Activation of blood T lymphocytes down-regulates CXCR4 expression and interferes with propagation of X4 HIV strains

TCR-Engineered Lymphocytes Targeting NY-ESO-1: In Vitro Assessment of Cytotoxicity against Tumors

Adoptive T-cell therapies tailored for the treatment of solid tumors encounter intricate challenges, necessitating the meticulous selection of specific target antigens and the engineering of highly specific T-cell receptors (TCRs). This study delves into the cytotoxicity and functional characteristics of in vitro-cultured T-lymphocytes, equipped with a TCR designed to precisely target the cancer-testis antigen NY-ESO-1. Flow cytometry analysis unveiled a notable increase in the population of cells expressing activation markers upon encountering the NY-ESO-1-positive tumor cell line, SK-Mel-37. Employing the NanoString platform, immune transcriptome profiling revealed the upregulation of genes enriched in Gene Ontology Biological Processes associated with the IFN-γ signaling pathway, regulation of T-cell activation, and proliferation. Furthermore, the modified T cells exhibited robust cytotoxicity in an antigen-dependent manner, as confirmed by the LDH assay results. Multiplex immunoassays, including LEGENDplex™, additionally demonstrated the elevated production of cytotoxicity-associated cytokines driven by granzymes and soluble Fas ligand (sFasL). Our findings underscore the specific targeting potential of engineered TCR T cells against NY-ESO-1-positive tumors. Further comprehensive in vivo investigations are essential to thoroughly validate these results and effectively harness the intrinsic potential of genetically engineered T cells for combating cancer.

Mesenchymal Stromal Cells: a Possible Reservoir for HIV-1?

The introduction of antiretroviral therapy (ART) and highly active antiretroviral therapy (HAART) has transformed human immunodeficiency virus (HIV)-1 into a chronic, well-managed disease. However, these therapies do not eliminate all infected cells from the body despite suppressing viral load. Viral rebound is largely due to the presence of cellular reservoirs which support long-term persistence of HIV-1. A thorough understanding of the HIV-1 reservoir will facilitate the development of new strategies leading to its detection, reduction, and elimination, ultimately leading to curative therapies for HIV-1. Although immune cells derived from lymphoid and myeloid progenitors have been thoroughly studied as HIV-1 reservoirs, few studies have examined whether mesenchymal stromal/stem cells (MSCs) can assume this function. In this review, we evaluate published studies which have assessed whether MSCs contribute to the HIV-1 reservoir. MSCs have been found to express the receptors and co-receptors required for HIV-1 entry, albeit at levels of expression and receptor localisation that vary considerably between studies. Exposure to HIV-1 and HIV-1 proteins alters MSC properties in vitro, including their proliferation capacity and differentiation potential. However, in vitro and in vivo experiments investigating whether MSCs can become infected with and harbour latent integrated proviral DNA are lacking. In conclusion, MSCs appear to have the potential to contribute to the HIV-1 reservoir. However, further studies are needed using techniques such as those used to prove that cluster of differentiation (CD)4⁺ T cells constitute an HIV-1 reservoir before a reservoir function can definitively be ascribed to MSCs.

The CXCL12-CXCR4/CXCR7 axis as a mechanism of immune resistance in gastrointestinal malignancies

Single agent checkpoint inhibitor therapy has not been effective for most gastrointestinal solid tumors, but combination therapy with drugs targeting additional immunosuppressive pathways is being attempted. One such pathway, the CXCL12-CXCR4/CXCR7 chemokine axis, has attracted attention due to its effects on tumor cell survival and metastasis as well as immune cell migration. CXCL12 is a small protein that functions in normal hematopoietic stem cell homing in addition to repair of damaged tissue. Binding of CXCL12 to CXCR4 leads to activation of G protein signaling kinases such as P13K/mTOR and MEK/ERK while binding to CXCR7 leads to β-arrestin mediated signaling. While some gastric and colorectal carcinoma cells have been shown to make CXCL12, the primary source in pancreatic cancer and peritoneal metastases is cancer-associated fibroblasts. Binding of CXCL12 to CXCR4 and CXCR7 on tumor cells leads to anti-apoptotic signaling through Bcl-2 and survivin upregulation, as well as promotion of the epithelial-to-mesechymal transition through the Rho-ROCK pathway and alterations in cell adhesion molecules. High levels of CXCL12 seen in the bone marrow, liver, and spleen could partially explain why these are popular sites of metastases for many tumors. CXCL12 is a chemoattractant for lymphocytes at lower levels, but becomes chemorepellant at higher levels; it is unclear exactly what gradient exists in the tumor microenvironment and how this influences tumor-infiltrating lymphocytes. AMD3100 (Plerixafor or Mozobil) is a small molecule CXCR4 antagonist and is the most frequently used drug targeting the CXCL12-CXCR4/CXCR7 axis in clinical trials for gastrointestinal solid tumors currently. Other small molecules and monoclonal antibodies against CXCR4 are being trialed. Further understanding of the CXCL12- CXCR4/CXCR7 chemokine axis in the tumor microenvironment will allow more effective targeting of this pathway in combination immunotherapy.

Evaluation of resistance to HIV-1 infection ex vivo of PBMCs isolated from patients with chronic myeloid leukemia treated with different tyrosine kinase inhibitors

Current antiretroviral treatment (ART) may control HIV-1 replication but it cannot cure the infection due to the formation of a reservoir of latently infected cells. CD4+ T cell activation during HIV-1 infection eliminates the antiviral function of the restriction factor SAMHD1, allowing proviral integration and the reservoir establishment. The role of tyrosine kinases during T-cell activation is essential for these processes. Therefore, the inhibition of tyrosine kinases could control HIV-1 infection and restrict the formation of the reservoir. A family of tyrosine kinase inhibitors (TKIs) is successfully used in clinic for treating chronic myeloid leukemia (CML). The safety and efficacy against HIV-1 infection of five TKIs was assayed in PBMCs isolated from CML patients on prolonged treatment with these drugs that were infected ex vivo with HIV-1. We determined that the most potent and safe TKI against HIV-1 infection was dasatinib, which preserved SAMHD1 antiviral function and avoid T-cell activation through TCR engagement and homeostatic cytokines. Imatinib and nilotinib showed lower potency and bosutinib was quite toxic in vitro. Ponatinib presented similar profile to dasatinib but as it has been associated with higher incidence of arterial ischemic events, dasatinib would be the better choice of TKI to be used as adjuvant of ART in order to avoid the establishment and replenishment of HIV-1 reservoir and move forward towards an HIV cure.

Different performances of CXCR4, integrin-1β and CCR-2 in bone marrow stromal cells (BMSCs) migration by low-intensity pulsed ultrasound stimulation

Low-intensity pulsed ultrasound (LIPUS) is an established therapy for fracture healing where bone marrow stromal cells (BMSCs) migration is crucial to bone regeneration. This work focused on different performances of C-X-C-receptor 4 (CXCR4), integrin-1β and chemokine-chemokine receptor2 (CCR-2) in BMSCs migration by LIPUS stimulation. Single 20-min LIPUS treatment was applied to BMSCs during wound healing assay with or without the inhibitor AMD3100. The migration rate of BMSCs with LIPUS stimulation exhibited a higher closure rate than that of BMSCs without LIPUS stimulation, which was 1.89 μm/h and 1.38 μm/h, respectively. After LIPUS stimulation, significant elevation of the expression of CXCR4, integrin-1β and CCR-2 was observed. When AMD3100 was added, the migration rate of the BMSCs was obviously declined with or without LIPUS treatment. Furthermore, the expression of CXCR4 was significantly down-regulated by AMD3100, while integrin-1β and CCR-2 were less affected. It suggested that the enhancement of the migration of the BMSCs by LIPUS was inhibited by AMD3100. The results confirmed that LIPUS stimulation was able to activate and improve migration of BMSCs. Nevertheless, CXCR4 and both integrin-1β and CCR-2 had different roles in BMSCs migration after LIPUS treatment.

Immunophenotyping of rheumatoid arthritis reveals a linkage between HLA-DRB1 genotype, CXCR4 expression on memory CD4(+) T cells, and disease activity

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease that leads to destructive arthritis. Although the HLA class II locus is the strongest genetic risk factor for rheumatoid arthritis, the relationship between HLA class II alleles and lymphocyte activation remains unclear. We performed immunophenotyping of peripheral blood mononuclear cells on 91 HLA-DRB1-genotyped RA patients and 110 healthy donors. The frequency of memory CXCR4⁺CD4⁺ T cells, and not Th1 and Th17 cells, was significantly associated with disease severity by multiple linear regression analysis. RA patients with one or more susceptible HLA-DR haplotypes (shared epitope: SE) displayed a significantly higher frequency of memory CXCR4⁺CD4⁺ T cells. Moreover, the frequency of memory CXCR4⁺CD4⁺ T cells significantly correlated with the expression level of HLA-DR on B cells, which was elevated in RA patients with SE. In vitro analysis and transcriptomic pathway analysis suggested that the interaction between HLA-DR and T cell receptors is an important regulator of memory CXCR4⁺CD4⁺ T cells. Clinically, a higher frequency of memory CXCR4⁺CD4⁺ T cells predicted a better response to CTLA4-Ig. Memory CXCR4⁺CD4⁺ T cells may serve as a powerful biomarker for unraveling the linkage between HLA-DRB1 genotype and disease activity in RA.

CXCR4 expression on pathogenic T cells facilitates their bone marrow infiltration in a mouse model of aplastic anemia

Aplastic anemia (AA) is a disease characterized by T-cell-mediated destruction of bone marrow (BM) hematopoietic stem and progenitor cells. Physiologically, T cells migrate to the BM in response to chemokines, such as SDF-1α, the ligand for CXCR4. However, how T cells traffic to the BM in AA is poorly understood. CXCR4 is aberrantly expressed in immune-mediated diseases and its regulation by nuclear factor-κB (NF-κB) in cancer models is well documented. In this study, we show that CXCR4 is highly expressed on BM-infiltrating CD4(+) and CD8(+) T cells in a mouse model of AA. Inhibiting CXCR4 in AA mice, using CXCR4(-/-) splenocytes or AMD3100, significantly reduced BM infiltration of T cells. We also report that NF-κB occupancy at the CXCR4 promoter is enhanced in BM-infiltrating CD8(+) T cells of AA mice. Moreover, inhibiting NF-κB signaling in AA mice using Bay11 or dehydroxymethylepoxyquinomicin, or transferring p50(-/-) splenocytes, decreased CXCR4 expression on CD8(+) T cells, significantly reduced BM infiltration of T cells, and strongly attenuated disease symptoms. Remarkably, therapeutic administration of Bay11 significantly extended survival of AA mice. Overall, we demonstrate that CXCR4 mediates migration of pathogenic T cells to the BM in AA mice, and inhibiting NF-κB signaling may represent a novel therapeutic approach to treating AA.

Mouse Dental Pulp Stem Cells Support Human Umbilical Cord Blood-Derived Hematopoietic Stem/Progenitor Cells in Vitro

It is well documented that specialized mesenchymal stem/stromal cells (MSCs) constitute the hematopoietic stem cell (HSC) niche in the bone marrow (BM), and these MSCs support/maintain the HSCs in an undifferentiated state. A number of studies have demonstrated that BM-derived MSCs (BM-MSCs) can support HSCs in vitro. However, it remains unclear whether nonhematopoietic tissue-derived MSC-like cells, such as dental pulp stem cells (DPSCs), have the ability to support HSCs. In this study, we prospectively isolated DPSCs from mouse mandibular incisors by fluorescence-activated cell sorting (FACS) using BM-MSC markers, such as PDGFRα and Sca-1. The PDGFRα and Sca-1 double-positive DPSCs and BM-MSCs showed similar morphologies and expression patterns of MSC markers. The ability of the DPSCs to support hematopoietic stem/progenitor cells (HSPCs) was then analyzed by an in vitro coculture system. Moreover, their HSC-supporting activity was evaluated by in vivo xenotransplantation assays using NOD/Shi-scid/IL-2Rγcnull (NOG) mice. Interestingly, the DPSCs supported human cord blood (CB)-derived CD34-positive (CD34+), as well as CD34-negative (CD34–), HSCs. The supporting activities of DPSCs for human CB-derived CD34+ and CD34– HSCs were comparable to those of BM-MSCs. The results of the present study demonstrated, for the first time, that prospectively isolated murine PDGFRα and Sca-1 double-positive DPSCs could support primitive human CD34+ and CD34– HSCs in vitro.

Slow turnover of HIV-1 receptors on quiescent CD4+ T cells causes prolonged surface retention of gp120 immune complexes in vivo

Peripheral blood CD4(+) T cells in HIV-1(+) patients are coated with Ig. However, the causes and consequences of the presence of Ig(+) CD4(+) T cells remain unknown. Previous studies have demonstrated the rapid turnover of viral receptors (VRs) on lymphoma and tumor cells. The present study investigates the turnover of VRs on peripheral quiescent CD4(+) T cells (qCD4s), which are the most abundant peripheral blood CD4(+) T cells. Utilizing pharmacological and immunological approaches, we found that the turnover of VRs on qCD4s is extremely slow. As a result, exposure to gp120 or HIV-1 virions in vitro causes gp120 to remain on the surface for a long period of time. It requires approximately three days for cell-bound gp120 on the surface to be reduced by 50%. In the presence of patient serum, gp120 forms surface immune complexes (ICs) that are also retained for a long time. Indeed, when examining the percentages of Ig(+) CD4(+) T cells at different stages of HIV-1 infection, approximately 70% of peripheral resting CD4(+) T cells (rCD4s) were coated with surface VRs bound to slow-turnover gp120-Ig. The levels of circulating ICs in patient serum were insufficient to form surface ICs on qCD4s, suggesting that surface ICs on qCD4s require much higher concentrations of HIV-1 exposure such as might be found in lymph nodes. In the presence of macrophages, Ig(+) CD4(+) T cells generated in vitro or directly isolated from HIV-1(+) patients were ultimately phagocytosed. Similarly, the frequencies and percentages of Ig(+) rCD4s were significantly increased in an HIV-1(+) patient after splenectomy, indicating that Ig(+) rCD4s might be removed from circulation and that non-neutralizing anti-envelope antibodies could play a detrimental role in HIV-1 pathogenesis. These findings provide novel insights for vaccine development and a rationale for using Ig(+) rCD4 levels as an independent clinical marker.

Hormonal contraception and HIV-1 infection: medroxyprogesterone acetate suppresses innate and adaptive immune mechanisms

Recent observational studies indicate an association between the use of hormonal contraceptives and acquisition and transmission of HIV-1. The biological and immunological mechanisms underlying the observed association are unknown. Depot medroxyprogesterone acetate (DMPA) is a progestin-only injectable contraceptive that is commonly used in regions with high HIV-1 prevalence. Here we show that medroxyprogesterone acetate (MPA) suppresses the production of key regulators of cellular and humoral immunity involved in orchestrating the immune response to invading pathogens. MPA inhibited the production of interferon (IFN)-γ, IL-2, IL-4, IL-6, IL-12, TNFα, macrophage inflammatory protein-1α (MIP-1α), and other cytokines and chemokines by peripheral blood cells and activated T cells and reduced the production of IFNα and TNFα by plasmacytoid dendritic cells in response to Toll-like receptor-7, -8, and -9 ligands. Women using DMPA displayed lower levels of IFNα in plasma and genital secretions compared with controls with no hormonal contraception. In addition, MPA prevented the down-regulation of HIV-1 coreceptors CXCR4 and CCR5 on the surface of T cells after activation and increased HIV-1 replication in activated peripheral blood mononuclear cell cultures. The presented results suggest that MPA suppresses both innate and adaptive arms of the immune system resulting in a reduction of host resistance to invading pathogens.

Pathogen-specific T cell depletion and reactivation of opportunistic pathogens in HIV infection

During HIV infection, it is unclear why different opportunistic pathogens cause disease at different CD4 T cell count thresholds. Early work has shown that CD4 T cell depletion is influenced both by cellular activation status and expression of viral entry receptors. More recently, functional characteristics of the CD4 T cells, such as cytokine and chemokine production, have also been shown to influence cellular susceptibility to HIV. Here, we examine how functional differences in pathogen-specific CD4 T cells could lead to their differential loss during HIV infection. This may have implications for when different opportunistic infections occur, and a better understanding of the mechanisms for functional imprinting of antigen-specific T cells may lead to improvements in design of vaccines against HIV and opportunistic pathogens.

Reciprocal regulation of CXCR4 and CXCR7 in intestinal mucosal homeostasis and inflammatory bowel disease

IBDs are characterized by increased influx of immune cells to the mucosa of genetically susceptible persons. Cellular migration to injury sites is mediated by chemokines. CXCL12 is a ubiquitous, constitutive chemokine that participates in stem cell proliferation and migration and mediates T lymphocyte migration to inflamed tissues. We have recently reported that CXCL12 and its receptor, CXCR4, are expressed in normal and more prominently, inflamed human intestinal mucosa. However, the interactions and roles of CXCL12 and its receptors, CXCR4 and the recently discovered CXCR7, in intestinal inflammation have not been defined. In the present study, we further dissected the effects of CXCL12 on lymphocytes in intestinal homeostasis and inflammation and delineated the interplay between CXCL12 and its receptors CXCR4 and CXCR7. To that end, fresh mononuclear cells were isolated from mucosa and PB of healthy or IBD patients. Phenotypical and functional assays were conducted using flow cytometry, Transwell migration chambers, and ELISA. The data show that CXCL12-mediated migration of T cells is CXCR4- but not CXCR7-dependent. T cell activation reciprocally regulates CXCR7 and CXCR4 expression and migratory capacity. IBD PBTs expressed more CXCR7 than normal PBTs. Finally, T cells attracted by CXCL12 are mostly of a memory phenotype. In conclusion, the present study suggests that the interplay between CXCL12 and its receptors affects homeostasis and inflammation in the intestinal mucosa.

SDF-1/CXCL12 production by mature dendritic cells inhibits the propagation of X4-tropic HIV-1 isolates at the dendritic cell-T-cell infectious synapse

An efficient mode of HIV-1 infection of CD4 lymphocytes occurs in the context of infectious synapses, where dendritic cells (DCs) enhance HIV-1 transmission to lymphocytes. Emergence of CXCR4-using (X4) HIV-1 strains occurs late in the course of HIV-1 infection, suggesting that a selective pressure suppresses the switch from CCR5 (R5) to X4 tropism. We postulated that SDF-1/CXCL12 chemokine production by DCs could be involved in this process. We observed CXCL12 expression by DCs in vivo in the parafollicular compartment of lymph nodes. The role of mature monocyte-derived dendritic cells (mMDDCs) in transmitting R5 and X4 HIV-1 strains to autologous lymphocytes was studied using an in vitro infection system. Using this model, we observed a strong enhancement of lymphocyte infection with R5, but not with X4, viruses. This lack of DC-mediated enhancement in the propagation of X4 viruses was proportional to CXCL12 production by mMDDCs. When CXCL12 activity was inhibited with specific neutralizing antibodies or small interfering RNAs (siRNAs), the block to mMDDC transfer of X4 viruses to lymphocytes was removed. These results suggest that CXCL12 production by DCs resident in lymph nodes represents an antiviral mechanism in the context of the infectious synapse that could account for the delayed appearance of X4 viruses.

Pairwise comparison of isogenic HIV-1 viruses: R5 phenotype replicates more efficiently than X4 phenotype in primary CD4+ T cells expressing physiological levels of CXCR4

CCR5-using (R5) HIV-1 strains are present during the whole course of the infection in all subjects, whereas CXCR4-using (X4) HIV-1 strains appear only in the late stages of the infection in some subjects. In this study, we tested the hypothesis that this phenomenon might be the result of a replicative advantage of R5 over X4 strains. We compared the infectivity of an R5 and an X4 strain that differ only in their env gene in peripheral blood mononuclear cells. CD4 T cells in culture, where the CXCR4 ligand SDF-1 is absent, overexpress CXCR4 at their surface. Therefore, a cell line producing the chemokine SDF-1, that binds to and induces the internalization of CXCR4, was established by transfer of the SDF-1 gene. We cocultured peripheral blood mononuclear cells with this SDF-1-producing cell line to obtain SDF-1 concentrations that maintained the CD4 T cell surface CXCR4 densities observed in vivo. Under these conditions, the R5 strain appeared to replicate more efficiently than the X4 strain. Thus, in vitro, when CD4 T cells express physiological levels of CXCR4 coreceptors, R5 virions are more fit for replication than X4 virions and in vivo that limited surface expression of CXCR4 on cell targets could contribute to the preponderance of R5 viruses.

In vivo CXCR4 expression, lymphoid cell phenotype, and feline immunodeficiency virus infection

Primary isolates of feline immunodeficiency virus (FIV) appear to require binding to CD134 in conjunction with CXCR4(X4) to infect IL-2-dependent T-cell-derived cells in culture. However, much less is known about the role of X4 for the infection of cells in vivo. To investigate the correlation between X4 expression and FIV infection in cats acutely infected with FIV-C-Pgmr we used high-speed fluorescence-activated cell sorting and realtime PCR to co-analyze cell phenotypes from lymph node, thymus, bone marrow and blood for FIV infection and X4 expression. X4 expression was greatest in lymph node, both in frequency and in mean fluorescence intensity. The thymus demonstrated a higher proviral burden in X4+ thymic T cells ( approximately 14% in X4+ thymic T cells and 7% in X4- cells) whereas, proviral loads were similar between X4+ and X4- cell populations in all other tissues examined. Assuming a minimum of one proviral copy per cell, a maximum of approximately 50% of FIV-positive cells were X4+. The highest fraction of FIV-infected X4- cells was present in bone marrow. Regardless of X4 status, proviral loads were higher in lymph node and blood T cells than in B cells. These studies provide both a positive association between X4 expression and FIV infection and introduce the probability that X4-independent infection occurs in other target cells in vivo.

Development of peptide-targeted lipoplexes to CXCR4-expressing rat glioma cells and rat proliferating endothelial cells

A peptide analog, 4-fluorobenzoyl-RR-(L-3-(2-naphthyl)alanine)-CYEK-(L-citrulline)-PYR-(L-citrulline)-CR, covalently linked to a phospholipid, was used for targeting a lipid-based gene delivery vehicle to CXCR4(+)-cells. Characterization of transfection activity was done in vitro using a transformed rat glioma cell line (RG2) that expresses CXCR4. The substitution of the targeting lipid at increasing mole percentages in the place of helper lipids yielded a progressive increase in reporter gene expression, reaching a maximum of 2.5 times the control value at 20 mol% of ligand. The substitution of helper lipids with cysteine-derivatized phospholipid analog or phosphatidylethanolamine resulted in a progressive decrease in transfection activity, with complete inactivation of the complex occurring at 20 mol%. A DNA dose-response with 10 mol% of lipopeptide reduced the effective DNA dose at least fivefold with regard to the number of transfected cells and >20-fold with regard to the amount of gene expression. Gene transfer to rat endothelial cells was studied in the context of an arterial organ culture. Mesenteric arteries were cannulated and maintained in culture for up to 4 days. CXCR4 cell-surface expression on endothelial cells was induced after overnight incubation with vascular endothelial growth factor (VEGF). Gene transfer studies showed that only the peptide-targeted lipoplexes transfected the endothelium, and only after CXCR4 had been induced with VEGF. These results demonstrate that non-viral transfection complexes can be targeted to cells expressing CXCR4, and that gene transfer is dependent upon cell surface receptor expression levels.

Up-regulation of leukocyte CXCR4 expression by sulfatide: An L-selectin-dependent pathway on CD4+ T cells

CXCR4 plays significant roles in immune and inflammatory responses and is important for selective recruitment of leukocytes. We previously showed that CXCR4 surface expression of human lymphocytes was affected by sulfatide, an in vivo ligand for L-selectin. Increased CXCR4 expression was shown to promote biologically relevant functions such as integrin-dependent adhesion and transmigration. Here, we show that sulfatide-induced CXCR4 up-regulation also occurs on other leukocyte subsets in humans and mice. B cells and CD4(+)CD25(+) T cells had the highest CXCR4 up-regulation after sulfatide stimulation. Transfection of L-selectin was sufficient for K562 cells to acquire sulfatide-induced CXCR4 up-regulation, while analysis of L-selectin knockout mice revealed that this response was critically L-selectin dependent only for CD4(+) T cells, suggesting an alternative pathway in CD8(+) T cells and B cells. Sulfatide triggered several intracellular signaling events in CD4(+) T cells, but only tyrosine kinase activation, including members of the Src family, were essential for L-selectin to CXCR4 signaling. CXCR4 up-regulation was rapid, enhanced CXCL12-induced signaling and increased chemotaxis toward CXCL12, and therefore has potentially important roles in vivo. Thus, the response to CXCL12 depends in part on tissue expression of sulfatide and, specifically in CD4(+) T cells, also depends on the surface level of L-selectin.

Circulating mononuclear cells from euthyroid patients with thyroid-associated ophthalmopathy exhibit characteristic phenotypes

Thyroid-associated ophthalmopathy (TAO) is a common yet poorly understood component of Graves' disease involving inflammation, congestion and soft tissue remodelling of the orbit. Unlike most autoimmune disorders, TAO has variable severity but follows a predictable course and is usually self-limited. The objective of this study was to investigate the phenotypic profile of peripheral blood mononuclear cells in euthyroid patients with TAO. The study was a prospective, consecutive analysis of the peripheral blood mononuclear cell phenotype in patients with TAO and normal controls. We demonstrate that the fraction of T cells expressing CD69, CD25 or CXCR4 is significantly greater in patients with TAO compared to control donors. In addition, the fraction of CD19(+) CD25(+) B cells is significantly greater. We did not find differences between the two groups of subjects in monocytes expressing these markers. There is a phenotypic shift in peripheral blood lymphocytes associated with TAO that appears durable and persists beyond the hyperthyroid phase of Graves' disease. These changes may support the immune reaction provoking orbital disease development.

RANTES -28G delays and DC-SIGN - 139C enhances AIDS progression in HIV type 1-infected Japanese hemophiliacs

The relationships between host immune factors and HIV-1 disease progression are still in dispute. Unlike CCR5Delta32, which has been found to delay disease progression of HIV-1, there still remain several factors whose effect on the clinical course is unconfirmed. To clarify the relationships, we selected seven single-nucleotide polymorphisms (SNPs) out of the previously reported factors, namely, RANTES promoter -28G/-403A, RANTES In1.1C, SDF-1 3'A, IL-4 promoter -589T, and DC-SIGN promoter -139C/-336C, and examined these in Japanese HIV-1-infected hemophiliacs (n = 102). The genotypes were examined by the direct sequencing method, and the distributions of genotype and allelic frequencies were compared between two groups, slow progressors (n = 54) who did not develop AIDS more than 10 years after intravenous infection and others (progressors) (n = 48). The allelic frequency of RANTES -28G was significantly higher in slow progressors (0.185) than in the progressor group (0.074) [p = 0.023, OR = 0.35, 95% CI (0.142, 0.880)]. DC-SIGN promoter -139C, and appeared in progressors with significantly higher allelic frequency (0.333) than slow progressors [0.204, p = 0.040, OR = 1.95, 95% CI (1.039, 3.677)]. With RANTES -403A, RANTES In1.1C, SDF-1 3' A, IL-4 -589T, and DC-SIGN -336C, no significant difference was observed in allelic frequencies between the two groups. These results suggest that RANTES -28G was associated with delayed AIDS progression, while DC-SIGN -139C was associated with accelerated AIDS progression in HIV-1-infected Japanese hemophiliacs.

Up-regulation of functional CXCR4 expression on human lymphocytes in sepsis

OBJECTIVE

Lymphocyte dysfunction has been documented in sepsis, and evidence suggests that lymphocyte infiltration contributes to tissue injury. The purpose of this study was to examine chemokine receptor expression and function in lymphocytes from septic patients and healthy donors.

DESIGN

Observational study of septic patients and laboratory investigation of normal controls.

SETTING

Tertiary care intensive care unit.

PATIENTS AND SUBJECTS

Nine critically ill patients fulfilling criteria for the systemic inflammatory response syndrome and with a Sepsis Score of >/=3 were included in this study. Lymphocytes were also obtained from healthy volunteers.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The total number of circulating leukocytes in septic patients was markedly increased; however, lymphocyte counts were decreased. Chemokine receptor expression on lymphocytes was examined by flow cytometry. CXCR4 expression on lymphocytes from septic patients was increased whereas CCR5 was decreased and CCR7 was unchanged. Lipopolysaccharide stimulation of normal lymphocytes increased CXCR4 expression but decreased CCR5 and did not change CCR7 expression. This lipopolysaccharide-stimulated CXCR4 expression required 20 hrs of stimulation and was accompanied by increased messenger RNA. Lymphocytes from septic patients or after lipopolysaccharide treatment demonstrated enhanced actin polymerization and migration in response to CXCL12. Taken together, sepsis and lipopolysaccharide up-regulated CXCR4 expression and enhanced lymphocyte activation and migration in response to CXCL12.

CONCLUSIONS

Blocking CXCR4 and CXCL12 function may provide a novel therapeutic method for controlling systemic inflammation and tissue injury in sepsis.

Abnormal differentiation of memory T cells in systemic lupus erythematosus

OBJECTIVE

The chemokine receptor CCR7 and the tumor necrosis factor receptor family member CD27 define 3 distinct, progressively more differentiated maturational stages of CD4 memory subpopulations in healthy individuals: the CCR7+, CD27+, the CCR7-, CD27+, and the CCR7-, CD27- populations. The goal of this study was to examine maturational disturbances in CD4 T cell differentiation in systemic lupus erythematosus (SLE), using these phenotypic markers.

METHODS

Phenotypic analysis by flow cytometry, in vitro stimulation experiments, telomere length measurement, and determination of inducible telomerase were carried out. RESULTS. In SLE patients, significant increases of CCR7-, CD27- and CCR7-, CD27+ and a reduction of CCR7+, CD27+ CD4 memory T cells were found. In vitro stimulation of SLE T cells showed a stepwise differentiation from naive to CCR7+, CD27+ to CCR7-, CD27+ to CCR7-, CD27-; telomere length and inducible telomerase decreased in these subsets in the same progressive sequence. The in vitro proliferative response of these populations progressively declined as their susceptibility to apoptosis increased. Interestingly, a significant reduction in inducible telomerase was noted in SLE naive and CCR7+, CD27+ CD4+ memory T cells. Additionally, SLE CCR7-, CD27+ and CCR7-, CD27- CD4 memory T cells proliferated poorly in response to in vitro stimulation and underwent significantly more apoptosis than their normal counterparts. Finally, expression of CXCR4 was significantly reduced in all SLE subsets compared with normal.

CONCLUSION

Together these data indicate an increased degree of in vivo T cell stimulation in SLE, resulting in the accumulation of terminally differentiated memory T cells with a decreased proliferative capacity and an increased tendency to undergo apoptosis upon stimulation.

CXCR4 and CCR5 regulation and expression patterns on T- and monocyte-macrophage cell lineages: implications for susceptibility to infection by HIV-1

Chemokine receptor expression may vary dramatically among cell subsets. Therefore, the stage of differentiation and the lineage of CD4 cells may profoundly affect their susceptibility to infection by human immunodeficiency virus type 1 (HIV-1). However, the mechanisms of coreceptor competition for association with HIV-1 glycoproteins remain unknown. Here, we propose mathematical models that address the interdependence of the concentrations of CD4 and CCR5 for efficient infection by M-tropic HIV-1 as well as additional complications originated by coreceptor competition caused by posttranslational modifications that positively or negatively affect the coreceptor ability to form complexes with CD4 and/or HIV-1 envelope. Furthermore, since CCR5 and CXCR4 expression on human leukocytes designate these cells as HIV-1 potential targets, the expression of the major HIV-1 coreceptors are also dynamically modeled/quantified as function of the stage of cell differentiation. Results show that although coreceptor competition degree has limited influence on R5 strain infectivity, the infectivity of CXCR4-using isolates strongly depends on the CD4 expression, according to the coreceptor competition model proposed in Lee et al. [J. Virol. 74(11) (2000) 5016]. Understanding the role of in vivo alterations in CD4, CCR5 and CXCR4 densities on HIV-1 cell entry may help the development of optimal control strategies for AIDS pathogenesis.

Indian primary HIV-2 isolates and relationship between V3 genotype, biological phenotype and coreceptor usage

The chemokine coreceptors play a significant role in HIV entry and pathogenesis. The V3 region of HIV envelope glycoprotein is considered as a principal determinant for viral phenotype and tropism. The present study describes lack of association between the V3 genotype and viral phenotype of 18 Indian HIV-2 isolates. The viruses were isolated, confirmed by PCR and the HIV subtypes were determined by sequencing V3 region of the env gene. The coreceptor usage and syncytium inducing (SI) capacity of isolates was determined. Our study indicated that CCR5 coreceptor usage and NSI phenotype is predominant among Indian HIV-2 isolates obtained from patients in the early stage of infection. Two of the four HIV-2 isolates obtained from the late stage patients were SI and dual tropic. Phylogenetic analysis of these isolates revealed close relatedness to the isolates from western and southern India.

Prostratin Induces HIV Activation and Downregulates HIV Receptors in Peripheral Blood Lymphocytes

Induction of HIV expression through lymphocyte activation has been proposed as a strategy to purge latent reservoirs. Prostratin is a non-tumourogenic phorbol ester that delays HIV replication in vitro, but paradoxically activates HIV expression in latently infected cells. To get a better insight into the mechanisms of action of prostratin, we have analysed the effect of prostratin on HIV activation and HIV receptor and coreceptors’ surface expression in human lymphocytes. Peripheral blood mononuclear cells (PBMCs) were transfected with luciferase expression constructs under the control of wild type HIV-long terminal repeat (LTR) and consensus sequences for transcription factors involved in HIV-LTR transactivation (NF-κB, SP1, NFAT). Prostratin stimulates transactivation of LTR vectors, κB- and SP-1-driven luciferase constructs. In another set of experiments, PBMCs were transfected with a full-length infectious viral clone. Prostratin induced HIV transcription and viral expression as detected by luciferase activity in cellular extracts and p24 levels in culture supernatants, respectively. Expression of the HIV coreceptors CCR5 and CXCR4 was decreased by prostratin and, concomitantly, prostratin inhibited the infection of PBMCs with R5 and X4 strains. However, prostratin did not inhibit infection with a pseudotyped viral clone that enters into the cells independently of HIV receptors. These results help to explain the paradoxical effects of prostratin. On one hand, prostratin induces HIV activation in latently infected cells through the induction of NF-κB and Sp1. On the other hand, strong and persistent downregulation of HIV receptors decreases infection of new targets and delays HIV propagation. These data support the potential use of prostratin to activate HIV from latency and purge viral reservoirs.

Kinetic analysis of genomewide gene expression reveals molecule circuitries that control T cell activation and Th1/2 differentiation

The global gene expression profiling of early T helper (Th) 1 and Th2 differentiation reveals that this process can be divided into two stages, activation and differentiation. The activation stage is manifested in coordinated mobilization of the replication machinery, a process that we hypothesize may be responsible for establishing genomewide opening of transcription loci. The molecular programs underlying the differentiation stage consist of highly regulated expression of functional groups of genes that are important for the biological properties of Th1/2 cells and transcription factors that are likely important in establishing terminal differentiation of these cells. The kinetics of expression pattern of a number of transcription factors shed new light on the molecular events that shape the outcome of Th1/2 differentiation.

L-selectin stimulation enhances functional expression of surface CXCR4 in lymphocytes: implications for cellular activation during adhesion and migration

L-selectin mediates leukocyte tethering and rolling, the first step in a sequential process of leukocyte adhesion and migration. Additionally, L-selectin has important signaling roles perhaps contributing to leukocyte activation and integrin-mediated adhesion. Because chemokines are critically involved in leukocyte activation, we questioned whether L-selectin signaling affects chemokine receptor expression and function. We observed that whereas only 5% to 15% of freshly isolated lymphocytes expressed CXCR4 on the cell surface, intracellular CXCR4 was detectable in all cells. Engagement of L-selectin by antibody cross-linking or the L-selectin ligands fucoidan or sulfatide mobilized intracellular CXCR4 to significantly increase surface CXCR4 expression but did not affect CCR5, CCR7, or beta2-integrin expression. L-selectin stimulation also inhibited stromal-derived factor 1 (SDF-1)-induced CXCR4 internalization. The combined effects of L-selectin on CXCR4 trafficking are likely important in markedly enhancing cell activation by SDF-1. Blockade of SDF-1-induced CXCR4 internalization resulted in enhanced actin polymerization on subsequent exposure to SDF-1. Physiologically more important, L-selectin stimulation increased SDF-1-induced lymphocyte adhesion and transendothelial migration, which were inhibited by anti-leukocyte function-associated antigen 1 antibodies, tyrosine kinase inhibitors, and pertussis toxin. To further corroborate the additive stimulating effects, L-selectin signaling and SDF-1 increased beta2-integrin activation. Taken together, L-selectin-mediated signals specifically enhance CXCR4 expression and function, suggesting a novel mechanism for the modulation of lymphocyte activation during cell adhesion and transmigration.

Positive regulation of CXCR4 expression and signaling by interleukin-7 in CD4+ mature thymocytes correlates with their capacity to favor human immunodeficiency X4 virus replication

The emergence of X4 human immunodeficiency virus type 1 (HIV-1) variants in infected individuals is associated with poor prognosis. One of the possible causes of this emergence might be the selection of X4 variants in some specific tissue compartment. We demonstrate that the thymic microenvironment favors the replication of X4 variants by positively modulating the expression and signaling of CXCR4 in mature CD4(+) CD8(-) CD3(+) thymocytes. Here, we show that the interaction of thymic epithelial cells (TEC) with these thymocytes in culture induces an upregulation of CXCR4 expression. The cytokine secreted by TEC, interleukin-7 (IL-7), increases cell surface expression of CXCR4 and efficiently overcomes the downregulation induced by SDF-1 alpha, also produced by TEC. IL-7 also potentiates CXCR4 signaling, leading to actin polymerization, a process necessary for virus entry. In contrast, in intermediate CD4(+) CD8(-) CD3(-) thymocytes, the other subpopulation known to allow virus replication, TEC or IL-7 has little or no effect on CXCR4 expression and signaling. CCR5 is expressed at similarly low levels in the two thymocyte subpopulations, and neither its expression nor its signaling was modified by the cytokines tested. This positive regulation of CXCR4 by IL-7 in mature CD4(+) thymocytes correlates with their high capacity to favor X4 virus replication compared with intermediate thymocytes or peripheral blood mononuclear cells. Indeed, we observed an enrichment of X4 viruses after replication in thymocytes initially infected with a mixture of X4 (NL4-3) and R5 (NLAD8) HIV strains and after the emergence of X4 variants from an R5 primary isolate during culture in mature thymocytes.

Optimization of ex vivo activation and expansion of macaque primary CD4-enriched peripheral blood mononuclear cells for use in anti-HIV immunotherapy and gene therapy strategies

The rhesus macaque model is a useful experimental system to evaluate effects of T-cell autotransfusion and gene therapies for HIV-1 infection and AIDS prior to a clinical trial. To obtain sufficient numbers of primary macaque CD4 T lymphocytes for this purpose, we examined the culture conditions that were needed to optimize ex vivo activation and expansion of macaque primary CD4-enriched peripheral blood mononuclear cells (PBMCs). In this report, we compared the effects of various stimulants on cell expansion, surface expression of CCR5 and CXCR4, and levels of transduction with a Moloney leukemia virus (MoLV) vector encoding the phenotypic selection marker truncated human nerve growth factor receptor (deltaNGFR) alone or with the human anti-HIV-1 tat intrabody sFvhutat2. The use of feeder cells strikingly increased the proliferation rate of macaque CD4-enriched PBMCs in vitro. In the presence of an irradiated rhesus macaque B-lymphoblastoid cell line (BLCL), the highest cell expansion over 21 days was achieved with cells activated by Con A (9648-fold), in turn, from high to low, phytohemagglutinin (PHA) (4855-fold), and anti-CD3/CD28-coated beads (2367-fold). Further studies showed that BLCL feeder cells were more effective than human PBMCs (hPBMCs) in promoting proliferation of macaque CD4-enriched PBMCs activated with Con A and anti-CD3/CD28, respectively. The combined use of both BLCL and hPBMC feeder cells did not further increase cell expansion when compared with the use of BLCL cells alone. In addition, the addition of BLCL-conditioned medium (CM) and hPBMC-CM induced cell growth at a rate higher than did the culture medium alone but not as high as with feeder cells. Con A-activated macaque CD4-enriched PBMCs retained 88% of CXCR4 and 39% of CCR5 expression over 17 days compared with PHA-activated cells (50% for CXCR4, 16% for CCR5) and anti-CD3/CD28-activated cells (34% for CXCR4, 37% for CCR5). Finally, PHA, Con A, and CD3/CD28-coated beads supported comparable levels of MoLV transduction. The results should improve the utility of the rhesus macaque model for the testing of T-cell autotransfusion and gene therapies for HIV-1 infection/AIDS.

Ex vivo isolation protocols differentially affect the phenotype of human CD4+ T cells

Leukemic T cell lines have facilitated signal transduction studies but their physiological relevance is restricted. The use of primary T lymphocytes overcomes this limitation but it has long been speculated that methodological aspects of blood collection and the isolation procedure modify the phenotype of the cell. Here we demonstrate that several characteristics of human peripheral T cells are affected by the selection conditions. A significantly higher induction of the chemokine receptor CXCR4 was observed on CD4+ lymphocytes isolated by sheep red blood cell (SRBC) rosetting and CD4 MicroBeads as compared with positively selected CD4+ cells where the antibody/bead complex was immediately detached. These latter cells expressed CXCR4 at levels equivalent to that observed on CD4+ lymphocytes obtained by negative antibody-mediated selection. Furthermore, CD4+ cells isolated by SRBC rosetting and CD4 MicroBeads formed aggregates upon in vitro culture. CD4+ lymphocytes obtained by SRBC rosetting as well as those isolated following positive selection demonstrated basal phosphorylation of the extracellular signal-regulated kinase (ERK)-2. Altogether these data suggest that certain discrepancies concerning signal transduction in primary human T cells can be attributed to the selection conditions. Thus, it is essential to establish the parameters influenced by the isolation protocol in order to fully interpret T cell responses to antigens, chemokines, and cytokines.

gp120-mediated induction of the MAPK cascade is dependent on the activation state of CD4(+) lymphocytes

The capacity of the HIV-1 envelope glycoprotein gp120 to induce intracellular signals is thought to contribute to HIV-1 pathogenesis. Here, we report that gp120 binding resulted in activation of the mitogen-activated protein kinase (MAPK) in CD4(+) lymphocytes prestimulated through their T-cell receptor (TCR). However, gp120 did not activate this pathway in either freshly isolated quiescent T cells or nonproliferating CD4(+) lymphocytes prestimulated with the interleukin-7 (IL-7) cytokine. This response was not solely dependent on proliferation per se because proliferating IL-7-prestimulated umbilical cord (UC)-derived T lymphocytes did not exhibit significant MAPK activation upon gp120 binding. Nevertheless, like peripheral blood lymphocytes, MAPK recruitment was induced by gp120 in UC T cells following TCR prestimulation. The lack of a gp120-mediated signaling response was not due to decreased gp120 receptor levels; CD4 expression was modified neither by IL-7 nor by TCR engagement, and high levels of functional CXCR4 were present on IL-7-treated lymphocytes. In addition to CD4 and CXCR4, recent evidence suggests that glycosphingolipids in raft microdomains serve as cofactors for HIV-1 fusion. The ganglioside GM1, a marker of rafts, was augmented in TCR-stimulated but not IL-7-stimulated T lymphocytes, and disruption of rafts inhibited gp120-induced signaling. Thus, stimulation of a mitogenic pathway by gp120 appears to require receptor binding in the context of membrane microdomains. These studies reveal a mechanism via which gp120 may differentially modulate the fate of activated and quiescent T cells in vivo.

Involvement of the interferon-gamma-induced T cell-attracting chemokines, interferon-gamma-inducible 10-kd protein (CXCL10) and monokine induced by interferon-gamma (CXCL9), in the salivary gland lesions of patients with Sjögren's syndrome

OBJECTIVE

To elucidate the mechanism of the development of T cell infiltrates in the salivary glands of patients with Sjögren's syndrome (SS), we studied T cell-attracting chemokines and their receptors.

METHODS

The expression of the T cell-attracting chemokines, interferon-gamma (IFNgamma)-inducible 10-kd protein (IP-10; also called CXCL10), monokine induced by IFNgamma (Mig; also called CXCL9), and stromal cell-derived factor 1 (SDF-1; also called CXCL12), in salivary glands from SS patients was investigated by polymerase chain reaction-enzyme-linked immunosorbent assay (ELISA). Cells that produce chemokines and lymphocytes that express chemokine receptors were identified by immunohistochemistry. The production of IP-10 and Mig proteins by salivary epithelial cells in response to IFNgamma was determined by ELISA.

RESULTS

Expression of IP-10 and Mig messenger RNA (mRNA) was significantly up-regulated in SS salivary glands compared with normal salivary glands (both P < 0.01). There was no significant difference in SDF-1 mRNA expression between the SS and normal salivary glands. IP-10 and Mig proteins were predominantly expressed in the ductal epithelium adjacent to lymphoid infiltrates. Most of the CD3+ infiltrating lymphocytes in dense periductal foci expressed CXCR3, the receptor for IP-10 and Mig. IFNgamma induced the production of high levels of IP-10 and Mig proteins from cultured SS salivary epithelial cells.

CONCLUSION

These findings suggest that IFNgamma stimulates the production of IP-10 and Mig in the SS ductal epithelium, and that IP-10 and Mig are involved in the accumulation of T cell infiltrates in the SS salivary gland. Chemokines or chemokine receptors could be a rational new therapeutic target in SS.

Follicular dendritic cell-mediated up-regulation of CXCR4 expression on CD4 T cells and HIV pathogenesis

Follicular dendritic cells (FDCs) represent a major reservoir of HIV, and active infection occurs surrounding these cells, suggesting that this microenvironment is highly conducive to virus transmission. Because CD4 T cells around FDCs in germinal centers express the HIV coreceptor, CXCR4, whereas CD4 lymphocytes in many other sites do not, it prompted the hypothesis that FDCs may increase CXCR4 expression on CD4 T cells, thereby facilitating infection. To test this, HIV receptor/coreceptor expression was determined on CD4 T cells cultured with or without FDCs, and its consequence to infection was assessed by measuring virus binding and entry. FDCs had little effect on CCR5 or CD4 expression but increased CXCR4 expression on CD4 T cells. FDC-mediated up-regulation of CXCR4 on CD4 T cells occurred by 24 h and was sustained for at least 96 h in vitro, and FDC-CD4 T cell contact was necessary. Importantly, increased CXCR4 expression directly correlated with increased binding and entry of HIV-1 X4 isolates. Furthermore, CD4(+)CD57(+) germinal center T cells expressed high levels of CXCR4 and supported enhanced entry of X4 HIV compared with other CD4 T cells from the same tissue. Thus, in addition to serving as a reservoir of infectious virus, FDCs render surrounding germinal center T cells highly susceptible to infection with X4 isolates of HIV-1.

TGF-beta1 enhances SDF-1alpha-induced chemotaxis and homing of naive T cells by up-regulating CXCR4 expression and downstream cytoskeletal effector molecules

The migration of immunocytes within the extracellular matrix (ECM) is influenced by the activation state of the incoming cell and its responses to the presence of chemokines and cytokines. We studied the regulatory role of TGF-beta1 on T cell homing to secondary lymphatic organs, such as the spleen, and chemotaxis within an ECM-like environment in using an ECM-like 3-dimensional gel system designed to follow the migration of individual leukocytes along chemokine gradients in real time. The numbers of migrating naive, but not memory T cells toward SDF-1alpha markedly increased after pre-incubating the cells with TGF-beta1 (0.25 ng/ml) for 24 h. The mechanisms underlying TGFbeta1-modulated migration involve the up-regulation of the expression of the SDF-1alpha receptor CXCR4, the enhancement of the SDF-1alpha-induced actin polymerization, and increased phosphorylation of Pyk2, a focal adhesion kinase involved in integrin-mediated lymphocyte migration, adhesion and interactions with ECM. Interestingly, priming of naive human T cells with TGF-beta1 increased homing of these cells to the spleen of NOD/SCID mice in a CXCR4-dependent manner. We propose that the effect of TGF-beta1 on the chemotaxis of naive T cells may be important in the locomotion of naive T cells toward SDF-1alpha-rich niches.

Differential expression of chemokines and chemokine receptors shapes the inflammatory response in rejecting human liver transplants

BACKGROUND

Graft rejection after liver transplantation is associated with a lymphocytic infiltrate, the nature of which will be determined by, among various factors, the local activity of chemokines that attract particular subsets of effector cells to the graft.

METHODS

The expression of chemokines and receptors in human liver allografts was studied by immunohistochemistry of tissue and flow cytometry of blood and liver-derived lymphocytes. Receptor function was assessed with in vitro chemotaxis.

RESULTS

We report increased expression of chemokine receptors CXCR3, CXCR4, and CCR5 on circulating and graft-infiltrating lymphocytes after liver transplantation. Liver-derived T cells responded to the ligands for these receptors in vitro, which suggests that the receptors are functionally active. The chemokine ligands for these receptors were detected in rejecting allografts. CXCR3 ligands interferon-inducible protein 10 and monokine-induced by gamma interferon were detected on sinusoidal endothelium and interferon-inducible T-cell alpha chemoattractant was detected on portal and hepatic vascular endothelium, whereas the CXCR4 ligand, stromal-derived factor (SDF), was restricted to biliary epithelium. CCR5 ligands have previously been shown on portal endothelium. An in vitro model of T-cell alloactivation demonstrated a similar pattern of expression of functional CXCR3, CXCR4, and CCR5 on T cells. Increased expression of chemokine receptors, especially CCR3 and CCR5, was associated with redistribution of activated Kupffer cells in rejecting grafts.

CONCLUSIONS

The patterns of chemokine expression in liver allografts during rejection suggest that the recruitment and positioning of lymphocytes is mediated by specific chemokines. Although ligands for the receptors CXCR3 and CCR5 are important for recruitment, the restriction of SDF to bile ducts suggests that CXCR4 may be involved in the retention of alloactivated lymphocytes at sites of graft damage.

Diverse transcriptional response of CD4+ T cells to stromal cell-derived factor SDF-1: cell survival promotion and priming effects of SDF-1 on CD4+ T cells

Stromal cell-derived factor (SDF)-1 is a ligand for the chemokine receptor CXCR4 which is broadly expressed in lymphocytes, but the effects of SDF-1 on T cells are largely unknown. When examined using complementary DNA microarray, up-regulation of genes which are associated with DNA repair, detoxification, apoptosis, cell morphology, cell adhesion, and signal transduction was seen in CD4(+) T cells upon SDF-1 exposure. SDF-1 was shown to promote CD4(+) T cell survival through the phosphatidylinositol 3-kinase (PI3K)- and mitogen-activated protein kinase (MAPK)-cascades without cell cycle progression. The proapoptotic Bcl-2 antagonistic of cell death protein was also seen inactivated by the SDF-1-mediated activation of MAPK-extracellular signal-regulated kinases (MEK)-extracellular signal-regulated kinase-ribosomal S6 kinases- and PI3K-pathways. Moreover, the genes known to be associated with cell survival were up-regulated upon SDF-1 exposure and were linked to the MAPK-MEK and PI3K-pathways. Thus, SDF-1 promotes cell survival by two mechanisms: posttranslational inactivation of the cell death machinery and an increased transcription of cell survival-related genes. SDF-1 also primed resting CD4(+) T cells for cytokine- and TCR-mediated stimuli. These data suggest that the SDF-1-mediated cell survival combined with its priming function would set T cells to respond to immunologic challenges.

Loss of chemokine SDF-1alpha-mediated CXCR4 signalling and receptor internalization in human hepatoma cell line HepG2

Expression of the chemokine stromal cell-derived factor-1alpha (SDF-1alpha) is absent from many carcinomas, including hepatomas. We note an early signalling defect in the hepatocellular carcinoma (HCC) cell line HepG2 that expresses the CXCR4 receptor and binds biotin-labelled SDF, but fails to stimulate downstream signalling events after engagement with SDF. In HepG2, the SDF/CXCR4 interaction did not result in calcium influx, phosphorylation and internalization of CXCR4, nor in a rapid phosphorylation of p44/42 MAP kinase. There were no CXCR4 mutations in the second chemokine binding loop or C terminal phosphorylation and internalization domains. The downstream signalling machinery in HepG2 appears to be intact since transfection of wild-type CXCR4 restored functional responsiveness. We conclude that HepG2 is unresponsive to SDF stimulation because of a defect located after receptor binding but before the activation of the signalling cascade. A hypothetical blocking molecule could hinder receptor internalization or CXCR4 signalling.

Coregulation of CXC chemokine receptor and CD4 expression on T lymphocytes during allogeneic activation

Upon activation, naive T cells alter their migratory patterns, acquiring the ability to move through peripheral tissues as well as the general lymphoid circulation. Although the mechanisms responsible for these alterations are not well understood, changes in chemokine receptor expression may play a critical role. To investigate these changes, the expression patterns of two chemokine receptors, CXCR3 and CXCR4, were compared on CD4(+) T cells following activation in the MLR. By day 9 of activation, expression of the inflammatory chemokine receptor CXCR3 was up-regulated, while expression of the homeostatic chemokine receptor CXCR4 was down-regulated. Alterations in receptor expression occurred almost exclusively on a subpopulation of T cells that expressed higher levels of CD4. These CD4(high) T cells demonstrated many characteristics of activated T cells and had undergone division in the MLR. By day 9 of culture, the majority of CXCR3(+) and CXCR4(-) cells had divided and had acquired an activated/memory phenotype (CD45RA(-) CD45RO(+) CD69(+) CD25(+)). The levels of transcripts for both CXCR3 and CXCR4 were increased upon allo-activation. The discrepancy between levels of CXCR4 mRNA and surface protein was not due to sequestration of the receptor in intracellular compartments, as CXCR4 was not detectable intracellularly. However, intracellular CXCR3 was readily detectable. Finally, cells from allogeneic cultures demonstrated enhanced migration toward IFN-inducible T cell alpha chemoattractant and reduced migration toward stromal cell-derived factor-1 compared with syngeneic controls, thus suggesting that the observed switch in receptor expression may at least partly contribute to the differential patterns of migration displayed by naive and memory T cells.

Duration of sample storage dramatically alters expression of the human immunodeficiency virus coreceptors CXCR4 and CCR5

Expression of the chemokine receptors CXCR4 and CCR5 was monitored using EDTA-anticoagulated whole blood held for different time periods prior to fluorescent-antibody staining. When left overnight CXCR4 expression on leukocytes was substantially increased, whereas CCR5 expression was reduced. The results were similar when heparin and acid-citrate-dextrose were used as anticoagulants.

Characterization of high-risk HIV-1 seronegative hemophiliacs

Mechanisms that protect most high-risk HIV-1 seronegative (HRSN) persons are not well understood. Among hemophiliacs from the Multicenter Hemophilia Cohort Study who remained HIV-1 seronegative despite a high (94%) risk for acquisition of HIV-1 infection, only 7/43 were homozygous for the protective CCR5 Delta32 polymorphism. Among the remainder, neither CCR5 density nor beta-chemokine production, nor in vitro susceptibility to infection with the HIV-1 isolate JR-FL could distinguish HRSN hemophiliacs from healthy controls. When compared to lymphocytes of healthy controls not at risk for HIV-1 infection, diminished spontaneous lymphocyte proliferation was seen in lymphocytes of HRSN hemophiliacs as well as in lymphocytes of hemophiliacs not at risk for HIV-1 infection. Surprisingly sera/plasmas obtained from high-risk HIV-1 seropositve hemophiliacs prior to seroconversion more often contained alloreactive antibodies than date-matched sera/plasmas obtained from HRSN hemophiliacs. Thus alloreactivity may predispose to acquisition of HIV-1 infection after parenteral exposure.

CXCR4 is down-regulated in cells infected with the CD4-independent X4 human immunodeficiency virus type 1 isolate m7NDK

Macrophages and T cells infected in vitro with CD4-dependent human immunodeficiency virus type 1 (HIV-1) isolates have reduced levels of CD4 protein, a phenomenon involved in retroviral interference. We have previously characterized the first CD4-independent HIV-1 X4 isolate m7NDK, which directly interacts with CXCR4 through its mutated gp120. We thus investigate CXCR4 expression in cells infected with this m7NDK CXCR4-dependent HIV-1 mutant. We present evidence of the down-regulation of CXCR4 membrane expression in CD4-positive or -negative cells chronically infected with the HIV-1 m7NDK, a phenomenon which is not observed in the CD4-dependent HIV-1 NDK parental strain. This down-regulation of CXCR4 was demonstrated by fluorescence-activated cell sorter analysis and was confirmed by the absence of CXCR4 functionality in m7NDK-infected cells, independently of the presence of CD4 protein. Furthermore, a drastic reduction of the intracellular level of CXCR4 protein was also observed. Reduced levels of CXCR4 mRNA transcripts were found in m7NDK-infected HeLa and CEM cells, reduced levels that could not be attributed to a reduced stability of CXCR4 mRNA. Down-regulation of CXCR4 on m7NDK-infected cells may thus be explained by transcriptional regulation.

CXC chemokine receptor 5 expression defines follicular homing T cells with B cell helper function

Leukocyte traffic through secondary lymphoid tissues is finely tuned by chemokines. We have studied the functional properties of a human T cell subset marked by the expression of CXC chemokine receptor 5 (CXCR5). Memory but not naive T cells from tonsils are CXCR5(+) and migrate in response to the B cell-attracting chemokine 1 (BCA-1), which is selectively expressed by reticular cells and blood vessels within B cell follicles. Tonsillar CXCR5(+) T cells do not respond to other chemokines present in secondary lymphoid tissues, including secondary lymphoid tissue chemokine (SLC), EBV-induced molecule 1 ligand chemokine (ELC), and stromal cell-derived factor 1 (SDF-1). The involvement of tonsillar CXCR5(+) T cells in humoral immune responses is suggested by their localization in the mantle and light zone germinal centers of B cell follicles and by the concomitant expression of activation and costimulatory markers, including CD69, HLA-DR, and inducible costimulator (ICOS). Peripheral blood CXCR5(+) T cells also belong to the CD4(+) memory T cell subset but, in contrast to tonsillar cells, are in a resting state and migrate weakly to chemokines. CXCR5(+) T cells are very inefficient in the production of cytokines but potently induce antibody production during coculture with B cells. These properties portray CXCR5(+) T cells as a distinct memory T cell subset with B cell helper function, designated here as follicular B helper T cells (T(FH)).