Structures of the glycopeptidolipid antigens of Mycobacterium abscessus and Mycobacterium chelonae and possible chemical basis of the serological cross-reactions in the Mycobacterium fortuitum complex

Abstract

Mycobacterium abscessus and Mycobacterium chelonae, two members of the Mycobacterium fortuitum complex, contain five major glycolipids. A combination of NMR spectroscopy, fast atom bombardment mass spectrometry and chemical degradation was used to elucidate their structures. All the compounds belong to the family of glycopeptidolipids. A 6-deoxy-a-~-talosyl unit, which may bear one or two acetyl groups, invariably occupies the site of glycosylation on the threonine residue in the various compounds. A 3,4-di-O-methyl-or 2,3,4-tri-O-methyl-a-~-rhamnosyl unit modifies the alaninol end of the diglycosylated molecules. Both species also contain a multiglycosylated compound consisting of a-L-rhamnosyl-(I -+ 2)-3,4-di-O-methyl-a-~-rhamnosyl linked to alaninol, which belongs to the class of new variants of glycopeptidolipids recently described. Using an ELISA, the latter glycolipid as well as the diglycosylated ones (not previously reported to be antigenic), were shown to react with the serum raised against the whole lipid antigens of M. chelonae. A comparative serologic study of the native and chemically modified glycopeptidolipid antigens allowed the identification of their epitope as the 3,4-di-O-methyl-a-~-rhamnosyl residue. Similar experiments conducted on the glycopeptidolipids isolated from the serologically cross-reacting species M. peregrinum led to the conclusion that the epitope identified in M. chelonae and M. abscessus was involved in the cross-reactions and demonstrated the existence of a second haptenic moiety in the glycolipids of M. peregrinum, the 3-O-methyl-a-~-rhamnosyl unit. In addition to this latter non-shared epitope, the recently described sulfated glycopeptidolipid antigen of M. peregrinum did not react with the M. chelonae serum, thus further explaining the difference in the seroreactivity within the complex.

Identification and Characterization of the Genes Involved in Glycosylation Pathways of Mycobacterial Glycopeptidolipid Biosynthesis

“…6). However, it is reported that M. fortuitum complex produced GPLs which are glycosylated as in GPL-5 and GPL-6 as major components (19,20). Therefore, these observations suggest that this type of glycosylation is not specific for M. smegmatis.…”

Hypervirulence of a Rough Variant of the Mycobacterium abscessus Type Strain

“…The precise nature of these GPLlike compounds was resolved by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry. All of the GPL-associated pseudomolecular ions ([M ϩ Na] ϩ ) detected in the smooth strains perfectly matched the GPLs previously described for M. abscessus in calculated molecular weight (16). In contrast, these GPL-associated pseudomolecular ions were nondetectable in the rough strains (data not shown).…”

Spontaneous reversion of Mycobacterium abscessus from a smooth to a rough morphotype is associated with reduced expression of glycopeptidolipid and reacquisition of an invasive phenotype

“…3b, square bracket). The colour and mobility of the extra lipids are similar to those of apolar GPLs of M. avium (McNeil et al, 1989), and it has been reported that M. abscessus expresses GPLs (Lopez-Marin et al, 1994). To provide further evidence that these lipids are M. abscessus GPLs, the plates were sprayed with 1-naphthol to detect deoxyhexoses found in GPLs, and extracts were also subjected to mild alkaline methanolysis to which GPLs are resistant (McNeil et al, 1989;Torrelles et al, 2002).…”

“…GPLs are found in the outermost portion of the mycobacterial cell envelope of NTM (Barrow et al, 1980;Furuchi & Tokunaga, 1972;Goren et al, 1972;Ortalo-Magne et al, 1996) and contain antigenic determinants for a number of mycobacterial species (Brennan & Goren, 1979;Camphausen et al, 1985;Lopez-Marin et al, 1994). The GPL molecule typically consists of a tripeptide-amino alcohol core with an amide linked long chain fatty acid.…”