HIV Pathophysiology Overview

Human Immunodeficiency Virus (HIV)

• HIV is a retrovirus, meaning its genetic material is RNA
• HIV has 2 major strains: HIV-1 (most common in the US) and HIV-2 (primarily in West Africa)
• HIV is a slowly progressive disease with 3 stages: Retrovirus, Acute HIV, and Chronic HIV leading to AIDS.
• Transmission routes include blood, semen, vaginal fluids, transplacental transmission, and breast milk. HIV must enter the bloodstream through mucous membranes (rectum, vagina, mouth, tip of penis, open cuts) or direct injection. Saliva might transmit HIV with open mouth wounds.
• HIV attacks CD4 cells and macrophages. CD4 cells are crucial for both humoral and cell-mediated immune responses.
• Macrophages serve as virus reservoirs, aiding in its spread, thus going undetected. They are found in mucous membranes.
• HIV slowly weakens the body's immune system, affecting T cells and B cells.

HIV Pathophysiology

• HIV fuses with a CD4 cell receptor.
• Reverse transcriptase converts viral RNA into DNA, which is then incorporated into the host cell's DNA.
• Integrase allows viral DNA to integrate into the host cell's DNA.
• The host cell then produces viral particles.
• Protease assists in assembling protein components for new viruses.
• The host cell becomes a viral production factory.
• The virus buds off from the host cell, destroying it and weakening the immune response.

Stages of HIV Infection

• Acute infection: Presents like a flu-like virus, similar to mononucleosis. Symptoms include fever, headache, fatigue, pharyngitis, lymphadenopathy, myalgia (muscle aches), and GI symptoms. This phase lasts a couple of weeks and often resolves. Symptoms are often mistaken.
• Chronic infection: Known as the latent stage, symptoms are often mild or absent. This stage can last from 6 months to 10 years. Symptoms can include malaise, headache, neuropathy, lymphadenopathy (swollen lymph nodes), and opportunistic infections.
• AIDS (Acquired Immunodeficiency Syndrome): The most advanced stage, marked by a severely compromised immune system. CD4 cell count drops to 200 cells/mm3 or less. Opportunistic infections and cancers become common. Symptoms include rapid weight loss, recurring fever, night sweats, rash (usually non-itchy on torso), prolonged swelling of lymph nodes, neurological issues, eye problems, lung complications, tumors, and opportunistic infections.

Risk Factors for HIV

• Unprotected sexual activity (heterosexual females at higher risk than males)
• Men who have sex with men (MSM), anal intercourse (receptive partners at higher risk)
• IV drug use
• History of STDs
• Frequent blood transfusions
• Offspring of infected mothers (during pregnancy and breastfeeding)

Clinical Manifestations (AIDS)

• Symptoms include: progressive weight loss, recurring fever, night sweats, a non-itchy rash (commonly on the torso), swollen lymph nodes, and opportunistic infections and cancers.

Treatment and Management of HIV

• Currently, antiretroviral therapy (ART) is the only effective long-term treatment. It targets the virus at various stages (e.g., protease inhibitors, transcriptase inhibitors, integrase inhibitors).
• Early initiation of ART is crucial for preserving immune function and reducing complications.

Laboratory Studies and Diagnostics

• Screening for HIV is vital.
• HIV RNA blood test detects the presence of the virus.
• CD4 count monitors the course of the disease. A normal range is 800-1200, and a count below 500 indicates impaired immunity.
• Viral load measures the amount of HIV in the blood. High viral loads can increase the risk of transmission.
• HIV antibody tests detect antibodies produced to fight HIV. It can take 2 weeks to 6 months for antibodies to develop.

Complications of HIV/AIDS

• Opportunistic infections (e.g., tuberculosis, candidiasis, pneumonia)
• Cancers (e.g., Kaposi sarcoma, lymphoma)
• Other complications (e.g., neurological issues, heart strain, gastrointestinal problems, skin disorders)

Practice Questions and Answers (Page 4)

• Question 1: Highest risk factors for HIV transmission
  • A: Transmission to women or men during sexual intercourse
  • B: First 2-6 months of infection is higher risk vs 1 year after infection
  • C: Perinatal transmission from HIV-infected mothers without ARV is higher than mothers on ARV
  • D: Needle stick exposure to HIV-infected blood is a higher risk than a splash exposure.
• Question 2: Reason for immune system failure
  • A: CD4+ T cells become infected and are destroyed.

This quiz explores the pathophysiology of HIV, including its classification as a retrovirus and its effects on the immune system. Learn about the different strains of HIV, transmission routes, and how it gradually progresses to AIDS. Understand the significance of CD4 cells and macrophages in the context of HIV infection.