PD1 blockade promotes IFN- production by progenitor exhausted PD1-expressing T cells in atherosclerotic plaques

Abstract Objective: Interferon-γ (IFN-γ) is a key cytokine regulating the development of atherosclerosis, but little is known regarding the phenotype and regulation of T cells producing IFN-γ in plaques. Methods: To identify and characterize IFN-γ-producing T cells in the development atherosclerosis, we utilized IFN-γ-YFP and Nur77-GFP reporter mice crossed onto an atherosclerotic background (Apoe−/−IFN-γ YFP/YFP; Apoe−/−Nur77GFP/wt), adoptive transfer of transgenic ApoB-reactive T-cells into mice containing humanized ApoB100 (HuBL mice), and treatment with immune checkpoint inhibitors in atherosclerotic mice. Results: Aortic CD4 +and CD8 +T cells producing IFN-γ were a complex set of cells comprised predominantly of “progenitor exhausted” PD1-intermediate (PD1 int) SLAMF6 +IL7R +T cells and a minor population of “terminally exhausted” PD1 hiTOX +T cells. However, both PD1 intand PD1 hiplaque T cells were Ki67 +and displayed elevated levels of recent TCR signaling (Nur77-GFP +). ApoB-specific transgenic CD4 +T cells adoptively transferred to a hypercholesterolemic HuBL mice showed sign of early exhaustion, upregulating PD1, TOX, and Tim3. Finally, PD1 blockade in mice with advanced atherosclerosis resulted in increased levels of IFN-γ production of plaque-infiltrating CD4 +and CD8 +T cells. Conclusion: IFN-γ-producing T cells in the atherosclerotic plaque display markers classically associated with an exhausted T cell phenotype but still produce cytokines, proliferate, and are responsive to anti-PD1 treatment. Our study suggests that PD1 signaling regulates T cell IFN-γ production in plaques and reveals a potential mechanism by which immune checkpoint blockade therapy aggravates cardiovascular disease. Supported by grants from Swedish Heart-Lung Foundation (#20200522, #20190449) sourced by Daniel Engelbertsen.