THE CHEMISTRY OF THE NATIVE CONSTITUENTS OF THE ACETONE-SOLUBLE FAT OF MYCOBACTERIUM TUBERCULOSIS (BREVANNES)

Glycerol mycolates from synthetic mycolic acids

R- and S-Glycerol mycolates derived from single synthetic α-, keto- and methoxy-mycolic acids are described.

Final Report on the Safety Assessment of Glyceryl Stearate and Glyceryl Stearate/SE

Glyceryl Stearate and Glyceryl Stearate/SE are the esterification products of glycerine and stearic acid, and are used in cosmetic formulations as emollients, emulsifiers, and stabilizers. In acute oral toxicity studies in rats, both ingredients were slightly toxic. Glyceryl Stearate in the diet of rats for three consecutive generations had no adverse effects. Five percent Glyceryl Stearate did not promote the carcinogenicity of DMBA in mouse skin. In subchronic and chronic dermal toxicity tests, Glyceryl Stearate was nontoxic to rabbits but did cause moderate irritation. Primary eye irritation studies, at concentrations up to 100%, were mildly irritating or nonirritating to rabbits. Single and Repeated Insult Patch Tests showed both ingredients to be nonsensitizing and nonirritating. Products containing 2% Glyceryl Stearate were nonphototoxic and nonphotoallergenic. On the basis of the available data, it is concluded that Glyceryl Stearate and Glyceryl Stearate/SE are safe for topical application to humans in the present practices of use and concentration.

Mycolic acids constitute a scaffold for mycobacterial lipid antigens stimulating CD1-restricted T cells

CD1-restricted lipid-specific T lymphocytes are primed during infection with Mycobacterium tuberculosis, the causative agent of tuberculosis. Here we describe the antigenicity of glycerol monomycolate (GroMM), which stimulates CD1b-restricted CD4(+) T cell clones. Chemical characterization of this antigen showed that it exists as two stereoisomers, one synthetic isomer being more stimulatory than the other. The hydroxyl groups of glycerol and the mycolic acid length are critical for triggering the T cell responses. GroMM was presented by M. tuberculosis-infected dendritic cells, demonstrating that the antigen is available for presentation during natural infection. Ex vivo experiments showed that GroMM stimulated T cells from vaccinated or latently infected healthy donors but not cells from patients with active tuberculosis, suggesting that GroMM-specific T cells are primed during infection and their detection correlates with lack of clinical active disease.

CD1b-mediated T cell recognition of a glycolipid antigen generated from mycobacterial lipid and host carbohydrate during infection

T cells recognize microbial glycolipids presented by CD1 proteins, but there is no information regarding the generation of natural glycolipid antigens within infected tissues. Therefore, we determined the molecular basis of CD1b-restricted T cell recognition of mycobacterial glycosylated mycolates, including those produced during tissue infection in vivo. Transfection of the T cell receptor (TCR) alpha and beta chains from a glucose monomycolate (GMM)-specific T cell line reconstituted GMM recognition in TCR-deficient T lymphoblastoma cells. This TCR-mediated response was highly specific for natural mycobacterial glucose-6-O-(2R, 3R) monomycolate, including the precise structure of the glucose moiety, the stereochemistry of the mycolate lipid, and the linkage between the carbohydrate and the lipid. Mycobacterial production of antigenic GMM absolutely required a nonmycobacterial source of glucose that could be supplied by adding glucose to media at concentrations found in mammalian tissues or by infecting tissue in vivo. These results indicate that mycobacteria synthesized antigenic GMM by coupling mycobacterial mycolates to host-derived glucose. Specific T cell recognition of an epitope formed by interaction of host and pathogen biosynthetic pathways provides a mechanism for immune response to those pathogenic mycobacteria that have productively infected tissues, as distinguished from ubiquitous, but innocuous, environmental mycobacteria.

Infra-red spectroscopy and its application to microbiology

Colorimeters and non-recording spectrophotometers for visible and ultra-violet light have been used for many years and are to be found in most microbiological laboratories. With the need for greater speed of operation, recording instruments are now coming into more general use. During the last two decades recording infra-red spectrophotometers have been developed and these have enabled the absorption measurements on micro-organisms to be extended into the infra-red region of the spectrum. Two factors have tended to retard the use of infra-red spectrophotometry. One is the high initial cost of the equipment and the other is the large absorption of infra-red radiation by water. Despite these difficulties, a considerable amount of work has now been done and it seems profitable to review the varied applications to which infra-red spectroscopy has already been put and to indicate the results which have been obtained by its use.

Purification of 1-monoacylglycerols containing alpha-branched-beta-hydroxylated fatty acids from lipids of Corynebacterium pseudotuberculosis

A complex mixture of monoacylglycerols, identified as (C30--C36) corynomycoloylglycerols was isolated from the diethyl ether/acetone-soluble lipids of Corynebacterium pseudotuberculosis.