Identification of an immunodominant Babesia gibsoni 47-kDa antigen.

摘要

Pooled sera from dogs naturally infected with Babesia gibsoni were used to immunoscreen the cDNA expression library of B. gibsoni merozoite. The cDNA inserts of positive clones were sequenced. 98 clones were obtained and analysed. Two clones showing high homology values with BgP50 (48%) and BgP32 (47%), previously identified as potential immunodiagnostic antigens, were molecularly characterized and named as BgP47. The full length of the nucleotide sequence of the cDNA was 1830 bp and contained a single open reading frame with 1332 bp predicted to encode a polypeptide consisting of 444 amino acid residues. The molecular mass of the mature protein was 47.4 kDa. The putative N-terminal signal peptide had a highly predicted signal peptide probability (0.999) and a maximum cleavage site probability (0.715) between amino acids in positions 19 and 20. In an experimentally infected dog, a high antibody response to the recombinant protein rBgP47 from 4 days post-infection was observed, and the high antibody level was maintained until 541 days post-infection even when the infection was in the chronic stage. Furthermore, enzyme linked immunosorbent assay showed that rBgP47 specifically reacted with B. gibsoni antibodies. It is concluded that BgP47 is an immunodominant antigen stimulating the immune system of host infected with B. gibsoni. This antigen might be useful as diagnostic and vaccine candidate.