15 Medical Virology (142) Flashcards
An unknown virus has been isolated in the laboratory from mouse epithelial cells, which contain reverse transcriptase. The genetic material from this virus is examined and found to contain adenine, guanine, cytosine, and uracil, but no thymine. What can be concluded about it?
1 It is a retrovirus
2 It is a DNA virus
3 It is a prion particle
4 It cannot undergo integration
5 It can only infect bacteria
It is a retrovirus
A retrovirus contains RNA as its genetic material, and uses the enzyme reverse transcriptase to convert its single stranded RNA genome into a DNA/RNA helix which is then converted to a DNA duplex. This then inserts into the host chromosome, is replicated, and eventually gives rise to single stranded RNA to be incorporated into the new viral particle. RNA and DNA have three bases in common (adenine, guanine, and cytosine) but RNA contains uracil and DNA contains thymine as the fourth base. Therefore, finding uracil in the viral genome indicates that it is an RNA containing virus. Since it contains reverse transcriptase, we can deduce that it is retrovirus.
Prion is a type of infectious agent that lacks nucleic acid, and is made up only of protein. Prion is a short form for proteinaceous infectious particle.
The process of incorporating the genetic material of a virus into the host genome is known as integration. Retroviruses can undergo integration. Bacteriophages (and not retroviruses) infect bacteria only.
A 28-year-old male presents to the office with bilateral cervical lymphadenopathy of 2 cm with mild fever and sore throat for 1 week. He also complains of nausea and decreased appetite. On examination, there is hepatosplenomegaly and palatal petechiae. A new intern diagnoses him with streptococcal throat infection and prescribes antibiotics. The patient comes back the next day with a painless, itchy rash all over his body. The antibiotic that was most likely given to this patient is
1 Benzathine penicillin
2 Erythromycin
3 Amoxicillin
4 Cephalexin
5 Clindamycin
Amoxicillin
The patient probably has infectious mononucleosis (IM), which was diagnosed wrongly and treated with Amoxicillin. Amoxicillin causes a non- allergic rash in patients having infectious mononucleosis. The underlying pathomechanisms are still unknown. The clinical decision to use antibiotics in acute pharyngitis is complicated by the identical presentation of both viral and bacterial illnesses. If empiric therapy is elected, the incidence of hypersensitivity reaction is less common with penicillin or tetracycline compared to ampicillin or its analog, amoxicillin.
Infectious mononucleosis, caused by Epstein-Barr virus (EBV), is a disorder that typically occurs in young adults and it is characterized by fever, sore throat, headache, malaise, nausea, and anorexia. Lymphadenopathy is usually present and splenomegaly may be observed. In the early phases of the infection, T lymphocytes become activated and they restrain viral replication in B-lymphocytes. The lymphocytosis characteristic of this period consists primarily of T lymphocytes with cytotoxic phenotype (CD8+). A humoral response is also present during acute IM and is characterized by non-EBV-specific response such as the production of Heterophil antibodies. Treatment is usually bed rest and steroids are indicated for impending or established airway obstruction.
The viral rash is faint, usually non-pruritic, and fades away rapidly. The drug-induced rash is pruritic and lasts for a longer duration than the typical viral rash seen in IM.
Benzathine penicillin interferes with synthesis of cell wall mucopeptides during active multiplication, which results in bactericidal activity. It is given for the prophylaxis of streptococcal throat infection. It does not cause a rash in IM.
Erythromycin inhibits bacterial growth, possibly by blocking dissociation of peptidyl tRNA from ribosomes, causing RNA-dependent protein synthesis to arrest. It is used in the treatment of Strep throat, but it does not cause a rash in IM.
Cephalexin is a first-generation cephalosporin that arrests bacterial growth by inhibiting bacterial cell wall synthesis. Primary activity is against skin flora and it is used for skin infections or prophylaxis in minor procedures. Orally, cephalosporins are effective in the treatment of streptococcal pharyngitis, but they do not cause a rash in IM.
Clindamycin is a lincosamide used for treatment of serious skin and soft tissue staphylococcal infections. It is also effective against aerobic and anaerobic streptococci (except enterococci). It inhibits bacterial growth, possibly by blocking dissociation of peptidyl tRNA from ribosomes, causing RNA-dependent protein synthesis to arrest. It does not cause a rash if given in IM.
Case
Over a period of 1 month, 42 persons from the local community, mostly adults, were seen in an ophthalmic clinic situated in one of the East Asian countries. Most of them had attended the clinic for other ocular problems a few days preceding the onset of symptoms.
The presenting symptoms were soreness and redness of eyes, photophobia, foreign body sensation, and excessive tearing. Some complained of ocular and periorbital pain and decreased visual acuity. Duration of the illness varied from 3-14 days. On examination, swelling and erythema of the eyelid, conjunctival hyperemia, chemosis, and follicular reaction mainly of the lower conjunctiva were seen in all patients. Superficial punctate keratitis and discrete sub-epithelial opacities were observed in those who complained of decreased visual acuity. An outbreak of keratoconjunctivitis (epidemic keratoconjunctivitis) in the community was suspected. Conjunctival swabs cultured on Hep2 cells showed cytopathic effect (CPE), characterized by marked rounding, enlargement, and aggregation of affected cells into grape-like clusters. Human adenovirus group antigen was detected in the infected tissue culture cells by immunofluorescence using antihexon antibody. Investigation of the source of infection revealed presence of adenovirus on the tonometer tip.
Certain types of adenoviruses are known to be commonly associated with particular disease manifestations.
Of the adenovirus types listed below which is most likely to be responsible for this outbreak of keratoconjunctivitis?
1 Type 37
2 Type 34
3 Type 40
4 Type 12
5 Type 7
Type 37
Type 37 is one of the 3 adenovirus types commonly associated with Epidemic Keratoconjunctivitis (EKC). The others are types 8 and 19 and all 3 types belong to subgroup D adenoviruses. Adenovirus type 8 was initially identified and considered as the most important causative agent of EKC. More recently, types 19 and 37 have been recognized as causative agents of this highly contagious disease. Type 37 is reported to have caused 3 large epidemics of EKC in northern Japan.
EKC is a serious disease as it involves both conjunctiva and cornea. In most cases, the infection remains self-limited. Acute phase involving viral replication lasts up to 2 weeks. Often the acute phase is followed by immune T-cell mediated infiltration of the corneal stroma leading to the formation of multiple sub epithelial infiltrates. These infiltrates can cause disturbances in vision, which may last for months. EKC outbreaks have been reported in eye clinics, hospitals, nursing homes, camps, and military bases. Major mode of transmission is through hands, ophthalmic instruments, and ophthalmic solutions.
Adenoviruses are extremely hardy when deposited on environmental surfaces. Adequate disinfection of ophthalmic instruments and hand hygiene are important in preventing transmission.
Adenoviruses are non-enveloped double stranded DNA viruses, 70-90 nm in size with a characteristic morphology. The viral capsid is composed of 252 capsomeres arranged as an icosahedron with 20 triangular facets and 12 vertices. The capsomeres consist of pentons and hexons. Pentons occur at the 12 vertices and the rest are hexon capsomeres. Penton consists of penton base and protrusion of fibers with a rod-like portion and a knob at the distal end. Thus the virion has the appearance of a space vehicle. Hexons, pentons, and fibers constitute the major antigens of adenoviruses. All human adenoviruses share a common hexon antigen and can be detected by complement fixation, immunofluorescence, or ELISA. Another group reactive antigen is present in penton base. The penton base carries toxin-like activity and causes cytopathogenic effect (CPE). The fibers contain type-specific antigens and are important in typing. The virus attaches to cells by the fibers. Hemagglutinating activity of adenoviruses depends on fibers.
Human adenoviruses are classified into 6 subgroups (subgenera) A-F based on their biologic, immunologic, and biochemical properties (hemagglutination, fiber length, DNA fragment analysis, and oncogenic potential). The groups differ in their ability to agglutinate rat and monkey RBCs and this property of hemagglutination is useful for identifying the subgroups.
Neutralization and hemagglutination inhibition tests are used for typing isolates. Different genome types also have been identified.
Adenoviral infection is species specific. Of the 51 human adenovirus types identified, more than one type may produce the same clinical syndrome and one type of virus may cause different diseases. The virus replicates only in cells of epithelial origin and shows the property of latency. In the infected cell the virus replicates in the nucleus and produces large intra nuclear inclusions.
Though cultural isolation and identification of the virus is important from epidemiological point of view, it is time consuming. Detection of adenoviral antigen in conjunctival cells by direct immunofluorescent assay (DFA) is rapid and found useful.
Molecular methods based on polymerase chain reaction (PCR) have been recently developed for the detection of adenovirus DNA in conjunctival swabs. A multiplex PCR-enzyme hybridization assay is reported to be of use for detecting all adenovirus species (A through F) simultaneously in a single test. This test is found to be rapid, specific, and sensitive.
For the diagnosis of adenoviral infections, detection of specific antibodies in the serum is helpful. Rise in titer of antibodies should be demonstrated in paired sera. Complement fixation or ELISA can be used for detecting antibodies against group antigen. Neutralization test detects type specific antibodies.
Type 34 and type 35 are associated with infections following transplantation and belong to group B adenoviruses. Patients may develop fatal disseminated infections especially following bone-marrow transplants. Post transplant adenovirus infections are more common in pediatric patients. Infection may be often endogenous caused by the reactivation of latent adenovirus or can be exogenous.
Type 40 and type 41 are known as enteric type adenoviruses. These viruses are associated with diarrhea occurring in infants and belong to group F adenovirus. Both these types are fastidious and fail to grow on conventional tissue cultures used for growing adenoviruses. The viruses are present in abundance in diarrheal stools and can be demonstrated by electron microscopy. Enzyme Immuno Assay (EIA) and latex agglutination (LA) commercial kits are available for detection of enteric adenoviruses in stools.
Type 12 belongs to group A adenoviruses and experimentally proved to be one of the most strongly oncogenic type. Inoculation of types 12, 18, and 31 into baby hamsters induces tumors. So far there is no evidence relating adenoviruses and natural malignancy in humans or animals.
Type 7 is a group B adenovirus commonly associated with several clinical syndromes. The diseases include pharyngitis, pharyngoconjunctival fever, acute respiratory disease (ARD), and pneumonia in infants and immunocompromised hosts. ARD outbreaks caused mostly by types 4 and 7 and occasionally by type 3 have been reported in military recruits. In the United States, a vaccine against types 4 and 7 was being used for military personnel for several years and was discontinued in 1990.
Adenovirus types 3 and 7 produce follicular conjunctivitis which is milder, usually occurring as a manifestation of pharyngoconjunctival fever. This is also known as swimming pool conjunctivitis. Outbreaks may occur, often associated with children’s summer camps. Similar ocular manifestations may be caused by Chlamydia trachomatis.
No licensed systemic or topical antiviral drug is available for treatment of adenoviral infections.
Case
A 45-year-old woman residing in US was seen at the medical clinic for sudden onset of fever, shivering, headache, bilateral conjunctivitis, retroorbital pain, and acute pain in her limbs and joints. She had traveled to India 4 weeks ago and returned 3 days ago after spending her vacation. She became ill soon after returning to the US. While she was in India, there was an ongoing epidemic of an arboviral infection in the country. The virus responsible for the epidemic belonged to genus Alphavirus (Togaviridae family) and was transmitted by Aedes aegypti mosquitoes.
After physical exam and routine laboratory investigations, clinical diagnosis was “viral fever”. The patient was placed on symptomatic treatment with analgesics and anti-inflammatory drugs. She became afebrile on the 7th day after onset of her illness and all symptoms except the joint pains resolved within 14 days. As the arthralgia persisted even after 2 months, she had to seek medical advice. Based on the possibility of travel-associated infection, serological tests were done. The test results came positive for specific IgM antibodies and neutralizing antibodies against the arbovirus that was causing the extensive epidemic in India.
What is the most likely viral agent that caused illness in this patient?
1 Sindbis virus
2 West Nile virus
3 Yellow fever virus
4 Chikungunya virus
5 Dengue virus
Chikungunya virus
Chikungunya virus is a mosquito-borne arbovirus and belongs to genus alphavirus of Togaviridae family. In Asian countries, the vector is Aedes aegypti mosquitoes. During 2005-2006, an epidemic of Chikungunya occurred in India and >1.4 million cases were reported in 2006. This epidemic was caused by an African genotype of the virus. In US, travel-associated chikungunya has been reported in returning travelers from India and SW Indian Ocean Islands where the outbreak originated. Though the symptoms of the patient are characteristic of Chikungunya, other viral fevers may clinically resemble this disease.
All other viruses listed are arboviruses transmitted by mosquitoes; they can be excluded due to the following reasons:
West Nile, Yellow fever, and Dengue viruses are not alphaviruses. They belong to genus flavivirus of Flaviviridae family. Sindbis is an alphavirus and has not been reported to have caused epidemics in India. The main vector for this species is Culex mosquitoes.
Alphaviruses are spherical viruses 70 nm in diameter with single-stranded positive-sense RNA genome. The neucleocapsid is wrapped inside a lipid layer upon which the envelope proteins are displayed. Envelope proteins mediate binding to host cells and the virus particles enter the cytoplasm of the host cell by endocytosis. Virus replication occurs in the cytoplasm. Viral assembly takes place at the host cell surface and the viruses acquire their envelope from the plasma membrane through budding. Most of the alphaviruses possess hemagglutinating ability.
Chikungunya virus causes endemic and epidemic infections indigenous to tropical Africa and Asia. The disease is characterized by acute onset of fever, arthralgia and sometimes arthritis. Related arthralgia and arthritis may persist for months. Conjunctivitis and maculopapular rash are other manifestations that may appear. In travelers returning from areas affected by an ongoing epidemic, Chikungunya infection is considered as a probable diagnosis if they develop these symptoms. An extensive epidemic has been reported from the Reunion Islands. Aedes albopectus was the vector. Imported cases have been reported from US. Indigenous transmission is possible as the vector mosquitoes belonging to Aedes species are present in the country. In the urban areas, the viral infection is maintained by a man-mosquito cycle. No animal reservoirs have been identified in the urban cycle. A sylvatic cycle similar to that of Yellow fever involving wild primates and forest dwelling Aedes species of mosquitoes has also been observed.
Vertical maternal-fetal transmission of the viral infection has been reported. Chikungunya viral genome was detected in the amniotic fluid, placenta, and brain tissue of the infected fetus.
Laboratory diagnosis depends on isolation of the virus in cell cultures, reverse-transcription polymerase chain reaction (RT-PCR) based assays for detection of the viral genome, and serological test for antibodies. Virus specific IgM can be demonstrated by enzyme-linked immunosorbent assay (IgM-capture ELISA) and neutralizing antibodies can be detected by plaque reduction test. For diagnosis during the first week of illness, PCR is more reliable than serology.
There is no specific treatment or vaccine available. Infection results in life-long immunity.
Sindbis virus is the prototype alphavirus. It causes Sindbis fever. Virus is maintained in nature by transmission between vertebrate hosts and mosquito vectors, mainly Culex mosquitoes. Sindbis fever is characterized by sudden onset of fever, myalgia, arthralgia, and rash. The disease is found in Asia, Africa, the Middle East, and Europe. Many species of birds and mammals have been identified as reservoir hosts. Experimental studies have shown that Sindbis virus has specific cytotoxicity for cancer cells. It causes necrosis of cervical tumors in mice. It is suggested that a specific strain of Sindbis virus (SIN AR339strain) could be a promising agent for human cervical and ovarian cancer therapy.
West Nile, Yellow fever, and Dengue viruses belong to the Flavivurus genus. Flaviviruses replicate in the cytoplasm of the host cell. The particle assembly takes place in intracellular vesicles. They are 40-60 nm in diameter and possess single-stranded positive sense RNA genome.
West Nile virus is transmitted by Culex species of mosquitoes. Generally birds are found as natural reservoirs. Infection may be subclinical or may cause acute mild febrile disease with lymphadenopathy and rash. The virus may cause fatal encephalitis in aged persons. An epidemic of West Nile virus infection with several cases of meningoencephalitis occurred in the US in 2002. Person to person transmission by organ transplantation, blood transfusion and breast feeding have also been reported.
Yellow fever virus is the prototype member of Flaviviridae family. Yellow fever is an acute febrile illness found only in Africa and Central and South Americas. In severe cases, liver and kidneys are affected and jaundice, proteinuria, and hemorrhagic manifestations are seen. Urban yellow fever is transmitted by Aedes aegypti mosquitoes. Jungle yellow fever is a disease of monkeys and the sylvatic cycle involving monkeys and wild mosquitoes maintain the virus in nature. 17D vaccine is a very effective, attenuated virus vaccine against yellow fever. It is the most effective preventive measure.
Dengue virus causes dengue fever. The virus is of worldwide distribution predominantly in tropical region. The disease is characterized by fever, myalgia, joint pains, lymphadenopathy, and rash. Dengue hemorrhagic fever and dengue shock syndrome are severe forms of the disease. Vector is primarily Aedes aegypti. Aedes albopectus is also known to transmit dengue. Epidemics have been reported from several countries including India.
Case
Within 48 hours of consumption of raw oysters from a restaurant in North Carolina, 3 men in their 30s developed diarrhea and severe vomiting accompanied by headache, low-grade fever, and chills. They recovered with administration of intravenous fluid. In a week’s time, all other adults and children in their households became sick with similar symptoms. Bacterial causes were excluded in the laboratory. A viral agent was considered as the cause of this outbreak of gastroenteritis.
What is a likely characteristic of this virus?
1 Enveloped virus, 70-80 nm size
2 Genome contains double-stranded RNA
3 Replicates in the nucleus of the host cell
4 Cultivable in vitro on HEp2 cells
5 Can survive temperature as high as 60°C
6 Only a single genotype has been identified
Can survive temperature as high as 60°C
The viral agent responsible for the outbreak of gastroenteritis is most likely to be a norovirus. Norovirus (a group of Norwalk-like viruses) is the cause of >90% of non-bacterial gastroenteritis in the U.S. and is the most important cause of viral gastroenteritis involving adults. Food-borne outbreaks are common. Uncooked or inadequately cooked shellfish is one of the important sources. Other viruses of gastroenteritis (Group A rotavirus, sapovirus, astrovirus, adenovirus types 40 and 41) are mostly associated with infections in children less than 5 years old. Norovirus can survive at temperatures as high as 60°C and up to 10ppm chlorine. The virus does not possess the other characteristics listed.
Norovirus genus belongs to the family Caliciviridae. The virus is non-enveloped, 27-40 nm in diameter, has a genome containing single-stranded RNA, replicates in the cytoplasm of the host cell, and is not cultivable. Genetic and antigenic diversity is an important characteristic of noroviruses. Genetic variability is likely to be responsible for repeated infections during a lifetime and high attack rates in all age groups during outbreaks. The prototype strain Norwalk virus caused an outbreak of gastroenteritis in a school in Norwalk, Ohio in 1968. Currently at least 4 norovirus genogroups (GI, GII, GIII, and GIV) have been identified, and these have been divided into at least 20 genetic clusters.
Transmission is by feco-oral route, through consumption of fecally contaminated water or food, or by direct person-to-person spread. Shellfish harvested from fecally contaminated waters pose a special risk, as they possess the capacity to concentrate viruses through filtration. Contaminated fomites can be a source of infection. Vomitus also contains the virus, and droplets resulting from aerosolization of vomitus can be infective. Noroviruses are highly contagious and as few as 10 viral particles are sufficient to produce infection. The infection is often self-limited; rehydration by intravenous fluids is required in severe cases.
A reverse-transcriptase polymerase chain reaction (RT-PCR) has been developed and is used by many state public health laboratories in the U.S. for detection of norovirus in stool and vomitus samples. The test can be used to detect norovirus in shellfish and water samples as well. Other detection assays for noroviruses include enzyme immunoassay (EIA), electron microscopy, and immune electromicroscopy (IEM). Enzyme-linked immunosorbent (ELISA) assays developed for detection of IgM antibodies are not widely used due to limitations in detecting immune responses to a variety of antigenic types.
A sexually active adolescent girl presented with fever, malaise, and painful vesiculo-ulcerative lesions of the genitalia of 3 days duration. Clinical diagnosis was suggestive of a viral infection. In the microbiology laboratory, material from the lesion was tested and found positive for a viral antigen by direct fluorescent antibody (DFA) test. This etiological viral agent is likely to possess what characteristic?
1 Grows only on human fibroblastic cells in vitro
2 Is an RNA virus with a long replication cycle of >48 hours
3 Remains latent in lymphoid tissues
4 Produces cytoplasmic inclusions in infected cells
5 Has glycoprotein G, an envelope protein that elicits type-specific antibodies
Has glycoprotein G, an envelope protein that elicits type-specific antibodies
The patient’s symptoms are suggestive of genital herpes, a widely prevalent sexually transmitted viral infection.
The major causative agent of genital herpes is Herpes simplex type 2 (HSV 2), accounting for 70-90% of primary genital herpes. Herpes simplex type 1 (HSV-1) also can cause genital herpes, though is mainly associated with oro-pharyngeal infections. Both types share a significant number of common antigens. An exception is Glycoprotein G, an envelope protein that elicits type-specific antibodies. Tests based on the recognition of antibodies to glycoprotein G antigens of HSV-1 (gG-1) and HSV-2 (gG-2) accurately distinguishes between HSV-1 and HSV-2 infections. Recurrence of genital herpes in HSV-2 infection is much more than in infection by HSV-1. High rates of HSV-2 infection are seen in HIV type-1 infected persons. Differentiation of the types and detection of HSV-2 infections is important in assessment of prognosis, management, and counseling of patients.
Other features listed are not characteristics of Herpes simplex virus.
Herpes simplex is a DNA virus, with the virus having a short replication cycle requiring only 8-16 hours for completion. Though human diploid fibroblasts are often preferred for growing the virus, it can grow in a variety of tissue culture cells and also on chorioallantoic membrane of chick embryo. The virus produces intranuclear eosinophilic inclusions in the infected cells, and the site of latency is a sensory ganglion.
In primary genital herpes, appearance of vesiculo-ulcerative lesions is often associated with systemic symptoms. Virus remains latent in sacral ganglia and leads to recurrent infections, mostly in HSV-2 infections. Asymptomatic infections are common. Both symptomatic and asymptomic infections serve as reservoirs of the virus.
Genital herpes during pregnancy presents great risk of transmitting infection to the newborn, resulting in neonatal herpes. HSV2 infection is known to enhance HIV susceptibility and subsequent sexual transmission because of the break in mucosal surface caused by the ulcerative lesions. Progressive disease and severe extensive lesions are seen in immunocompromised individuals.
Laboratory diagnosis of genital herpes is mainly based on virological tests and type-specific serological assays.
Virological tests include detection of viral antigen by direct fluorescent antibody test (DFA), viral culture, and Polymerase chain reaction (PCR) assay for detection and identification of the virus type. DFA does not identify HSV type and is less sensitive. PCR and culture yield positive results only during phases of active infection. Culture, though highly specific, is less sensitive. PCR is not widely available for use.
Type-specific serology using glycoprotein G antigens (gG-1 and gG-2) is recommended for confirming or establishing clinical diagnosis in symptomatic patients with negative culture and antigen testing and those with atypical presentations. The assays are used also for screening of high-risk populations. Enzyme Linked Immunosorbent Assay (ELISA), immunoblot tests, and a rapid membrane-based immunoassay for HSV-2 are available for detection of type-specific antibodies.
Acyclovir, famciclovir, and valacyclovir are drugs used for treatment of genital herpes. They reduce subclinical viral shedding and decrease frequency and severity of recurrent outbreaks.
A 6-year-old girl presents with severe diarrhea and abdominal pain. A stool sample is analyzed by RT-PCR for RNA-dependent RNA polymerase and the result is negative. What is most likely responsible for this child’s symptoms?
1 Rotavirus
2 Influenza A virus
3 Poliovirus
4 B19V
5 Adenovirus
Adenovirus
The syndrome and PCR findings are most consistent with adenovirus infection. Adenovirus is a very common cause of diarrhea and vomiting in children. Since it is a DNA virus, it does not encode an RNA-dependent RNA polymerase.
Although rotavirus is the most common cause of diarrhea and vomiting in children, it is a dsRNA virus and it does encode RNA-dependent RNA polymerase.
Influenza A is mainly a respiratory disease. Although it can be associated with abdominal discomfort in children, it not typically associated with predominantly gastrointestinal symptoms.
Poliovirus, the etiological agent of polio, causes flu-like symptoms that can progress to paralysis; its main manifestations are not diarrhea and vomiting.
Parvovirus B19 is a DNA virus; it does not encode RNA-dependent RNA polymerase. Additionally, it causes erythema infectiosum (“slapped cheek” syndrome) and sometimes aplastic anemia rather than diarrhea and vomiting.
You are studying a virus isolated in the laboratory from mouse epithelial cells. The genetic material from this virus is examined and found to contain adenine, guanine, cytosine, and uracil, but no thymine. You begin to study the mechanism of replication of this virus. Based on the fact that the genetic material of this virus contains uracil, what is the enzyme unique to these types of viruses that helps form double-stranded DNA?
1 Guanylate cyclase
2 Integrase
3 Reverse transcriptase
4 Topoisomerase
5 DNA ligase
Reverse transcriptase
The correct answer is reverse transcriptase because of the fact that it contains uracil, which indicates that it is an RNA virus. A double-stranded DNA virus is formed from an RNA virus by reverse transcriptase. A retrovirus is an infectious particle consisting of an RNA genome packaged in a protein capsid surrounded by a lipid envelope. This lipid envelope contains polypeptide chains, including receptor-binding proteins that link to the membrane receptors of the host cell, initiating the process of infection. In order to replicate, its genetic material (RNA) must first be converted to a DNA molecule by the enzyme reverse transcriptase. This enzyme, which is found in the virus particle, is a DNA polymerase that uses an RNA molecule as a template to synthesize DNA, resulting in an RNA/DNA double helix.
Further enzyme action leads to the synthesis of a DNA double helix using the RNA/DNA template. This DNA helix can then integrate into the host chromosome and be transcribed into RNA molecules coding for capsid proteins, envelope proteins, and the reverse transcriptase. This integration into the host DNA is carried out by the viral integrase. Integration into the host chromosome is required for the synthesis of new viral RNA molecules. A host cell RNA polymerase is responsible for this transcription. Many new virus particles are then assembled containing the RNA molecule and the enzyme reverse transcriptase.
Guanylate cyclase is an enzyme unrelated to transcription and translation. It is involved in the conversion of guanosine triphosphate (GTP) to cyclic guanosine monophosphate.
Topoisomerases are involved in unwinding the DNA to allow transcription and replication to occur. The DNA topology is adjusted by making temporary cuts in the DNA to allow unwinding.
DNA ligase helps bond DNA-strands, which have a double-strand break. It plays a significant role in DNA replication and repair.
Ribosomes are usually absent in viruses, with the exception of
1 Arenavirus
2 Retrovirus
3 Herpesvirus
4 Togavirus
5 Adenovirus
Arenavirus
Arenavirus posses a few nonfunctional ribosomes. Ribosomes are absent in retrovirus, herpesvirus, togavirus and adenovirus.
Viruses that are made up of lipoprotein envelope are generally
1 Less stable
2 More stable
3 Pathogenic
4 Viroids
5 Pseudoviruses
Less stable
Viruses that are made of lipoprotein envelope are generally less stable being more sensitive to heat, detergents, and lipid solvents such as alcohol and ether. They are not more stable or pathogenic. Viroids are atypical virus-like particles that are made up solely of single molecules of circular RNA without a protein coat. Pseudoviruses contain host cell DNA instead of viral DNA in the capsid.
The viral envelope is composed of
1 Lipoprotein
2 Peptidoglycan
3 Lipopolysaccharide
4 Teichoic acid
5 Nucleoid
Lipoprotein
The viral envelope is composed of lipoprotein which is composed of lipid derived from the host cell membrane and protein that is virus-specific. Peptidoglycan is found in bacterial cell wall and is composed of peptides and sugars. Lipopolysaccharides are found in the outer cell wall of gram negative bacteria. Teichoic acids are polymers of glycerol phosphate or ribitol phosphate located in the outer layer of gram positive cell wall. Nucleoid is an area of cytoplasm where DNA is located.
Which one of the following statements best describes prions?
1 They are infectious particles composed solely of proteins
2 They are composed of viral nucleic acids but cannot replicate without a helper virus
3 They contain host cell DNA instead of viral DNA within the capsid
4 They consist solely of a single molecule of circular RNA without a protein coat or envelope
5 They are protein particles that generate a strong immune response
They are infectious particles composed solely of proteins
Prions are infectious particles composed solely of proteins. They are not composed of viral nucleic acids and do not need a helper virus to replicate. They do not contain host cell DNA instead of viral DNA within the capsid; they do not consist solely of a single molecule of circular RNA without a protein coat or envelope; and they are not protein particles that generate a strong immune response.
During the lysogenic cycle, the viral DNA is located in the
1 Host cell chromosome
2 Extrachromosomal element
3 Plasmid
4 Host cell wall
5 Host cell endoplasmic reticulum
Host cell chromosome
During the lysogenic cycle, the viral DNA is located in the host cell chromosome and not in extrachromosomal element, plasmid, host cell wall, or host cell endoplasmic reticulum.
Lysogenic phase of viral growth cycle occurs if the gene product that is encoded by the cI gene predominates. This gene encodes for a
1 Repressor
2 Antagonizer of repressor
3 Reverse transcriptase
4 RNA polymerase
5 DNA polymerase
Repressor
The cI gene product encodes for a repressor, which turns off transcription of early genes so that lysogenic phase can ensue. Transcription is inhibited by binding of the repressor to two operator sites that control early protein synthesis. If the product of the cro gene that encodes for the antagonizer of the repressor predominates, it prevents synthesis of sufficient repressor and replication and lysis of the cell results.
Repressor can also prevent replication of additional lambda phages that infect subsequently. This is called immunity and is specifically directed against lambda phage, because the repressor binds only to the operator sites in lambda DNA and other phages are not affected.
Which of the following accurately describes the correct sequence of steps in viral infection and replication?
1 Uncoating, attachment, biosynthesis, penetration
2 Attachment, uncoating, penetration, biosynthesis
3 Attachment, penetration, uncoating, biosynthesis
4 Uncoating, attachment, penetration, biosynthesis
5 Uncoating, penetration, attachment, biosynthesis
Attachment, penetration, uncoating, biosynthesis
The first step requires a compatible union between sites on the virus and target cell, and likely involves electrostatic interactions. The surface site on the virus may be a spike or fiber of a specific protein. The receptor site on the target cell most typically is a glycoprotein, and may be shared by related members of the same virus group.
Penetration of the cell can occur via four mechanisms. Some viruses may be phagocytized. Alternatively, the viral lipoprotein of the envelope may fuse with the cell membrane. Thirdly, the virus may interact with cell membrane receptor sites, a process in which host cell enzymes start uncoating at the cell membrane, resulting in the nucleic acid (and occasionally its associated polymerase) escaping into the cell. Finally, direct penetration of the intact virus through the cell membrane into the cytoplasm occurs in some viruses.
Prior to replication, the viral genome must be extricated from all of the surrounding material. The destruction or disassembly of the capsid may commence while the virion is adsorbing to and penetrating through the cell. For some enveloped viruses, elimination of this coating occurs at the surface of the cells.
The location of viral synthesis is variable with the nature of the genome (DNA or RNA) and the family or group to which the virus belongs. The DNA of deoxyriboviruses is synthesized in the nucleus of the infected cell, while the protein components are translated in the cytoplasm. The poxviruses represent the exception, as all macromolecular synthesis occurs cytoplasmically. Similar to the poxviruses, the viral components of most of the riboviruses are synthesized in the cytoplasm. But here, too, there are exceptions: nuclear synthesis of some viral macromolecules occurs in the orthomyxoviridae (the group including influenza) and some of the paramyxoviridae and retroviridae.
Varicella is transmitted primarily by
1 Respiratory droplets
2 Sexual contact
3 Body fluids
4 Arthropods
5 Direct skin contact
Respiratory droplets
Varicella is caused by varicella-zoster virus and is transmitted primarily by respiratory droplets. The initial infection is in the respiratory tract. It spreads via the blood to the internal organs, such as liver, and then to the skin.
Infectious mononucleosis can be caused by what?
1 Herpes virus
2 Epstein Barr virus
3 Cytomegalo virus
4 Rickettsiae
5 Adeno virus
Epstein Barr virus
The Epstein Barr virus causes infectious mononucleosis associated with the Burkitts lymphoma in East African children. The virus is found in human oropharynx and B lymphocytes. It is transmitted primarily by saliva. The infection begins in the pharyngeal epithelium, spreads to the cervical lymph nodes, then travels through the blood to the liver and spleen.
For which of the following viruses is assay by viral enzymes particularly useful?
1 Influenza
2 Parainfluenza
3 Mumps virus
4 Hepatitis B virus
5 Retroviridae
Hepatitis B virus
No suitable cell culture system is currently available for the hepatitis B virus. Fortunately, the hepatitis B virus produces a DNA-dependent polymerase that is virus specific. Influenza A, influenza B, mumps virus, and parainfluenza virus may be cultured in primary monkey kidney cells. Influenza A, B, and C all may be cultured in eggs. Influenza A and B may be detected by hemadsorption, cytopathic effect, and hemagglutination; Influenza C may be detected by hemagglutination. Retroviridae may be cultured in T lymphocytes with methods of detection of transformation, reverse transcriptase, cytopathic effect, or immunofluorescence.
Which of the following methods is the most precise, universally useful technique for enumerating infective virus particles?
1 Pock assay
2 Plaque or Focal Assay
3 Electron microscopy Hemagglutination
4 Quantal Assay
Plaque or Focal Assay
The keys to this question are the terms “universally useful” and “infective.” Some of the described methods lead to the counting of both viable and nonviable particles, as described below.
Electron microscopy is useful for enumerating purified virus particles present at high density. The addition of a known number of latex particles to the suspension, followed by the calculation of the ratio of those particles to viral particles, provides an accurate count. Of course, this technique has the disadvantage that viable and nonviable particles cannot be differentiated. Equally important, very few diagnostic laboratories, and indeed not all research laboratories, have ready access to an electron microscope.
The plaque assay is the most precise measure of infectivity. The basis of this technique is the formation of clear zones, plaques or foci, in a monolayer of host cells. Serial dilutions of the virus are added to a monolayer of cells known to be infected by the cells (for example, MDCK cells are used for influenza). Most commonly after the virus has been allowed to adsorb onto the cells, an agar overlay is added to prevent dispersion of the virus. This ensures that each plaque represents only a single initial virus particle. For viruses which only infect contiguous cells without releasing virions into the surrounding medium, the agar may be replaced by a liquid.
Certainly not applicable for all viruses, the pock assay involves the counting of localized lesions (pocks) that form on the chorioallantoic membrane (CAM) of the embryonated egg upon addition of known dilutions of the virus. As in the plaque assay, each lesion represents a single original virus particle.
Instead of providing a quantitative measure of viral infectivity, quantal assays provide only a “yes or no” result. In quantal assays, each viral replication cycle results in an amplification of the effects of each individual virus particle. The virus is serially diluted, and appropriate cells are incubated with a known volume of each dilution. The endpoint for these assays may be negative effects, including morbidity in animals and development of lesions on either the chorioallantoic membrane or on the embryo of eggs. Following the incubation period, each target animal, or sample, is examined for a +/- response.
Which one of the following is the largest virus?
1 Poxvirus
2 Parvovirus
3 Hepadnavirus
4 Papovavirus
5 Adenovirus
Poxvirus
The largest known virus is the poxvirus that has a particle size of 250x400nm. The parvovirus particle size is 22nm, hepadnavirus is 42nm, papovavirus is 55nm, and adenovirus is 75nm.
Inoculation of lymphocytic choriomeningitis virus into the brain of an immunosuppressed adult mouse results in
1 Disease followed by shorter life span
2 Disease followed by complete recovery
3 Disease followed by carrier status
4 Death
5 No effect
No effect
Inoculation of lymphocytic choriomeningitis virus into the brain of immunosuppressed adult mice has no effect. However, inoculation into the brain of a normal mouse results in death due to immune attack by cytotoxic T cells on the viral antigens in the cell membranes, rather than by virus-induced inhibition of cell functions. It does not cause disease followed by either a shorter life span, complete recovery, carrier status, or death.
Which one of the following is an example of a chronic carrier infection?
1 Hepatitis B
2 Neonatal rubella virus
3 Cytomegalovirus
4 Retrovirus
5 Togavirus
Hepatitis B
Hepatitis B is an example of a chronic carrier infection where a carrier state can follow an asymptomatic infection, as well as actual disease. Neonatal rubella virus, cytomegalovirus, retrovirus, and togavirus do not cause chronic carrier infection.
Which one of the following drugs inhibits viral protein synthesis?
1 Methisazone
2 Azidothymidine
3 Dideoxyadenosine
4 Foscarnet
5 Acyclovir
Methisazone
Methisazone inhibits viral protein synthesis of poxviruses such as small pox and vaccinia virus. Azidothymidine is an inhibitor of retrovirus growth and inhibits chain termination during DNA synthesis. Dideoxyadenosine is a nucleoside analogue that causes chain termination during DNA synthesis. Foscarnet is a pyrophosphate analogue that inhibits the DNA polymerase of all herpes viruses and reverse transcriptase of HIV. Acyclovir (Zovirax) is a nucleoside analogue with a 3-carbon analogue in place of the normal sugar ribose.
Herpes virus can be detected by the Tzanck smear of the skin lesion. This test stains for the presence of which one of the following?
1 Multinucleated giant cells
2 Inclusion bodies
3 Dead cells
4 Herpes DNA
5 Herpes cell envelope
Multinucleated giant cells
The Tzanck smear stains for the presence of multinucleated giant cells that are formed as a result of fusion of cell membranes due to insertion of viral proteins into the membrane. Tzanck smear does not detect the presence of inclusion bodies, dead cells, herpes DNA, or cell envelope.
Which one of the following viruses causes gingivostomatitis?
1 Herpes simplex virus-1
2 Herpes simplex virus-2
3 Varicella zoster virus
4 Epstein Barr virus
5 Cytomegalovirus
Herpes simplex virus-1
Herpes simplex virus-1 causes gingivostomatitis. Herpes simplex virus-2 causes herpes of the genitals, varicella zoster causes varicella, Epstein-Barr virus causes infectious mononucleosis, and cytomegalovirus causes congenital infections.
Which of the following statements best describes the relationship between varicella and zoster?
1 Varicella is the primary disease, and zoster is the recurrent form
2 Zoster is the primary disease, and varicella is the secondary disease
3 Varicella and zoster are the same disease
4 Varicella and zoster occur at the same time in an individual
5 Varicella and zoster are unrelated
Varicella is the primary disease, and zoster is the recurrent form
Varicella and zoster are caused by the varicella zoster virus. Varicella is the primary disease, and zoster is the recurrent form of the disease that occurs in immunocompromised adults. Zoster is not the primary disease and varicella the secondary disease; they are not the same disease, and they are related because they are caused by the same virus.
How is the recombination of RNA segments from 2 different influenza virus strains described?
1 Antigenic shift
2 Antigenic drift
3 Peptidoglycan
4 Teichoic acids
5 Prions
Antigenic shift
Antigenic shift and antigenic drift can be found in the influenza virus. Antigenic shift is a process by which 2 or more different types of influenza A combine to form a virus radically different from the ancestor strains. Antigenic shift occurs in 2 ways.
1. Antigenic shift can occur through genetic recombination, or reassortment, when 2 or more different influenza A viruses infect the same host cell and combine their genetic material.
2. Qn influenza A virus can jump from 1 type of organism, usually a bird, to another type of organism, such as a human, without undergoing major genetic change.
A point mutation that leads to an amino acid change and altered antigenic sites so that the virus is no longer recognized by the host immune system is called antigenic drift. Peptidoglycan and teichoic acids are components of the bacterial cell wall and prions are infectious protein particles.
Paramyxoviruses possess hemagglutinin and neuraminidase that are present on the
1 Same spike
2 Different spikes
3 Nucleus
4 Golgi bodies
5 Endoplasmic reticulum
Same spike
Paramyxoviruses possess hemagglutinin and neuraminidase that are present on the same spike. This is in contrast to the orthomyxoviruses that possess hemagglutinin and neuraminidase on different spikes.
Rubella virus is a member of the family of:
1 Togavirus
2 Herpes virus
3 Neisseriae
4 Adenovirus
5 Picornavirus
Togavirus
Rubella virus is a member of the togavirus family and not the herpes virus, neisseriae, adenovirus, and picornavirus.
Which one of the following is a test for detection of cell-bound or incomplete antibodies?
1 Antiglobulin test
2 Gram stain
3 Enzyme linked immunoassay
4 Radioimmunoassay
5 Gel diffusion test
Antiglobulin test
Antiglobulin or Coombs test is used for the detection of cell-bound or incomplete antibodies that by themselves are incapable of agglutinating particles, but can bind to them firmly. By adding antibodies against globulin species, agglutination of the coated particles results. This test has the greatest application in the detection of various red blood cell antibodies in hemolytic anemias. Gram stain is used for the detection of bacteria. Enzyme linked immunoassay, radioimmunoassay, and gel diffusion tests are not used for the detection of cell-bound or incomplete antibodies.
Which of the following pairs of viruses are most closely related?
1 Poliovirus and Orbivirus
2 Enteroviruses and Rotavirus
3 Rotavirus and Echoviruses
4 Enteroviruses and Rhinoviruses
5 Rhinoviruses and Orbivirus
Enteroviruses and Rhinoviruses
Both the Enterovirus group, which includes the Poliovirus, Coxsackieviruses, and Echoviruses, and the Reoviridae, which includes the Reovirus, Orbivirus, and Rotavirus, have an RNA genome. The genomes of the former group are linear and single-stranded, whereas those of the later are double stranded and may be either linear or segmented.
The Picornaviridae family of viruses contains the Enterovirus and the Rhinoviruses, which have numerous properties in common. Viruses of this family lack an envelope and are icosahedral with a diameter of 20nm. The genome is a single-strand RNA. The Enteroviruses are stable to acid, while the Rhinoviruses are sensitive.
Which of the following are structurally most closely related to the influenza virus?
1 Retroviridae
2 Togaviridae
3 Paramyxoviruses
4 Coronaviridae
5 Rhabdoviridae
Paramyxoviruses
Each of these viral families or groups has an RNA genome and envelope. The Paramyxoviruses are structurally the most closely related to influenza, since both are negative sense RNA viruses and many of the paramyxoviruses contain a neuraminidase and hemagglutinin. There are some notable differences, however. In the paramyxoviruses, both neuraminidase and hemagglutinin functions contained in a single glycoprotein on one type of spike, whereas in influenza, these functions are accomplished by two separate glycoproteins which on two types of spikes (except for Influenza C, which has both functions on a single glycoprotein). In addition, the genome is segmented in influenza, but not in the paramyxoviruses. The viruses in the
Togaviridae and Coronaviridae families differ from the Influenza viruses in that they have a positive sense RNA genome. Viruses in the Rhabdoviridae family, which includes the vesicular stomatitis virus and the rabies virus, are bacilliform negative-stranded RNA viruses.
These enveloped, pleomorphic, and ss-RNA viruses cause respiratory infections by droplet nuclei or contact transmission. These belong to the orthomyxovirus group and are called what?
1 Lentiviruses
2 Influenza virus
3 Parainfluenza virus
4 Respiratory syncytial virus
Influenza virus
The influenza virus is a member of the orthomyxovirus group and is an enveloped ss-RNA virus. Lentiviruses are a group of retroviruses which include HIV-1. Parainfluenza virus and respiratory syncytial virus (RSV) belong to the paramyxovirus group.
This large-enveloped ds-DNA virus is associated with 70% of the initial genital infections by this virus group. Clinically, these infections present with small erythematous papules which progress to open ulcerations. Infections can become latent and recurrent. Which virus is this?
1 HSV-1
2 HSV-2
3 HIV-1
4 HIV-2
HSV-2
Herpes simplex type 1 and 2 (HSV-1, HSV-2) are both large-enveloped DNA viruses which cause latent and recurrent infections. However, HSV-1 is primarily associated with infections of the pharynx, skin, and central nervous system. On the other hand, HSV-2 is primarily associated with genital infections, representing approximately 70% of all such initial infections. HSV-2 infections recur more often as well.
Human immunodeficiency virus type 1 and 2 (HIV-1 and HIV-2) are retroviruses with plus-strand RNA genomes. Both of these can be passed by sexual contact and result in long-term infection of multiple cells and tissues. Both can also give rise to acquired immune deficiency syndrome or AIDS, however HIV-1 is associated with a long-term infection which has been virtually 99% fatal after 10-15 years. Recent research has illustrated that a small number of individuals may be infected with somewhat less virulent strains and these individuals do not follow the normal time-course to AIDS. HIV-2 is associated with a far less virulent infection and may include a much larger percentage of “none-progressing” individuals as well.
Viruses are
1 Free living saprophytes
2 Obligate intracellular parasites
3 Composed of DNA, as well as RN
4 Smallest free living cells
5 Capable of making their own proteins
Obligate intracellular parasites
Viruses are the smallest organism known and are not free living cells, but are obligate intracellular parasites. They were called filterable agents as they can pass through the filters designed to retain bacteria. Viral genome is made up of either DNA or RNA, but not both.
The viral genome is packaged into a protein coat called capsid. Capsid together with nucleic acid is called nucleocapsid. Nucleocapsid can be surrounded by a lipid called envelope. Viruses can not make their own protein or energy. Viruses require host cell biochemical machinery for energy and to make proteins. Viruses do not reproduce by binary fission or division. Viral reproduction occurs by self-assembly of individual components.
Which of the following is the correct sequence of viral replication?
1 Attachment, uncoating, penetration, protein synthesis, assembly, and release
2 Attachment, penetration, uncoating, protein synthesis, assembly, and release
3 Uncoating, attachment, penetration, protein synthesis, assembly, and release
4 Penetration, attachment, protein synthesis, uncoating, assembly, and release
5 Penetration, uncoating, attachment, protein synthesis, assembly, and release
Attachment, penetration, uncoating, protein synthesis, assembly, and release
Viral replication takes place in several stages. Once the virus recognizes the target cell, it binds to the cell. The viral attachment protein present on the surface of virion interacts with the cell receptor. Following attachment the virus can penetrate the cell by process of endocytosis or fusion. In the step of uncoating the capsid the envelope is removed and viral nucleic acid is released inside the host cell, so the viral genes become available for transcription.
In the protein synthesis step the process differs according to type of virus and the structure of genome. RNA virus mostly replicates in the cytoplasm. Plus-strand RNA viruses initiate protein synthesis. Minus-strand RNA virus, double-stranded RNA viruses, and DNA viruses initiate nucleic acid synthesis. Protein synthesis in DNA virus replication is divided into early phase and late phase. Once the replication is over the newly synthesized viral protein and nucleic acid is assembled inside the cells. The capsomers are self assembled into capsid. In enveloped virus the viral envelope is added from the cell membrane and becomes associated with nucleocapsid. The newly assembled virus is released from the cell by budding or cell lysis.
Which of the following RNA viruses replicate in the nucleus rather than in the cytoplasm?
1 Retroviruses
2 Picornaviruses
3 Togaviruses
4 Reoviruses
5 Arenaviruses
Retroviruses
Viral replication of majority of RNA viruses takes place in the cytoplasm. Retroviruses have a nuclear phase for their replication via a DNA intermediate. These viruses carry 2 copies of genome, 2 tRNA molecule, and an enzyme reverse transcriptase. Diploid genome has an inverted dimer of plus sense ssRNA. Reverse transcriptase uses tRNA molecule to make DNA copy. The viral DNA circularizes and integrates into the host genome. This integrated DNA is used as template for transcription of viral RNA.
Which of the following viruses is the smallest virus?
1 Poxviruses
2 Reoviruses
3 Parvoviruses
4 Picornaviruses
5 Papovaviruses
Parvoviruses
Poxviruses are the largest viruses in the category and parvoviruses are the smallest. Parvoviruses measure about 18 to 26 nm in diameter and contains single stranded linear DNA genome. Parvoviruses replicate in the nucleus of the cell. Parvoviruses do not contain envelope and have icosahedral symmetry.
B19 is a parvovirus which is member of genus Erythrovirus and is associated with erythema infectiosum, a human disease. This virus requires mitotically active cells for growth, such as fresh human bone marrow cells, embryonic cells, and erythroid leukemia cells.
The only double-stranded RNA viruses belongs to the family
1 Picornaviridae
2 Retroviridae
3 Arenaviridae
4 Togaviridae
5 Reoviridae
Reoviridae
Most of the families of RNA viruses infecting human consists of single strand of RNA, except the family Reoviridae. The virions in Reoviridae family consists of double stranded RNA, made up of 10-12 segments that separates them from other RNA viruses. Reoviruses are naked with icosahedral symmetry. Reoviruses replicate in the cytoplasm and are released by cell lysis. Reoviridae family comprises of genus:
Orthoreovirus.
Orbivirus.
Rotavirus.
Orthoreovirus is associated with mild upper respiratory disease, gastrointestinal infection, and biliary atresia. Orbivirus causes febrile illness accompanied by headache and myalgia. Orbivirus is the etiological agent of Colorado tick fever that is transmitted by the wood tick. Rotaviruses are implicated in epidemic diarrhea in young children.
Human T-cell lymphotropic viruses are
1 Single stranded DNA with naked icosahedral nucleocapsid
2 Linear double stranded DNA with naked icosahedral nucleocapsid
3 Double stranded circular DNA with naked icosahedral nucleocapsid
4 Double stranded linear DNA with enveloped complex nucleocapsid
5 Double stranded linear DNA with enveloped icosahedral nucleocapsid
6 Double stranded RNA with naked icosahedral nucleocapsid
7 Single stranded linear RNA with naked icosahedral nucleocapsid
8 Single stranded linear RNA with enveloped icosahedral nucleocapsid
9 Single stranded RNA with reverse transcriptase and diploid genome
10 Single stranded circular RNA with 3 segments and enveloped helical nucleocapsid
Single stranded RNA with reverse transcriptase and diploid genome
Human T-cell lymphotropic viruses belong to the family Retroviridae and are characterized by the presence of diploid genome. The virions of this family are enveloped with the genome, consisting of 2 plus stranded RNA and an enzyme reverse transcriptase. The virions replicate in the nucleus. Viral reverse transcriptase transcribes the double stranded DNA copy of the viral genome. The DNA is circularized and integrated into the host cellular DNA. This integrated DNA is used as a template for transcription of viral RNA.
Papillomavirus are naked icosahedral viruses, which are part of the family Papovaviridae. The genome of the virion consists of a cyclic double stranded DNA molecule. The virions have infectious genome that is replicated in the nucleus. Human papillomaviruses are implicated in warts, cervical cancer, and skin cancer.
Sandfly fever viruses are transmitted by Phlebotomus and can cause infections in humans and sheep. These viruses are a member of the family Bunyaviridae and are arboviruses (those that have wild animal reservoir hosts). The virions are enveloped with helical nucleocapsid. The genome is made up of 3 tubular nucleocapsids, with 3 segments of minus sense single stranded RNA. The virions replicate in the cytoplasm and bud from Golgi membranes of the host.
Parvoviruses are the smallest of viruses, measuring approximately 18 to 26nm in diameter. Parvoviruses are non-enveloped virions with icosahedral nucleocapsid. The genome consists of a single stranded linear DNA genome. Parvoviruses replicate in the nucleus of the cell. B19 is a parvovirus that is associated with erythema infectiosum, a human disease.
Rotaviruses are RNA viruses and are members of the family Reoviridae. Most of the RNA viruses consist of single stranded RNA in their genome. However, the virions of the family Reoviridae consist of linear double stranded RNA, with 10-11 segments. Rotaviruses are naked with icosahedral symmetry. Rotaviruses replicate in the cytoplasm and are released by cell lysis. Rotaviruses are associated with diarrhea in humans.
Rubella virus is the only non-arthropod-borne togavirus, which is an important human pathogen. The virions are enveloped and have icosahedral nucleocapsid. The genome consists of a linear, single stranded RNA that is non-segmented. Viral replication takes place in the cytoplasm and is released by budding from the cell membrane.
Adenoviruses are member of the family Adenoviridae and are implicated in infections of the eye, the respiratory tract, and the intestinal tract. The virions lack envelope and consist of icosahedral nucleocapsid. The genome consists of linear, double stranded DNA.
Smallpox virus is the DNA virus that is part of the family Poxviridae. The poxviruses are the largest and contain enveloped, complex nucleocapsid. The virions are made up of an inner core, which consists of a double stranded, linear DNA molecule.
Enteroviruses include polioviruses, human echoviruses, and coxsackieviruses. Enteroviruses are a member of the family Picornaviridae and are small, naked viruses with icosahedral nucleocapsid. The virions contain a single stranded, non-segmented linear RNA molecule and replicate in the cytoplasm.
Herpes simplex virus is a DNA virus from the family Herpesviridae. The virus is enveloped with icosahedral nucleocapsid. The genome contains double stranded, linear DNA. The virions replicate in the nucleus, bud through the nuclear membrane, and acquire the envelope.
Papillomavirus are:
1 Single stranded DNA with naked icosahedral nucleocapsid.
2 Linear double stranded DNA with naked icosahedral nucleocapsid.
3 Double stranded circular DNA with naked icosahedral nucleocapsid.
4 Double stranded linear DNA with enveloped complex nucleocapsid.
5 Double stranded linear DNA with enveloped icosahedral nucleocapsid.
6 Double stranded RNA with naked icosahedral nucleocapsid.
7 Single stranded linear RNA with naked icosahedral nucleocapsid.
8 Single stranded linear RNA with enveloped icosahedral nucleocapsid.
9 Single stranded RNA with reverse transcriptase and diploid genome.
10 Single stranded circular RNA with 3 segments and enveloped helical nucleocapsid.
Double stranded circular DNA with naked icosahedral nucleocapsid.
Human T-cell lymphotropic viruses belong to the family Retroviridae and are characterized by the presence of diploid genome. The virions of this family are enveloped with the genome, consisting of 2 plus stranded RNA and an enzyme reverse transcriptase. The virions replicate in the nucleus. Viral reverse transcriptase transcribes the double stranded DNA copy of the viral genome. The DNA is circularized and integrated into the host cellular DNA. This integrated DNA is used as a template for transcription of viral RNA.
Papillomavirus are naked icosahedral viruses, which are part of the family Papovaviridae. The genome of the virion consists of a cyclic double stranded DNA molecule. The virions have infectious genome that is replicated in the nucleus. Human papillomaviruses are implicated in warts, cervical cancer, and skin cancer.
Sandfly fever viruses are transmitted by Phlebotomus and can cause infections in humans and sheep. These viruses are a member of the family Bunyaviridae and are arboviruses (those that have wild animal reservoir hosts). The virions are enveloped with helical nucleocapsid. The genome is made up of 3 tubular nucleocapsids, with 3 segments of minus sense single stranded RNA. The virions replicate in the cytoplasm and bud from Golgi membranes of the host.
Parvoviruses are the smallest of viruses, measuring approximately 18 to 26nm in diameter. Parvoviruses are non-enveloped virions with icosahedral nucleocapsid. The genome consists of a single stranded linear DNA genome. Parvoviruses replicate in the nucleus of the cell. B19 is a parvovirus that is associated with erythema infectiosum, a human disease.
Rotaviruses are RNA viruses and are members of the family Reoviridae. Most of the RNA viruses consist of single stranded RNA in their genome. However, the virions of the family Reoviridae consist of linear double stranded RNA, with 10-11 segments. Rotaviruses are naked with icosahedral symmetry. Rotaviruses replicate in the cytoplasm and are released by cell lysis. Rotaviruses are associated with diarrhea in humans.
Rubella virus is the only non-arthropod-borne togavirus, which is an important human pathogen. The virions are enveloped and have icosahedral nucleocapsid. The genome consists of a linear, single stranded RNA that is non-segmented. Viral replication takes place in the cytoplasm and is released by budding from the cell membrane.
Adenoviruses are member of the family Adenoviridae and are implicated in infections of the eye, the respiratory tract, and the intestinal tract. The virions lack envelope and consist of icosahedral nucleocapsid. The genome consists of linear, double stranded DNA.
Smallpox virus is the DNA virus that is part of the family Poxviridae. The poxviruses are the largest and contain enveloped, complex nucleocapsid. The virions are made up of an inner core, which consists of a double stranded, linear DNA molecule.
Enteroviruses include polioviruses, human echoviruses, and coxsackieviruses. Enteroviruses are a member of the family Picornaviridae and are small, naked viruses with icosahedral nucleocapsid. The virions contain a single stranded, non-segmented linear RNA molecule and replicate in the cytoplasm.
Herpes simplex virus is a DNA virus from the family Herpesviridae. The virus is enveloped with icosahedral nucleocapsid. The genome contains double stranded, linear DNA. The virions replicate in the nucleus, bud through the nuclear membrane, and acquire the envelope.
Sandfly fever virus is a
1 Single stranded DNA with naked icosahedral nucleocapsid
2 Linear double stranded DNA with naked icosahedral nucleocapsid
3 Double stranded circular DNA with naked icosahedral nucleocapsid
4 Double stranded linear DNA with enveloped complex nucleocapsid
5 Double stranded linear DNA with enveloped icosahedral nucleocapsid
6 Double stranded RNA with naked icosahedral nucleocapsid
7 Single stranded linear RNA with naked icosahedral nucleocapsid
8 Single stranded linear RNA with enveloped icosahedral nucleocapsid
9 Single stranded RNA with reverse transcriptase and diploid genome
10 Single stranded circular RNA with 3 segments and enveloped helical nucleocapsid
Single stranded circular RNA with 3 segments and enveloped helical nucleocapsid
Human T-cell lymphotropic viruses belong to the family Retroviridae and are characterized by the presence of diploid genome. The virions of this family are enveloped with the genome, consisting of 2 plus stranded RNA and an enzyme reverse transcriptase. The virions replicate in the nucleus. Viral reverse transcriptase transcribes the double stranded DNA copy of the viral genome. The DNA is circularized and integrated into the host cellular DNA. This integrated DNA is used as a template for transcription of viral RNA.
Papillomavirus are naked icosahedral viruses, which are part of the family Papovaviridae. The genome of the virion consists of a cyclic double stranded DNA molecule. The virions have infectious genome that is replicated in the nucleus. Human papillomaviruses are implicated in warts, cervical cancer, and skin cancer.
Sandfly fever viruses are transmitted by Phlebotomus and can cause infections in humans and sheep. These viruses are a member of the family Bunyaviridae and are arboviruses (those that have wild animal reservoir hosts). The virions are enveloped with helical nucleocapsid. The genome is made up of 3 tubular nucleocapsids, with 3 segments of minus sense single stranded RNA. The virions replicate in the cytoplasm and bud from Golgi membranes of the host.
Parvoviruses are the smallest of viruses, measuring approximately 18 to 26nm in diameter. Parvoviruses are non-enveloped virions with icosahedral nucleocapsid. The genome consists of a single stranded linear DNA genome. Parvoviruses replicate in the nucleus of the cell. B19 is a parvovirus that is associated with erythema infectiosum, a human disease.
Rotaviruses are RNA viruses and are members of the family Reoviridae. Most of the RNA viruses consist of single stranded RNA in their genome. However, the virions of the family Reoviridae consist of linear double stranded RNA, with 10-11 segments. Rotaviruses are naked with icosahedral symmetry. Rotaviruses replicate in the cytoplasm and are released by cell lysis. Rotaviruses are associated with diarrhea in humans.
Rubella virus is the only non-arthropod-borne togavirus, which is an important human pathogen. The virions are enveloped and have icosahedral nucleocapsid. The genome consists of a linear, single stranded RNA that is non-segmented. Viral replication takes place in the cytoplasm and is released by budding from the cell membrane.
Adenoviruses are member of the family Adenoviridae and are implicated in infections of the eye, the respiratory tract, and the intestinal tract. The virions lack envelope and consist of icosahedral nucleocapsid. The genome consists of linear, double stranded DNA.
Smallpox virus is the DNA virus that is part of the family Poxviridae. The poxviruses are the largest and contain enveloped, complex nucleocapsid. The virions are made up of an inner core, which consists of a double stranded, linear DNA molecule.
Enteroviruses include polioviruses, human echoviruses, and coxsackieviruses. Enteroviruses are a member of the family Picornaviridae and are small, naked viruses with icosahedral nucleocapsid. The virions contain a single stranded, non-segmented linear RNA molecule and replicate in the cytoplasm.
Herpes simplex virus is a DNA virus from the family Herpesviridae. The virus is enveloped with icosahedral nucleocapsid. The genome contains double stranded, linear DNA. The virions replicate in the nucleus, bud through the nuclear membrane, and acquire the envelope.
Parvovirus is a
1 Single stranded DNA with naked icosahedral nucleocapsid
2 Linear double stranded DNA with naked icosahedral nucleocapsid
3 Double stranded circular DNA with naked icosahedral nucleocapsid
4 Double stranded linear DNA with enveloped complex nucleocapsid
5 Double stranded linear DNA with enveloped icosahedral nucleocapsid
6 Double stranded RNA with naked icosahedral nucleocapsid
7 Single stranded linear RNA with naked icosahedral nucleocapsid
8 Single stranded linear RNA with enveloped icosahedral nucleocapsid
9 Single stranded RNA with reverse transcriptase and diploid genome
10 Single stranded circular RNA with 3 segments and enveloped helical nucleocapsid
Single stranded DNA with naked icosahedral nucleocapsid
Human T-cell lymphotropic viruses belong to the family Retroviridae and are characterized by the presence of diploid genome. The virions of this family are enveloped with the genome, consisting of 2 plus stranded RNA and an enzyme reverse transcriptase. The virions replicate in the nucleus. Viral reverse transcriptase transcribes the double stranded DNA copy of the viral genome. The DNA is circularized and integrated into the host cellular DNA. This integrated DNA is used as a template for transcription of viral RNA.
Papillomavirus are naked icosahedral viruses, which are part of the family Papovaviridae. The genome of the virion consists of a cyclic double stranded DNA molecule. The virions have infectious genome that is replicated in the nucleus. Human papillomaviruses are implicated in warts, cervical cancer, and skin cancer.
Sandfly fever viruses are transmitted by Phlebotomus and can cause infections in humans and sheep. These viruses are a member of the family Bunyaviridae and are arboviruses (those that have wild animal reservoir hosts). The virions are enveloped with helical nucleocapsid. The genome is made up of 3 tubular nucleocapsids, with 3 segments of minus sense single stranded RNA. The virions replicate in the cytoplasm and bud from Golgi membranes of the host.
Parvoviruses are the smallest of viruses, measuring approximately 18 to 26nm in diameter. Parvoviruses are non-enveloped virions with icosahedral nucleocapsid. The genome consists of a single stranded linear DNA genome. Parvoviruses replicate in the nucleus of the cell. B19 is a parvovirus that is associated with erythema infectiosum, a human disease.
Rotaviruses are RNA viruses and are members of the family Reoviridae. Most of the RNA viruses consist of single stranded RNA in their genome. However, the virions of the family Reoviridae consist of linear double stranded RNA, with 10-11 segments. Rotaviruses are naked with icosahedral symmetry. Rotaviruses replicate in the cytoplasm and are released by cell lysis. Rotaviruses are associated with diarrhea in humans.
Rubella virus is the only non-arthropod-borne togavirus, which is an important human pathogen. The virions are enveloped and have icosahedral nucleocapsid. The genome consists of a linear, single stranded RNA that is non-segmented. Viral replication takes place in the cytoplasm and is released by budding from the cell membrane.
Adenoviruses are member of the family Adenoviridae and are implicated in infections of the eye, the respiratory tract, and the intestinal tract. The virions lack envelope and consist of icosahedral nucleocapsid. The genome consists of linear, double stranded DNA.
Smallpox virus is the DNA virus that is part of the family Poxviridae. The poxviruses are the largest and contain enveloped, complex nucleocapsid. The virions are made up of an inner core, which consists of a double stranded, linear DNA molecule.
Enteroviruses include polioviruses, human echoviruses, and coxsackieviruses. Enteroviruses are a member of the family Picornaviridae and are small, naked viruses with icosahedral nucleocapsid. The virions contain a single stranded, non-segmented linear RNA molecule and replicate in the cytoplasm.
Herpes simplex virus is a DNA virus from the family Herpesviridae. The virus is enveloped with icosahedral nucleocapsid. The genome contains double stranded, linear DNA. The virions replicate in the nucleus, bud through the nuclear membrane, and acquire the envelope.
Rotaviruses are
1 Single stranded DNA with naked icosahedral nucleocapsid
2 Linear double stranded DNA with naked icosahedral nucleocapsid
3 Double stranded circular DNA with naked icosahedral nucleocapsid
4 Double stranded linear DNA with enveloped complex nucleocapsid
5 Double stranded linear DNA with enveloped icosahedral nucleocapsid
6 Double stranded RNA with naked icosahedral nucleocapsid
7 Single stranded linear RNA with naked icosahedral nucleocapsid
8 Single stranded linear RNA with enveloped icosahedral nucleocapsid
9 Single stranded RNA with reverse transcriptase and diploid genome
10 Single stranded circular RNA with 3 segments and enveloped helical nucleocapsid
Double stranded RNA with naked icosahedral nucleocapsid
Human T-cell lymphotropic viruses belong to the family Retroviridae and are characterized by the presence of diploid genome. The virions of this family are enveloped with the genome, consisting of 2 plus stranded RNA and an enzyme reverse transcriptase. The virions replicate in the nucleus. Viral reverse transcriptase transcribes the double stranded DNA copy of the viral genome. The DNA is circularized and integrated into the host cellular DNA. This integrated DNA is used as a template for transcription of viral RNA.
Papillomavirus are naked icosahedral viruses, which are part of the family Papovaviridae. The genome of the virion consists of a cyclic double stranded DNA molecule. The virions have infectious genome that is replicated in the nucleus. Human papillomaviruses are implicated in warts, cervical cancer, and skin cancer.
Sandfly fever viruses are transmitted by Phlebotomus and can cause infections in humans and sheep. These viruses are a member of the family Bunyaviridae and are arboviruses (those that have wild animal reservoir hosts). The virions are enveloped with helical nucleocapsid. The genome is made up of 3 tubular nucleocapsids, with 3 segments of minus sense single stranded RNA. The virions replicate in the cytoplasm and bud from Golgi membranes of the host.
Parvoviruses are the smallest of viruses, measuring approximately 18 to 26nm in diameter. Parvoviruses are non-enveloped virions with icosahedral nucleocapsid. The genome consists of a single stranded linear DNA genome. Parvoviruses replicate in the nucleus of the cell. B19 is a parvovirus that is associated with erythema infectiosum, a human disease.
Rotaviruses are RNA viruses and are members of the family Reoviridae. Most of the RNA viruses consist of single stranded RNA in their genome. However, the virions of the family Reoviridae consist of linear double stranded RNA, with 10-11 segments. Rotaviruses are naked with icosahedral symmetry. Rotaviruses replicate in the cytoplasm and are released by cell lysis. Rotaviruses are associated with diarrhea in humans.
Rubella virus is the only non-arthropod-borne togavirus, which is an important human pathogen. The virions are enveloped and have icosahedral nucleocapsid. The genome consists of a linear, single stranded RNA that is non-segmented. Viral replication takes place in the cytoplasm and is released by budding from the cell membrane.
Adenoviruses are member of the family Adenoviridae and are implicated in infections of the eye, the respiratory tract, and the intestinal tract. The virions lack envelope and consist of icosahedral nucleocapsid. The genome consists of linear, double stranded DNA.
Smallpox virus is the DNA virus that is part of the family Poxviridae. The poxviruses are the largest and contain enveloped, complex nucleocapsid. The virions are made up of an inner core, which consists of a double stranded, linear DNA molecule.
Enteroviruses include polioviruses, human echoviruses, and coxsackieviruses. Enteroviruses are a member of the family Picornaviridae and are small, naked viruses with icosahedral nucleocapsid. The virions contain a single stranded, non-segmented linear RNA molecule and replicate in the cytoplasm.
Herpes simplex virus is a DNA virus from the family Herpesviridae. The virus is enveloped with icosahedral nucleocapsid. The genome contains double stranded, linear DNA. The virions replicate in the nucleus, bud through the nuclear membrane, and acquire the envelope.
Rubella virus is
1 Single stranded DNA with naked icosahedral nucleocapsid
2 Linear double stranded DNA with naked icosahedral nucleocapsid
3 Double stranded circular DNA with naked icosahedral nucleocapsid
4 Double stranded linear DNA with enveloped complex nucleocapsid
5 Double stranded linear DNA with enveloped icosahedral nucleocapsid
6 Double stranded RNA with naked icosahedral nucleocapsid
7 Single stranded linear RNA with naked icosahedral nucleocapsid
8 Single stranded linear RNA with enveloped icosahedral nucleocapsid
9 Single stranded RNA with reverse transcriptase and diploid genome
10 Single stranded circular RNA with 3 segments and enveloped helical nucleocapsid
Single stranded linear RNA with enveloped icosahedral nucleocapsid
Human T-cell lymphotropic viruses belong to the family Retroviridae and are characterized by the presence of diploid genome. The virions of this family are enveloped with the genome, consisting of 2 plus stranded RNA and an enzyme reverse transcriptase. The virions replicate in the nucleus. Viral reverse transcriptase transcribes the double stranded DNA copy of the viral genome. The DNA is circularized and integrated into the host cellular DNA. This integrated DNA is used as a template for transcription of viral RNA.
Papillomavirus are naked icosahedral viruses, which are part of the family Papovaviridae. The genome of the virion consists of a cyclic double stranded DNA molecule. The virions have infectious genome that is replicated in the nucleus. Human papillomaviruses are implicated in warts, cervical cancer, and skin cancer.
Sandfly fever viruses are transmitted by Phlebotomus and can cause infections in humans and sheep. These viruses are a member of the family Bunyaviridae and are arboviruses (those that have wild animal reservoir hosts). The virions are enveloped with helical nucleocapsid. The genome is made up of 3 tubular nucleocapsids, with 3 segments of minus sense single stranded RNA. The virions replicate in the cytoplasm and bud from Golgi membranes of the host.
Parvoviruses are the smallest of viruses, measuring approximately 18 to 26nm in diameter. Parvoviruses are non-enveloped virions with icosahedral nucleocapsid. The genome consists of a single stranded linear DNA genome. Parvoviruses replicate in the nucleus of the cell. B19 is a parvovirus that is associated with erythema infectiosum, a human disease.
Rotaviruses are RNA viruses and are members of the family Reoviridae. Most of the RNA viruses consist of single stranded RNA in their genome. However, the virions of the family Reoviridae consist of linear double stranded RNA, with 10-11 segments. Rotaviruses are naked with icosahedral symmetry. Rotaviruses replicate in the cytoplasm and are released by cell lysis. Rotaviruses are associated with diarrhea in humans.
Rubella virus is the only non-arthropod-borne togavirus, which is an important human pathogen. The virions are enveloped and have icosahedral nucleocapsid. The genome consists of a linear, single stranded RNA that is non-segmented. Viral replication takes place in the cytoplasm and is released by budding from the cell membrane.
Adenoviruses are member of the family Adenoviridae and are implicated in infections of the eye, the respiratory tract, and the intestinal tract. The virions lack envelope and consist of icosahedral nucleocapsid. The genome consists of linear, double stranded DNA.
Smallpox virus is the DNA virus that is part of the family Poxviridae. The poxviruses are the largest and contain enveloped, complex nucleocapsid. The virions are made up of an inner core, which consists of a double stranded, linear DNA molecule.
Enteroviruses include polioviruses, human echoviruses, and coxsackieviruses. Enteroviruses are a member of the family Picornaviridae and are small, naked viruses with icosahedral nucleocapsid. The virions contain a single stranded, non-segmented linear RNA molecule and replicate in the cytoplasm.
Herpes simplex virus is a DNA virus from the family Herpesviridae. The virus is enveloped with icosahedral nucleocapsid. The genome contains double stranded, linear DNA. The virions replicate in the nucleus, bud through the nuclear membrane, and acquire the envelope.
Adenoviruses consist of
1 Single stranded DNA with naked icosahedral nucleocapsid
2 Linear double stranded DNA with naked icosahedral nucleocapsid
3 Double stranded circular DNA with naked icosahedral nucleocapsid
4 Double stranded linear DNA with enveloped complex nucleocapsid
5 Double stranded linear DNA with enveloped icosahedral nucleocapsid
6 Double stranded RNA with naked icosahedral nucleocapsid
7 Single stranded linear RNA with naked icosahedral nucleocapsid
8 Single stranded linear RNA with enveloped icosahedral nucleocapsid
9 Single stranded RNA with reverse transcriptase and diploid genome
10 Single stranded circular RNA with 3 segments and enveloped helical nucleocapsid
Linear double stranded DNA with naked icosahedral nucleocapsid
Human T-cell lymphotropic viruses belong to the family Retroviridae and are characterized by the presence of diploid genome. The virions of this family are enveloped with the genome, consisting of 2 plus stranded RNA and an enzyme reverse transcriptase. The virions replicate in the nucleus. Viral reverse transcriptase transcribes the double stranded DNA copy of the viral genome. The DNA is circularized and integrated into the host cellular DNA. This integrated DNA is used as a template for transcription of viral RNA.
Papillomavirus are naked icosahedral viruses, which are part of the family Papovaviridae. The genome of the virion consists of a cyclic double stranded DNA molecule. The virions have infectious genome that is replicated in the nucleus. Human papillomaviruses are implicated in warts, cervical cancer, and skin cancer.
Sandfly fever viruses are transmitted by Phlebotomus and can cause infections in humans and sheep. These viruses are a member of the family Bunyaviridae and are arboviruses (those that have wild animal reservoir hosts). The virions are enveloped with helical nucleocapsid. The genome is made up of 3 tubular nucleocapsids, with 3 segments of minus sense single stranded RNA. The virions replicate in the cytoplasm and bud from Golgi membranes of the host.
Parvoviruses are the smallest of viruses, measuring approximately 18 to 26nm in diameter. Parvoviruses are non-enveloped virions with icosahedral nucleocapsid. The genome consists of a single stranded linear DNA genome. Parvoviruses replicate in the nucleus of the cell. B19 is a parvovirus that is associated with erythema infectiosum, a human disease.
Rotaviruses are RNA viruses and are members of the family Reoviridae. Most of the RNA viruses consist of single stranded RNA in their genome. However, the virions of the family Reoviridae consist of linear double stranded RNA, with 10-11 segments. Rotaviruses are naked with icosahedral symmetry. Rotaviruses replicate in the cytoplasm and are released by cell lysis. Rotaviruses are associated with diarrhea in humans.
Rubella virus is the only non-arthropod-borne togavirus, which is an important human pathogen. The virions are enveloped and have icosahedral nucleocapsid. The genome consists of a linear, single stranded RNA that is non-segmented. Viral replication takes place in the cytoplasm and is released by budding from the cell membrane.
Adenoviruses are member of the family Adenoviridae and are implicated in infections of the eye, the respiratory tract, and the intestinal tract. The virions lack envelope and consist of icosahedral nucleocapsid. The genome consists of linear, double stranded DNA.
Smallpox virus is the DNA virus that is part of the family Poxviridae. The poxviruses are the largest and contain enveloped, complex nucleocapsid. The virions are made up of an inner core, which consists of a double stranded, linear DNA molecule.
Enteroviruses include polioviruses, human echoviruses, and coxsackieviruses. Enteroviruses are a member of the family Picornaviridae and are small, naked viruses with icosahedral nucleocapsid. The virions contain a single stranded, non-segmented linear RNA molecule and replicate in the cytoplasm.
Herpes simplex virus is a DNA virus from the family Herpesviridae. The virus is enveloped with icosahedral nucleocapsid. The genome contains double stranded, linear DNA. The virions replicate in the nucleus, bud through the nuclear membrane, and acquire the envelope.
Smallpox virus is
1 Single stranded DNA with naked icosahedral nucleocapsid
2 Linear double stranded DNA with naked icosahedral nucleocapsid
3 Double stranded circular DNA with naked icosahedral nucleocapsid
4 Double stranded linear DNA with enveloped complex nucleocapsid
5 Double stranded linear DNA with enveloped icosahedral nucleocapsid
6 Double stranded RNA with naked icosahedral nucleocapsid
7 Single stranded linear RNA with naked icosahedral nucleocapsid
8 Single stranded linear RNA with enveloped icosahedral nucleocapsid
9 Single stranded RNA with reverse transcriptase and diploid genome
10 Single stranded circular RNA with 3 segments and enveloped helical nucleocapsid
Double stranded linear DNA with enveloped complex nucleocapsid
Human T-cell lymphotropic viruses belong to the family Retroviridae and are characterized by the presence of diploid genome. The virions of this family are enveloped with the genome, consisting of 2 plus stranded RNA and an enzyme reverse transcriptase. The virions replicate in the nucleus. Viral reverse transcriptase transcribes the double stranded DNA copy of the viral genome. The DNA is circularized and integrated into the host cellular DNA. This integrated DNA is used as a template for transcription of viral RNA.
Papillomavirus are naked icosahedral viruses, which are part of the family Papovaviridae. The genome of the virion consists of a cyclic double stranded DNA molecule. The virions have infectious genome that is replicated in the nucleus. Human papillomaviruses are implicated in warts, cervical cancer, and skin cancer.
Sandfly fever viruses are transmitted by Phlebotomus and can cause infections in humans and sheep. These viruses are a member of the family Bunyaviridae and are arboviruses (those that have wild animal reservoir hosts). The virions are enveloped with helical nucleocapsid. The genome is made up of 3 tubular nucleocapsids, with 3 segments of minus sense single stranded RNA. The virions replicate in the cytoplasm and bud from Golgi membranes of the host.
Parvoviruses are the smallest of viruses, measuring approximately 18 to 26nm in diameter. Parvoviruses are non-enveloped virions with icosahedral nucleocapsid. The genome consists of a single stranded linear DNA genome. Parvoviruses replicate in the nucleus of the cell. B19 is a parvovirus that is associated with erythema infectiosum, a human disease.
Rotaviruses are RNA viruses and are members of the family Reoviridae. Most of the RNA viruses consist of single stranded RNA in their genome. However, the virions of the family Reoviridae consist of linear double stranded RNA, with 10-11 segments. Rotaviruses are naked with icosahedral symmetry. Rotaviruses replicate in the cytoplasm and are released by cell lysis. Rotaviruses are associated with diarrhea in humans.
Rubella virus is the only non-arthropod-borne togavirus, which is an important human pathogen. The virions are enveloped and have icosahedral nucleocapsid. The genome consists of a linear, single stranded RNA that is non-segmented. Viral replication takes place in the cytoplasm and is released by budding from the cell membrane.
Adenoviruses are member of the family Adenoviridae and are implicated in infections of the eye, the respiratory tract, and the intestinal tract. The virions lack envelope and consist of icosahedral nucleocapsid. The genome consists of linear, double stranded DNA.
Smallpox virus is the DNA virus that is part of the family Poxviridae. The poxviruses are the largest and contain enveloped, complex nucleocapsid. The virions are made up of an inner core, which consists of a double stranded, linear DNA molecule.
Enteroviruses include polioviruses, human echoviruses, and coxsackieviruses. Enteroviruses are a member of the family Picornaviridae and are small, naked viruses with icosahedral nucleocapsid. The virions contain a single stranded, non-segmented linear RNA molecule and replicate in the cytoplasm.
Herpes simplex virus is a DNA virus from the family Herpesviridae. The virus is enveloped with icosahedral nucleocapsid. The genome contains double stranded, linear DNA. The virions replicate in the nucleus, bud through the nuclear membrane, and acquire the envelope.
Enteroviruses contain
1 Single stranded DNA with naked icosahedral nucleocapsid
2 Linear double stranded DNA with naked icosahedral nucleocapsid
3 Double stranded circular DNA with naked icosahedral nucleocapsid
4 Double stranded linear DNA with enveloped complex nucleocapsid
5 Double stranded linear DNA with enveloped icosahedral nucleocapsid
6 Double stranded RNA with naked icosahedral nucleocapsid
7 Single stranded linear RNA with naked icosahedral nucleocapsid
8 Single stranded linear RNA with enveloped icosahedral nucleocapsid
9 Single stranded RNA with reverse transcriptase and diploid genome
10 Single stranded circular RNA with 3 segments and enveloped helical nucleocapsid
Single stranded linear RNA with naked icosahedral nucleocapsid
Human T-cell lymphotropic viruses belong to the family Retroviridae and are characterized by the presence of diploid genome. The virions of this family are enveloped with the genome, consisting of 2 plus stranded RNA and an enzyme reverse transcriptase. The virions replicate in the nucleus. Viral reverse transcriptase transcribes the double stranded DNA copy of the viral genome. The DNA is circularized and integrated into the host cellular DNA. This integrated DNA is used as a template for transcription of viral RNA.
Papillomavirus are naked icosahedral viruses, which are part of the family Papovaviridae. The genome of the virion consists of a cyclic double stranded DNA molecule. The virions have infectious genome that is replicated in the nucleus. Human papillomaviruses are implicated in warts, cervical cancer, and skin cancer.
Sandfly fever viruses are transmitted by Phlebotomus and can cause infections in humans and sheep. These viruses are a member of the family Bunyaviridae and are arboviruses (those that have wild animal reservoir hosts). The virions are enveloped with helical nucleocapsid. The genome is made up of 3 tubular nucleocapsids, with 3 segments of minus sense single stranded RNA. The virions replicate in the cytoplasm and bud from Golgi membranes of the host.
Parvoviruses are the smallest of viruses, measuring approximately 18 to 26nm in diameter. Parvoviruses are non-enveloped virions with icosahedral nucleocapsid. The genome consists of a single stranded linear DNA genome. Parvoviruses replicate in the nucleus of the cell. B19 is a parvovirus that is associated with erythema infectiosum, a human disease.
Rotaviruses are RNA viruses and are members of the family Reoviridae. Most of the RNA viruses consist of single stranded RNA in their genome. However, the virions of the family Reoviridae consist of linear double stranded RNA, with 10-11 segments. Rotaviruses are naked with icosahedral symmetry. Rotaviruses replicate in the cytoplasm and are released by cell lysis. Rotaviruses are associated with diarrhea in humans.
Rubella virus is the only non-arthropod-borne togavirus, which is an important human pathogen. The virions are enveloped and have icosahedral nucleocapsid. The genome consists of a linear, single stranded RNA that is non-segmented. Viral replication takes place in the cytoplasm and is released by budding from the cell membrane.
Adenoviruses are member of the family Adenoviridae and are implicated in infections of the eye, the respiratory tract, and the intestinal tract. The virions lack envelope and consist of icosahedral nucleocapsid. The genome consists of linear, double stranded DNA.
Smallpox virus is the DNA virus that is part of the family Poxviridae. The poxviruses are the largest and contain enveloped, complex nucleocapsid. The virions are made up of an inner core, which consists of a double stranded, linear DNA molecule.
Enteroviruses include polioviruses, human echoviruses, and coxsackieviruses. Enteroviruses are a member of the family Picornaviridae and are small, naked viruses with icosahedral nucleocapsid. The virions contain a single stranded, non-segmented linear RNA molecule and replicate in the cytoplasm.
Herpes simplex virus is a DNA virus from the family Herpesviridae. The virus is enveloped with icosahedral nucleocapsid. The genome contains double stranded, linear DNA. The virions replicate in the nucleus, bud through the nuclear membrane, and acquire the envelope.
Herpes simplex virus contains
1 Single stranded DNA with naked icosahedral nucleocapsid
2 Linear double stranded DNA with naked icosahedral nucleocapsid
3 Double stranded circular DNA with naked icosahedral nucleocapsid
4 Double stranded linear DNA with enveloped complex nucleocapsid
5 Double stranded linear DNA with enveloped icosahedral nucleocapsid
6 Double stranded RNA with naked icosahedral nucleocapsid
7 Single stranded linear RNA with naked icosahedral nucleocapsid
8 Single stranded linear RNA with enveloped icosahedral nucleocapsid
9 Single stranded RNA with reverse transcriptase and diploid genome
10 Single stranded circular RNA with 3 segments and enveloped helical nucleocapsid
Double stranded linear DNA with enveloped icosahedral nucleocapsid
Human T-cell lymphotropic viruses belong to the family Retroviridae and are characterized by the presence of diploid genome. The virions of this family are enveloped with the genome, consisting of 2 plus stranded RNA and an enzyme reverse transcriptase. The virions replicate in the nucleus. Viral reverse transcriptase transcribes the double stranded DNA copy of the viral genome. The DNA is circularized and integrated into the host cellular DNA. This integrated DNA is used as a template for transcription of viral RNA.
Papillomavirus are naked icosahedral viruses, which are part of the family Papovaviridae. The genome of the virion consists of a cyclic double stranded DNA molecule. The virions have infectious genome that is replicated in the nucleus. Human papillomaviruses are implicated in warts, cervical cancer, and skin cancer.
Sandfly fever viruses are transmitted by Phlebotomus and can cause infections in humans and sheep. These viruses are a member of the family Bunyaviridae and are arboviruses (those that have wild animal reservoir hosts). The virions are enveloped with helical nucleocapsid. The genome is made up of 3 tubular nucleocapsids, with 3 segments of minus sense single stranded RNA. The virions replicate in the cytoplasm and bud from Golgi membranes of the host.
Parvoviruses are the smallest of viruses, measuring approximately 18 to 26nm in diameter. Parvoviruses are non-enveloped virions with icosahedral nucleocapsid. The genome consists of a single stranded linear DNA genome. Parvoviruses replicate in the nucleus of the cell. B19 is a parvovirus that is associated with erythema infectiosum, a human disease.
Rotaviruses are RNA viruses and are members of the family Reoviridae. Most of the RNA viruses consist of single stranded RNA in their genome. However, the virions of the family Reoviridae consist of linear double stranded RNA, with 10-11 segments. Rotaviruses are naked with icosahedral symmetry. Rotaviruses replicate in the cytoplasm and are released by cell lysis. Rotaviruses are associated with diarrhea in humans.
Rubella virus is the only non-arthropod-borne togavirus, which is an important human pathogen. The virions are enveloped and have icosahedral nucleocapsid. The genome consists of a linear, single stranded RNA that is non-segmented. Viral replication takes place in the cytoplasm and is released by budding from the cell membrane.
Adenoviruses are member of the family Adenoviridae and are implicated in infections of the eye, the respiratory tract, and the intestinal tract. The virions lack envelope and consist of icosahedral nucleocapsid. The genome consists of linear, double stranded DNA.
Smallpox virus is the DNA virus that is part of the family Poxviridae. The poxviruses are the largest and contain enveloped, complex nucleocapsid. The virions are made up of an inner core, which consists of a double stranded, linear DNA molecule.
Enteroviruses include polioviruses, human echoviruses, and coxsackieviruses. Enteroviruses are a member of the family Picornaviridae and are small, naked viruses with icosahedral nucleocapsid. The virions contain a single stranded, non-segmented linear RNA molecule and replicate in the cytoplasm.
Herpes simplex virus is a DNA virus from the family Herpesviridae. The virus is enveloped with icosahedral nucleocapsid. The genome contains double stranded, linear DNA. The virions replicate in the nucleus, bud through the nuclear membrane, and acquire the envelope.
Which of the following viruses consists of circular DNA that is partially double stranded and partially single stranded?
1 Hepatitis B virus
2 Varicella-zoster virus
3 Lassa fever virus
4 Epstein-Barr virus
5 Respiratory syncytial virus
Hepatitis B virus
Hepatitis B virus is the DNA virus that is part of the Hepadnaviridae family. The characteristic feature of the virus from this family is that the genome consists of a circular DNA that is part double stranded and part single stranded. The virions are spherical particles with an envelope. Hepatitis B virus consists of icosahedral core within a closely adherent capsid that contains cellular lipid, glycoproteins, and a virus-specific surface antigen called Hepatitis B surface antigen (HBsAg).
Respiratory syncytial virus is RNA virus that has linear single stranded nonsegmented RNA.
Lassa fever virus has a circular single stranded RNA in 2 segments.
Varicella-zoster virus and Epstein-Barr virus consist of a linear double stranded DNA.
The incubation period for hepatitis B is approximately
1 1-3 days
2 5-10 days
3 10-20 days
4 15-40 days
5 50-160 days
50-160 days
Hepatitis B is also called serum hepatitis and is caused by a DNA virus known as hepatitis B virus. It is transmitted primarily by parentral route with infected blood or blood products. The hepatitis B virus can also be transmitted by sexual contact or with contaminated body fluids. Hepatitis B has a longer incubation period which is approximately 50-160 days. The onset of disease is gradual and the infection can be acute or self-limiting or can lead to persistent viremia and chronic liver disease with immunologic complications.
Hepatitis A is transmitted by feco-oral route and has an incubation period of 15-40 days.
Which of the following serological markers is first to appear during the incubation period of hepatitis B?
1 HBcAg
2 HBsAg
3 Anti HBcAg-IgM
4 Anti HBsAg
5 Anti HBeAg
HBsAg
The course of hepatitis B viral infection and nature of the disease can by described by detection of serological markers in the laboratory using ELISA or EIA. HBsAg is the first to appear and can be detected during the incubation period of hepatitis B. The test for detection of HBcAg is not yet available. Anti-HBsAg and anti-HBeAg appear after disappearance of HBsAg. Anti-HBcAg-IgM along with HBsAg can be used as an indicator of acute infection.
Which of the following is an enveloped RNA virus from the family Flaviviridae and is the major cause of post-transfusion hepatitis?
1 Hepatitis A virus
2 Hepatitis B virus
3 Hepatitis C virus
4 Hepatitis D virus
5 Hepatitis E virus
Hepatitis C virus
Hepatitis C is an enveloped icosahedral RNA virus with gene order characteristic of the family Flaviviridae. The genome of Hepatitis C is infectious and consists of a linear single stranded 9.5 kb molecule of RNA. The virus replicates in the cytoplasm. Hepatitis C is transmitted by paranteral and sexual routes. It is the most common cause of post-transfusion hepatitis. Hepatitis C is associated with acute infection, chronic liver disease, and cirrhosis. Hepatitis C viral infection may serve as a predisposing factor in primary hepatocellular carcinoma.
Hepatitis B virus is an enveloped DNA virus that is part of the Hepadnaviridae family. The genome of Hepadnaviridae family is characterized by the presence of a circular, partially double stranded DNA molecule. Hepatitis B virus consists of a icosahedral core within a closely adherent capsid that contains cellular lipid, glycoproteins, and a virus-specific surface antigen called Hepatitis B surface antigen (HBsAg). The virus encodes a reverse transcriptase and replicates through an RNA intermediate. Hepatitis B virus shows tropism to the liver and replicates in hepatocytes. Hepatitis B is also called serum hepatitis and is caused by a DNA virus known as hepatitis B virus. It is transmitted by parenteral or sexual routes. Hepatitis B has a longer incubation period, which is approximately 50-160 days. Onset of the disease is gradual and the infection can be acute or self-limiting or can lead to persistent viremia and chronic liver disease with immunologic complications.
The Hepatitis A virus is a naked icosahedron that is member of the Picornaviridae family. The genome of this virus is infectious and contains a single linear molecule of single stranded RNA. Hepatitis A is transmitted by feco-oral routes and was known as infectious hepatitis. The virus enters the body by ingestion and multiplies in intestinal epithelial cells. The virus then enters the circulation and invades parenchymal cells in the liver. Incubation period for Hepatitis A is 15-40 days.
Hepatitis D virus is a very small virus with tiny genome and is classified under genus Deltavirus. It is defective satellite virus and needs Hepatitis B virus as helper, i.e., it is infective only in the presence of Hepatitis B virus. The outer capsid of the virion contains Hepatitis B surface antigen, which is encoded by HBV co-infecting the same cell.
Hepatitis E virus is a naked virus, which has icosahedral capsid with surface depression. Hepatitis E virus is from the family Calciviridae and contains a single molecule of a single stranded RNA. Hepatitis A is transmitted by feco-oral routes and by contaminated food and water. Hepatitis E is associated with cholestasis and has a higher fatality rate in pregnant women.
Hepatitis A virus and Hepatitis E virus are not associated with:
Parenteral transmission.
Chronic carrier state.
Chronic hepatitis.
Cirrhosis.
Hepatocellular carcinoma.
Hepatitis B virus, Hepatitis C virus, and Hepatitis D virus are associated with:
Parenteral transmission.
Chronic carrier state.
Chronic hepatitis.
Cirrhosis.
Hepatocellular carcinoma.
Which of the following is a DNA virus that replicates through a circular RNA intermediate and is a member of the Hepadnaviridae family?
Answer Choices
1 Hepatitis A virus
2 Hepatitis B virus
3 Hepatitis C virus
4 Hepatitis D virus
5 Hepatitis E virus
Hepatitis B virus
Hepatitis C is an enveloped icosahedral RNA virus with gene order characteristic of the family Flaviviridae. The genome of Hepatitis C is infectious and consists of a linear single stranded 9.5 kb molecule of RNA. The virus replicates in the cytoplasm. Hepatitis C is transmitted by paranteral and sexual routes. It is the most common cause of post-transfusion hepatitis. Hepatitis C is associated with acute infection, chronic liver disease, and cirrhosis. Hepatitis C viral infection may serve as a predisposing factor in primary hepatocellular carcinoma.
Hepatitis B virus is an enveloped DNA virus that is part of the Hepadnaviridae family. The genome of Hepadnaviridae family is characterized by the presence of a circular, partially double stranded DNA molecule. Hepatitis B virus consists of a icosahedral core within a closely adherent capsid that contains cellular lipid, glycoproteins, and a virus-specific surface antigen called Hepatitis B surface antigen (HBsAg). The virus encodes a reverse transcriptase and replicates through an RNA intermediate. Hepatitis B virus shows tropism to the liver and replicates in hepatocytes. Hepatitis B is also called serum hepatitis and is caused by a DNA virus known as hepatitis B virus. It is transmitted by parenteral or sexual routes. Hepatitis B has a longer incubation period, which is approximately 50-160 days. Onset of the disease is gradual and the infection can be acute or self-limiting or can lead to persistent viremia and chronic liver disease with immunologic complications.
The Hepatitis A virus is a naked icosahedron that is member of the Picornaviridae family. The genome of this virus is infectious and contains a single linear molecule of single stranded RNA. Hepatitis A is transmitted by feco-oral routes and was known as infectious hepatitis. The virus enters the body by ingestion and multiplies in intestinal epithelial cells. The virus then enters the circulation and invades parenchymal cells in the liver. Incubation period for Hepatitis A is 15-40 days.
Hepatitis D virus is a very small virus with tiny genome and is classified under genus Deltavirus. It is defective satellite virus and needs Hepatitis B virus as helper, i.e., it is infective only in the presence of Hepatitis B virus. The outer capsid of the virion contains Hepatitis B surface antigen, which is encoded by HBV co-infecting the same cell.
Hepatitis E virus is a naked virus, which has icosahedral capsid with surface depression. Hepatitis E virus is from the family Calciviridae and contains a single molecule of a single stranded RNA. Hepatitis A is transmitted by feco-oral routes and by contaminated food and water. Hepatitis E is associated with cholestasis and has a higher fatality rate in pregnant women.
Hepatitis A virus and Hepatitis E virus are not associated with:
Parenteral transmission.
Chronic carrier state.
Chronic hepatitis.
Cirrhosis.
Hepatocellular carcinoma.
Hepatitis B virus, Hepatitis C virus, and Hepatitis D virus are associated with:
Parenteral transmission.
Chronic carrier state.
Chronic hepatitis.
Cirrhosis.
Hepatocellular carcinoma.
Which of the following is an etiological agent of infectious hepatitis and a member of the Picornaviridae family?
1 Hepatitis A virus
2 Hepatitis B virus
3 Hepatitis C virus
4 Hepatitis D virus
5 Hepatitis E virus
Hepatitis A virus
Hepatitis C is an enveloped icosahedral RNA virus with gene order characteristic of the family Flaviviridae. The genome of Hepatitis C is infectious and consists of a linear single stranded 9.5 kb molecule of RNA. The virus replicates in the cytoplasm. Hepatitis C is transmitted by paranteral and sexual routes. It is the most common cause of post-transfusion hepatitis. Hepatitis C is associated with acute infection, chronic liver disease, and cirrhosis. Hepatitis C viral infection may serve as a predisposing factor in primary hepatocellular carcinoma.
Hepatitis B virus is an enveloped DNA virus that is part of the Hepadnaviridae family. The genome of Hepadnaviridae family is characterized by the presence of a circular, partially double stranded DNA molecule. Hepatitis B virus consists of a icosahedral core within a closely adherent capsid that contains cellular lipid, glycoproteins, and a virus-specific surface antigen called Hepatitis B surface antigen (HBsAg). The virus encodes a reverse transcriptase and replicates through an RNA intermediate. Hepatitis B virus shows tropism to the liver and replicates in hepatocytes. Hepatitis B is also called serum hepatitis and is caused by a DNA virus known as hepatitis B virus. It is transmitted by parenteral or sexual routes. Hepatitis B has a longer incubation period, which is approximately 50-160 days. Onset of the disease is gradual and the infection can be acute or self-limiting or can lead to persistent viremia and chronic liver disease with immunologic complications.
The Hepatitis A virus is a naked icosahedron that is member of the Picornaviridae family. The genome of this virus is infectious and contains a single linear molecule of single stranded RNA. Hepatitis A is transmitted by feco-oral routes and was known as infectious hepatitis. The virus enters the body by ingestion and multiplies in intestinal epithelial cells. The virus then enters the circulation and invades parenchymal cells in the liver. Incubation period for Hepatitis A is 15-40 days.
Hepatitis D virus is a very small virus with tiny genome and is classified under genus Deltavirus. It is defective satellite virus and needs Hepatitis B virus as helper, i.e., it is infective only in the presence of Hepatitis B virus. The outer capsid of the virion contains Hepatitis B surface antigen, which is encoded by HBV co-infecting the same cell.
Hepatitis E virus is a naked virus, which has icosahedral capsid with surface depression. Hepatitis E virus is from the family Calciviridae and contains a single molecule of a single stranded RNA. Hepatitis A is transmitted by feco-oral routes and by contaminated food and water. Hepatitis E is associated with cholestasis and has a higher fatality rate in pregnant women.
Hepatitis A virus and Hepatitis E virus are not associated with:
Parenteral transmission.
Chronic carrier state.
Chronic hepatitis.
Cirrhosis.
Hepatocellular carcinoma.
Hepatitis B virus, Hepatitis C virus, and Hepatitis D virus are associated with:
Parenteral transmission.
Chronic carrier state.
Chronic hepatitis.
Cirrhosis.
Hepatocellular carcinoma.
Which of the following is a non-enveloped RNA virus from the family Calciviridae that is associated with cholestasis?
1 Hepatitis A virus
2 Hepatitis B virus
3 Hepatitis C virus
4 Hepatitis D virus
5 Hepatitis E virus
Hepatitis E virus
Hepatitis C is an enveloped icosahedral RNA virus with gene order characteristic of the family Flaviviridae. The genome of Hepatitis C is infectious and consists of a linear single stranded 9.5 kb molecule of RNA. The virus replicates in the cytoplasm. Hepatitis C is transmitted by paranteral and sexual routes. It is the most common cause of post-transfusion hepatitis. Hepatitis C is associated with acute infection, chronic liver disease, and cirrhosis. Hepatitis C viral infection may serve as a predisposing factor in primary hepatocellular carcinoma.
Hepatitis B virus is an enveloped DNA virus that is part of the Hepadnaviridae family. The genome of Hepadnaviridae family is characterized by the presence of a circular, partially double stranded DNA molecule. Hepatitis B virus consists of a icosahedral core within a closely adherent capsid that contains cellular lipid, glycoproteins, and a virus-specific surface antigen called Hepatitis B surface antigen (HBsAg). The virus encodes a reverse transcriptase and replicates through an RNA intermediate. Hepatitis B virus shows tropism to the liver and replicates in hepatocytes. Hepatitis B is also called serum hepatitis and is caused by a DNA virus known as hepatitis B virus. It is transmitted by parenteral or sexual routes. Hepatitis B has a longer incubation period, which is approximately 50-160 days. Onset of the disease is gradual and the infection can be acute or self-limiting or can lead to persistent viremia and chronic liver disease with immunologic complications.
The Hepatitis A virus is a naked icosahedron that is member of the Picornaviridae family. The genome of this virus is infectious and contains a single linear molecule of single stranded RNA. Hepatitis A is transmitted by feco-oral routes and was known as infectious hepatitis. The virus enters the body by ingestion and multiplies in intestinal epithelial cells. The virus then enters the circulation and invades parenchymal cells in the liver. Incubation period for Hepatitis A is 15-40 days.
Hepatitis D virus is a very small virus with tiny genome and is classified under genus Deltavirus. It is defective satellite virus and needs Hepatitis B virus as helper, i.e., it is infective only in the presence of Hepatitis B virus. The outer capsid of the virion contains Hepatitis B surface antigen, which is encoded by HBV co-infecting the same cell.
Hepatitis E virus is a naked virus, which has icosahedral capsid with surface depression. Hepatitis E virus is placed in a sole genus Hepevirus, within a new family Hepeviridae, and contains a single molecule of a single stranded RNA. Hepatitis A is transmitted by feco-oral routes and by contaminated food and water. Hepatitis E is associated with cholestasis and has a higher fatality rate in pregnant women.
Hepatitis A virus and Hepatitis E virus are not associated with:
Parenteral transmission.
Chronic carrier state.
Chronic hepatitis.
Cirrhosis.
Hepatocellular carcinoma.
Hepatitis B virus, Hepatitis C virus, and Hepatitis D virus are associated with:
Parenteral transmission.
Chronic carrier state.
Chronic hepatitis.
Cirrhosis.
Hepatocellular carcinoma.
Refer to the image. The 26-year-old male seen in the image is HIV positive with a CD4 count less than 200. While he was in the hospital for the treatment of his miliary Tb, he developed smooth, skin-colored, umbilicated papules on his face. The lesions are asymptomatic but spreading gradually to the other parts of the body and causing cosmetic problems to the patient. What is the name of this skin infection?
1 Verrucae vulgaris
2 Filiform warts
3 Condyloma acuminata
4 Kaposi’s sarcoma
5 Molluscum contagiosum
Molluscum contagiosum
Molluscum contagiosum is a poxvirus infection characterized by skin-colored, smooth, waxy, umbilicated papules 2 to 10 mm in diameter. Transmission can be direct or venereal. Its contagiousness to others varies. The lesions may be seen anywhere on the skin, face, body, or genital area. They are usually asymptomatic unless secondarily infected. This disease is quite common in children, and the lesions can be widespread in patients with reduced cellular immunity.
Verrucae vulgaris is the other name for common warts. They are sharply demarcated, rough-surfaced, round, irregular, light gray, yellow, brown, or grayish black lesions. Filiform warts are long, narrow, small growths of skin, usually seen on the eyelids, face, neck, or lips.
Condyloma acuminata is the name for genital warts. They are moist, soft, pink, or red swellings that grow rapidly and become pedunculated. They most commonly occur on warm, moist surfaces in the subpreputial area, perineum, vaginal wall, cervix, penile shaft in men, and urethral meatus.
Kaposi’s sarcoma is a vascular skin tumor associated with AIDS. They may be the first notable manifestation of AIDS. The lesions start as pink or red papules, round or oval, and appear first on the upper body and mucosa. They may become widely disseminated on the skin and are associated with organ and lymph node involvement. This patient does not have the typical Kaposi’s sarcoma lesions.
A 7-year-old boy who lives in Uganda develops a large, disfiguring mass on his jaw. The mass develops rapidly. A biopsy confirms that he has lymphoma. The pathologist comments that on histologic examination, the biopsy looks like a “starry sky”. What virus is associated with the development of this type of lymphoma?
1 Human papilloma virus
2 Hepatitis B
3 Varicella-zoster virus
4 HTLV-1
5 Epstein-Barr virus
Epstein-Barr virus
This boy has Burkitt’s lymphoma. Burkitt’s lymphoma is neoplasm of B cells. Burkitt’s lymphoma can be either endemic (the African form of Burkitt’s’ lymphoma) or non-endemic. A large percentage of the cases of African Burkitt’s lymphoma involve the jaw. The phrase “starry sky” is a descriptive phrase for the pathologic appearance on microscopy.
Epstein Barr virus is a herpesvirus. Epstein Barr virus is the cause of infectious mononucleosis. Epstein-Barr virus is associated with the development of the African form of Burkitt’s lymphoma. Epstein-Barr virus is also associated with nasopharyngeal carcinoma.
Hepatitis B virus is a DNA virus. It is also referred to as the Dane particle. There is an association of hepatitis B infection and the development of hepatocellular carcinoma.
Human papilloma virus is a papovavirus. Human papilloma virus is responsible for warts. Human papilloma virus is associated with the development of cervical cancer.
Varicella-zoster virus is a herpesvirus. Varicella zoster virus is responsible for chicken pox and shingles, among other things. Varicella-zoster virus is not associated with the development of cancer in men.
HTLV is a retrovirus. HTLV-I is associated with T-cell leukemia/lymphoma.
