Human macrophages differentiated in the presence of vitamin D₃ restrict dengue virus infection and innate responses by downregulating mannose receptor expression

Background Severe dengue disease is associated with high viral loads and overproduction of pro-inflammatory cytokines, suggesting impairment in the control of dengue virus (DENV) and the mechanisms that regulate cytokine production. Vitamin D3 has been described as an important modulator of immune responses to several pathogens. Interestingly, increasing evidence has associated vitamin D with decreased DENV infection and early disease recovery, yet the molecular mechanisms whereby vitamin D reduces DENV infection are not well understood. Methods and principal findings Macrophages represent important cell targets for DENV replication and consequently, they are key drivers of dengue disease. In this study we evaluated the effect of vitamin D3 on the differentiation of monocyte-derived macrophages (MDM) and their susceptibility and cytokine response to DENV. Our data demonstrate that MDM differentiated in the presence of vitamin D3 (D3-MDM) restrict DENV infection and moderate the classical inflammatory cytokine response. Mechanistically, vitamin D3-driven differentiation led to reduced surface expression of C-type lectins including the mannose receptor (MR, CD206) that is known to act as primary receptor for DENV attachment on macrophages and to trigger of immune signaling. Consequently, DENV bound less efficiently to vitamin D3-differentiated macrophages, leading to lower infection. Interestingly, IL-4 enhanced infection was reduced in D3-MDM by restriction of MR expression. Moreover, we detected moderate secretion of TNF-α, IL-1β, and IL-10 in D3-MDM, likely due to less MR engagement during DENV infection. Conclusions/Significance Our findings reveal a molecular mechanism by which vitamin D counteracts DENV infection and progression of severe disease, and indicates its potential relevance as a preventive or therapeutic candidate.【背景】 重症登革热与高病毒载量及促炎细胞因子过度产生相关，这提示机体对登革病毒（Dengue virus, DENV）的控制以及细胞因子产生调控机制存在缺陷。维生素D3已被证实是多种病原体免疫应答的重要调节因子。值得关注的是，越来越多的证据表明维生素D与登革病毒感染率降低及疾病早期康复相关，但维生素D降低登革病毒感染的分子机制尚未完全阐明。 【材料与方法及主要研究结果】 巨噬细胞是登革病毒复制的重要靶细胞，因此也是重症登革热的关键驱动因素。本研究评估了维生素D3对单核细胞衍生巨噬细胞（monocyte-derived macrophages, MDM）分化的影响，以及这些巨噬细胞对登革病毒的易感性与细胞因子应答情况。研究数据显示，在维生素D3存在环境下分化的MDM（D3-MDM）可限制登革病毒感染，并调节经典炎症细胞因子应答。从机制层面而言，维生素D3诱导的巨噬细胞分化可降低C型凝集素的表面表达，其中包括甘露糖受体（mannose receptor, MR, CD206）——该受体已被证实可作为登革病毒附着于巨噬细胞的主要受体，并触发免疫信号通路。因此，登革病毒与维生素D3诱导分化的巨噬细胞结合效率降低，进而导致感染水平下降。值得注意的是，白细胞介素4（Interleukin-4, IL-4）诱导的感染增强效应在D3-MDM中可通过抑制甘露糖受体的表达得到削弱。此外，我们在D3-MDM中检测到肿瘤坏死因子α（Tumor necrosis factor-α, TNF-α）、白细胞介素1β（Interleukin-1β, IL-1β）与白细胞介素10（Interleukin-10, IL-10）的分泌水平适中，这可能是因为登革病毒感染过程中甘露糖受体的结合事件减少所致。 【结论与意义】 本研究揭示了维生素D对抗登革病毒感染并延缓重症疾病进展的分子机制，同时表明其有望成为预防或治疗登革热的潜在候选方案。