Immunoprofiling of Alcohol-Activated Hepatic Stellate Cells Reveals Mechanisms of Immune Evasion through NK/T Lymphocyte Checkpoint Signaling

ABSTRACT: Chronic alcohol consumption induces the pathogenic activation of hepatic stellate cells (HSC) and their conversion into proliferative myofibroblasts (Myo), which together constitute a disease hub in alcohol-associated liver disease (AALD). While natural killer (NK) lymphocytes efficiently target early activated HSC and ameliorate liver fibrosis in mouse models of diet- and alcohol-induced liver disease, late-activated HSC evade immune surveillance. To gain insight into evasive resistance mechanisms, we profiled the expression of immunoregulatory ligands by HSC and showed that HSC dynamically express CD80, a B7-family ligand that suppresses NK and T cell responses. Using a mouse model of acute-on-chronic alcohol consumption, we show that combined blockade of the CTLA-4//TIGIT/PD-1 inhibitory checkpoints overcomes this resistance mechanism, promoting the selective elimination of activated HSC (aHSC)/Myo, yet fails to diminish fibrosis or ameliorate liver function. Single-cell transcriptome profiling of liver non-parenchymal cells revealed that checkpoint blockade promotes hepatic infiltration of pro-fibrotic Th1 and Th17 T cell subpopulations, while decreasing immunosuppressive Treg. Strikingly, antibody-directed engagement of the PD-1 and TIGIT checkpoints also fails to reduce fibrosis or improve liver function. Thus, selective targeting of aHSC/Myo may be necessary to achieve significant therapeutic benefit.