DEVELOPMENTAL REGULATION OF AN EIMERIA-BOVIS MESSENGER-RNA ENCODING REFRACTILE BODY-ASSOCIATED PROTEINS

Eimeria bovis antigens defined by the monoclonal antibody (mAB) 2.4 ar e associated with the refractile bodies of sporozoites and are found i n the parasitophorous vacuole and host cell cytoplasm during schizogon y. Screening of an E. bovis oocyst cDNA library with mAB 2.4 resulted in the identification of a single unique cDNA sequence (Eb-25/50). Com parison of the predicted protein sequence of Eb-25/50 revealed a high degree of identity to an Eimeria Tenella refractile body protein and m AB 2.4 was found to cross-react with refractile bodies from Eimeria ac ervulina, demonstrating that these proteins are highly conserved among eimerian species. Measurements of Eb-25/50 mRNA showed that the multi ple proteins recognized by mAB 2.4 are encoded by a single mRNA specie s whose kinetics of expression during sporulation and schizogony close ly correlated with protein expression. Consistent with the multiple Eb -25/50 proteins arising from a single polypeptide, results from a Sout hern analysis of E. bovis genomic DNA indicated that Eb-25/50 mRNA is derived from a single copy gene. The presence of Eb-25/50 proteins in the host cytoplasm during schizogony, the high degree of conservation of these proteins, and the apparent complex post-translational modific ation raises interesting questions about the biochemistry of these pro teins during eimerian development.