Background: Respiratory birch pollen allergy and associated oral allergy syndrome affect more than 150 million people. IgE cross-sensitization to major birch pollen allergen Bet v 1 and pathogenesis-related (PR10) plant food allergens is responsible for the pollen-food allergy syndrome. Methods: We designed a recombinant protein, AB-PreS, consisting of non-allergenic peptides derived from the IgE binding sites of Bet v 1 and the cross-reactive apple allergen, Mal d 1, fused to the PreS domain of HBV surface protein as immunological carrier. AB-PreS was expressed in E. coli and purified by chromatography. The allergenic activity of AB-PreS was tested using sera and basophils from birch pollen patients allergic. The protective effect of AB-PreS was assessed by inhibition ELISA test using sera allergic patients and from immunized rabbits. Results: IgE-binding experiments and basophil activation test revealed the hypoallergenic nature of AB-PreS. IgG antibodies induced by 5 injections with AB-PreS inhibited allergic patients’ IgE binding to Bet v 1 and Mal d 1 better than did IgG induced by up to 30 injections of six licensed birch pollen allergen extract-based vaccines. Additionally, immunization with AB-PreS induced HBV-specific antibodies potentially protecting the infection. Conclusion: The recombinant AB-PreS-based vaccine is hypoallergenic, safe and superior to currently registered allergen extract-based vaccines for the treatment of the birch pollen food allergy syndrome.

Background. First vaccines for prevention of Coronavirus disease 2019 (COVID-19) are becoming available but there is a huge and unmet need for specific forms of treatment. In this study we aimed to evaluate the potent anti-SARS-CoV-2 effect of siRNA both in vitro and in vivo. Methods. To identify most effective molecule out of a panel of 15 in silico designed siRNAs, an in vitro screening system based on vectors expressing SARS-CoV-2 genes fused with the firefly luciferase reporter gene and SARS-CoV-2-infected cells was used. The most potent siRNA, siR-7, was modified by Locked nucleic acids (LNAs) to obtain siR-7-EM with increased stability and was formulated with the peptide dendrimer KK-46 for enhancing cellular uptake to allow topical application by inhalation of the final formulation - siR-7-EM/KK-46. Using the Syrian Hamster model for SARS-CoV-2 infection the antiviral capacity of siR-7-EM/KK-46 complex was evaluated. Results. We identified the siRNA, siR-7, targeting SARS-CoV-2 RNA-dependent RNA polymerase (RdRp) as the most efficient siRNA inhibiting viral replication in vitro. Moreover, we have shown that LNA-modification and complexation with the designed peptide dendrimer enhanced the antiviral capacity of siR-7 in vitro. We demonstrated significant reduction of virus titer and total lung inflammation in the animals exposed by inhalation of siR-7-EM/KK-46 in vivo. Conclusions. Thus, we developed a therapeutic strategy for COVID-19 based on inhalation of a modified siRNA-peptide dendrimer formulation.