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.