Phenotypic and functional characterisation of liver-infiltrating T-cells in a case of CFTR modulator induced drug-induced liver injury

BACKGROUND: The introduction of CFTR modulators has been transformative for many people with cystic fibrosis (CF). The drugs are generally well tolerated although adverse reactions such as delayed-type T-cell mediated hypersensitivity and drug-induced liver injury (DILI) have been reported. Here, we characterise a novel underlying immunological mechanism driving DILI post Elexacaftor/Tezacaftor/Ivacaftor (ETI) administration. METHODS: Liver-infiltrating T-cells were isolated, post liver biopsy, using a collagenase digestion protocol. Phenotypic analysis of isolated T-cell populations was conducted using flow cytometry and mass cytometry (CyTOF). Lymphocyte transformation tests (LTT) were conducted to detect CFTR modulator-specific T-cell proliferation ([3H]-thymidine). Cytokine analysis was performed using intracellular cytokine staining and enzyme-linked immunospot assays. RESULTS: Liver function tests and histological examination of liver tissue revealed elevated alanine transaminase levels and evidence of perivenular zone three confluent necrosis and hepatocyte loss with mixed inflammatory infiltrate of lymphocytes. T-cells isolated from a percutaneous liver punch biopsy were associated with a dominant CD8+ cellular phenotype. Phenotypic analysis also revealed a CD45RO+ memory phenotype alongside expression of trafficking and migratory markers, such as CXCR3 and LFA-1. In vitro antigen specificity testing demonstrated significant proliferative T-cell responses after exposure to Ivacaftor, Ivacaftor M1 and Ivacaftor M6 metabolites within populations of CD3+ liver-infiltrating T-cells, but not peripheral blood mononuclear cells. CONCLUSIONS: CFTR modulator-specific T-cells appear to be localised to sites of liver injury and not present at high frequencies within peripheral blood. Our findings align with pathomechanisms of immune-mediated DILI, during which drug-activated T-cells migrate towards sites of inflammation, infiltrate tissues and induce hepatotoxicity.