[Analysis of immune response to Japanese encephalitis virus infection in mice: effect of cyclosporin A on the production of HI antibody and interferon].

To study the protective factors against Japanese encephalitis (JE) virus infection, the effects of cyclosporin A (CsA) on the mortality, hemagglutination-inhibition (HI) antibody response and interferon (IFN) production induced by JE virus were investigated in mice. CsA was given to each mouse orally 50 mg/kg/day. CsA had a tendency to enhance HI antibody production from 14th day and significantly enhanced on 21st and 28th days after inoculation with inactivated JE virus vaccine. Similarly CsA also enhanced HI antibody production up to at least 50th day after live JE virus inoculation. CsA-treated mice showed a significantly lower mortality rate (7/52, 13.5%) than non-CsA-treated (control) mice (17/51, 33.3%) (p < 0.05). CsA did not affect the serum IFN levels, which reached their peak values at 12 hours and fell to almost basal levels by 24 hours after the inoculation of inactivated JE virus vaccine. These results suggest that an adequate antibody response is one of the major protective factors in JE virus-infected mice, even if it is limited in the early stage of the primary JE virus infection.