Introduction:: Despite the potential of oral immunotherapy (OIT) for food allergy treatment, adverse events and risk of relapse still remain significant challenges. While dysbiosis of the gut microbiota is implicated in food allergy [1], it is unknown how to effectively modulate the gut microbiota and metabolites for successful OIT. We have developed an engineered inulin gel loaded with allergen (inulin gel/allergen) that can remodel the gut microbiota and metabolites in situ, achieving robust OIT efficacy and sustained unresponsiveness in murine models of food allergy.
Materials and Methods:: Inulin gel/OVA was prepared using a heating-cooling process [2]. Rheology tests, pharmacokinetics study, and in vivo uptake assay were performed. Balb/c mice were sensitized with alum/OVA. After OIT treatment, the mice received repeated oral challenges with OVA and anaphylactic reactions and diarrhea were monitored. Small intestinal tissues were collected and analyzed by single cell RNA sequencing (scRNA-seq) and flow cytometry. Fecal pellets and ileal contents were collected after OIT for 16s rRNA gene sequencing and untargeted metabolomics analyses.
Results, Conclusions, and Discussions:: Results: Engineering inulin and OVA into the gel formulation increased its physical strength, viscosity, and retention in the intestines. OIT with inulin gel/allergen exerted robust therapeutic efficacy against food allergy (Figure 1). Mechanistically, antigen uptake was facilitated by macrophage-like DCs after being loaded to inulin gel. ScRNA-seq and flow cytometry data revealed inulin gel/OVA OIT increased Tregs and decreased Th2 cells, compared with OVA OIT. Microbial and unbiased global metabolites analyses in the ileal contents revealed normalized microbial and metabolites profiles after inulin gel/OVA OIT treatment, whereas OVA OIT resulted in high dissimilarities to the profiles of naïve mice. Intriguingly, inulin gel/OVA OIT restored several metabolic pathways, including nucleotides metabolism, citric acid cycle metabolism and short-chain fatty acid metabolism.
Discussion: Inulin gel/allergen promoted antigen uptake by DCs, modulated intestinal microbiome and metabolites and skewed differentiation of CD4 T cells into IFN-g and IL-10 producing regulatory cells. Our current work reveals the diversity and alterations in the compositions of small intestinal microbiota and metabolites, providing new insights into targeting microbiome-immune axis for therapeutic interventions.
Conclusion: We have developed a novel dietary fiber-based oral allergen delivery system that can induce tolerogenic intestinal environment and allergy desensitization. Our findings highlight the therapeutic potential of engineered gel/allergen formulations as a novel microbiome- and immune-modulating platform for the treatment of food allergies.
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References (Optional): : 1. Stephen-Victor, E. et al. Dietary and microbial determinants in food allergy. Immunity 53, 277-289 (2020).
2. Han, K. et al. Generation of systemic anti-tumor immunity via the in situ modulation of the gut microbiome by an orally administered inulin gel. Nature biomedical engineering 5, 1377-1388 (2021).