Microencapsulation - The future of oral immunotherapy?

Subcutaneous immunotherapy has been used successfully to treat atopic diseases for many years. However, its use is associated with several problems, the most bothersome being systemic allergic reactions. This has led to evaluation of alternative methods of treatment, including oral immunotherapy. For the most part, oral administration of allergens has not proven an effective substitute because of the lack of potency. Extraordinarily large oral doses were required to achieve clinical improvement, but even these doses were ineffective with some allergens. To resolve this difficulty, we have developed a novel system of encapsulating allergens which protects them from the destructive effects of gastric acid and pepsin. Most importantly, encapsulated allergens administered orally to mice elicited vigorous systemic immune responses, with stimulation of predominantly CD4+ T helper type 2 lymphocytes. Three studies of encapsulated short ragweed pollen extracts (eSRW) in short ragweed (SRW)-sensitive humans have been done. Treated patients developed high titres of SRW IgG antibodies, had blunting of the expected anamnestic increase in SRW IEE antibodies, downregulated the expected seasonal increase in nasal SRW IgA antibodies and had a decrease in nasal sensitivity to SRW on provocative testing. Symptoms were significantly decreased in treated patients if they could tolerate a high dose of eSRW. This was accomplished without inducing any systemic reactions, with an oral dose only slightly higher than that used in high dose subcutaneous immunotherapy. These encouraging results suggest that encapsulated allergens have the potential to become important therapeutic agents in immunotherapy.