Elevated plasma levels of CXCL16 in severe COVID-19 patients.

Genome-wide association studies have recently identified 3p21.31, with lead variant pointing to the CXCR6 gene, as the strongest thus far reported susceptibility risk locus for severe manifestation of COVID-19. In order the determine its role, we measured plasma levels of Chemokine (C-X-C motif) ligand 16 (CXCL16) in the plasma of COVID-19 hospitalized patients. CXCL16 interacts with CXCR6 promoting chemotaxis or cell adhesion. The CXCR6/CXCL16 axis mediates homing of T cells to the lungs in disease and hyper-expression is associated with localised cellular injury. To characterize the CXCR6/CXCL16 axis in the pathogenesis of severe COVID-19, plasma concentrations of CXCL16 collected at baseline from 115 hospitalized COVID-19 patients participating in ODYSSEY COVID-19 clinical trial were assessed together with a set of controls. We report elevated levels of CXCL16 in a cohort of COVID-19 hospitalized patients. Specifically, we report significant elevation of CXCL16 plasma levels in association with severity of COVID-19 (as defined by WHO scale) (P-value < 0.02). Our current study is the largest thus far study reporting CXCL16 levels in COVID-19 hospitalized patients (with whole-genome sequencing data available). The results further support the significant role of the CXCR6/CXCL16 axis in the immunopathogenesis of severe COVID-19 and warrants further studies to understand which patients would benefit most from targeted treatments.

CXCL16/CXCR6-mediated adhesion of human peripheral blood mononuclear cells to inflamed endothelium.

The endothelial chemokine CXC motif ligand 16 (CXCL16) is involved in the recruitment and firm adhesion of CXCR6+ cells to the atherosclerosis-prone aortic vessel wall. Recently we showed that CXCR6+ platelets from flowing blood attach to CXCL16 expressed by activated endothelium on the luminal side of the blood vessel. With this study we supplement these findings with the observation that platelets bound to the inflamed endothelium are presenting CXCR6 to CXCL16-positive peripheral blood mononuclear cells (PBMCs) and, thus, are mediating an increased adhesion of PBMCs to the arterial wall. Furthermore we identified endothelial CXCL16 as an important adhesion molecule promoting the firm adhesion of CXCR6-positive PBMCs to inflamed endothelium. Our results demonstrate that endothelial CXCL16 as well as platelet CXCR6 are acting as potent PBMC-adhesion ligands, inducing PBMC-adhesion to the atherosclerosis-prone vessel wall and thus promoting the progression of atherosclerosis.

Expression of CCR6 and CXCR6 by Gut-Derived CD4+/CD8α+ T-Regulatory Cells, Which Are Decreased in Blood Samples From Patients With Inflammatory Bowel Diseases.

BACKGROUND & AIMS: Faecalibacterium prausnitzii, a member of the Clostridium IV group of the Firmicutes phylum that is abundant in the intestinal microbiota, has anti-inflammatory effects. The relative level of F prausnitzii is decreased in fecal samples from patients with inflammatory bowel diseases (IBDs) compared with healthy individuals. Reduced F prausnitzii was correlated with relapse of Crohn's disease after surgery. We identified, in human colonic mucosa and blood, a population of T regulatory type 1-like T regulatory (TREG) cells that express CD4 and CD8α (DP8α T cells) and are specific for F prausnitzii. We aimed to determine whether they are altered in patients with IBD. METHODS: We isolated DP8α T cells from human colon lamina propria and blood samples and used flow cytometry to detect markers of cells that are of colon origin. We quantified DP8α cells that express colon-specific markers in blood samples from 106 patients with IBD, 12 patients with infectious colitis, and 35 healthy donors (controls). We identified cells that respond to F prausnitzii. Cells were stimulated with anti-CD3, and their production of interleukin 10 was measured by enzyme-linked immunosorbent assay. We compared the frequency and reactivity of cells from patients vs controls using the 2-sided Student t test or 1-way analysis of variance. RESULTS: Circulating DP8α T cells that proliferate in response to F prausnitzii express the C-C motif chemokine receptor 6 (CCR6) and C-X-C motif chemokine receptor 6 (CXCR6). These cells also have features of TREG cells, including production of IL-10 and inhibition of T-cell proliferation via CD39 activity. The proportion of circulating CCR6+/CXCR6+ DP8α T cells was significantly reduced (P < .0001) within the total population of CD3+ T cells from patients with IBD compared with patients with infectious colitis or controls. A threshold of <7.875 CCR6+/CXCR6+ DP8α T cells/10,000 CD3+ cells discriminated patients with IBD from those with infectious colitis with 100% specificity and 72.2% sensitivity. CONCLUSIONS: We identified a population of gut-derived TREG cells that are reduced in blood samples from patients with IBD compared with patients with infectious colitis or controls. These cells should be studied further to determine the mechanisms of this reduction and how it might contribute to the pathogenesis of IBD and their prognostic or diagnostic value.

Peripheral cytokines, C-X-C motif ligand10 and interleukin-13, are associated with Malaysian Alzheimer's disease.

AIM: Cytokines released from chronically-activated microglia could result in neuroinflammation. An accurate profile of the relationship between cytokines and Alzheimer's disease (AD) pathogenesis, as well as the patterns of these inflammatory mediators in AD patients could lead to the identification of peripheral markers for the disease. The present study was undertaken to identify pro- and anti-inflammatory cytokines associated with AD in the Malaysian population. METHODS: Further to informed consent from 39 healthy subjects and 39 probable AD patients, 8.5 mL of peripheral blood was collected and serum was extracted. The differential levels of 12 serum cytokines extracted from peripheral blood samples were measured using Procarta Multiplex Cytokine and enzyme-linked immunoassay kits. Concentrations of cytokines were measured at 615 nm using a fluorometer. RESULTS: Except for tumor necrosis factor-α, all classical pro-inflammatory cytokines (interleukin [IL]-1ß, IL-6, IL-12 and interferon-γ) were found to be significantly upregulated (P < 0.001) in AD patients. Three of the five non-classical pro-inflammatory cytokines (C-X-C motif ligand 10 [CXCL-10], monocyte chemoattractant protein-1 and macrophage inflammatory protein-1α) showed similar patterns. Both classical IL-10 and non-classical IL-13 anti-inflammatory cytokines were significantly downregulated (P < 0.001) in AD patients when compared with non-AD controls. Receiver operating characteristic curve analyses for both CXCL-10 (IP-10) and IL-13 showed a high level of diagnostic accuracy (area under curve = 1 [95% confidence interval]). Both CXCL-10 and IL-13 also showed sensitivity of 100% and specificity of 100% for diagnosis of AD (cut-off values >53.65 ρg/mL and <9.315 ρg/mL, respectively). CONCLUSIONS: Both the non-classical pro-inflammatory CXCL-10 and anti-inflammatory IL-13 cytokines showed promising potential as blood-based cytokine biomarkers for AD. This is the first study of non-classical cytokine profiles of Malaysian AD patients. Geriatr Gerontol Int 2017; 17: 839-846.