AIDS (acquired immunodeficiency syndrome)

AIDS Definition

• AIDS is a chronic, life-threatening condition caused by the Human Immunodeficiency Virus (HIV).
• HIV destroys CD4 cells (T-helper cells), weakening the immune system and making the body vulnerable to opportunistic infections and cancers.

Stages of HIV Infection

1. Acute HIV Infection:

   • Timeline: 2-4 weeks after exposure.
   • Symptoms: Flu-like symptoms (fever, swollen glands, sore throat, rash, muscle/joint aches, mouth ulcers).
   • Significance: High viral load, highly infectious.

2. Clinical Latency Stage:

   • Timeline: Can last for years or decades.
   • Symptoms: Often asymptomatic or mild symptoms. Virus continues to replicate at low levels.
   • Significance: HIV is still active and transmissible.

3. AIDS:

   • Timeline: Progresses when the immune system is severely weakened.
   • Symptoms: Severe weight loss, fever, night sweats, extreme fatigue, swollen lymph glands, prolonged diarrhea, sores (mouth, anus, genitals), pneumonia, neurological issues (memory loss, depression).
   • Diagnosis Criteria: CD4 count below 200 cells/mm³, or presence of specific opportunistic infections or cancers (e.g., Kaposi’s sarcoma, non-Hodgkin’s lymphoma).

Transmission

• HIV is transmitted through contact with bodily fluids from an infected person, primarily through:
  1. Unprotected Sexual Contact: Vaginal, anal, or oral sex without protection.
  2. Sharing Needles or Syringes: Among people who inject drugs.
  3. Mother-to-Child Transmission: During pregnancy, childbirth, or breastfeeding.
  4. Contaminated Blood Transfusions or Organ Transplants: Though rare in countries with strict blood screening protocols.

Symptoms

• The symptoms of AIDS are primarily due to opportunistic infections and cancers that the weakened immune system can no longer combat effectively.
• Common symptoms include:
  1. Rapid Weight Loss: Unintentional and significant weight reduction.
  2. Recurring Fever or Profuse Night Sweats: Persistent and often severe.
  3. Fatigue: Extreme and unexplained tiredness.
  4. Prolonged Swelling of the Lymph Glands: Especially in the neck, armpits, and groin.
  5. Persistent Diarrhea: Lasting more than a week.
  6. Sores: In the mouth, genitals, or anus.
  7. Pneumonia: Frequent and severe lung infections.
  8. Neurological Disorders: Memory loss, depression, and other cognitive or motor dysfunctions.

Treatment

1. No cure, but treatment can control the virus and extend life.

   1. Antiretroviral Therapy (ART):

      1. Combination Therapy: Involves taking a combination of antiretroviral drugs to reduce the viral load, maintain a higher CD4 cell count, and delay the progression to AIDS.
      2. Goals: To suppress viral replication, improve immune function, and reduce the risk of transmission.

   2. Managing Opportunistic Infections and Complications:

      1. Antibiotics, Antifungals, and Antivirals: To treat infections like tuberculosis, Pneumocystis pneumonia, and others.
      2. Regular Monitoring: Frequent blood tests to monitor viral load and CD4 count.
      3. Preventive Measures: Vaccinations and prophylactic medications to prevent infections.

Preventive Measures:

1. Safe Sex Practices: Consistent and correct use of condoms.
2. PrEP (Pre-Exposure Prophylaxis): Medication for HIV-negative individuals at high risk.
3. PEP (Post-Exposure Prophylaxis): Emergency treatment within 72 hours of potential exposure.
4. Needle Exchange Programs: For people who inject drugs.
5. Regular Testing: For early detection and treatment.

Etiology

• Causative Agent: Human Immunodeficiency Virus (HIV), a retrovirus that integrates into the host genome and targets CD4 cells.
  1. HIV-1: Most common and virulent, prevalent worldwide.
  2. HIV-2: Less common, found primarily in West Africa, slower progression to AIDS.

Major Abnormalities in the Immune System

1. CD4 Cell Depletion: Continuous viral replication destroys CD4 cells, weakening the immune system.
2. Impaired Cell-Mediated Immunity: Loss of CD4 cells disrupts immune coordination.
3. Opportunistic Infections: The weakened immune system can’t fight common infections.
4. Increased Cancer Risk: Weak immune response increases cancer risk (e.g., Kaposi’s sarcoma, non-Hodgkin’s lymphoma).

HIV Life Cycle

• The HIV life cycle includes several key stages:

1. Attachment and Entry:

   • HIV attaches to the CD4 receptor on CD4 cells using its surface glycoprotein, gp120.
   • The virus binds to a co-receptor (CCR5 or CXCR4), enabling fusion with the host cell membrane.
   • The viral capsid containing RNA and enzymes enters the host cell.

2. Reverse Transcription:

   • The viral enzyme reverse transcriptase converts single-stranded viral RNA into double-stranded DNA.

3. Integration:

   • The viral DNA is transported to the nucleus, where integrase incorporates it into the host cell’s genome, forming a provirus.

4. Transcription and Translation:

   • The host cell machinery transcribes the integrated viral DNA into RNA, which is then translated into viral proteins.

5. Assembly and Budding:

   • Viral RNA and proteins assemble at the host cell membrane, forming immature virus particles.
   • These particles bud off from the host cell, acquiring a lipid envelope.

6. Maturation:

   • The viral enzyme protease cleaves viral polyproteins into functional proteins, maturing the virus particles, making them infectious.

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