Studies on “allergoids” prepared from naturally occurring allergens II. Evaluation of allergenicity and assay of antigenicity of formalinized mixed grass pollen extracts

A crude dialyzed mixed grass pollen extract was modified under mild conditions with formaldehyde in the presence or absence of low molecular weight additives which participate in the chemical reaction. By scratch and intradermal skin testing of grass-sensitive subjects, certain of the derivatives (allergoids) were found to be about 200 to 2,000 times less allergenically reactive than the native pollen extract (allergen). The allergoids largely retained their capacity to induce guinea pigs to produce antibody which strongly cross-reacted with the allergen, as measured by passive cutaneous anaphylaxis (PCA) in normal guinea pigs. Cross-antigenicity between the allergen and allergoids was also observed by immunodiffusion analysis with the use of antiallergen and antiallergoid sera. One of the formalinized derivatives also was studied by bronchial inhalation challenge experiments in 5 asthmatic subjects.