Role du recepteur de chimiokine CCR3 dans l'infection du virus respiratoire syncytial

Respiratory syncytial virus (RSV) is an important cause of lower respiratory tract illness in infants and has been associated with the development of asthma. Currently no safe and efficacious RSV vaccine is available. Understanding of the biological mechanisms behind an RSV infection can have important implications for strategies aimed at preventing lower respiratory tract infection. Besides its role in the initiation of a new infection cycle, the surface envelope glycoprotein G (gp90) appears to be linked to the pathogenesis of RSV disease. It has been linked to excessive production of chemokine, cytokines, airways eosinophilia and accumulation of Th2 cells in the lungs. It is not clearly understood how RSV-G protein induces these diverse effects. The objective of this proposal is to improve our understanding of gp90 in bronchiolitis. The general hypothesis is that gp90 mimics chemokine activity and that the initiation of RSV infection is mediated by the interaction between gp90 and chemokine receptors.;Given the role of CCR3 in RSV pathogenesis, three strategies were tested to prevent RSV infection. (1) Penetration of RSV in the cell is blocked by the natural ligand (eotaxin) of CCR3. RSV infection of epithelial cells is inhibited by pre-treatment with recombinant human eotaxin or neutralizing anti-CCR3 antibody. (2) Prevention of gp90 attachment was obtained by cleaving CCR3 by metalloproteinases (MMP). MMP constitute a multigene family of over 25 secreted endopeptidases, they have the capacity to degrade chemokine receptors, in particular CCR3. Using Western blot and flow cytometric analysis, we report in this study that MMP7 cleaves CCR3 and prevents the binding of eotaxin to its receptor. The cleavage of CCR3 was also reflected in a loss of chemoattractant activity for eosinophils and GHOST/CCR3 cells. In addition, treatment of epithelial cells with MMP7 inhibited infection with RSV. (3) Finally, CCR3 expression is decreased by glucocorfcoides treatment. Pretreatment of the airway epithelial cells line Hep-2with ftuticasone proprionate (FP) at a concentration of 10-7 M decreased viral plaque formation. Moreover, significant inhibition of CCR3 expression was observed when the cells were treated with the 10-7 M FP solution.;Our data offers multiple strategies for inhibiting RSV interaction with CCR3 such as its decreased cell surface expression by corticosteroids, its blockade by eotaxin, as well as being cleaved by MMP. These could offer a basis for pharmacological intervention in bronchiolitis and asthma exacerbation caused by RSV.;Keywords: Respiratory syncytial virus, Glycoprotein G, Chemokine, Chemokine receptor, Metalloprotease, Corticosteroide.;First, we investigated the contribution of CCR3, a chemokine receptor constitutively expressed on epithelial cells, eosinophils and Th2-type cells, in RSV infection. Indeed, gp90 forms a physical association with CCR3 and prevents the chemokine eotaxin from binding to it. In addition, an anti-CCR3 antibody partially inhibits migration of eosinophils and Th2 cells induced by gp90. Thus, this interaction may contribute to the accumulation of eosinophils and Th2 cells characteristically found in the airways of children with RSV-induced bronchiolitis.