Protective effects of immunoactive peptide, FK565 against systemic and local infections with herpes simplex virus and murine cytomegalovirus and respiratory tract infection with influenza virus in mice.

The protective effects of FK565 against systemic infections with herpes simplex virus (HSV) and murine cytomegalovirus (MCMV), respiratory tract infection with influenza virus and zosteriform rash with HSV investigated in mice. FK565 showed excellent protective activities against systemic infections with both acyclovir (ACV)-sensitive and-resistant HSV at intravenous and subcutaneous doses of 0.1 and 1 mg/kg and oral dose of 1 mg/kg. FK565 showed superior protective activities at subcutaneous doses of 0.01 and 0.1 mg/kg compared to ACV at subcutaneous dose of 15 mg/kg against MCMV infection. In respiratory tract infection with influenza virus, FK565 showed potent protective effects at intravenous, subcutaneous and oral doses of 0.001 to 1 mg/kg. FK565 markedly inhibited zosteriform spread of HSV on the flank skin at an intravenous dose of 0.1 mg/kg and the mice given FK565 survived longer than the control mice. The peritoneal exudate cells from FK565-treated mice suppressed the growth of HSV in mouse embryo fibroblast more strongly than those from the control mice, although FK565 had no direct antiviral activity against HSV. These findings suggest that FK565 enhanced the host defense ability against viral infections by nonspecific activiation of macrophages.