Sensing antibody functions with a novel CCR8-responsive engineered cell

Human chemokine receptor 8 (CCR8) is a promising drug target for immunotherapy of cancer and autoimmune diseases. Monoclonal antibody-based CCR8 targeted treatment shows significant inhibition in tumor growth. The inhibition of CCR8 results in the improvement of antitumor immunity and patient survival rates by regulating tumor-resident regulatory T cells. Recently monoclonal antibody drug development targeting CCR8 has become a research hotspot, which also promotes the advancement of antibody evaluation methods. Therefore, we constructed a novel engineered customized cell line HEK293-cAMP-biosensor-CCR8 combined with CCR8 and a cAMP-biosensor reporter. It can be used for the detection of anti-CCR8 antibody functions like specificity and biological activity, in addition to the detection of antibody-dependent cell-mediated cytotoxicity and antibody-dependent-cellular-phagocytosis. We obtained a new CCR8 mAb 22H9 and successfully verified its biological activities with HEK293-cAMP-biosensor-CCR8. Our reporter cell line has high sensitivity and specificity, and also offers a rapid kinetic detection platform for evaluating anti-CCR8 antibody functions.

Expression and subcellular analyses of CCR8a/b genes with the identification of response to SGIV viral infect in orange-spotted grouper (Epinephelus coioides)

Chemokine receptors are a superfamily of seven transmembrane domain G-coupled receptors, and they play important roles in immune surveillance, inflammation, and development. Recently, nine CC chemokine receptors (CCRs) were identified and cloned from orange-spotted grouper (Epinephelus coioides) and annotated by phylogenetic and syntenic analyses. We detected mRNA transcripts for CCRs in healthy tissues of E. coioides, and CCR genes were highly expressed in the immune-relevant tissues. Analysis of gene expression after Singapore grouper iridovirus (SGIV) infection indicated that CCR genes are regulated in a gene-specific manner. CCR8a and CCR8b were significantly upregulated in the spleen and liver of resistant fish, indicating potential roles in immunity against the pathogen. Fluorescence microscopy revealed that CCR8a and CCR8b were expressed predominantly in the cytoplasm. Overexpression of CCR8a and CCR8b in grouper cells significantly inhibited the replication of SGIV, demonstrating that they delayed the occurrence of cytopathic effects induced by SGIV infection and inhibited viral gene transcription. CCR8a and CCR8b overexpression also significantly increased the expression of interferon (IFN)-related cytokines and activated IFN response element and IFN promoter activities. These results demonstrated that CCR8a and CCR8b might have an antiviral function against SGIV infect.

CCR8 blockade primes anti-tumor immunity through intratumoral regulatory T cells destabilization in muscle-invasive bladder cancer

Regulatory T cells (Tregs) play a major role in the development of an immunosuppressive tumor microenvironment. Systemic Treg depletion is not favored because of the critical role of Tregs in maintaining immune homeostasis and preventing the autoimmunity. Recently, CCR8 has been identified as an important chemokine receptor expressed on intratumoral Tregs and is known to be critical for CCR8⁺Treg-mediated immunosuppression. However, the inherent molecular mechanisms and clinical significance of intratumoral CCR8⁺Tregs remain poorly understood. In this study, a retrospective analysis of 259 muscle-invasive bladder cancer (MIBC) patients from two independent clinic centers was conducted to explore the prognostic merit of CCR8⁺Tregs via immunohistochemistry. Eighty-three fresh MIBC samples and data from the Cancer Genome Atlas were used to evaluate the proportion and function of immune cells via flow cytometry, ex vivo intervention experiments and bioinformatics analysis. It was found that the CCR8 expression by intratumoral Tregs maintained the stability and potentiated their suppressive function by upregulating the expression of transcript factors FOXO1 and c-MAF. High level of CCR8⁺Tregs was associated with the immune tolerance and predicted poor survival and inferior therapeutic responsiveness to chemotherapy. Moreover, it was revealed that CCR8 blockade could destabilize intratumoral Tregs into a fragile phenotype accompanied with reactivation of antitumor immunity and augment of anti-PD-1 therapeutic benefits in MIBC. In summary, those results suggested that CCR8⁺Tregs represented a stable Treg subtype and a promising therapeutic target in the immunotherapy of MIBC.

Disruption of the CCL1-CCR8 axis inhibits vascular Treg recruitment and function and promotes atherosclerosis in mice

The CC chemokine 1 (CCL1, also called I-309 or TCA3) is a potent chemoattractant for leukocytes that plays an important role in inflammatory processes and diseases through binding to its receptor CCR8. Here, we investigated the role of the CCL1-CCR8 axis in atherosclerosis. We found increased expression of CCL1 in the aortas of atherosclerosis-prone fat-fed apolipoprotein E (Apoe)-null mice; moreover, in vitro flow chamber assays and in vivo intravital microscopy demonstrated an essential role for CCL1 in leukocyte recruitment. Mice doubly deficient for CCL1 and Apoe exhibited enhanced atherosclerosis in aorta, which was associated with reduced plasma levels of the anti-inflammatory interleukin 10, an increased splenocyte Th1/Th2 ratio, and a reduced regulatory T cell (Treg) content in aorta and spleen. Reduced Treg recruitment and aggravated atherosclerosis were also detected in the aortas of fat-fed low-density lipoprotein receptor-null mice treated with CCR8 blocking antibodies. These findings demonstrate that disruption of the CCL1-CCR8 axis promotes atherosclerosis by inhibiting interleukin 10 production and Treg recruitment and function.

CCR8 Expression Defines Tissue-Resident Memory T Cells in Human Skin

Human skin harbors two major T cell compartments of equal size that are distinguished by expression of the chemokine receptor CCR8. In vitro studies have demonstrated that CCR8 expression is regulated by TCR engagement and the skin tissue microenvironment. To extend these observations, we examined the relationship between CCR8+ and CCR8- skin T cells in vivo. Phenotypic, functional, and transcriptomic analyses revealed that CCR8+ skin T cells bear all the hallmarks of resident memory T cells, including homeostatic proliferation in response to IL-7 and IL-15, surface expression of tissue localization (CD103) and retention (CD69) markers, low levels of inhibitory receptors (programmed cell death protein 1, Tim-3, LAG-3), and a lack of senescence markers (CD57, killer cell lectin-like receptor subfamily G member 1). In contrast, CCR8- skin T cells are heterogeneous and comprise variable numbers of exhausted (programmed cell death protein 1+), senescent (CD57+, killer cell lectin-like receptor subfamily G member 1+), and effector (T-bethi, Eomeshi) T cells. Importantly, conventional and high-throughput sequencing of expressed TCR β-chain (TRB) gene rearrangements showed that these CCR8-defined populations are clonotypically distinct, suggesting unique ontogenies in response to separate antigenic challenges and/or stimulatory conditions. Moreover, CCR8+ and CCR8- skin T cells were phenotypically stable in vitro and displayed similar levels of telomere erosion, further supporting the likelihood of a nonlinear differentiation pathway. On the basis of these results, we propose that long-lived memory T cells in human skin can be defined by the expression of CCR8.

Chemokine responsiveness of CD4+ CD25+ regulatory and CD4+ CD25- T cells from atopic and nonatopic donors

BACKGROUND

Allergic inflammation is associated with Th2-type T cells, which can be suppressed by CD4+ CD25+ regulatory T cells (Tregs). Both express chemokine receptors (CCR) 4 and CCR8, but the dynamics of expression and effect of atopic status are unknown.

OBJECTIVE

To examine the expression of chemokine receptors by CD4+ CD25+ and CD4+ CD25- T cells from atopic and nonatopic donors, and document response to allergen stimulation in vitro.

METHODS

Chemokine receptor expression was examined by flow cytometry and quantitative PCR of CD4+ CD25hi and CD4+ CD25- T cells from atopics and nonatopics. Responsiveness to chemokines was by actin polymerization. Dynamics of chemokine receptor expression in 6-day allergen-stimulated cultures was analysed by carboxyfluoroscein succinimidyl ester labelling.

RESULTS

CD4+ CD25hi Tregs preferentially expressed CCR3, CCR4, CCR5, CCR6 and CCR8. CD4+ CD25hi Tregs responded to the chemokine ligands for CCR4, CCR6 and CCR8 (CCL17, 22, 20 and 1 respectively), with no differences between atopic and nonatopic donors. Over 6-day allergen stimulation, CD4+ CD25+ T-cells downregulated CCR4 and upregulated CCR7, in contrast to CD4+ CD25- effector cells, which downregulated CCR7 and upregulated CCR4.

CONCLUSIONS

CCR4, CCR6 and CCR8 have potential roles in localization of both CD4+ CD25+ regulatory and CD4+ CD25- effector T cells to sites of allergic inflammation. Upregulation of CCR7 and downregulation of CCR4 upon allergen stimulation of Tregs may allow their recirculation from sites of inflammation, in contrast to retention of effector T cells.