GLYCOSYLATION OF SYNTHETIC T-HELPER CELL EPITOPIC PEPTIDES INFLUENCESTHEIR ANTIGENIC POTENCY AND CONFORMATION IN A SUGAR LOCATION-SPECIFICMANNER

The immunodominant T helper cell epitopes 31D and VF13N of rabies viru s nucleoprotein and glycoprotein, respectively, correspond to peptide sequences AVYTRIMMNGGRLKR and VVEDEGCTNLSGF and are expressed between amino acids 404-418 and 29-41, of the appropriate proteins. We investi gated how internal or external glycosylation affects the biological ac tivity and conformation of the peptides 31D and VF13N. Mid-chain incor poration of maltobiose or N-acetylglucosamine moieties into the aspara gine residues greatly diminished the T-cell stimulatory activity in vi tro (due to the diminished ability of the glycopeptides to bind to maj or histocompatibility complex determinants) and reduced the characteri stic alpha-helicity of the peptides in aqueous trifluoroethanol soluti ons. In contrast, addition of maltobiose- or N-acetylglucosamine-coupl ed asparagines to the N-termini of peptides 31D and VF13N resulted in unchanged T-cell activity. Furthermore, N-terminal glycosylation of pe ptide 31D, as indicated by the functional assay, decreased the sensiti vity of the peptide to degradation in human serum and did not affect t he alpha-helical conformation. These data indicate that glycosylation of T-cell epitopes is not a preferable method for the preparation of a ntagonists, but incorporation of the sugars to appropriate positions m ay be advantageous in the design of T-cell agonists and peptide-based vaccines.