Acid ceramidase regulates CD8+ T cell exhaustion via Type I interferon mediated upregulation of PD-L1

Zhongwen Hu¹Hossam Abdelrahman^1*Abdelrahman Elwy¹Fei Kuang¹Swati Dhiman¹Shafaqat Ali²Marcel Marson²Lisa Holnsteiner¹Thamer A Hamdan¹Justa Friebus-Kardash¹Elisa Wiebeck¹Wiebke Hansen^1,3Sven Heiles⁴Stefanie Scheu^5,6Erich Gulbins¹Philipp A Lang⁷Karl Lang^1*Judith Lang¹

• ¹Essen University Hospital, Essen, Germany
• ²Institute of Medical Microbiology and Hospital Hygiene, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University Düsseldorf, Universitätsstraße 1, D-40225 Düsseldorf, Germany., Düsseldorf, Germany
• ³Institute of Medical Microbiology, University Hospital Essen, University of Duisburg-Essen, Hufelandstr. 55, Essen D-45147, Germany, Essen, Germany
• ⁴Leibniz-Institut fur Analytische Wissenschaften - ISAS eV, Dortmund, Germany
• ⁵Institute of Medical Microbiology and Hospital Hygiene, Medical Faculty and University Hospital Düsseldorf, Heinrich Heine University Düsseldorf, Universitätsstraße 1, D-40225 Düsseldorf, Germany, Düsseldorf, Germany
• ⁶Institute of Immunology, University Medicine Rostock, Schillingallee 70, Rostock, 18057, Germany., Rostock, Germany
• ⁷Department of Molecular Medicine II, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany, Düsseldorf, Germany

Besides its robust antiviral activity, type I interferon (IFN-I) also exerts immunomodulatory effects and can even drive pathology during chronic viral infections. Mechanisms that regulate IFN-I induction during virus infection and thereby strongly affect the outcome of disease remain to be defined. Here, using the lymphocytic choriomeningitis virus (LCMV) Docile strain, we identified acid ceramidase (aCDase, Asah1) as a critical lipid-metabolic regulator of endosomal, nucleic acid-driven IFN-I responses and disease outcome during chronic virus infection. aCDase is highly expressed in plasmacytoid dendritic cells (pDCs) and required for robust early IFN-I production. aCDase deficiency resulted in ceramide accumulation, blunting IFN-α/β induction, impairing IFN-I-dependent up-regulation of programmed death-ligand 1 (PD-L1) on antigen-presenting cells and preventing exhaustion of virus-specific CD8⁺ T cells, leading to severe immunopathology. This pathology is abrogated by CD8⁺ T-cell depletion or by adoptive transfer of IFN-Iinduced PD-L1-expressing macrophages. Conversely, limiting ceramide production in acid sphingomyelinase (Asm) deficient mice prevented ceramide-accumulation and pDCs showed accelerated IFN-I induction. Mechanistically, ceramide abundance regulated IFN-I production by altering endosomal signaling microdomains. Collectively, our findings reveal ceramide homeostasis as a key determinant of IFN-I-driven CD8⁺ T cell exhaustion and immunopathology during chronic viral infection and highlight aCDase as a potential therapeutic target.