EFFECTS OF CANNABINOIDS ON HOST-RESISTANCE TO LISTERIA-MONOCYTOGENES AND HERPES-SIMPLEX VIRUS

Cannabinoids possess immunosuppressive properties. These agents may decrease host resistance to infections with L. monocytogenes and herpes simplex virus type 2. Host resistance was measured by changes in the 50% lethal dose of the pathogen in cannabinoid-treated and control mice. The effect of cannabinoids on resistance to L. monocytogenes was dose dependent. .delta.-9-tetrahydrocannabinol at doses of 38, 75 and 150 mg/kg suppressed resistance to infection by 10-, 17- and 657-fold, respectively. Marijuana extract was less active but significantly reduced resistance to L. moncytogenes at all tested doses. Resistance to systemic herpes simplex virus type 2 infection was decreased 96-fold by .delta.-9-tetrahydrocannabinol, although marijuana extract was inactive. The doses and regimen of treatment with cannabinoids that produced significant decreases in host resistance were similar to those which caused suppression of delayed type hypersensitivity to sheep erythrocytes. The possible mechanisms and public health aspects of the decreased host resistance produced by marijuana extract and its cannabinoids are discussed.