OC 44.5 - A gut metabolite-based dietary therapy influences FVIII inhibitor production with novel relationships between the gut microbiota, blood metabolome, and immune cell frequencies

Background: Treatment of patients with severe hemophilia A is complicated by the development of Factor VIII (FVIII) inhibitors. We have previously shown that the gut microbiota can regulate systemic humoral immune responses to the FVIII protein through gut microbiota-derived short-chain fatty acids (SCFAs), which have anti-inflammatory properties.

Aims: To determine if dietary supplementation with high-amylose maize starch, acetate, and butyrate (HAMSAB) can attenuate FVIII inhibitor development.

Methods: Hemophilia A mice were randomized and fed ad libitum with HAMSAB for eight weeks. Mice were administered four intravenous infusions of FVIII after four weeks on the diet to evaluate the incidence and magnitude of their anti-FVIII immune response. Plasma, secondary lymphoid tissue (spleen and mesenteric lymph nodes), and cecal contents were analyzed for immunophenotyping, 16S sequencing, and metabolomics. The results were compared to mice receiving an isocaloric control diet.

Results: HAMSAB did not alter the magnitude of anti-FVIII IgG in circulation, but there were significant reductions in the inhibitory capacity of these antibodies and Prdm1 mRNA in the mesenteric lymph nodes. These results were confirmed in ex vivo experiments, where physiologically relevant concentrations of butyrate, but not acetate, suppressed the activation of B and T cells. HAMSAB diet changed the gut microbiota significantly, as observed by the enrichment of SCFA-producing bacteria like Clostridiales and through alterations in functional pathways. Metabolomics profiling of murine plasma samples revealed the activation of redox and tryptophan metabolism pathways. Correlation analysis revealed novel relationships between populations of gut bacteria, blood metabolites, FVIII inhibitor production, and regulatory T cells within the gastrointestinal lymphoid tissue.

Conclusion(s): The combined action of acetate and butyrate influences the anti-FVIII immune response through complex mechanisms involving the gut microbiota and may hold promising benefits for the modulation of FVIII immunogenicity.