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April 8 (Thurs) ID, Week 1 Lectures
Virology I - Imperiale; Influenza & other resp viruses - Miller
22
Medical
Graduate
04/09/2010

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Cards

Term
What is the mechanism by which enveloped viruses that get into host cells via receptor-mediated endocytosis, eventually get into the cytoplasm?
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
Term
What is the result of the conformational change that takes place in pH independent enveloped viruses to trigger membrane fusion?
Definition
-exposure of hydrophobic residues facilitates fusion
Term
What is tropism?
Definition
differential ability of virus to successfully infect a given cell
Term
What are some major determinants of tropism?
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?
Term
What steps does a negative strand RNA virus need to undergo to get to protein synthesis?
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)
Term
What additional "machinery" does a negative stranded RNA need to carry with it when it infects cells?
Definition
-brings its own viral RNA polymerase so it can transcribe a + RNA
Term
What is the effect of using IRES?
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.
Term
How does antigenic shift occur? What is the consequence?
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
Term
What kind of immunity is boosted with live, attenuated virus? How is this achieved?
Definition
-improves cell-mediated immunity: exposes T cells to weak form of virus, allows for production of memory cells for future infection
Term
What type of immunity is boosted by a killed vaccine like the classic influenza or polio (Salk) vaccines?
Definition
-boosts antibody response; not very good at boosting cell-mediate response
Term
what are the major respiratory viruses?
Definition
-influenza (orthomyxoviridae)
-rhinovirus (picornaviridae)
-respiratory synctial virus (RSV; paramyxoviridae)
-coronaviruses
-adenoviruses
Term
which of the following respiratory viruses are enveloped: influenza, rhinovirus, respiratory synctial virus, coronaviruses, adenoviruses
Definition
-influenza
-RSV
-coronaviruses
Term
What are the 3 surface proteins on the influenza A virus that are major targets for antimicrobial drugs?
Definition
-hemagglutinin (HA) -neuraminidase (NA) -ion channel (M2)
Term
What function of neuraminidase (NA) is targeted for inhibition by NA-inhibitors (oseltamivir, zanamivir)?
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

Term
What is the role of the immune response in infuenza A infections?
Definition
primarily protective, as opposed to pathogenic
-induces virus and type specific immunity
Term
what is the role of the influenza A's NS1 protein?
Definition
host immune suppression
Term
which of the influenza types undergo antigenic drift? which undergo antigenic shift?
Definition
-all: A, B, C
-just type A
Term
What mechanism do rhinoviruses use to encode many proteins in its non-segmented RNA genome?
Definition
-polyprotein genome: translate genome as one large protein that is then cleaved at specific points to create many proteins
Term
what are the clinical manifestations of rhinovirus infection?
Definition
-rhinorrhea, sore throat, minimal cough, low grade fever; generally mild
Term
What is bronchiolitis? What causes it?
Definition
-bronchiole obstruction with mucus and necrotic cells
-this is hallmark of *RSV*
Term
What is the function and significance of the F protein on RSV?
Definition
-fxn: promotes virus-cell and cell-cell fusion
-significance: candidate for vaccine target; target for palivizumab (preventive monoclonal antibody)
Term
What kind of genomes do adenoviruses have?
Definition
DNA
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