Nonproductive human immunodeficiency virus type 1 infection of human fetal astrocytes: independence from CD4 and major chemokine receptors.
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Human immunodeficiency virus type 1 (HIV-1) infection of the brain is associated with neurological manifestations both in adults and in children. The primary target for HIV-1 infection in the brain is the microglia, but astrocytes can also be infected. We tested 26 primary HIV-1 isolates for their capacity to infect human fetal astrocytes in culture. Eight of these isolates, independent of their biological phenotype and chemokine receptor usage, were able to infect astrocytes. Although no sustained viral replication could be demonstrated, the virus was recovered by coculture with receptive cells such as macrophages or on stimulation with interleukin-1beta. To gain knowledge into the molecular events that regulate attachment and penetration of HIV-1 in astrocytes, we investigated the expression of several chemokine receptors. Fluorocytometry and calcium-mobilization assay did not provide evidence of expression of any of the major HIV-1 coreceptors, including CXCR4, CCR5, CCR3, and CCR2b, as well as the CD4 molecule on the cell surface of human fetal astrocytes. However, mRNA transcripts for CXCR4, CCR5, Bonzo/STRL33/TYMSTR, and APJ were detected by RT-PCR. Furthermore, infection of astrocytes by HIV-1 isolates with different chemokine receptor usage was not inhibited by the chemokines SDF-1beta, RANTES, MIP-1beta, or MCP-1 or by antibodies directed against the third variable region or the CD4 binding site of gp120. These data show that astrocytes can be infected by primary HIV-1 isolates via a mechanism independent of CD4 or major chemokine receptors. Furthermore, astrocytes are potential carriers of latent HIV-1 and on activation may be implicated in spreading the infection to other neighbouring cells, such as microglia or macrophages. (+info)
Soluble complexes of regulated upon activation, normal T cells expressed and secreted (RANTES) and glycosaminoglycans suppress HIV-1 infection but do not induce Ca(2+) signaling.
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Chemokines comprise a family of low-molecular-weight proteins that elicit a variety of biological responses including chemotaxis, intracellular Ca(2+) mobilization, and activation of tyrosine kinase signaling cascades. A subset of chemokines, including regulated upon activation, normal T cell expressed and secreted (RANTES), macrophage inflammatory protein-1alpha (MIP-1alpha), and MIP-1beta, also suppress infection by HIV-1. All of these activities are contingent on interactions between chemokines and cognate seven-transmembrane spanning, G protein-coupled receptors. However, these activities are strongly inhibited by glycanase treatment of receptor-expressing cells, indicating an additional dependence on surface glycosaminoglycans (GAG). To further investigate this dependence, we examined whether soluble GAG could reconstitute the biological activities of RANTES on glycanase-treated cells. Complexes formed between RANTES and a number of soluble GAG failed to induce intracellular Ca(2+) mobilization on either glycanase-treated or untreated peripheral blood mononuclear cells and were unable to stimulate chemotaxis. In contrast, the same complexes demonstrated suppressive activity against macrophage tropic HIV-1. Complexes composed of (125)I-labeled RANTES demonstrated saturable binding to glycanase-treated peripheral blood mononuclear cells, and such binding could be reversed partially by an anti-CCR5 antibody. These results suggest that soluble chemokine-GAG complexes represent seven-transmembrane ligands that do not activate receptors yet suppress HIV infection. Such complexes may be considered as therapeutic formulations for the treatment of HIV-1 infection. (+info)
A CXC chemokine receptor, CXCR5/BLR1, is a novel and specific coreceptor for human immunodeficiency virus type 2.
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G protein-coupled receptors serve as coreceptors in the infection process of human immunodeficiency virus type-1 (HIV-1), type-2 (HIV-2), and simian immunodeficiency virus (SIV). In this study, we showed that a CXC-CKR, CXCR5/BLR1, is a novel coreceptor for HIV-2, but for neither HIV-1 nor SIV. The expression of CXCR5 was detected by polymerase chain reaction after reverse transcription of cellular mRNA from S+L-HOS/CD4 cells and MT-2 human T cells, and the CXCR5 gene was cloned into an expression vector. S+L-HOS/CD4 cells were susceptible to several HIV-2 strains but not most HIV-1 strains. To examine a coreceptor activity of CXCR5, we used NP-2/CD4, which is a human glioma cell line, NP-2, transduced with the CD4 gene that shows strict resistance to infection with HIV-1, HIV-2, SIVmac, SIVagm, or SIVmnd strain. When CXCR5 was transduced into NP-2/CD4 cells, they became highly susceptible to HIV-2ROD and HIV-2CBL23 strains in a CD4-dependent manner but to not to HIV-1 or SIV strains. Anti-CXCR5 monoclonal antibody and a ligand for CXCR5, BCA-1, inhibited HIV-2 infection to NP-2/CD4/CXCR5 cells. Our findings suggest a possibility that CXCR5/BLR1 serves as a coreceptor for HIV-2 strains in vivo. (+info)
A putative G protein-coupled receptor, RDC1, is a novel coreceptor for human and simian immunodeficiency viruses.
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More than 10 G protein-coupled receptors (GPCRs) have been shown to act as coreceptors for infection of human immunodeficiency virus type 1 (HIV-1), HIV-2, and simian immunodeficiency virus (SIV). We have isolated HIV-1 variants infectious to primary brain-derived CD4-positive cells (BT-3 and BT-20/N) and U87/CD4 glioma cells that are resistant to T-cell line-tropic (T-tropic), macrophage-tropic (M-tropic), and T- and M-tropic (dualtropic) (X4, R5, and R5X4) HIV-1 strains. These primary brain-derived cells were also highly susceptible to HIV-2(ROD), HIV-2(SBL6669), and SIV(mndGB-1). A factor or coreceptor that determines the susceptibility of these brain-derived cells to these HIV and SIV strains has not been fully identified. To identify this coreceptor, we examined amino acid sequences of all known HIV and SIV coreceptors and noticed that tyrosine residues are well conserved in their extracellular amino-terminal domains. By this criterion, we selected 18 GPCRs as candidates of coreceptors for HIV and SIV strains infectious to these brain-derived cells. mRNA expression of an orphan GPCR, RDC1, was detected in the brain-derived cells, the C8166 T-cell line, and peripheral blood lymphocytes, all of which are susceptible to HIV-1 variants, but not in macrophages, which are resistant to them. When a CD4-expressing cell line, NP-2/CD4, which shows strict resistance to infection not only with HIV-1 but also with HIV-2 or SIV, was transduced with the RDC1 gene, the cells became highly susceptible to HIV-2 and SIV(mnd) strains but to neither M- nor T-tropic HIV-1 strains. The cells also acquired a low susceptibility to the HIV-1 variants. These findings indicate that RDC1 is a novel coreceptor for several HIV-1, HIV-2, and SIV strains which infect brain-derived cells. (+info)
A human milk factor susceptible to cathepsin D inhibitors enhances human immunodeficiency virus type 1 infectivity and allows virus entry into a mammary epithelial cell line.
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Human immunodeficiency virus type 1 (HIV-1) growth in lymphocyte cultures was increased when the virus inoculum was incubated in breast milk. The enhancing effect of milk was abolished by anti-cathepsin D antibody or by pepstatin A, a cathepsin D inhibitor. The cathepsin D-producing CD4-negative MCF7 mammary cells supported the growth of some HIV-1 isolates. An MCF7 line chronically producing HIV-1 IIIb was obtained. Cathepsin D may induce conformational modification of viral gp120, allowing direct interaction with a coreceptor. We demonstrated the presence of CXCR4 mRNA in MCF7 cells. (+info)
Differences among HIV-1 variants in their ability to elicit secretion of TNF-alpha.
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HIV-1 infection of human PBMC has been shown to elicit secretion of several different cytokines. TNF-alpha secretion induced by this virus has been of particular interest because it has been associated with the development of HIV-1 dementia and because TNF-alpha increases viral replication by enhancing NF-kappaB interaction with the viral promoter, the HIV-1 long terminal repeat. Thus, an autocrine pathway is potentially created in which HIV-1 stimulates its own replication. Conflicting reports exist, however, on the ability of HIV-1 to induce TNF-alpha secretion in vitro or in vivo. Using experimental protocols that controlled for potential bacterial endotoxin-induced TNF-alpha secretion, the current study demonstrates significant differences in TNF-alpha-eliciting properties among primary and laboratory obtained HIV-1. The relative TNF-alpha-inducing ability of different variants is conserved when tested using PBMC from different individuals. Elicitation of TNF-alpha secretion was not blocked by exposure of cells to zidovudine, indicating that viral integration was not required to induce secretion. Rather, the interaction between the virus and cell surface is critical for TNF-alpha induction, as Abs against CD4 or CCR5 blocked the induction of TNF-alpha synthesis by PBMC when added before virus exposure. Furthermore, the ability to induce TNF-alpha secretion mapped to a region of the HIV-1 env gene that includes the third hypervariable domain. Differences in the ability of different HIV-1 variants to elicit TNF-alpha may account for individual differences in HIV-1 disease course. (+info)
Broadening of coreceptor usage by human immunodeficiency virus type 2 does not correlate with increased pathogenicity in an in vivo model.
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The pathogenic properties of four primary human immunodeficiency virus type 2 (HIV-2) isolates and two primary HIV-2 biological clones were studied in an in vivo human-to-mouse chimeric model. The cell-associated viral load and the ability to reduce the severity of the induced graft-versus-host disease symptoms, the CD4/CD8 ratio and the level of repopulation of the mouse tissues by the graft, were determined. All HIV-2 strains, irrespective of their in vitro biological phenotype, replicated to high titres and significantly reduced graft-versus-host disease symptoms as well as the CD4/CD8 ratios. Reduction of graft repopulation caused by infection with the respective HIV-2 strains showed that the in vitro replication rate, syncytium-inducing capacity and ability to infect human macrophages did influence the in vivo pathogenic potential whereas broadening of coreceptor usage did not. (+info)
CXC and CC chemokine receptors on coronary and brain endothelia.
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BACKGROUND: Chemokine receptors on leukocytes play a key role in inflammation and HIV-1 infection. Chemokine receptors on endothelia may serve an important role in HIV-1 tissue invasion and angiogenesis. MATERIALS AND METHODS: The expression of chemokine receptors in human brain microvascular endothelial cells (BMVEC) and coronary artery endothelial cells (CAEC) in vitro and cryostat sections of the heart tissue was determined by light and confocal microscopy and flow cytometry with monoclonal antibodies. Chemotaxis of endothelia by CC chemokines was evaluated in a transmigration assay. RESULTS: In BMVEC, the chemokine receptors CCR3 and CXCR4 showed the strongest expression. CXCR4 was localized by confocal microscopy to both the cytoplasm and the plasma membrane of BMVEC. In CAEC, CXCR4 demonstrated a strong expression with predominantly periplasmic localization. CCR5 expression was detected both in BMVEC and CAEC but at a lower level. Human umbilical cord endothelial cells (HUVEC) expressed strongly CXCR4 but only weakly CCR3 and CCR5. Two additional CC chemokines, CCR2A and CCR4, were detected in BMVEC and CAEC by immunostaining. Immunocytochemistry of the heart tissues with monoclonal antibodies revealed a high expression of CXCR4 and CCR2A and a low expression of CCR3 and CCR5 on coronary vessel endothelia. Coronary endothelia showed in vitro a strong chemotactic response to the CC chemokines RANTES, MIP-1alpha, and MIP-1beta. CONCLUSIONS: The endothelia isolated from the brain display strongly both the CCR3 and CXCR4 HIV-1 coreceptors, whereas the coronary endothelia express strongly only the CXCR4 coreceptor. CCR5 is expressed at a lower level in both endothelia. The differential display of CCR3 on the brain and coronary endothelia could be significant with respect to the differential susceptibility of the heart and the brain to HIV-1 invasion. In addition, CCR2A is strongly expressed in the heart endothelium. All of the above chemokine receptors could play a role in endothelial migration and repair. (+info)