6. Viruses manipulate cells, and cells have mechanisms to control viruses. Most patients in your hospital recovered from their Ebola Reston virus infection, except for one patient. You isolated this patient’s virus. To explore the mechanism of virulence for your new virus isolate, you tested it in a wild type (WT) cell line and a cell line with a deletion of the gene encoding autophagy factor ATG5 (atg5 knockout/KO). Lysates were prepared from cells infected with the virus you had previously collected from patients that recovered (lab strain) and your new virus isolate. The proteins were separated by size on a denaturing gel and all proteins (cell and virus) were visualized. Your results are shown on the right.
a. For the lab strain, describe the result and suggest a potential reason why most patients were able to recover from their virus infections. (4 pts)
b. For the new isolate, describe the result, and also suggest a potential virulence mechanism for the new isolate. (4 pts)
c. Based on your results obtained with ATG5 knockout cells, what could you predict about the potential relationship between autophagy and protein translation. (2 pts)
7. A successful immune response to a virus infection will prevent further spread of the virus, clear the virus from tissues and fluids, and protect the host against re-infection.
a. Draw a diagram that depicts the amount of infectious virus produced after an acute viral infection. (1 point)
b. For this acute infection, draw and label a diagram that depicts the relative appearance and changes in levels of 1) antibodies 2) effector CD8 cytotoxic T cells 3) NK cells and 4) type I IFN. (4 points)
c. What are two ways that antibodies can neutralize virus? (2 points)
d. What protein of this enveloped virus is most likely to induce neutralizing antibody? CD8+ T cell response? (2 points)
e. What is the most likely oligomeric form of the blue fusion protein? (1 point)
8. There has been a recent epidemic of respiratory disease in cattle that has had a major negative impact upon the dairy industry. After performing PCR for a panel of virus families on cow nasal discharge samples, scientists are excited to discover that a novel orthomyxovirus, ‘virus X’, can be detected in all of the cows with disease but none of the healthy cows.
a. Your first step is to confirm the presence of virus X in diseased cows using a secondary measure. What are two other detection methods that you could use? (2 pts)
b. Your secondary measure confirms the presence of virus X in diseased cows. You now plan to determine if virus X is indeed the causative agent of respiratory disease in cows. Using Koch’s postulates, design experiments to accomplish this (6 pts).
c. You are able to design a highly effective antiviral drug against this orthomyxovirus, however some scientists are pessimistic about the likelihood of eradicating the virus. What is one biological reason why viruses in this family may be difficult to eradicate? (2 pts).
9. Virion particles have evolved optimally functional stuctures.
a. On the picornavirus particle pictured below (1) identify the type of symmetry and (2) indicate the 5-fold, 3-fold and 2-fold axes of symmetry (4 points).
b. Provide two reasons why is this a popular shape for virus particles? (2 points)
c. Describe the relationship of the 5-fold axis to picornavirus receptor binding (1 point).
d. Briefly describe 3 of the steps required for delivery of the picornavirus genome into a cell to be infected. (3 points)
