Mapping of an allergenically important determinant of grass group I allergens

This report documents the mapping of the second major epitope, previously described as site D, of grass group I allergens to residues 23-35 of meadow fescue group I (STFYGKPTGAGPK). Mapping was accomplished by screening fractions from a meadow fescue group I tryptic digest for peptide(s) that inhibit the ability of monoclonal antibody 24.64 (specific for site D) to bind to immobilized group I allergen. One such peptide, representing residues 23-35 of meadow fescue group I, was identified. Additional studies with the use of synthetic analogs of this peptide demonstrate that it binds mAb 24.64 directly. Examination of extracts containing group I glycoproteins from seven other species of grass confirms antigenic cross-reactivity due to this peptide. We also report based on protein sequence analysis that the amino terminal segment (which includes the site D epitope) of GpI allergens from seven different grass species is highly conserved and contains two hydroxyproline residues and an N-linked carbohydrate moiety.