维生素D及其代谢通路遗传变异在HCV感染及慢性化中的作用及其机制研究

Accumulating evidence suggest that vitamin D is an important immune system regulator, and the effects of vitamin D on the regulation of T helper (Th) cells immune responsiveness are closely related with human anti-hepatitis C virus (HCV) immune response. Vitamin D metabolism is a complex process, which requires the participation of multiple genes. And these vitamin D metabolism genes can influence circulating vitamin D level. We speculate that the genetic variation of these genes may regulate the expression and function of vitamin D and then influencing the replication, spontaneous clearance and outcomes of HCV. There is little information available about the associations of genetic variations in vitamin D metabolic pathway and vitamin D level with HCV infection outcomes as well as gene-gene and gene-environment interactions. On this basis, we designed a population-based case-control and case-case study with large sample size. The relationships would been systemically evaluated between genetic variations in vitamin D metabolic pathway, serum vitamin D level and HCV infection susceptibility and chronicity in Chinese population. And gene-gene and gene-environmental interactions between genetic variants and related risk factors would also been detected. In addition, functional studies are also carried out to explore the biology mechanisms of the relevant genetic variations of susceptibility genes (such as VDR, GC and CYP450). The results of this project will enable us more thoroughly to comprehend the immunologic mechanism in the development and progression of HCV infection, which in turn is important for screen high-risk population, prevention and individualized treatment of HCV infection.

大量研究证明，维生素D（Vitamin D, VD）具有调节免疫系统的功能，尤其对Th细胞免疫应答的调节效应在机体丙型肝炎病毒（hepatitis C virus, HCV）感染的抗病毒免疫应答中发挥着不可忽视的作用。VD在体内代谢需要多个基因的共同参与，这些关键基因是影响血清VD水平的重要因素，其遗传变异可能通过干扰VD的免疫调节功能而影响HCV的复制、自限清除及感染转归。迄今很少有涉及VD代谢通路上多基因联合效应以及与VD水平间交互效应与HCV感染结局关系的研究。基于以上背景，本课题采用大样本病例-对照和病例-病例研究设计，分析VD代谢通路遗传变异与HCV感染易感性及慢性化的关系以及基因-基因和基因-环境间的交互作用，并结合生物学功能研究探讨相关遗传变异在HCV感染转归中的作用及可能的机制，为阐明HCV感染转归的免疫学机制提供新思路，为HCV高危人群的筛查、预防及个体化治疗提供依据。

丙型肝炎病毒（hepatitis C virus, HCV）感染在全球范围内仍是一个重要公共卫生问题，易慢性化。大量研究证明维生素D（Vitamin D, VD）具有调节免疫系统的功能，在HCV感染转归及其抗病毒免疫应答中发挥着重要作用，而VD代谢通路中多个关键基因（VDR、VDBP、CYP2R1、CYP27A1、CYP27B1、CYP24A1）是影响血清VD水平的重要因素。本项目基于以上背景和既往研究基础，结合病例对照研究和分子生物学技术，从群体和分子水平探讨VD水平及其代谢通路基因遗传变异在HCV感染转归中的作用及可能机制。结果显示：1、血浆25(OH)D水平、年龄、性别、基因特征等因素与HCV感染及肝功能状况有关。2、VDR rs757343-A、rs739837-A、s7975232-C、rs2239185-T、rs11574129-T等位基因可降低HCV感染易感性，且存在联合作用，生物信息学分析发现位于3’-UTR区的rs11574129突变可能通过影响VDR的转录进而影响其蛋白表达。3、VDBP rs7041-G和rs3733359-T等位基因可增加HCV感染风险，且存在联合作用，同时rs7041-GT/GG和rs3733359-CT/TT间交互作用可增加HCV感染风险。4、CYP2R1 rs12794714-G、rs10741657-A、rs1562902-C、rs10766197-G等位基因可增加HCV感染风险，且存在联合作用；CYP24A1 rs6013897-A等位基因亦可增加HCV感染风险，携带rs3787557-C、rs6022999-G、rs2248359-T等位基因者更易进展为慢性化，而携带rs6068816-T等位基因者更易清除病毒；生物信息学功能分析显示以上位点变异可能通过改变多个转录调节模体或干扰蛋白质结合活性调节基因表达和转录从而影响VD代谢水平及HCV感染转归。5、维生素D对HCV感染转归的影响可能是通过调节免疫系统来发挥作用的，课题组还参与研究发现，HLA相关基因（HLA-II类分子、非经典基因LMP7和TAP2）和免疫相关细胞因子基因（IL28B、IFNL4和CXCR6）遗传变异与HCV感染转归或抗病毒治疗应答有关。以上结果均在中国高危人群中首次发现，为阐明HCV感染转归的免疫学机制提供新思路，为高危人群筛查与防治提供参考。