Abstract
Dengue hemorrhagic fever and/or dengue shock syndrome represent the most serious pathophysiological manifestations of human dengue virus infection. Despite intensive research, the mechanisms and important cellular players that contribute to dengue disease are unclear. Mast cells are tissue-resident innate immune cells that play a sentinel cell role in host protection against infectious agents via pathogen-recognition receptors by producing potent mediators that modulate inflammation, cell recruitment and normal vascular homeostasis. Most importantly, mast cells are susceptible to antibody-enhanced dengue virus infection and respond with selective cytokine and chemokine responses. In order to obtain a global view of dengue virus-induced gene regulation in mast cells, primary human cord blood-derived mast cells (CBMCs) and the KU812 and HMC-1 mast cell lines were infected with dengue virus in the presence of dengue-immune sera and their responses were evaluated at the mRNA and protein levels. Mast cells responded to antibody-enhanced dengue virus infection or polyinosiniċpolycytidylic acid treatment with the production of type I interferons and the rapid and potent production of chemokines including CCL4, CCL5 and CXCL10. Multiple interferon-stimulated genes were also upregulated as well as mRNA and protein for the RNA sensors PKR, RIG-I and MDA5. Dengue virus-induced chemokine production by KU812 cells was significantly modulated by siRNA knockdown of RIG-I and PKR, in a negative and positive manner, respectively. Pretreatment of fresh KU812 cells with supernatants from dengue virus-infected mast cells provided protection from subsequent infection with dengue virus in a type I interferon-dependent manner. These findings support a role for tissue-resident mast cells in the early detection of antibody-enhanced dengue virus infection via RNA sensors, the protection of neighbouring cells through interferon production and the potential recruitment of leukocytes via chemokine production.
Highlights
Mast cells are well known for their classical role in inflammation and allergy but recent evidence has highlighted that their immune functions have much broader reaching implications [1,2,3,4,5,6,7,8]
While the influence of CCL4 and CCL5 on the overall immune response to dengue virus infection is not well studied, clinically these chemokines are decreased in serum of dengue hemorrhagic fever patients, and their levels may serve as good prognostic factors for disease outcome [14,15]
To more fully elucidate mast cell interactions with dengue virus, we used a Quantitative PCR (qPCR) array to broadly evaluate the genes upregulated by primary human cord blood-derived mast cells (CBMCs) in response to antibody-enhanced dengue virus infection
Summary
Mast cells are well known for their classical role in inflammation and allergy but recent evidence has highlighted that their immune functions have much broader reaching implications [1,2,3,4,5,6,7,8]. Our studies involving mast cell responses to antibody-enhanced dengue virus infection have highlighted potent immunoregulatory activities of these cells, including secretion of tumor necrosis factor [9] and the chemokines CC chemokine ligand (CCL), CCL4 and CCL5 [10,11] These studies, in addition to other published reports [4,6,12,13], reinforce the role of mast cells as innate immune effectors in response to virus infection. These studies provide insight into the diversity of signals generated in response to active virus infection or viral components, which can influence the mode/action of antiviral activity. While the influence of CCL4 and CCL5 on the overall immune response to dengue virus infection is not well studied, clinically these chemokines are decreased in serum of dengue hemorrhagic fever patients, and their levels may serve as good prognostic factors for disease outcome [14,15]
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