CUTANEOUS DELAYED-HYPERSENSITIVITY REACTIONS OF CATTLE VACCINATED WITH MUTANT STRAINS OF BRUCELLA-ABORTUS, USING BRUCELLINS PREPARED FROM VARIOUS BRUCELLAR STRAINS

Cutaneous reactivity to brucellin was evaluated in 10-month-old heifer s vaccinated with low-virulence mutant strains of Brucella abortus and was compared with brucellin reactions in postparturient cows with act ive brucellosis. In the cows, the cutaneous lesion was characterized m icroscopically as severe, acute, serofibrinous vasculitis; dermal lesi ons at 6, 12 25, and 48 hours after brucellin injection consisted of e ndothelial activation and perivascular exudation that led to progressi ve accumulation of fibrin, monocytes, macrophages, and lymphocytes. In vaccinated heifers, cutaneous tests were done, using standard brucell in, brucellin prepared from strain RB51, and the purified brucellar pr oteins-31K and superoxide dismutase. Negative-control cattle given sal ine solution, did not have cutaneous reactions. Standard brucellin ind uced the most marked reactions in vaccinated heifers. Brucellin from r ough strain RB51 caused positive reactions in heifers vaccinated with strain 19, but reactions were variable in other groups. Skin lesions i nduced by purified superoxide dismutase and 31-kd proteins in vaccinat ed cattle were not acceptable for diagnosis. Marked variability of tes t responses in vaccinated cattle precludes field use of this test to d etermine vaccination status.