1 Virology Review Questions - Topic 1. 1. Enveloped viruses are typically less robust or stable than naked viruses when outside of the host cell. Suggest reasons as to why this might be so. 2. Define the term "host range" from a virology perspective. 3. A virus may have a very limited host range or a very broad host range. What determines the host range of a virus? 4. A new virus is able to infect a monkey cell but not a human cell when cultured in the laboratory. However, if the genome is extracted and then micro-injected into a human cell, a productive infection will occur. In other words, progeny viruses are produced. Is the human cell susceptible and/or permissive? 5. Blocking viral attachment and entry is the best way to prevent a potential infection. In many cases, such as the antibodies generated by our own immune responses, the anti- receptors on the viruses are neutralized. An alternative method would be to block the virus receptor; however, this is not done very often. Suggest reasons why this might not always be a possible therapy for prevention of infection? 6. There are three basic types of vaccines used to induce immunity for prevention of infection by viruses. What are they? What are the advantages and disadvantages of each type? If you were asked to design new vaccines for Ebola virus and the common cold virus, what type of vaccines would you use? What would be the criteria used in making your decision? 7. Why are there relatively few effective anti-viral drugs when compared to anti-bacterial agents? Why aren't such drugs used to treat common viral illness such as colds? Virology Review Questions - Topic 2 - Picornavirus Case Sudy. 8. Enteroviruses such as poliovirus, are known for being transmitted via the fecal-oral route and causing disease. What physical traits do these viruses have that allow them to carry this out? 9. Why does the poliovirus utilize a polyprotein strategy when translating its mRNA? Why aren't the individual viral genes translated separately into the individual proteins? 10. In a laboratory experiment, human cells were infected with poliovirus and a mutant version of poliovirus is isolated. In this mutant, the entire 5' UTR region of the genome is deleted. When this mutant virus is used to infect new host cells, what process(es) will be affected by this deletion? What will the effect be on the virus replication cycle? 11. What is VPg and why is it important? If the gene encoding VPg was deleted, what effect would this have on the virus replication cycle? 12. What would be the advantage to the virus in using a "replication compartment" to replicate its genome instead replicating its genome in the cell's cytoplasm?
2 13. With the destruction of certain host components by poliovirus, host cell protein synthesis is no longer initiated since the ribosomes cannot recognize host mRNA. Is this an advantage or disadvantage for the poliovirus? Specifically, what feature of poliovirus allows it