DNA VIRUSES (ENVELOPED DNA VIRUSES) Flashcards
Large (150-200 nm), double-stranded DNA, enveloped viruses.
Herpes virus
What are the four components of a Herpesvirus
Nucleic acid core
capsid,
tegument,
and the envelope.
An asymmetric structure made of a fibrous-like material that surrounds the capsid and contains 20 different proteins.
tegument
How many human herpes group viruses are there?
Eight.
Which viruses are included in the human herpes group?
-HSV types 1 and 2 (HSV-1 and HSV-2),
-Varicella-zoster virus (VZV),
-Epstein-Barr virus (EBV),
-Cytomegalovirus (CMV),
-Human herpes virus types 6 (HHV-6), 7 (HHV-7), and 8 (HHV-8),
-Kaposi sarcoma–associated herpes virus (KSHV).
Enveloped viruses with icosahedral nucleocapsid and linear double-stranded DNA.
HSV types 1 and 2 (HSV-1 and HSV-2), Varicella-zoster virus (VZV),
Epstein-Barr virus (EBV),
Cytomegalovirus (CMV)
What are some shared characteristics of HSV-1 and HSV-2?
-Variable host range,
-short replication cycle,
-rapid spread in cell culture,
-efficient destruction of infected cells,
-and ability to establish latency in the sensory ganglia of the CNS.
What types of diseases do HSV-1 and HSV-2 cause?
Mucous membrane and skin lesions, ocular, visceral, and CNS diseases.
How are HSV-1 and HSV-2 transmitted?
HSV-1: saliva or direct contact; HSV-2: sexual contact.
Where does HSV-1 infection typically occur?
oropharyngeal mucosa.
Where does HSV-2 infection typically occur?
At genital sites.
At what age does primary HSV-1 infection usually occur?
By the time a child reaches the age of 5 years.
What is a defining characteristic of herpes infection?
The recurrence of ulcerative anogenital skin lesions after the primary infection.
What is seen on a Tzanck smear in herpes infection?
Multinucleated giant cells.
What are Cowdry Type A inclusions?
Large, pink to purple nuclear inclusions.
How long do mucosal lesions from HSV-1 typically last?
4 to 7 days.
What are the common names for lesions caused by HSV-1 and HSV-2?
Herpes labialis, facialis, or febrilis; orolabial lesions are commonly referred to as cold sores or fever blisters.
Where do HSV-2 vesicles typically form in women and men?
In women: mucosal membranes, labia, and vagina
In men: shaft of the penis, prepuce (foreskin), and glans penis.
What systemic symptoms often accompany primary HSV-2 infection in women?
Fever, headache, malaise, and generalized myalgias.
What is the most commonly reported viral CNS infection?
HSV-1
What is the gold standard for herpes virus identification?
Cell culture.
What should be done with a herpes lesion or vesicle for cell culture?
It should be punctured, and the vesicular fluid absorbed with a swab, making sure to swab the base of the vesicle.
What are some cell lines used for herpes virus culture?
A-549, MRC-5, or Vero cell lines.
What is a rapid, sensitive, and inexpensive method for herpes virus diagnosis?
Direct antigen testing.
What is a more sensitive method than cell culture and antigen detection for herpes virus?
Nucleic acid amplification assays (PCR).
What is beneficial for the rapid diagnosis and treatment of herpes viral encephalitis?
Molecular amplification.
What disease is caused by VZV and characterized by a maculopapular rash?
Chicken pox.
How is VZV transmission increased during inclement months?
Individuals are typically in close proximity, spending more time indoors.
What is the mode of transmission (MOT) for VZV?
Person to person via respiratory secretions.
Where does VZV initially infect the body?
The conjunctiva or mucosa of the upper respiratory tract.
What happens four to six days after the initial VZV infection?
Infected T cells enter the bloodstream and cause primary viremia.
What occurs during secondary viremia in VZV infection?
Infected T cells invade the liver, spleen, and other organs, causing a second round of infection.
When does VZV cause the characteristic vesicular rash of chickenpox (dewdrop on a rose petal appearance)?
14 days after the initial infection.
What are the initial symptoms of VZV infection?
fever and malaise that appear before the onset of the maculopapular rash on the trunk and scalp.
reactivation of VZV, occurring in immunocompromised individuals older than 45 years old; dermatomal
Shingles
What stains can be used to identify VZV inclusions and giant cells?
Tzanck smear, Giemsa, or hematoxylin-eosin stain.
What is a painful condition that may accompany shingles?
Postherpetic neuralgia.
Is laboratory diagnosis recommended for uncomplicated cases of VZV infection in healthy individuals?
No, it is not recommended.
additional rapid method for diagnosis
Direct identification of viral antigens
What characteristic cytopathic effect (CPE) does VZV produce in cell culture?
Small clusters of ovoid cells in fibroid cells such as MRC-5, HF, and A549.
How long does it typically take for VZV to show positivity in cell culture?
7 to 10 days.
What is a simplified method of detecting VZV compared to regular cell culture?
Shell vial cultures.
What indicates a positive specimen for VZV under a fluorescent microscope?
Cytoplasmic, apple-green fluorescence.
What serologic assays are available to determine a patient’s immune status for VZV?
ELISA for VZV IgG and IgM antibodies.
What disease is commonly associated with EBV and is also known as the “kissing disease”?
Infectious mononucleosis (IM).
How is EBV typically transmitted?
EBV is transmitted in the saliva of infected patients, typically affecting adolescents and young adults.
What are the common symptoms and diseases of infectious mononucleosis caused by EBV?
Fever,
sore throat,
headache,
malaise, fatigue,
lymphadenopathy,
and splenomegaly.
Which cells does EBV primarily infect?
BV primarily infects lymphoid cells, especially B lymphocytes.
What are nonspecific heterophile antibodies also known as?
Paul-Bunnell antibodies.
When does the antibody (IgM) to the viral capsid antigen (VCA) appear after EBV infection?
Within 4 weeks after infection.
What does the presence of IgG and IgA antibodies to the early antigen (EA) indicate?
It indicates an acute or recent infection.
What is the final diagnostic serologic marker for EBV and when does it appear?
the antibody to the nuclear antigen (EBNA), which appears within 1 month of infection and peaks approximately 6 to 12 months after infection.
What types of cancers are associated with EBV?
-Burkitt’s lymphoma (common in African people),
-Nasopharyngeal carcinoma (common in Chinese people),
-B-cell lymphomas.
What condition associated with EBV is seen in AIDS patients?
Hairy leukoplakia.
is recognized as an important agent in the development of lymphoma or other lymphoproliferative disorders in transplant recipients.
EBV
What is a common cause of congenital birth defects?
Cytomegalovirus (CMV).
What does the TORCH panel screen for?
Toxoplasma, Rubella, CMV, and HSV-1.
How is CMV transmitted?
CMV is transmitted transplacentally, through organ transplants, and via human body fluids.
What type of illness does CMV cause in immunocompromised patients?
CMV causes an infectious mononucleosis-like illness in immunocompromised patients.
How is CMV identified in the laboratory?
CMV is identified using viral cell culture, serologic tests for IgM and IgG antibodies, direct antigen detection, and nucleic acid testing.
What is a characteristic histopathological feature of CMV?
Giant cells with Owl’s eye inclusions.
What is a unique feature of the herpes virus family?
Their hallmark characteristic of latency, meaning they are capable of viral recurrence or reactivation.
What diseases are associated with HSV-1 and HSV-2?
HSV-1 is associated with mucous membrane disease or life-threatening encephalitis, while HSV-2 is associated with mucous membrane vesicles or aseptic meningitis.
What condition is caused by Varicella-Zoster Virus (VZV)?
Localized lesions, also known as shingles.
a symptomatic shedding of virus in the oropharynx or as disseminated disease in
immunocompromised patients
EBV
ecurs symptomatically as a pathogen in many tissues, such as the heart, gastrointestinal tract, lung, and brain.
CMV
What do HHV-6 and HHV-7 cause in compromised hosts?
They cause reactivation disease.
What is the largest and most complex of all viruses?
Poxviridae
What type of genome does Poxviridae have?
Double-stranded DNA genome
What is the shape and size of Poxviridae structures?
Oval or brick-shaped structures, 200 to 400 nm in length
What disease caused by the Variola virus has been eradicated from the Earth?
Smallpox
What is the incubation period for smallpox?
7-14 days
How is the Variola virus transmitted?
Through aerosol or contact
What are the two subtypes of the Variola virus?
Variola major and Variola minor
What histopathological feature is associated with smallpox?
Guarnieri bodies
Where is monkeypox commonly found?
In the tropical rain forests of Africa
What is the host reservoir for monkeypox?
One or more rodent species
What are the initial symptoms of monkeypox?
Fever and headache, followed by a rash and lymphadenopathy
How long can monkeypox illness last?
2 to 4 weeks
What type of lesions are caused by Molluscum contagiosum?
Pinkish, papular skin lesions with an umbilicated center
-Single or small clusters of lesions
-Only host is humans
Molluscum contagiosum
How is Molluscum contagiosum transmitted?
Through direct contact, fomites, or sexually through intimate contact
What is the laboratory diagnosis method for Molluscum contagiosum?
Biopsy of the lesions and histologic examination (Henderson-Peter bodies)
How is Orf transmitted to humans?
Through direct contact with infected sheep
What symptoms are associated with Orf infection?
Single or multiple nodules, low-grade fever, and lymph node swelling
How long does it usually take for Orf infection to resolve?
4 to 6 weeks
What is the prototype virus of the Hepadnaviridae family?
Hepatitis B virus (HBV)
How do Hepadnaviridae viruses replicate?
Through reverse transcription and then DNA replication
What type of genome do Hepadnaviridae viruses have?
Circular, partially double-stranded DNA
Pleomorphic, enveloped viruses containing circular, partially double-stranded DNA that
replicates through an RNA intermediate
HBV
What is the incubation period for HBV?
Usually 1 to 3 months (10-12 weeks) , but it may be longer
What is the primary route of transmission for HBV?
Percutaneous exposure to blood or blood products
what are the initial symptoms of acute HBV infection?
Nonspecific, mild, flu-like symptoms
What is a significant worldwide cause of liver cirrhosis and hepatocellular carcinoma?
Chronic HBV infection
Fatal disease is most likely to occur in people coinfected with the?
hepatitis D virus (delta agent)
What is the most reliable marker for identifying HBV infection?
Hepatitis B surface antigen (HBsAg)
- Patient has the disease (chronic, acute, or asymptomatic carrier)
- Precedes onset of symptoms and elevation of liver enzymes
HbsAg
What is the most common type of immunoassay used for HBV diagnosis?
EIA (Enzyme Immunoassay) format
Can HBV be cultivated in vitro?
No, HBV is not cultivable in vitro
Early in the course of disease, during acute infection
IgM anti-HBcAg
The patient is in convalescence or previously vaccinated and has developed immunity
anti-HBsAg
High infectivity and a chronic carrier state
HBeAg
What is the best indication of active viral replication and high infectivity in HBV?
Presence of HBV DNA in the serum
What molecular test can detect HBV DNA?
PCR (Polymerase Chain Reaction)
Old infection is present
IgG anti-HBcAg
Low infectivity
anti-HBeAg
Describes whether the patient is diseased or immune
Surface antigen
Tells us how long the infection has been present
Core antigen
What autoimmune condition is associated with HBV?
Autoimmune vasculitides (polyarteritis nodosa)
What are common symptoms of HBV infection?
Fever, anorexia, and jaundice
What are some signs of HBV infection in bodily fluids?
Dark urine and pale feces
What lab findings are elevated in HBV infection?
Elevated transaminase levels
What serious liver conditions can chronic HBV infection lead to?
Cirrhosis and hepatocellular carcinoma
What is the significance of the HBV vaccine?
It is the first vaccine to prevent human cancer
Small, nonenveloped, circular, double-stranded DNA viruses
Polyomavirus
Which are the first human viruses identified in the Polyomaviridae family?
JC and BK virus
When do infections with JC and BK viruses usually occur, and what is their clinical significance?
Infections usually occur during childhood and have little clinical significance
What disease does JC virus reactivation cause?
Disease in the central nervous system (CNS)
What condition does BK virus cause?
Hemorrhagic cystitis
Name other viruses in the Polyomaviridae family.
KI virus, MC virus, and WU virus
What type of cancer is associated with MC virus?
Merkel cell carcinoma
What methods are used to detect JC virus?
-PCR of CSF samples,
-immunohistochemistry,
- electron microscopy of brain tissue
How is BK virus detected?
PCR or cytologic examination of the urine
