BRUCELLA RIBOSOMAL-PROTEIN L7 L12 IS A MAJOR COMPONENT IN THE ANTIGENICITY OF BRUCELLIN INRA FOR DELAYED-TYPE HYPERSENSITIVITY IN BRUCELLA-SENSITIZED GUINEA-PIGS/

A delayed-type hypersensitivity (DTH) reaction in the course of brucel losis in humans and animals can be revealed by the brucellin INRA (Bru cellergen) skin test. Brucellergen is composed of more than 20 protein s of different molecular weights. a 12-kDa protein eliciting DTH in br ucella melitensis Rev1-sensitized guinea pigs was found to be a signif icant component for the allergenic properties of Brucellergen. Sequenc ing of the gene encoding this protein identified it as the L7/L12 ribo somal protein. The L7/L12 gene of B. melitensis was amplified by PCR a nd subcloned in the Escherichia coli pQE30 plasmid. The resulting reco mbinant protein did not produce a DTH reaction in sensitized animals. It was used to raise specific antibodies in a rabbit. Affinity chromat ography with these antibodies was used to isolate a single protein fro m Brucellergen and from B. melitensis cytosol preparations which produ ced a DTH reaction in guinea pigs sensitized with B. melitensis Rev1. N-terminal amino acid sequencing of the protein confirmed that it was the L7/L12 ribosomal protein. This is the first complete report on the involvement of a defined bacterial ribosomal protein in the DTH respo nse of animals infected with intracellularly multiplying bacteria.