Figure 2

a. Serial dilution of antigens from 1:50 to 1:3200. All antibodies are at dilution 1:100. Selected Ag concentration for NP (1:400 dilution), N3 and N7 (1:100 dilution) antigen for cross-reactivity study are 80 μg/ml, 60 μg/ml and 50 μg/ml, respectively. b. Linear regression of ELISA titre and positive/negative ratio (P/N) ratio of 1:100 serum dilution. The regression equation y = 1.004x + 4.0233 (r = 0.936) is shown, where y is the ELISA titre of an individual serum sample, and x is the P/N value at 1:100 serum dilution.