Cloning and partial characterization of the Cr32 gene of Cowdria ruminantium

Cowdria organisms were purified by density gradient centrifugation. The DNA was used to construct expression libraries. The immunodominant Cr32 protein was purified and its N-terminal amino acid sequence was determined. The expression libraries were screened with Cr32-specific monoclonal antibodies, but did not yield Cr32-positive clones. Therefore a part of the Cr32-gene was amplified using primers derived from the N-terminal and an internal amino acid sequence. This DNA was used as a probe to detect the genomic DNA fragment encoding the Cr32 protein. This fragment was cloned, using genomic DNA of the Senegal strain of Cowdria ruminantium. A part of the gene comprising two third of its total length has been expressed in vector pGEX2T. This expression product is recognized by Cr32-specific monoclonal antibodies.