Establishment of an SIV/macaque model of HIV latency

HIV/AIDS is a global pandemic which has affected about 60 million people in the world. In the United States of America, with the development of Highly Active Anti-Retroviral Therapy (HAART), the biggest challenge in eradicating HIV is viral latency, particularly the latent reservoir in resting T lymphocytes. Therefore, a SIV/Macaque model was established to study viral latency. Assays were developed to detect latent SIV persisting in resting macaque CD4+ T cells. Pigtailed macaques were then infected with SIV/17E-Fr, a derivative of SIVmac239, and at viral set-point treated with PMPA and FTC. In treated animals, viremia was suppressed to below the limit of detection. The persistence of latent SIV was then demonstrated by the isolation of replication competent virus following activation of resting CD4+ T cells. In addition, integrated viral DNA was detected in both treated and un-treated animals, demonstrating the existence of a stable viral reservoir in the SIV/macaque system similar to HIV in humans. Various compartments were examined, and reservoirs were detected in blood, lymph nodes and spleen. No replication competent virus and only minimal levels of viral DNA were detected in the thymocytes, suggesting the thymus not being a source or a site of the latent reservoir. In the process of developing the animal model, a novel way to re-activate the latent virus was discovered. Several cell lines were determined to be able to activate resting cells and re-activate the latent virus, including CEMx174 and EBV transformed human B lymphocytes. TCR MHC class II interaction does not seem to be involved. Antibody blocking assays show that among the co-stimulatory molecules, CD58 is involved in the process, whereas CD80, CD86 and CD54 are not involved. The same cell lines do not re-activate HIV in human resting T cells. This is the first animal model to study HIV latency that closely resembles HIV patients on HAART. It is being used to evaluate the effect of therapeutic vaccines on latent reservoir, will be used to examine various tissue/organ compartments for latent reservoirs, and could possibly be used to test potential therapies to attack the reservoir.