Infection of mouse bone marrow-derived dendritic cells by live attenuated Japanese encephalitis virus induces cells maturation and triggers T cells activation

An attenuated Japanese encephalitis virus (JEV) strain SA14-14-2, generated from the wild strain SA14, is an effective live vaccine against JEV infection. It has led to a significant decrease in JEV infection around the world. Although it is highly effective, the mechanism for its robust immunity was not well investigated. In this study, the interaction of SA14-14-2 with bone marrow-derived dendritic cells (bmDCs) was investigated. Our results showed that the infection of bmDCs with SA14-14-2 resulted in viral replication and upregulation of bmDC maturation marker molecules (CD40, CD80, CD83 and MHC I). SA14-14-2 infection also stimulated the production of interferon-α (IFN-α), monocyte chemoattractant protein-1 (MCP-1/CCL2), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) of bmDC. Both MLR and ELISPOT assay showed an enhanced allostimulatory capacity of SA14-14-2-infected bmDCs. Furthermore, the SA14-14-2-infected bmDCs impaired the expansion of Foxp3+ regulatory T (Treg) cells with immunosuppressive potential, suggesting that SA14-14-2 infection induced antiviral immunity rather than immunosuppression. Taken together, our results indicated that SA14-14-2 infection caused bmDC maturation, changed the expression profiles of several cytokines, and triggered T cell activation. This offered an insight in the immunologic mechanisms associated with the high efficiency of the SA14-14-2 vaccine.