THE COWDRIA-RUMINANTUIM GROE OPERON

A Cowdria ruminantium genomic DNA library was constructed in the expre ssion vector lambda ZAPII, and an immunoreactive clone, designated lam bda Cr9.4, was isolated by screening with serum from a C. ruminantium- infected goat. Sequencing of the insert from this clone revealed two o pen reading frames, encoding peptides of 10462 and 58697 kDa respectiv ely, Database searching indicated that the two genes were homologues o f groES and groEL, genes encoding a group of heat shock proteins invol ved in protein processing, export and assembly, Western blotting exper iments showed that the recombinant GroEL protein was recognized by ser a raised against four isolates of C. ruminantium which originate from South Africa, West Africa and the Caribbean, but not by antisera to th e closely related Ehrlichia species (E. ovina, E, [Cytoecetes] ondiri, E. bovis, E. phagocytophila) of African and European ruminants which can be expected to occur in similar geographical areas to C, ruminanti um. This suggests that this protein may be useful in development of se rodiagnostic tests for C, ruminantium infection which are not subject to cross-reactions with antibodies to Ehrlichia species, The cloning a nd expression of the GroE operon will also facilitate further study of the roles of the GroE proteins in the immune response to C, ruminanti um.