STAT1-L351F is associated with enhanced interferon signaling and susceptibility toinfection.

Abstract

INTRODUCTION: Talaromyces marneffei can cause life-threatening disseminated infection, yet the immune alterations linking STAT1 gain-of-function (GOF) variants, including the previously reported L351F site, to talaromycosis remain incompletely defined. METHODS: We investigated STAT1-L351F in a four-member pedigree in which disease was restricted to the proband, combining human immunophenotyping, mechanistic assays, and an in vivo infection model. Systemic immune status was assessed by serum cytokine profiling, and peripheral blood mononuclear cell (PBMC) antifungal control was quantified using CFU-based ex vivo growth assays with T. marneffei, with extension to Cryptococcus neoformans and Candida albicans. STAT1 signaling was evaluated in HEK293T cells expressing STAT1-WT or STAT1-L351F by measuring IFN-α/β/γ-induced STAT1 phosphorylation and interferon-stimulated response element/gamma-activated sequence (ISRE/GAS) reporter activity. Wild-type and Stat1-L351F knock-in mice were challenged intranasally with T. marneffei and analyzed for lung fungal burden, histopathology, immune profiling, and bulk lung transcriptomics; infected Stat1-L351F mice additionally received ruxolitinib to probe the impact of JAK inhibition on infection-associated myeloid responses. RESULTS: The proband displayed an interferon-skewed cytokine milieu, and patient PBMCs supported increased ex vivo growth of T. marneffei and C. neoformans, whereas C. albicans did not show a consistent increase. STAT1-L351F was associated with increased IFN-induced STAT1 phosphorylation and enhanced ISRE/GAS reporter activity, consistent with a hyper-responsive interferon signaling state in this system. In vivo, female Stat1-L351F mice developed higher lung fungal burden and more severe pathology at 16 days post-infection, accompanied by reduced NKT-cell frequencies and broad transcriptomic remodeling characterized by type I interferon-biased signatures together with dysregulated myeloid/neutrophil effector and IL-17-related programs. Ruxolitinib partially attenuated infection-associated expansion of myeloid-derived suppressor cell subsets. DISCUSSION: Overall, STAT1-L351F was associated with impaired antifungal control, selective ex vivo permissiveness to distinct fungal pathogens, and altered IL-17-linked immune programs during T. marneffei infection, providing a multi-layered framework for understanding how dysregulated STAT1 signaling may reshape antifungal immunity across human, cell-based, and in vivo systems.