Peptide-based immunotherapy in a BALB/c mouse model of orally-induced egg allergy.

摘要

Peptide-based immunotherapy (PIT) represents an attractive approach to develop safe interventions in food allergy, due to its attenuated risk of side-effects. The concept lies in the administration of allergen-derived peptides devoid of IgE-crosslinking activity, but with conserved T-cell determinants in order to maintain immunogenicity. In light of recent reports on the functions of regulatory T cells (Treg), it was hypothesized that T-cell epitope-containing peptides could induce regulatory mechanisms, capable of repressing an allergic response.;Using the SPOTSRTM method, a 12-mer synthetic peptide library spanning the primary sequence of ovalbumin (OVA), a major egg allergen, was constructed and allowed identification of eight B-cell epitope regions. Optimization of an ex vivo splenocyte proliferation assay led to recognition of three immunodominant and one minor T-cell determinants.;Five groups of BALB/c mice were orally sensitized to OVA. Groups B, C and D were subsequently administered (s.c.) single synthetic peptides corresponding to OVA immunodominant T cell epitopes, while group E received a cocktail of the three peptides in equal amounts. Groups A and F served as negative (placebo) and positive (no peptide treatment) control groups, respectively. Following the peptide administration, mice were orally challenged with a high dose of OVA.;Group B, C and E showed lower serum histamine and specific IgE levels compared to group A, and significantly lower anaphylactic scores were obtained in group E. Group D tended to show higher levels for these same parameters. Real-time RT-PCR analysis of mRNA gene expression in ileum indicated a dominant Th1-response in peptide-treated groups, supported by similar cytokine secretion profiles in splenocyte cultures (ELISA). Importantly, groups C and E were characterized by pronounced mRNA expressions of TGF-beta and FOXp3, suggesting the involvement of repressive mechanisms mediated by subsets of Treg cells.;The suitability of a PIT approach in a food industrial context was assessed by orally administering egg-white protein hydrolyzates (≤2.0 kDa) to egg-white sensitized-BALB/c mice. The patterns observed were strongly reminiscent of those obtained in allergic mice desensitized to OVA by administration of synthetic peptides.;This is the first study to demonstrate the therapeutic potential of PIT in an orally-sensitized mouse model of food allergy.