Fig. 3.

Sequential change in the OD₄₀₅ value in the SARS-CoV rNP-based IgG ELISA and neutralizing antibody titers in 19 subjects with sero-conversion. The terminal positions of the tail and the cap of arrows indicate the level of OD₄₀₅ value in the SARS-CoV rNP-based IgG ELISA at a dilution of 1:100 and neutralizing antibody titers of two serum samples collected from the same subject on different occasions. Black, red and blue arrows indicate the subjects with negative neutralizing antibody and negative antibody detectable by the SARS-CoV rNP-based IgG ELISA at the stage of the first blood collection, those with negative neutralizing antibody but positive antibody detectable by the ELISA at the same stage, and the subjects with positive neutralizing antibody but negative antibody detectable by the ELISA at the same stage, respectively. Green arrows indicate the subjects with both positive neutralizing antibody and positive antibody detectable by the ELISA at the same stage.