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VET 413: Infectious Disease/Immunology > Virology II > Flashcards

Virology II Flashcards

1
Q

replication curve

A

initial latent period followed by exponential growth

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2
Q

what occurs during the latent period

A

producing early enzymes, nucleic acids, and protein coat

NO production of infectious virus from cells

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3
Q

when during the replication curve are structural components of the virus produced

A

end of replication curve –> exponential growth

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4
Q

what are the steps of the replication cycle

A
  1. attachment
  2. entry
  3. uncoating
  4. replication
  5. assembly
  6. release
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5
Q

replication cycle for an enveloped DNA virus

A
  1. virus envelope binds to receptors on host cell
  2. envelope fuses w/ plasma membrane so only encapsidated virus enters
  3. viral genome (DNA) exits from the capsid and enters the nucleus via a nuclear pore than circularizes inside the nucleus
  4. transcription and translation of early proteins produces transcription factors that promote synthesis of late proteins; late proteins encode the capsid and envelope
  5. genome gets enclosed into the capsid at the inner leaflet of the nuclear membrane
  6. assembled virus buds off of the nuclear membrane to form a vesicle; vesicle fuses with outer cell membrane to exocytose out of the cell in a lipid envelope
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6
Q

how do antiviral drugs work

A

target any stage of the replication cycle

  • helicase/primase inhibitors
  • nucleoside analogs
  • protease inhibitors
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7
Q

replication cycle for an enveloped RNA virus

A
  1. virus envelope binds to receptors on host cell
  2. entire virus gets engulfed into the cell –> forms endosome –> drop in pH triggers fusion of viral envelope with endosome membrane
  3. viral genome (RNA) exits from the capsid and enters the cytoplasm
  4. RNA viral genome acts as a template for complementary RNA strands via RNA polymerase –> new copies of viral genome are made
    - comp. RNA strands also act as mRNA –> gets translated into capsid proteins in the cytoplasm and envelope glycoproteins in ER/golgi
  5. capsid assembles around each new copy of the viral genome in cytoplasm; vesicles transport the envelope glycoproteins from golgi then fuse with outer cell membrane to present glycoproteins on cell surface
  6. capsidated virus buds off of the outer membrane, forming the envelope surrounded by glycoproteins
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8
Q

attachment

A

interactions between virus and cell surface proteins/carbohydrates

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9
Q

how do viruses find host cells

A

viruses are free floating - must encounter host cells that express the correct receptors

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10
Q

what determines specificity of virus binding to host cells

A

host cells must express the correct receptors in order to be infected by viruses

receptors determine tropism for certain tissues within certain hosts

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11
Q

adhesion vs entry receptors

A

adhesion: initial binding between virus envelope and host cell; loose adhesion

entry: final binding between virus envelope and host cells; tight adhesion

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12
Q

entry and uncoating

A

breaching the plasma membrane and releasing the genome

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13
Q

mechanisms of entry and uncoating

A
  1. direct penetration
  2. membrane fusion
  3. endocytosis
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14
Q

direct penetration

A

capsid does not enter the cell

injects viral genome directly into the cell

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15
Q

membrane fusion

A

envelope attaches and fuses to release capsid into cytoplasm

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16
Q

endocytosis

A

entire envelope and capsid gets engulfed into the cell

many different pathways exist

17
Q

replication

A

producing more viral genomes

STRATEGY: depends on viral genomic acid and its polarity

LOCATION: depends on genomic nucleic acids (DNA vs RNA)

18
Q

where do DNA viruses replicate

A

nucleus

19
Q

where do RNA viruses replicate

A

cytoplasm

20
Q

positive sense RNA replication

A

looks like mRNA –> can be directly translated into viral proteins

does not require virus to have its own RNA polymerase

21
Q

negative sense RNA replication

A

opposite direction than mRNA –> must be transcribed by RNA polymerase into a positive sense strand before translation can occur

virus must have its own RNA polymerase attached

22
Q

assembly and release

A

newly synthesized genomes assemble into new viruses and get released

23
Q

where do DNA vs RNA viruses assemble and release

A

DNA: nucleus
RNA: cytoplasm

24
Q

how are enveloped viruses released

A

budding off of the cell - takes components of the outer cell membrane with it to form envelope

can occur on different sides of the cell to allow for systemic spread or viral secretions

25
Q

how are encapsidated viruses released

A

lysis of the cell

can not bud off because does not have an envelope made of membrane components

26
Q

physical viral assays

A

measure the presence of virus structure, antigen, or genome

  • hemagglutination assay
  • hemagglutination inhibition
  • ELISA
  • PCR
27
Q

hemagglutination assay

A

determines presence of viral antigen

combine sample + RBCs in a well
- if antigen present –> virus will agglutinate the RBCs together to make solution diffusely pink
- if no antigen present –> lack of virus will cause RBCs to clump and sink to the bottom

28
Q

hemagglutination inhibition

A

determines presence of viral antibody

combine virus + RBCs + sample in a well
- if antibody present –> will bind virus and prevent agglutination causing RBCs to clump and sink to the bottom
- if no antibody present –> virus will agglutinate and well becomes diffuse pink

29
Q

ELISA

A

determines presence of viral antigen

sample + known antibody to see if antibody binds to antigen in sample

sandwich method vs non sandwich

30
Q

PCR

A

determines presence of viral nucleic acid

replication of viral genome within patient sample

early fluorescence indicates higher concentration of viral genome in the sample

31
Q

biological viral assays

A

measures how infectious the virus is

  • culture and cytopathic effects
  • plaque assays
32
Q

culture and cytopathic effects

A

determines if a virus is infectious

inoculating virus within the cell line and determining the reaction

33
Q

plaque assay

A

determines how much infectious virus there is

measures plaque forming units per volume of sample tested

VET 413: Infectious Disease/Immunology (38 decks)

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