Single-cell immune checkpoint landscape of PBMCs stimulated with Candida albicans

Immune checkpoints play various important roles in tumour immunity, which usually contribute to T cells' exhaustion, leading to immunosuppression in the tumour microenvironment. However, the roles of immune checkpoints in infectious diseases, especially fungal infection, remain elusive. Here, we reanalyzed a recent published single-cell RNA-sequencing (scRNA-seq) data of peripheral blood mononuclear cells (PBMCs) stimulated with Candida albicans (C. albicans), to explore the expression patterns of immune checkpoints after C. albicans bloodstream infection. We characterized the heterogeneous pathway activities among different immune cell subpopulations after C. albicans infection. The CTLA-4 pathway was up-regulated in stimulated CD4(+) and CD8(+) T cells, while the PD-1 pathway showed high activity in stimulated plasmacytoid dendritic cell (pDC) and monocytes. Importantly, we found that immunosuppressive checkpoints HAVCR2 and LAG3 were only expressed in stimulated NK and CD8(+) T cells, respectively. Their viabilities were validated by flow cytometry. We also identified three overexpressed genes (ISG20, LY6E, ISG15) across all stimulated cells. Also, two monocyte-specific overexpressed genes (SNX10, IDO1) were screened out in this study. Together, these results supplemented the landscape of immune checkpoints in fungal infection, which may serve as potential therapeutic targets for C. albicans infection. Moreover, the genes with the most relevant for C. albicans infection were identified in this study.