The spread of type I allergic diseases has reached epidemic dimensions. The success of therapeutic intervention is limited, and hence prophylactic vaccination is now seriously considered. However, immunization of healthy individuals requires safety standards far beyond those applicable for therapeutic approaches. mRNAs encoding allergen molecules represent an attractive tool for preventive vaccination because of the inherent safety features of this vaccine type.

In the current study we investigated whether mRNA constructs would be capable of protecting against type I allergic reactions in a murine model using the grass pollen allergen Phl p 5 and 28 other major pollen, food, animal, mold, and latex allergens.

BALB/c mice were immunized intradermally either with conventional or replicase-based mRNA constructs. Subsequently, animals were sensitized by means of subcutaneous injection of allergen/alum, followed by airway provocation. IgG1/IgG2a/IgE titers were determined by using ELISAs. Allergen-specific functional IgE levels were assessed by using the basophil release assay. Measurement of cytokines in splenocyte cultures and bronchoalveolar lavage fluids were performed by using enzyme-linked immunosorbent spot assays/sandwich ELISAs. Eosinophil and CD8⁺ counts in bronchoalveolar lavage specimens were determined by means of flow cytometry. Airway hyperreactivity was assessed with whole-body plethysmography and invasive resistance/dynamic compliance measurement.

mRNA vaccination proved its antiallergic efficacy in terms of IgG subclass distribution, functional IgE suppression, reduction of IL-4 and IL-5 levels, induction of IFN-γ–producing cells, and reduction of airway hyperreactivity and eosinophil counts in the lung.

Immunization with mRNA induces T_H1-biased immune responses similar to those elicited through DNA-based vaccination but additionally offers the advantage of a superior safety profile.