2.6.3 HIV

Structure of HIV:

1. Lipid Envelope:

• Surrounds the virus and contains attachment proteins, allowing the virus to bind to host cells.

2. Protein Capsid:

• Encloses the viral RNA and enzymes, including reverse transcriptase.

3. Genetic Material:

• HIV contains RNA as its genetic material, which is used to produce DNA once inside the host cell.

4. Enzymes:

• Reverse Transcriptase:
• Converts viral RNA into complementary DNA (cDNA), enabling integration into the host genome.

Replication of HIV:

5. Attachment and Entry:

• HIV binds to the CD4 receptor found on T helper cells using its attachment proteins.
• The capsid fuses with the host cell membrane, allowing the viral RNA and enzymes to enter the cell.

6. Reverse Transcription:

• Reverse transcriptase converts the viral RNA into DNA.

7. Integration:

• The viral DNA enters the host cell nucleus and integrates into the host's genome.

8. Protein Synthesis:

• The host cell uses its machinery to transcribe and translate the viral DNA into viral proteins and RNA.

9. Assembly and Release:

• New HIV particles are assembled and bud off from the host cell, acquiring their lipid envelope from the host cell membrane.
• The host cell is often destroyed in the process, reducing the number of T helper cells.

Progression to AIDS:

10. Effect on the Immune System:

• HIV destroys T helper cells, which are crucial for coordinating the immune response.
• As the number of T helper cells declines, the immune system becomes increasingly compromised.

11. Development of AIDS:

• AIDS occurs when the immune system is severely weakened, leading to an inability to fight opportunistic infections and cancers.
• Examples of opportunistic infections include tuberculosis (TB), pneumonia, and fungal infections.

Transmission of HIV:

1. Routes of Transmission:

• Unprotected sexual contact.
• Sharing contaminated needles.
• Blood transfusions with infected blood (rare in developed countries due to screening).
• From mother to baby during childbirth or breastfeeding.

2. Prevention:

• Safe sex practices (e.g., using condoms).
• Screening blood donations.
• Use of sterile needles.
• Antiretroviral therapy (ART) during pregnancy to reduce mother-to-child transmission.

Treatment of HIV:

3. Antiretroviral Therapy (ART):

• Involves a combination of drugs that target different stages of the HIV life cycle.
• Suppresses viral replication, slowing disease progression but does not cure HIV.

4. Challenges:

• HIV mutates rapidly, making it difficult to develop a vaccine.
• Long-term drug adherence is essential to prevent resistance.