Identification of the major T-cell antigens present in the Brucella melitensis B115 protein preparation, brucellergene OCB

Brucellergene is a commercial allergen prepared from Brucella melitensis strain B115 and containing at least 20 cytoplasmic proteins. These proteins were separated by SDS-PAGE. The unstained gel was divided into 18 fractions and proteins were eluted from the gel fractions. The capacity of the separated proteins to elicit delayed-type hypersensitivity (DTH) in infected guinea-pigs or to induce the production of interferon-γ (IFN-γ) by blood cells from infected cattle was evaluated. The biological activity of the corresponding protein fractions blotted on to nitrocellulose was measured in a lymphocyte blastogenesis assay. Among the 18 fractions tested, two - spanning the mol. wt ranges 17-22 (fraction 8) and 35-42-kDa (fraction 17) - showed the maximum biological activity in the three tests. These fractions contain two antigens, the Brucella bacterioferritin (BFR) and P39 proteins. Both proteins are good candidates for the detection of cellular immunity to Brucella.