ISG15-Induced IL-10 Is a Novel Anti-Inflammatory Myeloid Axis Disrupted during Active Tuberculosis

Abstract

IFN-stimulated gene 15 (ISG15) deficiency in humans leads to severe IFNopathies and mycobacterial disease, the latter being previously attributed to its extracellular cytokine-like activity. In this study, we demonstrate a novel role for secreted ISG15 as an IL-10 inducer, unique to primary human monocytes. A balanced ISG15-induced monocyte/IL-10 versus lymphoid/IFN-γ expression, correlating with p38 MAPK and PI3K signaling, was found using targeted in vitro and ex vivo systems analysis of human transcriptomic datasets. The specificity and MAPK/PI3K-dependence of ISG15-induced monocyte IL-10 production was confirmed in vitro using CRISPR/Cas9 knockout and pharmacological inhibitors. Moreover, this ISG15/IL-10 axis was amplified in leprosy but disrupted in human active tuberculosis (TB) patients. Importantly, ISG15 strongly correlated with inflammation and disease severity during active TB, suggesting its potential use as a biomarker, awaiting clinical validation. In conclusion, this study identifies a novel anti-inflammatory ISG15/IL-10 myeloid axis that is disrupted in active TB.

IFN-Stimulated Gene 15 Is an Alarmin that Boosts the CTL Response via an Innate, NK Cell–Dependent Route

“…However, the gene signature also suggested epithelial tissue repair, as indicated by collagen synthesis and increased expression of IL-24 (48) and ICOSL (49). Its collective properties as a molecule that is released from cells following pathogen challenge and/or cell death and is able to mobilize and activate various leukocytes suggest that free ISG15 acts as an alarmin (50), as has been proposed earlier (51). Another criterion to classify ISG15 as an alarmin is that the candidate molecule is able to activate innate and adaptive immune responses, which we indeed show to be the case for free ISG15.…”

“…Another criterion to classify ISG15 as an alarmin is that the candidate molecule is able to activate innate and adaptive immune responses, which we indeed show to be the case for free ISG15. In our gene set obtained from the vaccinated skin, we did not observe upregulation of IL-10 or IL-6 that were previously shown to be produced by human blood-derived monocytes in response to extracellular ISG15 (51). We also did not find IFN-g that can be produced by human blood-derived lymphoid cells in response to extracellular ISG15 (31)(32)(33).…”

“…Then, cell samples were centrifuged for 5 min at 400 3 g and resuspended in FACS buffer (PBS with 2% FCS; Antibody Production Services). Surface staining with relevant mAbs and allophycocyanin-H-2D b /E7 [49][50][51][52][53][54][55][56][57] tetramers was performed for 30 min on ice. Intracellular staining was performed after cell fixation and permeabilization using Foxp3 Transcription Factor Staining Buffer Set (eBioscience).…”

“…Fluorochrome-labeled mAbs employed were as follows: anti-CD8a-V500 . To detect cytokine production by E7 49-57 -specific CD8 + T cells in dLN and spleen, cells were incubated for 16 h with 1 mg/ml E7 [49][50][51][52][53][54][55][56][57] or no peptide (negative control) in the presence of GolgiPlug (BD Biosciences) in IMDM supplemented with 8% FCS. Flow cytometry was performed using LSRFortessa (BD Biosciences), and data were analyzed with FlowJo software (Tree Star).…”

“…To examine CD8 + T cell activation, we used a DNA vaccine-encoding HPV-16 E7 protein in a shuffled configuration (E7SH) (37,38). This protein contains an immunodominant epitope, E7 [49][50][51][52][53][54][55][56][57] , that is presented by H-2D b (Fig. 2B).…”