Study questions for Topic 12

Study questions for Topic 12 (Epidemiology and Control of Viral Infections)

Vaccines

1. What is “herd immunity”?
2. What is the difference between a passive vaccine and an active vaccine? Describe a natural method of passive immunization.
3. Compare attenuated and inactivated vaccines. Provide an example of each. Why do some vaccines need adjuvants and others do not?
4. What are the advantages and disadvantages of the oral poliovirus vaccine (OPV)? What are public health problems that are likely to occur if OPV vaccination is abruptly ended?
5. It’s been said that the inactivated influenza vaccine does not s2mulate robust immunity because it contains mainly HA protein. Can you explain this?
6. What makes the HPV and HBV vaccines unusual?

Antiviral drugs

1.  Why are there so few antiviral drugs? Why are there so many for HIV?
2. Why can’t we isolate a drug that blocks the production of HIV genomes from the provirus? How do nucleoside analog antiviral drugs work? Why does the drug acyclovir have fewer side effects than AZT?
3. Why is resistance to Tamiflu pervasive but not resistance to Relenza? Why does antiviral drug resistance occur?
4. Name one mechanism by which viruses become resistant to a specific antiviral. What are the antiviral targets for inhibition of HIV‐1?

Short answer questions

1. Explain why the antibiotics we use to treat bacterial infections are not effective against viral infections and why most of the limited number of antiviral chemical agents we do use therapeutically work by blocking viral nucleic acid synthesis.
2. How do antiretroviral drugs that bind to HIV-encoded protease help to reduce the number of HIV in the body?

2. Match the following drugs with the viral infections they are used against:

_____ amantadine, rimantidine, zanamivar, and oseltamivir

_____ acyclovir, famciclovir, penciclovir, and valacyclovir

_____ foscarnet, gancyclovir, cidofovir, valganciclovir, and fomivirsen

_____ AZT (ZDV), didanosine, zalcitabine, stavudine, nevirapine, delavirdine, saquinavir, and ritonavir

• HIV infection and AIDS
• influenza A
• severe CMV infections such as retinitis
• HSV and VZV infections

3. Match the following:

_____ These drugs do not resemble regular DNA building blocks. They bind to an allosteric site that regulates reverse transcriptase activity rather than to the enzyme’s active site. They prevent HIV provirus formation.

_____ These are drugs that bind to the active site of an HIV-encoded protease and prevent it from cleaving the long gag-pol polyprotein and the gag polyprotein into essential proteins essential to the structure of HIV and to RNA packaging within its nucleocapsid. As a result, viral maturation does not occur and noninfectious viral particles are produced.

_____ These drugs chemically resemble normal DNA nucleotides, the building block molecules for DNA synthesis. They bind to the active site of the reverse transcriptase which, in turn, inserts it into the growing DNA strand in place of a normal nucleotide. Once inserted, however, new DNA nucleotides are unable to attach to the drug and DNA synthesis is stopped. This results in an incomplete provirus.

• nucleoside reverse transcriptase inhibitors
• non-nucleoside reverse transcriptase inhibitors
• protease inhibitors
• entry inhibitors