Structural and immunological properties of the phenolic glycolids from Mycobacterium gastri and Mycobacterium kansasii

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Abstract
Mycobacterial species‐specific antigens belong to the three following classes: phenolic glycolipids (Phe Gl), acyltrehalose‐containing lipooligosaccharides and polar glycopeptidolipids. These antigens have been chemically defined and alkali‐labile epitopes were found to characterize the lipooligosaccharide antigen type.In the present study the major Mycobacterium kansasii phenolic glycolipid epitope namely Phe Gl K‐I was delineated as the distal monoacetylated disaccharidic residue: 2,6‐dideoxy‐4‐O‐methyl‐α‐D‐Arbino‐hexopyranosyl‐(1 → 3)‐2‐O‐methyl‐4‐Oacetyl‐α‐L‐fucopyranose. This acetoxy group is required for K‐I epitope recognition demonstrating that alkali‐labile epitopes also occur in the phenolic glycolipid antigen class. Using immunoelectron microscopy, the Phe Gl K‐I epitope was localized around the electron‐transparent layer on the M. Kansasii cell‐wall surface. Furthermore, two new phenolic glycolipids namely Phe Gl K‐III and Phe Gl K‐IV were discovered in minute amounts. They were purified and characterized by their retention time in direct‐phase column HPLC. These molecules are also M. kansasii antigens, whose epitopes differ from that of Phe Gl K‐I. The complete family of phenolic glycolipids Phe Gl K‐I, K‐II, K‐III and K‐IV was found in both rough and smooth variants of both M. kansasii and Mycobacterium gastri species.

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