Abstract
Purpose :
To investigate the prophylactic or therapeutic effects of oral administration of transgenic rice seeds expressing a modified antigen on allergic conjunctivitis induced by birch pollen in mice.
Methods :
Transgenic rice that deposits a hypoallergenic modified antigen (tree pollen chimera 7, TPC7) in protein bodies of endosperm was generated by DNA shuffling with 14 types of Fagales tree pollen allergens known to cause birch pollen allergy. Whereas TPC7 exhibited low allergenicity [as reflected in its immunoglobulin E (IgE) reactivity and ability to activate basophils], it was highly immunogenic. BALB/c mice were sensitized by two injections of birch pollen in alum and were subsequently challenged three times with pollen in eyedrops. They were fed TPC7 transgenic or nontransgenic (control) rice seeds either for 14 days before sensitization (prophylactic protocol) or for 17 days after sensitization (therapeutic protocol). Clinical signs of allergic conjunctivitis were examined 20 minutes after the last challenge, and the conjunctiva, blood, and spleen were isolated for histological analysis, measurement of serum IgE, or cytokine production assays and flow cytometric analysis, respectively, after 24 hours.
Results :
The clinical score and number of eosinophils in the conjunctiva were significantly lower in mice fed TPC7 transgenic rice than in those fed nontransgenic rice according to either the prophylactic or therapeutic protocol. The serum concentration of allergen-specific IgE did not differ between the TPC7-fed and control groups in either protocol. Prophylatic administration of TPC7 down-regulated the allergen-induced production of interleukin (IL)–4 and interferon (IFN)–γ by, as well as increased the number of CD4+CD25+Foxp3+ regulatory T cells among, isolated splenocytes. Therapeutic administration of TPC7 up-regulated the allergen-induced production of IL-2 and IFN-γ by isolated splenocytes.
Conclusions :
Prophylactic or therapeutic oral administration of transgenic rice seeds expressing modified birch pollen allergen suppressed pollen-induced experimental allergic conjunctivitis in mice. Such feeding with transgenic rice is thus a potentially effective approach to allergen-specific oral immunotherapy for allergic conjunctivitis.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.