HIV

Question 1

HIV preferentially kills what kind of cells leading to what?

Answer 1

Kills helper (CD4) T lymphocytes, resulting in the loss of cell mediated immunity.

Question 2

What does the genome of HIV consist of?

Answer 2

Two identical molecules of ss, positive-polarity RNA and is said to be diploid.

Question 3

What does positive sense RNA indicate?

Answer 3

mRNA that can be directly translated

Question 4

What does negative sense RNA indicate?

Answer 4

-ve sense RNA needs RNA-dependent RNA polymerase to make the positive strand before translation can occur.

Question 5

What are the three typical retroviral genes?

Answer 5

gag

pol

env

Question 6

The RNA genome has 6 regulatory genes; what two are required for replication and what four are accessory.

Answer 6

• Replication
  
  • tat
  • rev
• Accessory
  
  • nef
  • vif
  • vpr
  • vpu

Question 7

What does the gag encode?

Answer 7

• The “internal” core proteins; most importantly p24 protein.
  
  • P24 = it is the antigen in the initial serologic test that determines whether the patient has been infected with HIV.

Question 8

What does the pol gene encode?

Answer 8

• The virion “Reverse transcriptase” which synthesizes DNA using the genome RNA as a template.

An integrase that integrates the viral DNA into the cellular DNA.

Question 8

What does the pol gene encode?

Answer 8

• The virion “Reverse transcriptase” which synthesizes DNA using the genome RNA as a template.

An integrase that integrates the viral DNA into the cellular DNA.

Question 9

What are the three enzymes located within the nucleocapsid of the virion?

Answer 9

Reverse transcriptase, integrase, and protease.

Question 10

What is important about gp120?

Answer 10

• It protrudes from the surface and interacts with the CD4 receptor.
  
  • The gene that encodes this protein mutates rapidly, resulting in many antigenic variants.

Question 11

Describe antigen p24?

Answer 11

• Antibodies against p24 do not neutralize HIV infectivity but serve as important serologic markers of infection.
  
  • Located in the nucleocapsid core and not known to vary.

Question 12

Summary of gag products and their functions?

Answer 12

• Group-specific antigens → structural proteins
• p24 → capsid protein
• p17 → matrix protein

Question 13

Summary of pol products and their functions?

Answer 13

• Reverse transcriptase → Produces dsDNA provirus (extremely error prone).
• Integrase → Viral DNA integration into host cell DNA
• Protease → cleaves viral polyprotein

Question 14

Summary of env products and their functions?

Answer 14

• gp120 → surface protein that binds to CD4 and coreceptors CCR5 (macrophages and T-cells) and CXCR4 (T cells); tropism; genetic Drift
• gp41 → Transmembrane protein for viral fusion to host cell

Question 15

Loss of function of what two regulatory genes prevents the virus from replicating?

Answer 15

Tat and Rev