Structure elucidation of sphingolipids from the mycopathogen Paracoccidioides brasiliensis: An immunodominant beta-galactofuranose residue is carried by a novel glycosylinositol phosphorylceramide antigen

Two major acidic glycolipid components (Pb-1 and Pb-2) have been extracted from the mycopathogen Paracoccidioides brasiliensis, a thermally dimorphic fungus endemic to rural areas of South and Central America. Sera of all patients exhibiting paracoccidioidomycosis were found to be reactive with Pb-1, but not with Pb-2; no reactivity was observed with sera of healthy patients or those with histoplasmosis [Toledo, M. S., Suzuki, S., Straus, A. H., and Takahashi, H. K. (1995) J. Mcd. Vet. Mycol. 33, 247-251]. We report here the complete structure elucidation of both P. brasiliensis glycolipids using monosaccharide, fatty acid, sphingosine, and inositol component analysis by GC-MS; H-1- and P-31 NMR spectroscopy; ESI-MS and -MS/CID-MS, linkage analysis, and exoglycosidase digestion. the compounds were found to be glycosylinositol phosphorylceramides (GIPCs) with the following structures: Pb-2, Manp alpha 1-->3Manp alpha 1-->2Ins1-P-1Cer; and Pb-1, Manp alpha 1-->3[Galf beta l-->6]Manp alpha 1-->2lns1-P-1Cer. the serologically nonreactive Pb-2 appears to be a biosynthetic intermediate between mannosylinositol phosphorylceramide (MIPC), which is widely distributed among fungi, and the antigenic Pb-1. Pb-1 is a novel glycosphingolipid, similar to a triglycosyl IPC (Hc-VI) reported from Histoplasma capsulatum [Barr, K., Laine, R.A, and Lester, R. L. (1984) Biochemistry 23, 5589-5596], but differing in the anomeric configuration of the terminal Galf1-->6 residue, which is immunodominant. the significance of these structures as serological and taxonomic markers, as well as their potential utility as targets for immunodiagnostic agents, is discussed.Univ Georgia, Complex Carbohydrate Res Ctr, Athens, GA 30602 USAUniversidade Federal de São Paulo, Escola Paulista Med, Dept Biochem, BR-04023900 São Paulo, BrazilUniversidade Federal de São Paulo, Escola Paulista Med, Dept Biochem, BR-04023900 São Paulo, BrazilWeb of Scienc