Allergology International (Jan 2002)
Allergen immunotherapy: Current and new therapeutic strategies
Abstract
Allergen-specific immunotherapy (SIT) involves the administration of gradually increasing amounts of an allergen extract to reduce clinical symptoms of allergy. Well-controlled clinical trials have demonstrated the efficacy of SIT in the treatment of allergic diseases, including rhinoconjunctivitis and asthma, and best practice protocols have been established. Nevertheless, application of this potentially curative treatment is restricted, largely due to the risk of serious adverse events, especially in asthmatics. Although efficacy is high for venom-induced allergy, success rates for the more common aeroallergen-induced disease range from 60 to 80% depending on the allergen. The practice of SIT is currently being refined following major advances in our knowledge of basic immune mechanisms. In particular, new T cell-targeted strategies are being explored with the awareness of the pivotal role allergen-specific T cells play in initiating and regulating the immune response to allergens. Current SIT induces decreased IgE class switching and eosinophil activation by downregulating production of the T helper (Th) 2-type cytokines interleukin (IL)-4 and IL-5. Therefore, allergen preparations that have ablated IgE binding while retaining T cell reactivity should still be clinically effective but have substantially improved safety. These approaches include the use of small peptides based on dominant T cell epitopes of allergens and chemically modified or recombinant allergen molecules. Both approaches have already been tested, with promising results, in animal models; peptide immunotherapy has been shown effective in clinical trials. Defined hypoallergenic molecules or peptides offer ease of standardization in addition to efficacy and safety and will result in more widespread use of SIT in clinical practice. Elucidation of mechanisms for downregulating Th2-predominant responses to allergen by SIT will enable the development of laboratory assays for monitoring clinical efficacy.
Keywords
