KIR/HLA复合基因在隐匿性乙肝免疫逃逸中的机制研究

The lack of serological marker and low viremia caused by occult hepatitis B virus infection (OBI) mainly lead to clinical misdiagnosis and missed diagnosis. Previous study on OBI is only limited in specific population. Therefore, there were only four hypothesises on the pathogenesis of OBI. In Xi'an Regional Blood transfusion Center, we have the blood sample of the large size of the healthy blood donors and diagnostic reagent which is more sensitivity than the clinical diagnostic reagents. Our preliminary study identified the fact a certain percentage of OBI patients exist in 'healthy blood donor' which is the basis for our OBI-related research. On the other hand, a large amount of studies have shown that the polymorphisms of HLA and KIR genes are associated with the immune pathogenesis of many diseases. So we believe that the lack of immune markers in OBI should be associated with immune tolerance which is tightly linked with host genetic background. Then we suppose the proposed interaction between KIR and cognate HLA ligand should affect NK cell activity and eventually lead to the OBI occurrence. In this study, firstly, we use the high sensitivity of nucleic acid testing reagent to test blood sample in large size of healthy blood donors to investigate the incidence and the epidemiological situation of OBI. Secondly, we study the KIR and HLA genotype in OBI patients and other control groups. Thirdly, we test and analyze the function of NK cell. Our aim is to provide a new basis for the pathogenesis of OBI and provide new ideas for the early diagnosis and treatment of OBI.

缺乏血清学免疫标志、以及低病毒血症是造成隐匿性乙型肝炎病毒感染（OBI）临床误诊、漏诊的主要原因。陕西省血液中心具有大样本量的健康人群血样，诊断试剂敏感性远远高于临床的优势，而且在前期研究结果确定了一定比例的存在于"健康献血人群"中，为确保临床安全用血，对OBI进行研究就非常重要和迫切。大量研究显示HLA和KIR的多态性与多种疾病的免疫发病机制相关。我们认为OBI缺乏免疫标志可能与免疫逃逸有关，并从宿主遗传背景为出发点，提出KIR及同源性HLA配体之间的相互作用进而影响NK细胞活性引起免疫逃逸，最终导致OBI发生。本研究拟采用高灵敏度的核酸检测试剂，率先以大样本量普通人群为研究对象，调查OBI的发病率及流行病情况；对OBI及其他HBV感染状态的患者及对照人群进行KIR和HLA分型；检测分析其外周血NK细胞功能。为OBI的发病机制提供新的依据，为临床OBI早期诊断、筛查以及治疗提供新的思路。

研究背景 研究表明OBI有通过血液传播HBV的风险。缺乏血清学免疫标志、低病毒血症是造成OBI临床误诊、漏诊的主要原因，为确保临床安全用血，对OBI进行研究非常重要。.研究内容 以2013年在陕西省血液中心捐献血液的健康献血者为研究对象，进行HBV DNA检测，对其中诊断为OBI者进行流行病学调查及随访，了解OBI的最终疾病转归。对OBI患者及正常对照人群进行KIR和HLA分型。分析KIR/HLA基因型与OBI的相关性。.重要结果、关键数据 .1..获得OBI在大样本健康人群中的发病率为0.0648%。.2..在107个OBI个体中，研究发现了47人是AA基因型（43.93%），60人为AB基因型（56.07%）。发现了22种基因组合型。KIR 2DL1、KIR 2DS4和 KIR 2DS5在OBI人群和正常人群的比较中有显著性差异。.3..在OBI人群中分别发现20、43、24、33和18个HLA-A 、B、C、DRB1和DQB1等位基因，其中HLA-C*0701，HLA-DQB1*0301，HLA-DRB1*1101，HLA-DRB1*1501在OBI人群和正常人群的比较中有显著性差异。.4..在OBI人群中有8个HLA A-B- Cw- DRB1- DQB1单倍型在OBI人群和正常人群的比较中有显著性差异。7个HLA A-B- Cw- DRB1单倍型在OBI人群和正常人群的比较中有显著性差异，24个HLA A-B单倍型在OBI人群和正常人群的比较中有显著性差异。其中HLA A*3303 B*4403 Cw*0701 DRB1*0701 DQB1*0202，HLA A*0201 B*1511 Cw*0303 DRB1*0901 DQB1*0303，HLA A*3201 B*4403 Cw*0401 DRB1*0701 DQB1*0202仅出现在OBI人群中。.科学意义：研究表明KIR抑制基因为人类NK细胞最主要的抑制基因家族，它与HLA I 类分子结合的抑制性受体是NK细胞对正常细胞耐受的关键所在。我们的研究初步探讨了KIR及HLA在隐匿性乙型肝炎患者中的遗传学特点，显示OBI患者中KIR某些基因和HLA某些基因及单倍型与正常人群的比较中有显著性差异，这些是否是OBI的易感基因、易感单倍型或是抗OBI的保护基因、保护单倍型还有待我们的进一步研究确证