Surface Expression Of CCR5 Research Articles

Inhibition of HIV-1 replication by GB virus C infection through increases in RANTES, MlP-lα, MIP-1β, and SDF-1

Background People coinfected with HIV and GB virus C (GBV-C) have lower mortality than HIV-positive individuals without GBV-C infection. HIV uses either of the chemokine receptors CCR5 and CXCR4 for entry into CD4-positive cells. Longer survival in HIV-positive individuals is associated with high serum concentrations of ligands for CCR5 (RANTES [regulated on activation, normal T-cell expressed and secreted] and macrophage inflammatory proteins [MIP] 1alpha and 1beta) and CXCR4 (stromal-derived factor [SDF-1]), and with decreased expression of CCR5 on lymphocytes. Methods Peripheral-blood mononuclear cells were coinfected with GBV-C and HIV, and HIV replication was monitored by measuring infectivity and HIV p24 antigen production. Chemokine secretion was measured by ELISA, chemokine-receptor expression by flow cytometry, and cellular chemokine mRNA expression by differential hybridisation. Findings GBV-C infection of peripheral-blood mononuclear cells resulted in decreased replication of both clinical and laboratory HIV strains that use either CCR5 or CXCR4 as their coreceptor. Inhibition was related to the dose and timing of the GBV-C infection. Expression of mRNA for RANTES, MIP-1alpha, MIP-1beta, and SDF-1 and secretion of the chemokines into culture supernatants were higher in GBV-C-infected cells than in mock-infected cells. The inhibitory effect of GBV-C on HIV replication was blocked by incubation with neutralising antibodies against the relevant chemokines, and surface expression of CCR5 was significantly lower in GBV-C-infected cells than in mock-infected cells. Interpretation GBV-C induces HIV-inhibitory chemokines and reduces expression of the HIV coreceptor CCR5 in vitro. This study provides insight into the epidemiological association between GBV-C infection and longer survival in HIV-infected individuals.

Increase in CCR5 Delta32/Delta32 genotype in multiple sclerosis.

Chemokines and their receptors participate in the development of multiple sclerosis (MS) by guiding immune cells into the brain tissue. A CCR5 Delta32 deletion mutation abolishes functional CCR5 on the cell surface and may reduce cell entry into the lesion sites. To analyse the significance of this mutation in MS, we compared the frequencies of CCR5 genotype in peripheral blood mononuclear cells from 89 MS patients and 119 healthy controls. The CCR5 genotype was further compared with the CCR5 RNA and surface protein expression in 48 MS patients and their controls. In all MS patients, the Delta32/32 genotype was found with 6.7% frequency, whereas it was present only in 0.8% of the controls (6/89 vs 1/119, P = 0.01). Specifically, the Delta32/Delta32 genotype was increased (11.5%, P = 0.05) among primary progressive MS patients, whereas it was present only in 4.8% in other MS subtypes and only in 0.8% of the controls. The amount of CCR5 protein on CD4(+) cells analysed in 48 MS patients (nine primary progressive MS, 18 secondary progressive MS, 21 relapsing-remitting MS) and 13 controls decreased with genotype, being 8.9% in wt/wt, 7.7% in wt/Delta32 and 4.3% in Delta32/Delta32. CCR5 surface expression analysed on these 48 MS patients and 13 controls was significantly decreased in Delta32/Delta32 MS patients as compared with that in wt/wt genotype individuals (P = 0.004). The significantly increased number of Delta32/Delta32 individuals among our MS patients suggests that this genotype could contribute as a general risk factor for MS. However, neither the levels of RNA or surface protein correlated with MS subtype, neurological disability as expressed by expanded disability status scale, or disease progression index. Our results suggest that the lack of CCR5 does not protect from MS, but rather it may predispose to the chronic course of the disease. This would further imply that in view of the redundancy in the chemokine system, CCR5 ligands must be assumed to function through other closely related chemokine receptors.

Effects of human immunodeficiency virus type 1 infection on CCR5 and CXCR4 coreceptor expression on CD4 T lymphocyte subsets in infants and adolescents.

HIV-1 infection alters expression of CCR5 and CXCR4 on CD4 T cells in adults, although an effect by virus on expression of coreceptor genes in pediatric subjects is unknown. We designed an exploratory study to evaluate surface expression of CXCR4 and CCR5 on CD45RA and CD45RO subsets of CD4 T lymphocytes from 17 HIV-1-infected infants and adolescents and 16 healthy age-matched individuals. While age in the absence of HIV-1 infection was unrelated to coreceptor expression, infection affected coreceptor expression differentially in infants and adolescents. Among infected adolescents, CCR5 and CXCR4 expression was significantly increased on CD4 CD45RO T cells, while CXCR4 was diminished in the CD4 CD45RA subset. Although HIV-1 infection in infants was also associated with increased CXCR4 expression on the CD4 CD45RO subset, in contrast to adolescents, infection in infants had no impact on coreceptor expression within the CD45RA CD4 subset. The proportion of CD4 T cells coexpressing CD45RA and CD45RO was increased by infection in both infants and adolescents. The CD45RA CD45RO subset in culture expressed high levels of CD4, CXCR4, and CD69, an early activation marker, and was highly susceptible to HIV-1 infection and replication. Infection of transitional CD4 T cells coexpressing CD45RA and CD45RO could contribute in part to provirus in either CD45RA or CD45RO subsets. Deleterious effects by HIV-1 infection on CD4 T cell homeostasis were greater in infants then adolescents, indicating that adolescence may be an optimal age group for assessing vaccines to prevent or treat HIV-1 infection.

A CCR2-V64I polymorphism affects stability of CCR2A isoform.

A valine to isoleucine substitution at position 64 of CCR2 (CCR2-64I) is associated with a delay in progression to AIDS in HIV-1-infected individuals. The aim of the present study is to elucidate the molecular mechanism underlying the effect of this allele. We analysed the effect of the 64I substitution on levels of expression of CCR2A and CCR2B, two CCR2 isoforms produced by alternative splicing. Sendai virus vector was used to express CCR2 molecules. While CCR2B trafficked well to the cell surface, CCR2A, which differs from CCR2B only by the sequence of its C-terminal cytoplasmic tail, was detected predominantly in the cytoplasm. The level of expression of CCR2A-64I was significantly higher than that of CCR2A without the substitution. On the other hand, the 64I substitution did not affect levels of CCR2B expression. Pulse-chase experiments revealed that the 64I substitution increased the half-life of CCR2A in cells. When co-expressed with CCR5, CCR2A-64I interfered more severely with cell surface expression of CCR5 than did wild-type CCR2A. Furthermore, immunoprecipitation experiments showed that CCR2A co-precipitated with an immature form of CCR5. These results suggest that CCR2A binds to CCR5 in the cytoplasm and down-modulates its surface expression. We propose that the increased ability of CCR2A-64I to down-modulate CCR5 expression might be a possible cause of a delay in HIV-1 disease progression in patients with this allele.

Role for CCR5Delta32 protein in resistance to R5, R5X4, and X4 human immunodeficiency virus type 1 in primary CD4+ cells.

CCR5Delta32 is a loss-of-function mutation that abolishes cell surface expression of the human immunodeficiency virus (HIV) coreceptor CCR5 and provides genetic resistance to HIV infection and disease progression. Since CXCR4 and other HIV coreceptors also exist, we hypothesized that CCR5Delta32-mediated resistance may be due not only to the loss of CCR5 function but also to a gain-of-function mechanism, specifically the active inhibition of alternative coreceptors by the mutant CCR5Delta32 protein. Here we demonstrate that efficient expression of the CCR5Delta32 protein in primary CD4(+) cells by use of a recombinant adenovirus (Ad5/Delta32) was able to down-regulate surface expression of both wild-type CCR5 and CXCR4 and to confer broad resistance to R5, R5X4, and X4 HIV type 1 (HIV-1). This may be important clinically, since we found that CD4(+) cells purified from peripheral blood mononuclear cells of individuals who were homozygous for CCR5Delta32, which expressed the mutant protein endogenously, consistently expressed lower levels of CXCR4 and showed less susceptibility to X4 HIV-1 isolates than cells from individuals lacking the mutation. Moreover, CD4(+) cells from individuals who were homozygous for CCR5Delta32 expressed the mutant protein in five of five HIV-exposed, uninfected donors tested but not in either of two HIV-infected donors tested. The mechanism of inhibition may involve direct scavenging, since we were able to observe a direct interaction of CCR5 and CXCR4 with CCR5Delta32, both by genetic criteria using the yeast two-hybrid system and by biochemical criteria using the coimmunoprecipitation of heterodimers. Thus, these results suggest that at least two distinct mechanisms may account for genetic resistance to HIV conferred by CCR5Delta32: the loss of wild-type CCR5 surface expression and the generation of CCR5Delta32 protein, which functions as a scavenger of both CCR5 and CXCR4.

Shikonin, a component of chinese herbal medicine, inhibits chemokine receptor function and suppresses human immunodeficiency virus type 1.

Shikonin is a major component of zicao (purple gromwell, the dried root of Lithospermum erythrorhizon), a Chinese herbal medicine with various biological activities, including inhibition of human immunodeficiency virus (HIV) type 1 (HIV-1). G protein-coupled chemokine receptors are used by HIV-1 as coreceptors to enter the host cells. In this study, we assessed the effects of shikonin on chemokine receptor function and HIV-1 replication. The results showed that, at nanomolar concentrations, shikonin inhibited monocyte chemotaxis and calcium flux in response to a variety of CC chemokines (CCL2 [monocyte chemoattractant protein 1], CCL3 [macrophage inflammatory protein 1alpha], and CCL5 [regulated upon activation, normal T-cell expressed and secreted protein]), the CXC chemokine (CXCL12 [stromal cell-derived factor 1alpha]), and classic chemoattractants (formylmethionyl-leucine-phenylalanine and complement fraction C5a). Shikonin down-regulated surface expression of CCR5, a primary HIV-1 coreceptor, on macrophages to a greater degree than the other receptors (CCR1, CCR2, CXCR4, and the formyl peptide receptor) did. CCR5 mRNA expression was also down-regulated by the compound. Additionally, shikonin inhibited the replication of a multidrug-resistant strain and pediatric clinical isolates of HIV in human peripheral blood mononuclear cells, with 50% inhibitory concentrations (IC(50)s) ranging from 96 to 366 nM. Shikonin also effectively inhibited the replication of the HIV Ba-L isolate in monocytes/macrophages, with an IC(50) of 470 nM. Our results suggest that the anti-HIV and anti-inflammatory activities of shikonin may be related to its interference with chemokine receptor expression and function. Therefore, shikonin, as a naturally occurring, low-molecular-weight pan-chemokine receptor inhibitor, constitutes a basis for the development of novel anti-HIV therapeutic agents.

Rapamycin causes down-regulation of CCR5 and accumulation of anti-HIV beta-chemokines: an approach to suppress R5 strains of HIV-1.

Propagation of R5 strains of HIV-1 on CD4 lymphocytes and macrophages requires expression of the CCR5 coreceptor on the cell surface. Individuals lacking CCR5 (CCR5 Delta 32 homozygous genotype) are phenotypically normal and resistant to infection with HIV-1. CCR5 expression on lymphocytes depends on signaling through the IL-2 receptor. By FACS analysis we demonstrate that rapamycin (RAPA), a drug that disrupts IL-2 receptor signaling, reduces CCR5 surface expression on T cells at concentrations as low as 1 nM. In addition, lower concentrations of RAPA (0.01 nM) were sufficient to reduce CCR5 surface expression on maturing monocytes. PCR analysis on peripheral blood mononuclear cells (PBMCs) showed that RAPA interfered with CCR5 expression at the transcriptional level. Reduced expression of CCR5 on PBMCs cultured in the presence of RAPA was associated with increased extracellular levels of macrophage inflammatory protein (MIP)-1 alpha and MIP-1 beta. In infectivity assays, RAPA suppressed the replication of R5 strains of HIV-1 both in PBMC and macrophage cultures. In total PBMC cultures, RAPA-mediated inhibition of CCR5-using strains of HIV-1 occurred at 0.01 nM, a concentration of drug that is approximately 103 times lower than therapeutic through levels of drug in renal transplant recipients. In addition, RAPA enhanced the antiviral activity of the CCR5 antagonist TAK-779. These results suggest that low concentrations of RAPA may have a role in both the treatment and prevention of HIV-1 infection.

Beta-Chemokine production in CD40L-stimulated monocyte-derived macrophages requires activation of MAPK signaling pathways.

CD40 ligand is a cell surface molecule on CD4(+) T cells that interacts with its receptor, CD40, on antigen presenting cells to mediate humoral and cellular immune responses. Our previous studies demonstrated that a trimeric soluble form of CD40L (CD40LT) activates macrophages to produce beta-chemokines and decrease CCR5 and CD4 cell surface expression, thus inducing resistance to HIV-1 infection. However, the mechanism(s) by which CD40LT mediates these effects in primary macrophages remains unclear. In this report, we demonstrate that CD40LT induces synthesis of beta-chemokines through the activation of MAPK signaling pathways. Treatment of macrophages with CD40LT results in a rapid activation of p38 and ERK1/2 mitogen-activated protein kinases. Inhibitors of these MAPKs blocked beta-chemokine production, while protein kinase A and C inhibitors had little or no effect. We also provide evidence that CD40LT stimulates beta-chemokine production directly, as well as indirectly via a TNF-alpha-dependent mechanism. At the early time points, CD40LT directly stimulated beta-chemokine production, whereas at later time points the effect was mediated to some extent by TNF-alpha. In conclusion, our results suggest that CD40-CD40L interactions are important for the activation of monocyte-derived macrophage antiviral response affecting both viral replication and the recruitment of immune cells.

YY1 Transcription Factor Down-regulates Expression of CCR5, a Major Coreceptor for HIV-1

Expression of CCR5, a major coreceptor for human immunodeficiency virus type 1 (HIV-1), is regulated by a number of transcription factors. Here we report that the YY1 transcription factor down-regulates CCR5 promoter activity and that overexpression of YY1 reduces cell surface CCR5 expression and infectibility by R5-HIV-1. Because YY1 also down-regulates promoter activities of CXCR4, another major coreceptor for HIV-1 and HIV-1 long terminal repeat, this transcription factor may play a critical role in the pathogenesis of HIV-1 disease.

Genetic footprinting of the HIV co-receptor CCR5: delineation of surface expression and viral entry determinants

Human immunodeficiency virus type 1 (HIV-1) utilizes CD4 as a primary receptor for viral entry and any of several 7-transmembrane chemokine receptors, including CCR5, as a co-receptor. Previous studies have demonstrated that multiple extracellular domains (ECDs) of CCR5 contribute to co-receptor function; here we applied genetic footprinting to CCR5 to confirm and extend those investigations. In genetic footprinting, a duplex oligonucleotide is inserted into the DNA sequence of interest by use of either a bacterial transposase or retroviral integrase. Here, CCR5 mutants were analyzed in bulk for their ability to be expressed on the recipient cell surface and to mediate viral entry of R5 HIV isolates. Most of the approximately 150 CCR5 mutants were not expressed on the cell surface. Of those remaining, 8 were specifically reduced or absent after macrophage (M)-tropic HIV infection, confirming a critical role of ECDs three (extracellular loop 2 or ECL2) and possibly four (ECL3) in viral entry. Mutational and functional analyses of ECD4 (ECL3) suggest it is under severe topological constraint for CCR5 surface expression and are consistent with it contributing to co-receptor function.

CD1d-restricted natural killer T cells are potent targets for human immunodeficiency virus infection.

Invariant human natural killer T cells (NKT) express a restricted T-cell receptor (TCR) Valpha24Vbeta11 repertoire. These cells share both phenotypic and functional similarities between NK and T cells. Given the emerging role of NKT cells as critical cells in bridging the gap between innate and adaptive immunity, we examined their susceptibility to productive human immunodeficiency virus (HIV) infection by T-tropic, M-tropic, and primary isolates of HIV. We generated three human NKT cell clones (CA5, CA29, and CA31). Phenotypic characterization of these Valpha24+ Vbeta11+ clones indicated that they were predominately positive for CD4, CD161, HLA-DR, CD38, CD45RO, and CD95 expression. The NKT cell clones expressed significantly more surface CCR5 molecules/cell and lower CXCR4 molecules/cell than phytohaemagglutinin-stimulated peripheral blood mononuclear cells (PBMC). Consistent with the surface expression of CCR5 and CXCR4, the NKT clones were also selectively susceptible to HIV M-tropic, T-tropic, and primary isolate infection, as evaluated by both HIV p24 enzyme-linked immunosorbent assay and intracellular staining of HIV proteins. The amount of p24 production was dependent on the NKT clone studied and the HIV strain used. Clones CA29 and CA31 were also susceptible to HIV IIIB infection. The virions produced by these clones were able to productively infect PHA-stimulated PBMCs with the same kinetics as for primary infection of CD4+ blast. Collectively, this data demonstrates that NKT cells can be a target for productive HIV infection but with a lag in the time to peak p24 production.

Human cytomegalovirus infection reduces surface CCR5 expression in human microglial cells, astrocytes and monocyte-derived macrophages

Within the brain, glial cells are target cells for human cytomegalovirus (HCMV) and HIV. We infected cultures of unstimulated human microglial cells and astrocytes of embryonic origin and of monocyte-derived macrophages (MDM) with HCMV strain AD169 and observed down-regulation of the plasma membrane expression of CCR5 in the three cell types, and of CXCR4 and CD4 in microglial cells only. Cells were then coinfected simultaneously or at a 24-h interval with both AD169 and two different HIV-1 monocytotropic strains. HCMV late antigens and HIV-1 tat protein colocalized in the cytoplasm of 5–10% of microglia and MDM. p24 antigen levels decreased 10- to 40-fold in supernatants of MDM and the reduction was greater when HCMV infection was performed 24 h before HIV-1 infection. These data suggest that HCMV-induced reduction in the cell-surface expression of the primary co-receptor of HIV-1 monocytotropic strains may impair the ability of HIV to infect these cells.

MHC class II engagement by its ligand LAG-3 (CD223) leads to a distinct pattern of chemokine and chemokine receptor expression by human dendritic cells

Upon stimulation by infectious agent products, dendritic cells (DC) become activated, express high levels of class I and class II antigens, CD80, CD86 and CD83 and migrate to secondary lymphoid organs where they can prime naive CD4-helper and CD8-cytotoxic T-cells. Cognate CD4 + T-cell help mediated by CD40L along with DC stimulation with another T-cell effector molecule, termed lymphocyte activated gene-3 (LAG-3 or CD223, a ligand for MHC class II) have been shown to induce this maturation process. Both CD40L and LAG-3 have been used as vaccine adjuvants to induce CTL and CD4 Th1 responses. Here, we studied the effect of a soluble LAG-3Ig molecule on the chemokine and chemokine receptor profile of human immature monocyte-derived DC. LAG-3Ig, unlike CD40L, induced an inflammatory signal in terms of IL-8 and MIP-1α/CCL3 production and, in contrast to LPS, induced production of chemokines (MDC/CCL22 and TARC/CCL17) known to direct the migration of maturing DC to lymph nodes. In LAG-3-matured DC, surface expression of CCR5 (a receptor for MIP-1α/CCL3) was down-regulated and CCR7 (a receptor for MIP-3β and SLC) was up-regulated. However, LAG-3-matured, but not LPS- or CD40L-matured DC retained their capacity to migrate in chemotaxis chambers and to respond to MIP-1α. Altogether, these data represent the first evidence that MHC class II signaling may affect DC migration to secondary lymphoid tissues.

Expression of chemokine receptors in the different clinical forms of multiple sclerosis.

Chemokines and their receptors are important in the trafficking of peripheral leukocytes into the central nervous system, a major event in the pathogenesis of multiple sderosis (MS). Evidence based on clinical, pathological and magnetic resonance imaging grounds supports some divergence between forms of MS with relapses [relapsing-remitting (RR) and secondary progressive (SP)] and the primary progressive (PP) form. To elucidate whether different pathogenic mechanisms are involved in PPMS, we compared membrane expression of a group of CC and CXC chemokine receptors (CCR1, CCR5, CXCR3, CXCR4) in peripheral blood of 68 MS patients (25 PPMS, 23 SPMS and 20 RRMS) and 26 healthy controls. We found a significant increase in surface expression of CCR5 in CD4+, CD8+, CD19+ and CD14+ cells as well as an increased percentage of CXCR3 and CXCR4 in CD14+ cells in MS patients compared to controls. Increased levels of CXCL10 (IP-10) and CCL5 (RANTES) in cerebrospinal fluid were also observed in a subgroup of MS patients. These results support that chemokines and their receptors are involved in the pathogenesis of MS However, a pattem of chemokine-chemokine receptor expression characteristic of each clinical form of the disease failed to be observed.

IFN-γ and IL-12 differentially regulate CC-chemokine secretion and CCR5 expression in human T lymphocytes

Interleukin (IL)-12, especially in the presence of neutralizing anti-IL-4 monoclonal antibodies, primed CD45RO(-) T clones for high CCL3/macrophage-inflammatory protein-1alpha (MIP-1alpha) and CCL4/MIP-1beta levels. In CD4(+) and CD8(+) clones from two patients deficient for IL-12Rbeta1 (IL-12Rbeta1(-/-)), production of CCL3/MIP-1alpha and CCL4/MIP-1beta was defective. CD4(+) clones from two patients deficient for interferon-gamma (IFN-gamma) R1 (IFN-gammaR1(-/-)) produced somewhat decreased CCL4/MIP-1beta levels. IL-12 failed to prime CD4(+) or CD8(+) healthy clones for high CCL5/regulated on activation, normal T expressed and secreted (RANTES) production, although its secretion was impaired in CD4(+) clones from IL-12Rbeta1(-/-) and IFN-gammaR1(-/-) patients. CCR5 surface expression was up-regulated in resting peripheral blood mononuclear cells and CD4(+) clones from both kinds of patients, rendering them more susceptible to CCR5-dependent (R5) HIV-1 infection. Neutralization of IFN-gamma increased CCR5 expression and decreased CC-chemokine secretion by CD4(+) clones from healthy and IL-12Rbeta1(-/-) individuals, suggesting an IFN-gamma-dependent control of CCR5 expression. These data provide the first documented analysis of chemokine secretion and chemokine receptor expression on T cells from IL-12 and IFN-gamma receptor-deficient patients and dissect the role of IL-12 and IFN-gamma on inducing inflammatory chemokine secretion and down-regulating CCR5 expression in human T cells.

Prostaglandin E2 is a key factor for CCR7 surface expression and migration of monocyte-derived dendritic cells

Dendritic cells (DCs) are potent antigen-presenting cells that are able to initiate and modulate immune responses and are hence exploited as cellular vaccines for immunotherapy. Their capacity to migrate from peripheral tissues to the T-cell areas of draining lymph nodes is crucial for the priming of T lymphocytes. In this study, we investigated how the maturation of human monocyte-derived DCs (MoDCs) by several different stimuli under serum-free conditions affected their T-cell stimulatory function, cytokine secretion, and migratory behavior. Surprisingly, we found that for all maturation stimuli tested, the addition of prostaglandin E2 (PGE2) was required for effective migration of MoDCs toward the lymph node-derived chemokines CCL19 (EBI1 ligand chemokine/macrophage inflammatory protein--3beta) and CCL21 (secondary lymphoid tissue chemokine [SLC]/6Ckine). Costimulation with PGE2 enhanced the expression of the CCL19/CCL21 receptor CCR7 on the cell surface of MoDCs when they were matured with soluble CD40 ligand or proinflammatory cytokines, but did not affect CCR7 expression of polyI:C-stimulated MoDCs. The effects of PGE2 on MoDCs were mediated through increased cyclic adenosine monophosphate by 2 of the known PGE2 receptors, EP2 and EP4, which are expressed and down-regulated after PGE2 binding in these cells. In conclusion, our results suggest that signals provided by the proinflammatory mediator PGE2 are crucial for MoDCs to acquire potent T-helper cell stimulatory capacity and substantial chemotactic responsiveness to lymph node-derived chemokines. This is a new and important parameter for the preparation of MoDCs as cellular vaccines in tumor immunotherapy. (Blood. 2002;100:1354-1361)

Natural Truncation of the Chemokine MIP-1β/CCL4 Affects Receptor Specificity but Not Anti-HIV-1 Activity

Activated lymphocytes synthesize and secrete substantial amounts of the beta-chemokines macrophage inflammatory protein (MIP)-1 alpha/CCL3 and MIP-1 beta/CCL4, both of which inhibit infection of cells with human immunodeficiency virus type 1 (HIV-1). The native form of MIP-1 beta secreted by activated human peripheral blood lymphocytes (MIP-1 beta(3-69)) lacks the two NH(2)-terminal amino acids of the full-length protein. This truncated form of MIP-1 beta has now been affinity-purified from the culture supernatant of such cells, and its structure has been confirmed by mass spectrometry. Functional studies of the purified protein revealed that MIP-1 beta(3-69) retains the abilities to induce down-modulation of surface expression of the chemokine receptor CCR5 and to inhibit the CCR5-mediated entry of HIV-1 in T cells. Characterization of the chemokine receptor specificity of MIP-1 beta(3-69) showed that the truncated protein not only shares the ability of intact MIP-1 beta to induce Ca(2+) signaling through CCR5, but unlike the full-length protein, it also triggers a Ca(2+) response via CCR1 and CCR2b. These results demonstrate that NH(2)-terminally truncated MIP-1 beta functions as a chemokine agonist with expanded receptor reactivity, which may represent an important mechanism for regulation of immune cell recruitment during inflammatory and antiviral responses.

Functional expression of the lymphoid chemokines CCL19 (ELC) and CCL 21 (SLC) at the blood-brain barrier suggests their involvement in G-protein-dependent lymphocyte recruitment into the central nervous system during experimental autoimmune encephalomyelitis.

Migration of autoaggressive T cells across the blood-brain barrier (BBB) is critically involved in the initiation of experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis. The direct involvement of chemokines in this process was suggested by our recent observation that G-protein-mediated signaling is required to promote adhesion strengthening of encephalitogenic T cells on BBB endothelium in vivo. To search for chemokines present at the BBB, we performed in situ hybridizations and immunohistochemistry and found expression of the lymphoid chemokines CCL19/ELC and CCL21/SLC in venules surrounded by inflammatory cells. Their expression was paralleled by the presence of their common receptor CCR7 in inflammatory cells in brain and spinal cord sections of mice afflicted with EAE. Encephalitogenic T cells showed surface expression of CCR7 and the alternative receptor for CCL21, CXCR3. They specifically chemotaxed towards both CCL19 or CCL21 in a concentration dependent and pertussis toxin-sensitive manner comparable to naive lymphocytes in vitro. Binding assays on frozen sections of EAE brains demonstrated a functional involvement of CCL19 and CCL21 in adhesion strengthening of encephalitogenic T lymphocytes to inflamed venules in the brain. Taken together our data suggest that the lymphoid chemokines CCL19 and CCL21 besides regulating lymphocyte homing to secondary lymphoid tissue are involved in T lymphocyte migration into the immunoprivileged central nervous system during immunosurveillance and chronic inflammation.

Lentiviral transduction of human T-lymphocytes with a RANTES intrakine inhibits human immunodeficiency virus type 1 infection.

Intrakines, modified intracellular chemokines, offer a novel strategy to prevent cellular entry of HIV-1 by blocking the surface expression of HIV-1 co-receptors. To investigate potential clinical applications of the RANTES-intrakine, we explored the use of HIV-1-based lentiviral vectors for therapeutic gene transfer into T-lymphocytes. RANTES-intrakine genes can be efficiently transduced into primary human T-lymphocytes by lentiviral vectors, especially when human T-lymphocytes were stimulated with CD3 and CD28 antibodies. The transduced T cells showed decreased surface expression of the chemokine receptor CCR-5, as well as CCR-1 and CCR-3. This lentivirus-mediated approach to intrakine gene transfer protected human T-lymphocytes from infection by a variety of R5-tropic HIV-1 strains. A quantitative real-time PCR assay, developed to monitor cells for HIV entry and persistence, revealed persistent low copy numbers of proviral HIV DNA in RANTES intrakine-transduced T-lymphocytes during 3-week culture, suggesting that viruses produced from infected untransduced cell populations were unable to infect the surrounding transduced T-lymphocytes. We conclude that targeting HIV-1 co-receptors to block virus entry with lentiviral vectors is an attractive approach to the control of HIV-1 infection.

Reduced CC chemokine receptor (CCR) 1 and CCR5 surface expression on peripheral blood T lymphocytes from patients with chronic hepatitis C infection.

T cell recruitment to the infected liver is an essential step for the efficient elimination of hepatitis viruses. The surface expression of CC chemokine receptor (CCR) 1, CCR4, and CCR5 on peripheral blood T lymphocytes and their responsiveness to the chemokines macrophage inflammatory proteins (MIP)-1alpha, MIP-1beta, and RANTES (regulated on activation, normally T cell-expressed and secreted) was analyzed in patients with chronic hepatitis C and hepatitis B infection and compared with healthy subjects. Although CCR4 surface expression was not altered, hepatitis C virus (HCV)-infected patients had lower proportions of CD8 T cells with CCR1 and CCR5 surface expression (P<.05). Migration of CD8 T cells in response to MIP-1alpha, MIP-1beta, and RANTES was significantly reduced in HCV-infected patients (P<.05). Intracellular CCR1 and CCR5 protein and messenger RNA levels in peripheral blood T cells did not indicate reduced chemokine receptor biosynthesis in hepatitis C infection. Thus, chronic hepatitis C, but not hepatitis B, infection alters surface expression of distinct CCRs, resulting in lower CC chemokine responsiveness.