Analysis of immunodominant piroplasm surface antigen alleles in mixed populations of Theileria sergenti and T. buffeli.

Previous studies revealed that isolates of Theileria sergenti consisted of at least 2 parasite populations bearing 2 different allelic forms of p33/32, an immunodominant piroplasm surface protein, and that the majority of T. sergenti-infected calves harbored mixed parasite populations of Ikeda (I)- and Chitose (C)-types. In this study we designed an additional oligonucleotide primer, which specifically amplified the p34 gene of T. buffeli (BI-type). DNAs from 3 field isolates in Japan were positive with this primer as well as those prepared from cattle imported from Australia and the T. buffeli Warwick stock, but restriction enzyme patterns of the PCR products from the former 3 were different from those of the latter. The nucleotide sequence of the gene amplified from Japanese isolates showed 89% homology at the nucleotide level and 88% homology at the amino-acid level with T. buffeli p34 genes. The results indicate that T. sergentilbuffeli distributed in Japan and Australia is a mixture of parasites with various combinations of 4 different allelic types.