The role of CC chemokine receptor 5 (CCR5) in islet allograft rejection

Role of chemokine receptors in transplant rejection and graft-versus-host disease

Organ transplantation increases life expectancy and improves the quality of life of patients experiencing specific conditions such as terminal organ failure. Despite matching efforts between donor and recipient, immune activation can interfere with allograft survival after transplantation if immunosuppression is not used. With both innate and adaptive responses, this is a complicated immunological process. This can lead to organ rejection, or graft-versus-host disease (GVHD), depending on the origin of the immune response. Inflammatory factors, such as chemokine receptors and their ligands, are involved in a wide variety of immunological processes, including modulating transplant rejection or GVHD, therefore, chemokine biology has been a major focus of transplantation studies. These molecules attract circulating peripheral leukocytes to infiltrate into the allograft and facilitate dendritic and T cell trafficking between lymph nodes and the graft during the allogeneic response. In this chapter, we will review the most relevant chemokine receptors such as CXCR3 and CCR5, among others, and their ligands involved in the process of allograft rejection for solid organ transplantation and graft-versus-host disease in the context of hematopoietic cell transplantation.

Antibody-Suppressor CXCR5+CD8+ T Cells Are More Potent Regulators of Humoral Alloimmunity after Kidney Transplant in Mice Compared to CD4+ Regulatory T Cells

Adoptive cell therapy (ACT), especially with CD4+ regulatory T cells (CD4+ Tregs), is an emerging therapeutic strategy to minimize immunosuppression and promote long-term allograft acceptance, although much research remains to realize its potential. In this study, we investigated the potency of novel Ab-suppressor CXCR5+CD8+ T cells (CD8+ TAb-supp) in comparison with conventional CD25highFoxp3+CD4+ Tregs for suppression of humoral alloimmunity in a murine kidney transplant (KTx) model of Ab-mediated rejection (AMR). We examined quantity of peripheral blood, splenic and graft-infiltrating CD8+ TAb-supp, and CD4+ Tregs in KTx recipients and found that high alloantibody-producing CCR5 knockout KTx recipients have significantly fewer post-transplant peripheral blood and splenic CD8+ TAb-supp, as well as fewer splenic and graft-infiltrating CD4+ Tregs compared with wild-type KTx recipients. ACT with alloprimed CXCR5+CD8+ T cells reduced alloantibody titer, splenic alloprimed germinal center (GC) B cell quantity, and improved AMR histology in CCR5 knockout KTx recipients. ACT with alloprimed CD4+ Treg cells improved AMR histology without significantly inhibiting alloantibody production or the quantity of splenic alloprimed GC B cells. Studies with TCR transgenic mice confirmed Ag specificity of CD8+ TAb-supp-mediated effector function. In wild-type recipients, CD8 depletion significantly increased alloantibody titer, GC B cells, and severity of AMR pathology compared with isotype-treated controls. Anti-CD25 mAb treatment also resulted in increased but less pronounced effect on alloantibody titer, quantity of GC B cells, and AMR pathology than CD8 depletion. To our knowledge, this is the first report that CD8+ TAb-supp cells are more potent regulators of humoral alloimmunity than CD4+ Treg cells.

A functional interaction between the CCR5 and CD34 molecules expressed in hematopoietic cells can support (or even promote) the development of cancer

Inflammation and angiogenesis are linked to the development of cancer since both can support the establishment of a tumor-prone microenvironment. The CCR5 is a major regulatory molecule involved in inflammation. The CD34 molecule is commonly described as a hematopoietic stem cell marker, and CD34⁺ cells are involved in the regulation of distinct physiological processes, including angiogenesis. CCR5 participates in the development of various types of cancer, and recently, a reduced CCR5 expression was associated with low CD34⁺ cell counts in human cord blood. A naturally occurring genetic variant of the CCR5 gene, the so-called CCR5Δ32 polymorphism, consists of a 32 base-pair deletion in the DNA, interfering in the CCR5 protein levels on the cell surface. When in homozygosis, this variant leads to a total absence of CCR5 expression on the cell surface. In heterozygous individuals, CCR5 surface levels are reduced. Based on these key findings, we hypothesize that a functional interaction can connect CCR5 and CD34 molecules (giving rise to a “CCR5-CD34 axis”). According to this, a CCR5-CD34 interaction can potentially support the development of different types of cancer. Consequently, the lack of CCR5 in association with reduced CD34⁺ cell counts could indicate a protective factor against the development of cancer. It is required to characterize in detail the functional relationship between CCR5 and CD34 proteins, as well as the real influence of both molecules on the susceptibility and development of cancer at population level. If our hypothesis is confirmed, the CCR5-CD34 axis may be a potential target in the development of anti-cancer therapies.

Increased Adipose Tissue Expression of Interferon Regulatory Factor (IRF)-5 in Obesity: Association with Metabolic Inflammation

Interferon regulatory factor (IRF)-5 is known to be involved in M1 macrophage polarization, however, changes in the adipose expression of IRF5 in obesity and their relationship with the local expression of proinflammatory cytokines/chemokines are unknown. Therefore, IRF5 gene expression was determined in the subcutaneous adipose tissue samples from 53 non-diabetic individuals (6 lean, 18 overweight, and 29 obese), using real-time RT-PCR. IRF5 protein expression was also assessed using immunohistochemistry and/or confocal microscopy. Adipose gene expression of signature immune metabolic markers was also determined and compared with adipose IRF5 gene expression. Systemic levels of C-reactive protein and adiponectin were measured by ELISA. The data show that adipose IRF5 gene (P = 0.008) and protein (P = 0.004) expression was upregulated in obese compared with lean individuals. IRF5 expression changes correlated positively with body mass index (BMI; r = 0.37/P = 0.008) and body fat percentage (r = 0.51/P = 0.0004). In obese, IRF5 changes associated positively with HbA1c (r = 0.41/P = 0.02). A good agreement was found between gene and protein expression of IRF5 in obese subjects (r = 0.65/P = 0.001). IRF5 gene expression associated positively with adipose inflammatory signatures including local expression of TNF-α, IL-6, CXCL8, CCL-2/5, IL-1β, IL-18, CXCL-9/10, CCL7, CCR-1/2/5, TLR-2/7/8/9, IRF3, MyD88, IRAK-1, and inflammatory macrophage markers (P < 0.05). Interestingly, IRF5 gene expression correlated positively with CRP (r = 0.37, P = 0.03) and negatively with adiponectin levels (r = −0.43, P = 0.009). In conclusion, elevated adipose IRF5 expression in obesity concurs with the typical inflammatory signatures, locally and systemically. Hence, the IRF5 upregulation may represent a novel adipose tissue marker for metabolic inflammation.

Peritransplant VLA-4 blockade inhibits endogenous memory CD8 T cell infiltration into high-risk cardiac allografts and CTLA-4Ig resistant rejection

Recipient endogenous memory CD8 T cells expressing reactivity to donor class I MHC infiltrate MHC-mismatched cardiac allografts within 24 hours after reperfusion and express effector functions mediating graft injury. The current study tested the efficacy of Very Late Antigen-4 (VLA-4) blockade to inhibit endogenous memory CD8 T cell infiltration into cardiac allografts and attenuate early posttransplant inflammation. Peritransplant anti-VLA-4 mAb given to C57BL6 (H-2b ) recipients of AJ (H-2a ) heart allografts completely inhibited endogenous memory CD4 and CD8 T cell infiltration with significant decrease in macrophage, but not neutrophil, infiltration into allografts subjected to either minimal or prolonged cold ischemic storage (CIS) prior to transplant, reduced intra-allograft IFN-γ-induced gene expression and prolonged survival of allografts subjected to prolonged CIS in CTLA-4Ig treated recipients. Anti-VLA-4 mAb also inhibited priming of donor-specific T cells producing IFN-γ until at least day 7 posttransplant. Peritransplant anti-VLA plus anti-CD154 mAb treatment similarly prolonged survival of allografts subjected to minimal or increased CIS prior to transplant. Overall, these data indicate that peritransplant anti-VLA-4 mAb inhibits early infiltration memory CD8 T cell infiltration into allografts with a marked reduction in early graft inflammation suggesting an effective strategy to attenuate negative effects of heterologous alloimmunity in recipients of higher risk grafts.

Surgical perspectives regarding application of biomaterials for the management of large congenital diaphragmatic hernia defects

This review focuses on the surgical viewpoints on patch repairs in neonates with large congenital diaphragmatic hernia defects. The main focus  is on the various biomaterials that have been employed to date with regard to their source of origins, degradation properties as well as tissue integration characteristics. Further focus  is on the present knowledge on patch integration when biomaterials are placed in the diaphragmatic defect. The review will also look at the present evidence on the biomechanical characteristics of the most commonly used biomaterials and compares these materials to diaphragmatic tissue to offer more  insight on the present practice of patch repairs in large defects. Since tissue engineering and regenerative medicine has offered another dimension to diaphragmatic replacement, a detailed overview of this technology will be undertaken with regard to cell sourcing, scaffolds, in vitro versus in vivo implants as well as quality of tissue produced, to explore the limitations and the feasibility facing the scientific community in its clinical implementation of skeletal muscle-engineered tissue beyond laboratory research for diaphragmatic replacement.

Comparison of Tolerated and Rejected Islet Grafts: A Gene Expression Study

Recently we showed that donor-specific tolerance to MHC-matched islet allografts in diabetic NOD mice could be induced by simultaneous islet and bone marrow transplantation. Mononuclear cell infiltration surrounding the islets was also found in tolerated grafts. In this study, we compared gene expression in the tolerated and rejected islet grafts by using Affymetrix Murine U74A oligonucleotide arrays. To confirm the results of microarray analysis, we performed real-time PCR and RNase protection assay on selected genes. Of over 12,000 genes studied, 57 genes were expressed at consistently higher levels in tolerated islet grafts, and 524 genes in rejected islet grafts. Genes from a variety of functional clusters were found to be different between rejected and tolerated grafts. In the rejected islet grafts, a number of T-cell surface markers and of cytotoxicity-related genes were highly expressed. Also in the rejected grafts, a number of cytokines and chemokines and their receptors were highly expressed. The differential expression of selected genes found by microarray analysis was also confirmed by real-time PCR and RNase protection assay. Our results indicated that gene microarray analysis can help us to detect gene expression differences representative of the biologic mechanisms of tolerance and rejection.

Chemokines and Their Receptors in Islet Allograft Rejection and as Targets for Tolerance Induction

Graft rejection is a major barrier to successful outcome of transplantation surgery. Islet transplantation introduces insulin secreting tissue into type 1 diabetes mellitus recipients, relieving patients from exogenous insulin injection. However, insulitis of grafted tissue and allograft rejection prevent long-term insulin independence. Leukocyte trafficking is necessary for the launch of successful immune responses to pathogen or allograft. Chemokines, small chemotactic cytokines, direct the migration of leukocytes through their interaction with chemokine receptors found on cell surfaces of immune cells. Unique receptor expression of leukocytes, and the specificity of chemokine secretion during various states of immune response, suggest that the extracellular chemokine milieu specifically homes certain leukocyte subsets. Thus, only those leukocytes required for the current immune task are attracted to the inflammatory site. Chemokine blockade, using antagonists and monoclonal antibodies directed against chemokine receptors, is an emerging and specific immunosuppressive strategy. Importantly, chemokine blockade may potentiate tolerance induction regimens to be used following transplantation surgery, and prevent the need for life-long immunosuppression of islet transplant recipients. Here, the role for chemokine blockade in islet transplant rejection and tolerance is reviewed.

Defective CD8 Signaling Pathways Delay Rejection in Older Recipients

CD8+ T cells play a cardinal feature in response to alloantigens and are able to generate effector/memory T cells independently from CD4+ T cells. To investigate the impact of aging on CD8 T cells, we used a fully mismatched mouse skin transplant model. Our findings showed a prolonged allograft survival in older recipients associated with a significant increase of CD4+ and CD8+ CD44high CD62Llow effector/memory T cells and a reduced systemic IFNγ production. When reconstituting young CBA Rag-1 mice that lack mature T and B cells with old CD8+ T cells expressing clonal anti-H2K T cell receptor (TCR) alloreactive for MHC I, graft survival was significantly prolonged and comparable to those receiving young CD8+ T cells. Moreover, our data showed that reduced systemic IFNγ levels observed in old recipients had been linked to a compromised expression of the IL-2R β subunit (CD122) by old CD8+ T cells. In addition, we observed an impaired IFNγ production on IL-2 receptor activation. At the same time, gene profiling analysis of old CD8 T cells demonstrated reduced chemokine ligand-3 and CD40L expression that resulted in compromised CD8+ T cell/dendritic cell communication, leading to impaired migratory and phagocytic activity of CD11c cells.Collectively, our study demonstrated that aging delays allograft rejection. CD8 T cells play a critical role in this process linked to a compromised production of IFNγ, in addition to a defective IL-2 receptor signaling machinery and a defective communication between CD8 T cells and dendritic cells.

IL-1 Receptor Signaling on Graft Parenchymal Cells Regulates Memory and De Novo Donor-Reactive CD8 T Cell Responses to Cardiac Allografts

Reperfusion of organ allografts induces a potent inflammatory response that directs rapid memory T cell, neutrophil, and macrophage graft infiltration and their activation to express functions mediating graft tissue injury. The role of cardiac allograft IL-1 receptor (IL-1R) signaling in this early inflammation and the downstream primary alloimmune response was investigated. When compared with complete MHC-mismatched wild-type cardiac allografts, IL-1R(-/-) allografts had marked decreases in endogenous memory CD8 T cell and neutrophil infiltration and expression of proinflammatory mediators at early times after transplant, whereas endogenous memory CD4 T cell and macrophage infiltration was not decreased. IL-1R(-/-) allograft recipients also had marked decreases in de novo donor-reactive CD8, but not CD4, T cell development to IFN-γ-producing cells. CD8 T cell-mediated rejection of IL-1R(-/-) cardiac allografts took 3 wk longer than wild-type allografts. Cardiac allografts from reciprocal bone marrow reconstituted IL-1R(-/-)/wild-type chimeric donors indicated that IL-1R signaling on graft nonhematopoietic-derived, but not bone marrow-derived, cells is required for the potent donor-reactive memory and primary CD8 T cell alloimmune responses observed in response to wild-type allografts. These studies implicate IL-1R-mediated signals by allograft parenchymal cells in generating the stimuli-provoking development and elicitation of optimal alloimmune responses to the grafts.

Characterization of Innate Immunity in an Extended Whole Blood Model of Human Islet Allotransplantation

The instant blood-mediated inflammatory reaction (IBMIR) has been studied in whole blood models of human allo-islet transplantation for short periods (<6 h). Beyond this time frame the innate response to intraportally transplanted islets is less well described. A novel whole blood model was applied to study blood-islet-graft interactions up to 48 h. Heparinized polyvinyl chloride tubing was sealed into small bags containing venous blood together with allogeneic human islets and exocrine tissue, respectively. The bags were attached to a rotating wheel (37°C). Concentrated glucose and sodium hydrogen carbonate were added every 12 h to maintain physiological limits for sustained immune cell functions. Plasma was collected at repeated time points for analyses of coagulation/complement activation and chemokine/cytokine production. Immune cell infiltration was analyzed using immunohistochemistry. Coagulation and platelet activation markers, thrombin-antithrombin complex (TAT) and soluble CD40 ligand (sCD40L) showed early high concentrations (at 6-12 h). sC5b-9 steadily increased over 48 h. At 6 h neutrophils and monocytes surrounded the clotted cellular grafts with a following massive infiltration of neutrophils. High and increasing concentrations of CXCR1/2 ligands [IL-8 and growth-regulated oncogene α/β/γ (Gro-α/β/γ)] and IL-6 were produced in response to human islets and exocrine tissue. The CCR2 ligand monocyte chemoattractant protein 1 (MCP-1) exhibited increasing concentrations in response to exocrine tissue. The CXCR3 ligand interferon-inducible T cell α chemoattractant (I-TAC) was produced in response to both human islets and exocrine tissue from 6 h. Monokine induced by γ interferon (Mig) and interferon γ-induced protein 10 (IP-10) showed a later response, preferentially to exocrine tissue and with larger variations among preparations. An extended blood model of clinical islet transplantation allowed characterization of early immune activation in response to human islets and exocrine tissue. Increased production of chemokines targeting CXCR1/2, CCR2, and CXCR3 was observed, accompanied by massive intraislet neutrophil infiltration over 48 h. The model proved to be useful in exploring early blood-mediated reactions to cellular transplants and has relevance for evaluation of pharmacological interventions to prevent graft loss.

Control of CD8 T-Cell Infiltration into Tumors by Vasculature and Microenvironment

CD8 T-cells are a critical brake on the initial development of tumors. In established tumors, the presence of CD8 T-cells is correlated with a positive patient prognosis, although immunosuppressive mechanisms limit their effectiveness and they are rarely curative without manipulation. Cancer immunotherapies aim to shift the balance back to dominant antitumor immunity through antibody blockade of immunosuppressive signaling pathways, vaccination, and adoptive transfer of activated or engineered T-cells. These approaches have yielded striking responses in small subsets of patients with solid tumors, most notably those with melanoma. Importantly, the subset of patients who respond to vaccination or immunosuppression blockade therapies are those with CD8 T-cells present in the tumor prior to initiating therapy. While current adoptive cell therapy approaches can be dramatically effective, they require infusion of extremely large numbers of T-cells, but the number that actually infiltrates the tumor is very small. Thus, poor representation of CD8 T-cells in tumors is a fundamental hurdle to successful immunotherapy, over and above the well-established barrier of immunosuppression. In this review, we discuss the factors that determine whether immune cells are present in tumors, with a focus on the representation of cytotoxic CD8 T-cells. We emphasize the critically important role of tumor-associated vasculature as a gateway that enables the active infiltration of both effector and naïve CD8 T-cells that exert antitumor activity. We also discuss strategies to enhance the gateway function and extend the effectiveness of immunotherapies to a broader set of cancer patients.

Long-term survival of allograft murine islets coated via covalently stabilized polymers

Clinical islet transplantation (CIT) has emerged as a promising treatment option for type 1 diabetes mellitus (T1DM); however, the antirejection drug regimen necessary to mitigate allograft islet rejection is undesirable. The use of polymeric coatings to immunocamouflage the transplant from host immune attack has great potential. Alginate and poly(ethylene glycol) (PEG)-based polymers, functionalized with azide and phosphine, respectively, which form spontaneous and chemoselective crosslinks via the bioorthogonal Staudinger ligation scheme, were recently developed. Here, the utility of these polymers to form immunoprotective, ultrathin coatings on murine primary pancreatic islets is explored. Resulting coatings are nontoxic, with unimpaired glucose stimulated insulin secretion. Transplantation of coated BALB/c (H-2(d) ) islets into streptozotozin-induced diabetic C57BL/6 (H-2(b) ) results in prompt achievement of normoglycemia, at a rate comparable to controls. A significant subset of animals receiving coated islets (57%) exhibits long-term (>100 d) function, with robust islets observed upon explantation. Control islets rejected after 15 d (±9 d). Results illustrate the capacity of chemoselectively functionalized polymers to form coatings on islets, imparting no detrimental effect to the underlying cells, with resulting coatings exhibiting significant protective effects in an allograft murine model.

Effector mechanisms of rejection

Organ transplantation appears today to be the best alternative to replace the loss of vital organs induced by various diseases. Transplants can, however, also be rejected by the recipient. In this review, we provide an overview of the mechanisms and the cells/molecules involved in acute and chronic rejections. T cells and B cells mainly control the antigen-specific rejection and act either as effector, regulatory, or memory cells. On the other hand, nonspecific cells such as endothelial cells, NK cells, macrophages, or polymorphonuclear cells are also crucial actors of transplant rejection. Last, beyond cells, the high contribution of antibodies, chemokines, and complement molecules in graft rejection is discussed in this article. The understanding of the different components involved in graft rejection is essential as some of them are used in the clinic as biomarkers to detect and quantify the level of rejection.

Characterization in vitro and in vivo of a pandemic H1N1 influenza virus from a fatal case

Pandemic 2009 H1N1 (pH1N1) influenza viruses caused mild symptoms in most infected patients. However, a greater rate of severe disease was observed in healthy young adults and children without co-morbid conditions. Here we tested whether influenza strains displaying differential virulence could be present among circulating pH1N1 viruses. The biological properties and the genotype of viruses isolated from a patient showing mild disease (M) or from a fatal case (F), both without known co-morbid conditions were compared in vitro and in vivo. The F virus presented faster growth kinetics and stronger induction of cytokines than M virus in human alveolar lung epithelial cells. In the murine model in vivo, the F virus showed a stronger morbidity and mortality than M virus. Remarkably, a higher proportion of mice presenting infectious virus in the hearts, was found in F virus-infected animals. Altogether, the data indicate that strains of pH1N1 virus with enhanced pathogenicity circulated during the 2009 pandemic. In addition, examination of chemokine receptor 5 (CCR5) genotype, recently reported as involved in severe influenza virus disease, revealed that the F virus-infected patient was homozygous for the deleted form of CCR5 receptor (CCR5Δ32).

Immunosuppressive Activity of Size-Controlled PEG-PLGA Nanoparticles Containing Encapsulated Cyclosporine A

We encapsulated cyclosporine A (CsA) in poly(ethylene glycol)-b-poly(d,l-lactide-co-glycolide) (PEG-PLGA) nanoparticles (NPs) by nanoprecipitation of CsA and PEG-PLGA. The resulting CsA/PEG-PLGA-NPs were <100 nm in diameter with a narrow particle size distribution. The NP size could be controlled by tuning the polymer concentration, solvent, or water/solvent ratio during formulation. The PEGylated NPs maintained non-aggregated in salt solution. Solid NPs lyoprotected with bovine serum albumin were prepared for the convenience of storage and transportation. The release kinetics of CsA (55.6% released on Day 1) showed potential for maintaining therapeutic CsA concentrations in vivo. In T-cell assays, both free CsA and CsA/PEG-PLGA-NPs suppressed T-cell proliferation and production of inflammatory cytokines dose dependently. In a mixed lymphocyte reaction assay, the IC(50) values for free CsA and CsA/PEG-PLGA-NPs were found to be 30 and 35 ng/mL, respectively. This nanoparticulate CsA delivery technology constitutes a strong basis for future targeted delivery of immunosuppressive drugs with improved efficiency and potentially reduced toxicity.

CCR5Δ32 genotype leads to a Th2 type directed immune response in ESRD patients

Background

In patients with end stage renal disease (ESRD) we observed protection from inflammation-associated mortality in CCR5Δ32 carriers, leading to CCR5 deficiency, suggesting impact of CCR5Δ32 on inflammatory processes. Animal studies have shown that CCR5 deficiency is associated with a more pronounced Th2 type immune response, suggesting that in human CCR5Δ32 carriers the immune response may be more Th2 type directed. So, in the present study we determined the Th1-Th2 type directed immune response in ESRD patients carrying and not carrying the CCR5Δ32 genetic variant after stimulation.

Methodology/Principal Findings

We tested this hypothesis by determining the levels of IFN-γ and IL-4 and the distribution of Th1, Th2 and Th17 directed circulating CD4+ and CD8+ T cells and regulatory T cells (Tregs) after stimulation in ESRD patients with (n = 10) and without (n = 9) the CCR5Δ32 genotype. The extracellular levels of IFN-γ and IL-4 did not differ between CCR5Δ32 carriers and non carriers. However, based on their intracellular cytokine profile the percentages IL-4 secreting CD4+ and CD8+ T cells carrying the CCR5Δ32 genotype were significantly increased (p = 0.02, respectively p = 0.02) compared to non carriers, indicating a more Th2 type directed response. Based on their intracellular cytokine profile the percentages IFN-γ and IL-17 secreting T cells did not differ between carriers and non-carriers nor did the percentage Tregs, indicating that the Th1, Th17 and T regulatory response was not affected by the CCR5Δ32 genotype.

Conclusions/Significance

This first, functional human study shows a more pronounced Th2 type immune response in CCR5Δ32 carriers compared to non carriers. These differences may be involved in the previously observed protection from inflammation-associated mortality in ESRD patients carrying CCR5Δ32.

CCR5 blockade is well tolerated and induces changes in the tissue distribution of CCR5+ and CD25+ T cells in healthy, SIV-uninfected rhesus macaques

BACKGROUND

CCR5 is a main co-receptor for HIV, but also homes lymphocytes to sites of inflammation. We hypothesized that inhibition of CCR5 signaling would reduce HIV-associated chronic immune activation.

METHODS

To test this hypothesis, we administered an antagonistic anti-CCR5 monoclonal antibody (HGS101) to five uninfected rhesus macaques (RMs) and monitored lymphocyte dynamics in blood and tissue.

RESULTS

CCR5 blockade resulted in decreased levels of CCR5+ T cells in blood and, at later timepoints, in lymph nodes. Additionally, the levels of CD25+ T cells increased in lymph nodes, but decreased in blood, bone marrow, and rectal mucosa. Finally, a profile of gene expression from HGS101-treated RMs revealed a subtle, but consistent, in vivo signature of CCR5 blockade that suggests a mild immune-modulatory effect.

CONCLUSIONS

Treatment with anti-CCR5 antibody induces changes in the tissue distribution of CCR5+ and CD25+ T cells that may impact on the overall levels of immune activation during HIV and SIV infection.

Identification and characterization of INCB9471, an allosteric noncompetitive small-molecule antagonist of C-C chemokine receptor 5 with potent inhibitory activity against monocyte migration and HIV-1 infection

C-C chemokine receptor 5 (CCR5) is a clinically proven target for inhibition of HIV-1 infection and a potential target for various inflammatory diseases. In this article, we describe 5-[(4-{(3S)-4-[(1R,2R)-2-ethoxy-5-(trifluoromethyl)-2,3-dihydro-1H-inden-1-yl]-3-methylpiperazin-1-yl}-4-methylpiperidin-1-yl)carbonyl]-4,6-dimethylpyrimidine dihydrochloride (INCB9471), a potent and specific inhibitor of human CCR5 that has been proven to be safe and efficacious in viral load reduction in phase I and II human clinical trails. INCB9471 was identified using a primary human monocyte-based radioligand competition binding assay. It potently inhibited macrophage inflammatory protein-1β-induced monocyte migration and infection of peripheral blood mononuclear cells by a panel of R5-HIV-1 strains. The results from binding and signaling studies using incremental amounts of INCB9471 demonstrated INCB9471 as a noncompetitive CCR5 inhibitor. The CCR5 residues that are essential for interaction with INCB9471 were identified by site-specific mutagenesis studies. INCB9471 rapidly associates with but slowly dissociates from CCR5. When INCB9471 was compared with three CCR5 antagonists that had been tested in clinical trials, the potency of INCB9471 in blocking CCR5 ligand binding was similar to those of 4,6-dimethyl-5-{[4-methyl-4-((3S)-3-methyl-4-{(1R0-2-(methyloxy)-1-[4-(trifluoromethyl) phenyl]ethyl}-1-piperazingyl)-1-piperidinyl]carbonyl}pyrimidine (SCH-D; vicriviroc), 4-{[4-({(3R)-1-butyl-3-[(R)-cyclohexyl(hydroxyl)methyl]-2, 5-dioxo-1,4,9-triazaspiro[5.5]undec-9-yl}methyl)phenyl]oxy}benzoic acid hydrochloride (873140; aplaviroc), and 4,4-difluoro-N-((1S)-3-{(3-endo)-3-[3-methyl-5-(1-methylethyl)-4H-1,2,4-triazol-4-yl]-8-azabicyclo[3.2.1]oct-8-yl}-1-phenylpropyl)cyclohexanecarboxamide (UK427857; maraviroc). Its inhibitory activity against CCR5-mediated Ca(2+) mobilization was also similar to those of SCH-D and 873140. Further analysis suggested that INCB9471 and UK427857 may have different binding sites on CCR5. The significance of two CCR5 antagonists with different binding sites is discussed in the context of potentially overcoming drug-resistant HIV-1 strains.

CC Chemokine receptor 5 deficiency does not prevent local immune responses to adenovirus vector in islet transplant recipients

BACKGROUND

CC chemokine receptor 5 (CCR5) plays an important role in mediating inflammation. We examined the effect of CCR5 on the immune response to adenovirus vectors and graft function in islet transplant model.

MATERIALS AND METHODS

Syngeneic wild-type (WT) or CCR5-deficient (KO) mouse islets transduced with adenovirus encoding β-gal were transplanted under the renal capsule. After transplant, blood glucose, glucose tolerance, graft cellular infiltration, transgene and chemokine/receptor expression, and systemic anti-adenoviral/-β-gal immune response were evaluated.

RESULTS

Diabetes was reversed in 1 d in both WT and KO untransduced recipients, while islets transduced with adenovirus failed to reverse diabetes until 10 d post-transplant in WT recipients or even longer (>15 d) in KO recipients (P < 0.05). A profound infiltration of CD4(+), CD8(+) cells and macrophages was observed in both WT and KO transduced grafts at 25 d. Though transgene expression was significantly reduced, insulin and β-gal expression persisted over 3 mo. Glucose tolerance was impaired in all grafts in KO recipients compared with untransduced grafts in WT recipients at 25 d post-transplant, but was equivalent at 3 mo. Early expression of CCR2 mRNA was increased in transduced grafts in both WT and KO recipients. No systemic antivector immunity was demonstrated in any recipient group.

CONCLUSIONS

Transduction of islets with adenovirus causes significant local inflammation in islet grafts and impairs early graft function in CCR5-deficient recipients, but long-term graft function is preserved. Thus, CCR5 absence does not prevent the local immune response to adenovirus transduction, and vector-associated graft dysfunction is not mediated by CCR5.

Targeting the CXCR4-CXCL12 axis mobilizes autologous hematopoietic stem cells and prolongs islet allograft survival via programmed death ligand 1

Antagonism of CXCR4 disrupts the interaction between the CXCR4 receptor on hematopoietic stem cells (HSCs) and the CXCL12 expressed by stromal cells in the bone marrow, which subsequently results in the shedding of HSCs to the periphery. Because of their profound immunomodulatory effects, HSCs have emerged as a promising therapeutic strategy for autoimmune disorders. We sought to investigate the immunomodulatory role of mobilized autologous HSCs, via target of the CXCR4-CXL12 axis, to promote engraftment of islet cell transplantation. Islets from BALB/c mice were transplanted beneath the kidney capsule of hyperglycemic C57BL/6 mice, and treatment of recipients with CXCR4 antagonist resulted in mobilization of HSCs and in prolongation of islet graft survival. Addition of rapamycin to anti-CXCR4 therapy further promoted HSC mobilization and islet allograft survival, inducing a robust and transferable host hyporesponsiveness, while administration of an ACK2 (anti-CD117) mAb halted CXCR4 antagonist-mediated HSC release and restored allograft rejection. Mobilized HSCs were shown to express high levels of the negative costimulatory molecule programmed death ligand 1 (PD-L1), and HSCs extracted from wild-type mice, but not from PD-L1 knockout mice, suppressed the in vitro alloimmune response. Moreover, HSC mobilization in PD-L1 knockout mice failed to prolong islet allograft survival. Targeting the CXCR4-CXCL12 axis thus mobilizes autologous HSCs and promotes long-term survival of islet allografts via a PD-L1-mediated mechanism.

Polylactide-cyclosporin A nanoparticles for targeted immunosuppression

Polymeric nanoparticles (NPs), prepared via coprecipitation of drugs and polymers, are promising drug delivery vehicles for treating diseases with improved efficacy and reduced toxicity. Here, we report an unprecedented strategy for preparing polylactide-cyclosporine A (PLA-CsA) NPs (termed CsA-NPs) through CsA-initiated ring-opening polymerization of lactide (LA) followed by nanoprecipitation. The resulting CsA-NPs have sub-100 nm sizes and narrow particle size distributions, and release CsA in a sustained manner without a "burst"-release effect. Both free CsA and CsA-NPs displayed comparable suppression of T-cell proliferation and production of inflammatory cytokines in various T-cell assays in a dose-dependent manner. The IC(50) values for CsA and CsA-NPs were 27.5 and 72.0 ng/ml, respectively. As lymph nodes are the main loci for T-cell activation, we coupled dendritic cells (DCs) with CsA-NPs and successfully delivered CsA selectively to the lymph nodes. Our studies indicated that CsA-NPs could be internalized in the DCs with a sustained release of CsA to the culture medium, suppressing alloreactive T-cell proliferation. Allogeneic DCs loaded with CsA-NPs were able to migrate to the draining lymph nodes where the T-cell priming was significantly reduced without any systemic release. This innovative nanoparticulate CsA delivery technology constitutes a strong basis for future targeted delivery of immunosuppressive drugs with improved efficiency and reduced toxicity.

Dual targeting of CCR2 and CCR5: therapeutic potential for immunologic and cardiovascular diseases

A cardinal feature of inflammation is the tissue recruitment of leukocytes, a process that is mediated predominantly by chemokines via their receptors on migrating cells. CCR2 and CCR5, two CC chemokine receptors, are important players in the trafficking of monocytes/macrophages and in the functions of other cell types relevant to disease pathogenesis. This review provides a brief overview of the biological actions of CCR2 and CCR5 and a comprehensive summary of published data that demonstrate the involvement of both receptors in the pathogenesis of immunologic diseases (RA, CD, and transplant rejection) and cardiovascular diseases (atherosclerosis and AIH). In light of the potential for functional redundancy of chemokine receptors in mediating leukocyte trafficking and the consequent concern over insufficient efficacy offered by pharmacologically inhibiting one receptor, this review presents evidence supporting dual targeting of CCR2 and CCR5 as a more efficacious strategy than targeting either receptor alone. It also examines potential safety issues associated with such dual targeting.

Monokine induced by interferon-gamma (MIG/CXCL9) is derived from both donor and recipient sources during rejection of class II major histocompatibility complex disparate skin allografts

Chemokines, including monokine induced by interferon-gamma (Mig/CXCL9), are produced both in allografts and during the direct T-cell infiltration that mediates graft rejection. Neither the specific production nor contribution of allograft donor versus recipient Mig in allograft rejection is currently known. C57BL/6 mice with a targeted deletion in the Mig gene were used as both skin allograft donors and recipients in a class II major histocompatibility complex-mismatched graft model to test the requirement for donor- versus recipient-derived Mig for acute rejection. B6.Mig(-/-) allografts had a 10-day prolonged survival in B6.H-2(bm12) recipients when compared with wild-type C57BL/6 allograft donors, and B6.H-2(bm12) skin allografts had a 5-day prolonged survival in B6.Mig(-/-) versus wild-type recipients. Transplantation of B6.Mig(-/-) skin grafts onto B6.H-2(bm12).Mig(-/-) recipients resulted in further prolonged allograft survival with more than 30% of the grafts surviving longer than 60 days. Prolonged allograft survival was also associated with delayed cellular infiltration into grafts but not with altered T-cell proliferative responses to donor stimulators. Immunohistochemical staining of allograft sections indicated that Mig is produced by both donor- and recipient-derived sources, but Mig from each of these sources appeared in different areas of the allograft tissue. These results therefore demonstrate the synergy of donor- and recipient-derived Mig in promoting T-cell infiltration into allografts.

The role of inflammation in insulitis and beta-cell loss in type 1 diabetes

Type 1 diabetes mellitus (T1DM) is a chronic autoimmune disease with a strong inflammatory component. The latest studies indicate that innate immunity and inflammatory mediators have a much broader role in T1DM than initially assumed. Inflammation might contribute to early induction and amplification of the immune assault against pancreatic beta cells and, at later stages, to the stabilization and maintenance of insulitis. Inflammatory mediators probably contribute to the suppression of beta-cell function and subsequent apoptosis; they may also inhibit or stimulate beta-cell regeneration and might cause peripheral insulin resistance. The different effects of inflammation take place in different phases of the course of T1DM, and should be considered in the context of a 'dialog' between invading immune cells and the target beta cells. This dialog is mediated both by cytokines and chemokines that are released by beta cells and immune cells, and by putative, immunogenic signals that are delivered by dying beta cells. In this Review, we divided the role of inflammation in T1DM into three arbitrary stages: induction, amplification and maintenance or resolution of insulitis. These stages, and their progression or resolution, might depend on a patient's genetic background, which contributes to disease heterogeneity.

Chemokine Receptor-5Delta32 Mutation is No Risk Factor for Ischemic-Type Biliary Lesion in Liver Transplantation

It has been shown that certain chemokine receptor polymorphisms may correspond to certain complications after organ transplantation. Ischemic-type biliary lesion (ITBL) encounters for major morbidity and mortality in liver transplant recipients. So far, the exact cause for ITBL remains unclear. Certain risk factors for the development of ITBL like donor age and cold ischemic time are well described. In a previous study, a 32-nucleotide deletion of the chemokine receptor-5Δ32 (CCR-5Δ32) was strongly associated with the incidence of ITBL in adult liver transplantation. This study re-evaluates the association of CCR-5Δ32 gene polymorphism and the incidence of ITBL. 169 patients were included into this retrospective analysis. 134 patients were homozygous for wild-type CCR-5, 33 patients heterozygous, and 2 patients were homozygous for CCR-5Δ32 mutation. There were no major differences in donor or recipients demographics. No association was found between CCR-5Δ32 mutation and the development of ITBL. We conclude that CCR-5Δ32 is no risk factor for the development of ITBL in our patient cohort.

Innate immunity and heat shock response in islet transplantation

Islet transplantation is an extremely effective therapy for patients with type I diabetes, providing tight control of blood glucose and persistent insulin release. Islet grafts struggle with various stress responses and immunity attacks, which contribute to loss of islet grafts in the long term. In this review we focus upon the innate immunity and heat shock responses, which are closely relevant to the outcome of islet grafts. Potential strategies provided by more comprehensive interventions to control innate immunity and by selective induction of heat shock proteins may ameliorate the outcome of islet transplantation.

CCR5 expression levels influence NFAT translocation, IL-2 production, and subsequent signaling events during T lymphocyte activation

Ligands of CCR5, the major coreceptor of HIV-1, costimulate T lymphocyte activation. However, the full impact of CCR5 expression on T cell responses remains unknown. Here, we show that compared with CCR5(+/+), T cells from CCR5(-/-) mice secrete lower amounts of IL-2, and a similar phenotype is observed in humans who lack CCR5 expression (CCR5-Delta32/Delta32 homozygotes) as well as after Ab-mediated blockade of CCR5 in human T cells genetically intact for CCR5 expression. Conversely, overexpression of CCR5 in human T cells results in enhanced IL-2 production. CCR5 surface levels correlate positively with IL-2 protein and mRNA abundance, suggesting that CCR5 affects IL-2 gene regulation. Signaling via CCR5 resulted in NFAT transactivation in T cells that was blocked by Abs against CCR5 agonists, suggesting a link between CCR5 and downstream pathways that influence IL-2 expression. Furthermore, murine T cells lacking CCR5 had reduced levels of intranuclear NFAT following activation. Accordingly, CCR5 expression also promoted IL-2-dependent events, including CD25 expression, STAT5 phosphorylation, and T cell proliferation. We therefore suggest that by influencing a NFAT-mediated pathway that regulates IL-2 production and IL-2-dependent events, CCR5 may play a critical role in T cell responses. In accord with our prior inferences from genetic-epidemiologic studies, such CCR5-dependent responses might constitute a viral entry-independent mechanism by which CCR5 may influence HIV-AIDS pathogenesis.

Chemokines and transplant vasculopathy

Transplant vasculopathy (TV) remains the leading cause of late death among heart transplant recipients. Transplant vasculopathy is characterized by progressive neointimal proliferation, leading to ischemic failure of the allograft. Multiple experimental and clinical studies have shown that injury to the graft at various stages of transplantation can be a risk factor for development of transplant vasculopathy. The hallmark of cardiac allograft injury is the infiltration of leukocytes. Recruitment of leukocytes requires intercellular communication between infiltrating cells, endothelium, parenchymal cells, and components of extracellular matrix. These events are mediated via the generation of adhesion molecules, cytokines, and chemokines. The chemokines, by virtue of their specific cell receptor expression, can selectively mediate the local recruitment/activation of distinct leukocytes/cells, allowing for migration across the endothelium and beyond the vascular compartment. This report provides a comprehensive review of the chemokines that participate in the development of transplant vasculopathy.

The role for monocyte chemoattractant protein-1 in the generation and function of memory CD8+ T cells

Memory T cells are resistant to the conventional costimulatory blockade and therefore impede tolerance induction. However, their migratory, survival, and functional requirements for chemokines are not well understood. We herein examine the role for MCP-1 or CCL2 in the generation, migration, and function of memory CD8+ T cells. We found that overall generation of both central memory (TCM) and effector memory (TEM) CD8+ T cells was severely impaired in the absence of MCP-1. Importantly, the survival of TEM, but not TCM, CD8+ cells was reduced without MCP-1, whereas the homeostatic proliferation of TCM, but not TEM, CD8+ cells was weakened in MCP-1-/- mice. However, once they were generated in the absence of MCP-1, in vitro function of both subsets of memory cells remained intact as determined by their proliferation and IFN-gamma production. Interestingly, the migration of TCM, but not TEM, CD8+ cells to inflammatory sites was significantly delayed without MCP-1, whereas both subsets of memory cells underwent comparable expansion and apoptosis with or without MCP-1 during the effector phase. Moreover, the function to eliminate a graft of TCM, but not TEM, CD8+ cells was impaired without MCP-1. Thus, this study demonstrates that MCP-1 plays an important role in not only migration but also generation and survival of memory T cells. This finding provides new insight into the requirement of chemokines for the generation, survival, and function of differential subsets of memory T cells and may have clinic implications for tolerance induction.

Phenotypic and functional differences between wild-type and CCR2-/- dendritic cells: implications for islet transplantation

BACKGROUND

Trafficking of dendritic cells (DC), the primary regulators of alloimmune responses, is controlled by chemokines. Here, we provide evidence that lack of CCR2 could lead to the generation of functionally and phenotypically different DC, which in part could explain the benefits observed in transplanting islets in CCR2 recipients.

METHODS AND RESULTS

We show that, in contrast to the in vitro DC maturation model, in vivo DC maturation is accompanied by an increase in the expression of CCR2. Compared with wild-type (WT), DC generated in vitro from CCR2 mice, and DC extracted from CCR2 naïve mice or from CCR2 recipients of islet allografts, display lesser allostimulatory capacity. Compared with WT DC, CCR2 DC produce more IL-4 and induce more IL-4-producing T cells. CCR2 DC also promote the generation of regulatory T cells that more efficiently suppress T cell proliferative responses by mixed leukocyte reaction. Similarly, the percentage of CD4CD25FoxP3 cells were found to be higher in CCR2 recipients of islet allografts than in WT recipients.

CONCLUSIONS

In summary, lack of CCR2 interferes with the allostimulatory capacity of DC and promotes the generation of regulatory T cells. This is the first demonstration of a mechanistic link between targeting a specific chemokine pathway and the DC-regulatory T cell axis in alloimmunity.

Combined CXCR3/CCR5 blockade attenuates acute and chronic rejection

Chemokine-chemokine receptor interactions orchestrate mononuclear cells recruitment to the allograft, leading to acute and chronic rejection. Despite biologic redundancy, several experimental studies have demonstrated the importance of CXCR3 and CCR5 in acute rejection of allografts. In these studies, deficiency or blockade of CXCR3 or CCR5 led to prolongation of allograft survival, yet allografts were ultimately lost to acute rejection. Given the above findings and the specificity of mononuclear cells bearing CXCR3 and CCR5, we hypothesized that combined blockade of CXCR3 and CCR5 will lead to indefinite (>100 days) graft survival in a full MHC-mismatched murine cardiac allograft model. The donor hearts in the control group were rejected in 6 +/- 1 days after transplantation. Combined blockade of CXCR3 and CCR5 prolonged allograft survival >15-fold vs the control group; all allografts survived for >100 days. More importantly, the donor hearts did not display any intimal lesions characteristic of chronic rejection. Further analysis of the donor hearts in the CXCR3/CCR5 blockade group demonstrated graft infiltration with CD4(+)CD25(+) T cells expressing the Foxp3 gene. Depletion of CD25(+) cells in the combined CXCR3 and CCR5 blockade group resulted in acute rejection of the allografts in 22 +/- 2 days. Combined CXCR3 and CCR5 blockade also reduced alloantigen-specific T lymphocyte proliferation. Combined CXCR3 and CCR5 blockade is effective in preventing acute and chronic rejection in a robust murine model. This effect is mediated, in part, by CD25(+) regulatory T cell recruitment and control of T lymphocyte proliferation.

Relation of circulating concentrations of chemokine receptor CCR5 ligands to C-peptide, proinsulin and HbA1c and disease progression in type 1 diabetes

Th1 related chemokines CCL3 and CCL5 and Th2 related CCL4 as ligands of the receptor CCR5 contribute to disease development in animal models of type 1 diabetes. In humans, no data are available addressing the role of these chemokines regarding disease progression and remission. We investigated longitudinally circulating concentrations of CCR5 ligands of 256 newly diagnosed patients with type 1 diabetes. CCR5 ligands were differentially associated with beta-cell function and clinical remission. CCL5 was decreased in remitters and positively associated with HbA1c suggestive of a Th1 associated progression of the disease. Likewise, CCL3 was negatively related to C-peptide and positively associated with the beta-cell stress marker proinsulin but increased in remitters. CCL4 associated with decreased beta-cell stress shown by negative association with proinsulin. Blockage of chemokines or antagonism of CCR5 by therapeutic agents such as maraviroc may provide a new therapeutic target to ameliorate disease progression in type 1 diabetes.

Chemokines and their receptors: drug targets in immunity and inflammation

The chemokine system coordinates leukocyte migration in immunity and inflammation and is implicated in the pathogenesis of many human diseases. Although several successful strategies have been identified to develop drugs targeting chemokines and their receptors, this has not yet resulted in many new therapeutics. This is likely due to a complexity of the chemokine system, which was not initially appreciated, that is characterized by redundancy, pleiotropy, and differences among species. Nevertheless, our understanding of chemokine biology is continuing to grow and several promising drugs are currently being tested in late-stage clinical trials. In this review, we examine the role of chemokines in health and diseases and discuss strategies to target the chemokine system.

Acute humoral rejection of renal allografts in CCR5(-/-) recipients

Increasing detection of acute humoral rejection (AHR) of renal allografts has generated the need for appropriate animal models to investigate underlying mechanisms. Murine recipients lacking the chemokine receptor CCR5 reject cardiac allografts with marked C3d deposition in the parenchymal capillaries and high serum donor-reactive antibody titers, features consistent with AHR. The rejection of MHC-mismatched renal allografts from A/J (H-2(a)) donors by B6.CCR5(-/-) (H-2(b)) recipients was investigated. A/J renal allografts survived longer than 100 days in wild-type C57BL/6 recipients with normal blood creatinine levels (28 +/- 7 micromol/L). All CCR5(-/-) recipients rejected renal allografts within 21 days posttransplant (mean 13.3 +/- 4 days) with elevated creatinine (90 +/- 31 micromol/L). The rejected allografts had neutrophil and macrophage margination and diffuse C3d deposition in peritubular capillaries, interstitial hemorrhage and edema, and glomerular fibrin deposition. Circulating donor-reactive antibody titers were 40-fold higher in B6.CCR5(-/-) versus wild-type recipients. Depletion of recipient CD8 T cells did not circumvent rejection of the renal allografts by CCR5-deficient recipients. In contrast, microMT(-/-)/CCR5(-/-) recipients, incapable of producing antibody, did not reject most renal allografts. Collectively, these results indicate the rapid rejection of renal allografts in CCR5(-/-) recipients with many histopathologic features observed during AHR of human renal allografts.

Antibody-Mediated Rejection of Cardiac Allografts in CCR5-Deficient Recipients

Rejected MHC-mismatched cardiac allografts in CCR5(-/-) recipients have low T cell infiltration, but intense deposition of C3d in the large vessels and capillaries of the graft, characteristics of Ab-mediated rejection. The roles of donor-specific Ab and CD4 and CD8 T cell responses in the rejection of complete MHC-mismatched heart grafts by CCR5(-/-) recipients were directly investigated. Wild-type C57BL/6 and B6.CCR5(-/-) (H-2(b)) recipients of A/J (H-2(a)) cardiac allografts had equivalent numbers of donor-reactive CD4 T cells producing IFN-gamma, whereas CD4 T cells producing IL-4 were increased in CCR5(-/-) recipients. Numbers of donor-reactive CD8 T cells producing IFN-gamma were reduced 60% in CCR5(-/-) recipients. Day 8 posttransplant serum titers of donor-specific Ab were 15- to 25-fold higher in CCR5(-/-) allograft recipients, and transfer of this serum provoked cardiac allograft rejection in RAG-1(-/-) recipients within 14 days, whereas transfer of either serum from wild-type recipients or immune serum from CCR5-deficient recipients diluted to titers observed in wild-type recipients did not mediate this rejection. Wild-type C57BL/6 and B6.CCR5(-/-) recipients rejected A/J cardiac grafts by day 11, whereas rejection was delayed (day 12-60, mean 21 days) in muMT(-/-)/CCR5(-/-) recipients. These results indicate that the donor-specific Ab produced in CCR5(-/-) heart allograft recipients is sufficient to directly mediate graft rejection, and the absence of recipient CCR5 expression has differential effects on the priming of alloreactive CD4 and CD8 T cells.

Beta 3 integrins regulate lymphocyte migration and cytokine responses in heart transplant rejection

Integrin alpha v beta 3 is important for cell survival, signaling and migration, particularly during angiogenesis and tumorigenesis, where it has been proposed as a therapeutic target. alpha v beta 3 is up-regulated following transplantation and beta 3 polymorphisms are associated with increased acute kidney rejection, suggesting that alpha v beta 3 may also play a role in transplant rejection. Here, using a model of allogeneic heart transplantation, we show that allograft survival is prolonged in beta 3 integrin-deficient (beta 3(-/-)) mice. This is associated with Th2-type immune responses and reduced T-cell infiltration into grafts and T cells from beta 3(-/-) mice show impaired adhesion and migration, consistent with a role for alpha v beta 3 in transmigration. These studies provide evidence that targeting beta 3 integrins impairs recruitment of effector cells and alters cytokine production, so prolonging graft survival. We also show that low doses of blocking antibodies against leukocyte function associated antigen-1 (LFA-1)/alpha L beta 2 and very late antigen-4 (VLA-4)/alpha 4 beta 1, when combined with deletion of beta 3, lead to long-term survival of allografts with no evidence of chronic rejection. Hence we provide strong mechanistic evidence supporting previous genetic studies, demonstrate the involvement of beta 3 integrins in both acute and chronic rejection and identify beta 3 as a new target for immunosuppressive therapy.

Characterization of donor dendritic cells and enhancement of dendritic cell efflux with CC-chemokine ligand 21: a novel strategy to prolong islet allograft survival

Dendritic cells (DCs) are the most potent antigen-presenting cells, yet little data are available on the differential characteristics of donor and recipient DCs (dDCs and rDCs, respectively) during the process of islet allograft rejection. DTR-GFP-DC mice provide a novel tool to monitor DC trafficking and characteristics during allograft rejection. We show rapid migration of dDCs to recipient lymphoid tissues as early as 3 h post-islet allotransplantation. Compared with rDCs, dDCs express different patterns of chemokine receptors, display differential proliferative capacity, and exhibit a higher level of maturity; these findings could be attributed to the effects of injury that dDCs undergo during islet cell preparation and engraftment. Intriguingly, we detected dDCs in the spleen of recipients long after rejection of islet allografts. Given that dDCs express high levels of CCR7, islets were cultured before transplant with the ligand for CCR7 (CCL21). This novel method, which enabled us to enhance the efflux of dDCs from islet preparations, resulted in a prolongation of islet allograft survival in immunocompetent recipients. This study introduces dDCs and rDCs as two distinct types of DCs and provides novel data with clinical implications to use chemokine-based DC-depleting strategies to prolong islet allograft survival.

CCL4 protects from type 1 diabetes by altering islet beta-cell-targeted inflammatory responses

We previously reported that interleukin (IL)-4 treatment of nonobese diabetic (NOD) mice elevates intrapancreatic CCL4 expression and protects from type 1 diabetes. Here, we show that antibody neutralization of CCL4 abrogates the ability of T-cells from IL-4-treated NOD mice to transfer protection against type 1 diabetes. Intradermal delivery of CCL4 via a plasmid vector stabilized by incorporation of the Epstein-Barr virus EBNA1/oriP episomal maintenance replicon (pHERO8100-CCL4) to NOD mice beginning at later stages of disease progression protects against type 1 diabetes. This protection was associated with a Th2-like response in the spleen and pancreas; decreased recruitment of activated CD8(+) T-cells to islets, accompanied by diminished CCR5 expression on CD8(+) T-cells; and regulatory T-cell activity in the draining pancreatic lymph nodes. Thus, inflammatory responses that target islet beta-cells are suppressed by CCL4, which implicates the use of CCL4 therapeutically to prevent type 1 diabetes.

Membrane-bound CC chemokine inhibitor 35K provides localized inhibition of CC chemokine activity in vitro and in vivo

CC chemokines mediate mononuclear cell recruitment and activation in chronic inflammation. We have shown previously that gene transfer using recombinant adenoviruses, encoding a soluble CC chemokine-binding protein of vaccinia virus 35K, can dramatically reduce atherosclerosis and vein graft remodeling in apolipoprotein E knockout mice. In this study, we report the development of a membrane-bound form of 35K (m35K), tagged with GFP, which allows for localized, broad-spectrum CC chemokine blockade. In vitro experiments indicate that m35K-expressing cells no longer undergo CC chemokine-induced chemotaxis, and m35K-expressing cells can locally deplete the CC chemokines RANTES (CCL5) and MIP-1alpha (CCL3) from supernatant medium. This sequestration of CC chemokines can prevent chemotaxis of bystander cells to CC, but not CX(3)C chemokines. Intraperitoneal injection of mice with an adenovirus-encoding m35K leads to a significant (44%) decrease in leukocyte recruitment into the peritoneal cavity in a sterile peritonitis model. Intravenous adenovirus-encoding m35K delivery leads to m35K expression in hepatocytes, which confers significant protection against liver damage (75% reduction in liver enzymes) in a Con A-induced hepatitis model. In summary, we have generated a membrane-bound CC chemokine-binding protein (m35K) that provides localized broad-spectrum CC chemokine inhibition in vitro and in vivo. m35K may be a useful tool to study the role of CC chemokines in leukocyte trafficking and block the recruitment of monocytes in chronic inflammation.

Alloantigen-enhanced accumulation of CCR5+ 'effector' regulatory T cells in the gravid uterus

Regulatory T cells play an essential role in preventing fetal rejection by the maternal immune system. Here we show that, based on the expression of CCR5, regulatory T cells can be divided into a highly suppressive CCR5+ and a far less suppressive CCR5- subpopulation, suggesting that the former represent the effector arm of regulatory T cells. Although regulatory T cells from CCR5-/- gene deletion mutants still suppress, they are less effective mediators of maternal-fetal tolerance. The accumulation of CCR5+ regulatory T cells at this site appears to be enhanced by alloantigen. This finding is in stark contrast to the systemic expansion of regulatory T cells during pregnancy, which appears to be alloantigen-independent. The fact that CCR5+ regulatory T cells preferentially accumulate in the gravid uterus and that expression of CCR5 on regulatory T cells can be induced by activation lead us to propose that CCR5 is responsible for the accumulation of those regulatory T cells that have been activated by paternal antigens.

IL-12p40 is not required for islet allograft rejection

AIM

To investigate whether IL-12p40 plays a crucial role in regulating islet allograft rejection in a streptozotocin (STZ)-induced diabetes mouse model.

METHODS

C57BL/6 and IL-12p40 gene knockout mice were selected as recipient mice, to which the diabetes was induced with a treatment of STZ (150-200 mg/kg) by a single ip injection. BALB/c mice were selected as donor mice and islet cells were isolated from the mice. The 500 islets were transplanted into recipient mice beneath the capsule of the left kidney. Following the islet transplantation the glucose from the mice sera was monitored and the rejection rate of islets was analyzed.

RESULTS

STZ could induce diabetes in the recipient mice within 1 week. After transplantation of allograft islets, the increased glucose in wild-type (WT) mice returned to normal level and was maintained for 10 d. Unexpectedly, the rejection rate of islet allograft between IL-12p40-deficient mice and WT mice was similar.

CONCLUSION

The results suggested that, although islet allograft rejection is believed to be Th1-cell predominant, the Th1 response inducer, IL-12 and IL-23 are not essential to induce islet allograft rejection.

Involvement of CCR5 signaling in macrophage recruitment to porcine islet xenografts

BACKGROUND

Porcine antigen primed and CD4+ T-cell-activated macrophages are capable of both recognition and rejection of porcine xenografts. However, the specific signaling mechanisms involved remains to be addressed. The aim of this study was to examine the role of chemokine receptor and CD40 signaling in macrophage recruitment and graft destruction.

METHODS

Macrophages were isolated from rejecting CCR2, CCR5, CD40 and control C57BL/6 mice that were recipients of neonatal porcine pancreatic cell cluster (NPCC) xenografts and were transferred to NPCC recipient NOD-SCID mice.

RESULTS

Macrophages isolated from rejecting NPCC xenografts in CD40 and wildtype C57BL/6 mice demonstrated upregulated expression of macrophage activation markers as well as CCR5 and CCR2 genes, and caused pig islet xenograft destruction 8 days after transfer to NOD-SCID recipients. Graft infiltrating macrophages from rejecting CCR2 mice showed a similar activation phenotype and destroyed NPCC xenografts 10 days after transfer to NOD-SCID mice. Blockade of MCP-1 by anti-MCP-1 mAb did not prolong graft survival in CD4+ T cell reconstituted NPCC recipient NOD-SCID mice. By contrast, the graft infiltrating macrophages from rejecting CCR5 recipients showed impaired macrophage activation when compared to control C57BL/6 recipients, and transfer of these macrophages did not result in xenograft destruction in NOD-SCID recipients until day 16 after transfer. Analysis of graft infiltrating macrophages from these rejecting NOD-SCID mice showed an impaired activation phenotype.

CONCLUSION

These results demonstrate that CCR5 is involved in both the activation and recruitment of macrophages to rejecting islet xenografts but other pathways are involved.