E3

Question 1

You have identified 2 enteric viruses that can replicate in M cells. One buds apically & the other basolaterally. What would you predict about the tissue tropism of these 2 viruses

Answer 1

-Apical will have more localized distribution
-Basolateral virus will disseminate & infect tissue like lymphs

Question 2

You infect 2 genetically altered mice with a virus that does not kill normal mice. The first mouse has no pattern recognition receptors. The second produces 100,000 fold more cytokines than a normal mouse after infection. Neither mouse survives the infection. Explain the most likely reason the mouse died.

Answer 2

First mouse didn’t have an innate antiviral response so no cytokines or interferons or T-cell co-stimulatory molecules were produced. Infection was rampant. Second mouse had too many cytokines and resulted in lots of inflammation that was deadly.

Question 3

Which vaccine formulation would be a better choice for an immunocompromised individual: Flublock (Recombinant hemagglutinin protein), or FluMist (Live, attenuated virus)? Why?

Answer 3

Flublock would be better since it is not a live virus and will train the immune system to target viral hemagglutinin proteins. FluMist is bad because it can still replicate although it is weakened. Individuals who are immunocompromised would be unable to mount a good response.

Question 3

Which virus is more likely to cause a pandemic? Justify your answer.

Note that in both cases, the affected person sheds virus starting 12 hours after infection.

a. Virus A - Causes moderate-to-severe respiratory disease, sometimes resulting in death, with symptoms manifesting six days after infection.

b. Virus B - Causes severe respiratory disease, leading to death in all cases, with symptoms manifesting

Answer 3

Virus A is most likely since the long incubation will result in more shedding because they do not show symptoms and will not know they are infected.

Virus B can be prevented by quarantining after symptoms appear.

Question 4

Name 3 routes of virus entry in the body. Name a site-specific defense mechanism associated with each portal of entry.

Answer 4

-Respiratory tract: Mucus tract antigen
-Alimentary tract(Digestive system): Low acidity pH
-Urogenital tract: Low pH in vagina induces confirmation change at the wrong time

Question 5

You identified a new virus that expresses 3 proteins and causes chronic infection. You infect a mouse with the virus and watch what happens to the proteins over time. Based on data (In table) what protein is most likely targeted by the host immune response?

Answer 5

Protein 2 (With the most changes in original sequence) since the virus would have caused changes in the protein over time.

Question 6

Would you predict that a single vaccine against this virus could confer lifelong immunity.

Answer 6

It may be difficult since the mutation rate may be skewed due to the virus

Question 7

What is the origin of retroviral oncogenes

Answer 7

Cellular oncogenes

Question 8

You are studying a virus that can infect both eyes and the lung. Which is likely the site of chronic infection?

Answer 8

The eye could be a site because it is an immune-privileged site. It is exposed to the environment and would need to reach a certain threshold before any possible immune response can occur to save itself

Question 9

Name one way that antibodies can help to eliminate viral infection. Name one way antibodies could promote infection

Answer 9

-Antibodies can help eliminate viral infection by binding to them so they can be marked for elimination by the immune response.
-Some viruses prefer to replicate in certain environments like phagocytic cells. Marking viruses with antibodies will make it easier to reach these desired environments

Question 10

What is viremia

Answer 10

Virus particles in the blood stream. Helps facilitate spread to other tissues/organs

Question 11

Describe 2 biological activities of interferons

Answer 11

-Perform autocrine or paracrine signalling
-Can bind to the interferon receptor on its self (Autocrine) or bind to the other cells interferon receptors (Paracrine)

Question 12

Describe 3 basic requirements to ensure successful infection

Answer 12

1. High concentration of virions that have high survivability
2. Must infect accessible, susceptible, and permissive cells
3. Should target ones with ineffective or absent immune response

Question 13

Why would a virus want to prevent autophagy

Answer 13

Autophagy causes cell to degrade its cellular components & substrates. Resources and machinery necessary for viral replication are destroyed. Virus can’t replicate.

Question 14

Describe 3 properties of transformed cells.

Answer 14

-Reduced requirement for serum growth factors
-Lack of contact inhibition
-Lose polarity by having altered morphology which can make them look undifferentiated

Question 15

Viruses often downregulate surface expression of MHC class I in infected cells/ How does this help the virus? Conversely, how might the downregulation of MHC class I signal to the immune system that that cell is infected.

Answer 15

MHC Class I often takes antigens and presents them to T-cell receptors such as CD8+. Virus won’t be targeted by T-cells as a result. Molecules will be able to detect the absence of MHC class I and will send out other cells like NK cells to find the infection

Question 16

You have developed a new nucleoside analog that works as a virus-activated prodrug. What is the advantage of the prodrug mechanism? What is the risk of using this antiviral alone in treating infected individuals?

Answer 16

-Prodrug is only activated in the presence of the virus. Meaning it could have reduced side effects
-The virus could learn and evolve away from it. Use of a combination of treatments make it harder to adapt.

Question 17

You have been asked to make an attenuated strain of a new coronavirus found in horses in hopes that this could be used as the basis for a vaccine. Although little is known about this particular coronavirus, you recently identified the ORF6 protein as a virulence factor. Describe 2 strategies you could use to generate an attenuated coronavirus

Answer 17

-We can take the virus and passage it in other animal host. Virus will mutate so that it can survive in that animal and not horse (Attenuation)

-We can create a viral genome with ORF 6 removed using methods such as CRISPR so that it wont be as virulent when injected.

Question 18

Describe how viroreceptors and v-cyclin impact infection

Answer 18

-Viroreceptors redirects cellular ligands and prevents release of IFN & others.
-V-cyclins can act as cyclins and turn on cell cycle. V-Cyclin helps viruses to replicate because cell cycle is not off.

Question 19

You are studying how a virus that establishes chronic infection causes cancer. Your data indicate that the virus does not integrate into the host genome or encode for any viral proteins that impact cell cycle. How does this virus likely cause cancer.

Answer 19

Virus could sequester Rb proteins and prevent it from regulating cell cycle.

Question 20

Which strategy is better: Using one antiviral drug to treat an infected individual or a combination therapy including more than one antiviral?

Answer 20

Combination therapy is better because they can target different aspects of the virus so even if the virus mutates and is resistant to one antiviral, there are more present to fight off against the virus