Overview
This lecture discusses the three phases of HIV infection, the progression to AIDS, common opportunistic infections, and diagnostic methods for HIV.
Phases of HIV Infection
- Phase 1: Asymptomatic or chronic swollen lymph nodes (chronic lymphadenopathy) after primary infection.
- Phase 2: Persistent health decline with increased vulnerability to infections due to a weakening immune system.
- Phase 3: HIV infection progresses to AIDS once CD4 T cell count drops below 200 cells/μL or 14% of normal.
Acute HIV Syndrome and Immune Response
- After infection, acute HIV syndrome causes a rapid drop in CD4 T cell count and spike in viral load.
- Seroconversion (full antibody response) takes up to three months.
- Once antibodies develop, viral load drops and CD4 T cell count partially recovers, then steadily declines over years.
Constitutional Symptoms and AIDS
- Near end of Phase 2, "constitutional symptoms" appear: fever, night sweats, chills, and weight loss.
- AIDS is diagnosed when CD4 T cells fall below 200/μL; opportunistic diseases begin to occur.
Opportunistic Infections in AIDS
- Toxoplasma gondii can cause encephalitis in immunocompromised individuals.
- Cytomegalovirus (CMV) may cause encephalitis, blindness, or death.
- Tuberculosis (Mycobacterium tuberculosis) is more severe in HIV/AIDS patients.
- Pneumocystis pneumonia, yeast infections, and Kaposi's sarcoma are common in AIDS.
- AIDS patients die from infections due to complete loss of immune function.
Diagnosis of HIV
- Initial screening uses ELISA to detect HIV antibodies (may take months for seroconversion).
- Confirmation is done with Western blot or the AB tema (RNA test) to detect the virus directly.
Key Terms & Definitions
- HIV (Human Immunodeficiency Virus) — Virus that attacks the immune system, especially CD4 T cells.
- AIDS (Acquired Immunodeficiency Syndrome) — Final stage of HIV infection marked by severe immune deficiency (CD4 < 200/μL).
- CD4 T Cells — White blood cells crucial for immune defense.
- Seroconversion — Development of detectable antibodies to HIV.
- Opportunistic Infection — Illnesses that occur more frequently in people with weakened immune systems.
- ELISA — Blood test used to detect HIV antibodies.
- Western Blot/AB tema — Tests to confirm HIV infection by detecting the virus.
Action Items / Next Steps
- Review the list of opportunistic infections associated with AIDS.
- Study the diagnostic steps for detecting and confirming HIV infection.