A functional, discontinuous HIV-1 gp120 C3/C4 domain-derived, branched, synthetic peptide that binds to CD4 and inhibits MIP-1alpha chemokine binding.
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This paper describes a branched synthetic peptide [3.7] that incorporates sequence discontinuous residues of HIV-1 gp120 constant regions. The approach was to bring together residues of gp120 known to interact with human cell membranes such that the peptide could fold to mimic the native molecule. The peptide incorporates elements of both the conserved CD4 and CCR5 binding sites. The 3.7 peptide, which cannot be produced by conventional genetic engineering methods, is recognized by antiserum raised to native gp120. The peptide also binds to CD4 and competitively inhibits binding of QS4120 an antibody directed against the CDR2 region of CD4. When preincubated with the CD4+ve MM6 macrophage cell line, which expresses mRNA for the CCR3 and CCR5 chemokine receptors, both 3.7 and gp120 inhibit binding of the chemokine MIP-1alpha. The peptide also inhibits infection of primary macrophages by M-tropic HIV-1. Thus, 3.7 is a prototype candidate peptide for a vaccine against HIV-1 and represents a novel approach to the rational design of peptides that can mimic complex sequence discontinuous ligand binding sites of clinically relevant proteins. (+info)
Induction of macrophage C-C chemokine expression by titanium alloy and bone cement particles.
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Particulate wear debris is associated with periprosthetic inflammation and loosening in total joint arthroplasty. We tested the effects of titanium alloy (Ti-alloy) and PMMA particles on monocyte/macrophage expression of the C-C chemokines, monocyte chemoattractant protein-1 (MCP-1), monocyte inflammatory protein-1 alpha (MIP-1alpha), and regulated upon activation normal T expressed and secreted protein (RANTES). Periprosthetic granulomatous tissue was analysed for expression of macrophage chemokines by immunohistochemistry. Chemokine expression in human monocytes/macrophages exposed to Ti-alloy and PMMA particles in vitro was determined by RT-PCR, ELISA and monocyte migration. We observed MCP-1 and MIP-1alpha expression in all tissue samples from failed arthroplasties. Ti-alloy and PMMA particles increased expression of MCP-1 and MIP-1alpha in macrophages in vitro in a dose- and time-dependent manner whereas RANTES was not detected. mRNA signal levels for MCP-1 and MIP-1alpha were also observed in cells after exposure to particles. Monocyte migration was stimulated by culture medium collected from macrophages exposed to Ti-alloy and PMMA particles. Antibodies to MCP-1 and MIP-1alpha inhibited chemotactic activity of the culture medium samples. Release of C-C chemokines by macrophages in response to wear particles may contribute to chronic inflammation at the bone-implant interface in total joint arthroplasty. (+info)
Differential regulation of eosinophil chemokine signaling via CCR3 and non-CCR3 pathways.
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To investigate eosinophil stimulation by chemokines we developed a sensitive assay of leukocyte shape change, the gated autofluorescence/forward scatter assay. Leukocyte shape change responses are mediated through rearrangements of the cellular cytoskeleton in a dynamic process typically resulting in a polarized cell and are essential to the processes of leukocyte migration from the microcirculation into sites of inflammation. We examined the actions of the chemokines eotaxin, eotaxin-2, monocyte chemoattractant protein-1 (MCP-1), MCP-3, MCP-4, RANTES, macrophage inflammatory protein-1alpha (MIP-1alpha), and IL-8 on leukocytes in mixed cell suspensions and focused on the responses of eosinophils to C-C chemokines. Those chemokines acting on CCR3 induced a rapid shape change in eosinophils from all donors; of these, eotaxin and eotaxin-2 were the most potent. Responses to MCP-4 were qualitatively different, showing marked reversal of shape change responses with agonist concentration and duration of treatment. In contrast, MIP-1alpha induced a potent response in eosinophils from a small and previously undescribed subgroup of donors via a non-CCR3 pathway likely to be CCR1 mediated. Incubation of leukocytes at 37 degrees C for 90 min in the absence of extracellular calcium up-regulated responses to MCP-4 and MIP-1alpha in the majority of donors, and there was a small increase in responses to eotaxin. MIP-1alpha responsiveness in vivo may therefore be a function of both CCR1 expression levels and the regulated efficiency of coupling to intracellular signaling pathways. The observed up-regulation of MIP-1alpha signaling via non-CCR3 pathways may play a role in eosinophil recruitment in inflammatory states such as occurs in the asthmatic lung. (+info)
Effects of dexamethasone and ibuprofen on LPS-induced gene expression of TNF alpha, IL-1 beta, and MIP-1 alpha in rat lung.
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AIM: To study the kinetics of tumor necrosis factor alpha (TNF alpha), interleukine-1 (IL-1 beta), and macrophage inflammatory protein-1 alpha (MIP-1 alpha) gene expression in rat lung after i.p. lipopolysaccharides (LPS) and the effect of dexamethasone (Dex) and ibuprofen (Ibu) on the cytokines gene expression. METHODS: The amount of Evans blue in lung was measured by fluorescence method. The mRNA levels of TNF alpha, IL-1 beta, and MIP-1 alpha in rat lung were assessed by slot blot analysis. RESULTS: The mRNA levels of TNF alpha, IL-1 beta, and MIP-1 alpha in rat lung after i.p. LPS increased in a dose-dependent manner, and peaked at 2, 6, and 12 h, respectively. Both Dex 50 mg.kg-1 and Ibu 90 mg.kg-1 injected at 1 h before i.p. LPS markedly decreased the content of Evans blue in lung at 1 h after i.p. LPS. After Dex or Ibu pretreatment, the peak levels of TNF alpha, IL-1 beta, and MIP-1 alpha mRNA decreased markedly compared with LPS alone. CONCLUSION: The gene expression of TNF alpha, IL-1 beta, and MIP-1 alpha in rat lung increased after i.p. LPS. Dex and Ibu prevented LPS-induced lung injury through inhibiting the cytokines gene expression. (+info)
Intracellular adhesion molecule-1 modulates beta-chemokines and directly costimulates T cells in vivo.
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The potential roles of adhesion molecules in the expansion of T cell-mediated immune responses in the periphery were examined using DNA immunogen constructs as model antigens. We coimmunized cDNA expression cassettes encoding the adhesion molecules intracellular adhesion molecule-1 (ICAM-1), lymphocyte function associated-3 (LFA-3), and vascular cell adhesion molecule-1 (VCAM-1) along with DNA immunogens, and we analyzed the resulting antigen-specific immune responses. We observed that antigen-specific T-cell responses can be enhanced by the coexpression of DNA immunogen and adhesion molecules ICAM-1 and LFA-3. Coexpression of ICAM-1 or LFA-3 molecules along with DNA immunogens resulted in a significant enhancement of T-helper cell proliferative responses. In addition, coimmunization with pCICAM-1 (and more moderately with pCLFA-3) resulted in a dramatic enhancement of CD8-restricted cytotoxic T-lymphocyte responses. Although VCAM-1 and ICAM-1 are similar in size, VCAM-1 coimmunization did not have any measurable effect on cell-mediated responses. These results suggest that ICAM-1 and LFA-3 provide direct T-cell costimulation. These observations are further supported by the finding that coinjection with ICAM-1 dramatically enhanced the level of interferon-gamma (IFN-gamma) and beta-chemokines macrophage inflammatory protein-1alpha (MIP-1alpha), MIP-1beta, and regulated on activation normal T-cell expression and secreted (RANTES) produced by stimulated T cells. Through comparative studies, we observed that ICAM-1/LFA-1 T-cell costimulatory pathways are independent of CD86/CD28 pathways and that they may synergistically expand T-cell responses in vivo. (+info)
Tyrosine sulfation of the amino terminus of CCR5 facilitates HIV-1 entry.
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Chemokine receptors and related seven-transmembrane-segment (7TMS) receptors serve as coreceptors for entry of human and simian immunodeficiency viruses (HIV-1, HIV-2, and SIV) into target cells. Each of these otherwise diverse coreceptors contains an N-terminal region that is acidic and tyrosine rich. Here, we show that the chemokine receptor CCR5, a principal HIV-1 coreceptor, is posttranslationally modified by O-linked glycosylation and by sulfation of its N-terminal tyrosines. Sulfated tyrosines contribute to the binding of CCR5 to MIP-1 alpha, MIP-1 beta, and HIV-1 gp120/CD4 complexes and to the ability of HIV-1 to enter cells expressing CCR5 and CD4. CXCR4, another important HIV-1 coreceptor, is also sulfated. Tyrosine sulfation may contribute to the natural function of many 7TMS receptors and may be a modification common to primate immunodeficiency virus coreceptors. (+info)
Secretion of beta-chemokines by bronchoalveolar lavage cells during primary infection of macaques inoculated with attenuated nef-deleted or pathogenic simian immunodeficiency virus strain mac251.
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Primary infection of macaques with simian immunodeficiency virus (SIV) as a model of human immunodeficiency virus (HIV) infection represents a unique opportunity to investigate early lentivirus-host interactions. In order to gain insight into immunopathogenic events taking place in the lung during lentiviral infection, we analysed lymphocyte expansion in the lung and chemokine secretion by mononuclear cells obtained by bronchoalveolar lavage (BALMCs) during primary infection by a pathogenic and a non-pathogenic SIV. Two groups of cynomolgus macaques were inoculated intravenously with a fully pathogenic isolate of SIVmac251 or with an attenuated, nef-deleted, molecular clone of SIVmac251. Spontaneous MIP-1alpha, MIP-1beta and RANTES production was assessed by ELISA in supernatants of short-term cultured BALMCs. Kinetics of haematological, virological and immunological parameters were investigated simultaneously. All 11 inoculated animals became infected. Monkeys inoculated with the nef-deleted SIV clone exhibited a significantly reduced plasma virus load and a less pronounced accumulation of lymphocytes in the lung compared to monkeys infected with the pathogenic SIVmac251 isolate. Compared to pre-infection levels, we observed an increase in the levels of RANTES, MIP1-alpha and MIP1-beta production in the two groups of monkeys, by the time of peak viraemia. Strikingly, a greater enhancement of RANTES and MIP-1alpha production was detected in monkeys infected with the attenuated virus. Given the potential influence of beta-chemokines on the immune response and virus replication, such results suggest that RANTES, MIP1-alpha and MIP1-beta could contribute to the singular features of the immune response elicited during infection of macaques with an attenuated SIV. (+info)
Specific activation of leukocyte beta2 integrins lymphocyte function-associated antigen-1 and Mac-1 by chemokines mediated by distinct pathways via the alpha subunit cytoplasmic domains.
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We show that CC chemokines induced a sustained increase in monocyte adhesion to intercellular adhesion molecule-1 that was mediated by Mac-1 (alphaMbeta2) but not lymphocyte function-associated antigen-1 (LFA-1; alphaLbeta2). In contrast, staining for an activation epitope revealed a rapid and transient up-regulation of LFA-1 activity by monocyte chemotactic protein-1 (MCP-1) in monocytes and Jurkat CCR2 chemokine receptor transfectants or by stromal-derived factor-1alpha in Jurkat cells. Differential kinetics for activation of Mac-1 (sustained) and LFA-1 (transient) avidity in response to stromal-derived factor-1alpha were confirmed by expression of alphaM or alphaL in alphaL-deficient Jurkat cells. Moreover, expression of chimeras containing alphaL and alphaM cytoplasmic domain exchanges indicated that alpha cytoplasmic tails conferred the specific mode of regulation. Coexpressing alphaM or chimeras in mutant Jurkat cells with a "gain of function" phenotype that results in constitutively active LFA-1 demonstrated that Mac-1 was not constitutively active, whereas constitutive activity was mediated via the alphaL cytoplasmic tail, implying the presence of distinct signaling pathways for LFA-1 and Mac-1. Transendothelial chemotaxis of monocytes in response to MCP-1 was dependent on LFA-1; however, Mac-1 was involved at MCP-1 concentrations stimulating its avidity, showing differential contributions of beta2 integrins. Our data suggest that a specific regulation of beta2 integrin avidity by chemokines may be important in leukocyte extravasation and may be triggered by distinct activation pathways transduced via the alpha subunit cytoplasmic domains. (+info)