virology Flashcards
size range of viruses
18 nm to 300 nm
families of DNA viruses (7)
1) poxviridae: smallpox virus, monkeypox virus
2) herpesviridae: herpes simplex virus (types 1 and 2), epstein-barr virus, cytomegalo virus, human herpes virus 6,7,8
3) adenoviridae - adenovirus
4) hepadnaviridae - hep B virus
5) polyoma viridae - BK virus
6) papilloma viridae - papilloma virus
7) parvoviridae - parovirus B19
capsids
protein; environmentally stable to temperature, acid, proteases, detergents drying; release from cell by lysis;
consequences: can be spread easily, can dry out and retain infectivity; can survive the adverse acidic conditions of the gut; antibody may be sufficient for immunoprotection
enveloped virus
membrane; lipid; proteinl glycoproteins
environmentally labile - is disrupted by acid, detergents, drying, heat; modifies cell membrane during replication; is released by budding and cell lysis
consequences: must stay wet; cannot survive the gastrointestinal tract; spreads in large droplets, secretions; does not need to kill the cell to spread; may need antibody and cell-mediated immune response for protection and control; elicits hypersensitivity and inflammation to cause immunopathogenesis
how do hemagglutin glycoprotein trimers of influenza virus help in the rapid infection of various human cell types?
sialic acid binding domain - attachment region of influenza virus binds to sialic acid domains expressed in various types of cells; this facilitates the binding of influenza with several cell types
how does the antibody molecules, nucleoside analogues and protease inhibitors help combat the spread of an infecting virus?
antibody - before entering the cell binds to viral proteins
nucleoside analogs - inhibit the replication, DNA synthesis
protease inhibitors - inhibit assembly of virus from a polyprotein segment
families of RNA viruses
1) paramyxoviridae - measles virus, mumps, virus, metapneumovirus
2) orthomyxoviridae - influenze virus types A, B, C
3) coronaviridae - coronavirus, SARS
4) rhabdoviridae - rabies virus
5) retrovirdiae - human T-cell leukemia virus types I and II< HIV
6) picornaviridae - poliovirus, hep A
7) togaviridae - rubella virus
8) flaviviridae - yellow fever virus, west nile virus, hep C
DNA viruses
DNA is not transient or labile
viral genomes remain in the infected cell
many DNA viruses establish persistent infecitons
DNA genomes reside in the nucleus
viral genome resembles host DNA for transcription and replication
viral genes must interact with host transcriptional machinery (except for pox viruses)
viral gene transcription is temporarily regulated (early genes and late genes)
RNA viruses
RNA is labile and transient replicate in the cytoplasm cells cannot replicate RNA RNA viruses must encode an RNA dependent RNA polymerase prone to mutation
what are the probes as well as the material being tested during in situ hybridization?
DNA probes can be used to detect specific genetic sequences in biopsy specimens
what are the probes as well as the material being tested during northern blot?
DNA probe hybridization of RNA electrophoretically separated and blotted onto a nitrocellulose filter
what are the probes as well as the material being tested during southern blot?
DNA probe hybridization of DNA separated in gel electrophoresis and transferred onto a nitrocellulose paper
what are the probes as well as the material being tested during western blot hybridizations?
electropohoretically separated proteins can be identified using antibodies
what are the probes as well as the material being tested during PCR?
Amplified single copies of viral DNA millions of times over; can be used to detect even few viruses lying dormant in infected cells; most sensitive, recent and preffered method to detect a few DNA molecules
what are the probes as well as the material being tested during RT-PCR?
involves the use of revere transcriptase enzyme of retroviruses; viral RNAs are first converted to DNA by reverse transcriptase enzyme and then PCR amplified
Prodrome
non specific early symptoms
Tropism
a particular disease caused by several viruses that have a common tissue preference - hepatitis (liver), common cold (upper respiratory tract)
Viremia
presence of virus in the blood circulation
What are acyclovir and AZT? How do they influence the viral spread?
Acyclovir is a nucleoside analogues inhibit viral DNA polymerase selectively and there by inhibit viral DNA polymerase selectively and thereby inhibit viral replication
AZT was originally developed as anticancer drug. It si 100 fold more sensitive to viral reverse transcriptase than to the host cell DNA polymerase. AZT is the first useful therapy for HIV infection
some viruses do not cause any cytopathological effects (CPE) on tissues. How can these viruses be detected and identified?
cells infected with influenze virus, parainfluenza virus, mumps virus and togavirus do not exhibit classic CPEs; these cells expressive viral glycoprotein - hemagglutinin can bind to erythrocytes (hemadsorption) of a given species and cause hemagglutination; antibodies against specific viruses can prevent the hemagglutination caused by that specific viruses (against which the antibodies have been raised); this demonstration of hemagglutination and inhibition of hemagglutination is a major tool to detect and identify a specific virus without a CPE
What is a PFU?
plaque forming units
viruses can be quantitated by determining the greatest dilution that retains the following titers: TCD50, LD50, ID50
TCD50
tissue culture dose - titer of virus that cause cytopathologic effects in half the tissue
LD50
lethal dose; titer of virus that kills 50% of a set of test animals
ID50
infectious dose; titer of virus that initiates a detectable symptom, antibody or other response in 50% of a set of test animals
What are the methods of viral transformation and immortalization
viruses can cause cancer of the infected cells; this is achieved by removal of growth suppressors in host cells and enhancement of growth activators
What are the methods of viral transformation and immortalization
viruses can cause cancer of the infected cells; this is achieved by removal of growth suppressors in host cells and enhancement of growth activators
Why is HIV one of the deadliest viruses?
causes antigenic drift which helps the virus to escape the immune system; virus has tropism for CD4 expressing T cells and macrophages; can travel to lymph nodes and get in contact with CD 4 T cells
Gp120, Gp 41 and chemokine receptors: where are they located and what are their roles
they help the virus bind to the CD4 receptor; chemokine receptors (CXCR4) facilitate the binding and bring them closer to each other; enveloped spherical virion loses its envelope upon entering the cell; first a negative strand of DNA is synthesized by reverse transcriptase
poxviridae
smallpox virus, monkeypox virus
herpesviridae
herpes simplex virus (types 1 and 2), epstein-barr virus, cytomegalo virus, human herpes virus 6,7,8
adenoviridae
adenovirus
hepadnaviridae
hep B virus
polyoma viridae
BK virus
papilloma viridae
papilloma virus
parvoviridae
parovirus B19
paramyxoviridae
- measles virus, mumps, virus, metapneumovirus
orthomyxoviridae
influenze virus types A, B, C
coronaviridae
coronavirus, SARS
rhabdoviridae
rabies virus
retrovirdiae
human T-cell leukemia virus types I and II< HIV
picornaviridae
poliovirus, hep A
togaviridae
rubella virus
flaviviridae
yellow fever virus, west nile virus, hep C
how does herpes virus manage to stay latent after infecting a human being?
trigeminal ganglia
distinguish between HSV1 and HSV2 in terms of the tergion of infection in a human body.
HSV-1 causes syndromes mainly in the upper part of the body
HSV-2 causes syndromes in the genital area
what are the diseases caused by HSV1, HSV2, HSV3, and HSV4?
HSV1 or HSV2 can cause primary herpes gingiovostamatitis
HSV3 - vericella-zoster virus - chicken pox/ shingles
HSV4 - epstein-barr virus
what organs of a human body are infected by varicella (HSV3) virus during primary and secondary viremia?
primary viremia - viral replication in the regional lymph nodes
secondary viremia - virla replicationin the spleen, liver, and other organs –> infection of skin and appearance of vesicular rash
after infecting a human being, varicella virus goes through the stages of incubation, primary viremia and secondary viremia. At what stage of infection the virus becomes contagious and cause fever?
secondary viremia - day 10
Zanamavir, Oseltamivir, Amatadine and Rimantadine have antiviral effect. How do they bring about this inhibitory effect on influenza A virus infeciton.
zanamavir and oseltamivir inhibit neuraminidase of influenza A and B
amantadine and rimantadine inhibit uncoating step in influenza A infection
Herpes infection causes the following diseases: herpes zoster, herpes labialis, herpes whitlow and herpes gladiatorium. Which of these diseases occurs in nurses and physicians attending patients with HSV INFECTION?
Herpes whitlow occurs in nurses and physicians attending patients with HSV infections
which one of the influenza viruses can cause pandemics? what organ systems are affected by this virus infection?
influenza A
describe the structure of influenza virus A, B, and C with respect to envelop and genetic material.
influenza A, B, and C are enveloped and have a negative sense RNA genome
name the viruses that can cause cervical cancer
papillomaviruses and polyomaviruses
names the virus that can cause kerantinization of epithelial cells
papillomavirus
name the virus that causes molluscum contagiosum
poxviruses
name the virus that causes small pox
poxviruses
describe the method by which live vaccinia virus with recombinant DNA can be produced. Why this vaccination was discontinued?
vaccinia live form vaccination was abandoned due to fatalities caused in spite of being effective against small pox; altered vaccinia is being used as expression vector
describe conjunctivitis
caused by adenovirus
describe molluscum contagiosum
infection by pox virus contianing double stranded linear DNA genome which replicates in cytoplasm; lesions nodular to wartlike; contains pearl-like umbilicated nodule; nodule has a central casious plug that can be squeeze out
describe erythema infectiosum
caused by parovirus B19; infected children have flu like illness (fever, muscle pain, tired); after a few days of flu suddently develops an intensely red rashon cheeks and trunk
which is the largest and most complex of all the viruses
pox viruses - contain linear double stranded genome; DNA viruses replicate in the cytoplasm; include human viruses variola (small pox) and molluscum contagiosum
explain the following with a mention of the associated viruses
a. dead and infection
b. herpangina
c. hand-foot and mouth disease
d. genetic assortment
e. epidemic
f. pandemic
dead end infection - alphavirus and flavivirus - no transmission of the virus back to the vector
describe the genome and the characteristic features of corona virus and rhino virus
corona virus - enveloped virus; contains long positive RNA genome; early phase of translation - RNA dependent RNA pol; late phase - produce structural and non structural proteins
what are the symptom and diseases resulting from the infection of coxsackie virus
infectious disease in children; characterized by a sunnder occurence of fever, loss of appetite, inflammation and ulceration of throat; distinct vesicles on the palate
vesicular lesions on the hands, feet, mouth and tongue; first develops in the oral cavity; within one day spreads to other parts
what are the symptom and diseases resulting from the infection of paramyxovirus
measles, mumps, and parainfluenza virus; virus induce cell-cell fusion causing multinucleated giant cells; transmitted in respiratory droplets and initiate in the respiratory tract; cell-mediated immunity causes may of the symptoms but essential for control of the infection
what are the symptom and diseases resulting from the infection of alpha virus
DHF - deng hemorrhagic fever (loss of fluids from vasculature)
DSS - deng shock syndrome
what are the symptom and diseases resulting from the infection of rubella virus
rubella enters and infects the nasopharynx and lung; spreads to the lymph nodes and monocyte macrophage system; circulating antibody can block the transfer of the virus; immunologically deficient pregnant woman, the virus can infect the placenta and spread to the fetus; can cause serious congenital abnormalities in the chidl
what are the symptom and diseases resulting from the infection of corona virus
second most prevalent cause of the common cold; prefers to prolerate in upper respiratory tract; in 2002, SARS (atypical pneumona characterized by high fever, chills, headache, dizziness, myalgia and breathing difficulty; symptoms develop within 10 days of exposure to person or place associated with SARS; infected human beins from animals)
which virus is being used for vaccination as a live attenuated form?
paramyxovirus
name the virus that gets transmitted through arthropods
togaviruses (alpha viruses, rubiviruses)
flaviviruses (west nile virus)
arbovirus (alpha virus and flavivirus)
