Mycobiome Dysbiosis and Genetic Predisposition for Elevated IL-17A Drive Fibrosis in MASLD

ABSTRACT Metabolic dysfunction-associated steatotic liver disease (MASLD) is the leading cause of chronic liver disease in Western countries. Progression to metabolic dysfunction-associated steatohepatitis (MASH) occurs when fat accumulation in the liver triggers Th17 activation and other inflammatory processes. In this study, we identify the IL17A rs2275913 minor allele variant as a risk factor for fibrosis progression in MASLD patients. In patients with advanced fibrosis, we also observed an increased abundance of fungal CTG species including Candida albicans and Debaryomyces hansenii, which are potent triggers of Th17 responses. Integrating genetic risk-predisposition and mycobiome composition, we show in ex vivo T cell stimulation assays, that donors carrying the minor allele variant of IL17A rs2275913 secreted significantly higher IL-17A levels in response to CTG species. Additionally, MASH patients carrying the IL17A rs2275913 risk allele have elevated Th17/Treg ratios in peripheral blood. Taken together, our data indicate that genetic predisposition for enhanced Th17 responses in the context of mycobiome dysbiosis can trigger MASH progression and liver fibrosis. Graphical AbstractThis Graphical Abstract was created with BioRender.com. Brief summary Increased antifungal immune responses triggered by gut mycobiome dysbiosis in genetically predisposed patients can lead to severe stages of metabolic dysfunction-associated steatotic liver disease. Competing Interest Statement The authors have declared no competing interest. Funding Statement This study was funded by by the IZKF Wuerzburg (project A-401), the Marie Sklodowska-Curie 563 Actions (MSCA), and Innovative Training Networks, H2020-MSCA-ITN-2018, 813781 564 BestTreat and by funds from the Deutsche Forschungsgemeinschaft (DFG) within the 565 Collaborative Research Center CRC 124 FungiNet. Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Ethics committee of the University Wuerzburg gave ethical approval for this work (EK 96/12, 05.09.2012; EK 188/17, 13.01.2020; EK 191/21, 16.08.2021). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Data availability Raw sequences from ITS1 gene sequencing were registered at NCBI under BioProject PRJNA834619. ABBREVIATIONS - aHT - arterial hypertension - ALD - alcohol-associated liver disease - ALT - alanine aminotransferase - AST - aspartate aminotransferase - BCAA - branched-chain amino acid - BS - bland steatosis - C. albicans - Candida albicans - D. hansenii - Debaryomyces hansenii - glm - generalized linear model - HC - healthy control - MAF - minor allele frequency - MASLD - metabolic dysfunction-associated steatotic liver disease - MASH - metabolic dysfunction-associated steatohepatitis - OTU - operational taxonomic unit - TE - transient elastography - rTreg - resting regulatory T cells - S. cerevisiae - Saccharomyces cerevisiae - SCFA - short-chain fatty acid