Indian Journal of Virology

To determine cross-protection amongst three antigenically related flaviviruses i.e., JEV, DEN and WN viruses that are prevalent simultaneously in some of the South East countries including India. Monoclonal antibodies (MAbs) raised against glycoprotein E (gpE) of Japanese encephalitis virus (JEV) strain 733913 were administered in mice 1 day before or 2 days after intracerebral challenge with West Nile virus (WNV) strain 68856 or Dengue virus (DENV-2) strain P23085. Furthermore, two JEV strains belonging to group II (strains 641686 and 691004) that have lost reactivity against virus-specific MAbs were also used in passive immunization experiments. MAbs as ascitic fluids were administered intraperitoneally in mice. Hemagglutination-inhibition- (HAI) positive JEV-specific (Hs-3) MAbs given 2 days after the virus infection showed reduced mortality along with increased survival of mice challenged with WNV or with DENV-2. Also the HAI-positive flavivirus cross-reactive MAbs produced a marginal increase in the survival of mice challenged with both JEV strains 641686 and 691004 belonging to the group II. As the MAbs reacting with HAI –positive virus - specific (Hs) and HAI –negative virus - specific (NHs) epitopes are neutralizing and protective in mice against JEV strain 733913 challenge, the results indicate a cross-protection phenomenon in mice that might be occurring in some of the localities endemic for the three closely related flaviviruses.