Studies on allergoids from naturally occurring allergens IV. Efficacy and safety of long-term allergoid treatment of ragweed hay fever

An allergoid of ragweed was produced by treating dialyzed defatted pollen extract under mild conditions with formaldehyde. This modified antigen was found to have the desirable properties of reduced allergenicity, retained antigenicity, and prolonged stability for IgG antibody production. A series of trials was carried out in ragweed-allergic patients from 1972 to 1978. In 1972 it was demonstrated that on average, allergoid had on the basis of antigen E content about one fiftieth the ability of unaltered whole ragweed extract (allergen) to induce local delayed and systemic allergic reactions when given subcutaneously. IgG antibody responses specific for allergen were readily induced. A blinded comparison in 1973 divided 48 highly sensitive patients into two groups on the basis of basophil sensitivity; one group was treated with allergoid and the other with allergen. In individuals never before treated, allergoid stimulated a significantly more rapid rise in IgG antibodies. Clinical evaluation in 45 of the patients gave a modest advantage (not significant) to allergoid. An open trial employing booster injections every 2 wk except during the ragweed season continued until 1978 in many of these patients and showed no evidence of long-term ill effects of allergoid. IgG antibody titers were maintained at a high level, and IgE antibodies, after a rise in the first year, declined slowly in both groups. Daily symptom-medication scores continued to be lower in the allergoid-treated group each year, and the difference was significant (p < 0.05) in 1975, 1976, and 1977. In comparison with allergen, allergoid has the advantages of prolonged shelf life, lowered potential to induce allergic reactions, and more rapid induction of IgG antibody responses.