Physicochemical and immunologic characterization of low molecular-weight allergoids of Dactylis glomerata pollen proteins

Background: Orchard grass (Dactylis glomerata) pollen proteins were chemica lly modified by means of acid anhydrides (maleic and succinic anhydride) to obtain low-molecular-weight allergoids. Chemical modification in both case s led to the replacement of one positive charge (epsilon amino group of Lys ) by one negative charge, yielding proteins with changed physicochemical pr operties in comparison to the native orchard grass-pollen proteins. Methods: Physicochemical characterization of derivatives was done by gel ch romatography, SDS-PAGE, and isoelectric focusing. To examine the IgE-bindin g properties of these derivatives, we carried out immunoblotting. To examin e the ability of derivatives to induce IgG production, we immunized rabbits . Skin prick testing with the allergoids was performed on 15 individuals al lergic to orchard grass pollens and on two healthy subjects. Results: II was shown that the modified proteins retain their original mole cular weights, but change pi to more acidic values. In the case of allergoi ds, a strong reduction in IgE binding was found. Immunization of rabbits wi th allergoids showed that the derivatives retain the ability to induce IgG production, and that the antisera obtained in such a way react to native (u nmodified) extract. The ability of derivatives to induce allergic reaction was significantly reduced. The patients (86.6%) included in our study exhib ited less than 50% of native extract response. Among them, 53.3% had no res ponse to one or both allergoids. Conclusions: These modification procedures yield allergoids with a reduced allergenic activity and preserved immunogenic potential suitable for use in immunotherapy.