Targeting the FOXP3—T-bet interaction to restore Treg stability in IFN-γ—driven autoimmunity 2254306

Abstract Introduction Regulatory T cells (Tregs) maintain immune homeostasis through FOXP3-centered transcriptional complexes that tightly control lineage stability and suppressive function. However, how specific FOXP3 mutations disturb this complex and drive pathogenic Treg reprogramming in IPEX syndrome remains unclear. We identified a distinctive mechanism by which the FOXP3 V408M mutation promotes Th1-skewed inflammation and also explored a pharmacological strategy to restore Treg stability. Methods We generated FOXP3 V408M knock-in mice and performed immunophenotyping, transcriptomic, and chromatin conformation analyses to determine how the mutation affects FOXP3—T-bet interaction and Ifng transcription. An AI-driven virtual screening strategy integrating sequence- and structure-based modeling was applied to identify compounds that stabilize FOXP3—T-bet interaction. Functional validation was performed in vitro and in multiple in vivo mouse models. Results FOXP3 V408M mutation disrupted the FOXP3—T-bet interaction, thereby releasing T-bet from FOXP3-mediated repression and enhancing Ifng transcription. This defect reprogrammed Tregs toward an IFN-γ—producing phenotype that promoted Th1 inflammation. Among the AI-driven screening hits, 430C10 emerged as a first-in-class FOXP3-targeting stabilizer binding an allosteric pocket within the FKH domain. 430C10 reinforced the FOXP3—T-bet interaction and suppressed T-bet—driven IFN-γ production by Tregs. Oral 430C10 treatment markedly alleviated IFN-γ+ Treg—driven inflammation in FOXP3 V408M mice and improved disease outcomes in an acute colitis model under FOXP3 WT settings. Conclusion Our findings define the FOXP3—T-bet interaction as a tunable checkpoint controlling Treg stability and IFN-γ—driven autoimmunity. Pharmacological stabilization of this interaction with 430C10 provides a proof-of-concept therapeutic strategy for restoring immune homeostasis in IPEX syndrome and related autoimmune diseases. Funding Source Our research is supported by National Natural Science Foundation of China (82271829, 32130041, 82441047, 82241222); The Innovation Program of Shanghai Municipal Education Commission (21140902900); Noncommunicable Chronic Diseases-National Science and Tech Topic Categories Therapeutic Approaches to Autoimmunity (THER)