Purification of a 28 kDa Babesia (Theileria) equi antigen and a 29 kDa spurious erythrocyte antigen from in vitro culture through ion exchange chromatography.

An extract of in vitro cultivated Babesia equi was fractionated using a MonoQ anion exchange column. Separation of a 28 kDa B. equi antigen from a 29 kDa spurious erythrocyte antigen, both of which were intensely immunoreactive, was achieved by chromatography of the infected erythrocyte proteins. Using tricine-SDS-PAGE, the 28 kDa antigen of B. equi showed multiple band resolution, while the 29 kDa antigen was consistently resolved as a single band. The 29 kDa antigen was identified in both infected and non-infected erythrocyte extracts. Moreover, B. equi antiserum recognised this antigen in the non-infected erythrocyte extract, and conversely serum from horses not infected with babesia detected the antigen in infected erythrocyte extract. This 29 kDa antigen could represent a horse erythrocyte isoantigen. The purified 28 kDa antigen is specifically recognised by B. equi antisera and therefore could be useful for the production of the recombinant replica and to employ these in further test systems.