Nuclear immunofluorescence in porcine kidney cells infected with Japanese encephalitis virus

Acetone-fixed porcine stable kidney (PS) cells infected with Japanese encephalitis (JE) virus were stained in indirect fluorescent antibody (FA) assay with anti-JE virus monoclonal (MoAb) and polyclonal (immune PF) antibodies. First positive immunofluorescence (IF) occurred in the cytoplasm with MoAb Hs-1 (anti-envelope, JE-specific) and immune PF after 7 hr post-infection (p. i.); it became prominent by 15 hr to 48 hr (maximum) when cells reacted strongly also with MoAb Hx-3 (flavivirus crossreactive epitope). In addition, 15 to 20% of the infected cells, which revealed positive cytoplasmic IF, showed intranuclear IF with Hs-1, Hx-3, and immune PF by 20 to 24 hr p.i. By 48 hr, the intranuclear IF was not observed or became diminished. These observations indicate that the JE virus specific epitope Hs-1 appeared first followed by the flavivirus cross-reactive epitope Hx-3. Nuclei of the infected cells seem to play some role in the replication of JE virus.