FIG 3.
Antigenicity of BdRON2 against sera from B. divergens-infected cows and gerbils. The reactivity of BdRON2 against recombinant BbRON2peptide was determined by ELISA with preimmune sera (PI) and sera from cows (A) or gerbils (B) experimentally infected with B. divergens. Three bovine serum samples showed higher OD values than the others at a 1:100 dilution, but then the reactivity dropped to the basal level, with all serum samples showing the same reactivity to BbRON2peptide at the remaining dilutions. One of the five serum samples from gerbils experimentally infected with B. divergens showed much higher OD values than noninfected serum samples in a dilution-dependent manner at dilutions of 1:200 to 1:6,400 (serum sample G3), and another gerbil serum sample (serum sample G4) showed higher reactivity than the others at the 1:200 dilution. However, no reactivity of the three bovine or three gerbil serum samples against BbRON2peptide was observed at any dilution, suggesting that the B. bovis RON2 peptide used here either is not specific enough for native BdRON2 or is within a region of the native antigen that is not exposed to the host immune mechanisms to generate naturally acquired antibodies against this peptide. Error bars show the standard error of the mean ODs.