Host defence mechanisms against Japanese encephalitis virus infection in mice.

The role of antibody and cell-mediated immunity in the resistance to Japanese encephalitis virus (JEV) infection was studied in adult mice. Passively transferred antibodies obtained up to 2 weeks after primary infection protected the recipient mice against a challenge infection with JEV. Antibody obtained at 4 or 5 weeks failed to protect despite the presence of high titres of neutralizing antibody. Protection was abrogated by pretreatment of the early serum with 2-mercaptoethanol to remove IgM. Similarly, adoptive transfer of immune spleen cells obtained up to 2 weeks after immunization provided protection. The protective effect was abolished by pretreatment of the immune spleen cells with anti-Thy 1.2 antiserum and complement. These findings suggest a role of T lymphocytes and IgM antibody in recovery from JEV infection.