Morphine reduces herpes simplex virus-1 pathogenesis in the murine flank

Here we investigate the effect of morphine on herpes simplex virus-1 (HSV-1) pathogenesis using a murine flank scarification model. Murine flank scarification with HSV-1 results in primary lesions at the site of inoculation within three days and lesions at secondary sites within four days. The lesions are scored based on lesion size. Applying 0.1 mM morphine to the skin one-day post inoculation tested the effect of morphine on the formation of the herpes lesion. On days three through five, mice treated with morphine developed lesions with scores half of that observed in untreated animals, however, skin viral titers on these days were equivalent. Further, 1.0 microM morphine did not effect the replication rate of HSV-1 in Vero cells. Taken together, these data suggest the morphine reduced HSV-1 pathogenesis by modifying the host response to HSV-1 infection and not by reducing viral replication rates.