Date of Presentation: December 1, World AIDS Day, by Prof. Bill Keevil.
Complex Relationship: HIV interacts uniquely with the immune system, causing significant immunosuppression over time.
Immune Response: Early on, the immune system responds vigorously to HIV, generating a powerful response that is typically effective against other viruses, but HIV's characteristics allow it to evade this response and persist.
CD4 T Cell Decrease: A hallmark of HIV infection is the gradual decline of CD4 T cell counts, indicating immunological disruption.
Additional Immune Changes: Other immune alterations occur, including changes in lymph nodes and T cell functionality.
Swollen Lymph Nodes: Common in HIV+ individuals during the initial infection phase.
Histological Findings: • Disruption of lymph node architecture, • Influx of CD8 T cells, • Loss of germinal centers.
Function of Dendritic Cells (DCs): Patrol tissues and present pathogen fragments to CD4 T cells, initiating immune responses.
HIV Exploitation: HIV is taken up by DCs and transported to lymph nodes to evade destruction.
Recognition Mechanism: The virus's GM3 ganglioside aids in its uptake by DCs, allowing it to circumvent immune detection.
Over the course of infection, HIV+ individuals exhibit a decline in CD4 T cell function, not solely explained by cell count reductions.
Transplant Comparison: Immunosuppressed transplant patients maintain better CD4 T cell function despite comparable cell loss.
Viraemia: Rapid viral replication leads to high blood virus levels.
CD8 T Cell Response: Strong response against HIV proteins (gp120, p24) noted.
Latency: The disease eventually enters a latent phase following the immune response.
New methods reveal persistent active viral replication even during lew latency periods.
Prognostic Indicator: Low viral RNA levels correlate with slower disease progression.
Structural Abnormalities: Lymph node damage becomes more pronounced as the disease progresses.
HIV's Survival Tactics: High replication and mutation rates; hiding as a provirus; evasion of immune detection through rapid antigenic changes.
Direct HIV-induced cell death and immune-mediated destruction of infected CD4 cells.
Soluble gp120 Presence: High levels in the blood contribute to CD4 T cell death through various mechanisms.
Direct Lysis: HIV can directly lyse CD4 T cells.
Antibody-Dependent Mechanisms: Infected cells may be targeted by antibodies and other immune cells (e.g., NK cells).
Cytotoxic Response: CD8 T cells target infected cells presenting viral antigens.
Apoptosis: A process seen in HIV-infected, permissive CD4 T cells following full infection.
Pyroptosis: Mediated by caspase-1 in abortively infected CD4 T cells, leading to inflammatory responses and attracting more CD4 T cells.
High Mutational Rates: Complicate treatment and create resistance to drugs.
Initial Drug Use: First introduced anti-HIV drug was zidovudine (AZT), but resistance developed quickly.
Combination Therapy: Effective use of multiple drugs reduces resistance rates and saves lives with estimated 2.9 million lives saved through Anti-Retroviral Therapy (ART).
Nucleoside Reverse Transcriptase Inhibitors (NRTIs): Insert themselves into viral DNA, terminating synthesis.
Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs): Bind to reverse transcriptase, inhibiting its function without attaching to DNA.
Protease Inhibitors: Prevent cleavage of viral proteins, inhibiting replication.
Clinical Effectiveness: Combination therapies improve patient outcomes and reduce viral loads but are associated with side effects.
Logistical Issues: Compliance with complex regimens and high costs limit access to necessary treatments, especially in low-resource settings.
Prophylactic Vaccines: Aim to protect uninfected individuals from HIV infection.
Therapeutic Vaccines: Intended to enhance immune responses in already infected individuals.
Immunological Complexity: High mutation rates and diverse subtypes complicate design.
Long Testing Durations: Chronic disease progression makes efficacy evaluation lengthy.
Overview: Initial identification of AIDS in 1981, strain isolation in 1983. HIV primarily infects CD4+ T cells, leading to immunosuppression.
Epidemiology and Current Statistics: 30 million individuals infected; vaccination and treatment strategies remain ongoing challenges.
Impact of Treatment: Although ART suppresses viral loads, it does not eliminate infection due to mechanisms like Vif targeting interferon responses.
Future Directions: Together with therapeutics, innovative strategies like microbiocides and pyroptosis inhibitors may advance treatment protocols.