Topic 6 - HIV & AIDS

Question 1

Describe how HIV invades T helper cells

Answer 1

– The glycoprotein GP120 on the virus surface, binds to CD4 receptors on the T helper cells
- The envelope surrounding virus fuses with the cell membrane
- HIV capsid containing viral mRNA enters the cell

Question 2

Why can HIV also infect macrophages as well as T helper cells?

Answer 2

They also have CD4 receptors, so the GP120 molecule can also bind to macrophages

Question 3

Describe what happens after HIV has entered the T helper cell

Answer 3

– New viral components need to be replicated
– the RNA must be converted into DNA copy by reverse transcript days
– DNA copy is integrated into hosts genome by viral enzyme integrase
- viral DNA is then transcribed and translated to produce new viral proteins

Question 4

How does HIV destroy T helper cells?

Answer 4

– Once the new viral RNA genome, enzymes and capsid proteins are made they are assembled into new virus particles
– The GP120 is packaged by the Gogi into the vesicle and sent to T helper cell
– as the New virus particle buds out of the cell some of the host cell membrane, with the GP120, envelopes the particle
– The host T helper cell dies

Question 5

What is the consequence of destroyed T helper cells on the immune system?

Answer 5

– The infected T helper cells are also killed by T killer cells
– which means macrophages, B cells and T killer cells are unable to be activated and function properly
– the immune system becomes deficient

Question 6

What determines the speed of development of AIDS?

Answer 6

– health of host before the infection
– the genetic resistance or infection
– the quality of their immune response to infection
– their lifestyle
– the nutritional status

Question 7

Describe the acute phase of AIDS

Answer 7

– HIV antibodies appear in blood after 3 to 12 weeks
– person may experience fever, sweats, headache
– there is rapid replication of new virus particles and loss of T helper cells
– infected T helper cells are identified by T killer cells and killed

Question 8

Describe the chronic phase of AIDS( also known as latent phase)

Answer 8

• virus replicates rapidly but the immune system keeps numbers in check
• Maybe no symptoms apart from more colds and minor infections (TB and shingles can reactivate)

Question 9

Describe the disease phase of AIDS

Answer 9

• eventually an increased viral load and significant reduction in T helper cell count indicates the onset of AIDS
• The immune system is now vulnerable to opportunistic infections like TB and pneumonia
• Development of the symptoms can lead to death

Question 10

What are the drugs used to treat in HIV infection collectively known as?

Answer 10

Antiretroviral drugs

Question 11

What are the three main types of antiretroviral drugs and describe how they work?

Answer 11

1. Reverse transcripts inhibitors – prevents the viral RNA from making DNA.
2. Integrase inhibitors – prevent viral DNA from integrating into host DNA, preventing latency.
3. Protease Inhibitors – inhibits protein is that catalyses the cutting of larger proteins into smaller polypeptides.

Question 12

Why are the drugs given in combination?

Answer 12

HIV can develop resistance, if virus becomes resistant to one drug it may still be susceptible to the other drugs being taken