MOLECULAR-BASIS OF IGE-RECOGNITION OF LOL-P-5, A MAJOR ALLERGEN OF RYE-GRASS POLLEN

Grass pollen, especially of lye-grass (Lolium perenne), represents an important cause of type I allergy. Identification of IgE-binding (alle rgenic) epitopes of major grass pollen allergens is essential for unde rstanding the molecular basis of interaction between allergens and hum an IgE antibodies and therefore facilitates the devising of safer and more effective diagnostic and immunotherapy reagents. The aim of this study was to identify the allergenic epitopes of Lol p 5, a major alle rgen of rye-grass pollen, immunodissect these epitopes further so that the amino acid residues critical for antibody binding can be determin ed and investigate the conservation and nature of these epitopes withi n the context of the natural grass pollen allergens. Peptides, 12-13 a mino acid residues long and overlapping each other by 3 amino acid res idues, based on the entire deduced amino acid sequence of the coding r egion of Lol p 5, were synthesised and assayed for IgE-binding. Two st rong IgE-binding epitopes (Lol p 5 (49-60) and (265-276), referred to as peptides 7 and 34, respectively) were identified. These epitopes we re further resolved by truncated peptides and amino acid replacement s tudies and the amino acid residues critical for IgE-binding determined (Lol p 5 (49-60) residue Lys,, and (265-276) residue Lys,,,). Sequenc es of these epitopes were conserved in related allergens and may form the conserved allergenic domains responsible for the cross-reactivity observed between pollen allergens of taxonomically related grasses. Fu rthermore, due to its strong IgE-reactivity, synthetic peptide Lol p 5 (265-276) was used to affinity-purify specific IgE antibodies which r ecognised proteins of other clinically important grass pollens, furthe r indicating presence of allergenic cross-reactivity at the level of a llergenic epitope. Moreover, Lol p 5 (265-276) demonstrated a strong c apacity to inhibit IgE-binding to natural rye-grass pollen proteins hi ghlighting the antibody accessibility to these sequences within the co ntext of the natural allergens. Strong IgE-binding epitopes of Lol p 5 have been identified down to single critical amino acid residues and are shown to occur as linear or continuous domains in the natural conf ormation of natural Lol p 5 and other group 5 grass pollen allergens. The fact that such an allergenic synthetic epitope has the capacity to strongly inhibit IgE-binding to natural allergens highlight its poten tial for use as a candidate in future therapeutics to treat pollen-ass ociated allergies. (C) 1998 Elsevier Science Ltd. All rights reserved.