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 p roblems, the most bothersome being systemic allergic reactions. This h as led to evaluation of alternative methods of treatment, including or al 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 im provement, but even these doses were ineffective with some allergens. To resolve this difficulty, we have developed a novel system of encaps ulating allergens which protects them from the destructive effects of gastric acid and pepsin. Most importantly, encapsulated allergens admi nistered orally to mice elicited vigorous systemic immune responses, w ith stimulation of predominantly CD4+ T helper type 2 lymphocytes. Thr ee studies of encapsulated short ragweed pollen extracts (eSRW) in sho rt ragweed (SRW)-sensitive humans have been done. Treated patients dev eloped 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 n asal sensitivity to SRW on provocative testing. Symptoms were signific antly decreased in treated patients if they could tolerate a high dose of eSRW. This was accomplished without inducing any systemic reaction s, with an oral dose only slightly higher than that used in high dose subcutaneous immunotherapy. These encouraging results suggest that enc apsulated allergens have the potential to become important therapeutic agents in immunotherapy.