MP Board · Class 12 · Biology · Human Health and DiseasesExplain AIDS (Acquired Immuno Deficiency Syndrome) with emphasis on its causative agent, mode of transmission, detailed replication process of HIV in the human host body, and methods of prevention.

Introduction and Causative Agent

AIDS stands for Acquired Immuno Deficiency Syndrome. It is caused by the Human Immunodeficiency Virus (HIV), which belongs to a group of viruses called Retroviruses. These viruses have an RNA genome enclosed within a protein coat.

Modes of Transmission

• Sexual contact with an infected person.
• Transfusion of contaminated blood and blood products.
• Sharing of infected needles and syringes among intravenous drug abusers.
• Transmission from an infected mother to her child through the placenta during pregnancy or during breastfeeding.

(Note: HIV does not spread through casual physical contact, touch, or hugging).

Replication Mechanism of HIV in Human Body

1. Entry into Host Cells: After entering the body, the virus binds to and enters macrophages and Helper T-lymphocytes ($T_H$ cells).
2. Reverse Transcription: The viral RNA genome uses the enzyme Reverse Transcriptase to synthesize viral DNA inside the host cytoplasm.
3. Integration: The viral DNA enters the host cell's nucleus and incorporates itself into the host cell's genome/DNA.
4. Viral Production: The infected host genome directs the cell to produce new viral RNA molecules and viral proteins. Thus, macrophages continue to act as an HIV factory.
5. Destruction of Helper T-cells: Newly formed viruses exit macrophages and attack new Helper T-lymphocytes ($T_H$ cells). The virus replicates continuously, leading to a progressive reduction in the number of Helper T-cells in the patient's body.
6. Immune Breakdown: Due to the severe decrease in $T_H$ cells, the person becomes immune-compromised and succumbs to opportunistic infections caused by bacteria (Mycobacterium), viruses, fungi, and parasites like Toxoplasma.

Diagnosis and Prevention

• Diagnosis: Commonly diagnosed using ELISA (Enzyme-Linked Immunosorbent Assay).
• Prevention & Control:
  • Advocacy and education by organizations like NACO (National AIDS Control Organisation) and WHO.
  • Ensuring the use of disposable needles and syringes.
  • Screening blood banks carefully before blood transfusions.
  • Promoting free distribution of condoms and safe sex practices.