Single-cell RNA-sequencing of PBMCs from SAVI patients reveals disease-associated monocytes with elevated integrated stress response II

Gain-of-function mutations in STING1, that codes for the Stimulator of Interferon Gene (STING), result in a severe autoinflammatory disease termed STING-associated vasculopathy with onset in infancy (SAVI). Although elevated type I interferon (IFN) production is thought to be the leading cause of the symptoms observed in patients, STING can induce a set of pathways, and their role in the onset and severity of SAVI remains to be elucidated. To address this point, we compared a single-cell RNA sequencing (scRNA-seq) dataset of peripheral blood mononuclear cells (PBMCs) from SAVI patients to a dataset of healthy PBMCs treated with recombinant IFN-ß. We revealed a loss of mucosal associated invariant T cells and CD56bright natural killer cells in SAVI patients, not replicated in IFN-ß-treated PBMC. Patient T cells are in an activated state associated with senescence and apoptosis, dependent on type I IFNs. Inferring cell to cell communication, from scRNA-seq predicted monocytes as potential drivers of this T cell phenotype and was supported by plasma cytokines measurement, with high CCL3, CCL4 and IL-6. Furthermore, scRNA-seq clustering identified a patient-specific subset of monocytes, highly inflammatory and expressing a strong integrated stress response (ISR). It also pinpointed to a patient with lower ISR, allowing us to identify a secondary mutation in PERK, that was recently shown to be activated by STING to trigger the ISR. Finally, based on the identification of this patient-specific subset of monocytes and the exploration of IFN-ß stimulated PBMCs from healthy donors, we developed a strategy to propose a transcriptomic signature specific of STING activation and independent of type I IFN. Altogether, these results provide a deeper understanding of SAVI at the cellular and molecular levels. Overall design: 7 CTRL, 5 untreated SAVI patients, and 4 SAVI patients treated with a JAK-inhibitor (including 2 samples for the first patient)