Allergen immunotherapy: immunomodulatory treatment for allergic diseases

Allergen immunotherapy is currently the only immune-modifying treatment for allergic disease. At the present time it is indicated for the treatment of allergic rhinitis, asthma and venom hypersensitivity. Efficacy appears to be dose dependent, and the immunological mechanisms responsible for the clinical efficacy of immunotherapy are still being elucidated. Immunological changes associated with immunotherapy include induction of T regulatory cells, increase in allergen-specific immunoglobulin G4, increase in interleukin-10 production and downregulation of the T helper 2 response. The disadvantages of allergen immunotherapy include risk of adverse events and patient time and inconvenience. Risks of immunotherapy range from large local reactions to mild systemic reactions, such as rhinitis. Fatalities from immunotherapy injections have been reported at a rate of approximately one fatality per 2.5 million injections. Conventional subcutaneous immunotherapy build-up schedules involve administration of a single-dose increase each visit and it may take several months before a patient achieves the therapeutic maintenance dose. Accelerated schedules, such as rush and cluster, will allow the patient to achieve the maintenance dose sooner but there may be a greater risk of a systemic reaction. The current focus of immunotherapy research is to develop safer and more effective vaccines. Another approach to enhancing immunotherapy safety is through an alternative delivery method. Sublingual immunotherapy is clearly safer than subcutaneous immunotherapy, but further investigation is needed to determine optimal dose and appropriate patient selection.