Understanding HIV and AIDS

• These notes discuss HIV (Human Immunodeficiency Virus), AIDS (Acquired Immunodeficiency Syndrome), their differences, and related information.

HIV and AIDS Distinction

• HIV is the virus causing HIV infection, which damages the immune system by targeting CD4 cells.
• AIDS is the advanced stage of HIV infection, marked by increased viral load and decreased CD4 cell count.
• Without treatment, HIV can progress to AIDS in approximately 10 years.

Human Immunodeficiency Virus (HIV)

• HIV belongs to the Retroviridae family.
• HIV causes AIDS.
• Two serogroups exist: HIV-1, the common global strain, and HIV-2, mainly in West Africa.
• HIV-1 has subtypes M (major), N, and O.

HIV Replication Process

• HIV binds to the CD4 molecule on T helper cells, monocytes, macrophages, and other cells, with co-receptors aiding viral binding.
• HIV enters the cell via the plasma membrane, releasing its RNA.
• Viral RNA converts to DNA using reverse transcriptase, then integrates into the host cell's DNA through integrase.
• Viral DNA transcribes into mRNA, which translates into viral proteins, leading to virus production and budding from the host cell.
• Replication kills infected T helper cells, reducing their number.
• HIV targets T helper cells, making it difficult to cure or vaccinate because the virus hijacks the body's cellular immune response.
• Replication steps: binding, fusion, reverse transcription, integration, replication, assembly, budding.

Immune Response and HIV

• Antibodies to HIV appear around 12 weeks post-infection, detected by ELISA and Western blot assays.
• Neutralizing antibodies appear about 1 year post-infection, interfering with host cell infection but not providing full protection.
• HIV escapes immune response by antigenic variation or mutations.
• HIV escapes cell death by mutating and altering cytokine production patterns.

Effects on T Cells

• CD4+ T helper cells deplete as the disease progresses, worsening immune deficiency.
• HIV compromises immune response by destroying T helper cells.
• CD4 and CD8 cells crucial to immune response are affected, suppressing the immune system.
• Viral load tests monitor HIV in the blood, while CD4 lymphocyte cell counts assess the impact on the immune system.
• Additional effects include decreased natural killer cell activity and defective chemotaxis, impacting immune response.
• Enhanced release of interleukin-1 and cachectin by monocytes occurs.
• The ratio of CD4 to CD8 cells reduces from the normal 2:1 ratio.

Epidemiology

• HIV-1 spreads through unprotected sex, contaminated blood/products, contaminated needles, or perinatally.
• In the U.S., AIDS is the leading cause of death for individuals aged 20-35.

Symptoms

• Initial acute phase may be asymptomatic or show mononucleosis-like symptoms.
• The virus replicates in lymphoid tissue during clinical latency.
• As T cells decrease, opportunistic infections like Candida albicans and herpes simplex virus occur, known as AIDS-related complex (ARC).
• The final stage (full-blown AIDS) involves severe opportunistic infections and cancers due to T cell depletion.
• Staging disease severity uses CD4+ T cell counts and opportunistic infections.

Laboratory Tests

• ELISA tests identify HIV antibodies and antigens, confirmed by Western blot or immunofluorescent tests.
• The Western blot assay confirms serological tests, requiring two of three bands (p24, gp41, gp120/160) to be positive.
• Genetic probes can detect replicating viruses.
• Reverse transcriptase-polymerase chain reaction assays identify nucleic acid gene sequences.
• Indirect immunofluorescence assays detect HIV antigens in infected cells and can confirm.

Treatment

• Retrovir (Zidovudine) offers hope by increasing survival time and decreasing mortality.
• Combination antiretroviral therapy, involving multiple drug classes, is now common.

Prevention

• Modify sexual behavior.
• Implement measures to protect blood/products: self-referral of high-risk groups, blood donor screening, and heating blood plasma at 68°C for 24 hours.
• Research for an effective vaccine continues.
• HIV mutates rapidly.