探討自體吞噬泡及單核細胞趨化蛋白-1 之產生在登革病毒感染致病機轉角色

Dengue virus infection may cause self-limited dengue fever (DF), dengue hemorrhagic fever (DHF), and dengue shock syndrome (DSS). The viral load is the key point of the pathogenesis of dengue virus infection. Moreover, vascular leakage, thrombocytopenia and hemoconcentration are the hallmarks of dengue hemorrhage fever (DHF) and dengue shock syndrome (DSS). Permeability aberration may contribute to the plasma leakage, which is most likely affected by certain soluble mediators. Cytokines may play an important role in the vascular leakage. Autophagy, a cellular response against stresses, functions to recycle protein and organelles. However, the roles of autophagy in disease pathogenesis and microbial infection remain unclear. Several viral infections could induce autophagy and replicate using the autophagosome. We found that dengue virus-2 (DV2) infection can induce punctate GFP-microtubule-associated protein light chain (GFP-LC3) and increased expression of the proteolytic derivate LC-II in DV2 infected cells. DV2 infection induced autophagosome formation revealed by immuno-gold labeling of LC3 protein under the transsimission electron microscopy. The mTOR/p70S6K signaling pathway may be involved in DV2-induced autophagy. Further study reveals that DV2 infection-induced autophagy can enhance the replication of the virus in the infected cells. Furthermore, high levels of monocyte chemoattractant protein-1 (MCP-1) were detected in the plasma of DHF patients. DV2 infection can induce MCP-1 production in monocytes, but not in hepatoma and endothelium cells. The production of MCP-1 is dengue virus-dose dependent. Exposure of human umbilical vein endothelial cells (HUVEC) to recombinant human MCP-1 (rhMCP-1) or the cultured supernatant of DV2-infected human monocytes increased vascular permeability of HUVECs. Neutralizing monoclonal antibody of MCP-1 partially reduced vascular permeability. The distribution of the tight junction protein ZO-1 on the cellular membrane of HUVEC was disrupted either by pretreatment of recombinant MCP-1 or the conditioned medium from DV2-infected monocytes. All together, we unravel that dengue virus infection can induce autophagosome formation and increase viral replication. Moreover, increased viral load sustains the overexpression of MCP-1, which further increases the degree of the vascular permeability. Our findings open a new direction toward understanding the pathogenesis of DHF.