Oral administration of transgenic barley expressing a Culicoides allergen induces specific antibody response.

This study investigates the effectiveness of an allergen from the Culicoides insect, expressed in barley grains using the Orfeus technique, in inducing an immune response against insect bite hypersensitivity in horses. Through oral administration to Icelandic horses, the researchers found that the transgenic barley prompted a specific antibody response, suggesting that this approach may provide an alternative treatment or preventative measure against equine insect bite hypersensitivity.

Objectives and Methodology

• The primary goal of this study was to express a Culicoides allergen in barley and determine if feeding this transgenic barley to healthy Icelandic horses would induce a specific immune response. This was evaluated through an in vivo experiment.
• The allergen used comes from the salivary gland of the Culicoides nubeculosus (Cul n 2), a type of midge. Specifically, the allergen expressed is a hyaluronidase, which is an enzyme that helps spread the allergic response.
• Icelandic horses were used because the prevalence of hypersensitivity is particularly higher among those born in Iceland and exported, comparing to those born in environments rich in Culicoides. Thus, there is heightened need for effective immunotherapy for these horses.
• Seven Icelandic horses were orally treated with barley flour, using a specially designed device. Of them, four received transgenic barley, while three received control barley.
• Serum and saliva samples were collected from the horses to measure the specific antibodies developed following the treatment.

Results and Conclusion

• Results showed that horses treated with the transgenic barley developed a specific immune response (IgG1 and IgG4/7) to the Cul n 2 allergen, as evidenced in both serum and saliva samples.
• The immune response in the horses treated with the transgenic barley was significantly different from those treated with control barley.
• Notably, the induced serum antibodies also recognized the corresponding allergen from Culicoides obsoletus (rCul o 2), demonstrating cross-reactivity.
• Importantly, these antibodies appeared to partially inhibit binding of specific IgE from horses affected by insect bite hypersensitivity. It indicates that antibodies produced could neutralize the allergic response, offering a potential therapeutic strategy.
• The study concludes that specific antibody responses can be successfully triggered in horses not previously exposed to Culicoides, through the oral intake of barley grains that express the insect allergen. The research suggests that this methodology could potentially serve as a preventative measure or alternative treatment for equine hypersensitivity.
• However, the study acknowledges the limitations of its small sample size and highlights the need for further research to ascertain the wider applicability and efficacy of this immunotherapeutic approach.