Non-injection routes of allergen specific immunotherapy are becoming more and more applicable such as through mucosal surfaces of the mouth. The sublingual route has been established and marketed for humans use as a valid non-invasive alternative to the subcutaneous route (Passalacqua et al., 2019). Eight recombinant allergens have been expressed in barley in collaboration with ORF Genetics (Magnusdottir et al., 2013) They have shown to be comparable with E. coli and insect cell produced allergens in immunoassays (Jonsdottir et al., 2018 and 2021).
A method to treat horses with recombinant barley flour via the oral mucosa using spiral bits was developed. Treated healthy horses developed an IgG response able to partly block IgE-binding to the allergen. (Jonsdottir et al., 2017). More allergens are now being expressed in barley and a more user-friendly method of treatment will be tried on larger number of horses.