Towards an in vitro model for acute hemorrhagic conjunctivitis: Cytokine-mediated vascular endothelial cell activation triggered by enterovirus type 70 infection

Background: Little is known of the pathogenetic mechanisms of enterovirus type 70 (EV70), a causative agent of acute hemorrhagic conjunctivitis. However, virus- or cytokine-induced perturbation of vascular endothelial cells are potential triggering events. Objective: To determine whether EV70 infection of human umbilical vascular endothelial cells (HUVECs) and human corneal epithelial cells (HCEs) causes the release of vasoactive cytokines, capable of triggering vascular endothelial cell activation. Study design: Susceptibility of cultured HUVECs and HCEs to EV70 was tested by observing the appearance of cytopathic effect or immunoprecipitation of viral protein in infected cells. The culture fluids from the virus-infected cells were tested for their ability to stimulate the expression of intercellular adhesion molecule-1 (ICAM-1) on uninfected HUVECs. Anti-cytokine antibodies were used to identify ICAM-1-activating cytokine(s). Results: Both HUVECs and HCEs were susceptible to EV70 infection. Culture fluids from EV70-infected HUVECs and HCEs stimulated ICAM-l expression on uninfected HUVECs, which was completely blocked by anti-interleukin-1α (IL-1α) antibody but not by interleukin-1β (IL-1β) or anti-tumor necrosis factor α (TNFα) antibodies. Conclusion: This study provides the first evidence of EV70 infection of both HCEs and HUVECs, and furthermore, identifies IL-1α as the predominant endothelial cell-activating factor produced by EV70-infected cells. Since endothelial cell activation is often an initiating step towards vascular permeability and/or inflammation, the perturbation of endothelial cell function through EV70 induced IL-1α is thus a potential contributory factor in the pathogenesis of EV70-associated hemorrhagic conjunctivitis.