Protective effect of OK‐432 (streptococcal preparation) on murine fulminant hepatitis following mouse hepatitis virus infection

SHIRAI, MUTSUNORI; WATANABE, SEISHIRO; NISHIOKA, MIKIO

The effects of OK‐432 (streptococcal preparation) on murine fulminant hepatitis were investigated. Hepatitis was induced by injection of mouse hepatitis virus type 2 (MHV‐2) at a strength of either 1 times 10(3) or 1 times 10(4) plaque‐forming units (PFU). Mice without OK‐432 treatment died within 5 days, whereas mice pre‐inoculated with OK‐432 showed survival rates of 50% (1 times 10(3)PFU) or 10% (1 times 10(4)PFU) after 60 days. Survival time was not prolonged if OK‐432 was injected after MHV‐2. Examined histologically, mice not treated with OK‐432 showed severe haemorrhagic necrosis of the liver, often panlobular. Treated mice showed less necrosis; the least necrosis was observed in those injected with OK‐432 before MHV‐2. In those mice injected first with OK‐432 and then with 1 times 10(3)PFU of MHV‐2 that survived 7 days, autopsy showed a very slight and focal hepatic necrosis, with follicular infiltration by lymphocytes and macrophages. Mitogenic reaction of spleen cells was remarkably less than normal in mice with MHV‐2 injection. However, mice injected with OK‐432 before MHV‐2 (same treatment as mice showing high survival rates) showed relatively high reactivity in comparison with mice not treated with OK‐432.