Vaccination with complete adjuvant-added inactivated virus vaccine of Japanese encephalitis to swine, rabbits and chicks for preventing viremia (epidemiological study on Japanese encephalitis 25)

As a step towards the elimination of Japanese encephalitis virus in natural surroundings, we inoculated pigs, rabbits and chicks with inactivated Japanese encephalitis vaccine supplemented with complete or incomplete Freund's adjuvant twice at one-week interval. Subsequently, we compared HI antibody titers of the groups inoculated with vaccine containing complete Freund's adjuvant (pigs, rabbits, chicks), of the group inoculated with vaccine containing incomplete adjuvant (rabbits), ar;d of the groups inoculated with vaccine containing no adjuvant (pigs, rabbits, chicks), and also observations on changes in the antibody titers due to natural infection. In a certain portion of these animals neutralizing antibody titers were also determined. The results of this study are briefly summarized as follows. 1. In the groups of pigs and rabbits inoculated with vaccine containing complete Freund's adjuvant, titers of HI antibody and neutralizing antibody were higher than those inoculated with vaccine containing no adjuvant and their high titers persisted. Further, in the group of chicks inoculated with inactivated Japanese encephalitis vaccine containing complete Freund's adjuvant, HI antibody titers were higher and persistent as compared with the antibody titers in the chicks inoculated with inactivated Japanese encephalitis vaccine alone. 2. In the rabbits inoculated with inactivated Japanese encephalitis vaccine contammg incomplete adjuvant, HI antibody titers were lower than in those receiving the vaccine with complete adjuvant, but it has been demonstrated clearly that vaccination of inactivated Japanese encephalitis vaccine supplemented with incomplete adjuvant brings about less sideeffects. Hence such a method of vaccination can be applied as the vaccination with least side-effects. 3. With respect to natural infection of swine, on August 27 when the pigs were thought to have been infected, there was observed a rise in antibody titers. And on being infected with Japanese encephalitis, the antibodies formed in those pigs inoculated with inactivated Japanese ence- phalitis vaccine with or without complete adjuvant proved to be all 2-ME resistant type, whereas the antibodies produced in the control groups not receiving such a vaccination were 2-ME sensitive antibody.