Mite allergy is associated with a specific profile of IgG epitopes recognized on antigen p1 of Dermatophagoides pteronyssinus

BACKGROUND: Immune response to inhaled antigens differs in allergic patients and healthy individuals, mostly in the quality of T cell help provided (i.e. Th2 or Th1 dominant subset). However, while different in many functional aspects, both groups of T cells shared the capacity to support the synthesis of antigen-specific immunoglobulin G (IgG) antibodies detected in different amounts in the serum of atopic and healthy individuals. OBJECTIVE: The present study investigates whether these IgG responses display similar or different epitopic dominance in the mite sensitization model. METHODS: Antibody specificity was evaluated by comparing the IgG binding to native Der p1 (nDer p1) and its products of pepsin hydrolysis (dDer p1) in 56 mite-allergic patients and 148 healthy individuals, including 24 mite-sensitized individuals in a solid enzyme linked immunosorbent assay (ELISA). Antibody specificity was also studied in competitive ELISA using streptavidin biotin technology. RESULTS: Mite-allergic sera showed a higher degree of binding to nDer p1 than to dDer p1, whereas control sera and mite-sensitized sera bound at a similar level to the two forms of the antigen. Allergic sera and control sera, including mite-sensitized sera, showed distinct capacities to prevent the binding to nDer p1 of pooled IgG from each group as well as murine monoclonal antibodies specific to Der p1. CONCLUSION: The IgG response to Der p1 of mite-allergic patients differs from that of healthy controls and mite-sensitized subjects, not only in its increased titres but also in its consistant pattern of modified specificity, displaying a marked preference for conformational epitopes. Cross-competition experiments confirm the clinically associated, restricted specificity, allowing almost complete discrimination between groups, particularly between mite-sensitized and mite-allergic subjects, which is currently impossible with routinely available assays.