Mechanisms of peptide immunotherapy in allergic airways disease.

Allergen immunotherapy with whole proteins is clinically efficacious but requires a protracted treatment period because of frequent allergic adverse events. A combination of duration of treatment and adverse events leads to poor compliance. Short synthetic peptides containing the major immunodominant T cell epitopes of allergenic proteins have been shown to reduce IgE cross-linking ability, thereby leading to fewer allergic adverse events following their administration to patients with allergies. Peptide immunotherapy has been shown to result in clinically meaningful efficacy in several Phase II, randomized, double-blind, placebo-controlled clinical trials. Exactly how peptide immunotherapy achieves its efficacy remains incompletely understood, but the mechanisms are thought to include immune deviation and induction of regulatory T cells capable of suppressing allergen-specific immune responses. Limited data are available on the effects of peptide therapy on humoral immune responses. Induction of allergen-specific IgG has been observed after peptide therapy, but the levels of antibody induced were much lower than generally seen with the utilization of whole allergen approaches. Thus, the immunological mechanisms of peptide immunotherapy appear to overlap, although not completely, with those seen in whole allergen therapy. Further studies are required to fully elucidate mechanisms of action.