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36 Cards in this Set
- Front
- Back
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What viruses are orthomyxoviridae?
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Influenza A, B, and C
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Describe the features of the influenza virus?
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Spherical
8 segments of (-) RNA Helical symmetry capsid Glycoproteins anchored by M-proteins |
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What are the two glycoproteins of influenza?
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HA and NA
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What is the mechanism of influenza HA?
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Can attach to host sialic acid receptors. HA binding to these receptors activates fusion of the host cell membrane with the virion membrane.
HA needed for absorption. Antibodies bind HA and block activity. |
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What is the mechanism of influenza NA?
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Cleaves neuraminic acid and disrupts the mucin barrier, exposing the sialic acid binding sites on the cell surface. Neuraminidase also cleaves the sialic acid receptor to allow the formed virion to escape and infect a new cell.
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Describe influenza antigenic drift.
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During viral replication, mutations can occur in the HA/NA, leading to changes in the antigenic nature of the glycoproteins. New strains are only partially attacked by the immune system, causing mild disease.
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Describe influenza antigenic shift.
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Antigenic shift causes complete change of the HA/NA or both. Will only occur with influenza type A because the mechanism involves RNA exchange between animal and human strains. When a cell is co-infected, RNA can be mispackaged into another virus. The new virus has never been exposed to the human immune system.
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What influenza groups are responsible for human disease? Which can infect animals? Which is found only in humans?
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A and B are responsible for human disease
A can infect animals B and C are only found in humans |
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What influenze groups are associated with endemics? Which are associated with pandemics?
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Group B: endemics
Group A: pandemics |
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What influenza type undergoes antigenic shift and drift?
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Type A
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Is influenza enveloped?
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Yes
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Type B will only undergo antigenic drift, why?
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It cannot undergo antigenic shift because it has no animal reservoir.
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Where does influenze replication occur?
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In the nucleus, with partial assembly in the cytoplasm
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What is the most important antibody in controlling influenza?
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IgA
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Describe the period of time influenza is shed by the patient?
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up to 2 days prior to symptoms, and up to 4-5 days after onset of symptoms
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What is the reservoir for all HA and NA subtypes?
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Aquatic birds
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What is Reye's syndrome?
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Children given aspirin when they have influenza or varicella can develop a severe liver and brain disease.
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What is the peak month of influenza activity?
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February
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Why is H1N1 more likely to cause serious disease (think tropism, not serology)?
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More likely to infect the lower respiratory tract
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What are the two licensed anti-influenza drugs?
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M2 blockers (adamantanes)
NA inhibitors |
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What are the NA inhibitors?
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Oseltamivir
Zanamivir |
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Influenza vaccines are trivalent, what are the components?
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A type: H3N2
A type: H1N1 B type |
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When can antivirals be used prophylatically for influenza?
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For people allergic to the vaccine and for periods before the vaccine takes effect
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Influenza vaccine is indicated for what population?
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Healthy persons 5-49 years of age
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What virus has caused the most deaths of any infectious disease?
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variola (poxvirus)
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When was small pox declared eradicated?
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1979
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Why can smallpox be used as a weapon?
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Can be produced in large quantities
Stable for storage Stable aerosol High mortality Highly infectious No immunity |
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Why was it possible to eradicate variola?
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Slow spread
Effective vaccine No animal vector No carrier state Infectious only with symptoms Prior infection gives immunity International coop |
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What are the strains of poxviridae family?
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Variola (major and minor)
Vaccinia Cowpox Monkeypox |
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Describe the pathogenesis of smallpox.
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Virus enters in respiratory or oral mucosa.
Macrophages carry it to regional nodes. 1` Viremia on day 3 Invades reticuloendothelial organs 2` Viremia on day 8 |
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Who developed the first smallpox vaccine?
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Jenner 1796: saw that milkmaids that got cowpox did not get smallpox.
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What are the means of vaccine administration for variola?
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Jet gun
Bifurcated needle: mainstay of WHO |
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What is vaccinia gangrenosum/necrosum?
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Lesion caused by vaccination of smallpox. Does not heal. Mortality is 100% if untreated.
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Discuss the use of vaccinia as a vaccine vector.
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1. large genome makes it a good candidate for insertion of foreign DNA (can express hepatitis and influenza proteins).
2. limited accepted use 3. multiple vaccinations not easy |
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What is the primary difference in replication between vaccinia and other DNA viruses?
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Poxviruses are DNA viruses that replicate in the cytoplasm.
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Why was the smallpox vaccine eliminated in the US prior to its eradication world wide?
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Serious complications associated with vaccine. Serious reactions to the vaccine exceeded the risk of infection in the developed world.
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