3型固有淋巴样细胞在柯萨奇病毒B3型诱导的病毒性心肌炎发病中的作用及其机制

Viral myocarditis, mostly caused by coxsackievirus B3 infection, is characterized by myocardial inflammation with unclear pathogenesis. Innate lymphoid cells (ILCs) are recently identified members of the lymphoid lineage that have emerging roles in infection, inflammation and metabolic diseases, but its impact on viral myocarditis is unknown. Our previous study showed the daynamic discordance of IL-17 expression and Th17 induction, indicative of exist of IL-17-producing innate cells. Meanwhile, we found the enrichment of splenic ILC3 (CD3-RORγt+ ) in CVB3-infected mice, which was positively associated with myocarditis severity.Considering that ILC3 as a main innate cell souce of IL-22/IL-17 lacks PRR for CVB3 sensing and could cross-talk with other innate cells; meanwhile macrophages,enriched in TLR and are activated by CVB3 stimulation, play an important role in CVB3-induced myocarditis, therefore, we raise the following scientific hypothesis:by stimulating TLRs, CVB3 induces macrophage to produce pro-inflammatory cytokines like IL-23 or IL-1β, which promotes ILC3 to produce IL-22/IL-17/IFN-γand then modulate the subsequent adaptive Th1/Th17 cell immune response and aggravate viralmyocarditis. Our study may not only help understanding the influence of ILCs onthe pathogenesis of viral myocarditis, but also provide potential target for the novel therapeutic strategy based on ILCs modulation.

固有淋巴细胞（ILCs）是一类新近发现的重要固有免疫应答细胞，在多种感染、炎症性疾病中扮演重要角色，但其在病毒性心肌炎中的作用尚不明了。我们前期研究发现柯萨奇病毒B3型（CVB3）诱导的心肌炎小鼠模型中IL-17存在固有免疫细胞来源。同时，脾脏3型ILCs（ILC3, CD3-RORγt+）比例显著升高，清除后可显著改善心肌炎症和心脏功能，提示ILC3参与心肌炎发病。鉴于ILC3是IL-22/IL-17的重要细胞来源，但缺乏感知CVB3的TLR，而富含TLR的巨噬细胞在心肌炎时异常活化并参与发病，因此我们提出科学假设：CVB3通过TLR-MyD88通路刺激巨噬细胞分泌细胞因子如IL-23/IL-1β，后者通过JAK-STAT通路促进ILC3细胞分泌效应性因子IL-22/IL-17/IFN-γ，启动和维持机体固有应答促炎微环境的同时，推动和扩大后续病理Th17/Th1应答，加重心肌炎症损伤。

柯萨奇病毒B3型（CVB3）诱导的病毒性心肌炎是一类临床常见心血管疾病，其发病机制不清。本研究探讨了固有免疫应答细胞3型固有淋巴样细胞（ILC3）在CVB3心肌炎发病的作用。发现在感染早期（第3天）肠道局部ILC3比例显著增加，并与病情发展高度相关。与对照小鼠相比，ILC3缺失小鼠感染组织（肠道和心脏）病毒载量显著增加，心肌病理学改变加重，且生存率显著降低。进一步研究发现，ILC3主要通过效应分子IL-22而非IL-17控制病毒复制。通过RNAseq分析了ILC3缺失小鼠与对照组感染肠道上皮组织中的差异基因，发现其参与免疫应答和炎症应答的共同差异基因中改变最明显的为IL-1β和IL-18，另外检测炎症小体感受器差异性表达时发现下调最明显的为NLRP3。在ILC3缺失小鼠感染肠道组织，我们同样检测到显著下调的NLRP3表达、明显抑制的下游分子cleaved caspase-3以及效应分子IL-1β和IL-18。应用NLRP3激动剂可显著促进CVB3感染肠道上皮细胞HT-29和心肌细胞HL-1内病毒清除，表明IL-22主要通过活化炎症小体NLPR3通路抑制病毒复制。探讨其相关分子机制时，我们发现，IL-22主要通过其受体下游STAT3，而非STAT1,STAT5或者MAPK显著抑制病毒载量。本研究不仅阐明了固有细胞ILC3保护病毒性心肌炎的分子机制，同时也解析了IL-22促进NLRP3活化进而显著抑制病毒复制的分子免疫学机制，为病毒性心肌炎发病机理阐明和治疗策略的研制提供了新思路。