Oral immunotherapy with short ragweed extract in a novel encapsulated preparation: a double-blind study.

BACKGROUND: In the past, oral immunotherapy with allergens has had limited clinical effectiveness, presumably because of gastrointestinal destruction of allergens. OBJECTIVE: We have developed a new technique for microencapsulating protein antigens that permits them, when given orally, to bypass the stomach and be delivered to the small intestine in a highly immunogenic form. This study's purpose was to confirm the immunologic potency of orally administered short ragweed pollen extracts (SRW) microencapsulated (mSRW) by this new technique and to study the effectiveness of mSRW in controlling the symptoms of ragweed-induced hay fever. METHODS: Twenty-one SRW-sensitive patients were treated with mSRW in a double-blind placebo-controlled study. Serum SRW IgG and IgE antibodies and nasal secretory IgA antibodies were determined. During the ragweed season, symptoms were quantified by symptom-medication scoring. RESULTS: The treated patients had high titers of serum SRW IgG antibodies (1.15 microg/ml at baseline, increasing to 21.21 microg/ml), experienced regulation of the seasonal increase in serum SRW IgE antibodies (+9% vs +59% in placebo-treated patients), and produced a small amount of nasal SRW IgA antibodies. Despite an insubstantial pollen count, the symptom-medication scores in the treated group were lower than those in the placebo group (4.28 vs 6.18, p = 0.059), but the differences were statistically significant only in the subgroup that tolerated high doses (>20 microg of Amb a 1 in 19 of 21 patients, p = 0.04). These effects were accomplished without inducing any systemic reactions with a dose of mSRW (mean, 23.8 microg of Amb a 1) only slightly higher than that used in high-dose subcutaneous immunotherapy. CONCLUSION: Oral mSRW seems a safe, easily administered, and immunologically potent treatment for ragweed-induced hay fever, but its ultimate utility requires further study.