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Micro/Immuno FINAL > Respiratory Viruses > Flashcards

Respiratory Viruses Flashcards

1
Q

what is the virus family, genome, and virion of influenza?

A
  • orthomyxoviridae
  • segmented (-)ssRNA
  • enveloped
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2
Q

what is the virus family, genome, and virion of adenovirus?

A
  • adenoviridae
  • dsDNA
  • non-enveloped
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3
Q

what is the virus family, genome, and virion of rhinovirus?

A
  • picornavirus(childhood viral section)
  • (+)ssRNA
  • non-enveloped
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4
Q

out of the 3 types of influenza (A, B, C) which is the most common and associated with greatest concerns?

A

type A influenza

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5
Q

what proteins are associated with type A influenza?

A
  • HA: hemagglutinin, cell attachment
  • NA: neuraminidase, viral budding and release
  • M1: matrix
  • M2: ion channel
  • PB1, PB2, PA: transcription complex
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6
Q

which of the type A influenza proteins is often the target of antivirals?

A

NA

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7
Q

which type A influenza protein is the major determinant for human to human transmission?

A

HA

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8
Q

what type of reservoir does type influenza have?

A

animal

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9
Q

how is type A influenza viral replication initiated?

A
  • attachment brings cell and virus membranes into close proximity
  • conformational change triggered after cell attachment by pH change in endosome
  • causes membrane fusion
  • model for all enveloped viruses
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10
Q

where does transcription and replication occur for type A influenza?

A
  • nucleus (EXCEPTION)
  • protected genome (RNP core) escapes nucleus and buds from cell surface
  • NA critical to budding (cleaves connections to free virus so go to extracellular space)
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11
Q

how is influenza transmitted?

A

-aerosol, large and small droplets
*infectivity greatest for particles <10 microns
**ID50 as low as 0.3-6, 50% egg infectious doses (IED50)
=every 10 particles for 1 egg infectious dose so 0.3 =~3 particles so why it is possible to be enough to cause illness

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12
Q

what is the incubation time for influenza?

A

1-4 days: contagious day before symptom onset to 5 days later

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13
Q

T/F: infection from influenza causes the innate immune response to come into play early

A

true

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14
Q

describe seasonal (interpandemic) flu

A
  • fever, malaise, nonproductive cough, sore throat

- lasts 3-7 days after symptoms develop

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15
Q

what are some complications from seasonal flu?

A
  • viral pneumonia
  • bacterial pneumonia
  • reye syndrome (type B + aspirin)
  • otitis media
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16
Q

how is influenza virus prevented?

A
  • attenuated live vaccine:
  • virus mutations require new vaccine development every year- antigenic shift
  • long lead time
  • usually contains an H3N2, H1N1 and Type B strain
  • type A strain generated thru reassortment via coinfection with PR8 strain
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17
Q

how is influenza treated?

A
  • antiviral treatment:
  • amantidine: inhibits acidification of endosome so HA has conformational change
  • blocks entry of ions, and inhibits M2 activity (described above)
  • development of resistance common
  • zanamivir or oseltamivir (tamiflu):
  • blocks release of budding virions
  • development of resistance is not common

-supportive care

18
Q

what are the 4 major influenza pandemics?

A
  • 1918 spanish flu
  • 1957 asian flu
  • 1968 hong kong flu
  • 2009-2010 H1N1
19
Q

what strains of influenza are pandemics thought to arise from?

A

avian

20
Q

describe avian influenza (H5N1)

A
  • highly pathogenic avian influenza: H5 or H7 strains
  • lethal in >75% of 6-8 week old susceptible chicks
  • HPAI strains have multi-basic residues at HA cleavage site allowing replication thru out the body
  • skin lesions, necrotic & swollen combs, systemic infection
  • low pathogenic avian influenza: asymptomatic to slight respiratory infection, no lesions
  • H5 and H7 strains can mutate to HPAI strains
21
Q

how did H5N1 become passable between animals through airborne droplets?

A

the dutch did an experiment with ferrets and after 10 generations virus was capable of airborne transmission between animals

22
Q

how is adenovirus characterized?

A
  • by their serotype
  • diff serotypes associated with different diseases
  • Ad 2 & 5 most frequently studied
23
Q

what are the proteins associated with adenovirus?

A

fiber: cell attachment
penton base: cell entry
hexon: capsid

24
Q

how does adenovirus enter into a host?

A
  • via coxsackie-adenovirus receptor (CAR)
  • pH triggered capsid disassembly
  • moves to nucleus
25
Q

how is the adenovirus gene expression in 3 phases?

A
  1. immediate-early: E1A portion of genome- 2 transcriptional regulators (cell & virus), necessary to reach early stage
  2. Early: 5 genome sections - E1B, E2. E3, E4 and L1, DNA replication & post transcriptional events
  3. Late take over of cellular mRNA
26
Q

where does adenovirus replication occur?

A

dsDNA so replication in nucleus

27
Q

how does adenovirus exit the host cell?

A

weakly lytic because doesn’t have proteins lysing membrane so need cell to die and rupture

28
Q

describe the genome replication process of adenovirus

A
  • initiated on either end, identical end sequences
  • replication in 5’-3’ direction, one strand displaced
  • displaced strand circulizes to allow template copy to be made
  • primed by the protein pTP, unusual priming strategy
29
Q

when does DNA replication occur in the mitotic cycle for adenovirus?

A

s phase, not all cells are actively replicating

30
Q

how does DNA replication occur specifically with the genome sections?

A
  • E1A inactivates pRb leading to s phase gene expression
  • E1B inactivates p53 leading to s phase and preventing apopotosis
  • similar to oncogenic processes
31
Q

what does the E3 genomic component of adenovirus do?

A

-produces proteins important to host immune evasion

32
Q

**what can adenovirus block?

A
  • MHC class I expression reducing CTL cell killing
  • TNF induced apoptosis
  • IFN-alpha and IFN-beta action keeping protein translation active
33
Q

what kind of clinical diseases does adenovirus cause?

A
  • resp infections very common
  • typical symptoms of common cold
  • acute resp disease (ARD): severe pneumonia seen in miliary; serotypes 4&7; vaccine for military
34
Q

T/F: adenovirus is a frequently used vector

A

T

35
Q

what virus is the frequent cause of mild upper resp infections?

A

rhinovirus

36
Q

does rhinovirus have many serotypes and therefore large antigenic diversity?

A

yes over 100 serotypes

37
Q

what is the only known reservoir for rhinovirus?

A

humans

38
Q

how does rhinovirus enter the host?

A

attaches to intercellular adhesion molecule 1 or the very low density lipoprotein (VLDL) receptor

DIRECT INJECTION

39
Q

what is the incubation period for rhinovirus?

A

1-4 days

40
Q

how long is virus shedding detectable for rhinovirus?

A

2-3 days but sometimes detected up to 3 weeks afterwards

41
Q

what are the symptoms of rhinovirus?

A

red nose, blood vessel dilation, nasal discharge that become mucopurulent (neutrophils), epithelial damage likely due to immune response

42
Q

how is rhinovirus prevented?

A

no vaccines b/c too many serotypes and no antivirials b/c resistant mutants

Micro/Immuno FINAL (16 decks)

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