Cutaneous Hypersensitivity in Brucellosis

Abstract

Summary The use of the surface-active agents, Duponol WA and Lorol, for the preparation of skin test antigens from Brucella suis is described. These reagents were more effective than Tergitol 7, Tween 80, Triton A-20, phenol and water. The time of onset of cutaneous hypersensitivity in guinea pigs was related to the number of living organisms used for sensitization. The intensity of the allergic response reached a maximum after 8 weeks of infection and decreased to a relatively constant level from the tenth to eighteenth week of infection. Reactions of the purpura type were produced in guinea pigs by the crude extract from the fourth to tenth week of infection. Such reactions were not observed in response to the partially purified reagent. The crude extract exhibited specificity for Brucella infection in guinea pigs. Responses in animals infected with Mycobacterium tuberculosis and Coccidioides immitis were not of the same order of magnitude in size or intensity as were produced in experimental Brucella infections. The partial purification and crystallization of the antigen by precipitation at pH 4–5 and ammonium sulfate precipitation at 6–10% of saturation at pH 7.0 and 5 C was described. The antigen is water-soluble near pH 7.0, thermostable and inactivated by trypsin. Tests for the presence of desoxyribonucleic and ribonucleic acids were negative while the tests for protein were positive. Only traces of carbohydrate were detected in the purified antigen. Upon further purification skin test activity of the reagent sharply increased, while the concentration of carbohydrate and of substances responsible for strong ultraviolet absorption at 2700 Å decreased. The final product showed a low specific density at this wave length. Repeated intradermal injections of the allergen did not result in the development of either systemic (anaphylactic) or dermal sensitivity in normal guinea pigs. These intradermal injections of the purified antigen resulted in very minor stimulation of agglutinin formation in guinea pigs and in a small group of humans. Guinea pigs infected subcutaneously with as few as 9 cells of Br. suis responded to the cutaneous test with the purified antigen 1 week following infection. The antigen was about 225% more potent when used to skin-test rabbits infected for 4 weeks with Br. suis (homologous species) than for rabbits infected for 4 weeks with Br. abortus or Br. melitensis (heterologous species). An allergen capable of detecting skin sensitivity in guinea pigs infected with Br. suis could not be extracted from Br. abortus strain A19 under the conditions of the method used successfully on Br. suis. Upon storage at 5 C for 11 months a solution of the purified antigen lost 85% of its skin test potency. Response to dosage data on various preparations were susceptible to analysis of relative potency by virtue of the parallelism of the log dose-log response relationship. The skin-test antigen inhibits the linear migration of leukocytes of normal guinea pigs in direct proportion to its concentration.