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