Immunity of Hamsters to West Nile and Murray Valley Viruses Following Immunization with St. Louis and Japanese B.

Abstract

An available strain of Syrian hamsters was found to be highly susceptible to West Nile (WN) and Murray Valley encephalitis (MVE) viruses by peripheral routes of inoculation. Groups of animals of this species were then immunized with Japanese B encephalitis (JBE) and St. Louis encephalitis (SLE) viruses and subsequently challenged subcutaneously with serial dilutions of WN and MVE viruses. Complete protection against these 2 agents was afforded by JBE immunization, and protection of a lesser degree obtained by SLE immunization. Neutralizing antibody titers of the immunized hamsters to the 2 heterologous challenge viruses paralleled their peripheral resistance in that the JBE virus immunes had higher neutralizing antibody titers to WN and MVE viruses than did the SLE virus immunes. These findings together with previously reported data support the hypothesis that cross immunity to these viruses probably occurs in man and that there might be some practical application of this concept in the field of human immunization. Further work with animals using other virus combinations is in progress.