Term
| What is the mechanism by which enveloped viruses that get into host cells via receptor-mediated endocytosis, eventually get into the cytoplasm? |
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Definition
-use a pH dependent mechanism
-vesicles acidify as they move toward golgi; trigger membrane fusion. Viral envelope fuses with vesicle membrane and releases viral nucleocapsid into cytoplasm of host cell.
-in influenza A, M2 protein acts as ion channel to help virus monitor pH in vesicle |
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Term
| What is the result of the conformational change that takes place in pH independent enveloped viruses to trigger membrane fusion? |
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Definition
| -exposure of hydrophobic residues facilitates fusion |
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Term
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Definition
| differential ability of virus to successfully infect a given cell |
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Term
| What are some major determinants of tropism? |
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Definition
-host species (some viruses are more species specific than others)
-receptors - viruses need to bind receptors on host cell surface to infect cells
-intracellular environment: does the cell support the activities the virus needs to replicate and survive? |
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Term
| What steps does a negative strand RNA virus need to undergo to get to protein synthesis? |
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Definition
-needs to first make a + strand (+ strand RNA = mRNA and can be directly translated)
-uses 5' end of host cell mRNA's as primers to start translation of viral mRNA (+ RNA) |
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Term
| What additional "machinery" does a negative stranded RNA need to carry with it when it infects cells? |
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Definition
| -brings its own viral RNA polymerase so it can transcribe a + RNA |
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Term
| What is the effect of using IRES? |
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Definition
| IRES are internal translation initiation sites that allow multiple proteins to be translated from one nucleic acid segment. Allows translation of multiple reading frames. |
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Term
| How does antigenic shift occur? What is the consequence? |
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Definition
-when a cell is infected with 2 strains of a virus, there can be reassortment of viral genes = antigenic shift
-can lead to new strains of a virus |
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Term
| What kind of immunity is boosted with live, attenuated virus? How is this achieved? |
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Definition
| -improves cell-mediated immunity: exposes T cells to weak form of virus, allows for production of memory cells for future infection |
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Term
| What type of immunity is boosted by a killed vaccine like the classic influenza or polio (Salk) vaccines? |
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Definition
| -boosts antibody response; not very good at boosting cell-mediate response |
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Term
| what are the major respiratory viruses? |
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Definition
-influenza (orthomyxoviridae)
-rhinovirus (picornaviridae)
-respiratory synctial virus (RSV; paramyxoviridae)
-coronaviruses
-adenoviruses |
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Term
| which of the following respiratory viruses are enveloped: influenza, rhinovirus, respiratory synctial virus, coronaviruses, adenoviruses |
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Definition
-influenza
-RSV
-coronaviruses |
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Term
| What are the 3 surface proteins on the influenza A virus that are major targets for antimicrobial drugs? |
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Definition
| -hemagglutinin (HA) -neuraminidase (NA) -ion channel (M2) |
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Term
| What function of neuraminidase (NA) is targeted for inhibition by NA-inhibitors (oseltamivir, zanamivir)? |
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Definition
-release of newly formed virions; inhibits viral proliferation
-NA cleaves sialic acid residues, allowing newly formed virions to be released from the plasma membrane of the host cell where it is budding |
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Term
| What is the role of the immune response in infuenza A infections? |
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Definition
primarily protective, as opposed to pathogenic
-induces virus and type specific immunity |
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Term
| what is the role of the influenza A's NS1 protein? |
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Definition
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Term
| which of the influenza types undergo antigenic drift? which undergo antigenic shift? |
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Definition
-all: A, B, C
-just type A |
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Term
| What mechanism do rhinoviruses use to encode many proteins in its non-segmented RNA genome? |
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Definition
| -polyprotein genome: translate genome as one large protein that is then cleaved at specific points to create many proteins |
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Term
| what are the clinical manifestations of rhinovirus infection? |
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Definition
| -rhinorrhea, sore throat, minimal cough, low grade fever; generally mild |
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Term
| What is bronchiolitis? What causes it? |
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Definition
-bronchiole obstruction with mucus and necrotic cells
-this is hallmark of *RSV* |
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Term
| What is the function and significance of the F protein on RSV? |
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Definition
-fxn: promotes virus-cell and cell-cell fusion
-significance: candidate for vaccine target; target for palivizumab (preventive monoclonal antibody) |
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Term
| What kind of genomes do adenoviruses have? |
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Definition
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