Characterization of allergens prepared from smooth and rough strains of Brucella melitensis.

Protein allergens were prepared from smooth strain Rev. 1 and rough strain B115 using a cold saline method of extraction. Guineapig skin tests showed the two preparations to be of similar potency and specificity. Gel filtration on Sephadex G-75 showed that the skin test reactive fractions of each preparation were composed of a mixture of proteins with molecular weights in the range of 12,000 to 50,000. Polyacrylamide gel electrophoresis and immunoelectrophoresis indicated that the preparations consisted of at least 12 similar, if not identical, protein constituents. At least 20 protein bands were revealed with polyacrylamide gel isoelectric focusing, which appeared to be almost identical in the two preparations. Smooth lipopolysaccharide antigen, tested in normal and infected guineapigs, was of a lower potency than protein allergens and the eyrthematous response occurred earlier, resembling an antibody mediated reaction rather than delayed hypersensitivity. The allergen prepared from the rough strain contained no detectable smooth lipopolysaccharide antigen and therefore did not stimulate a secondary rise in antibody to smooth cells in sensitized animals. As the presence of smooth lipopolysaccharide antigen in an allergen appears to be unnecessary for provoking delayed hypersensitivity responses, and undesirable because it may stimulate the production of antibodies which interfere with diagnosis, it is preferable to prepare allergens from rough strains of brucella.