Blocking the CC chemokine receptor 5 pathway by antisense peptide nucleic acid prolongs islet allograft survival

Chemokines are important regulators in the development, differentiation, and anatomic location of leukocytes. The CC chemokine receptor 5 (CCR5) is the receptor for the proinflammatory chemokines and plays an important role in islet allograft rejection. Peptide nucleic acid (PNA) is a nucleic acid analog in which the sugar phosphate backbone of natural nucleic acid has been replaced by a synthetic peptide backbone. Studies indicate that PNA inhibits both transcription and translation of targeted genes. Fullly major histocompatibility complex (MHC)-mismatched murine islet transplant models were used to test the in vivo effect of PNA CCR5 by targeting CCR5 in acute allograft rejection. PNA CCR5-treated recipients demonstrated significant prolongation (12.0 +/- 1.75 days) of functional allograft survival compared with saline (6.5 +/- 0.58 days)- or PNA mismatch-treated recipients (6.5 +/- 0.50 days). The PNA CCR5 blocked the expression of CCR5 in spleen CD3+ T cells. Lymphocytes from PNA CCR5-treated mice exhibited a reduced degree of proliferation comparable to that of saline- and PNA mismatch-treated mice. The present study indicated that PNA CCR5 has a substantial therapeutic effect to inhibit acute allograft rejection.

Met-RANTES ameliorates fibrous airway obliteration and decreases ERK expression in a murine model of bronchiolitis obliterans

OBJECTIVES

Bronchiolitis obliterans (BO) is the main cause of late mortality among long-term survivors of lung transplantation. Chemokine-chemokine receptor (CCR) interaction and subsequent recruitment of infiltrating cells to the graft are early events in the development of chronic rejection of transplanted lungs. The present study investigated whether blockade of chemokine receptors CCR1 and CCR5 with Met-regulated-on-activation, normal T cells expressed and secreted (RANTES), an amino-terminal modified derivative of RANTES/CCL5, affects the development of BO in murine model and we sought to determine the expression of RANTES/CCL5 and their relationship with extracellular signal-regulated kinase (ERK).

MATERIALS AND METHODS

BALB/c mouse tracheas were heterotopically transplanted into C57Black6 recipients and treated for 21 days with either Met-RANTES at 20 microg/day or vehicle. Animals were killed at 21 days after transplantation for histologic examination of ERK expression.

RESULTS

RANTES/CCL5 was highly expressed in allografts compare to isografts. Met-RANTES treatment ameliorated fibrous airway obliteration in a mouse model of BO and decreased ERK expression.

CONCLUSION

Blockade of chemokine receptors by Met-RANTES ameliorated airway obliteration and decreased ERK expression. These findings suggest that chemokine receptors CCR1 and CCR5 play significant roles in the development of chronic rejection and ERK may be a new molecular target for chronic rejection.

Monocyte subsets differentially employ CCR2, CCR5, and CX3CR1 to accumulate within atherosclerotic plaques

Monocytes participate critically in atherosclerosis. There are 2 major subsets expressing different chemokine receptor patterns: CCR2(+)CX3CR1(+)Ly-6C(hi) and CCR2(-)CX3CR1(++)Ly-6C(lo) monocytes. Both C-C motif chemokine receptor 2 (CCR2) and C-X(3)-C motif chemokine receptor 1 (CX3CR1) are linked to progression of atherosclerotic plaques. Here, we analyzed mouse monocyte subsets in apoE-deficient mice and traced their differentiation and chemokine receptor usage as they accumulated within atherosclerotic plaques. Blood monocyte counts were elevated in apoE(-/-) mice and skewed toward an increased frequency of CCR2(+)Ly-6C(hi) monocytes in apoE(-/-) mice fed a high-fat diet. CCR2(+)Ly-6C(hi) monocytes efficiently accumulated in plaques, whereas CCR2(-)Ly-6C(lo) monocytes entered less frequently but were more prone to developing into plaque cells expressing the dendritic cell-associated marker CD11c, indicating that phagocyte heterogeneity in plaques is linked to distinct types of entering monocytes. CCR2(-) monocytes did not rely on CX3CR1 to enter plaques. Instead, they were partially dependent upon CCR5, which they selectively upregulated in apoE(-/-) mice. By comparison, CCR2(+)Ly-6C(hi) monocytes unexpectedly required CX3CR1 in addition to CCR2 and CCR5 to accumulate within plaques. In many other inflammatory settings, these monocytes utilize CCR2, but not CX3CR1, for trafficking. Thus, antagonizing CX3CR1 may be effective therapeutically in ameliorating CCR2(+) monocyte recruitment to plaques without impairing their CCR2-dependent responses to inflammation overall.

Trypanosoma cruzi-triggered meningoencephalitis is a CCR1/CCR5-independent inflammatory process

Encephalitis rarely occurs during acute Trypanosoma cruzi infection. However, the central nervous system (CNS) is the major site of infection reactivation in immunocompromised patients. We show that the acute T. cruzi-triggered CD8-enriched meningoencephalitis paralleled the in situ expression of CCL3/MIP-1alpha and CCL5/RANTES mRNA. The frequency of CCR5-bearing cells was increased among peripheral blood mononuclear cells (PBMC) of infected mice. Further, CCL5/RANTES-driven in vitro PBMC migration was partially abrogated by the CCR1/CCR5 antagonist Met-RANTES. However, Met-RANTES treatment of infected mice altered neither parasitism nor intensity and nature of the CNS inflammation, indicating that T. cruzi-elicited meningoencephalitis is a CCR1/CCR5 independent process.

Structural basis for coreceptor selectivity by the HIV type 1 V3 loop

The third variable region (V3) of the HIV-1 surface glycoprotein, gp120, plays a central role in the interaction of the virus envelope with the cell surface chemokine receptors, triggering membrane fusion and virus entry into human lymphocytes and macrophages. The CXCR4 and CCR5 chemokine receptors are used by "X4-tropic" and "R5-tropic" viruses, respectively. Recently, the crown of the V3 loop was shown to bear a close structural homology to the beta2-beta3 loop in the CXC and CC chemokines, the natural ligands of CXCR4 and CCR5, respectively. This homology can serve as the foundation for 3D molecular modeling of the V3 loops from primary isolates whose coreceptor usage was experimentally defined. The modeling revealed a charged "patch" on the surface of V3 that correlates with coreceptor usage. This V3 surface patch is positively charged in X4-tropic viruses and negatively charged or neutral in R5-tropic viruses, and is formed by two amino acids, at position 11 and at position 24 or 25; amino acids 11 and 24 or 11 and 25 contact each other in 3D space. Residues at positions 11 and 25 were known previously to influence coreceptor usage, and the charge of the residues at these two positions is often used to predict viral tropism. However, we found that the predictive value of using the charge of residues 11, 24, and 25 to identify X4 or R5 tropism was improved over using only the charge of residues 11 and 25. Thus, the data suggest a new " 11/24/25 rule" : a positively charged amino acid at position 11, 24, or 25 defines X4; otherwise R5. This rule gave an overall predictive value of 94% for 217 viruses whose tropism had been determined experimentally as either X4 or R5. The results have additional implications for the design of HIV therapeutics, vaccines, and strategies for monitoring disease progression.

The envelope gene is a cytopathic determinant of CCR5 tropic HIV-1

Late stage AIDS associated CCR5 tropic HIV-1 clones (R5-AIDS HIV-1) exhibit greater cytopathic effects (CPE) than earlier isolates from the same patients. In this study, envelopes from a series of three biological clones derived from the same patient were evaluated as a cytopathic determinant of R5-AIDS HIV-1 for thymocytes. In a single round of replication in thymocytes, the AIDS associated clone mediated greater initiation of reverse transcription. This enhancement was not due to broadened coreceptor tropism, as all clones studied were exclusively R5 tropic. The full-length R5-AIDS env mediated greater infectivity than R5 pre-AIDS env when used to pseudotype a reporter virus. R5-AIDS env pseudotypes were more resistant to TAK-779 and showed more rapid infection kinetics but similar resistance to a CD4 blocking mAb. We conclude that the enhanced thymic replication and CPE shown by the R5-AIDS clone is due to enhanced efficiency of Env-mediated entry via CCR5.

Novel inhibitors of the early steps of the HIV-1 life cycle

Considerable advances have been made on compounds that are active as inhibitors of HIV entry and fusion. The discovery of chemokines a few years ago focused the attention on coreceptor inhibitors in addition to fusion and attachment blockers. During the last 5 years, there has been an intense research activity from both private companies and academic institutions to find effective compounds that are capable of inhibiting the initial steps in the HIV life cycle. Some of the presented compounds demonstrated in vitro synergism, thus there is the rationale of their combined use in HIV-infected individuals. Many entry and fusion inhibitors of HIV are being investigated in controlled clinical trials and there are a number of them that are bioavailable as oral formulations. This is an essential feature for an extended use of these compounds with the purpose of ameliorating patients' adherence to medications; therefore, preventing the development of drug resistance. Among the many compounds that are being investigated, some are in the preclinical arena and others are more advanced in development stages. Overall, the main aim is to establish the action of these compounds on the immune system (e.g., the balance of the system after shutting off CCR5 or CXCR4 coreceptors) and the possible burden of unexplained side effects. This review focuses on the recent developments in this field with a particular attention on promising compounds in preclinical and clinical trials.

HIV-1 gp120 compromises blood-brain barrier integrity and enhances monocyte migration across blood-brain barrier: implication for viral neuropathogenesis

Human immunodeficiency virus-1 (HIV-1) encephalitis is characterized by brain infiltration of virus-infected monocytes and macrophages. Cellular products and viral proteins secreted by infected cells likely play an important role in blood-brain barrier (BBB) impairment and the development of HIV-1-associated dementia (HAD). We previously demonstrated that HIV-1 envelope glycoprotein gp120 induces toxicity and alters expression of tight junction proteins in human brain microvascular endothelial cells (HBMECs). Here, we delineate the mechanisms of gp120-induced BBB dysfunction. Human brain microvascular endothelial cells expressed HIV-1 co-receptors (CCR5 and CXCR4). Exposure of HBMECs to gp120 derived from macrophage (CCR5) or lymphocyte (CXCR4)-tropic viruses decreased BBB tightness, increased permeability, and enhanced monocyte migration across in vitro BBB models. Blood-brain barrier integrity was restored after gp120 removal. CCR5 antibodies and inhibitors of myosin light chain kinase or protein kinase C (PKC) blocked gp120-enhanced monocyte migration and permeability of BBB in vitro. Exposure of HBMECs to gp120 induced release of intracellular calcium ([Ca(2+)](i)) that was prevented by CCR5 antibody and partially blocked by CXCR4 antagonist. Human immunodeficiency virus-1 gp120 activated three PKC isoforms in HBMECs [PKC-alpha/betaII, PKC(pan)-betaII and PKC-zeta/lambda]. Furthermore, specific PKC inhibitors (acting at the ATP-binding and calcium release site) blocked gp120-induced PKC activation and prevented increase in BBB permeability, supporting the biologic significance of these results. Thus, gp120 can cause dysfunction of BBB via PKC pathways and receptor mediated [Ca(2+)](i) release leading to cytoskeletal alterations and increased monocyte migration.

Development and characterization of a novel single-cycle recombinant-virus assay to determine human immunodeficiency virus type 1 coreceptor tropism

Most human immunodeficiency virus type 1 (HIV-1) strains require either the CXCR4 or CCR5 chemokine receptor to efficiently enter cells. Blocking viral binding to these coreceptors is an attractive therapeutic target. Currently, several coreceptor antagonists are being evaluated in clinical trials that require characterization of coreceptor tropism for enrollment. In this report, we describe the development of an automated and accurate procedure for determining HIV-1 coreceptor tropism (Trofile) and its validation for routine laboratory testing. HIV-1 pseudoviruses are generated using full-length env genes derived from patient virus populations. Coreceptor tropism is determined by measuring the abilities of these pseudovirus populations to efficiently infect CD4+/U87 cells expressing either the CXCR4 or CCR5 coreceptor. Viruses exclusively and efficiently infecting CXCR4+/CD4+/U87 cells are designated X4-tropic. Conversely, viruses exclusively and efficiently infecting CCR5+/CD4+/U87 cells are designated R5-tropic. Viruses capable of infecting both CXCR4+/CD4+/U87 and CCR5+/CD4+/U87 cells are designated dual/mixed-tropic. Assay accuracy and reproducibility were established by evaluating the tropisms of well-characterized viruses and the variability among replicate results from samples tested repeatedly. The viral subtype, hepatitis B virus or hepatitis C virus coinfection, and the plasma viral load did not affect assay performance. Minority subpopulations with alternate tropisms were reliably detected when present at 5 to 10%. The plasma viral load above which samples can be amplified efficiently in the Trofile assay is 1,000 copies per ml of plasma. Trofile has been automated for high-throughput use; it can be used to identify patients most likely to benefit from treatment regimens that include a coreceptor inhibitor and to monitor patients on treatment for the emergence of resistant virus populations that switch coreceptor tropism.

Role of CCR1 and CCR5 in homing and growth of multiple myeloma and in the development of osteolytic lesions: a study in the 5TMM model

Multiple myeloma (MM) is a plasma cell malignancy, characterized by the localization of the MM cells in the bone marrow (BM), where they proliferate and induce osteolysis. The MM cells first need to home or migrate to the BM to receive necessary survival signals. In this work, we studied the role of CCR1 and CCR5, two known chemokine receptors, in both chemotaxis and osteolysis in the experimental 5TMM mouse model. A CCR1-specific (BX471) and a CCR5-specific (TAK779) antagonist were used to identify the function of both receptors. We could detect by RT-PCR and flow cytometric analyses the expression of both CCR1 and CCR5 on the cells and their major ligand, macrophage inflammatory protein 1alpha (MIP1alpha) could be detected by ELISA. In vitro migration assays showed that MIP1alpha induced a 2-fold increase in migration of 5TMM cells, which could only be blocked by TAK779. In vivo homing kinetics showed a 30% inhibition in BM homing when 5TMM cells were pre-treated with TAK779. We found, in vitro, that both inhibitors were able to reduce osteoclastogenesis and osteoclastic resorption. In vivo end-term treatment of 5T2MM mice with BX471 resulted in a reduction of the osteolytic lesions by 40%; while TAK779 treatment led to a 20% decrease in lesions. Furthermore, assessment of the microvessel density demonstrated a role for both receptors in MM induced angiogenesis. These data demonstrate the differential role of CCR1 and CCR5 in MM chemotaxis and MM associated osteolysis and angiogenesis.

Genetic protection against hepatitis B virus conferred by CCR5Delta32: Evidence that CCR5 contributes to viral persistence

Recovery from acute hepatitis B virus (HBV) infection requires a broad, vigorous T-cell response, which is enhanced in mice when chemokine receptor 5 (CCR5) is missing. To test the hypothesis that production of a nonfunctional CCR5 (CCR5Delta32 [a functionally null allele containing a 32-bp deletion]) increases the likelihood of recovery from hepatitis B in humans, we studied 526 persons from three cohorts in which one person with HBV persistence was matched to two persons who recovered from an HBV infection. Recovery or persistence was determined prior to availability of lamivudine. We determined genotypes for CCR5Delta32 and for polymorphisms in the CCR5 promoter and in coding regions of the neighboring genes, chemokine receptor 2 (CCR2) and chemokine receptor-like 2 (CCRL2). Allele and haplotype frequencies were compared among the 190 persons with viral recovery and the 336 with persistence by use of conditional logistic regression. CCR5Delta32 reduced the risk of developing a persistent HBV infection by nearly half (odds ratio [OR], 0.53; 95% confidence interval [CI], 0.33 to 0.83; P = 0.006). This association was virtually identical in persons with and without a concomitant human immunodeficiency virus infection. Of the nine individuals who were homozygous for the deletion, eight recovered from infection (OR, 0.25; 95% CI, 0.03 to 1.99; P = 0.19). None of the other neighboring polymorphisms examined were associated with HBV outcome. These data demonstrate a protective effect of CCR5Delta32 in recovery from an HBV infection, provide genetic epidemiological evidence for a role of CCR5 in the immune response to HBV, and suggest a potential therapeutic treatment for patients persistently infected with HBV.

Polymorphisms in CCL2&CCL5 chemokines/chemokine receptors genes and their association with diseases

BACKGROUND

Chemokines and chemokine receptors are major mediators of leukocyte trafficking into the sites of the immune response. They participate in defence against microbial infection, in Th1/Th2 polarization of the immune response, allograft rejection and angiogenesis/angiostasis as well as in tumorigenesis and metastasis. To date, several functional polymorphisms of chemokine and chemokine receptor genes have been discovered that are able to deregulate chemokine system and, therefore, they may interfere with the pathogenesis of a large number of inflammatory and other diseases. In this review we focus on the known polymorphisms of two chemokines: CCL2, CCL5 and their corresponding receptors (CCR2, CCR5) and we also discuss their associations with susceptibility and progression to selected immune-mediated diseases.

METHODS AND RESULTS

Based on relevant literature this article gives a short overview of case-control and family studies regarding effect of the genetic factors on diseases such as coronary artery disease, systemic lupus erythematosus, diabetes mellitus, lung diseases and others.

CONCLUSION

Recent advance in the identification of chemokine genetic background of the diseases could provide opportunity for pharmacological treatment. However, we need more information about posttranscriptional events to understand functional relevance of polymorphisms and to discovery new avenues to blocking disease development.

Dendritic cell stimulation by mycobacterial Hsp70 is mediated through CCR5

An effective host immune response to mycobacterial infection must control pathogen dissemination without inducing immunopathology. Constitutive overexpression of mycobacterial heat shock protein (myHsp70) is associated with impaired bacterial persistence, but the immune-mediated mechanisms are unknown. We found that myHsp70, in addition to enhancing antigen delivery to human dendritic cells, signaled through the CCR5 chemokine receptor, promoting dendritic cell aggregation, immune synapse formation between dendritic cells and T cells, and the generation of effector immune responses. Thus, CCR5 acts as a pattern-recognition receptor for myHsp70, which may have implications for both the pathophysiology of tuberculosis and the use of myHsps in tumor-directed immunotherapy.

Cell-free human immunodeficiency virus type 1 transcytosis through primary genital epithelial cells

Although the transport of human immunodeficiency virus type 1 (HIV-1) through the epithelium is critical for HIV-1 colonization, the mechanisms controlling this process remain obscure. In the present study, we investigated the transcellular migration of HIV-1 as a cell-free virus through primary genital epithelial cells (PGECs). The absence of CD4 on PGECs implicates an unusual entry pathway for HIV-1. We found that syndecans are abundantly expressed on PGECs and promote the initial attachment and subsequent entry of HIV-1 through PGECs. Although CXCR4 and CCR5 do not contribute to HIV-1 attachment, they enhance viral entry and transcytosis through PGECs. Importantly, HIV-1 exploits both syndecans and chemokine receptors to ensure successful cell-free transport through the genital epithelium. HIV-1-syndecan interactions rely on specific residues in the V3 of gp120 and specific sulfations within syndecans. We found no obvious correlation between coreceptor usage and the capacity of the virus to transcytose. Since viruses isolated after sexual transmission are mainly R5 viruses, this suggests that the properties conferring virus replication after transmission are distinct from those conferring cell-free virus transcytosis through the genital epithelium. Although we found that cell-free HIV-1 crosses PGECs as infectious particles, the efficiency of transcytosis is extremely poor (less than 0.02% of the initial inoculum). This demonstrates that the genital epithelium serves as a major barrier against HIV-1. Although one cannot exclude the possibility that limited passage of cell-free HIV-1 transcytosis through an intact genital epithelium occurs in vivo, it is likely that the establishment of infection via cell-free HIV-1 transmigration is a rare event.

CCR5-dependent homing of naturally occurring CD4+ regulatory T cells to sites of Leishmania major infection favors pathogen persistence

Pathogen persistence after clinical cure is a hallmark of many chronic infections. Previously, we showed that naturally occurring CD4+CD25+ regulatory T (nTreg) cells rapidly accumulate within chronic dermal sites of Leishmania major infection where they suppress anti-pathogen CD4+ T cell responses, favor parasite persistence and dermal pathology, and consequently control concomitant immunity. Here, we postulated that chemokines might direct nTreg cell homing in sites of infection and show that CD4+CD25+ nTreg cells, compared with normal CD4+ T cells, preferentially express the CCR5 chemokine receptor, which enables them to migrate in response to CCR5 ligands in vitro. We show that in contrast to their wild-type (WT) counterparts, CCR5-/- CD4+CD25+ nTreg cells resulted in an increased magnitude of parasite-specific, interferon gamma-producing CD4+ T cells within infection sites, dramatically reduced parasite numbers, and potent resistance to infection, a finding consistent with the clinical outcome of infected CCR5-/- mice. Interestingly, this resistance was related to an inefficient migration of CCR5-/- nTreg cells to infected dermal sites compared with WT nTreg cells. Thus, this study shows that CCR5 directs the homing of CD4+CD25+ nTreg cells to L. major-infected dermal sites where they promote the establishment of infection and long-term survival of the parasite in the immune host.

[Relationship between CCR5 and acute graft-versus-host disease in murine bone marrow transplantation]

This study was aimed to eveluate the role of CCR5 on donor cells in recipient models received intensive conditioning, so as provide the scientific evidence for clinical application of allo-HSCT. Lethally irradiated BALB/c mice received allogeneic bone marrow transplants from C57BL/6 mice. Mice divided into 4 groups according to receiving variant donor cells: B6 CCR5 KO group, receiving C57BL/6 CCR5(-/-) mice bone marrow cells and splenocytes; B6 WT BMC group, receiving C57BL/6 mice bone marrow cells and splenocytes; B6 CCR5 KO BMC group, receiving C57BL/6 CCR5(-/-) bone marrow cells alone; B6 WT BMC group, receiving C57BL/6 mice bone marrow cells alone. The result showed that compared to B6 WT BMC group, B6 CCR5 KO group succumbed to acute GVHD at an accelerated rate. Donor CD8(+) T cells expanded to a significantly greater extent in recipients of CCR5 KO, compared with B6 WT control cells. T cells recovered from recipients of CCR5 KO cells produced more IFN-gamma and TNF-alpha and proliferated to a T-cell at a significantly higher level than T cells from recipients of WT cells, indicating that CCR5 plays a role in downregualting donor alloreative CD8(+) T-cells expansion. Histological assessment of the mice indicated pathological lesions in the kidneys and a greater degree of liver pathological changes in mice that received CCR5 KO donor grafts. It is concluded that the knock-out of CCR5 on donor cells results in increase of GVHD and donor CD8(+) T cell expansion, as well as hepatic and renal lesions in allo-HSCT, which indicates that CCR5 is very important in allo-BMT.

Long-term changes of serum chemokine levels in vaccinated military personnel

BACKGROUND

Members of the United States Armed Forces receive a series of vaccinations during their course of service. To investigate the influence of multiple vaccinations on innate immunity, we measured concentrations of a panel of immunomodulatory and pro-inflammatory cytokines in serum samples from a group of such individuals.

RESULTS

Significantly increased levels of macrophage inflammatory protein 1alpha (MIP-1alpha), MIP-1beta and interleukin 8 (IL-8) were detected. Since these cytokines are known to have anti-human immunodeficiency virus (HIV) activity, we tested the effect of serum from these individuals on HIV-1 infectivity and susceptibility of their peripheral blood mononuclear cells (PBMCs) to HIV-1 infection in vitro. Sera from vaccinated military personnel inhibited, and their PBMCs were partially resistant to, infection by HIV-1 strains tropic to CCR5 (R5), but not to CXCR4 (X4), chemokine receptor.

CONCLUSION

These findings demonstrate that increased anti-HIV chemokines can be detected in vaccine recipients up to 68 weeks following immunization.

Diverse signalling by different chemokines through the chemokine receptor CCR5

We have investigated the signalling properties of the chemokine receptor, CCR5, using several assays for agonism: stimulation of changes in intracellular Ca(2+) or CCR5 internalisation in CHO cells expressing CCR5 or stimulation of [(35)S]GTPgammaS binding in membranes of CHO cells expressing CCR5. Four isoforms of the chemokine CCL3 with different amino termini (CCL3, CCL3(2-70), CCL3(5-70), CCL3L1) were tested in these assays in order to probe structure/activity relationships. Each isoform exhibited agonism. The pattern of agonism (potency, maximal effect) was different in the three assays, although the rank order was the same with CCL3L1 being the most potent and efficacious. The data show that the amino terminus of the chemokine is important for signalling. A proline at position 2 (CCL3L1) provides for high potency and efficacy but the isoform with a serine at position 2 (CCL3(2-70)) is as efficacious in some assays showing that the proline is not the only determinant of high efficacy. We also increased the sensitivity of CCR5 signalling by treating cells with sodium butyrate, thus increasing the receptor/G protein ratio. This allowed the detection of a change in intracellular Ca(2+) after treatment with CCL7 and Met-RANTES showing that these ligands possess measurable but low efficacy. This study therefore shows that sodium butyrate treatment increases the sensitivity of signalling assays and enables the detection of efficacy in ligands previously considered as antagonists. The use of different assay systems, therefore, provides different estimates of efficacy for some ligands at this receptor.

Mechanisms of neuronal injury and death in HIV-1 associated dementia

Infection with the human immunodeficiency virus-1 (HIV-1) and acquired immunodeficiency syndrome (AIDS) remain a persistent and even growing health problem worldwide. Besides its detrimental systemic effects on the immune system, HIV-1 seems to enter the brain very soon after peripheral infection and can induce severe and debilitating neurological problems that include behavioral abnormalities, motor dysfunction and frank dementia. Infected peripheral immune cells, in particular macrophages, appear to infiltrate the CNS and provoke a neuropathological response involving all cell types in the brain. Both viral and host factors, such as the viral strain and the response of the host's immune system, strongly influence the course of HIV-1 disease. Moreover, HIV-1-dependent disease processes in the periphery have a substantial effect on the pathology developing in the central nervous system (CNS), although the brain eventually harbors a distinctive viral population of its own. In the CNS, HIV-1 also initiates activation of chemokine receptors, inflammatory mediators, extracellular matrix-degrading enzymes and glutamate receptor-mediated excitotoxicity, all of which can activate numerous downstream signaling pathways and disturb neuronal and glial function. Although there have been substantial improvements in the control of viral infection in the periphery, an effective therapy for HIV-1 associated dementia (HAD) is still not in sight. This article will review recently identified injurious mechanisms potentially contributing to neuronal death in association with HIV-1 disease and discuss recent and prospective approaches for therapy and prevention of HAD.

Viral evolution in macaques coinfected with CCR5- and CXCR4-tropic SHIVs in the presence or absence of vaccine-elicited anti-CCR5 SHIV neutralizing antibodies

Macaques were immunized with SF162 Env-based gp140 immunogens and challenged simultaneously with the CCR5-tropic homologous SHIV(SF162P4) and the CXCR4-tropic heterologous SHIV(SF33A) viruses. Both mock-immunized and immunized animals became dually infected. Prior immunization preferentially reduced the viral replication of the homologous virus during primary infection but the relative replication of the two coinfecting viruses during chronic infection was unaffected by prior immunization, despite the fact that five of six immunized animals maintained a significantly lower overall viral replication that the control animals. Neutralizing antibodies participated in controlling the replication of SHIV(SF162P4), but not that of SHIV(SF33A). Dual infection resulted in the emergence and predominance within the circulating CCR5 virus pool, of a variant with a distinct neutralization phenotype. The signature of this variant was the presence of three amino acid changes in gp120, two of which were located in the receptor and coreceptor binding sites. Also, a significant fraction of the viruses circulating in the blood, as early as two weeks post-infection, was recombinants and prior immunization did not prevent their emergence. These findings provide new insights into the dynamic interaction of CCR5- and CXCR4-tropic HIV isolates that are potentially relevant in better understanding HIV-mediated pathogenesis.

Mechanisms of HIV-1 neurotropism

Human immunodeficiency virus type 1 (HIV) infects macrophages and microglia in the CNS and frequently causes neurocognitive impairment. Although antiviral therapy generally reduces the viral load in the CNS and improves HIV-associated neurological dysfunction, most current antiviral drugs have poor CNS penetrance and cannot completely suppress viral replication. Furthermore, drug-resistance mutations can evolve independently in the CNS. Thus, a long-lived viral reservoir persists in macrophages and microglia in the brain despite antiviral therapy. This review discusses mechanisms underlying the neurotropism of HIV, focusing on the role of the HIV envelope glycoproteins and their interactions with CD4 and the chemokine receptors CCR5 and CXCR4. We review data from studies of neurotropic HIV derived from the brains of patients with HIV-associated neurocognitive impairment as well as studies of nonhuman primate models. Understanding mechanisms that underlie HIV neurotropism and neurovirulence is critical for development of therapeutics to inhibit CNS infection and preventing neurological injury in HIV-infected individuals.

Analysis of HIV-1-X4 fusion with immature dendritic cells identifies a specific restriction that is independent of CXCR4 levels

Immature dendritic cells (iDCs) are likely to be among the first targets of HIV infection during sexual transmission. We analyzed whether the relatively inefficient viral replication in iDCs could be attributed to specific restrictions during the viral life cycle. Using iDCs from a panel of donors, we set out to compare their capacity to support infection and propagation of X4- and R5-tropic viruses. We also performed quantitative flow cytometry to determine levels of relevant cell-surface CD4 and HIV-1 co-receptors. Although iDCs express comparable levels of functional CXC chemokine receptor 4 (CXCR4) and CC chemokine receptor 5 (CCR5) at the cell surface, they are 100- to 1,000-fold less susceptible to infection by X4- versus R5-tropic HIV-1 strains. Increasing surface expression of CXCR4 by transduction with lentiviral vectors did not lead to increased replication of the X4-tropic strains. Fusion of HIV-X4 with iDCs was markedly less efficient compared to that of HIV-R5. We conclude that an env-specific block early in the viral cycle operates in iDCs. This restriction may play a role in the exclusion of X4-tropic strains during HIV-1 transmission.

CCR5 in T Cell-Mediated Liver Diseases: What’s Going On?

The chemokine receptor CCR5 came into worldwide prominence a decade ago when it was identified as one of the major coreceptors for HIV infectivity. However, subsequent studies suggested an important modulatory role for CCR5 in the inflammatory response. Specifically, CCR5 has been reported to directly regulate T cell function in autoimmune diseases, including multiple sclerosis, rheumatoid arthritis, and type 1 diabetes. Moreover, T cell-mediated immune responses are proposed to be critical in the pathogenesis of autoimmune and viral liver diseases, and recent clinical and experimental studies have also implicated CCR5 in the pathogenesis of autoimmune and viral liver diseases. Therefore, in this brief review, we highlight the evidence that supports an important role of CCR5 in the pathophysiology of T cell-mediated liver diseases with specific emphasis on autoimmune and viral liver diseases.

Cellular entry of HIV: Evaluation of therapeutic targets

In the absence of a vaccine which could stop the HIV/AIDS pandemic, the development of therapeutic options is of utmost interest. The combined use of inhibitors of reverse transcriptase and protease as highly active antiretroviral therapy (HAART) provided the first effective treatment of HIV/AIDS and significantly decreased the number of AIDS related deaths in industrialized countries. However, the emergence of resistant viruses and the toxic side effects of HAART highlights that novel therapies are urgently required. The inhibition of HIV-1 entry is a promising option. Entry of HIV-1 into target cells involves interactions of the viral envelope protein (Env) with CD4 and a coreceptor, usually CCR5 or CXCR4. Env binding to receptor triggers several conformational rearrangements in Env, which involve the creation and/or exposure of structural intermediates pivotal to fusion of the viral and cellular membranes. Both, cellular receptors and structures in Env associated with membrane fusion are targets for therapeutic intervention. Here, we will discuss how HIV-1 enters cells and introduce strategies how this process can be inhibited.

CC-chemokine receptor five gene polymorphism in primary IgA nephropathy: the 32 bp deletion allele is associated with late progression to end-stage renal failure with dialysis

The chemokine (CK) receptor 5 (CCR5) is necessary for two adjacent cysteines (CC)-CKs such as Regulated upon Activation Normal T cell Expressed and Secreted, a/o Macrophage Inflammatory Protein 1alpha/beta to mediate their inflammatory properties. The CCR5 gene polymorphism with 32-basepair deletion (d32) leads to receptor inactivation/dysfunction in homo/heterozygous individuals. We have evaluated its role in both initiation and/or progression of primary immunoglobulin A (IgA) nephropathy (IGAN) in a case-control study involving a prospective cohort of 318 IGAN patients and a matched group of 294 controls. Genotyping was performed by a two-specific primers single polymerase chain reaction technique: normal allele (nl) vs d32 allele. The d32 allele frequency was not different in patients (11.0%) vs controls (8.3%), indicating no significant influence on IGAN initiation. Genotype to clinical phenotype correlation demonstrated that progression to renal/patient death was associated with the d32 allele: 18.2% (12 out of 66 with d32) vs 8.3% (21 out of 252); chi(2)=6.73; P=0.017. The Kaplan-Meier survival without renal/patient death was worse in d32-positive patients (log-rank test; P=0.002). The Cox regression analyses confirmed that the nl/nl genotype was a significant and independent protective factor for progression to end-stage renal failure (ESRF)/dialysis: beta/standard error (s.e.)=-3.1; chi(2)=9.5; relative risk=0.31 (95% confidence interval 0.15-0.65); P=0.002. The d32-CCR5 polymorphism played a significant role in the progression of primary IGAN, with the nl/nl genotype being an independent protective factor for late progression towards ESRF/dialysis. These data raise question about the usefulness of systematic CCR5 genotyping in IGAN patients.

Chemokines and chemokine receptors in HIV infection: role in pathogenesis and therapeutics

Chemokines are known to function as regulatory molecules in leukocyte maturation, traffic, homing of lymphocytes and in the development of lymphoid tissues. Besides these functions in the immune system, certain chemokines and their receptors are involved in HIV pathogenesis. In order to infect a target cell, the HIV envelope glycoprotein gp120 has to interact with the cellular receptor CD-4 and co-receptor, CC or CXC chemokine receptors. Genetic findings have yielded major insights into the in vivo roles of individual co-receptors and their ligands in providing resistance to HIV infection. Mutations in chemokine receptor genes are associated with protection against HIV infections and also involved in delayed progression to AIDS in infected individuals. Blocking of chemokine receptors interrupts HIV infection in vitro and this offers new options for therapeutic strategies. Approaches have been made to study the CCR-5 inhibitors as antiviral therapies and possibly as components of a topical microbicide to prevent HIV-1 sexual transmission. Immune strategies aimed at generating anti-CCR-5 antibodies at the level of the genital mucosa might be feasible and represent a strategy to induce mucosal HIV- protective immunity. It also remains to be seen how these types of agents will act in synergy with existing HIV-1 targeted anti viral or those currently in developments. Beyond providing new perspectives in fundamental aspects of the HIV-1 transmission and pathogenesis, chemokines and their receptors suggest new areas for developing novel therapeutic and preventive strategies against HIV infections. Studies in this review were identified through a search for relevant literature in the pubmed database of the national library of medicine. In this review, some developments in chemokine research with particular focus on their roles in HIV pathogenesis, resistance and therapeutic applications have been discussed.

CCR5: no longer a ‘good for nothing’ gene – chemokine control of West Nile virus infection

The chemokine receptor CCR5 was identified in 1996 as a crucial host factor exploited by HIV for cell entry. CCR5 presumably functions normally in antimicrobial host defense because it generally mediates leukocyte chemotactic responses; however, evidence of antimicrobial functions for CCR5 in humans has been elusive. Recently, genetic analyses in mice and humans have provided strong evidence for the CCR5 control of infection by West Nile virus (WNV), a re-emerging pathogen capable of causing fatal encephalitis. Thus, the same receptor can benefit or harm the host, depending on the virus. Although CCR5 might be a logical target for new drug development in HIV/AIDS, the benefits of blocking CCR5 could carry the cost of an increased risk of WNV disease in co-infected patients.

Modeling the structural basis of human CCR5 chemokine receptor function: from homology model building and molecular dynamics validation to agonist and antagonist docking

This article describes the construction and validation of a three-dimensional model of the human CCR5 receptor using a homology-based approach starting from the X-ray structure of the bovine rhodopsin receptor. The reliability of the model is assessed through molecular dynamics and docking simulations using both natural agonists and a synthetic antagonist. Some important structural and functional features of the receptor cavity and the extracellular loops are identified, in agreement with data available from site-directed mutagenesis. The results of this study help to explain the structural basis for the recognition, activation, and inhibition processes of CCR5 and may provide fresh insights for the design of HIV-1 entry blockers.

CCL5-CCR5-mediated apoptosis in T cells: Requirement for glycosaminoglycan binding and CCL5 aggregation

CCL5 (RANTES (regulated on activation normal T cell expressed and secreted)) and its cognate receptor, CCR5, have been implicated in T cell activation. CCL5 binding to glycosaminoglycans (GAGs) on the cell surface or in extracellular matrix sequesters CCL5, thereby immobilizing CCL5 to provide the directional signal. In two CCR5-expressing human T cell lines, PM1.CCR5 and MOLT4.CCR5, and in human peripheral blood-derived T cells, micromolar concentrations of CCL5 induce apoptosis. CCL5-induced cell death involves the cytosolic release of cytochrome c, the activation of caspase-9 and caspase-3, and poly(ADP-ribose) polymerase cleavage. CCL5-induced apoptosis is CCR5-dependent, since native PM1 and MOLT4 cells lacking CCR5 expression are resistant to CCL5-induced cell death. Furthermore, we implicate tyrosine 339 as a critical residue involved in CCL5-induced apoptosis, since PM1 cells expressing a tyrosine mutant receptor, CCR5Y339F, do not undergo apoptosis. We show that CCL5-CCR5-mediated apoptosis is dependent on cell surface GAG binding. The addition of exogenous heparin and chondroitin sulfate and GAG digestion from the cell surface protect cells from apoptosis. Moreover, the non-GAG binding variant, (44AANA47)-CCL5, fails to induce apoptosis. To address the role of aggregation in CCL5-mediated apoptosis, nonaggregating CCL5 mutant E66S, which forms dimers, and E26A, which form tetramers at micromolar concentrations, were utilized. Unlike native CCL5, the E66S mutant fails to induce apoptosis, suggesting that tetramers are the minimal higher ordered CCL5 aggregates required for CCL5-induced apoptosis. Viewed altogether, these data suggest that CCL5-GAG binding and CCL5 aggregation are important for CCL5 activity in T cells, specifically in the context of CCR5-mediated apoptosis.

CXCR4 and CCR5 mediate homing of primitive bone marrow-derived hematopoietic cells to the postnatal thymus

Factors governing the entry of cells into the postnatal thymus are poorly understood. We aimed to define molecular mechanisms mediating the homing of bone marrow cells to the thymus using a sublethally irradiated in vivo murine model. Entry of unfractionated and lineage-depleted bone marrow cells to the thymus, but not bone marrow, was a Galphai-mediated phenomenon. Lineage-depleted cells that had homed to the thymus expressed abundant CXCR4 and CCR5 mRNA, alone of 17 chemokine receptors evaluated by QPCR. Thymic-homed cells were distinct from cells that had homed to bone marrow in expression of CXCR4 and CCR5 by mRNA quantification and cell-surface expression of protein. Abrogation of CXCR4 and CCR5 function by genetic, antibody, or pharmacologic means impaired homing of lineage-depleted cells to the thymus, although not in a synergistic manner, implying interdependency of these receptors in the homing process. Competitive repopulation experiments demonstrated that inhibiting CXCR4-mediated homing adversely affected the double-negative cell pool at 2 weeks, suggesting that cells with prothymocytic activity may in part home via CXCR4. Overall, our data demonstrate differential homing mechanisms governing entry of unfractionated and lineage-depleted cells to irradiated bone marrow or thymus, with thymic homing of immature cells being pertussis-sensitive and mediated by the chemokine receptors CXCR4 and CCR5.

Distribution of the mutated delta 32 allele of the CCR5 gene in a Sicilian population

The CCR5 gene encodes a cell-surface chemokine receptor molecule that serves as a co-receptor for macrophage-tropic strains of human immunodeficiency virus type 1 (HIV-1). A mutation in this gene may alter the expression or the function of the protein product, thereby altering chemokine binding and/or signalling or HIV-1 infection of cells that normally express CCR5 protein. Individuals homozygous for a 32-bp deletion allele of CCR5 (CCR5 delta32), heritable as a Mendelian trait, are relatively resistant to HIV-1 infection. The CCR5 delta32 mutation is present in the Caucasian population at different frequencies. The aim of this study was to investigate the frequency of truncated alleles of the CCR5 delta32 gene in a Sicilian population, as the interpopulation variation in CCR5 delta32 frequency may be a significant factor in the prediction of AIDS endemicity in future studies. We examined 901 healthy individuals from several Sicilian provinces. We found a mean (+/- standard deviation) delta32 allele frequency (fr) of 0.04 +/- 0.012. The highest value was observed in the province of Messina, with a mean delta32 allele frequency of 0.06 +/- 0.024, where we collected samples from a cohort of 114 HIV-1-infected individuals. The observed frequency amongst these patients was quite low (fr = 0.03 +/- 0.031) compared to the healthy population, although the difference was not statistically significant.

Deficiency in CCR5 but not CCR1 protects against neointima formation in atherosclerosis-prone mice: involvement of IL-10

The chemokine RANTES has been implicated in neointimal hyperplasia after arterial injury. We analyzed the differential role of the RANTES receptors CCR1 and CCR5 by genetic deletion in apolipoprotein E–deficient mice. Deficiency in CCR5 significantly reduced neointimal area after arterial wire injury, associated with a decrease in macrophages, CD3+ T lymphocytes, and CCR2+ cells. In contrast, CCR1 deficiency did not affect neointimal area or cell content. Deletion of CCR5 entailed an up-regulation of the anti-inflammatory cytokine interleukin 10 (IL-10) in neointimal smooth muscle cells, and its antibody blockade reversed effects in CCR5–/– mice. Conversely, proinflammatory interferon γ was increased in the neointima of CCR1–/– mice, and its blockade unmasked a reduction in macrophage recruitment. Our data indicate that CCR5 is more crucial than CCR1 for neointimal plaque formation, and that its attenuation in CCR5–/– mice is due to an atheroprotective immune response involving IL-10. This harbors important implications for targeting chemokine receptors in vascular remodeling.

Selective transmission of CCR5-utilizing HIV-1: the 'gatekeeper' problem resolved?

Understanding the mechanisms of HIV-1 transmission is crucial for the development of effective preventive microbicides and vaccine strategies, and remains one of the main goals of HIV research. Over the past decade, many studies have focused on trying to identify the 'gatekeeping' mechanism that restricts the transmission of CXCR4-utilizing HIV-1 more efficiently than CCR5-utilizing HIV-1. However, to date, no study has explained the almost perfect negative selection of the former in vivo. Here, we propose that there is no single gatekeeper and that, instead, the selective transmission of R5 HIV-1 depends on the superimposition of multiple imperfect gatekeepers.

Role of CCR5 in the Pathogenesis of IL-13-Induced Inflammation and Remodeling

IL-13 is a major effector at sites of Th2 inflammation and tissue remodeling. In these locations, it frequently coexists with the CCR5 chemokine receptor and its ligands MIP-1alpha/CCL3 and MIP-1beta/CCL4. We hypothesized that CCR5 induction and activation play important roles in the pathogenesis of IL-13-induced tissue responses. To test this hypothesis, we evaluated the effects of IL-13 on the expression of CCR5 in the murine lung. We also compared the effects of lung-targeted transgenic IL-13 in mice treated with anti-CCR5 or an Ab control and mice with wild-type or null CCR5 loci. These studies demonstrate that IL-13 is a potent stimulator of epithelial cell CCR5 expression. They also demonstrate that CCR5 neutralization or a deficiency of CCR5 significantly decreases IL-13-induced inflammation, alveolar remodeling, structural and inflammatory cell apoptosis, and respiratory failure and death. Lastly, these studies provide mechanistic insights by demonstrating that CCR5 is required for optimal IL-13 stimulation of select chemokines (MIP-1alpha/CCL3, MIP-1beta/CCL4, MCP-1/CCL-2), matrix metalloproteinase-9 and cell death regulators (Fas, TNF, TNFR1, TNFR2, Bid), optimal IL-13 inhibition of alpha1-antitrypsin, and IL-13-induction of and activation of caspases-3, -8, and-9. Collectively, these studies demonstrate that CCR5 plays a critical role in the pathogenesis of IL-13-induced inflammation and tissue remodeling.

Comparative studies on mucosal and intravenous transmission of simian immunodeficiency virus (SIVsm): evolution of coreceptor use varies with pathogenic outcome

Coreceptor usage of isolates from 30 cynomolgus macaques infected intrarectally (n=22) or intravenously (n=8) with simian immunodeficiency virus of sooty mangabey origin (SIVsm) was evaluated in U87.CD4 and GHOST(3) cell lines. Based on progression rate, the animals were divided into progressors (18 animals), slow progressors (five animals) and long-term non-progressors (seven animals). There was no difference in how many or which coreceptors were used according to route of infection. All isolates but one used CCR5 for cell entry, and CCR5 was also the major coreceptor in 70 out of 105 isolates tested. In general, early isolates were multitropic, using CCR5, CXCR6 and/or gpr15. Interestingly, CXCR4-using viruses could be isolated on human peripheral blood mononuclear cells (PBMCs), but not on cynomolgus macaque PBMCs, suggesting that human PBMCs select for variants with CXCR4 use. Even though CXCR4-using SIV isolates have been reported rarely, we could recover CXCR4-using viruses from 13 monkeys. CXCR4 use either appeared early during the acute phase of infection and disappeared later or only appeared late in infection during immunodeficiency. Surprisingly, one late isolate from a progressor monkey did not use CCR5 at all and used the CXCR4 receptor with high efficiency. The ability to use many different receptors decreased over time in long-term non-progressor monkeys, whilst the majority of progressor monkeys showed broadening of coreceptor use, stable coreceptor use or fluctuation between the different coreceptor-usage patterns. The results indicate that, in the infected host, evolution of SIV coreceptor usage occurs, involving changes in the mode of coreceptor use.

Human immunodeficiency virus types 1 and 2 have different replication kinetics in human primary macrophage culture

This study compares the replication of primary isolates of human immunodeficiency virus type 2 (HIV-2) and type 1 (HIV-1) in monocyte-derived macrophages (MDMs). Eleven HIV-2 and five HIV-1 primary isolates that use CCR5, CXCR4 or both coreceptors to enter cells were included. Regardless of coreceptor preference, 10 of 11 HIV-2 viruses could enter, reverse transcribe and produce fully infectious virus in MDMs with efficiency equal to that in peripheral blood mononuclear cells. However, the kinetics of replication of HIV-2 compared with HIV-1 over time were distinct. HIV-2 had a burst of virus replication 2 days after infection that resolved into an apparent 'latent state' at day 3. HIV-1, however, continued to produce infectious virions at a lower, but steady, rate throughout the course of infection. These results may have implications for the lower pathogenesis and viral-load characteristics of HIV-2 infection.

Spatially distinct and functionally independent mechanisms of axonal degeneration in a model of HIV-associated sensory neuropathy

Sensory polyneuropathies are the most frequent neurological complication of human immunodeficiency virus (HIV) infection. Distal symmetric polyneuropathy (DSP), associated with HIV infection, is characterized by length-dependent axonal degeneration of sensory fibres. In rodent dorsal root ganglia (DRG) cultures, HIV viral envelope protein gp120 results in neurotoxicity and axonal degeneration. Since it is unknown whether the axonal degeneration is a consequence of neuronal death or whether it is due to a direct toxic effect on axons, we investigated gp120-induced axonal toxicity using compartmentalized cultures of sensory neurons. Our results show that gp120 causes neuronal apoptosis and axonal degeneration through two, independent and spatially separated mechanisms of action: (i) an indirect insult to cell bodies, requiring the presence of Schwann cells, results in neuronal apoptotic death and subsequent axonal degeneration; (ii) a direct, local toxicity exerted on axons through activation of mitochondrial caspase pathway that is independent of cell body. This local axonal toxicity is mediated through binding of gp120 to axonal chemokine receptors and can be prevented by chemokine receptor blockers. In conclusion, we propose a novel pathway of axonal degeneration mediated by gp120 that is dependent on local activation of caspases in the axon. This observation suggests that axonal protection is a relevant therapeutic target for HIV-associated sensory neuropathy. Furthermore, chemokine receptor inhibitors, which are currently being developed as HIV entry inhibitor drugs, may also have a therapeutic role in HIV-associated peripheral neuropathies by preventing axonal degeneration.

Human immunodeficiency virus fusion to dendritic cells declines as cells mature

The maturation of dendritic cells (DCs) is associated with a diminished ability to support human immunodeficiency virus (HIV) replication; however, the precise step in the HIV life cycle impaired by DC maturation remains uncertain. Using an HIV virion-based fusion assay, we now show that HIV fusion to monocyte-derived DCs (MDDCs) both decreases and kinetically slows when DCs are induced to mature with poly(I:C) and tumor necrosis factor alpha. Specifically, laboratory-adapted CCR5-tropic 81A virions fused with markedly lower efficiency to mature MDDCs than immature DCs. In contrast, fusion of NL4-3, the isogenic CXCR4-tropic counterpart of 81A, was low in both immature and mature MDDCs. Fusion mediated by primary HIV envelopes, including seven CCR5- and four CXCR4-tropic envelopes, also decreased with DC maturation. The kinetics of virion fusion were also altered by both the state of DC maturation and the coreceptor utilized. Fusion of 81A and NL4-3 virions was delayed in mature compared to immature MDDCs, and NL4-3 fused more slowly than 81A in both mature and immature MDDCs. Surprisingly, primary envelopes with CXCR4 tropism mediated fusion to immature MDDCs with efficiencies similar to those of primary CCR5-tropic envelopes. This result contrasted with the marked preferential fusion of the laboratory-adapted 81A over NL4-3 in immature MDDCs and in ex vivo Langerhans cells, indicating that these laboratory-adapted HIV strains do not fully recapitulate all of the properties of primary HIV isolates. In conclusion, our results demonstrate that the defect in HIV replication observed in mature MDDCs stems at least in part from a decline in viral fusion.

Expression of CCL5 (RANTES) and CCR5 in prostate cancer

BACKGROUND

Expression of the inflammatory chemokine CCL5 (RANTES) by tumor cells is thought to correlate with the progression of several cancers. CCL5 was shown to induce breast cancer cell migration, mediated by the receptor CCR5. A CCR5 antagonist was demonstrated to inhibit experimental breast tumor growth. Recently, CCL5 and CCR5 mRNA expression was reported in prostate cancer (PCa) tissues. Herein, we characterized CCL5 and CCR5 expression in cultures of PCa cells and explored possible functions of CCL5 in PCa progression.

METHODS

Quantitative RT-PCR, ELISA, and immunohistochemical staining were performed to examine CCL5 expression in prostate cell lines. CCR5 expression was measured by flow cytometry. Proliferation and invasion assays were performed to determine potential functions of CCL5 and CCR5 in PCa.

RESULTS

Expression of CCL5 mRNA and protein was found in human PCa cell lines (PC-3; DU-145; LNCaP) and primary prostate adenocarcinoma cells. CCL5 and CCR5 were also detected in human PCa tissues. CCR5 expression was demonstrated on the cell surface of PCa cells, as well as in intracellular pools. Incubation with CCL5 (10-100 ng/ml) induced PCa cell proliferation, and the CCR5 antagonist TAK-779 inhibited CCL5-induced proliferation. CCL5 was found to stimulate PCa cell invasion, and TAK-779 blocked the effects of CCL5.

CONCLUSIONS

In light of evidence that inflammation influences the pathogenesis of PCa, these results suggest that inflammatory chemokines, such as CCL5, expressed by prostate cells may act directly on the growth and survival of PCa cells. Chemokine receptor antagonists may thus block autocrine mechanisms of PCa progression.

Use of a novel GFP reporter cell line to examine replication capacity of CXCR4- and CCR5-tropic HIV-1 by flow cytometry

The rate of HIV-1 disease progression correlates strongly with plasma viral load and is likely to be influenced by both host and viral determinants. Though interest in the impact of viral replication capacity during HIV-1 infection has been increasing, especially with respect to drug resistance mutations, its influence on disease course remains poorly understood. This is due in part to significant drawbacks in conventional means of measuring HIV-1 growth in vitro (i.e. expense, inconvenience, and experimental variability). A FACS-based method is described here to measure HIV-1 replication sensitively and a modification of this method can be used to determine viral titer accurately. Importantly, the target cells used are permissive to CXCR4- and CCR5-tropic HIV-1 strains. In pilot experiments, the growth kinetics of laboratory-adapted strains NL4-3 and IIIB were examined carefully. Using this method, differences were observed in growth kinetics between three laboratory strains and seven primary isolates, indicating the potential for a broad range of in vitro replication capacities among individual isolates. In conclusion, this FACS-based method provides a sensitive approach to measure the replication capacity of HIV-1 and may prove useful in studies examining the impact of viral fitness on disease progression.

Human immunodeficiency virus type 1 coreceptor switching: V1/V2 gain-of-fitness mutations compensate for V3 loss-of-fitness mutations

Human immunodeficiency virus type 1 (HIV-1) entry into target cells is mediated by the virus envelope binding to CD4 and the conformationally altered envelope subsequently binding to one of two chemokine receptors. HIV-1 envelope glycoprotein (gp120) has five variable loops, of which three (V1/V2 and V3) influence the binding of either CCR5 or CXCR4, the two primary coreceptors for virus entry. Minimal sequence changes in V3 are sufficient for changing coreceptor use from CCR5 to CXCR4 in some HIV-1 isolates, but more commonly additional mutations in V1/V2 are observed during coreceptor switching. We have modeled coreceptor switching by introducing most possible combinations of mutations in the variable loops that distinguish a previously identified group of CCR5- and CXCR4-using viruses. We found that V3 mutations entail high risk, ranging from major loss of entry fitness to lethality. Mutations in or near V1/V2 were able to compensate for the deleterious V3 mutations and may need to precede V3 mutations to permit virus survival. V1/V2 mutations in the absence of V3 mutations often increased the capacity of virus to utilize CCR5 but were unable to confer CXCR4 use. V3 mutations were thus necessary but not sufficient for coreceptor switching, and V1/V2 mutations were necessary for virus survival. HIV-1 envelope sequence evolution from CCR5 to CXCR4 use is constrained by relatively frequent lethal mutations, deep fitness valleys, and requirements to make the right amino acid substitution in the right place at the right time.

Interleukin 12 induces T-cell recruitment into the atherosclerotic plaque

CD4 T cells, through the release of cytokines as well as direct effector functions, have been implicated in promoting inflammation of the atherosclerotic plaque. Plaque-infiltrating CD4 T cells include a specialized subset of (CD4+)CD28- T cells that express a unique profile of regulatory receptors and are responsive to novel microenvironmental cues. Here we report that (CD4+)CD28- T cells, either isolated from the plaque tissue or from the blood of patients with acute coronary syndrome (ACS), spontaneously express interleukin (IL)-12 receptors, even in the absence of antigenic stimulation. (CD4+)CD28- IL-12R+ cells responded to IL-12 stimulation with the upregulation of the chemokine receptor CCR5 and the C-type lectin receptor CD161, both implicated in regulating tissue homing of effector T cells. IL-12 treatment of (CD4+)CD28- T cells enhanced their chemotaxis and transendothelial migration toward the chemokine CCL5. In vivo relevance for the role of IL-12 in regulating the recruitment of (CD4+)CD28- T cells into the atheroma was examined in human atheroma-SCID mouse chimeras. Exposure of nonstimulated (CD4+)CD28- T cells to IL-12 was sufficient to amplify T-cell accumulation within the inflamed plaque, and coadministration of anti-CCR5 antibodies blocked T-cell recruitment into the plaque. Thus, (CD4+)CD28- T cells functionally resemble NK cells, which have proinflammatory activity even in the unprimed state and respond to any IL-12-inducing host infection with a shift in tissue trafficking and accrual in inflammatory lesions.

Increased HIV-DNA load in CCR5-negative lymphocytes without viral phenotypic change

We have previously described a selective increase in HIV-DNA content in CCR5-negative lymphocytes from late stage HIV-infected patients. Here, we show that this increase occurred even in the absence of viral phenotypic switching from CCR5- to CXCR4-tropic. This leads us to hypothesize that early and late CCR5-tropic viruses might be different in the ability to infect CCR5-low or -negative cells. We compared a set of early CCR5-tropic viruses with low viral DNA content in CCR5-negative cells to a set of late CCR5-tropic viruses with high viral DNA content in CCR5-negative cells. We could not find any significant differences between the two sets of viruses in the aspects of relative infectivity in CCR5-low cells and the level of inhibition by beta-chemokine. This suggested that there may be some changes in cellular phenotype or environment that allows an expansion of susceptible cell population in late stages HIV infection. Understanding these changes may provide a novel approach for HIV therapy.

TAK-652 inhibits CCR5-mediated human immunodeficiency virus type 1 infection in vitro and has favorable pharmacokinetics in humans

The first small-molecule CCR5 antagonist, TAK-779, could not be developed as an anti-human immunodeficiency virus type (anti-HIV-1) agent because of its poor oral bioavailability. TAK-652 is an orally bioavailable TAK-779 derivative with potent anti-HIV-1 activity. TAK-652 inhibited the binding of RANTES (regulated on activation, normal T-cell expressed and secreted), macrophage inflammatory protein 1alpha (MIP-1alpha), and MIP-1beta to CCR5-expressing cells at nanomolar concentrations. TAK-652 could also suppress the binding of monocyte chemotactic protein 1 (MCP-1) to CCR2b-expressing cells. However, its inhibitory effect on ligand binding to other chemokine receptors was limited. TAK-652 was active against CCR5-using (R5) HIV-1 but totally inactive against CXCR4-using (X4) HIV-1. The compound was active against R5 HIV-1 clinical isolates containing reverse transcriptase and protease inhibitor-resistant mutations, with a mean 50% effective concentration (EC50) and EC90 of 0.061 and 0.25 nM, respectively. In addition, recombinant R5 viruses carrying different subtype (A to G) envelope proteins were equally susceptible to TAK-652. A single oral administration of TAK-652 up to 100 mg was safe and well tolerated in humans. The compound displayed favorable pharmacokinetics, and its plasma concentration was 7.2 ng/ml (9.1 nM) even 24 h after the administration of 25 mg. Thus, TAK-652 is a promising candidate as a novel entry inhibitor of HIV-1.