Targeting chemokine crosstalk between T-cells and macrophages to treat immune checkpoint inhibito-mediated myocarditis

Immune checkpoint inhibitors (ICIs) are effective against many cancers but can also cause immune-related adverse events. Although rare, ICI-mediated myocarditis has a high fatality rate of up to 40% and is also associated with heart failure and life-threatening arrhythmias. We characterized a population of CXCL9+CXCL10+ macrophages and CXCR3hi CD8+ T-cells in the hearts of mice with myocarditis and elucidated chemokine crosstalk between the CXCR3hi CD8+ effector T-cells and the CXCL9+CXCL10+ macrophages in the heart. Depletion of macrophages or blockade of CXCR3 both resulted in significantly decreased immune cell infiltration in the hearts of mice. Similarly, CXCR3 blockade decreased immune cell infiltration into the heart,, thus posing CXCR3 and its ligands as an attractive therapeutic target. Additionally, an in vitro transwell assay showed that selective blockade of CXCR3 and its ligand CXCL10 significantly decreased CD8+ T-cell migration towards macrophages, implicating this interaction in T-cell cardiotropism towards cardiac macrophages. These findings were compared with cardiac biopsies from patients with ICI myocarditis that also demonstrated infiltrating CXCR3+ lymphocytes and CXCL9+/CXCL10+ macrophages. In both mouse cardiac immune cells and patient peripheral blood immune cells, T-cell receptor (TCR)-sequencing revealed expanded TCRs that correlated with CXCR3hi CD8+ T-cells. The identification of a CXCR3-specific T-cell and macrophage interaction as important in the pathogenesis of ICI myocarditis offers a new potential target for a chemokine/chemokine receptor inhibition-focused form of therapy in this disease.