Definition of AIDS
AIDS (acquired immunodeficiency syndrome) is a chronic, potentially life-threatening condition caused by the Human Immunodeficiency Virus (HIV).
HIV targets and destroys the immune system's CD4 cells (T-helper cells), which are crucial for mounting an immune response against infections and diseases.
As the immune system becomes progressively weakened, the individual becomes vulnerable to opportunistic infections and certain types of cancers.
Stages of HIV Infection
1. Acute HIV Infection:
Timeline: Occurs within 2 to 4 weeks after initial exposure to the virus.
Symptoms: Flu-like symptoms, such as fever, swollen glands, sore throat, rash, muscle and joint aches, headache, and mouth ulcers. This stage is also known as acute retroviral syndrome (ARS) or primary HIV infection.
Significance: High levels of HIV are present in the blood, making the person highly infectious.
2. Clinical Latency Stage:
Timeline: Can last several years to decades.
Symptoms: Often asymptomatic or mild symptoms. The virus continues to reproduce at low levels.
Significance: Although there are no or few symptoms, HIV is still active and can be transmitted. This phase is also known as chronic HIV infection or asymptomatic HIV infection.
3. AIDS:
Timeline: Progression to AIDS occurs when the immune system is severely damaged.
Symptoms: Severe symptoms including rapid weight loss, recurring fever or profuse night sweats, extreme and unexplained tiredness, prolonged swelling of the lymph glands, diarrhea that lasts for more than a week, sores of the mouth, anus, or genitals, pneumonia, and neurological disorders such as memory loss and depression.
Diagnosis Criteria: CD4 cell count drops below 200 cells/mm³, or the presence of specific opportunistic infections or cancers such as Kaposi's sarcoma and non-Hodgkin's lymphoma.
Transmission
HIV is transmitted through contact with certain bodily fluids from an infected person.
Common modes of transmission include:
Unprotected Sexual Contact: Vaginal, anal, or oral sex without protection.
Sharing Needles or Syringes: Among people who inject drugs.
Mother-to-Child Transmission: During pregnancy, childbirth, or breastfeeding.
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:
Rapid Weight Loss: Unintentional and significant weight reduction.
Recurring Fever or Profuse Night Sweats: Persistent and often severe.
Fatigue: Extreme and unexplained tiredness.
Prolonged Swelling of the Lymph Glands: Especially in the neck, armpits, and groin.
Persistent Diarrhea: Lasting more than a week.
Sores: In the mouth, genitals, or anus.
Pneumonia: Frequent and severe lung infections.
Neurological Disorders: Memory loss, depression, and other cognitive or motor dysfunctions.
Treatment
While there is currently no cure for AIDS, treatment can help control the virus and enable individuals to live healthier, longer lives.
A. Antiretroviral Therapy (ART):
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.
Goals: To suppress viral replication, improve immune function, and reduce the risk of transmission.
B. Managing Opportunistic Infections and Complications:
Antibiotics, Antifungals, and Antivirals: To treat infections like tuberculosis, Pneumocystis pneumonia, and others.
Regular Monitoring: Frequent blood tests to monitor viral load and CD4 count.
Preventive Measures: Vaccinations and prophylactic medications to prevent infections.
Preventive Measures:
Safe Sex Practices: Using condoms consistently and correctly.
PrEP (Pre-Exposure Prophylaxis): Medication taken by HIV-negative individuals at high risk of infection to prevent acquiring HIV.
PEP (Post-Exposure Prophylaxis): Emergency treatment taken within 72 hours of potential HIV exposure.
Needle Exchange Programs: To reduce the risk among people who inject drugs.
Regular Testing: For early detection and treatment of HIV.
Etiology
AIDS is caused by the Human Immunodeficiency Virus (HIV), a retrovirus that integrates into the host genome and primarily targets CD4 cells.
There are two main types of HIV:
HIV-1: The more common and virulent form, prevalent worldwide.
HIV-2: Less common and primarily found in West Africa, generally associated with a slower progression to AIDS.
Major Abnormalities in the Immune System
HIV infection leads to several significant immune system abnormalities:
1. Depletion of CD4 Cells:
Continuous viral replication destroys CD4 cells, weakening the immune response.
2. Impaired Cell-Mediated Immunity:
Loss of CD4 cells disrupts the coordination of the immune response, affecting the body's ability to fight intracellular pathogens.
3. Susceptibility to Opportunistic Infections:
A weakened immune system cannot effectively combat infections, making individuals vulnerable to diseases that do not typically affect those with healthy immune systems.
4. Increased Risk of Certain Cancers:
The weakened immune system fails to control the growth of cancer cells, leading to a higher incidence of cancers like Kaposi's sarcoma and 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.
