CLONING AND SEQUENCE-ANALYSIS OF A NEWLY IDENTIFIED BRUCELLA-ABORTUS GENE AND SEROLOGICAL EVALUATION OF THE 17-KILODALTON ANTIGEN THAT IT ENCODES

A thus far unknown gene encoding a Brucella abortus protein has been i solated from a lambda gt11 expression library probed with sera from Br ucella-infected sheep, Sequence analysis of the cloned gene revealed t he presence of an open reading frame of 158 amino acids encoding a pro tein of 17.3 kDa (calculated molecular mass). The recombinant B. abort us protein, expressed in Escherichia coli, and the corresponding Bruce lla melitensis protein migrated at the same apparent molecular masses as shown by Western blotting (immunoblotting). Among a series of serum samples from B. melitensis- or B. abortus-infected sheep and cows, 51 and 39%, respectively, showed a signal at 17 kDa on Western blot anal ysis of total protein extract from Brucella bacteria, These figures am ount to 70 and 61% for sheep and cattle, respectively, in a competitiv e enzyme-linked immunosorbent assay with a specific monoclonal antibod y, These data indicate that the 17-kDa antigen may be useful for serol ogical diagnosis of Brucella infection.