Human Immunodeficiency Virus (HIV)

Question 1

Describe the structure of HIV.

Answer 1

1. Capsid: a protein coat which contains RNA and an enzyme called reverse transcriptase
2. Envelope: made up of lipids
3. Antigen: glycoprotein molecules (attachment proteins) which can trigger an immune response

Question 2

How is HIV transmitted?

Answer 2

• via sexual intercourse
• blood to blood contact
• mother to baby via the umbilical cord
  HIV infects T cells by replicating inside the cells and rupturing the host cell membrane. This kills the host cell.

Question 3

Describe the replication of HIV in TH cells.

Answer 3

1. Antigens on the virus bind to complementary receptor proteins in the TH cell membrane.
2. HIV’s lipid envelope fuses with the TH cell membrane. This releases the capsid into the cell.
3. RNA and reverse transcriptase are released from the capsid.
4. RNA and reverse transcriptase are used to make viral proteins.
5. New viral proteins are assembled to make new viruses. These bud out of the cell causing the TH cell to rupture and die.
6. New viruses go on to infect other TH cells.

Question 4

Describe and explain the symptoms of HIV.

Answer 4

-Initially, HIV causes flu like symptoms (fever, headaches, joint pains, and sore throat)
-Immune system causes a primary immune response which kills many of the HIV particles. However, some remain inside TH cells for many years without causing the person any symptoms.
-When HIV becomes activated, many helper T cells will be killed causing T cell account in blood to decrease.
-This weakens the immune system and causes AIDS, a collection of infections such as: pneumonia, tuberculosis, parasitic infections, fungal infection and extreme weight loss.

The lower the blood T cell count, the worse the symptoms are.

Question 5

Why are antibiotics ineffective at treating HIV?

Answer 5

Antibiotics kill bacteria by interfering with their metabolic rate, by targeting their bacterial enzymes and ribosomes.

Viruses do not have their own bacterial enzymes and ribosomes so are not killed by antibiotics.

Question 6

What are anti-viral drugs?

Answer 6

They target the enzymes inside viruses, eg. Reverse transcriptase.

HIV needs reverse transcriptase to replicate inside host cells so drugs called reverse transcriptase inhibitors will prevent HIV from replicating whiteout the drug affecting the host cell.