Resistance to Tuberculosis in Mice immunized with BCG disrupted in Oil

Abstract

RECENTLY it was shown¹ that mice develop resistance to pulmonary infection with virulent Mycobacterium tuberculosis (strain H37Rv) when attenuated tubercle bacilli (BCG or H37Ra) are administered either intravenously or by the aerosol method. Previously, several authors^2,3 demonstrated that killed organisms suspended in mineral oil produce significant changes in experimental hosts and Choucron⁴ extracted a fraction (Pmko) with mineral oil to which various immunological activities were ascribed. Cell walls and cell wall extracts of a variety of micro-organisms have been found to produce resistance to infection in experimental animals although cytoplasmic particles rather than cell wall material have been implicated as the protective antigen of M. tuberculosis^5,6. Since we had been unable to immunize mice either with cell walls of attenuated tubercle bacilli which had been ruptured in water or with the entire disruption product (mixture of cell wall and cytoplasm), investigations were initiated to test the potency of BCG bacilli disrupted in oil. This method was utilized by D. W. Smith and the material was reported to be highly immunogenic in guinea pigs (Conference on Immunity and Pathogenesis of Mycobacterial Diseases, U.S. National Institutes of Health, March 1962). The experiment described here shows that such products are capable of giving rise to significant protective immunity in mice injected intravenously with as little as 0.2 mg of material.