HIV & AIDS

HIV & AIDS Overview

  • HIV: Infectious disease caused by the Human Immunodeficiency Virus, affecting the immune system.

  • AIDS: Acquired Immunodeficiency Syndrome, representing the most advanced stage of HIV infection.

Human Immunodeficiency Virus

  • Transmission Methods:

    • Body fluids via:

      • Sexual contact

      • Blood-to-blood contact, including:

        • Contaminated needles

        • Blood transfusions

        • From mother to child during pregnancy, birth, or via breast milk

  • Infectiousness: Patients can transmit the virus even when asymptomatic.

Characteristics of HIV

  • Type of Virus: Retrovirus

  • Genetic Material: Carries RNA instead of DNA

  • Strains of HIV:

    • HIV-1 - most common in America; more aggressive

    • HIV-2 - mainly found in West Africa; same pathophysiology as HIV-1 but spreads slower

  • Target Cells: Infects CD4+ T helper cells.

HIV Infection & Replication Process

  1. Attachment: Virus binds to CD4+ receptors on host cells

  2. Internalization: Virus enters the host cell

  3. Reverse Transcription: Converts RNA to DNA using reverse transcriptase

    • For it to reproduce, it has to change from the 2 RNAs to 2 strands of DNA through reverse transcriptase

  4. Integration: Viral DNA integrates into host genome

    • The newly formed viral DNA enters the nucleus

    • Viral enzyme integrate inserts HIV DNA into the host’s genome

    • Once integrated, HIV becomes a permanent part of the cell

      • This is why HIV cannot be cured and virus can stay latent (inactive for years)

  5. Transcription: Host machinery transcribes integrated viral DNA

  6. Translation: Viral RNA is translated into proteins

    • Host ribosomes translate viral mRNA into long, immature protein chains including:

      • Structural proteins

      • Enzymes (protease, reverse transcriptase, integrase)

  7. Cleavage: Proteins are cleaved into functional units by protease

    • Proteins have to be cut because long proteins cannot penetrate the cells

  8. Assembly and Release: New virions are assembled and exported from the host cell


Attach → Enter → Copy → Hide → Read → Build → Cut → Escape

Life Cycle of HIV in a Cell

  • Steps 1-3 (HIV Infects a Cell):

    • Binding of HIV to CD4 receptor

    • Reverse transcriptase function in converting viral RNA to DNA

  • Steps 4-8 (Infected Cell Produces New HIV):

    • Polyprotein processing by protease

    • Dormancy potential in the host genome for years before activation

    • Production of long, stringy polyproteins followed by cleavage into subunits

    • Assembly into new virus particles

Clinical Course of HIV Infection

  1. Primary Infection Phase:

  • Duration varies; window period where signs of systemic infection occur

  • Seroconversion happens within 1-6 months, where antibodies appear

  • Virus is replicating, resulting in gradual T cell count decline

  1. Latency Phase:

    • May last 10-11 years

    • Characterized by asymptomatic state or lymphadenopathy

  2. Overt AIDS Phase:

  • CD4 count drops below 200 cells/μL or development of AIDS-defining illnesses

  • Without treatment, prognosis may be 2-3 year


Key Metrics: CD4 count and viral load help monitor disease progression

  • Normal CD4 count = 800-1000

Symptoms in Each Stage of Disease

  • Primary Infection Stage:

    • Symptoms resemble acute mononucleosis

  • Latent Stage:

    • Asymptomatic or presents lymphadenopathy

Main Symptoms of AIDS

  • Neurological:

    • Encephalitis

    • Meningitis

  • Eyes:

    • Retinitis

  • Lungs:

    • Pneumocystis pneumonia

    • Tuberculosis (may affect multiple organs)

  • Skin:

    • Tumors

  • Gastrointestinal:

    • Esophagitis

    • Chronic diarrhea

    • Tumors

  • AIDS-Defining Illnesses:

    • Opportunistic infections

    • Malignancies

    • Wasting syndrome

Diagnostic Tests for HIV

  • HIV Antibody Tests:

    1. ELISA (Enzyme-Linked Immunosorbent Assay): Used for screening test

    2. Western Blot: Confirmatory test if ELISA positive

  • Polymerase Chain Reaction (PCR):

    • Detects presence of HIV DNA instead of antibodies

    • Also used on infants/children up to 18 months

  • CD4 Count/T-cell Count:

    • Used to monitor immune system impact


Testing Differences: Diagnostic procedures may differ for adults vs. infants

Treatment for HIV/AIDS

  • Cure Status: Currently, no cure for HIV/AIDS

  • HAART: Highly Active Antiretroviral Therapy

    • Composed of a 3-drug combination (e.g., emtricitabine, tenofovir, ritonavir)

    • Goals: Suppress HIV replication (lower viral load and increase CD4 count)

    • Notable significant side effects

  • Other Treatments:

    • Medications and vaccines to prevent and/or treat opportunistic infections

    • PrEP: Pre-Exposure Prophylaxis as a preventive measure

Anti-HIV Medication Mechanisms

  • Target Sites:

    1. Binding and entry inhibitors

    2. Reverse transcription inhibitors

    3. Integration inhibitors

    4. Transcription inhibitors

    5. Assembly inhibitors

    6. Release and protease inhibitors

HIV Considerations in Pregnancy, Infants & Children

  • Reducing Transmission:

    • Administering zidovudine to mother during pregnancy, labor, delivery, and to the infant post-birth

  • Counseling and Testing:

    • Offered to all pregnant women

  • Child-Specific Patterns:

    • Failure to thrive

    • Central nervous system (CNS) abnormalities

    • Developmental delays

    • Lower weight

    • Higher incidence of Pneumocystis pneumonia (PCP) compared to adults

Stigma and Community Perspective on HIV

  • Stigma: The concept of U=U (Undetectable = Untransmissible) as a public health message

  • Prevention Strategies:

    • PrEP: Pre-Exposure Prophylaxis

    • PEP: Post-Exposure Prophylaxis