HIV cure research

The HIV Reservoir - Hiding in Plain Sight

• What: A pool of long-lived, resting memory CD4+ T cells (and other cells like macrophages) harboring integrated but transcriptionally silent HIV provirus.
• Mechanism: HIV DNA hides within the host cell's genome, remaining dormant and invisible to the immune system.
• Problem: Standard antiretroviral therapy (ART) only targets actively replicating virus. It cannot eliminate this latent reservoir, which can reactivate and produce new virus if ART is stopped.

⭐ The half-life of the latent reservoir is estimated to be over 44 months, making it the primary barrier to a cure.

Shock and Kill - Luring Out the Enemy

The "Shock and Kill" strategy aims to eliminate the latent HIV reservoir in a two-step process.

• Step 1 (Shock): Use Latency-Reversing Agents (LRAs) to force latent HIV out of its dormant state in CD4+ T-cells.
  • Examples: HDAC inhibitors (e.g., Vorinostat), PKC agonists (e.g., Prostratin).
• Step 2 (Kill): Once reactivated, the infected cells become visible to the immune system and are destroyed, or are killed by Antiretroviral Therapy (ART).

⭐ A major challenge is that no single LRA can reactivate all latent proviruses without causing global, toxic T-cell activation.

Gene & Cell Therapy - Snipping and Swapping

• Primary Goal: To permanently alter host cells, making them resistant to HIV or enabling them to eliminate the integrated provirus.

• Gene Therapy (e.g., CRISPR-Cas9):

  • Aims to "snip" out the integrated HIV proviral DNA from the host cell's genome.
  • Alternatively, it can disable the gene for the CCR5 co-receptor, which is essential for the entry of R5-tropic HIV strains.

• Cell Therapy (Stem Cell Transplant):

  • Involves transplanting hematopoietic stem cells from a donor with a natural resistance to HIV.
  • The classic example uses donors homozygous for the CCR5-delta32 mutation.

⭐ The 'Berlin patient' (Timothy Ray Brown) is the first person considered cured of HIV, following a hematopoietic stem cell transplant from a CCR5-delta32 homozygous donor.

Immunotherapy - Boosting Host Defenses

• Broadly Neutralizing Antibodies (bNAbs):

  • Potent antibodies that recognize and neutralize diverse HIV strains.
  • Mediate clearance of infected cells via antibody-dependent cell-mediated cytotoxicity (ADCC).
  • Engineered for longer half-lives and greater potency.

• Therapeutic Vaccines:

  • Aim to induce a potent and broad anti-HIV immune response in infected individuals.
  • Goal: Enable long-term, ART-free viral control or clearance, unlike preventative vaccines which aim to block initial infection.

⭐ Infusions of bNAbs have been shown to delay viral rebound after stopping ART, demonstrating their potential for long-term remission.

High‑Yield Points - ⚡ Biggest Takeaways

• The main barrier to an HIV cure is the latent reservoir in resting CD4+ T-cells.
• "Shock and kill" uses Latency Reversing Agents (LRAs) to reactivate latent HIV for immune clearance.
• "Block and lock" aims for a functional cure by permanently silencing HIV transcription.
• Gene therapy (e.g., CRISPR-Cas9) targeting the CCR5 co-receptor prevents viral entry.
• Broadly neutralizing antibodies (bNAbs) can provide long-term viral suppression off-ART.
• Therapeutic vaccines seek to improve immune control over HIV.