Acta Virologica Vol.52, No.4, p.219-224, 2008

In the present study, the effect of monoclonal antibodies (MAbs) against glycoprotein E (gE) of Japanese encephalitis virus (JEV) strain 733913 administered 1 day before or 2 days after intracerebral (i.c.) challenge with West Nile virus (WNV) strain 68856 or Dengue virus (DENV-2) strain P23085, was studied in mice. 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 (i.p.) 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 (Hx) 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 JEV-specific (Hs) and HAI-negative JEV-specific (NHs) epitopes were neutralizing and protective in mice against JEV strain 733913 challenge, the results indicated presence of the cross-protection phenomenon that might be occurring in some of the localities endemic for the three closely related flaviviruses.