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Virology 1 > Influenza and enveloped viruses > Flashcards

Influenza and enveloped viruses Flashcards

1
Q

characteristics of enveloped viruses

A
  1. nucleocapsids surrounded by coating lipoprotein membrane containing glycoproteins

2 infectivity of enveloped viruses destroyed by ether. nucleocapsid viruses are not harmed by ether

3 enveloped viruses are generally unstable, transmission requires close contact

4 continuous release of virions w/o cell dying via budding

5 more complicated viral assembly

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2
Q

what are the antigens for neutralizing Abs for nucleocapsid and enveloped viruses?

A

nucleocapsid- capsomers

envelopes- envelope glycoproteins

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3
Q

how is the mode of release different between enveloped v nucleocapsid

A

nucleocapsid- lysis

envelope- budding

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4
Q

which is more stable- enveloped or nucleocapids

A

nucleocapsids

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5
Q

describe the orthomyoxovirus characteristics

A
  1. enveloped w/ glycoproteins

2 virions contain 8 separate segments of negative strand ssRNA

  1. each segment of RNA is encoded in a separate helical nucleocapsid
  2. virus contains RNA dependent RNA polymerase because it is negative sense
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6
Q

what is the first macromolecule produced in + stranded genomes? - stranded genomes? double stranded genomes?
which of these need RNA polymerase prepackaged?

A

1 protein

2 plus stranded mRNA- need RNA poly

3 plus stranded mRNA- need RNA poly

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7
Q

is + stranded genome infectious? - stranded genomes? double stranded genomes?

A

yes

no

no

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8
Q

describe why Abs against nucleocapsids are effective against naked viruses but not enveloped?

A

because the envelope conceals the virus, so the Abs will never come into contact

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9
Q

describe influenza replication

A

hemagglutinin molecules bind to sialic receptors on the cell surface, resulting in endocytosis

pH changes in endosome cause release of viral RNA, go to nucleus

RNA polymerase copies - strand RNA into + RNA. creates either mRNA or cRNA, which act as templates for more - strand RNA, effectively replicating the genome

these bud out of the cell to form new virions

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10
Q

what are the two important glycoproteins on influenza

A

hemagglutinin- binds sialic receptors

neurminidase- cleaves host cell connections when budding off

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11
Q

which is more important, Abs against H or G?

A

H- prevents new infection

G- prevents spread of infection

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12
Q

describe hemagglutination testing of influenza

A

the sailic acid moeity is common to RBCs, and if exposed to influenza, they will form a large network that will settle as a thin layer at the bottom of a well

w/o influenca, it settles as a dense droplet

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13
Q

describe hemagglutinin inhibition

A

can be used to titrate the amount of Ab present against flu

do an acute phase with pt serum, and most likely no Ab is present so everything agglutinates

convalesence stage however, Ab exists in pt serum and prevents agglutination by binding flu. can dilute (titrate) to find out how much Ab is present

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14
Q

pandemic

A

world wide epidemic

calculated by determining deaths above expected

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15
Q

what is the difference between influenza A, B, and C

A

each subtype has the same nucelocapsid antigen

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16
Q

which is worse, influenza A epidemics or influenza B?

A

A- minor occurrence every 2-3 yrs, major every 10-30

B- minor occurrence every 3-6 years

17
Q

how are flu vaccines generally constructed?

A

with 1 strained targeted toward influenza B

2 strains targeted towards influenza A (1 for projected H and project N antigens)

18
Q

how do minor epidemics occur

A

antigenic drift- H-antigen mutates slightly leaving only partial immunity in human population

19
Q

how do major epidemics occur?

A

antigenic shift- major change in H antigen where existing immunity provides no protection. additional changes in N protein can make the epidemic worse, but H antigen is always changed

20
Q

what drives antigenic drifts and shifts?

A

drift- mutations in the H antigen (mistake prone RNA polymerase)

shift
1. recombination b/t human and animal strains when both viruses infect the same animal
2 direct transmission and increase virulence of animal flu to humans (swine flu, 1918 pandemic)

21
Q

how is flu diagnosis made?

A

virus isolation in embryonated eggs/tissue cultures

hemagglutinin/ hemagglutinin inhibition

fluorescent An on throat swab

22
Q

how is flu transmitted?

A

person to person via coughs/sneezes. infects upper respiratory tracts

23
Q

what are the flu symptoms?

A

fever, chills, aches, headache, muscle pains

potential development of pneumonia d/t secondary infection (pneumococcus or staphylococcus)

24
Q

what does the flu infect?

A

mucosal surface of respiratory tract

25
Q

why does immunity from infection only last 3-10 years?

A

b/c it is dependent on IgA, which does not last as long as IgG

26
Q

why isnt IgG very effective?

A

no viremia- flu doesnt travel to blood

27
Q

describe 3 drugs used to treat the flu

A

tamiflu and relenza- N protein inhibitors. only effective before or just after infection

adamantanes- H3N2 are resistant, but not H1N1. more effective if given before infections. it inhibits uncoating of virus inside the cell

28
Q

paramyxoviruses characteristics

A

1 singular piece of (-) ssRNA w/ helical nucelcaspid

no major antenicity shifts seen

virions agglutinate RBCs (except RSV- no H protein)

29
Q

paramyxoviruses examples

A

measles
mumps
parainfluenza
RSV

30
Q

croup

A

acute laryngo-tracheo-bronchitis

characterized by dyspnea and stridor (high pitched noisy inspiration)

usually found in kids under 3 and caused by parainfluenza

31
Q

what is the most common cause of lower respiratory infection in infants?

A

RSV

32
Q

what is the treatment for RSV?

A

antiviral- ribavirin- interferes with RNA dependent RNA polymerase

high risk pts get palivizumab to prevent or mitigate infection

33
Q

human metapneumonia virus

A

“relative” of RSV that also causes lower respiratory tract disease

34
Q

characteristics of coronaviruses

A

(+) ssDNA
helical nucleocapsid

usually cause cold, but also contains SARS and MERS

35
Q

SARS

A

lower respiratory tract
dry cough and dyspnea
transmitted by close contact, aersols

china

36
Q

MERS

A

lower respiratory tract
fever, cough, shortness of breath
transmission not understood

Jordan/middle east

37
Q

interferon a/b

A

released by cells when they become infected, bind to neighboring cells and stimulate cellular defenses

38
Q

what are the 2 proteins stimulated by interferon a/b

A

2-5-A synthase- synthesizes 2-5-A, which activates a ribonuclease to destroy mRNA

PKR- inactivates initiation factor 2, inhibiting protein synthesis

Virology 1 (4 decks)

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