Optimization of the concentration of coating antigens and dilutions of serum for ELISA. Several recombinant proteins, Ernsaa 112-227E1aa 1-7 (A), Ernsaa 109-160 (B), and Ernsaa 109-145 (C), at 1 and 2 μg/ml, were tested for reactivity with one positive serum (S#3) and one negative serum at 1/50 and 1/100 dilutions, respectively. Each bar represents the mean value of two determinations.