Heat denaturation affects the ProDer p 1 IgE reactivity and downregulates the development of the specific allergic response

Background: Modified allergens with reduced IgE-binding activity represent an elegant approach to circumvent the risk of anaphylactic reactions in allergen-specific immunotherapy. Objective: The current work investigated the effect of heat denaturation on the allergenic properties of recombinant ProDer p 1, a precursor form of the major house dust mite allergen Der p 1. Methods: The IgE reactivity was estimated by direct and competition ELISA. The immunogenicity of heat-denatured ProDer p 1 was evaluated in naive and Der p 1-allergic mice. Results: Heat denaturation in reducing conditions drastically reduced the in vitro ProDer p 1 IgE reactivity toward human allergic sera. In naive mice, heat-denatured ProDer p 1 generated mixed T(H)1-T(H)2 responses characterized by the absence of specific IgE with concomitant rise in specific IgG2a titers and the presence of IL-5 and IFN-gamma in splenocyte cultures. In contrast, natural Der p 1 or native ProDer p 1 induced typical strict T(H)2-biased allergic responses with strong IgG1 and IgE titers, whereas spleen cells exhibited only high IL-5 secretion. Moreover, native or beat-denatured ProDer p 1 vaccinations prevented airway eosinophil infiltrations after challenge. Although native or heat-treated ProDer p 1 adjuvanted with SBAS1b induced mixed T(H)1-T(H)2 responses in allergic mice, heat-denatured ProDer p 1, compared with native ProDer p 1, proved to be more effective in redirecting the T(H)2-allergic response toward T(H)1. Conclusion: Taken together, our results suggest that variants of Der p 1 with reduced IgE-binding reactivity could represent hypoallergenic molecules suitable for allergen-specific immunotherapy.