L4_Immunology of HIV

Question 1

Explain the terms a) primary immunodeficiency & b) secondary immunodeficiency.

Answer 1

a) genetic basis and usually rare.

b) used to have a normal immune system but acquired immunodeficiency (bc of chemotherapy, HIV etc.) and common.

Question 2

What is the structure of HIV?

Answer 2

• double stranded RNA virus.

- its genome only contains 3 genes and can encode around 9 different proteins.

Question 3

How does HIV infect a T cell and produce virions?

Answer 3

• GP120 on HIV virus envelope will interact with TCR of a CD4 cell.
• this allows the viral genetic material to enter the CD4 cell.
• the reverse transcriptase changes the viral RNA to pro-viral DNA.
• it will enter the host genome using the enzyme integrase.
• in the CD4 cells it will produce virions.

Question 4

Name the two methods via which CD4 levels drop in a HIV infected individual.

Answer 4

• programmed cell death (apoptosis).

- T cell suicide (pyroptosis).

Question 5

Describe pyroptosis.

Answer 5

• a more inflammatory form of apoptosis.

Question 6

Why are antibody levels low during acute HIV infection?

Answer 6

• this is bc the body’s immune defence against HIV is primarily driven by a cell-mediated response, whereas the humoral response occurs later in the infection.

Question 7

What role do CD8 cytotoxic T cells play in an HIV infection?

Answer 7

• CD8 cytotoxic T cells kill virus infected host cells i.e. infected CD4 cells.

Question 8

Why are antibodies less useful in fighting off an HIV infection?

Answer 8

• due to HIV’s antigenic diversity.