Gut virome-colonising Orthohepadnavirus genus is associated with ulcerative colitis pathogenesis and induces intestinal inflammation in vivo

ObjectivesUlcerative colitis (UC) is a chronic inflammatory disorder of unknown aetiology. Gut virome dysbiosis is fundamental in UC progression, although its role in the early phases of the disease is far from fully understood. Therefore, we sought to investigate the role of a virome-associated protein encoded by theOrthohepadnavirusgenus, the hepatitis B virus X protein (HBx), in UC aetiopathogenesis.DesignHBx positivity of UC patient-derived blood and gut mucosa was assessed by RT-PCR and Sanger sequencing and correlated with clinical characteristics by multivariate analysis. Transcriptomics was performed on HBx-overexpressing endoscopic biopsies from healthy donors.C57BL/6 mice underwent intramucosal injections of liposome-conjugated HBx-encoding plasmids or the control, with or without antibiotic treatment. Multidimensional flow cytometry analysis was performed on colonic samples from HBx-treated and control animals. Transepithelial electrical resistance measurement, proliferation assay, chromatin immunoprecipitation assay with sequencing and RNA-sequencing were performed onin vitromodels of the gut barrier. HBx-silencing experiments were performedin vitroandin vivo.ResultsHBx was detected in about 45% of patients with UC and found to induce colonic inflammation in mice, while its silencing reverted the colitis phenotypein vivo. HBx acted as a transcriptional regulator in epithelial cells, provoking barrier leakage and altering both innate and adaptive mucosal immunityex vivoandin vivo.ConclusionThis study described HBx as a contributor to the UC pathogenesis and provides a new perspective on the virome as a target for tailored treatments.