Cannabinoid Administration Attenuates the Progression of Simian Immunodeficiency Virus

Delta(9)-Tetrahydrocannabinol (Delta(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, chronic Delta(9)-THC use may impact HIV disease progression. We examined the impact of chronic Delta(9)-THC administration (0.32 mg/kg im, 2 x daily), starting 28 days prior to inoculation with simian immunodeficiency virus (SIVmac251; 100 TCID50/ml, iv), on immune and metabolic indicators of disease during the initial 6 month asymptomatic phase of infection in rhesus macaques. SIVmac251 inoculation resulted in measurable viral load, decreased lymphocyte CD4(+)/CD8(+) ratio, and increased CD8(+) proliferation. Delta(9)-THC treatment of SIV-infected animals produced minor to no effects in these parameters. However, chronic Delta(9)-THC administration decreased early mortality from SIV infection (p = 0.039), and this was associated with attenuation of plasma and CSF viral load and retention of body mass (p = NS). In vitro, Delta(9)-THC (10 mu m) decreased SIV (10 TCID50) viral replication in MT4-R5 cells. These results indicate that chronic Delta(9)-THC does not increase viral load or aggravate morbidity and may actually ameliorate SIV disease progression. We speculate that reduced levels of SIV, retention of body mass, and attenuation of inflammation are likely mechanisms for Delta(9)-THC-mediated modulation of disease progression that warrant further study.