Recombinant allergen immunotherapy: clinical evidence of efficacy--a review.

Recombinant allergens for immunotherapy aim to overcome the problems of natural extracts as they can be produced in unlimited amounts with exact physiochemical and immunological properties. These can be modified to have more favourable characteristics including reduced IgE reactivity or enhanced immunogenicity. Different types of recombinant allergens have been evaluated in clinical phase II and III trials whilst others are currently under development. In this review, we identified double-blind, placebo-controlled randomised clinical trials assessing the efficacy and safety of various recombinant allergen preparations. The majority of studies have up to now focused on cat, grass, birch, ragweed and bee venom allergens. Some studies have shown some of these preparations to be effective and well tolerated. However, there are still outstanding issues regarding optimum doses, minimising side effects and long-term effects.