Virology Chapter 9

Question 1

what does asymptomatic reservoirs mean, and what is the asymptomatic reservoirs of influenza

Answer 1

species carrying the disease without having any symptoms
ducks / waterbirds

Question 2

Influenza binds to SA, but the type of linkages matter, what are the different linkages for avian, human and pigs

Answer 2

avian: a-2,3
human: a-2,6
pigs: a-2,6 and a-2,3

Question 3

What does it mean when pigs have both linkages

Answer 3

it means that it can infect both avians and humans because it expresses both receptor types

Question 4

dual infection can lead to…
(pigs infecting both humans and birds)

Answer 4

re-assortment of viral genome segments
creation of new hybrid strains

Question 5

To control and prevent the infection, we use (2)

Answer 5

antiviral drugs and vaccines

Question 6

Why do influenza epidemics occur?

Answer 6

because new strains emerges, and they have unfamiliar H and N glycoproteins

Question 7

There are two ways the H and N can change, what are they?

Answer 7

Antigenic Drift
Antigenic Shift

Question 8

What is antigenic drift

Answer 8

minor changes to H and N due:
- point mutations
- amino acid substitutions
- error in RNA Pol. Complex: can’t proofread

So, H and N are immunologically similar to previous strains, antibiotics may or may not still work

Question 9

What is antigenic shift

Answer 9

major changes to H and N
- genetic reassortment of RNA segments (human + bird combine to make a new thing)
- immunologically distinct

Question 10

What happens when there is an antigenic shift

Answer 10

pandemics (very rare)
bodies don’t have immunological memory

Question 11

antigenic shifts only happen in

Answer 11

influenza A due to animal reservoirs

Question 12

After a pandemic, the strain usually begins to…

Answer 12

drift

Question 13

the drift after a pandemic allows the virus to

Answer 13

make small changes and improve human evasion

Question 14

Antigenic drift is caused by mutations in

Answer 14

epitopes

Question 15

what are epitopes

Answer 15

part of the antigen molecule where the antibody binds to

Question 16

Why do we need annual vaccines

Answer 16

because of antigenic drift (minor changes) and it means that previous vaccines may not be the best fit (but can be adequate)

Question 17

Antigenic shift is caused by reassortment of

Answer 17

RNA segments

Question 18

the reassortment of virus genome from antigenic shift causes an

Answer 18

entirely new gene, creating a new subtype
(vaccines don’t work at all)

Question 19

What are “plug drugs”

Answer 19

antiviral drugs that block active site of N protein

Question 20

What happens when there is no N

Answer 20

N cannot cleave SA, so the virus cannot leave the host cell to infect new host cells

Question 21

example of plug drugs

Answer 21

oseltamivir (tamiflu)
zanamivir (relenza)

Question 22

there are also other drugs like amantadine (symmetrel) and rimantadine (flumadine), what do these drugs do?

Answer 22

inhibit M2 channel, blocking the release of influenza virus genome into the cytoplasm (cannot replicate)

Question 23

What are the two molecular mechanisms that result in new strains of influenza virus?How frequently does each mechanism occur? Which mechanism can result in new influenza virus strains with pandemic potential?

Answer 23

antigenic drift (frequently every year) and antigenic shift (less frequent)
pandemic: antigenic shift

Question 24

What step in the Influenza replication cycle does the anti-viral drug Tamiflu inhibit? How does this drug work?

Answer 24

It inhibits the cleavage of sialic acid by binding to N protein, virus cannot egress

Question 25

Why are birds and other mammals, especially pigs, important factors in the evolution of new influenza virus strains?

Answer 25

because from animals, the virus shed in their droppings / respiratory secretions, and can quickly spread through farms and farmers and other animals.

Question 26

Why would antibodies against the H protein be more effective at neutralizing the influenza virus than antibodies against the N protein?

Answer 26

because H is extended out in the virus particle more than N (its taller) and there are more Hs than Ns. H is used by the virus to attach to the cell, so blocking it would prevent binding.

Question 27

What are the 3 important sites in the RDRP

Answer 27

- site that binds 5' of (-) RNA (doesn't release it) - site that acts as endonuclease - site that reads (-) RNA template and catalyze the synthesis of mRNA

Question 28

6 of the 8 segments are......, and the remaining 2 would be.....

Answer 28

monocistronic spliced

Question 29

Antibodies can neutralize viruses in the body's fluids, this means that the virus is unable to...

Answer 29

bind to the host cell and infect

Question 30

antibodies bind to

Answer 30

epitopes

Question 31

why are antigenic shifts much less frequent?

Answer 31

because of segmented rna genome

Question 32

drift can happen with any virus -- more frequently with

Answer 32

RNA genome virus

Question 33

Shift can only happen if the virus as a

Answer 33

segmented genome

Question 34

Drift and shift can occur simultaneously T or F

Answer 34

true

Question 35

Why are there many more antibiotics compared to antiviral drugs

Answer 35

Because the antiviral drugs must not harm healthy uninfected cells, they must target a virus-specific activity

Question 36

Why is symmetrel no longer recommended

Answer 36

because the virus has shown resistance through mutations that change the shape of the protein where it can bind to the drug

Question 37

What causes the influenza virus to NO longer be restricited to the respiratory tract

Answer 37

when H is cleaved as it moves through the Golgi by the enzyme: Furin

Question 38

How are influenza vaccines made

Answer 38

embyronated egg / cell culture/ recombinant DNA tech

Question 39

new vaccines are produced by

Answer 39

genetic reassortment to produce a strain of H antigen that we want

Question 40

Explain the process of making a vaccine from the embryonated chicken egg

Answer 40

circulating strain and vaccine strain co-infect the egg, and a new strain is collected from allantoic fluid, it's inactivated, treated w detergents, then turned into an injection

Question 41

What are the three types of vaccines of influenza

Answer 41

Whole vaccine (WV) - intact but inactivated Subvirion vaccine (SV) - only virus envelope (distrupted virus) Surface Antigen Vaccine (SAV) - only use H and N glycoproteins (subunit)

Question 42

Influenza is... (acute/persistent/latent/oncogenic)

Answer 42

persistent