Factors affecting the immunizing activity of ribosomal fractions isolated from Mycobacterium tuberculosis var. bovis strain BCG.

Levels of antituberculous immunity similar to those induced by live BCG vaccine were detected in CF1 mice immunized with ribosomal fractions isolated from Mycobacterium tuberculosis var. bovis, strain BCG, and challenged 3 weeks later with the virulent H37Rv strain of Mycobacterium tuberculosis var. hominis. The activity of the crude ribosomal preparations was found to be a function of the immunizing doses and the immunity induced by 1.0-mg doses remained at the same high level after 4 weeks of storage at 4 degrees C but decreased markedly thereafter. Dialysis and lyophilization had no detrimental effects on the activity of the crude preparations whereas purification by column chromatography on Sephadex G-200 annihilated their biological activity. Crude low-polysaccharide-containing preparations were found inactive even at the 1.0-mg dose level and results of experiments performed with crude ribosomal fractions of varying polysaccharide contents strongly suggest that polysaccharides, or RNA-polysaccharide complexes, may play an important role in the induction of immunity with crude ribosomal fractions isolated from the BCG strain of Mycobacterium tuberculosis var. bovis.