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72 Cards in this Set
- Front
- Back
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How does a virus directly damage a cell?
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(1) Effects of conscription of cell machiners (2) Toxic effects (3) Cell lysis
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What is the immune-mediated response to viral infection?
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Cytotoxic T lymphocyte attack
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Define incubation period
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Period of time between when an infectious agent gains entry and the appearance of the first signs or symptoms
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Factors which affect the incubation period
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(1) type of infection (2) clinical manifestations of infection
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Define viral tropism
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Propensity of virus to infject certain cell types
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What is the effect of viral tropism?
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Determines clinical manifestations of viral infection
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(1) Rhinovirus (2) HBV, HCV (3) Parvovirus B19 (4) HSV(a) Erythroid percursor (b) Nasal mucosal(c.) Hepatocytes (d) DRG neurons
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1-b, 2-c, 3-a, 4-d
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Rhinovirus ->
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upper respiratory tract infection; rhinitis
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HBV, HCV ->
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Hepatitis
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Parvovirus B19 ->
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Anemia
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HSV ->
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Recurrent skin infection in dermatome pattern
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What are the 4 direct methods of virus detection?
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(1) Histology/cytology (2) Culture (3) Antigen (4) Nucleic acid [PCR]
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What is histology/cytology?
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(1) Examination of infected cells in tissue, fluids (2) Viral cytopathic effect
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What is CPE?
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Viral cytopathic effect: (1) cellular damange (2) viral inclusions
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T/F CPE are always generalized damage
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False (CPE may be virus specific)
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CMV detection?
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check lung tissue (for aliens!)
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HSV detection?
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PAP smear
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Why do we culture?
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(1) viruses infect and replicate in mammalian cells (2) different virii have different tropism (3) infection causes cell damage (CPE)
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What methods are used in virus culture?
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(1) monolayers of cells inoculated with specimen (2) monolayers examined for CPE (3) flurescent staining to identify and confirm negatives
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Describe antigen detection
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Detection of viral antigens using specific antibody; solid, liquid, or membrane-based assay
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Describe DFA
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Direct fluorescent ntibody staining labels antibodies for direct detection of viral antigens
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Princile of rapid antigen tests
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Allows for rapid identification of virus-specific antigen in patient samples
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Rapid antigen testing method and use
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Immunochromatograpic membrane (plus a culture backup); Ised for rapid ID of RSV and influenza
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What is the RSV virus?
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Respiratory Syncytial Virus--respiratory tract infections (lower RTI)
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What is nucleic acid detection?
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Detection of viral nucleic acid (DNA, RNA) in patient specimens via PCR, etc.
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When is nucleic acid detection most utilized?
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Diagnosis of viral CNS, viral respiratory, (also other) infections
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How is nucleic acid detection used in prognosis and monitoring?
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Quantifies viral load (ex. HIV, HCV, CMV)
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Decribe serology
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Detection of virus specific antibodies in serum
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T/F Presence of IgM is indicative of a remote infection
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False (current or recent infection)
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T/F Presence of IgG takes time to develop
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TRUE
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What quantitative criteria is checked in serology testing?
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Detection of IgM or four-fold rise in IgG = infection
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Methods summary
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(1) lots of methods (2) none detect everything (3) each requires specific specimen types and handling
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What is the primary challenge in developing antiviral therapy?
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Virus is in the host cell likely using host cell machinery. How to target therapeutic agents to specifically target viral processes without undue toxicity to human cells
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T/F The stable nature of virii lead to ease in drug resistance development
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False (high replication and polymerase error rates -> rapid development of resistance in some virii)
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List poential agents for antiviral therapy
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(1) attachement (2) penetration, uncoating (3) viral polymerase (4) viral enzymes necessary for viral protein processing or packagaing
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T/F Antivirals are broad in range and activity
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False (some agents are highly virus specific with a single mechanizm of action
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Describe the influenza virus
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Enveloped, segmented, RNA virus (a,b) causes epidemic and pandemic respiratory infections; diagnosed via rapid antigen, DFA, culture
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What is a major chacteristic of influenza genotype?
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Antigenic shift and drift--may develop resistance (ex Avian flu)
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HSV
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Herpes simplex virus
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Descrbie HSV
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Enveloped DNA virus, neurotropic, high recurrence, may cause meningitis, encephalitis; diagnosed by PCR
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Define neurotropic
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Latent infection of dorsal root ganglia
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CMV
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Cytomegalovirus
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Describe CMV
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Enveloped DNA virus, latetent in leukocytes, self-limited, sever in immunocompromised
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What is diagnostic choice for CMV?
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CMV DNA PCR (viral load), antigenemia
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Define antigenemia
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Detection of infected leukocytes in blood by FA staining
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CMV drug treatments
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(1) ganciclovir (2) cidofovir (3) foscarnet
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Describe resistance in CMV
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Mutation in viral phosphotransferase (ganciclovir) or DNA polymerase genese (alll three)
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HCV
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Hepatitis C virus
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Describe HCV
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Enveloped RNA virus, hepatotropic, chronic hepatitis (may be clinically asymptomatic)
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Diagnosis of HCV
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Serology, RNA detection in plasma
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Pronosis for HCV
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Monitor quantitiative RNA in plasma (viral load), genotype determination
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HIV
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Human immunodeficiency Virus
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Describe HIV
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enveloped RNA virus, chronic infection in CD4+ T cells, immunodeficiency develops when destruction of CD4+ cells outstrips replenishment
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HIV diagnosis
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serology, RNA in plasma
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HIV monitoring
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Quantitiative HIV RNA in plasma (viral load)
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Characteristic of HIV virus
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viral RNA is reverse transcribed into DNA by reverse transcriptase (retrovirus)
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What is cause of chronic damange in HCV?
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Due to host inflammatory response to virally-infected cells
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HIV therapeutics
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NRTI, NNRTI, protease inhibitors, fusion inhibitors
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NRTI
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nucleoside reverse transcriptase inhibitors
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NNRTi
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non-nucleoside reverse transcriptase inhibitors
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Why does resistance develop quickly in HIV?
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Level of replication, error rate of HIB polymerase; detect by sequenceing RT and protease genes
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T/F HIV drugs are used in sequence to prevent development of resistance
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False (drug cocktails are multiple mixes of different antiviral agents)
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HAART
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Highly active retroviral therapy
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What is the smallest form of life?
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For this class, a virus
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What is the MO of a virus?
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Binds to and infects a host cell, co-opts host cell machinery to replicate and propagate itself
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Can a virus replicate outside of a host cell?
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NO
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What are the primary viral components?
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Nucleic acid, proteins (envelope, capsid, structural, other)
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What are the steps in viral host infection?
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1) Attachment 2) Penetration 3) Viral protein synthesis and replication 4) Viral assembly 5) Release
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List the types of viral infection
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1) Acute/lytic 2) Chronic active 3) Latent 4) multiple
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Describe acute viral infection
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Virus replicates within the cell. Cell lysis and death releases viral particles to infect other nearby cells.
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Describe chronic viral infection (non-retroviral)
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Virus replicates within the cell. Viral particles are released as they are produced by the cell which remains alive.
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Describe retroviral infection
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Viral genome is integreated into host DNA. Viral genome and proteins are transcribed/translated. May also be non-replicating (latent)
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