2.3 Food Allergies
Food allergies are the result of aberrant immune responses towards harmless food antigens; these responses are skewed towards Th2 responses associated with the cytokines IL-4, IL-5 and IL-13. Damage to the skin barrier can trigger or promote the occurrence of a food allergy.34,35 Current treatments for IgE-mediated food allergies are largely confined to the avoidance of allergens, anti-histamine treatments and corticosteroid therapies with low efficacy and many side effects (Table 1). Food allergen immunotherapy has also been extensively studied. This process induces desensitisation and promotes permanent immune tolerance to food allergens by gradually increasing exposure to the allergens;36 however, the incidence of adverse reactions is high and it is a long-term treatment process.37 Most biological agents targeted at food allergies are in the preclinical stage.38
Trx1 treatment has been effective against food allergies in previous studies. For example, the application of Trx1 significantly reduced allergic reactions in a wheat allergy dog model subjected to a skin test; thus, the Trx1 system potentially reduces wheat sensitisation by reducing the number of disulphide bonds in the major protein allergens of wheat.39 Similarly, Trx1 reduces the number of disulphide bonds of β-lactoglobulin, an allergen in bovine milk; the disulphide-reduced protein shows increased sensitivity to pepsin digestion and decreased hypersensitivity in vivo .40 In addition, a Trx1-treated salt-soluble wheat allergen was shown to reduce IgE binding in children with asthma.41 Consistent with these results, active systemic and passive cutaneous anaphylaxis tests on guinea pigs showed that yeast extract rich in Trx1 significantly reduced egg mucin-induced anaphylaxis; it was suggested that the anti-allergic activity of Trx1 itself may play a role in these effects.42 Therefore, Trx1-rich yeast extract could potentially be used to produce fermented foods such as alcoholic beverages and bread. Recently, recombinant rice Trx1 has been shown to improve β-lactoglobulin digestion and decrease its allergenicity, thereby improving the feasibility and practicality of large-scale application because a plant Trx system would be more cost-effective than Escherichia coli or animal Trx systems.43