Figure 5.

ELISA binding titers of guinea pig serum antibodies to monomeric Δ123 (A), monomeric RBD (B), and peptides corresponding to epitopes I (C), II (D), and III (E) of the H77c strain. Half-log serial dilutions of sera were performed, and curves were fitted by nonlinear regression. Titers were obtained by interpolation using a value of 25-fold above background (defined by signal in the absence of sera) for the Δ123 and RBD antigens and 20-fold above background (defined as above) for peptides I, II, and III. The dashed line shows the lower detection limit of the assay (1:100 dilution).