The CC-chemokine RANTES (regulated on activation normal T-cell expressed and secreted; CCL5) transduces multiple intracellular signals. Like all chemokines, it stimulates G protein-coupled receptor (GPCR) activity through interaction with its cognate chemokine receptor(s), but in addition also activates a GPCR-independent signaling pathway. Here, we show that the latter pathway is mediated by an interaction between RANTES and glycosaminoglycan chains of CD44. We provide evidence that this association, at both low, physiologically relevant, and higher, probably supraphysiologic concentrations of RANTES, induces the formation of a signaling complex composed of CD44, src kinases, and adapter molecules. This triggers the activation of the p44/42 mitogen-activated protein kinase (MAPK) pathway. By specifically reducing CD44 expression using RNA interference we were able to demonstrate that the p44/p42 MAPK activation by RANTES requires a high level of CD44 expression. As well as potently inhibiting the entry of CCR5 using HIV-1 strains, RANTES can enhance HIV-1 infectivity under certain experimental conditions. This enhancement process depends in part on the activation of p44/p42 MAPK. Here we show that silencing of CD44 in HeLa-CD4 cells prevents the activation of p44/p42 MAPK and leads to a substantial reduction in HIV IntroductionThe chemokine RANTES (regulated on activation normal T-cell expressed and secreted; CCL5) is a member of the CC-chemokine family, a group of small proteins with a highly conserved tertiary. 1,2 Chemokines recruit and activate specific leukocyte populations. Multiple chemokine receptors with partially overlapping specificities for ligand binding have been described, suggesting a possible redundancy of the system. However, an increased selectivity of the action of chemokines is thought to be gained through their ability to discern and preferentially bind to certain glycosaminoglycan (GAG) subpopulations, a process considered important in mediating tissue-specific leukocyte recruitment. [3][4][5][6] The chemokine RANTES has a complex influence on the biology of a variety of cell types including T lymphocytes, monocytes, natural killer cells, dendritic cells, basophils, and eosinophils. 7,8 At nanomolar concentrations, RANTES binds to and activates several 7-transmembrane G protein-coupled receptors (GPCRs), namely the chemokine receptors CCR1, CCR3, and CCR5. Ligation of these receptors activates a heterotrimeric G␣i protein-coupled signaling pathway, characterized by a transient Ca 2ϩ influx, 7,9 and triggers activation of cell polarization and chemotaxis. 10 In addition to these classic chemokine-activated responses, RANTES also induces several biochemical and biologic effects that are to date unique to this chemokine and that are triggered through a GPCR-independent pathway. Induction of this pathway is mediated by protein tyrosine kinases (PTKs), occurs at high micromolar concentrations of the chemokine, and leads to a sustained influx of Ca 2ϩ . 9 We and others have previously demonstr...

This study focused on the in vitro infection of mouse and human neuroblastoma cells and the in vivo infection of the murine central nervous system with a recombinant measles virus. An undifferentiated mouse neuroblastoma cell line (TMN) was infected with the vaccine strain of measles virus (MVeGFP), which expresses enhanced green fluorescent protein (EGFP). MVeGFP infected the cells, and cell-to-cell spread was studied by virtue of the resulting EGFP autofluorescence, using real-time confocal microscopy. Cells were differentiated to a neuronal phenotype, and extended processes, which interconnected the cells, were observed. It was also possible to infect the differentiated neuroblastoma cells (dTMN) with MVeGFP. Single autofluorescent EGFP-positive cells were selected at the earliest possible point in the infection, and the spread of EGFP autofluorescence was monitored. In this instance the virus used the interconnecting processes to spread from cell to cell. Human neuroblastoma cells (SH-SY-5Y) were also infected with MVeGFP. The virus infected these cells, and existing processes were used to initiate new foci of infection at distinct regions of the monolayer. Transgenic animals expressing CD46, a measles virus receptor, and lacking interferon type 1 receptor gene were infected intracerebrally with MVeGFP. A productive infection ensued, and the mice exhibited clinical signs of infection, such as ataxia and an awkward gait, identical to those previously observed for the parental virus (Edtag). Mice were sacrificed, and brain sections were examined for EGFP autofluorescence by confocal scanning laser microscopy over a period of 6 h. EGFP was detected in discrete focal regions of the brain and in processes, which extended deep into the parenchyma. Collectively, these results indicate (i) that MVeGFP can be used to monitor virus replication sensitively, in real time, in animal tissues, (ii) that infection of ependymal cells and neuroblasts provides a route by which measles virus can enter the central nervous system in mouse models of encephalitis, and (iii) that upon infection, the virus spreads transneuronally.Measles virus (MV) infects over 40 million individuals each year. Encephalomyelitis can occur as part of the acute infection, while subacute sclerosing panencephalitis (SSPE) and measles inclusion body encephalitis (MIBE) are two rare sequelae of central nervous system (CNS) infections (1, 42). SSPE is invariably fatal and occurs an average of 8 years after the acute infection. There is no evidence to suggest that a variant virus is involved in the primary infection, nor has any vaccine virus has been implicated in the establishment of SSPE. The virus appears to persist in the body at an unknown site (37). In SSPE, CNS infection develops in the presence of high titers of antiviral antibodies, and the isolated viruses are defective in budding (12). Mutations accumulate in the virus genome, especially in the fusion and matrix genes, and transcription of envelope genes is reduced by an altered transcription gra...

Knowledge of the mechanisms of virus dissemination in acute measles is cursory, but cells of the monocyte/ macrophage (MM) lineage appear to be early targets. We characterized the dissemination of the Edmonston B vaccine strain of measles virus (MV-Ed) in peripheral blood mononuclear cells (PBMC) of two mouse strains expressing the human MV-Ed receptor CD46 with human-like tissue specificity and efficiency. In one strain the alpha/beta interferon receptor is defective, allowing for efficient MV-Ed systemic spread. In both mouse strains the PBMC most efficiently infected were F4/80-positive MMs, regardless of the inoculation route used. Circulating B lymphocytes and CD4-positive T lymphocytes were infected at lower levels, but no infected CD8-positive T lymphocytes were detected. To elucidate the roles of MMs in infection, we depleted these cells by clodronate liposome treatment in vivo. MV-Ed infection of splenic MM-depleted mice caused strong activation and infection of splenic dendritic cells (DC), followed by enhanced virus replication in the spleen. Similarly, depletion of lung macrophages resulted in strong activation and infection of lung DC. Thus, in MV infections of genetically modified mice, blood monocytes and tissue macrophages provide functions beneficial for both the virus and the host: they support virus replication early after infection, but they also contribute to protecting other immune cells from infection. Human MM may have similar roles in acute measles.