Spider monkeys inoculated with 17D yellow fever vaccine and 6 months later with an attenuated isolate of West Nile virus were protected against central nervous system (CNS) lesions when challenged by St. Louis or Japanese B encephalitis viruses under special experimental conditions.
Reversing the order of inoculations was less effective.
Spider monkeys inoculated first with 17D yellow fever virus and then with West Nile virus produced a higher level of neutralizing antibody to St. Louis encephalitis virus than monkeys given West Nile virus first.
The length of time that elapsed between the inoculation of 17D yellow fever and West Nile viruses was important in determining the height of the level of neutralizing antibody to St. Louis encephalitis virus.
An attenuated isolate of Langat virus protected spider monkeys against challenge by all the other seven members of the Russian spring-summer virus complex, protection being judged by the absence of CNS lesions.
Passive immunization of spider monkeys with antisera which contained antibody against Russian spring-summer encephalitis (RSSE) virus and was produced by inoculation of spider monkeys with an attenuated strain of Langat virus protected monkeys against CNS lesions when challenged with RSSE virus under certain experimental conditions.
Spider monkeys inoculated sequentially with 17D, dengue type 4, West Nile, and Langat viruses had a lower viremia when challenged subcutaneously with other types of dengue viruses, than monkeys immunized with other vaccination procedures, and had the highest levels of neutralizing antibodies against heterologous dengue serotype viruses.
The criteria for a vaccination procedure based on the principle of serologic overlap were discussed.
The role of group B arbovirus antibodies was discussed in relation to infections in man with these agents.
The senior author wishes to dedicate this paper to Dr. Max Theiler and Dr. Joseph Smadel whose encouragement and discussions during the last 8 years have played a prominent role in the work described in this paper. However, any errors of interpretation and all views expressed are those of the authors. The senior author also wishes to thank Drs. Jordi Casals and Delphine Clarke for fruitful discussions concerning the antigenic relationships between arboviruses and Dr. Philip Sartwell for encouragement during the past few years.