The Relationship between Sedimentation Value and Immunogenic Activity of Mycobacterial Ribonucleic Acid

Abstract In a series of papers Youmans and Youmans (1–8) have reported that ribosomal or ribonucleic acid (myc. RNA)2 preparations obtained from living cells of the attenuated H37Ra strain of Mycobacterium tuberculosis were as immunogenic in CF-1 mice as viable cells of the H37Ra strain. This comparison was based upon the amount of RNA present in each vaccine. The immunity engendered by these preparations is specific and long lasting. The RNA preparations also have certain nonspecific activities of particular interest. For example, this material can act as a potent adjuvant for the production of antibody to bovine γ globulin (BGG) in mice, being as active in this respect as complexes of poly-adenylic and poly-uridylic acids (poly A:U) (9). In addition, the myc. RNA can serve as an effective adjuvant for the induction of experimental allergic encephalomyelitis in guinea pigs (10). Insofar as immunogenic activity against tuberculous infection is concerned, apparently the myc. RNA must exist in a double-stranded form to be highly active (5). In addition, the presence of a component having a sedimentation value of 16-S appeared to be required for good immunizing activity (5). Sedimentation analysis using 5 to 20% sucrose gradients either did not show a 23-S component or showed only a small shoulder or hump on the 16-S peak where the 23-S peak would be expected to appear. However, more recently we have found that when the myc. RNA is treated with trace amounts of pancreatic ribonuclease, which hydrolyzes single stranded but not double stranded RNA, an entirely different sedimentation pattern is obtained; the 16-S peak disappears and a distinct 23-S peak emerges.