The current state of recombinant allergens for immunotherapy

Subcutaneous immunotherapy is a well documented treatment of allergic rhinitis and asthma. The majority of the disadvantages of the treatment are related to the poor quality of the natural allergen extracts which can contain varying amounts of individual allergens including allergens to which the patient may not be sensitized. Recombinant allergens offer a possibility to use well defined molecules with consistent pharmaceutical quality defined in mass units. The proof of concept of the clinical efficacy of recombinant allergens is based on two studies published as full articles.

One study applied a mixture of five Phleum pratense major allergens in a maximum dose of 40mcg protein. The clinical efficacy showed a significant efficacy with 40% reduction in disease severity. The second study compared a commercial birch extract with both recombinant Bet v 1 and purified Bet v 1 in dosages of 15mcg allergen. The clinical effect was 60% additional efficacy. Systemic side effects occurred more frequently with grass allergens. A third study used hypoallergenic fragments and a trimer of Bet v 1. The study did not show efficacy and a rather high frequency of systemic side effects.

The advantages of using recombinant allergens for immunotherapy are obvious but more studies on a large scale are needed before the overall value in terms of efficacy and safety can be assessed. Clinical trials are also necessary for new combined vaccines based on recombinant allergens that in experimental studies have shown greatly enhanced immunogenicity and low allergen-specific reactivity.