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MOHD 4.2 > 20 - Virus Overview (Stapleton) > Flashcards

20 - Virus Overview (Stapleton) Flashcards

1
Q

virus characteristics

A

small

obligate intracellular parasitesencased in protein package (capsid)

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2
Q

adsorption phase

A

lasts 1 hour

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3
Q

eclipse phase

A

10-12 hours

virus becomes uncoated

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4
Q

synthetic phase

A

12 hours post infection

new virus particles are assembled and released

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5
Q

latent period

A

no extracellular virus detected

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6
Q

virus inside host

A

replication

consist of genome, RNA and proteins

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7
Q

virus outside host

A

no replication
encased by protein shell (capsid) that interacts with environment
enveloped or not

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8
Q

virus envelope

A

made of glycoproteins
derived from infected cell membrane
more sensitive to inactivation than naked viruses

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9
Q

virus morphology

A

Icosahedral
helical
complex

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10
Q

icosahedral

A

180-240 faces

symmetrical

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11
Q

helical

A

all human helical viruses that cause diesease are enveloped

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12
Q

why does viral structure matter

A

structure elicits immune response
structure imporatnat in viral replication
viral replication steps are targets of therapy

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13
Q

virus genome

A 
ss, ds
DNA, RNA
circular, linear
non segmented, segmented
ssRNA have polarity
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14
Q

steps in replication

A 
attachment
entry
uncoating
genome expression
genome replication
assembly
egress
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15
Q

attachment of virus

A

using viral attachment protein (VAP), binds specific cell receptor (usually surface protein)

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16
Q

non enveloped VAP

A

protein on capsid

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17
Q

enveloped VAP

A

glycoprotein envelope

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18
Q

naked entry

A

internalization into endosomes
neutral pH- plamsa membrane pore entry
low pH-amino acids making pore entry

19
Q

enveloped entry

A

gp VAP binds cell receptors and have hydrophobic fusion peptide
1-env membrane fuses directly with cell membrane
2-virion is internalized into endosomes

20
Q

antiviral drugs targeting entry

A

blocking entry of virus can prevent infection

21
Q

HIV attachment and entry

A

HIV gp120 attaches to CD4
conformational change to allow interacting with CCR5
exposes fusion peptide in gp41
brings viral membrane and plasma membrane together
fusion

22
Q

Influenza attachment and entry

A 
influenza VAP (gp HA) interacts with cell receptor (sialic acid)
virion taken into endosomes
low pH leads to interaction between HA and endosomal membranes fusing
23
Q

DNA genome expression

A

transcription to RNA

translation to protein

24
Q

RNA+ genome expression

A

translation to protein

25
Q

RNA - genome expression

A

transcription to RNA+

translation to protein

26
Q

retrovirus genome expression

A

RNA to DNA with reverse transcription
transcription to RNA
translation to protein

27
Q

genome replication by

A

DDDP
DDRP
RDRP
RDDP

28
Q

DNA virus replicates where

A

nucleus

with DDRP

29
Q

RNA+ genome replication

A

translation to protein

transcription to RNA- to make template for RNA+

30
Q

RNA- genome replication

A

Transcription to RNA+ to make template for RNA-

Translation to protein

31
Q

retrovirus genome replication

A

RNA+ use RT to make DNA- strand and destruction of RNA+

make DNA+ strand from DNA- template for ds DNA

32
Q

what is a provirus

A

retroviral DNA integrated into human genome

33
Q

what facilitates immune escape of viruses

A

viral polymerases are error prone

absence of proof reading activity

34
Q

translation of viral proteins

A

viruses use host ribosomes

viruses use host translation machinery

35
Q

virus assembly

A

capsid self assemble and stuff genome in (DNA, icosahedral)

capsid forms around genome (helical, some icosahedral)

36
Q

envelopment assembly

A

capsid budding into cell membrane containing viral proteins (plasma mem, intracellular mem)

37
Q

viral egress

A

cytolytic by lysing (non envelope)
virus buds from plasma mem (HIV)
released from secretory pathway (HCV)

38
Q

maturation in viral replication

A

proteins translated as proproteins (polyproteins)

must be processed into mature proteins and cleaved by protease to make infectious

39
Q

why do we care about replication

A

rates may correlate with pathogenesis (high rate=fulminant disease or more rapid disease)
antiviral treatment that interfere with replication enzymes

40
Q

viral transmission

A

only in humans (small pox, polio, HIV)
animal reservoirs but spread to humans (flu)
human reservoir but no human to human transmission, through vector (dengue, yellow fever)
animal or insect reservoir, rare human to human (rabies, zika)

41
Q

factors influencing acquisition of virus

A

season
age
genetics
immune status

42
Q

enveloped virus vs. naked

A

enveloped is more sensitive to drying and must be transmitted through droplet or body fluid
not as stable

43
Q

virus portal of entry

A

upper respiratory, oral, sexual

fomites, blood, zoonoses, translation, maternal to fetal

MOHD 4.2 (13 decks)

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