Adjuvants for allergen immunotherapy: experimental results and clinical perspectives

Inclusion of adjuvants in immunotherapy vaccines are important to enhance immune responses to allergens. This article will cover the recent advances in adjuvant formulations described in published articles primarily over the past 2 years.

Traditionally, allergen immunotherapy preparations utilize aluminium hydroxide as an adjuvant. These have generally proved efficacious and have a good safety profile. However, recent advances in the understanding of immunological mechanisms underlying immunotherapy and in the design of new adjuvants may allow a more rational approach to adjuvant use. One approach is to use adjuvants such as immunostimulatory sequences or monophosphoryl lipid A, which can deviate allergy-associated Th2 immune responses towards a Th1 phenotype. Both of these adjuvants have been used in pilot controlled clinical trials which have demonstrated clinical efficacy and the induction of protective IgG antibodies. Other approaches to improve immunotherapy vaccines include microencapsulation of allergen to allow delivery of the allergen directly to the gut in order to induce immunological tolerance and vaccination with heat-killed mycobacteria.

There is great interest in newly designed adjuvants to improve the efficacy and safety of allergen immunotherapy. A better understanding of immunological mechanisms and further clinical trials utilizing new adjuvants are needed.