By Aliasger K. Salem
In the U.S., 84% of residences have detectable levels of house dust mite (HDM) allergens, and a quarter of these houses have higher levels of allergens than the proposed limit for asthma. High levels of these allergens can trigger asthma attacks in sensitized individuals. Long-term exposure to allergens triggers a T-helper 2 (Th2) immune response that is thought to be correlated with these asthma attacks. Vaccines could be used to prevent allergen-induced asthma attacks by lowering the level of Th2 orchestrated airway inflammation and stimulating protective immunity by Th1 cells that reduce the symptoms linked with allergy.
Amongst the various allergen-producing HDM, Dermatophagoides pteronyssinus (Der p), is the most common allergy-causing mite. Serum samples of 79% of patients suffering from asthma, wheezing, and/or rhinitis showed positive titers for anti-Der p2 IgE antibodies. Existing strategies for treatment of the symptoms of dust mite allergies include the use of β2 agonists and neutralizing antibodies such as Xolair (omalizumab). Approaches for prevention or reduction of dust mite allergies include desensitization by long-term sublingual immunotherapy. Desensitization is an approach that has shown a lot of promise in the clinic for inducing HDM-speciﬁc long-term tolerance in adults and children, but such treatment requires regular administration of high doses of HDM allergens for at least three years to show satisfactory clinical efﬁcacy.
In a previous AAPS Blog and AAPS Journal article, I discussed how biodegradable nanoparticles could be used to stimulate potent antigen-specific Th1-biased immune responses if we packaged the adjuvant and antigen into a biodegradable nanoparticle-based delivery system. In another article that was recently published in The AAPS Journal, we show that biodegradable nanoparticles that deliver Der p2 antigen and CpG adjuvants trigger a Th1-biased Der p2-specific antibody response that has the potential to protect against asthma attacks after subsequent and repeated nasal exposure to allergens. This study highlights the potential that vaccines have for protecting against allergen-induced asthma attacks, and the continuing potential that biodegradable nanoparticles have in enhancing and stimulating protective antigen-specific immune responses. This paper is part of a special theme issue I am developing for The AAPS Journal on the use of biodegradable nanoparticles in vaccine delivery.