Studies on the lipid of BCG. I. Glyceryl mono-mycolate in wax C fraction of the lipid of BCG.

Abstract

In the analyses of the lipid of Mycobacterium tuberculosis, Stodola, Lesuk and Anderson (1938) isolated a long chain hydroxyacid having a molecular formula of C88H176O4 and showing acidfastness. The mycolic acid has been subjected to extensive studies by Lederer and his coworkers. In fact, various kinds of related fatty acids were isolated and purified by chromatography from lipids of human strains of tubercle bacilli, Test and Aeschbacher (Asselineau and Lederer, 1949; 1951), H37Ra and H37Rv (Asselineau, Demarteau and Lederer, 1950) and of bovine strains, Vallée (Demarteau, 1951), BCG (Ginsberg and Lederer, 1952), Marmorek (Demarteau and Lederer, 1952) and Mycobacterium phlei (Peck and Anderson, 1941; Barbier and Lederer, 1952) . In view of the fact that those acids isolated from various kinds of Mycobacteria have closely related chemical configulations, i.e. a long alkyl branch on α position and a hydroxy radical on β position, they were generally designated as mycolic acids.So long as fatty acids in bacterial lipids are concerned, the presence of mycolic acids in Mycobacteria is certainly a distinguishable character from other bacteria. It has also been reported that the lipid of tubercle bacilli contained mycolic acids not only in the form of free acid but also of complexes with another components possessing biological activities.Sabin, Doan and Forkner (1930) reported that the phosphatide and wax fractions were responsible for the formation of tubercle which was composed of epitheloid and giant cells, although other bacterial components, protein and polysaccharide, showed no bearing thereupon. The tubercle formation in the lesion of tuberculosis was, therefore, chiefly due to the lipid of tubercle bacilli. Later, mycolic acid (Gerstl, Tennant and Perzman, 1945), wax D (Delaunay, Asselineau and Lederer, 1951) and branched fatty acids (Sabin 1941; Husseini and Elberg, 1952) were proved to have the activity when injected into animals.As wax D is a lipopolysaccharide containing a lot of mycolic acids, it seems reasonable that mycolic acid is one of the important components for tubercle formation.Since Anderson's pioneering studies, the free mycolic acid has been shown to have acid-fast property, which is one of the characteristic features of Mycobacteria. Furthermore, it should be emphasized that no other substance responsible for acid-fastness has ever been isolated from Mycobacteria than mycolic acid and related complexes. Accordingly, acid-fastness of tubercle bacilli should partly depend on the chemical nature of mycolic acids.Choucroun (1947) reported the isolation of a lipopolysaccharide from tubercle bacilli by extraction with paraffin oil, which was capable of producing tubercle lesion in guinea pig's lung when injected intraperitoneally. As the toxic lipid gave mycolic acid and sugars on hydrolysis, it was an ester of mycolic acid with a polysaccharide and in all likelihood identical with wax D, a chloroform soluble and hot acetone insoluble wax derived from tubercle bacilli.Bloch (1950) reported the presence of another toxic lipid, called cord factor, in the lipid of tubercle bacilli which inhibited strictly leucocyte migration and exerted delayed toxicity in injected mice which succumbed showing pulmonary hemorrhage and decrease in body weight. Extensive studies on the occurrence and chemical nature of the toxic lipid rendered evident that the toxic lipid could be found in the petroleum ether extract as well as the chloroform soluble wax, especially wax C. (Bloch, Sorkin and Erlenmeyer, 1953; Noll and Bloch 1953; Asselineau, Bloch and Lederer, 1953) .