Protection Against St. Louis Encephalitis and West Nile Arboviruses by Previous Dengue Virus (Types 1-4) Infection 1 2

Summary Hamsters inoculated with Den-2 virus were shown to survive peripheral challenge with large amounts of WN virus. Dengue types 1, 3, and 4 gave less complete protection than Den-2. Cynomolgus monkeys with probable naturally acquired Den-2 neutralizing antibody were shown to be protected from a persistent viremia following SLE virus inoculation. Serological tests on both hamsters and monkeys were of the expected pattern but did not lead to an understanding of the specific mechanism involved in the cross protection. These results support epidemiological observations of the absence of severe epidemics of JBE, SLE, WN, and other Group B encephalitides in areas with endemic dengue.