To further confirm the antigenic activities of the identified R1-R5 regions, five newly designed short peptides encompassing regions R1-R5 (Fig. 6, panel A) were expressed as C-terminal fusions to thioredoxin (Trx) and purified from E. coli [29, 30] . The binding affinities of these peptides to the mouse, goat and human antisera were characterized by the method of ELISA, with thioredoxin as the control (Fig. 6, panels B and D) . As can been seen from the figure, the ELISA results generally correspond well to the screening results shown in Figs. 4 and 5 . Specifically, the peptide P1 (corresponding to the R1 region identified in all three screenings, Figs. 4 and 5 ) was reactive to all three antisera. The peptides P3, P4 and P5, corresponding to the R3-R5 regions identified only in the screening against the goat antisera (Fig. 4 , panels C, D, and Fig. 5) were only reactive to the goat antisera (Fig. 6, panel C) . There is one exception in that the peptide P2 (corresponding to the R2 region identified in the screenings using the mouse and human antisera, Figs. 4 and 5) showed no measurable affinity to either mouse or human antisera, suggesting that the R2 region might be less conformation-independent than the other four regions.