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Virology@RUSVM > Viral Replication > Flashcards

Viral Replication Flashcards

1
Q

permissive cell

A

a cell which a virus is able to replicate within

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2
Q

non-permissive cell

A

cells in which a factor or factors necessary to viral reproduction is not present or one detrimental to viral reproduction is present

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3
Q

MOI

A

number of virions that are added per cell during infection

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4
Q

adsorption

A

period in which the virus attaches to and enters the cell, and the titer of free virus in the medium may actually decline

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5
Q

eclipse period

A

time interval between uncoating (disappearance) and appearance, intracellularly, of first infectious progeny viruses. No infectious virus is detected during this time

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6
Q

latent period

A

time before new infectious virus appears in the medium, time from uncoating to just prior to the release of the first extracellular virions

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7
Q

burst size

A

number of infectious virions released per average cell

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8
Q

steps of viral replication (6 steps)

A

attachement, penetration, uncoating, synthesis of viral components, assembly and maturation, release in large numbers

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9
Q

attachment

A

binding of the virus to receptors on the host cell

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10
Q

endocytosis

A

a process in which a substance gains entry into a cell without passing through the cell membrane

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11
Q

most common form of endocytosis

A

receptor mediated endocytosis

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12
Q

types of receptor mediated endocytosis

A

clathrin-mediated endocytosis of virus by host
clathrin- and caveolin-independent endocytosis
caveolin-mediated endocytosis

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13
Q

how do enveloped viruses get out of the cell

A

fusion of virus membrane with host endosomal membrane releases viral genome. virus with glycoproteins bind to host membrane and fuse

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14
Q

how do non-enveloped viruses get out of the cell

A

lysis

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15
Q

ADCC

A

suface membrane fusion of enveloped viruses. viral glycoproteins are retained on the cell surface, and since these are antigenic, the cell can become a target of the host immune system

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16
Q

pH independent fusion proteins and examples

A

receptor binding, virus with host membrane fusion, release of viron contents into host cytoplasm
ex. HIV & Measles

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17
Q

pH dependent fusion proteins and examples

A

endocytosis, acidification(low pH) of endosome, HA configuration changes, membrane fusion, RNA genome enters cytosol
ex. HA in Influenza

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18
Q

pore-mediated penetration

A

some non-enveloped viruses inject their genome into the host cytoplasm through creation of a pore in the host membrane

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19
Q

antibody mediated attachment and penetration

A

antibodies against spike proteins of FIP cannot clear the virus from host. Rather these antibodies bind to FIP virus spike proteins and facilitate entry of viruses into host cells via antibody Fc receptor
ex. FIP- in macrophages

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20
Q

uncoating within endosome (enveloped viruses)

A

low pH in endosome promotes fusion of envelope with endosomal membrane; lysis of nucleocapsid by lysosomal proteases

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21
Q

uncoating at the nuclear membrane (4 ways)

A

1-pass directly through nuclear pores
2-attach to nuclear pore complex and release genome inside nucleus
3-wait for mitosis
4-genome released in nucleus and pass through pores

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22
Q

poliovirus uncoating

A

not completely uncoated until inside the cell

23
Q

poxvirus uncoating

A

complex series of steps involving both host and viral gene products

24
Q

retroviruses and reoviruses replication

A

first stages of viral replication cycle occurs inside the capsid

25
Q

replication of double-stranded DNA viral genome and production of viral mRNA

A

dsDNA–> (+)RNA –> viral protein

*dsDNA for progeny viruses

26
Q

replication of single-stranded DNA viral genome and production of viral mRNA

A

(+)ssDNA –> dsDNA intermediate –> (+)RNA –> viral protein

*(+)ssDNA for progeny

27
Q

replication of double-stranded RNA viral genome and production of viral mRNA

A

dsRNA –> (+)RNA –> viral proteins

*dsRNA for progeny

28
Q

replication of single-stranded (-)RNA viral genome and production of viral mRNA

A

(-)ssRNA –> (+)RNA –> viral proteins

*(+)ssRNA intermediate –> (-)ssRNA for progeny

29
Q

replication of a single-stranded (+)RNA viral genome and production of viral mRNA

A

(+)ssRNA –> (+)RNA –> viral protein
or
(+)ssRNA –> (-)ssRNA –> (+)ssRNA for progeny

30
Q

replication of single-stranded (+)RNA viral genome and production of viral mRNA by way of REVERSE TRANSCRIPTASE

A

(+)ssRNA –> (-)ssDNA –> dsDNA intermediate –> (+)RNA –> viral protein
or
dsDNA intermediate –> (+)ssRNA for progeny

31
Q

replication of double-stranded DNA viral genome and production of viral mRNA by way of REVERSE TRANSCRIPTASE

A

dsDNA –> (+)ssRNA –> (-)ssDNA –> dsDNA –> (+)RNA –> viral protein

32
Q

mRNA cannot be recognized until it has __________ & a ____________

A

cap & a tail

33
Q

capping

A

addition of 7-methylgluanosine to the 5’ end of RNA, binds to the mRNA ribosomes, mark mRNA as self

34
Q

how are caps synthesized (3ways)

A

1- synthesized by host cell enzymes (eg. Retrovirus, Adenovirus)
2- by viral enzymes (eg. Poxvirus, Reovirus)
3- cap snatching from host mRNA (eg. Influenza)

35
Q

addition of tail

A

3’ poly- adenylated tail, tail interacts with poly-A binding proteins- important for translation

36
Q

3’ polyadenylation

A

a stretch of adenylate residues are added to the 3’ end. The poly-A tail contains ~250 A residues

37
Q

major signal for the 3’ cleavage for the tail is

A

“AAUAAA” - cleavage occurs 10-35 nucleotides downstream from the specific signal sequence

38
Q

exon

A

portion of a gene that codes for AAs

39
Q

intron

A

portion of a gene that does not code for AAs or proteins

40
Q

constitutive splicing

A

every intron is spliced out and every exon is spliced in

41
Q

alternative splicing

A

all introns are spliced out and only selective exons are spliced in.

42
Q

monocistronic

A

mRNA that encodes for only one polypeptide

43
Q

polycistronic

A

mRNA that encodes for several polypeptides

44
Q

two types of polycistronic and what they yield

A

1- translation: polyprotien (multiple proteins stuck together), proteases chop them up to yield functional proteins
2- endonuclease: chops up mRNA into monocistronic mRNA, each encodes for a specific protein, they are translated into functional proteins

45
Q

viral proteins

A

enzymes, structural proteins, viral nonstructural proteins, regulatory proteins, inhibitors

46
Q

where does assembly and maturation occur

A

nucleus, cytoplasm, plasma/cell membrane

47
Q

release of progeny viruses (how in naked viruses? in enveloped?

A

naked- lysis

enveloped- budding or lysis

48
Q

layers of enveloped virus once budding occurred

A

matrix protein, host cytoplasm, virus glycoproteins

49
Q

viruses that can bud through the golgi or ER

A

flaviviruses, arteriviruses, coronaviruses and bunyaviruses

50
Q

extracellular spread of viruses

A

virus is adsorbed, enters, replicates, assembles, released and infects new host cell

51
Q

intracellular spread

A

spread from cell to cell without contact with extracellular milieu.

52
Q

mechanisms of intracellular spread

A
  • cell-cell plasma-membrane fusion (Herpesvirus, Paramyxovirus and Retrovirus)
  • passage of virions across tight junction (Herpesvirus)
  • movement of virions across neural synapse (Rabies)
  • viral induction of actin (Poxvirus)
  • viral subversion of actin
  • membrane nanotube subversion (HIV-1)
  • virological synapse (Retrovirus)
53
Q

nuclear spread of virus genome

A

viral genome is integrated into the host cell genome and passed down to next progeny or generation of host cells (Retroviruses)

Virology@RUSVM (11 decks)

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