Inhibition of influenza virus replication by cocaine

Cocaine has been shown to have a number of diverse effects on the immune system. The current investigators have previously demonstrated an inhibitory effect of cocaine on murine hepatitis virus replication in peritoneal macrophages in vitro. The present study was undertaken to examine the effects of cocaine on influenza virus replication and to further characterize that effect in an animal model. Cocaine was capable of inducing a dose-dependent reduction in influenza PR-8 replication using MDCK cells in vitro. Concentrations of 100 microg/ml caused a 50% reduction of virus. To further characterize the effect in vivo, C57Bl/6 mice infected with influenza PR-8 by intranasal instillation were given daily ip injections of 10 mg/kg cocaine just prior to and for 4 days after exposure to influenza. Lungs from mice exposed to cocaine had viral titers that were reduced approximately 50% compared to controls as demonstrated by hemagglutination titers. Additional studies suggest that this reduction appears to be caused by an increase of cocaine-induced interferon.