Iron-induced chelation alleviates the potential allergenicity of ovotransferrin in a BALB/c mouse model

Ovotransferrin (OVT) is one of the main egg allergens with 2 iron-binding sites. Several studies have demonstrated that iron-chelation decreased the allergenicity of milk allergen and birch pollen allergens. Therefore, we hypothesized that iron-chelation could also reduce the allergenicity of OVT. Apo-OVT (iron-free OVT, the natural state in egg white) and Holo-OVT (iron-chelated OVT) were prepared, and the allergenicity of them were assessed and compared using a BALB/c mouse model as well as dendritic cells (DCs) based on antigen uptake. Mice were orally sensitized with Apo-OVT or Holo-OVT using cholera toxin as adjuvant. Clinical signs of allergy, morphological structure of jejunum, specific antibody levels, mast cell protease-1 (mMCP-1) concentrations, cytokines and antigen uptake by DCs were determined after the mice were challenged with Apo-OVT or Holo-OVT. Results showed that both Apo-OVT and Holo-OVT induced intestinal allergy, but no systematic allergic symbols were observed. Serum levels of mouse mast cell protease-1 (mMCP-1) and specific IgE in Apo-OVT group were lower than in control group, and no significant difference between Apo-OVT group and Holo-OVT group (P>.05). The levels of OVT-specific IgG and IgG1, as well as the Th-1 cytokine interferon gamma and Th2-type cytokine interleukin-13 in Holo-OVT sensitized mice were significantly decreased compared to Apo-OVT group (P<.05), while no significant difference with control group (P>.05). However, DCs took in less Apo-OVT than Holo-OVT. Overall, iron-induced chelation could alleviate the potential allergenicity of OVT in vivo.