人类基因多态性与移植后巨细胞病毒感染相关性研究进展

魏巴金 周琳

·综述·

人类基因多态性与移植后巨细胞病毒感染相关性研究进展

魏巴金1, 2周琳1

CMV是一种疱疹DNA病毒，一般正常人群可以携带，但不引起临床症状。移植后合并CMV感染在供者CMV阳性而受者CMV阴性(D+/R-)时发生率较高，轻者可能引起轻微无症状感染，重者可能引起严重器官功能衰竭甚至死亡。常见的预防措施因为药物不良反应和经济问题而无法全面应用。在过去的10年里，有很多探讨人类基因多态性和移植后CMV感染、再燃和相关组织疾病等之间关系的研究，但结果并不一致。本文系统地阐述了目前人类基因多态性与移植后CMV感染的相关性研究，并根据移植类型(包括肝移植、肾移植、心肺移植、造血干细胞移植和实体器官移植)，有助于掌握目前的研究进展，为未来研究方向提供一定的参考。

基因多态性； 巨细胞病毒； 移植

移植术后出于保护移植物的需要，往往需要人为降低受者本身的免疫系统功能应答，增加了许多病毒、细菌、真菌等感染的风险。CMV是一种疱疹DNA病毒，一般正常人群可以携带，但不引起临床症状。移植术后CMV感染在供者CMV阳性而受者阴性(D+/R-)时发生率较高，轻者可能引起轻微无症状感染，重者可能引起严重器官功能衰竭甚至死亡[1-2]。目前，CMV感染及其发病机制尚不明确，常见的预防措施有移植术前预防性使用药物，但这不仅加重了患者负担，而且存在白细胞、血小板减少和发热等不良反应[1, 3]。

人类基因多态性是进化的动力，但也为疾病的治疗带来了一定困难。目前研究表明，人类基因多态性对移植受者术后CMV易感性、CMV感染临床表现的多样性以及对药物治疗的反应上都起着重要作用；人类基因多态性与移植术后CMV感染的相关性研究对认识该疾病的发病机制、预测转归等方面有重要作用。如何精准地使用抗病毒药物，实现个体化治疗，已成为移植领域的一大研究热点。

1 肝移植

2007年，Kijpittayarit等[4]首先报道，与不具有Toll样受体2(toll-like receptor 2，TLR2)位点rs5743708基因多态性的肝移植受者相比，具有该位点基因多态性的纯合子和杂合子具有更高的CMV DNA复制量，且单因素分析指出其是CMV病的危险因素；但在多因素分析中，通过对年龄、急性排斥反应、感染状态等因子校正后，二者相关性存在不确定性。2012年，另一项涉及737例肝移植受者的研究却指出，TLR2(位点rs5743708)纯合子基因型的受者术后组织侵袭性CMV病的发生率升高[5]。无论供者或受者术前是否存在CMV感染，供者甘露糖结合凝集素(mannose-binding lectin，MBL)和胶原凝集素2基因多态性可以独立预测CMV感染，特别是在供者CMV阴性而受者阳性(D-/R+)情况下预测作用更佳，结合供、受者基因型不一致状态可以增加预测能力[6]。在活体肝移植中，细胞色素P450 3A5(cytochrome P450 3A5，CYP3A5)表达型肝移植受者发生CMV和细菌感染的可能性和ImmuKnow检测免疫细胞功能的结果明显高于非表达型[7]。IL28B(位点rs12979860)基因多态性被证实不仅对急性排斥反应有影响，而且与CMV的再燃也有相关性[8]。

2 肾移植

法国一项研究指出，如果将具有TLR4位点rs4986790和rs4986791任何变异型的肾移植受者定义为变异型携带者，与野生型携带受者相比，CMV感染可能会有较高，但结果差异不具有统计学意义[9]。白介素家族成员基因多态性与CMV感染的关联也有较多相关研究。供者IL10位点rs1800896 AA基因型可以降低受者术后CMV感染率并延迟感染发生时间，受者该基因型基因多态性则与是否感染CMV没有关系[10]。法国Hoffmann等[11]另一项研究发现，经过多因素分析，具有IL12位点rs3212227等位基因C可以增加CMV感染，这种相关性在移植前CMV阳性且未接受预防性治疗的受者中更加明显。在接下来的实验中，虽然未能验证IL12位点rs3212227基因多态性和肾移植术后急性排斥反应、慢性移植物失功和移植物生存有关，却再次发现具有位点rs3212227等位基因C受者发生CMV感染的风险增加[12]。进一步研究PD-1基因多态性与CMV感染的关系，Hoffmann等[13]还发现该基因位点rs11568821等位基因A与IL12基因3-UTR区域的基因多态性相比，具有更好的预测CMV感染的能力。具有IL28B位点rs12979860等位基因T的肾移植受者CMV感染风险降低34%，在术前不采取预防措施的亚组分析中，TLR9位点rs5743836 TT基因型同样被发现对CMV感染具有保护作用，而树突状细胞特异性细胞黏附分子-3结合非整合素因子(dendritic cell specific intercellular-adhesionmolecule-3 grabbing non-integrin，DC-SIGN)位点rs735240GG基因型却被视为危险因素[14]。有关细胞因子IFN-γ(位点rs2430561)单因素分析表明，相对于TT基因型，AA基因型携带者CMV感染风险增加约3.4倍；多因素分析指出：D+/R-、位点rs2430561的基因多态性、急性排斥反应和使用抗胸腺细胞球蛋白诱导可以作为CMV感染的高危因素[15]。两项针对不同地区人群开展的研究同时指出，在中国西北部和印度肾移植受者中，HLA-G启动子一段14 bp的缺失会同时影响CMV感染和急性排斥反应的发生情况[16-17]。一项关于肾移植术后早期3个月受者CMV感染的研究指出，维生素D受体位点FokIff基因型携带者CMV病的发生率会升高[18]。相比无症状CMV感染患者，细胞毒性T淋巴细胞相关抗原4(cytotoxic T lymphocyte antigen-4，CTLA4)(位点rs231775和rs3087243)GG基因型在有症状的CMV感染患者中频率较高，它的存在可以使CMV感染出现症状的风险增加约2.5倍[19]。

3 心肺移植

IFN-γ位点rs2430561 TT基因型的肺移植受者不仅IFN-γ分泌增加，而且和CMV病发展相关，特别是在CMV阳性受者中更加明显，同时也降低了血CMV载量的峰值[20]。奥地利一项关于肺移植的研究中，研究人员发现人CMV特异性免疫球蛋白表达和移植后巨细胞病毒复制密切相关，并且通过测定44位患者的免疫球蛋白重链γ1的基因多态性，认为其影响人CMV特异性免疫球蛋白表达[21]。Gourley等[22]在心脏移植研究中发现，TNF-α、TNF-β、IL-6、IL-10、IFN-γ的基因多态性和CMV感染无相关性。

4 造血干细胞移植

德国一项针对43例造血干细胞移植受者的研究中，趋化因子受体5(chemokine receptor 5，CCR5)和IL10的基因多态性被认为和CMV病病情发展有关，而单核细胞趋化蛋白-1(monocyte chemotactic protein 1，MCP-1)则和CMV的再燃有关[23]。Corrales等[24]对102例西班牙造血干细胞移植受者的研究发现，虽然受者和供者CCR5(位点rs1800023)、MCP-1(位点rs13900)、IL-10(位点rs1878672)及TLR9(位点rs352140)基因多态性和CMV的活动性无明显联系，但是供者CCR5位点rs1800023 AA基因型携带者CMV血症和血浆中CMV DNA峰值持续时间较长。DC-SIGN基因启动子区域的(位点rs735240和rs2287886)基因多态性可以影响DC-SIGN基因的表达，从而影响树突状细胞对CMV的免疫作用，和CMV再燃、CMV病密切相关[25]。和肺移植、肾移植一样，行造血干细胞移植后IFN-γ的基因多态性和CMV病再发、高病毒载量有关，而CMV拷贝数高往往伴随宿主急性移植物排斥反应，并且预后较差[26]。供者CTLA4(位点rs3087243)的AA基因型更易在异基因造血干细胞移植的早期出现CMV感染以及反复发作，并且和预后呈现一定的相关性[27]。造血干细胞移植并出现过移植物排斥反应的受者，其共刺激分子中的CLTA4(位点rs4553808)和CD28(位点rs3116496)基因多态性与活动性CMV感染相关[28]。虽然造血干细胞移植受者和供者IL28B(位点rs8099917)基因多态性和活动性CMV感染无明显关联，但供者TT基因型会有较短的血CMV DNA持续时间[29]。在接受异基因造血干细胞移植的儿童白血病患者中拥有核转录因子FOXP3位点rs3761548的等位基因CC携带者CMV感染发生率较高，同时肝静脉闭塞性疾病风险也会提高，并且生存时间较短[30]。

5 实体器官移植

在检测MBL的3个功能基因多态性位点后，发现其单倍型全部为纯合子状态，和侵袭性CMV病密切相关，相比非纯合子受者，发生该疾病的风险提高了约6倍[31]。D+/R-实体器官移植受者IL28B位点rs8099917 TT基因型携带者会有较高的CMV DNA复制量，并且体外实验证明，该位点在CMV的刺激下会影响IL28B的表达[32]。IL28B基因可以编码IFN，IFN基因位点rs368234815多态性包括基因型TT/TT、基因型-G/-G及二者的杂合子，基因型-G/-G携带者CMV DNA复制量更高，在供者CMV阳性的受者中尤为明显[33]。MCP-2分泌和器官移植后CMV感染密切相关，且停止预防性用药后，在MCP-2启动子区域位点rs3138035 TT基因型的D+/R-受者群体中会出现CMV复制[34]。

6 总 结

目前有关人类基因多态性和移植后CMV感染的相关研究主要集中在细胞因子(如IL和IFN家族等)，样本量相对较少，取得的结果存在一定的局限性，尚不能大规模应用于临床。特别是存在相同基因位点在不同的移植研究中出现不同结果，可能是由各种族和疾病评判标准的差异引起，需要进一步的荟萃分析等手段来增加证据的信度。此外，基因多态性检测费用虽然较以前有大幅度的下降，但广泛应用于临床尚有一定的距离。可以预见基因多态性会在临床个体化治疗应用中发挥重要作用。随着中国人体器官分配与共享系统等相关协作登记制度的完善，开展大规模人群研究的障碍逐步减少，基因多态性的检测技术也日新月异，未来多中心、大样本试验将会陆续开展。

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(本文编辑：徐小明)

魏巴金, 周琳. 人类基因多态性与移植后巨细胞病毒感染相关性研究进展[J/CD]. 中华移植杂志: 电子版, 2016, 10(1):45-48.

Progress on the association between human gene polymorphisms and cytomegalovirus infection after transplantation

WeiBajin1,2,ZhouLin1.1KeyLaboratoryofOrganTransplantation,2DiagnosisandTreatmentofBreastDiseasesCenter,theFirstAffiliatedHospital,SchoolofMedicine,ZhejiangUniversity,Hangzhou310003,China

ZhouLin,Email：linzhou19@163.com

Cytomegalovirus belonged to herpes virus group, which could be carried by health people. The patients with transplantation often suffered from the deficiency of innate and adaptive immune. Therefore, cytomegalovirus relative diseases were extremely common after transplantation, especially in (D+R-/D-R+) group. The clinical outcomes fluctuated between mild asymptomatic infection and multiple organ dysfunction syndromes. The benefit of prophylactic anti-virus drugs should be measured before transplantation for their own limitations (adverse side effects and financial burdens).In the past 10 years, many single nucleotide polymorphisms in human genes had been analyzed to explore their relationships with cytomegalovirus infection, reactivation and tissue relative diseases, but the results were not consistent. Our study tried to illustrate and classify those associations by genes and transplantations. It would help to understand the progress of current researches and show the potential direction in the future.

Gene polymorphisms; Cytomegalovirus; Transplantation

10.3877/cma.j.issn.1674-3903.2016.01.009

310003 杭州，浙江大学医学院附属第一医院器官移植重点实验室1,乳腺疾病诊治中心2

周琳, Email: linzhou19@163.com

2016-01-16)