魏巴金 周琳

·綜述·

人類基因多態(tài)性與移植后巨細胞病毒感染相關性研究進展

魏巴金1, 2周琳1

CMV是一種皰疹DNA病毒，一般正常人群可以攜帶，但不引起臨床癥狀。移植后合并CMV感染在供者CMV陽性而受者CMV陰性(D+/R-)時發(fā)生率較高，輕者可能引起輕微無癥狀感染，重者可能引起嚴重器官功能衰竭甚至死亡。常見的預防措施因為藥物不良反應和經濟問題而無法全面應用。在過去的10年里，有很多探討人類基因多態(tài)性和移植后CMV感染、再燃和相關組織疾病等之間關系的研究，但結果并不一致。本文系統地闡述了目前人類基因多態(tài)性與移植后CMV感染的相關性研究，并根據移植類型(包括肝移植、腎移植、心肺移植、造血干細胞移植和實體器官移植)，有助于掌握目前的研究進展，為未來研究方向提供一定的參考。

基因多態(tài)性； 巨細胞病毒； 移植

移植術后出于保護移植物的需要，往往需要人為降低受者本身的免疫系統功能應答，增加了許多病毒、細菌、真菌等感染的風險。CMV是一種皰疹DNA病毒，一般正常人群可以攜帶，但不引起臨床癥狀。移植術后CMV感染在供者CMV陽性而受者陰性(D+/R-)時發(fā)生率較高，輕者可能引起輕微無癥狀感染，重者可能引起嚴重器官功能衰竭甚至死亡[1-2]。目前，CMV感染及其發(fā)病機制尚不明確，常見的預防措施有移植術前預防性使用藥物，但這不僅加重了患者負擔，而且存在白細胞、血小板減少和發(fā)熱等不良反應[1, 3]。

人類基因多態(tài)性是進化的動力，但也為疾病的治療帶來了一定困難。目前研究表明，人類基因多態(tài)性對移植受者術后CMV易感性、CMV感染臨床表現的多樣性以及對藥物治療的反應上都起著重要作用；人類基因多態(tài)性與移植術后CMV感染的相關性研究對認識該疾病的發(fā)病機制、預測轉歸等方面有重要作用。如何精準地使用抗病毒藥物，實現個體化治療，已成為移植領域的一大研究熱點。

1 肝移植

2007年，Kijpittayarit等[4]首先報道，與不具有Toll樣受體2(toll-like receptor 2，TLR2)位點rs5743708基因多態(tài)性的肝移植受者相比，具有該位點基因多態(tài)性的純合子和雜合子具有更高的CMV DNA復制量，且單因素分析指出其是CMV病的危險因素；但在多因素分析中，通過對年齡、急性排斥反應、感染狀態(tài)等因子校正后，二者相關性存在不確定性。2012年，另一項涉及737例肝移植受者的研究卻指出，TLR2(位點rs5743708)純合子基因型的受者術后組織侵襲性CMV病的發(fā)生率升高[5]。無論供者或受者術前是否存在CMV感染，供者甘露糖結合凝集素(mannose-binding lectin，MBL)和膠原凝集素2基因多態(tài)性可以獨立預測CMV感染，特別是在供者CMV陰性而受者陽性(D-/R+)情況下預測作用更佳，結合供、受者基因型不一致狀態(tài)可以增加預測能力[6]。在活體肝移植中，細胞色素P450 3A5(cytochrome P450 3A5，CYP3A5)表達型肝移植受者發(fā)生CMV和細菌感染的可能性和ImmuKnow檢測免疫細胞功能的結果明顯高于非表達型[7]。IL28B(位點rs12979860)基因多態(tài)性被證實不僅對急性排斥反應有影響，而且與CMV的再燃也有相關性[8]。

2 腎移植

法國一項研究指出，如果將具有TLR4位點rs4986790和rs4986791任何變異型的腎移植受者定義為變異型攜帶者，與野生型攜帶受者相比，CMV感染可能會有較高，但結果差異不具有統計學意義[9]。白介素家族成員基因多態(tài)性與CMV感染的關聯也有較多相關研究。供者IL10位點rs1800896 AA基因型可以降低受者術后CMV感染率并延遲感染發(fā)生時間，受者該基因型基因多態(tài)性則與是否感染CMV沒有關系[10]。法國Hoffmann等[11]另一項研究發(fā)現，經過多因素分析，具有IL12位點rs3212227等位基因C可以增加CMV感染，這種相關性在移植前CMV陽性且未接受預防性治療的受者中更加明顯。在接下來的實驗中，雖然未能驗證IL12位點rs3212227基因多態(tài)性和腎移植術后急性排斥反應、慢性移植物失功和移植物生存有關，卻再次發(fā)現具有位點rs3212227等位基因C受者發(fā)生CMV感染的風險增加[12]。進一步研究PD-1基因多態(tài)性與CMV感染的關系，Hoffmann等[13]還發(fā)現該基因位點rs11568821等位基因A與IL12基因3-UTR區(qū)域的基因多態(tài)性相比，具有更好的預測CMV感染的能力。具有IL28B位點rs12979860等位基因T的腎移植受者CMV感染風險降低34%，在術前不采取預防措施的亞組分析中，TLR9位點rs5743836 TT基因型同樣被發(fā)現對CMV感染具有保護作用，而樹突狀細胞特異性細胞黏附分子-3結合非整合素因子(dendritic cell specific intercellular-adhesionmolecule-3 grabbing non-integrin，DC-SIGN)位點rs735240GG基因型卻被視為危險因素[14]。有關細胞因子IFN-γ(位點rs2430561)單因素分析表明，相對于TT基因型，AA基因型攜帶者CMV感染風險增加約3.4倍；多因素分析指出：D+/R-、位點rs2430561的基因多態(tài)性、急性排斥反應和使用抗胸腺細胞球蛋白誘導可以作為CMV感染的高危因素[15]。兩項針對不同地區(qū)人群開展的研究同時指出，在中國西北部和印度腎移植受者中，HLA-G啟動子一段14 bp的缺失會同時影響CMV感染和急性排斥反應的發(fā)生情況[16-17]。一項關于腎移植術后早期3個月受者CMV感染的研究指出，維生素D受體位點FokIff基因型攜帶者CMV病的發(fā)生率會升高[18]。相比無癥狀CMV感染患者，細胞毒性T淋巴細胞相關抗原4(cytotoxic T lymphocyte antigen-4，CTLA4)(位點rs231775和rs3087243)GG基因型在有癥狀的CMV感染患者中頻率較高，它的存在可以使CMV感染出現癥狀的風險增加約2.5倍[19]。

3 心肺移植

IFN-γ位點rs2430561 TT基因型的肺移植受者不僅IFN-γ分泌增加，而且和CMV病發(fā)展相關，特別是在CMV陽性受者中更加明顯，同時也降低了血CMV載量的峰值[20]。奧地利一項關于肺移植的研究中，研究人員發(fā)現人CMV特異性免疫球蛋白表達和移植后巨細胞病毒復制密切相關，并且通過測定44位患者的免疫球蛋白重鏈γ1的基因多態(tài)性，認為其影響人CMV特異性免疫球蛋白表達[21]。Gourley等[22]在心臟移植研究中發(fā)現，TNF-α、TNF-β、IL-6、IL-10、IFN-γ的基因多態(tài)性和CMV感染無相關性。

4 造血干細胞移植

德國一項針對43例造血干細胞移植受者的研究中，趨化因子受體5(chemokine receptor 5，CCR5)和IL10的基因多態(tài)性被認為和CMV病病情發(fā)展有關，而單核細胞趨化蛋白-1(monocyte chemotactic protein 1，MCP-1)則和CMV的再燃有關[23]。Corrales等[24]對102例西班牙造血干細胞移植受者的研究發(fā)現，雖然受者和供者CCR5(位點rs1800023)、MCP-1(位點rs13900)、IL-10(位點rs1878672)及TLR9(位點rs352140)基因多態(tài)性和CMV的活動性無明顯聯系，但是供者CCR5位點rs1800023 AA基因型攜帶者CMV血癥和血漿中CMV DNA峰值持續(xù)時間較長。DC-SIGN基因啟動子區(qū)域的(位點rs735240和rs2287886)基因多態(tài)性可以影響DC-SIGN基因的表達，從而影響樹突狀細胞對CMV的免疫作用，和CMV再燃、CMV病密切相關[25]。和肺移植、腎移植一樣，行造血干細胞移植后IFN-γ的基因多態(tài)性和CMV病再發(fā)、高病毒載量有關，而CMV拷貝數高往往伴隨宿主急性移植物排斥反應，并且預后較差[26]。供者CTLA4(位點rs3087243)的AA基因型更易在異基因造血干細胞移植的早期出現CMV感染以及反復發(fā)作，并且和預后呈現一定的相關性[27]。造血干細胞移植并出現過移植物排斥反應的受者，其共刺激分子中的CLTA4(位點rs4553808)和CD28(位點rs3116496)基因多態(tài)性與活動性CMV感染相關[28]。雖然造血干細胞移植受者和供者IL28B(位點rs8099917)基因多態(tài)性和活動性CMV感染無明顯關聯，但供者TT基因型會有較短的血CMV DNA持續(xù)時間[29]。在接受異基因造血干細胞移植的兒童白血病患者中擁有核轉錄因子FOXP3位點rs3761548的等位基因CC攜帶者CMV感染發(fā)生率較高，同時肝靜脈閉塞性疾病風險也會提高，并且生存時間較短[30]。

5 實體器官移植

在檢測MBL的3個功能基因多態(tài)性位點后，發(fā)現其單倍型全部為純合子狀態(tài)，和侵襲性CMV病密切相關，相比非純合子受者，發(fā)生該疾病的風險提高了約6倍[31]。D+/R-實體器官移植受者IL28B位點rs8099917 TT基因型攜帶者會有較高的CMV DNA復制量，并且體外實驗證明，該位點在CMV的刺激下會影響IL28B的表達[32]。IL28B基因可以編碼IFN，IFN基因位點rs368234815多態(tài)性包括基因型TT/TT、基因型-G/-G及二者的雜合子，基因型-G/-G攜帶者CMV DNA復制量更高，在供者CMV陽性的受者中尤為明顯[33]。MCP-2分泌和器官移植后CMV感染密切相關，且停止預防性用藥后，在MCP-2啟動子區(qū)域位點rs3138035 TT基因型的D+/R-受者群體中會出現CMV復制[34]。

6 總 結

目前有關人類基因多態(tài)性和移植后CMV感染的相關研究主要集中在細胞因子(如IL和IFN家族等)，樣本量相對較少，取得的結果存在一定的局限性，尚不能大規(guī)模應用于臨床。特別是存在相同基因位點在不同的移植研究中出現不同結果，可能是由各種族和疾病評判標準的差異引起，需要進一步的薈萃分析等手段來增加證據的信度。此外，基因多態(tài)性檢測費用雖然較以前有大幅度的下降，但廣泛應用于臨床尚有一定的距離?？梢灶A見基因多態(tài)性會在臨床個體化治療應用中發(fā)揮重要作用。隨著中國人體器官分配與共享系統等相關協作登記制度的完善，開展大規(guī)模人群研究的障礙逐步減少，基因多態(tài)性的檢測技術也日新月異，未來多中心、大樣本試驗將會陸續(xù)開展。

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(本文編輯：徐小明)

魏巴金, 周琳. 人類基因多態(tài)性與移植后巨細胞病毒感染相關性研究進展[J/CD]. 中華移植雜志: 電子版, 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，浙江大學醫(yī)學院附屬第一醫(yī)院器官移植重點實驗室1,乳腺疾病診治中心2

周琳, Email: linzhou19@163.com

2016-01-16)