FIG. 6.

Time course of NS1 antibody levels/titers in mice infected with JEV. Sera were examined by the one-dilution (A) or endpoint (B) method of the CDC assay and ELISA for measuring IgG (C) or IgM (D) antibodies. The sera used in this experiment were collected in a previous study (15), in which five mice in one group were immunized with 100 μg (closed circles) or 10 μg (closed squares) of pcJEME or were inoculated with PBS (open triangles), followed by infection with JEV. Because of the small volumes of stored sera, sera pooled from the five mice were used for this experiment. Sera were not available from PBS-inoculated mice on day 14, since the mice died of JEV infection. The volume of stored sera from mice immunized with 10 μg of pcJEME on days 6 and 14 was not enough for examination by all assay methods. For ELISA, the antigen amount used for sensitization was 3 or 20 ng/well to measure IgG or IgM antibodies, respectively, and test sera were used at a 1:200 dilution. Dotted lines indicate cutoff values to differentiate positive from negative samples. Antibody levels/titers of 5% (the one-dilution method), 1:10 (the endpoint method), 0.076 (IgG ELISA), and 0.217 (IgM ELISA) or higher were determined to be positive (see the text for details).