Respiratory syncytial virus impairs T cell activation by preventing synapse assembly with dendritic cells

Respiratory syncytial virus (RSV) infection is one of the leading causes of infant hospitalization and a major health and economic burden worldwide. Infection with this virus induces an exacerbated innate proinflammatory immune response characterized by abundant immune cell infiltration into the airways and lung tissue damage. RSV also impairs the induction of an adequate adaptive T cell immune response, which favors virus pathogenesis. Unfortunately, to date there are no efficient vaccines against this virus. Recent in vitro and in vivo studies suggest that RSV infection can prevent T cell activation, a phenomenon attributed in part to cytokines and chemokines secreted by RSV-infected cells. Efficient immunity against viruses is promoted by dendritic cells (DCs), professional antigen-presenting cells, that prime antigen-specific helper and cytotoxic T cells. Therefore, it would be to the advantage of RSV to impair DC function and prevent the induction of T cell immunity. Here, we show that, although RSV infection induces maturation of murine DCs, these cells are rendered unable to activate antigen-specific T cells. Inhibition of T cell activation by RSV was observed independently of the type of TCR ligand on the DC surface and applied to cognate-, allo-, and superantigen stimulation. As a result of exposure to RSV-infected DCs, T cells became unresponsive to subsequent TCR engagement. RSV-mediated impairment in T cell activation required DC-T cell contact and involved inhibition of immunological synapse assembly among these cells. Our data suggest that impairment of immunological synapse could contribute to RSV pathogenesis by evading adaptive immunity and reducing T cell-mediated virus clearance.