Challenge of Monkeys with Japanese B Virus after Immunization by West Nile Infection Plus Japanese B Vaccine

Abstract

Treatment of monkeys with various doses of cortisone followed by subcutaneous inoculation of JBE virus led to viremia in each instance but not to clinical disease. Monkeys inoculated with a dose of 0.1 ml of a 10^-1 dilution of WN virus for immunization showed viremia within the first 3 days. Neutralizing antibodies to WN virus frequently developed by the 7th day after inoculation and reached their maximum titer in the 2nd and 3rd week. The injection of potent JBE vaccine in WN immune animals had a booster effect on WN neutralizing antibodies. There was a significant rise in JBE neutralizing antibodies in these stone animals after the JBE vaccine inoculation, and 2 out of 3 also developed CF antibodies. Monkeys thus immunized basically with WN virus infection and supplemented with one injection of potent JBE vaccine developed either a questionable degree of viremia or none when inoculated with JBE virus after cortisone treatment. On the other hand, monkeys immunized with one injection of potent JBE vaccine only, or with WN virus only, had a consistent and prolonged viremia. The combined WN and JBE vaccine immunization appeared to prevent infection entirely, since this group of animals showed no serological rises following virus challenge. It is concluded that this evidence, supplementing that obtained with hamsters, recommends this method of immunization for human trial, providing that a safe strain of WN virus for human use is found.