Abstract
Marijuana is one of the most commonly used and abused drugs. Δ-9-tetrahydrocannabinol (Δ-9-THC), the primary psychoactive component in marijuana, is FDA-approved to ameliorate AIDS-associated wasting. Because cannabinoid receptors are expressed on cells of the immune system, it is possible that chronic Δ-9-THC use may impact HIV disease progression. Until recently, longitudinal, controlled, systems-approach studies on the effects of cannabinoids on disease progression were lacking. Data from our controlled studies in non-human primates show chronic Δ-9-THC administration prior to and during simian immunodeficiency virus (SIV) infection ameliorates disease progression, attenuates viral load and tissue inflammation, significantly reducing morbidity and mortality of SIV-infected macaques. Identification of possible mechanisms responsible for this modulation of disease progression is complicated due to the multiplicity of cannabinoid-mediated effects, tissue-specific responses to the viral infection, multiple cellular mechanisms involved in inflammatory responses, coordinated neuroendocrine and localized responses to infection, and kinetics of viral replication. Emerging results from our studies reveal that the overall mechanisms mediating the protective effects of cannabinoids involve novel epigenomic regulatory mechanisms in need of systematic investigation. Here, we review the evidence supporting an immunomodulatory role for cannabinoids and its impact on disease progression with focus on HIV/SIV infection.