30. HIV infection and AIDS

Question 1

What are the ways in which HIV can be transmitted?

Answer 1

1. Sexual contact
2. Contact with blood or blood products
3. Perinatal (mother-to-child: before, during or after birth/ breast milk)

Question 2

What cell types can be infected with HIV?

Answer 2

CD4+ cells.
Main targets = T helper cells and Macrophages.
Can also include microglial cells and dendritic cells.

Question 3

Which receptors are involved in the interaction between HIV and its host cells?

Answer 3

Major receptor = CD4

Co-receptor = Chemokine

Question 4

In what ways can HIV kill CD4+ T cells?

Answer 4

1. Death of infected cell by cytoplasmic effect of virus
2. Activation-induced cell death (apoptosis)
3. Killing of infected cells by virus-specific CTLs

Question 5

How can HIV avoid destruction by the immune system?

Answer 5

1. Killing of CD4+ T cells
2. Establishment of latent state in host cells
3. Trapping of immune complexes containing HIV in folicular dendritic cells
4. Genetic mutations in HIV leading to a change in viral antigens

Question 6

What laboratory methods are used to screen for and confirm the presence of HIV antibody?

Answer 6

Screen for HIV-1/-2 antibodies by ELISA or rapid EIA (traditional) or 4th generation combination HIV Ab/p24 antigen (current).
Confirm positive results with Western blot (traditional) or multispot, a rapid EIA (current).

Question 7

What are the advantages of the combination HIV antibody/ p24 antigen test over the traditional testing algorithm?

Answer 7

Detects HIV as early as 2.5 - 3 weeks post infection because p24 Ag appears early.

Question 8

What does a high viral load, and a CD4+ T cell count

Answer 8

Passed clinical latency and now has opportunistic diseases (AIDS)

Question 9

What stages of HIV replication are anti-retroviral drugs directed against?

Answer 9

• at all stages
  Nucleoside analogue RT inhibitors = stop transcription in growing DNA
  Non

Question 10

What are some ways in which HIV transmission to laboratory personnel can be prevented?

Answer 10

x

Question 11

What stages of HIV replication are anti-retroviral drugs directed against?

Answer 11

• at all stages
  Nucleoside analogue RT inhibitors = stop transcription in growing DNA
  Nonnucleoside RT inhibitors = directly bind to RT and inhibit its action
  Protease inhibitors = prevent cleavage of precursor proteins
  Fusion inhibitors = prevent entry of virus into host cell
  Coreceptor antagonists = prevent virus binding to chemokine
  Integrase inhibitor = block integeration of viral DNA into host genome

Question 12

What are some ways in which HIV transmission to laboratory personnel can be prevented? (10)

Answer 12

1. Universal precautions
2. Wear gloves, lab coats, and face sheilds
3. Wash hands immediately after contamination
4. Do not mouth pipet
5. Use biological safety cabinets
6. Use precautions when handling needles
7. Clean blood spills immediately
8. Disposed contaminated disposable material in designated biohazard bags
9. Decontaminate reusable equipment before reuse
10. Wash hands and remove lab coats before leaving the lab