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55 Cards in this Set
- Front
- Back
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What is the name for a viral infection that occurs relatively rapidly with lysis of infected cells and finally eradiction from the body?
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Acute viral infection.
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What type of viral infection is characterized by long lasting infection with production of intact viral particles?
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Chronic (Persistent) viral infection.
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What type of viral infection is characterized by an initial infection that is followed by periods of time when intact viruses can not be found and by periods when symptoms flare-up and viral particles can be detected?
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Latent viral infection.
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What characterizes the ability to detect slow viruses or prions during the course of infection?
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Both gradually increase in quantity over many years after infection and prior to development of symptoms of disease.
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List four ways that viruses can evade the host’s immune system.
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1) Restricted gene expression. 2) Become inaccessible to the immune response-latency. 3)Decrease expression of MHC or adhesion expression on host cells. 4)Produce homologues of cytokines that are immunosuppressive – such as IL-10.
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What should you do when considering ordering laboratory tests for the detection of viral infection?
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Check in the local environment to see what is available.
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What is the best specimen to collect for upper respiratory virus infections?
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Nasopharyngeal swab or lavage.
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What is an important step to take to ensure that a good viral specimen arrives in the diagnostic laboratory?
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Put the specimen in transport medium and keep it cold.
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Why is virus culture with the identification of CPE not very useful in clinical medicine?
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It takes too long.
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What does CPE mean?
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Cytopathic effect. Changes in cultured cells that occur due to virus infection.
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Why do red blood cells adhere to cells (hemagglutination) infected by some viruses?
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The viruses expresses a hemagglutinin that is expressed on the surface of the infected cell.
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What technique can be used to make virus culture faster and therefore more clinically useful?
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The Shell Vial Technique. It detects early antigen expression in infected cells which are usually present after overnight incubation.
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What is the primary serologic assay used for virus diagnosis?
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ELISA
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Do ELISA assays detect virus antigen or antibodies specific to the virus?
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Either can be detected. It depends on how the assay is constructed.
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When is electron microscopy used in the clinical diagnosis of virus infections?
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For some of the enteric virus infections such as with the Norwalk agent.
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What assay is rapidly becoming the “gold standard” for detection of viruses in clinical specimens?
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PCR or RT-PCR.
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What is the primary limitation of PCR techniques?
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They are usually qualitative to semi-quantitative.
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What new PCR technique is quantitative?
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Real-time PCR.
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What is the mode of action of Amantadine?
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Inhibits virus uncoating.
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For what viral disease is amantadine prescribed?
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Influenza A (not effective against Influenza B or influenza C).
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What is the mode of action of Relenza and Tamiflu?
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Both inhibit the neuraminidase of the influenza virus and prevent it’s spread from cell to cell.
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What is the mechanism of action of acyclovir?
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Acyclovir is phosphorylated by a virus encoded thymidine kinase and subsequently further phosphorylated by host cell enzymes. The ACV-triphosphate replaces dGTP in DNA causing chain termination.
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What viral agents are treated with acyclovir?
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Herpes Simplex virus-1, Herpes Simplex virus-2 and the varicella-zoster virus (VZV).
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What virus is treated with ganciclovir?
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Cytomegalovirus (CMV)
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What is the mode of action of the nucleoside inhibitors used in the treatment of HIV infection?
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They inhibit DNA synthesis from the RNA genome of the virus by their action on the reverse transcriptase of the virus. They are competitive inhibitors of reverse transcriptase.
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What is the mode of action of the non-nucleoside inhibitors used for the treatment of HIV infection?
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They induce a conformational change in the reverse transcriptase enzyme of the virus that inhibits its activity.
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What do the protease inhibitors used in the treatment of HIV infection do?
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They inhibit the viral protease from cleaving polyproteins of the virus into proteins.
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What is the basis of HAART therapy?
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Use of two reverse transcriptase inhibitors and one protease inhibitor for the treatment of HIV infection.
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What conditions are treated with ribavirin?
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Severe RSV infection. Severe influenza B infection. In conjugation with interferon-alpha to treat hepatitis C.
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What is the mode of action of interferon-alpha?
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It induces enzymes in cells adjacent to viral-infected cells that inhibit translation of viral mRNA into protein.
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What is the most important characteristic of the herpesviruses?
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They can establish latent infection and persist for life.
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What are the general features-size and DNA-of the herpesviruses?
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Large with a dsDNA genome.
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What are the three waves associated with replication of herpesviruses and what is synthesized during each wave?
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Alpha-immediate early genes and proteins. Beta-early genes and proteins. Gamma-late genes and proteins that assemble into the capsid.
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Where does herpes simplex virus (HSV) establish latency?
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Nuclei of the sensory ganglion.
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When HSV reactivates where does it go?
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It moves to a site at or near the portal of entry.
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In what socioeconomic group are more herpes infections found?
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Lower socioeconomic.
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How many adults are infected with HSV worldwide?
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60-90 percent.
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What correlates with infection with genital herpex?
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The number of lifetime sexual partners.
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What is characteristic about the pathology of HSV infection?
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Formation of multinucleated giant cells. Vesicular lesions containing large quantities of virus.
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Where does HSV-1 infection usually occur and what ganglion is colonized?
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Infection of the oropharyngeal mucosa. Trigeminal ganglion colonized.
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How is HSV-2 usually transmitted and which ganglion is colonized?
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Sexual contact. Sacral ganglia.
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How does HSV-1 inhibit host responses?
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1) Inhibition of MHC expression. 2) Inhibition of IFN-induced antiviral cascade. 3) Presence of pseudo-Fc receptors. 4) Inhibition of apoptosis of infected cells. 5) Dormancy in neurons.
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At what age do most primary infections with HSV-1 occur?
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In children between 1-2 years of age.
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Who transmits HSV to newborns?
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Nursery personnel and mothers.
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Where do recurrent HSV-1 infections occur?
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At the vermillion border of the lip.
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What are the clinical findings in primary genital (HSV-2) infection?
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Macules and papules followed by vesicles, pustules and ulcers.
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What are the most common complications associated with HSV-2 infections?
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Meningitis and extragenital lesions.
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Does the presence of anti-HSV-1 antibodies affect the severity of HSV-2 infection?
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Yes, it can ameliorate the infection but does not protect the individual.
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What three routes of infection with HSV occur in neonates?
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In utero. Intrapartum contact (most by this route). Post-natal acquisition – nursing or transmission vial oral lesions.
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What are the consequences of neonatal herpes infection?
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It is symptomatic and frequently fatal.
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Name three different infections found in herpes-infected babies?
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Infection of the skin, eye and mouth. Encephalitis with or without skin involvement. Dissemination.
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What type of skin infection with HSV is common among health care workers?
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Herpetic whitlow.
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Who is at increased risk following herpes infection?
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The immunosuppressed.
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What is the method of choice for diagnosis of herpes infections?
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PCR.
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What is used in the treatment of HSV infection?
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Acyclovir
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