Virology - vaccines, antivirals, viral evolution

Question 1

What’s in a vaccine, broadly speaking? (5)

Answer 1

water
preservatives & stabilisers
active ingrediant (antigen)
adjuvant
residues

Question 2

Active vs passive immunization

Answer 2

active = administer antigen or parts
passive = administer immune response products like antibodies

Question 3

attenuated and inactivated vaccines.

Answer 3

Vaccine attenuation means the alteration of a virus to decrease or inhibit its virulence whilst remaining replication competent.

Inactivated vaccines cannot infect cells and replicate, but can still trigger an immune response.

Question 4

Modern vaccines are based on 4 molecular techniques

Answer 4

I. Recombinant vaccines
II. Genetic attenuation
III. Vector vaccines
IV. Other (e.g. mRNA vaccines)

Question 5

What is the main difference between mRNA and vector vaccine

Answer 5

The mRNA vaccine contains messenger RNA.
The vector vaccine contains viral genome that encodes spike protein for the target pathogen.

Question 6

clinical trial phase I involves?

Answer 6

tests safety of vaccine

Question 7

clinical trial phase II involves?

Answer 7

tests immunogenicity of vaccine

Question 8

clinical trial phase III involves?

Answer 8

tests efficacy of vaccine

Question 9

clinical trial phase IV involves?

Answer 9

extended clinical trials

Question 10

Efficacy vs effectiveness

Answer 10

vaccine efficacy refers to how the vaccine performs in indeal conditions - controlled clinical trials.

vaccine effectiveness refers to how the vaccine performs in the wild

Question 11

Vaccine efficacy is the

Answer 11

percentage of reduction in disease incidence in a vaccinated group compared to an unvaccinated group under optimal conditions (in clinical trials).

Question 12

Vaccine effectiveness is

Answer 12

the ability of a vaccine to prevent outcomes of interest in the “real
world”.

Question 13

first antiviral discovered in the 50’s/60’s

Answer 13

amantadine

Question 14

Is drug resistance more frequent among RNA or DNA viruses?

Answer 14

Drug resistance is more frequent in RNA viruses because of their higher rate of mutation.

Question 15

phage

Answer 15

or bacteriophage

is a Virus that infects bacteria

Question 16

viroid

Answer 16

an infectious entity affecting plants, smaller than a virus and consisting only of RNA nucleic acid without a protein coat.

Question 17

what is satellite RNA

Answer 17

Satellite RNAs and satellite viruses are extraviral components that can affect either the pathogenicity, the accumulation, or both of their associated viruses while themselves being dependent on the associated viruses as helper viruses for their infection.

Viral satellite RNAs (satRNAs) are small subviral RNAs and depend on the helper virus for replication and spread.

Question 18

virophage

Answer 18

Virophages are small, double-stranded DNA viral phages that require the co-infection of another virus. The co-infecting viruses are typically giant viruses. Virophages rely on the viral replication factory of the co-infecting giant virus for their own replication.

Question 19

prion

Answer 19

Proteinaceous infectious particles

The term “prions” refers to abnormal, pathogenic agents that are transmissible and are able to induce abnormal folding of specific normal cellular proteins called prion proteins that are found most abundantly in the brain.

Question 20

What are the three different types of spongiform encephalopathies

Answer 20

Infectious, genetic and sporadic/spontaneous.

Question 21

Scrapie

Answer 21

a TSE affecting sheep (sometimes goats)

Question 22

CWD

Answer 22

chronic wasting disease, a TSE of cervids (deer)

Transmission: animal-to- animal and vi environment

Question 23

Four main drivers of virus evolution:

Answer 23

1. Large numbers of progeny
2. Large numbers of mutants
3. Quasi-species effects
4. Selection

Question 24

What are Quasi-species effects

Answer 24

quasispecies are dynamic distributions of non-identical but closely-related mutant and recombinant viral genomes. They are subjected to a continuous process of genetic variation, competition and selection, and act as a unit of selection.

Question 25

viral genomic recombination is

Answer 25

Recombination is when parts of different viral genomes mix or trade places during transcription.

Question 26

viral genomic reassortment is

Answer 26

viral genome segments can get “mixed” up if two virions with slightly different segments infect a cell at the same time.

Reassortment only happens in viruses with segmented genomes.

Reassortment is loads more frequent than recombination and is why influenza mutates the way it does, causing new pandemics regularly.

Question 27

Error threshold in viral mutation

Answer 27

the level of mutations that are still beneficial

If exceeded: loss of viral infectivity

If too below threshold: cannot produce enough mutations to survive selection

◦ RNA viruses evolve close to their error threshold
◦ DNA viruses evolve far below their error threshold.

Question 28

Which viruses evolve close to their error threshold?

Answer 28

RNA viruses evolve close to their error threshold

Question 29

Which viruses evolve far below their error threshold?

Answer 29

DNA viruses evolve far below their error threshold.

Question 30

Muller’s ratchet

Answer 30

small, asexual populations accumulate deleterious mutations

The theory of Muller’ Ratchet predicts that small asexual populations are doomed to accumulate ever-increasing deleterious mutation loads as a consequence of the magnified power of genetic drift and mutation that accompanies small population size.

Question 31

Genetic bottlenecks

Answer 31

A genetic bottleneck occurs when a population is greatly reduced in size, limiting the genetic diversity of the species.

Recombination and reassortment help to overcome the reduced genetic diversity caused by a genetic bottleneck.

Question 32

Antigenic shift refers to

Answer 32

genetic diversity arising after recombination or reassortment.

Question 33

Antigenic drift refers to

Answer 33

genetic diversity arising from copying-errors and immune selection.
May occur each time a genome replicates and includes accumulation of mutations over time.

Question 34

Emerging virus

Answer 34

newly discovered virus with increasing incidence

Question 35

Re-emerging virus

Answer 35

virus that has existed previously but is rapidly increasing in incidence or geographic range

Question 36

viral spillover

Answer 36

transmission of the virus into novel host population

Question 37

viral Spillback

Answer 37

transmission of the virus back to maintenance host

Question 38

Steps of emerging viral infections

Answer 38

1. Encounter
2. Establishment and dissemination

Question 39

A stable host-virus relationship maintains

Answer 39

the virus in the appropriate ecosystem.
E.g. herpes virus.

Question 40

An evolving host-virus relationship involves

Answer 40

passage of the virus to a naïve population.

Question 41

A dead-end host-virus relationship involves

Answer 41

one way passage to a different species. This is very common but those that produce sustainable transmission are rare.