Characterization of Japanese encephalitis virus envelope protein expressed by recombinant baculoviruses

Recombinant baculoviruses containing the coding sequences of the viral structural proteins, i.e., the capsid (C) protein, the precursor to premembrane (preM) protein, and the envelope (E) protein, as well as a nonstructural protein, NS1, of Japanese encephalitis virus (JEV) were constructed. Infection of Spodoptera frugiperda cells with these recombinant viruses produced PreM and E proteins. The E proteins synthesized by the recombinants were shown to be glycosylated and similar in size to the authentic E protein. The E protein was found on the surface of infected cells. The antigenic properties of recombinant E proteins were evaluated using a panel of monoclonal antibodies produced against JEV E protein. It was demonstrated that all of the epitopes detectable on the authentic JEV E protein were present on the recombinant E protein expressed by a recombinant baculovirus containing the coding sequence for a part of C, PreM, E, and a part of NS1 proteins. However, for E protein expressed by a recombinant baculovirus having the coding sequence of only a part of PreM, but all of E and a part of NS1, one of the flavivirus cross-reactive epitopes was not detected. Mice immunized with cells infected with the recombinant baculoviruses developed neutralization antibodies.