Chemokine Receptor CCR5 Research Articles

Global computational analyses of APEX proximity biotinylation data reveal distinct trafficking rules of chemokine receptors CCR2 and CCR5

Global computational analyses of APEX proximity biotinylation data reveal distinct trafficking rules of chemokine receptors CCR2 and CCR5

Patients with ankylosing spondylitis present a distinct CD8 T cell subset with osteogenic and cytotoxic potential

ObjectivesAnkylosing spondylitis (AS) is a chronic inflammatory rheumatic disease affecting mainly the axial skeleton. Peripheral involvement (arthritis, enthesitis and dactylitis) and extra-musculoskeletal manifestations, including uveitis, psoriasis and bowel inflammation, occur...

Progression of retinal choroidal neovascularizationby latent human cytomegalovirus infection and immunological signaling among neonatal patients admitted to tertiary care hospital.

Choroidal neovascularization (CNV) is a serious condition that affects the retina, causing partial or complete blindness in people of different ages. While CNV is a common occurrence in various chorioretinopathies, research on its occurrence in neonates is limited. Human cytomegalovirus (HCMV) is a significant health threat to neonates, with a strong association with retinal angiogenesis. However, there has been limited investigation into HCMV-associated CNV progression. In this article, we extensively studied the expression of different inflammatory cytokines and chemokines during latent HCMV-associated retinal neovascularization. Our research found that HCMV-induced CNV progression was significantly prominent in the presence of AT2R-dependent angiogenesis (p < 0.001), whereas in the absence of HCMV, AT1R-dependent CCL-5-mediated angiogenesis was documented. We also observed significant increases in CCL-19, CCL-21 chemokine responses, followed by CCR-7 chemokine receptor activation (p < 0.001) in HCMV-induced CNV patients compared to HCMV non-induced CNV groups. Furthermore, significant changes in predictive chemokine markers of HCMV-induced CNV were positively correlated with HCMV viremia. These immunological alterations ultimately lead to the switching of NFκB canonical and noncanonical pathways, respectively, in HCMV-induced neonatal CNV and HCMV non-induced CNV. This clinical observation presents a novel hypothesis that ocular HCMV latency poses a noteworthy risk factor for the progression of retinal neovascularization through a distinctive immunological signaling pathway. The current study represents the first of its kind to report on this association, which may have significant implications for the clinical management of patients with ocular HCMV.

Arylsulfatases and neuraminidases modulate engagement of CCR5 by chemokines by removing key electrostatic interactions

The chemokine receptor CCR5 is known to exist in cell surface subpopulations that differ in their capacity to engage ligands. One proposed explanation for this phenomenon is the presence of CCR5 species with different levels of post-translational modifications (PTMs). Tyrosine sulfation and O-glycan sialylation are PTMs that add negative charges to the extracellular domain of CCR5 and make strong contributions to chemokine binding but it is not known whether cellular mechanisms to control their levels exist. In this study we used a combination of sulfation-sensitive and sulfation-insensitive CCR5 ligands to show that the rate of turnover of CCR5 tyrosine sulfation is more rapid than the rate of turnover of the receptor itself. This suggests that the steady state level of CCR5 sulfation is maintained through the combination of tyrosine protein sulfotransferase (TPST), the trans-Golgi network (TGN)-resident ‘source enzyme, and a ‘sink’ activity that removes tyrosine sulfation from CCR5. By measuring the effects on ligand binding of knockdown and overexpression experiments, we provided evidence that non-lysosomal cellular arylsulfatases, particularly ARSG, ARSI and ARSJ, are CCR5 sulfation ‘sink’ enzymes. We also used targeted knockdown and sialylation-sensitive and insensitive chemokines to identify the sialidase NEU3 as a candidate ‘sink’ enzyme for CCR5 O-glycan sialylation. This study provides the first experimental evidence of activity of sulfatase and sialidase ‘sink’ enzymes on CCR5, providing a potential mechanism for cells to control steady-state levels of these PTMs and thereby exert dynamic control over receptor-ligand interactions at the cell surface and during receptor desensitization.

The chemokine receptor CCR8 is not a high-affinity receptor for the human chemokine CCL18.

The primate-specific chemokine CCL18 is a potent chemoattractant for T cells and is expressed at elevated levels in several inflammatory diseases. However, the cognate receptor for CCL18 remains unconfirmed. Here, we describe attempts to validate a previous report that the chemokine receptor CCR8 is the human CCL18 receptor (Islam et al. J Exp Med. 2013, 210:1889-98). Two mouse pre-B cell lines (4DE4 and L1.2) exogenously expressing CCR8 exhibited robust migration in response to the known CCR8 ligand CCL1 but not to CCL18. Similarly, CCL1 but not CCL18 induced internalization of CCR8 on 4DE4 cells. CCR8 expressed on Chinese hamster ovarian (CHO) cells mediated robust G protein activation, inhibition of cAMP synthesis and β-arrestin2 recruitment in response to CCL1 but not CCL18. Several N- and C-terminal variants of CCL18 also failed to stimulate CCR8 activation. On the other hand, and as previously reported, CCL18 inhibited CCL11-stimulated migration of 4DE4 cells expressing the receptor CCR3. These data suggest that CCR8, at least in the absence of unidentified cofactors, does not function as a high affinity receptor for CCL18.

Influence of genetic polymorphism of the chemokine receptor CCR5 on clinical course of coronary artery disease and results of percutaneous coronary interventions

Influence of genetic polymorphism of the chemokine receptor CCR5 on clinical course of coronary artery disease and results of percutaneous coronary interventions

The BET inhibitor apabetalone decreases neuroendothelial proinflammatory activation in vitro and in a mouse model of systemic inflammation.

Brain vascular inflammation is characterized by endothelial activation and immune cell recruitment to the blood vessel wall, potentially causing a breach in the blood - brain barrier, brain parenchyma inflammation, and a decline of cognitive function. The clinical-stage small molecule, apabetalone, reduces circulating vascular endothelial inflammation markers and improves cognitive scores in elderly patients by targeting epigenetic regulators of gene transcription, bromodomain and extraterminal proteins. However, the effect of apabetalone on cytokine-activated brain vascular endothelial cells (BMVECs) is unknown. Here, we show that apabetalone treatment of BMVECs reduces hallmarks of in vitro endothelial activation, including monocyte chemoattractant protein-1 (MCP-1) and RANTES chemokine secretion, cell surface expression of endothelial cell adhesion molecule VCAM-1, as well as endothelial capture of THP-1 monocytes in static and shear stress conditions. Apabetalone pretreatment of THP-1 downregulates cell surface expression of chemokine receptors CCR1, CCR2, and CCR5, and of the VCAM-1 cognate receptor, integrin α4. Consequently, apabetalone reduces THP-1 chemoattraction towards soluble CCR ligands MCP-1 and RANTES, and THP-1 adhesion to activated BMVECs. In a mouse model of brain inflammation, apabetalone counters lipopolysaccharide-induced transcription of endothelial and myeloid cell markers, consistent with decreased neuroendothelial inflammation. In conclusion, apabetalone decreases proinflammatory activation of brain endothelial cells and monocytes in vitro and in the mouse brain during systemic inflammation.

Metformin-induced reduction of CCR8 enhances the anti-tumor immune response of PD-1 immunotherapy in glioblastoma

Immunotherapy strategies targeting the programmed cell death 1 (PD-1) in clinical treatments have shown limited success in controlling glioblastoma malignancies. Metformin exserts antitumor function, yet the underlying mechanisms remain unclear. Here, we investigated whether metformin could enhance the effectiveness of anti-PD-1 therapy by activating the immune system. Whether combination of an anti-PD-1 antibody or not, metformin significantly increased tumor-infiltrating CD4+ T cells while decreased regulatory T (Treg) cells in a mouse GBM model. Additionally, metformin reduced CC motif chemokine receptor CCR8 and elevated Interleukin 17 A (IL-17 A) expressions. Mechanistically, metformin reduces histone acetylation at the CCR8 promotor and inhibits CCR8 expression by upregulating AMP-activated protein kinase (AMPK)-activated sirtuin 2 (SIRT2). Metformin enhances the effectiveness of anti-PD-1 immunotherapy by reducing CCR8 expression on tumor-infiltrating Treg cells, suggesting that metformin has an antitumor effect by alleviating immunosuppression and promoting T cell-mediated immune response.

Control of CCR5 Cell-Surface Targeting by the PRAF2 Gatekeeper.

The cell-surface targeting of neo-synthesized G protein-coupled receptors (GPCRs) involves the recruitment of receptors into COPII vesicles budding at endoplasmic reticulum exit sites (ERESs). This process is regulated for some GPCRs by escort proteins, which facilitate their export, or by gatekeepers that retain the receptors in the ER. PRAF2, an ER-resident four trans- membrane domain protein with cytoplasmic extremities, operates as a gatekeeper for the GB1 protomer of the heterodimeric GABAB receptor, interacting with a tandem di-leucine/RXR retention motif in the carboxyterminal tail of GB1. PRAF2 was also reported to interact in a two-hybrid screen with a peptide corresponding to the carboxyterminal tail of the chemokine receptor CCR5 despite the absence of RXR motifs in its sequence. Using a bioluminescence resonance energy transfer (BRET)-based subcellular localization system, we found that PRAF2 inhibits, in a concentration-dependent manner, the plasma membrane export of CCR5. BRET-based proximity assays and Co-IP experiments demonstrated that PRAF2/CCR5 interaction does not require the presence of a receptor carboxyterminal tail and involves instead the transmembrane domains of both proteins. The mutation of the potential di-leucine/RXR motif contained in the third intracellular loop of CCR5 does not affect PRAF2-mediated retention. It instead impairs the cell-surface export of CCR5 by inhibiting CCR5's interaction with its private escort protein, CD4. PRAF2 and CD4 thus display opposite roles on the cell-surface export of CCR5, with PRAF2 inhibiting and CD4 promoting this process, likely operating at the level of CCR5 recruitment into COPII vesicles, which leave the ER.

T cell migration requires ion and water influx to regulate actin polymerization

Migration of T cells is essential for their ability to mount immune responses. Chemokine-induced T cell migration requires WNK1, a kinase that regulates ion influx into the cell. However, it is not known why ion entry is necessary for T cell movement. Here we show that signaling from the chemokine receptor CCR7 leads to activation of WNK1 and its downstream pathway at the leading edge of migrating CD4+ T cells, resulting in ion influx and water entry by osmosis. We propose that WNK1-induced water entry is required to swell the membrane at the leading edge, generating space into which actin filaments can polymerize, thereby facilitating forward movement of the cell. Given the broad expression of WNK1 pathway proteins, our study suggests that ion and water influx are likely to be essential for migration in many cell types, including leukocytes and metastatic tumor cells.

Increased gene expression of CCR6 and RORγt in peripheral blood cells of rheumatoid arthritis patients and their correlation with anti-cyclic citrullinated peptide and disease activity.

The significance of T helper 17 (Th17) cells in the pathogenesis of rheumatoid arthritis (RA) has recently been demonstrated in many studies. Retinoic acid receptor-related orphan receptor γt (RORγt) is a transcription factor that is specifically involved in the generation of Th17 cells. Besides, the chemokine receptor CCR6, the receptor for CCL20, is characteristically expressed by these cells. Considering the pivotal roles of Th17 cells in RA pathogenesis, in this study, we assessed the gene expression of CCR6 and RORγt in the peripheral blood leukocytes of new case RA patients. Also, we evaluated their association with anticyclic citrullinated peptide (anti-CCP) antibodies and disease activity. Forty-five new case RA patients and 45 healthy persons have been recruited in this investigation. The gene expression of CCR6 and RORγt was evaluated by quantitative real-time PCR (qRT-PCR), and anti-CCP antibodies plasma levels were measured using the enzyme-linked immunosorbent assay (ELISA) technique. Disease activity was measured according to the disease activity score-28 (DAS-28) formula. The gene expression of CCR6 and RORγt increased remarkably in new case RA patients compared to healthy controls (p < .05 and p < .01, respectively). Moreover, there was a positive correlation between RORγt gene expression and parameters, including gene expression of CCR6 (p = .001, r = .461), plasma levels of CCL20 (p = .0009, r = .477), ESR (p = .004, r = .419), DAS-28 (p = .006, r = .402), anti-CCP (p = .019, r = .346), and RF (p = .001, r = .451). Also, CCR6 gene expression was positively associated with the DAS-28 (p = .037, r = .310), plasma levels of anti-CCP (p = .037, r = .312), and ESR (p = .029, r = .327). Increased gene expression of CCR6 and RORγt in peripheral blood leukocytes of new case RA patients may contribute to the exacerbation and pathogenesis of RA.

Abstract A012: STING agonists drive intrinsic type I interferon responses in monocytes for optimal anti-tumor immunity

Abstract The cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway is triggered by the sensing of cytosolic DNA, triggering the production of type I interferon (IFN-I) and play a crucial role in host defense against pathogens. This pathway also induces an anti-tumor response when tumor-derived DNA is sensed. Small molecule agonists called STING agonists activate this pathway and have been shown to cause tumor regression in mice. However, it is unclear how immune cells respond to STING agonist-induced IFN-I. In our study, we observed that monocytes were abundantly recruited to tumors during STING agonist therapy, and the lack of CCR2+ Ly6Chi inflammatory monocytes in CCR2-knockout (KO) mice led to impaired responses to STING agonist therapy of B16F10 and MC-38 tumors. Single-cell RNA sequencing (scRNA-Seq) of CD45+ cells from lymph nodes and tumors of Ifnar1 mixed bone marrow chimeric mice in which half of the immune cells lacked IFN-I receptors revealed that inflammatory monocytes upregulated chemokine receptor ccr5 and genes associated with MHC-I restricted antigen presentation in response to IFN-I. Using mice with B16.OVA.Tomato red fluorescent tumors, we demonstrated that IFN-I-responsive monocytes captured fluorescent antigens in tumors and transported them to lymph nodes. Additionally, the administration of CCR5 antagonist, maraviroc, significantly reduced the number of fluorescent antigen-carrying monocytes in the lymph nodes of red fluorescent tumor-bearing mice treated with STING agonists, indicating the involvement of CCR5 in monocyte-mediated antigen transport. Furthermore, NicheNet analysis of scRNA-Seq data showed that IL-18 - IL-18R1 interaction was the top predicted interaction between inflammatory monocytes and CD8+ T cells or NK cells. Blocking IL-18 remarkedly reduced the therapeutic efficacy of STING agonist treatment. Moreover, IFN-I acted on monocytes to upregulate glucocorticoid-induced TNFR-related (GITRL) providing a pro-survival signal to T cells. Deletion of GITRL on CCR2+ monocytes led to impaired tumor control, and the absence of the cognate receptor GITR on T cells led to impaired anti-tumor effector T cell responses in the tumors treated with and tissue-resident memory T cell accumulation in the skins that rejected tumors with STING agonist therapy. Taken together, our data suggests that STING agonists induce IFN-I-responsive monocytes to promote anti-tumor responses through secreting IL-18, potentially through transporting antigens to lymph nodes, and through providing a pro-survival signal for T cell accumulation in the tumors during STING agonist therapy. Citation Format: Tianning Yu, Melanie Girard, Tania H Watts. STING agonists drive intrinsic type I interferon responses in monocytes for optimal anti-tumor immunity [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor Immunology and Immunotherapy; 2023 Oct 1-4; Toronto, Ontario, Canada. Philadelphia (PA): AACR; Cancer Immunol Res 2023;11(12 Suppl):Abstract nr A012.

IMMU-58. CHARACTERIZATION OF MYELOID CELL POPULATIONS IN PEDIATRIC HIGH-GRADE BRAIN TUMORS: THE MIMIC PROGRAM

Abstract BACKGROUND Pediatric high-grade brain tumors (pHGBT) pose treatment challenges with limited options. Myeloid cells, particularly tumor-associated macrophages (TAMs) in the tumor-microenvironment (TME), exhibit potent immunosuppressive features inhibiting effective anti-tumor T-cell responses. Targeting these cells holds promise to improve outcomes, however the underlying mechanisms of myeloid cell dysfunction remain poorly understood. This study aimed to comprehensively characterize myeloid cell populations in pHGBT and investigate their functional phenotype. METHODS Spectral flow cytometry was performed on tumor tissue (biopsies or resections) and tumor fragments obtained by cavitron ultrasonic surgical aspiration (CUSA) in pHGBT patients (High-grade glioma n=2, Ependymoma n=1, Medulloblastoma n=6, Pilocytic Astrocytoma n=2) enrolled in the MIMIC program. This allowed quantification and comprehensive characterization of myeloid cell populations within the TME. RESULTS The pHGBT TME showed a low abundance of immune cells across different entities, with myeloid cells comprising the predominant proportion. CD49d was used to identify invading cells derived from bone marrow (CD49+) and resident microglia (CD49-). The total TAMs/microglia population was detected in both tumor tissue and CUSA tumor fragments in similar proportions, however resident CD49d- microglia were notably increased in CUSA tumor fragments. Additionally, invading TAMs displayed a mixed "M1" and "M2" polarization phenotype and exhibited higher expression of the chemokine receptor CCR2 and HLA-DR, and of the immune-checkpoint receptors SIRP1A/B, CD33, and TIM3, compared to resident microglia. CONCLUSIONS TAMs play a multifaceted role in pHGBT. The high expression of immune-checkpoint receptors by invading TAMs suggests an immunosuppressive phenotype, potentially facilitating tumor growth, infiltration and (immune)therapy escape. Although, differences between disease entities could not yet be analyzed, disparities were observed in the TME between tumor and CUSA samples, likely related to spatial cellular organization. Understanding TAM dynamics and functional differences between invading and resident subsets, as well as their underlying mechanisms, is crucial for advancing therapeutic efficacy in pHGBT.

Cutting Edge: CCR8 Signaling Regulates IL-25- and IL-33-Responsive Skin Group 2 Innate Lymphoid Cell Migration and Function.

Group 2 innate lymphoid cells (ILC2s) are sentinels of barrier immunity, and their activation by the epithelial alarmins IL-25 and IL-33 is a defining trait. In this study, we identified a role for the chemokine receptor CCR8 in modulating skin ILC2 abundance and activation. CCR8 signaling facilitated IL-25-induced increases in skin and lung ILC2s, ILC2 activation and systemic IL-13 production, and ligand-directed ILC2 entry into skin and lung. CCR8 controlled ILC2 tissue entry in IL-25-treated naive mice, but only transferred bone marrow ILC2 progenitors were equipped to enter the skin, whereas multiple tissue-sourced ILC2s entered the lung. CCR8 selectively regulated IL-33-induced increases in skin ILC2s, their proliferation, and production of IL-13/IL-5, as well as IL-33-responsive transferred ILC2 trafficking only to the skin. Collectively, we illuminate (to our knowledge) novel aspects of CCR8 signaling-regulated ILC2 motility and function, especially in the skin, in response to two hallmark ILC2-activating alarmins.

Assessment of Circulating CCR6 Level in Acute Myocardial Infarction and its Association with Disease Severity.

Acute myocardial infarction (AMI) pathophysiology is mediated by systemic, intraplaque myocardial inflammatory processes that occur mainly due to coronary artery thrombosis in an atherosclerotic plaque area. The G-protein-coupled chemokine receptor (Ccr6) is displayed on the surface of many types of leukocytes, that have been found in atherosclerotic plaques. It is a novel mediator of inflammation and immune response. To determine CCR6 lymphocyte expression in AMI patients and its association with disease severity using the Gensini scoring system. 25 AMI patients and 25 controls underwent flow cytometry to determine the percentage of circulating CCR6+ lymphocytes. To forecast AMI and determine how CCR6 expression relates to it, multivariate logistic regression analysis was used. There was a higher percentage of CCR6+ lymphocyte expression in AMI patients than in controls. In addition, CCR6 showed a significant positive correlation with the Gensini score (GS) in the AMI group then with the degree of coronary artery disease (CAD). The chemokine receptor CCR6 is an independent biomarker for AMI and mayplay a role as a mediator of T lymphocyte recruitment, which is associated with coronary lesion destabilization.

Cytoplasmic CCR7 (CCR7c) Immunoexpression Is Associated with Tumor Invasion in Gastric Cancer

Background: This study investigates the CCR7 chemokine receptor’s prognostic value in gastric cancer and its relationship to metastasis.&#x0D; Materials and Methods: Normal and adjacent tumor cells in 70 patients with gastric cancer were evaluated for CCR7 expression using immunohistochemical staining. The prognostic values of high and low levels of expression of CCR7 were also evaluated by multivariate and univariate analyses.&#x0D; Results: Analysis indicated high expression of CCR7 in 52.9% of tumor tissue. Moreover, high expression of CCR7 was significantly related to metastasis of lymph nodes (p = 0.00). In addition, high expression of CCR7 had a positive correlation to the disease stage (p = 0.00), age of ≥50 years (p = 0.019), male gender (p = 0.024), vascular involvement (p = 0.009), histology of tumor adenocarcinoma (p = 0.00), and poor tumor differentiation (p = 0.00). However, the high expression of the CCR7 marker was not related to the tumor size.&#x0D; Conclusion: Based on our results, CCR7 expression in gastric cancer can be considered a clinical prognostic indicator in patients with gastric cancer.

Structural basis of dimerization of chemokine receptors CCR5 and CXCR4

G protein-coupled receptors (GPCRs) are prominent drug targets responsible for extracellular-to-intracellular signal transduction. GPCRs can form functional dimers that have been poorly characterized so far. Here, we show the dimerization mechanism of the chemokine receptors CCR5 and CXCR4 by means of an advanced free-energy technique named coarse-grained metadynamics. Our results reproduce binding events between the GPCRs occurring in the minute timescale, revealing a symmetric and an asymmetric dimeric structure for each of the three investigated systems, CCR5/CCR5, CXCR4/CXCR4, and CCR5/CXCR4. The transmembrane helices TM4-TM5 and TM6-TM7 are the preferred binding interfaces for CCR5 and CXCR4, respectively. The identified dimeric states differ in the access to the binding sites of the ligand and G protein, indicating that dimerization may represent a fine allosteric mechanism to regulate receptor activity. Our study offers structural basis for the design of ligands able to modulate the formation of CCR5 and CXCR4 dimers and in turn their activity, with therapeutic potential against HIV, cancer, and immune-inflammatory diseases.

Bifunctional Role of Monocyte Subsets in Modulating Radiotherapy Combined Intra-Tumor αCD40 Agonist Induced Abscopal Effect

Abscopal effect induced by radiotherapy and immune checkpoint blockade is a promising yet far from satisfactory strategy in clinical. The underlying immune mechanism, especially driven by monocytes remains poorly undefined. Monocytes consist of two phenotypically and functionally distinct subsets distinguished by expression of chemokine receptors CCR2 and CX3CR1: classical inflammatory Ly6ChiCCR2hi monocytes and nonclassical patrolling Ly6CloCCR2loCX3CR1hi monocytes. Monocytes differentiate and transit to other myeloid cells such as dendritic cells and macrophages according to various environmental cues. Herein we investigated the roles of monocyte subsets in modulating tumor control consisting of combination RT and myeloid checkpoint agonist αCD40 to specifically ignite myeloid cell activation. To establish abscopal model, contralateral tumors were implanted in each mouse, while only one side were treated with RT (8 Gy × 3) + αCD40 agonist (50 μg, intra-tumor). Tumor volume and mice survival were compared in each group (control, RT, αCD40 and RT + αCD40). Ccr2RFP/+ Cx3cr1GFP/+ (R2 × 3), Ccr2RFP/RFPCx3cr1+/+ (R2-KO) and Ccr2+/+Cx3cr1GFP/GFP (X3-KO) mice were used for cell tracking and to dissect chemokine receptor CCR2 and CX3CR1 on monocyte. Tumor infiltrating immune cells were analyzed by flowcytometry and RNA-seq. RT combined with αCD40 significantly dampened tumor growth on both ipsilateral and contralateral sides in abscopal model (p< 0.01), accompanied by upregulation of chemokine receptors CCR2 and CX3CR1 on myeloid cells were both increased in tumor and peripheral blood. Chemokine ligands CCL2, CCL3, CCL5, CCL7, CCL12 and CX3CL1 were upregulated in tumor after RT and αCD40 treatment, recruiting CCR2 and CX3CR1 expressing monocytes in situ. To elucidate the roles of CCR2 and CX3CR1 in mediating local and systemic anti-tumor immunity, R2 × 3, R2-KO and X3-KO mice with combined treatment were used. Tumor size on ipsilateral leg were similar among groups. However, tumor growth was significantly delayed on contralateral side in X3-KO mice while accelerated in R2-KO mice compared with that in R2 × 3 mice. Mechanistically, remarkable decrease of antigen presenting dendritic cells (MHCII+Ly6ChiCD11c+) were observed in R2-KO mice. Moreover, phagocytosis was strengthened in macrophages (F4/80+CD11b+) of X3-KO mice. CX3CR1 deletion ignite anti-tumor immunity elicited by RT and αCD40 through enhanced phagocytosis in macrophages, while CCR2 deletion renders inferior tumor control through reduction of dendritic cells. Preferential targeting nonclassical patrolling monocyte may lead to enhanced local and systemic tumor control.

Targeting Monocyte Derived CCL17 Attenuates Murine Crescentic Glomerulonephritis by Affecting Renal CCR4+ Regulatory T-Cell Recruitment

Introduction: The chemokine receptor CCR4 is expressed by diverse CD4⁺ T cell subsets including regulatory T cells (Tregs) but its functional importance for leukocyte recruitment and the relevance of its two corresponding chemokines CCL17 and CCL22 have not been studied in immune-mediated crescentic glomerulonephritis (cGN). Methods: Utilizing the single-cell RNA sequencing (scRNAseq) data in analyzing leukocytes isolated from both human and murine nephritic kidneys, we identified CCL17 as a potential therapeutic target in immune-mediated renal disease. Using a mouse model of murine cGN, we then delineated the effects of targeting CCL17 by neutralizing antibodies and in Ccl17 gene-deficient mice. Results: Unsupervised scRNAseq analyses identified the CCL17-CCR4 axis as a mechanism potentially involved in renal T-cell migration. Analyses of functional kidney impairment and histopathological kidney damage revealed an attenuation of crescentic GN in anti-CCL17 antibody-treated mice which was corroborated using in Ccl17 gene-deficient mice. Immunohistochemical analyses revealed that these changes were accompanied by an affected renal Treg recruitment in both experimental approaches. Conclusion: The chemokine receptor CCR4 and its corresponding chemokine CCL17 are expressed in human and murine cGN and targeting the CCR4-CCL17 axis by neutralizing antibodies as well as Ccl17 gene deficiency led to increased renal Treg recruitment and reduced histological and functional kidney damage in murine cGN.

SARS-CoV-2 spike-specific regulatory T cells (Treg) expand and develop memory in vaccine recipients suggesting a role for immune regulation in preventing severe symptoms in COVID-19

We enrolled healthy subjects that received 2 to 4 injections of mRNA-based vaccination to prevent COVID-19 months to a year from the last vaccine boost, and we found numerous SARS-CoV-2 spike-specific regulatory T cell (Treg) that developed T cell memory as effector memory T cells (TEM) and central memory T cells (TCM). CD4+ CD25high Treg expressed the chemokine receptor CCR6 in a considerable percentage, suggesting T cell homing to the vascular endothelium, lung and gut epithelial cells and brain. Treg phenotype was different than peripherally-induced Treg (pTreg) that revert from pro-inflammatory T cells under repeated stimulatory conditions, suggesting that SARS-CoV-2 spike-specific Treg differentiated from naïve T cells in tissues where the SARS-CoV-2 spike proteins were synthetized. Twenty two of 22 subjects studied responded to vaccination developing a spike-specific CD4+ T helper (Th)1 response, and 20 of 22 developing a spike-specific CD8+ cytotoxic T cells (CTL) response. However, in vaccine recipients the expansion of spike-specific pro-inflammatory T cells was less significant than the expansion of spike-specific Treg. Effector (TEM) and central memory (TCM) Treg were numerous as early as after two vaccine doses, with no significant differences following additional vaccine boosts. In co-culture experiments under stimulatory conditions, Treg regulated naïve T cell differentiation toward a pro-inflammatory phenotype and suppressed interferon (IFN)γ production by SARS-CoV-2-specific CD4 + Th1 cells.