Expression and validation of D-erythrulose 1-phosphate dehydrogenase from Brucella abortus: A diagnostic reagent for bovine brucellosis

Brucella abortus is a bacterium of brucellosis causing abortion in cattle. The diagnosis of bovine brucellosis mainly relies on serologic tests using smooth lipopolysaccharide (S-LPS) from B. abortus. However, the usefulness of this method is limited by false-positive reactions due to cross-reaction with other Gramnegative bacteria. In the present study, the eryC gene encoding B. abortus D-erythrulose 1-phosphate dehydrogenase, which is involved in the erythritol metabolism in virulent B. abortus strain but is absent from a B. abortus vaccine strain (S19), was cloned. Recombinant EryC was expressed and purified for the evaluation as a diagnostic reagent for bovine brucellosis. Other B. abortus proteins, Omp16, PP26, and CP39 were also purified and their seroreactivities were compared. Recombinant EryC, Omp16, PP26, and PP39 were all reactive to B. abortus-positive serum. The specificity of recombinant Omp16, PP26, CP39, and EryC, were shown to be approximately 98%, whereas that of B. abortus whole cell lysates was shown to be 95%. The sensitivity of Omp16, PP26, CP39, and EryC were 10%, 51%, 64%, and 43%, respectively, whereas that of B. abortus whole cell lysates was 53%. These results suggested that B. abortus EryC would be a potential reagent for diagnosis for bovine brucellosis as a single protein antigen.