Expression analysis of a Babesia bovis BboP67 gene homologous to the Theileria parva p67 gene

Abstract

A fragment of a novel gene, designated as the BboP67 gene, of Babesia bovis, which had been recently reported as a homolog of the gene encoding a sporozoite-specific P67 antigen of Theileria parva, was isolated from the genomic DNA of B. bovis and expressed as a recombinant (rBboP67) in E. coli. The antigenicity of rBboP67 was evaluated using 102 and 68 field serum samples collected from cattle in Ghana and Mongolia, respectively. All of the B. bovis- and B. bigemina-infected sera, which had been identified by the species-specific antigens, rRAP-1/CTs, for B. bovis and B. bigemina in the standard ELISA, positively reacted with the rBboP67 in ELISA. While B. bovis-infected field serum samples recognized the rBboP67 in Western blot analysis, sera collected from the experimentally infected cattle with B. bovis merozoites failed to react to it. IFAT analysis conducted with polyclonal antisera collected from the immunized mice with rBboP67 did not show any positive reaction to the B. bovis merozoites. These results indicate that the p67 homolog is not expressed in merozoite stage but is likely expressed in sporozoites; they also suggest that the antigen might be relatively conserved among different isolates of B. bovis and, at least, several epitopes of the antigens might be shared between B. bovis and B. bigemina sporozoites.