Allergen immunotherapy: therapeutic vaccines for allergic diseases

Allergen immunotherapy is the administration of gradually increasing quantities of an allergen vaccine to an allergic subject, reaching a dose which is effective in ameliorating the symptoms associated with subsequent exposure to the causative allergen. Controlled studies have shown that allergen immunotherapy is an effective treatment for patients with allergic rhinitis/conjunctivitis, allergic asthma, and allergic reactions from stinging insects. The treatment of allergic diseases is based on allergen avoidance, pharmacotherapy, allergen immunotherapy, and education of the patient. Immunotherapy, where appropriate, should be used in combination with all forms of therapy with the goal that the allergic patient will become as symptom-free as medically possible. Allergen immunotherapy is indicated for patients who have demonstrated evidence of specific IgE antibodies to clinically relevant allergens. The rationale for prescribing allergen immunotherapy depends on the degree to which symptoms can be reduced by medication, the amount and type of medication required to control symptoms, and whether effective allergen avoidance is possible. The response to immunotherapy is specific for the antigen administered. Mixtures of allergens unrelated to the patient's sensitivity should not be utilized. Physicians should know of local and regional aerobiology and the exposure of the patient in the home and work environments. Only physicians with training in allergology (allergy/immunology) should prescribe the clinically relevant vaccine for allergen immunotherapy. The quality of the allergen vaccine is critical for both diagnosis and treatment. Where possible, standardized vaccines of known potency and shelf life should be utilized for allergen immunotherapy. The use of well-characterized and standardized vaccines makes it possible to define an optimal maintenance dose in the range of 5-20 mu g of major allergen per injection for a number of primary allergens. Therapeutic efficacy correlates with such doses. The major risk of allergen immunotherapy is anaphylaxis. Therefore, allergen immunotherapy should be administered by or under the close supervision of a trained physician who can recognize early symptoms and signs of anaphylaxis and administer appropriate emergency treatment. The optimal duration of immunotherapy is still unknown. Many clinicians advise 3-5 years of therapy for patients who have had a good therapeutic response. However, the decision to discontinue allergen immunotherapy should be individualized. Several studies suggest that venom immunotherapy may be discontinued after 3-5 years in most patients. However, the decision to discontinue venom immunotherapy should be individualized.