Chapter 9

Question 1

List the three primary methods for controlling viral diseases.

Answer 1

1. Prevent transmission/entry into animal
2. Vaccinate
3. Use antivirals

Question 2

What are the two types of whole viruses?

Answer 2

live and inactivated

Question 3

What is a live vaccine?

Answer 3

a vaccine with containing a replicating, infectious virus

Question 4

What is an inactivared virus?

Answer 4

a killed virus, partially purified supensions of virions, inactivated by chemical or physical treatment

Question 5

What is the goal of vaccination?

Answer 5

to prevent or reduce disease, not necessarily to prevent infection

Question 6

What are the 4 different subcomponents of viruses that are used in vaccines?

Answer 6

protein subunit, virus-vectored, virus like particle, DNA

Question 7

What is a virus-vectored subcomponent?

Answer 7

a virus, such as vaccinia virus, that is used as an in vivo vector for the gene specifying the protective antigen

Question 8

What is a virus like particle?

Answer 8

a particle comprised of viral proteins assembled in a virion-like structure

Question 9

What DNA is used in viruses?

Answer 9

Purified DNA that codes for a protective antigen

Question 10

What are virulent live virus vaccines?

Answer 10

vaccines that produce planned infections where animals are infected at an opportune time or are injected into a non-critical site where lesions are acceptable

Question 11

What is the most common form of live virus vaccines?

Answer 11

avirulent/attenuated live virus vaccines

Question 12

Where do naturally occurring avirulent strains come from?

Answer 12

they may be from the same host, or a closely related by heterologous host

Question 13

What is an example of a vaccine that came from naturally occuring avirulent strain?

Answer 13

the cowpox vaccine against smallpox

Question 14

What is the goal of experimentally attenuated strains?

Answer 14

to produce a virus with reduced virulence, but which still retains its original ‘protective antigens’ and is capable of replicating sufficiently in the host to stimulate an adquate immune response

Question 15

What are empirically-derived mutants selected for?

Answer 15

chance mutations

Question 16

What are temperature sensitive -or cold adapted mutants selceted for?

Answer 16

mutants with skewed temperature preference

Question 17

What are viruses that have temperature sensitive mutants forced to do?

Answer 17

adapt to lower temperature by repeated passage in vitro thus they lose the ability to replicate at normal body temperatures

Question 18

What knowledge is required to generate a genetically engineered mutant?

Answer 18

which genes control the virulence of the virus

Question 19

What are inactivated whole virus vaccines?

Answer 19

virulent virus grown in cell culture or embryonated chicken eggs is usually partially purified and then inactivated and packaged as a vaccine

Question 20

What problems are associated with inactivated whole virus vaccines?

Answer 20

proper inactivation is difficult, they are expensive, multiple doses are needed

Question 21

What are protein subunit vaccines composed of?

Answer 21

individual protective protein subunit of the virion that will stimulate immunity

Question 22

What are purified subunit vaccines?

Answer 22

vaccines obtained by purification procedures from degraded whole virus

Question 23

What are closed subunit vaccines?

Answer 23

where recombinant DNA technology used to express a cloned gene coding for a protective antigen in an in vitro expression vector

Question 24

What are synthetic peptide vaccines based on?

Answer 24

amino acid sequence of the protective antigen

Question 25

How are synthetic peptide vaccines produced?

Answer 25

by chemically synthesizing a peptide in a machine from amino acid sequences

Question 26

What problems are associated with synthetic peptide vaccines?

Answer 26

no glycosylation, poorly immunogenic

Question 27

What are virus-vectored vaccines made by?

Answer 27

inserting genes for the protective antigens into another virus, so that that virus will infect the natural host and serve as a ‘vector’ for expression of the inserted genes within the animal

Question 28

What are the four advantages associated with virus-vectored vaccines?

Answer 28

1. Not possible to revert to virulence 2. Protective antigens from several pathogens can be inserted into one vector 3. Relatively inexpensive to produce 4. Pox virus vectors are relatively stable

Question 29

What is the biggest single concern associated with virus-vectored vaccines?

Answer 29

the biohazard potential to the vector itself

Question 30

What is the difference between a virus like particle and a virus-vectored vaccine?

Answer 30

they morphologically resemble the actual virus and induce neutralizing antibody, but they do not have the nucleic acid

Question 31

What are the three main areas of concern when dealing with vaccines?

Answer 31

effectiveness, safety, and stability during storage

Question 32

How can a DNA vaccine be used to yield a protein antigen?

Answer 32

sufficient DNA gets into cells and is expressed by the cell to produce immunizing amounts of protein antigen of the pathogen

Question 33

List five advantages for use of a replicating viral vaccine.

Answer 33

1. Replicating agents yield greater antigenic mass because of amplifying effect
2. More natural presentation of viral antigens
3. Spreads over mucosal surfaces during replication better than non-replicating products, thus stimulating greater mucosal immunity
4. Replicating vaccines generally stimulate longer lasting immune responses - a single dose is often adequate
5. With live products, immunization of unvaccinated herd-mates can occur

Question 34

What is a minor problem to bear in mind about replicating viral vaccines?

Answer 34

interference by intercurrent virus infections

Question 35

What are some potential hazards of replicating viral vaccines?

Answer 35

insufficient attenuation, reversion to virulence, danger to pregnant animals, spread to other animals from shedding, live viral contaminants

Question 36

What are three benefits of antiviral drugs?

Answer 36

1. They can prevent an infection, or stop an infection after it has started
2. Provide therapeutic option for those already infected
3. Serve as a second arm of defese against virus infections for which vaccines are not available or are not effective

Question 37

List 5 factors that contribute to the limited repertoire of effective antiviral drugs.

Answer 37

1. Challenge of developing drugs that are safe and have high potency
2. Specificity of viral agent
3. Variable patterns of infection
4. In vitro replication
5. Cost

Question 38

What is the mechanism of action of oseltamivir?

Answer 38

blocks the binding of neuraminidase to Sialic Acid

Question 39

What is the mechanism of action of Acyclovir?

Answer 39

it blocks DNA replication of the virus

Question 40

What is Acyclovir highly effective against?

Answer 40

herpes simplex

Question 41

What type of drug is Acyclovir?

Answer 41

a prodrug

Question 42

Acyclovir has no effect on what?

Answer 42

non-infected cells

Question 43

What is AZT’s mechanism of action?

Answer 43

to block reverse transcription

Question 44

AZT was the first antiviral licensed to treat what?

Answer 44

HIV-1

Question 45

What are drawbacks to AZT?

Answer 45

Competes with thymidine for formation of NTP, short half-life, there are more effective anti-retrovirals (used mainly as a prophylactic)