In vivo anti-influenza virus activity of kampo (Japanese herbal) medicine "sho-seiryu-to" and its mode of action.

When BALB/c mice were treated with a Kampo (Japanese herbal) medicine "Sho-seiryu-to" (SST) (2 g/kg, 10 times) orally from 7 days before to 4 days after the infection and infected with mouse-adapted influenza virus A/PR/8/34 by nasal site-restricted infection, replication of the virus in the nasal cavity and spread of the virus to the lung were efficiently inhibited at 5 days after infection in comparison with water-treated mice. However, another Kampo medicine "Kakkon-to" showed no anti-influenza virus activity in the same condition. The antiviral IgA antibody in the nasal and broncho-alveolar washes of the SST treated mice increased significantly in comparison with that of water-treated control. Oral administration of SST (2 g/kg, 18 times) from 7 days before to 13 days after vaccination also significantly augmented serum hemagglutination-inhibiting antibody by nasal inoculation of influenza HA vaccine (5 micrograms/mouse) that was insufficient to induce antiviral antibody. SST did not inhibit the replication of mouse-adapted influenza virus A/PR/8/34 in Madin-Darby canine kidney cells. SST also did not inhibit the influenza virus sialidase activity against sodium p-nitrophenyl-N-acetyl-alpha-D-neuraminate and hemagglutination by mouse-adapted influenza virus A/PR/8/34. SST showed no influence on interferon production in nasal wash of mice at 5 days after the virus infection. These results suggest that SST confers better protection against influenza virus infection through augmentation of production of antiviral IgA antibody but not direct action to the virus, and can be used as an adjuvant to nasally inoculated influenza HA vaccine.