蘇佳,趙煒,劉丹,王嘉,白洪旭,吳華偉,薛青紅,陳曉春
外源性馬立克氏病病毒熒光定量PCR檢測(cè)方法的建立
蘇佳,趙煒,劉丹,王嘉,白洪旭,吳華偉,薛青紅,陳曉春
中國獸醫(yī)藥品監(jiān)察所,北京 100081
【目的】為解決現(xiàn)有獸用生物制品外源性馬立克氏病病毒(Marek’s disease virus, MDV)檢驗(yàn)方法靈敏度低、檢測(cè)時(shí)間長(zhǎng)、鑒別性不強(qiáng)的問題,研究分別建立MDV血清1型(MDV serotype 1,MDV 1)和MDV血清3型(MDV serotype 3,MDV 3)毒株的實(shí)時(shí)熒光定量PCR檢測(cè)方法,用于禽用生物制品純凈性控制?!痉椒ā繌腘CBI下載MDV 1、MDV血清2型(MDV serotype 1,MDV 2)和MDV 3各毒株序列,進(jìn)行核苷酸和氨基酸序列比對(duì)分析;分別針對(duì)MDV 1 CVI988毒株、MDV 3 FC126毒株的設(shè)計(jì)特異性引物和相應(yīng)的Taqman探針,建立實(shí)時(shí)熒光定量PCR檢測(cè)方法;分別構(gòu)建相應(yīng)的重組質(zhì)粒作為陽性標(biāo)準(zhǔn)品,建立標(biāo)準(zhǔn)曲線,并評(píng)價(jià)所建立方法基因拷貝數(shù)檢測(cè)的靈敏度;分別對(duì)其他禽用病毒類生物制品、毒種、MDV 2 SB-1毒株的全長(zhǎng)質(zhì)粒及生產(chǎn)原材料(SPF雞胚尿囊液、胚體、尿囊膜、雞胚成纖維細(xì)胞)進(jìn)行檢測(cè),評(píng)價(jià)檢測(cè)方法的特異性;分別對(duì)600、60、6、0.6、0.06、0.006、0.0006 PFU的CVI988毒株和FC126毒株進(jìn)行檢測(cè),評(píng)價(jià)所建立方法檢測(cè)活病毒粒子的靈敏度;分別以不同稀釋度的陽性標(biāo)準(zhǔn)品質(zhì)粒為模板,進(jìn)行3次重復(fù)性檢測(cè),計(jì)算變異系數(shù),分析所建立檢測(cè)方法的可重復(fù)性?!窘Y(jié)果】MDV在同一血清型內(nèi)核苷酸和推導(dǎo)的氨基酸同源性達(dá)99.99%,具有很高的保守性,在不同血清型間核苷酸同源性只有約75%,推導(dǎo)的氨基酸同源性只有約85%;分別建立了MDV 1和MDV 3兩種實(shí)時(shí)熒光定量PCR檢測(cè)方法;MDV 1檢測(cè)方法標(biāo)準(zhǔn)曲線的擴(kuò)增效率E=98.8%,相關(guān)系數(shù)2=0.992,標(biāo)準(zhǔn)曲線方程=-3.351+38.828(=Ct,=lg(拷貝數(shù))),MDV 3檢測(cè)方法標(biāo)準(zhǔn)曲線的擴(kuò)增效率E=95.0%,相關(guān)系數(shù)2=0.998,標(biāo)準(zhǔn)曲線方程=-3.447+36.496(=Ct,=lg(拷貝數(shù)));所建立的兩種檢測(cè)方法特異性好,MDV 1或MDV 3毒株擴(kuò)增曲線良好,其他禽用病毒類生物制品、毒種、MDV 2 SB-1毒株的全長(zhǎng)質(zhì)粒及生產(chǎn)原材料未出現(xiàn)特異性擴(kuò)增曲線;靈敏度高,MDV 1基因拷貝數(shù)檢出限度為32.8拷貝/μL,至少可檢出0.006 PFU的CVI988毒株,MDV 3基因拷貝數(shù)檢出限度為10 拷貝/μL,至少可檢出0.006 PFU的FC126毒株;重復(fù)性好,MDV 1檢測(cè)方法重復(fù)性試驗(yàn)的變異系數(shù)小于1%,MDV 3檢測(cè)方法重復(fù)性試驗(yàn)的變異系數(shù)小于1.5%?!窘Y(jié)論】所建立的實(shí)時(shí)熒光定量PCR檢測(cè)方法可分別用于禽用生物制品中外源性MDV1、MDV3毒株的檢測(cè)。
馬立克氏病病毒;實(shí)時(shí)熒光定量PCR;外源病毒;檢測(cè)
【研究意義】生物制品生產(chǎn)過程中涉及的動(dòng)物源性原輔材料,如生產(chǎn)用動(dòng)物、細(xì)胞、培養(yǎng)基、血清、胰酶等,都容易引入外源微生物,特別是病毒[1-2],而外源病毒的污染,不僅給生物制品生產(chǎn)企業(yè)帶來重大經(jīng)濟(jì)損失,還會(huì)影響疫苗免疫效力,甚至引發(fā)新的疫情,給下游生物制品使用企業(yè)造成滅頂之災(zāi)[3-4]。實(shí)時(shí)熒光定量PCR是近年來發(fā)展起來的新型PCR技術(shù),不僅可以定性分析,還可以對(duì)檢測(cè)樣品進(jìn)行定量分析,具有靈敏度高、特異性強(qiáng)、檢測(cè)迅速、重復(fù)性好等優(yōu)點(diǎn),已廣泛應(yīng)用于多種病原的檢測(cè)[5-8]。建立MDV實(shí)時(shí)熒光定量PCR檢測(cè)方法,進(jìn)而用于禽源生物制品外源性MDV的檢測(cè),對(duì)于禽源生物制品質(zhì)量控制、MDV實(shí)驗(yàn)室分子生物學(xué)診斷等將有重要的實(shí)際臨床價(jià)值。【前人研究進(jìn)展】馬立克氏病是雞的一種常見的惡性淋巴細(xì)胞增生性疾病[9-10],該病的病原MDV屬于α皰疹病毒亞類的屬,根據(jù)病毒的血清學(xué)反應(yīng),分為MDV 1、MDV 2和MDV 3合計(jì)3個(gè)血清型(https://talk.ictvonline.org/ taxonomy/),其中MDV 1是指具有不同致病性的野毒株,MDV 2為從健康雞只分離得到的非致病毒株,MDV 3則是從健康火雞分離得到的非致病毒株,又稱為火雞皰疹病毒[11-13]?,F(xiàn)有外源性MDV檢驗(yàn)方法主要是通過雞胚法觀察尿囊膜病變、細(xì)胞法檢查細(xì)胞病變、雞檢查法通過瓊脂擴(kuò)散試驗(yàn)測(cè)定抗體[14]。但隨著獸用生物制品品種的不斷增加和生物技術(shù)的不斷進(jìn)步,現(xiàn)有的外源性MDV檢驗(yàn)國家標(biāo)準(zhǔn)已不能完全滿足檢驗(yàn)、檢測(cè)的需求。主要表現(xiàn)在兩個(gè)方面:一是方法靈敏度問題,如雞檢查法中MDV采用瓊脂擴(kuò)散試驗(yàn)進(jìn)行抗體檢測(cè),靈敏度低、穩(wěn)定性差、檢測(cè)時(shí)間長(zhǎng)、不同來源檢測(cè)抗原反應(yīng)性差異較大;二是方法的鑒別性不強(qiáng),如不同血清型MDV相互污染時(shí),無法進(jìn)行外源性MDV的鑒別。分子生物學(xué)相關(guān)檢測(cè)技術(shù)已廣泛應(yīng)用于多種病原的檢測(cè),歐洲藥典已將PCR方法描述為參考技術(shù),并對(duì)待檢材料類型、檢測(cè)過程及結(jié)果判定做了詳細(xì)的質(zhì)量要求,只要符合相關(guān)質(zhì)量要求,便可使用PCR作為替代檢測(cè)方法[15-17]。而在國際貿(mào)易指定試驗(yàn)中,PCR方法也已經(jīng)廣泛使用,如世界動(dòng)物衛(wèi)生組織已將檢測(cè)藍(lán)舌病病毒、非洲豬瘟病毒、牛傳染性鼻氣管炎病毒等病毒的PCR方法列為國際貿(mào)易指定試驗(yàn)方法[18]。此外,國家市場(chǎng)監(jiān)督管理總局、國家標(biāo)準(zhǔn)化管理委員會(huì)最新發(fā)布的中華人民共和國國家標(biāo)準(zhǔn),將普通PCR方法、實(shí)時(shí)熒光定量PCR方法及熒光RAA方法等分子生物學(xué)檢測(cè)技術(shù)納入非洲豬瘟診斷技術(shù)[19]。【本研究切入點(diǎn)】目前禽用生物制品中,外源性MDV檢測(cè)國家標(biāo)準(zhǔn)中并無分子生物學(xué)相關(guān)的檢測(cè)技術(shù)。MDV編碼的蛋白與、和分別編碼的VP23、preVP22a和VP19c蛋白是病毒核衣殼的重要組成成分[20],不同血清型內(nèi)MDV毒株的在核苷酸和氨基酸序列上具有很高的保守性[21]?!緮M解決的關(guān)鍵問題】以MDV的基因?yàn)榘袠?biāo)設(shè)計(jì)特異的引物和相應(yīng)的探針,建立快速、靈敏、特異的MDV 1、MDV 3毒株實(shí)時(shí)熒光定量PCR檢測(cè)方法,用于禽用生物制品外源性MDV污染的純凈性控制、MDV的快速診斷和定量檢測(cè)。
本研究于2020年2月至2022年6月在中國獸醫(yī)藥品監(jiān)察所完成。
1.1.1 病毒 試驗(yàn)所涉及的禽用病毒類生物制品及毒種的來源見表1。
1.1.2 質(zhì)粒 由于無MDV 2毒株,因此根據(jù)MDV 2 SB-1毒株全基因(序列號(hào):HQ840738.1)合成其,連接至pMV載體,構(gòu)建pMV-SB-1(UL19)質(zhì)粒,作為特異性研究材料。
1.1.3 實(shí)驗(yàn)動(dòng)物 8日齡SPF雞胚,購自北京勃林格殷格翰維通生物技術(shù)有限公司。
1.1.4 主要試劑與儀器 病毒基因組DNA/RNA提取試劑盒(DP 315)購自天根生化科技有限公司,TaqMan? Fast Advanced Master Mix(4444557)購自美國ABI公司,E.Z.N.A膠回收試劑盒(D 2500)購自O(shè)MEGA公司,質(zhì)粒中量提取PureYield TM Plasmid Midipre System試劑盒(A 2492)購自Promega公司,2×TransStart? GoldPfu PCR SuperMix(AS 401)、2×EasyTaq? PCR SuperMix (+dye )(AS 111)、pEASY- Blunt Cloning Kit(CB 101)、Trans1-T1 Phage Resistant Chemically Competent Cell(CD 501)購自北京全式金生物技術(shù)有限公司,CFX 96型熒光定量PCR儀購自美國BIO-RAD公司,NANORDROP LITE超微量核酸蛋白檢測(cè)儀購自美國Thermo公司。
1.2.1 不同血清型MDV序列比對(duì)分析及引物設(shè)計(jì) 下載GenBank上公布的MDV各血清型毒株序列,經(jīng)核苷酸和氨基酸序列比對(duì)分析,針對(duì)MDV 1和MDV 3分別設(shè)計(jì)特異性引物及探針(表2)。引物和探針由北京六合華大基因科技有限公司合成。
表2 引物和探針
1.2.2 標(biāo)準(zhǔn)品質(zhì)粒的制備 取病毒液200 μL,使用病毒基因組DNA/RNA提取試劑盒提取病毒核酸,進(jìn)行PCR擴(kuò)增,50 μL反應(yīng)體系:上、下游引物(10 μmol·L-1)各1 μL,2×TransStart? GoldPfu PCR SuperMix 25 μL,模板3 μL,ddH2O 20 μL。PCR反應(yīng)條件:94 ℃預(yù)變性5 min;94 ℃變性20 s,60 ℃退火20 s,72 ℃延伸20 s,35個(gè)循環(huán);72 ℃終末延伸10 min。PCR產(chǎn)物經(jīng)瓊脂糖凝膠電泳鑒定,切膠純化、回收目的DNA片段,將目的片段連接至pEASY-Blunt載體,轉(zhuǎn)化Trans1-T1感受態(tài)細(xì)胞,通過菌液PCR鑒定獲得陽性單菌落,提取質(zhì)粒經(jīng)測(cè)序驗(yàn)證正確后用作陽性標(biāo)準(zhǔn)品質(zhì)粒。
1.2.3 實(shí)時(shí)熒光定量PCR方法的建立
①實(shí)時(shí)熒光定量PCR反應(yīng)體系與反應(yīng)條件的優(yōu)化 參考TaqMan? Fast Advanced Master Mix推薦的反應(yīng)體系和反應(yīng)條件,將探針和引物分別稀釋至終濃度為10 μmol·L-1,取0.2 μL以及0.4 μL的探針和0.2 μL、0.4 μL以及0.6 μL的引物棋盤式組合,進(jìn)行實(shí)時(shí)熒光定量PCR試驗(yàn),篩選出最優(yōu)的探針濃度以及引物濃度;分別以55 ℃、60 ℃作為退火溫度,進(jìn)行實(shí)時(shí)熒光定量PCR試驗(yàn),確定反應(yīng)最優(yōu)退火溫度。
②標(biāo)準(zhǔn)曲線的建立及靈敏度測(cè)定 使用超微量核酸蛋白檢測(cè)儀測(cè)定標(biāo)準(zhǔn)品質(zhì)粒濃度,根據(jù)公式N=(質(zhì)粒濃度(ng·μL-1)×10-9×6.02×1023)/(重組質(zhì)粒堿基數(shù)×660)計(jì)算重組質(zhì)??截悢?shù),其中MDV 1重組質(zhì)??截悢?shù)為3.28×108拷貝/μL,MDV 3重組質(zhì)??截悢?shù)為1×108拷貝/μL。分別將重組質(zhì)粒10倍系列稀釋后作為標(biāo)準(zhǔn)陽性模板,以優(yōu)化的反應(yīng)條件進(jìn)行實(shí)時(shí)熒光定量PCR檢測(cè),確定其檢測(cè)基因拷貝數(shù)的靈敏度,繪制標(biāo)準(zhǔn)曲線,并得出反應(yīng)的擴(kuò)增效率和曲線的相關(guān)性系數(shù)。
此外,分別取600、60、6、0.6、0.06、0.006、0.0006 PFU的MDV 1 CVI988病毒液和MDV 3 FC126病毒液,提取病毒基因組作為模板,用建立的相應(yīng)實(shí)時(shí)熒光定量PCR檢測(cè)方法進(jìn)行檢測(cè),確定所建立方法檢測(cè)活病毒粒子的靈敏度。
③特異性試驗(yàn) 對(duì)特異性研究樣品,包括其他禽用病毒類生物制品、毒種(表1)、質(zhì)粒pMV-SB-1 (UL19)及生產(chǎn)原材料(SPF雞胚尿囊液、胚體、尿囊膜、雞胚成纖維細(xì)胞)分別進(jìn)行處理,方法如下:尿囊液、細(xì)胞、胚體、尿囊膜生產(chǎn)毒:用一定體積的生理鹽水將樣品溶解至100羽份/200 μL,12 000 r/min 4 ℃離心10 min,取上清;SPF雞胚尿囊液:12 000 r/min 4 ℃離心10 min,取上清;雞胚成纖維細(xì)胞(按照現(xiàn)行《中國獸藥典》附錄進(jìn)行制備):取生長(zhǎng)7d以上、面積75 cm2以上的雞胚成纖維細(xì)胞,反復(fù)凍融3次后,12 000 r/min 4 ℃離心10 min,取上清;SPF雞胚胚體、尿囊膜:剪取一定體積SPF雞胚胚體或尿囊膜,加入5倍體積的生理鹽水,在生物安全柜中研磨,將獲得的勻漿反復(fù)凍融3次后,12 000 r/min 4 ℃離心10 min,取上清;取上述各樣品200 μL,使用病毒基因組DNA/RNA提取試劑盒提取病毒基因組,質(zhì)粒pMV-SB-1 (UL19)直接作為反應(yīng)模板,同時(shí)用雙蒸水作為陰性對(duì)照,采用所建立的實(shí)時(shí)熒光定量PCR方法進(jìn)行檢測(cè)。
④重復(fù)性試驗(yàn) 針對(duì)MDV 1以3.28×107—3.28×101拷貝/μL 10倍系列稀釋的標(biāo)準(zhǔn)品質(zhì)粒為模板,針對(duì)MDV 3以1×107—1×101拷貝/μL 10倍系列稀釋的標(biāo)準(zhǔn)品質(zhì)粒為模板,每個(gè)濃度的樣品做3次重復(fù)性檢測(cè),計(jì)算變異系數(shù),分析所建立的實(shí)時(shí)熒光定量PCR檢測(cè)方法的可重復(fù)性。
對(duì)不同血清型MDV的核苷酸和氨基酸序列進(jìn)行MegAlign比對(duì)分析(表1),結(jié)果可見,MDV在同一血清型內(nèi)核苷酸和推導(dǎo)的氨基酸同源性達(dá)99.99%,具有很高的保守性,在不同血清型間核苷酸同源性只有約70%,推導(dǎo)的氨基酸同源性只有約40%。因此,可以為靶標(biāo),設(shè)計(jì)不同血清型特異性檢測(cè)引物和探針。
A:不同血清型MDV UL19基因核苷酸同源性分析;B:不同血清型MDV UL19基因推導(dǎo)的氨基酸同源性分析
MDV 1及MDV 3實(shí)時(shí)熒光定量PCR方法中,探針(10 μmol·L-1)添加量為0.2 μL、上、下引物(10 μmol·L-1)添加量各為0.4 μL時(shí),特異性擴(kuò)增曲線效果最佳,Ct值也相對(duì)較?。▓D2-A和B紅色擴(kuò)增曲線所示);退火溫度為55 ℃與60 ℃所產(chǎn)生的擴(kuò)增曲線形態(tài)差異較小,退火溫度為60 ℃時(shí)的Ct值略小于退火溫度為55 ℃時(shí)(圖2-C和D紅色擴(kuò)增曲線所示)。綜合考慮Ct值、熒光強(qiáng)度,確定反應(yīng)體系20 μL:TaqMan? Fast Advanced Master Mix(2×)10 μL,上下游引物(10 μmol·L-1)各0.4 μL,探針(10 μmol·L-1)0.2 μL,模板2 μL,ddH2O 7 μL。反應(yīng)條件:50 ℃ UNG酶孵育2 min,95 ℃聚合酶激活20 s;95 ℃變性3 s,60 ℃退火/延伸30 s,40個(gè)循環(huán),收集熒光信號(hào)。
A:MDV 1實(shí)時(shí)熒光定量PCR方法引物和探針濃度優(yōu)化;B:MDV 3實(shí)時(shí)熒光定量PCR方法引物和探針濃度優(yōu)化;C:MDV 1實(shí)時(shí)熒光定量PCR方法退火溫度優(yōu)化;D:MDV 3實(shí)時(shí)熒光定量PCR方法退火溫度優(yōu)化
通過實(shí)時(shí)熒光定量PCR,得到各標(biāo)準(zhǔn)陽性模板的Ct值,以log(拷貝數(shù))為橫坐標(biāo)、Ct值為縱坐標(biāo)繪制標(biāo)準(zhǔn)曲線。MDV 1標(biāo)準(zhǔn)曲線如圖3-A,B所示:擴(kuò)增效率E=98.8%,相關(guān)系數(shù)2=0.992,標(biāo)準(zhǔn)曲線方程=-3.351+38.828(=Ct,=log(拷貝數(shù)));MDV 3標(biāo)準(zhǔn)曲線如圖3-C,D所示:擴(kuò)增效率E=95.0%,2=0.998,標(biāo)準(zhǔn)曲線方程=-3.447+36.496(=Ct,=log(拷貝數(shù)))。
經(jīng)檢測(cè),MDV 1、MDV 3實(shí)時(shí)熒光定量PCR方法基因拷貝數(shù)檢測(cè)靈敏度分別可達(dá)到32.8,10 拷貝/μL(結(jié)果見圖3-A,C),MDV 1、MDV 3實(shí)時(shí)熒光定量PCR方法活病毒粒子檢測(cè)靈敏度均可達(dá)到0.006 PFU(圖4),靈敏度高。
特異性試驗(yàn)結(jié)果顯示,MDV 1實(shí)時(shí)熒光定量PCR對(duì)MDV 1的3個(gè)疫苗株(CVI988株、SC9-1株和814株)及1個(gè)強(qiáng)毒株(Md5株)均可檢測(cè)到特異性擴(kuò)增信號(hào),而對(duì)其他特異性研究樣品(包括禽用疫苗、生產(chǎn)用毒、MDV 3 FC126毒株、MDV 2 pMV-SB-1(UL19)質(zhì)粒、雙蒸水和生產(chǎn)原材料)檢測(cè)結(jié)果為陰性(圖5-A);MDV 3實(shí)時(shí)熒光定量PCR僅可特異性擴(kuò)增出血清3型MDV毒株,而對(duì)包括MDV 1毒株和MDV 2 pMV-SB-1(UL19)質(zhì)粒在內(nèi)的其他特異性研究樣品擴(kuò)增結(jié)果為陰性(圖5-B);說明所建立的MDV 1和MDV 3實(shí)時(shí)熒光定量PCR檢測(cè)方法的特異性好。
A:MDV 1實(shí)時(shí)熒光定量PCR方法基因拷貝數(shù)靈敏度的檢測(cè);B:MDV 1實(shí)時(shí)熒光定量PCR方法標(biāo)準(zhǔn)曲線的建立;C:MDV 3實(shí)時(shí)熒光定量PCR方法基因拷貝數(shù)靈敏度的檢測(cè);D:MDV 3實(shí)時(shí)熒光定量PCR方法標(biāo)準(zhǔn)曲線的建立
A:MDV 1實(shí)時(shí)熒光定量PCR方法的活病毒粒子檢測(cè)靈敏度;B:MDV 3實(shí)時(shí)熒光定量PCR方法的活病毒粒子檢測(cè)靈敏度
取7個(gè)10倍梯度稀釋的標(biāo)準(zhǔn)品質(zhì)粒做3次重復(fù)性檢測(cè),結(jié)果如表3、表4所示,兩種實(shí)時(shí)熒光定量PCR檢測(cè)方法的變異系數(shù)均低于1.5%,表明所建立的實(shí)時(shí)熒光定量PCR檢測(cè)方法有較好的可重復(fù)性。
A:MDV 1實(shí)時(shí)熒光定量PCR方法特異性檢測(cè);B:MDV 3實(shí)時(shí)熒光定量PCR方法特異性檢測(cè)
表3 MDV 1實(shí)時(shí)熒光定量PCR重復(fù)性的檢測(cè)
2009年,Merrimack公司在一次性生物反應(yīng)器進(jìn)行CHO細(xì)胞培養(yǎng)時(shí),通過PCR方法檢測(cè)到鼠細(xì)小病毒污染,從原輔料、工廠環(huán)境、生產(chǎn)人員及生產(chǎn)工藝等方面進(jìn)行快速調(diào)查,最終鎖定在培養(yǎng)基或添加物上,但是通過PCR方法,仍未得到確認(rèn),該公司委托第三方,通過實(shí)時(shí)熒光定量PCR方法,最后確定培養(yǎng)基添加物為罪魁禍?zhǔn)譡22]。LI等[23]建立了液滴數(shù)字PCR檢測(cè)技術(shù),用于減毒活疫苗中雞傳染性貧血病毒污染的檢測(cè)。MOTITSCHKE等[24]將PCR檢測(cè)新城疫病毒、禽呼腸孤病毒、禽流感病毒和禽傳染性支氣管炎病毒的靈敏度與歐洲藥典中相應(yīng)血清學(xué)的靈敏度進(jìn)行了比較,發(fā)現(xiàn)PCR檢測(cè)技術(shù)完全可以替代血清學(xué)技術(shù)。實(shí)時(shí)熒光定量PCR相比普通PCR具有更高的靈敏度,如果實(shí)時(shí)熒光定量PCR檢測(cè)陽性,在不確定是否為假陽性的情況下,可對(duì)該樣品進(jìn)行基因測(cè)序[25],同時(shí)可將該樣品在敏感細(xì)胞系或動(dòng)物上繼代后再進(jìn)行檢測(cè),避免誤判。
表4 MDV 3實(shí)時(shí)熒光定量PCR重復(fù)性的檢測(cè)
目前2020年版《中華人民共和國獸藥典》(三部)外源病毒檢測(cè)法中針對(duì)禽源制品及其細(xì)胞中外源性MDV病毒的檢驗(yàn),主要是通過雞胚法觀察尿囊膜病變、細(xì)胞法檢查細(xì)胞病變、雞檢查法測(cè)定MDV特異性抗體[14]。雞胚檢查法是將樣品接種9—11日齡雞胚,連續(xù)7日觀察是否出現(xiàn)尿囊膜病變,細(xì)胞法是將樣品接種制備的SPF雞胚成纖維細(xì)胞,培養(yǎng)5—7日觀察是否出現(xiàn)細(xì)胞病變,兩種方法均無法進(jìn)行鑒別檢驗(yàn),且細(xì)胞法試驗(yàn)過程中所使用的原材料(如雞胚、胎牛血清、胰酶等)都可能引入外源病毒[26],可采用更靈敏的分子生物學(xué)方法來排除試驗(yàn)過程中引入的外源病毒,以保證試驗(yàn)結(jié)果的準(zhǔn)確性。雞檢查法是將樣品接種SPF雞,21日后進(jìn)行第二次接種,第一次接種后42日采血通過瓊脂擴(kuò)散試驗(yàn)測(cè)定MDV特異性抗體,靈敏度低、穩(wěn)定性差、檢測(cè)時(shí)間長(zhǎng)、不同來源檢測(cè)抗原反應(yīng)性差異較大,且無法進(jìn)行不同血清型MDV的鑒別,而分子生物學(xué)技術(shù)的引入可高效解決上述問題。因此,本研究擬通過建立快速(3 h可完成核酸提取及檢測(cè))、靈敏、特異的MDV實(shí)時(shí)熒光定量PCR檢測(cè)方法解決上述問題。
靶基因選擇上,為MDV 1毒株特有的致瘤基因,大量學(xué)者建立了以為靶標(biāo)的普通PCR[27-29]及熒光定量PCR[30-34]鑒別檢測(cè)方法,特異性良好,靈敏度各異,但是,隨著MDV的變異與演化,缺失毒株層出不窮,國內(nèi)[35]及國外(包括伊拉克[36]、意大利[37]、日本[38-39]、沙特阿拉伯[40]和印度[41]等)都有相關(guān)報(bào)道;GIMENO等[42]與BAIGENT等[43]針對(duì)MDV 1建立了可有效區(qū)分CVI988疫苗株與其他致瘤性MDV 1毒株的實(shí)時(shí)熒光定量PCR方法,特異性較好;CORTES等[44]以MDV 1 Md5株糖蛋白為靶標(biāo)建立了可檢測(cè)家禽血液和羽毛囊樣本中MDV 1含量的實(shí)時(shí)熒光定量PCR方法,但未在其他多種MDV 1毒株上進(jìn)行驗(yàn)證。為建立可涵蓋所有MDV 1毒株的檢測(cè)方法,本研究選擇編碼MDV核衣殼蛋白的為靶基因(目前無缺失毒株的相關(guān)報(bào)道)建立MDV 1實(shí)時(shí)熒光定量PCR檢測(cè)方法,經(jīng)驗(yàn)證該方法可有效用于缺失毒SC9-1株及其他血清1型毒株的檢測(cè),為禽用生物制品外源性血清1型MDV污染純凈性控制提供了技術(shù)支持。血清3型毒株方面,ISLAM等[45]以為靶標(biāo)建立了檢出限度為75拷貝的實(shí)時(shí)熒光定量PCR方法,李冬冬[46]以為靶標(biāo)建立的重組火雞皰疹病毒rHVT-VP2 實(shí)時(shí)熒光定量PCR檢測(cè)方法的靈敏度為540拷貝/μL,我們以為靶基因建立的MDV 3 qPCR檢測(cè)方法檢出限度達(dá)10拷貝/μL,可見,針對(duì)不同基因建立的實(shí)時(shí)熒光定量PCR檢測(cè)方法其靈敏度存在差異。
目前我國MDV疫苗主要是MDV 1 CVI988株、814株和MDV 3 FC126株,考慮到MDV 2為從健康雞只分離得到的非致病毒株,因此本研究針對(duì)MDV 1及MDV 3分別建立了鑒別檢測(cè)實(shí)時(shí)熒光定量PCR方法,以期用于外源性MDV的檢測(cè)。
本研究所建立MDV 1、MDV 3實(shí)時(shí)熒光定量PCR檢測(cè)方法特異性好,靈敏度高,重復(fù)性好,可作為現(xiàn)有外源性MDV檢測(cè)方法的有效補(bǔ)充,用于禽用生物制品純凈性控制。
[1] 范學(xué)政, 李翠, 寧宜寶, 曲鴻飛. 病毒類疫苗中外源病毒污染、檢測(cè)方法與控制措施. 中國獸藥雜志, 2014, 48(11): 57-61.
FAN X Z, LI C, NING Y B, QU H F. Contamination of extraneous virus in viral vaccine and detection methods, purification control strategies. Chinese Journal of Veterinary Drug, 2014, 48(11): 57-61. (in Chinese)
[2] PASTORET P P. Human and animal vaccine contaminations. Biologicals, 2010, 38(3): 332-334.
[3] SU Q, LIU X F, LI Y, MENG F F, CUI Z Z, CHANG S, ZHAO P. The intracorporal interaction of fowl adenovirus type 4 and LaSota strain significantly aggravates the pathogenicity of one another after using contaminated Newcastle disease virus-attenuated vaccine. Poultry Science, 2019, 98(2): 613-620.
[4] SU Q, MENG F, LI Y, ZHANG Y, ZHANG Z, CUI Z, CHANG S, ZHAO P. Chicken infectious anemia virus helps fowl adenovirus break the protection of maternal antibody and cause inclusion body hepatitis-hydropericardium syndrome in layers after using co-contaminated Newcastle disease virus-attenuated vaccine. Poultry Science, 2019, 98(2): 621-628.
[5] 張帆帆, 宋德平, 周信榮, 黃冬艷, 李安琪, 彭棋, 陳燕君, 吳瓊, 何后軍, 唐玉新. 新現(xiàn)豬Delta冠狀病毒RT-PCR檢測(cè)方法的建立及其應(yīng)用. 中國農(nóng)業(yè)科學(xué), 2016, 49(7): 1408-1416.doi: 10.3864/j. issn.0578-1752.2016.07.016.
ZHANG F F, SONG D P, ZHOU X R, HUANG D Y, LI A Q, PENG Q, CHEN Y J, WU Q, HE H J, TANG Y X. Establishment and application of a RT-PCR assay for detection of newly emerged. Scientia Agricultura Sinica, 2016, 49(7): 1408-1416. doi: 10.3864/j.issn.0578-1752.2016.07.016.(in Chinese)
[6] 王濤, 韓玉, 潘力, 王冰, 孫茂文, 王翌, 羅玉子, 仇華吉, 孫元. 針對(duì)非洲豬瘟病毒MGF360-13L基因的TaqMan熒光定量PCR的建立. 中國農(nóng)業(yè)科學(xué), 2021, 54(5): 1073-1080.doi: 10.3864/j.issn. 0578-1752.2021.05.018.
WANG T, HAN Y, PAN L, WANG B, SUN M W, WANG Y, LUO Y Z, QIU H J, SUN Y. Development of a TaqMan real-time PCR targeting the MGF360-13L gene of African swine fever virus. Scientia Agricultura Sinica, 2021, 54(5): 1073-1080. doi: 10.3864/j.issn.0578- 1752.2021.05.018.(in Chinese)
[7] YIN D, GENG R H, LV H, BAO C H, SHAO H X, YE J Q, QIAN K, QIN A J. Development of real-time PCR based ongene for the detection of African swine fever virus. Frontiers in Veterinary Science, 2021, 8: 753967.
[8] BANKO A, PETROVIC G, MILJANOVIC D, LONCAR A, VUKCEVIC M, DESPOT D, CIRKOVIC A. Comparison and sensitivity evaluation of three different commercial real-time quantitative PCR kits for SARS-CoV-2 detection. Viruses, 2021, 13(7): 1321.
[9] SWAYNE D E, GLISSON J R, MCDOUGALD L R, NOLAN L K, SUAREZ D L, NAIR V L. Diseases of Poultry. 13th edition. New Jersey: Wiley-Blackwell, 2013
[10] ROZINS C, DAY T, GREENHALGH S. Managing Marek’s disease in the egg industry. Epidemics, 2019, 27: 52-58.
[11] 崔治中, 蘇帥, 羅俊, 錢琨, 莊國慶, 孫愛軍, 滕蔓. 雞馬立克病毒的研究進(jìn)展. 微生物學(xué)通報(bào), 2019, 46(7): 1812-1826.
CUI Z Z, SU S, LUO J, QIAN K, ZHUANG G Q, SUN A J, TENG M. Progress in Marek’s disease virus. Microbiology China, 2019, 46(7): 1812-1826. (in Chinese)
[12] SHI M Y, LI M, WANG W W, DENG Q M, LI Q H, GAO Y L, WANG P K, HUANG T, WEI P. The emergence of a vv + MDV can break through the protections provided by the current vaccines. Viruses, 2020, 12(9): 1048.
[13] AFONSO C L, TULMAN E R, LU Z, ZSAK L, ROCK D L, KUTISH G F. The genome of Turkey herpesvirus. Journal of Virology, 2001, 75(2): 971-978.
[14] 中國獸藥典委員會(huì). 中華人民共和國獸藥典-三部: 2020年版. 北京: 中國農(nóng)業(yè)出版社, 2020.
Chinese Veterinary Pharmacopoeia Commission. People’s republic of China (PRC) veterinary medicine code-part III: 2020 edition. Beijing: China Agriculture Press, 2020. (in Chinese)
[15] European Pharmacopoeia Commission. European pharmacopoeia (6th Edition), 2007.
[16] BRUCKNER L, OTTIGER H P. Pre-validation study for testing of avian viral vaccines for extraneous agents by PCR. Pharmeuropa Bio, 2007, 2007(1): 15-18.
[17] OTTIGER H P. Development, standardization and assessment of PCR systems for purity testing of avian viral vaccines. Biologicals, 2010, 38(3): 381-388.
[18] 世界動(dòng)物衛(wèi)生組織. OIE陸生動(dòng)物診斷試驗(yàn)和疫苗手冊(cè)(哺乳動(dòng)物、禽鳥與蜜蜂)第五版. 農(nóng)業(yè)部獸醫(yī)局譯, 北京: 中國農(nóng)業(yè)出版社, 2017.
World Organization for Animal Health. OIE Manual of Diagnostic Tests and Vaccines for Terrestrial Animals (Mammals, Birds and Bees) 5th Edition. Veterinary Bureau of the Ministry of Agriculture translate, Beijing: China Agriculture Press, 2017. (in Chinese)
[19] 國家市場(chǎng)監(jiān)督管理總局,國家標(biāo)準(zhǔn)化管理委員會(huì). 中華人民共和國國家標(biāo)準(zhǔn)GB/T 18648-2020.
State Administration for Market Regulation, Standardization Administration. National standards of People's Republic of China GB/T 18648-2020. (in Chinese)
[20] KUT E, RASSCHAERT D. Assembly of Marek’s disease virus (MDV) capsids using recombinant baculoviruses expressing MDV capsid proteins. The Journal of General Virology, 2004, 85(Pt 4): 769-774.
[21] BARFOED A M, ?STERGAARD E, FRANDSEN P L, NIELSEN E B, SANDBERG E, RASMUSSEN T B. Development of a primer-probe energy transfer based real-time PCR for detection of Marek’s disease virus. Journal of Virological Methods, 2010, 165(1): 21-26.
[22] MOODY M, ALVES W, VARGHESE J, KHAN F. Mouse minute virus (MMV) contamination: a case study: detection, root cause determination, and corrective actions. PDA Journal of Pharmaceutical Science and Technology, 2011, 65(6): 580-588.
[23] LI Q C, ZHANG Y B, MENG F F, JIANG H, XU G L, DING J B, ZHANG Y W, DONG G W, TIAN S B, CHANG S, ZHAO P. A new strategy for the detection of chicken infectiousvirus contamination in attenuated live vaccine by droplet digital PCR. BioMed Research International, 2019, 2019: 2750472.
[24] MOTITSCHKE A, OTTIGER H P, JUNGB?CK C. Evaluation of the sensitivity of PCR methods for the detection of extraneous agents and comparison withtesting. Biologicals, 2010, 38(3): 389-392.
[25] 尚宏華, 郭建平, 謝秋梅. 豬瘟活疫苗外源病毒BVDV細(xì)胞培養(yǎng)與PCR檢測(cè)的比較. 江西畜牧獸醫(yī)雜志, 2014(6): 8-10.
SHANG H H, GUO J P, XIE Q M. Comparison of BVDV cell culture and PCR detection of classical swine fever live vaccine. Jiangxi Journal of Animal Husbandry & Veterinary Medicine, 2014(6): 8-10. (in Chinese)
[26] MACKAY D, KRIZ N. Current challenges in viral safety and extraneous agent testing. Biologicals, 2010, 38(3): 335-337.
[27] 呂紅超, 張艷萍, 孫國榮, 高玉龍, 李志杰, 鄭惠文, 包珂巖, 王笑梅, 劉長(zhǎng)軍. 雞馬立克氏病強(qiáng)弱病毒株P(guān)CR鑒別檢測(cè)方法在診斷中的應(yīng)用評(píng)價(jià). 中國預(yù)防獸醫(yī)學(xué)報(bào), 2016, 38(7): 567-571.
Lü H C, ZHANG Y P, SUN G R, GAO Y L, LI Z J, ZHENG H W, BAO K Y, WANG X M, LIU C J. Assessments of a PCR method for detection and identification of virulent Marek’s disease virus and vaccine strain for Marek’s disease diagnosis. Chinese Journal of Preventive Veterinary Medicine, 2016, 38(7): 567-571. (in Chinese)
[28] 周冬玉, 李國紅, 靳澤華, 徐巧霞, 徐蓉, 張安定. 雞馬立克氏病病毒和疫苗毒株P(guān)CR診斷方法的建立及其應(yīng)用. 現(xiàn)代畜牧獸醫(yī), 2022(8): 50-54.
ZHOU D Y, LI G H, JIN Z H, XU Q X, XU R, ZHANG A D. Establishment and application of PCR diagnosis method for chicken Marek’s disease virus and vaccine virus. Modern Journal of Animal Husbandry and Veterinary Medicine, 2022(8): 50-54. (in Chinese)
[29] 李學(xué)伍, 劉媛, 王麗, 鄧瑞廣, 趙東, 楊繼飛, 柴書軍. 雞3種主要DNA病毒多重感染復(fù)合PCR檢測(cè)方法的建立. 河南農(nóng)業(yè)科學(xué), 2017, 46(7): 101-105.
LI X W, LIU Y, WANG L, DENG R G, ZHAO D, YANG J F, CHAI S J. Establishment of multiplex PCR detection method for three kinds of main DNA viruses in chicken. Journal of Henan Agricultural Sciences, 2017, 46(7): 101-105. (in Chinese)
[30] 屈素潔, 施開創(chuàng), 胡杰, 張步嫻, 尹彥文, 粟艷瓊, 莫?jiǎng)偬m, 李軍, 鄒聯(lián)斌. 熒光定量PCR檢測(cè)雞馬立克氏病血清1型病毒方法的建立及應(yīng)用. 上海畜牧獸醫(yī)通訊, 2015(4): 19-21.
QU S J, SHI K C, HU J, ZHANG B X, YIN Y W, SU Y Q, MO S L, LI J, ZOU L B. Establishment and application of fluorescence quantitative PCR method for detecting Marek’s disease serum type 1 virus in chickens. Shanghai Journal of Animal Husbandry and Veterinary Medicine, 2015(4): 19-21. (in Chinese)
[31] 閆彩虹. 江蘇地區(qū)家禽4種免疫抑制病病原檢測(cè)及致瘤病毒三重?zé)晒舛縋CR檢測(cè)方法的建立與應(yīng)用[D]. 揚(yáng)州: 揚(yáng)州大學(xué), 2020.
YAN C H. Establishment and application of triple fluorescence quantitative PCR method for detection of pathogens of four immunosuppressive diseases in poultry in Jiangsu Province[D]. Yangzhou: Yangzhou University, 2020. (in Chinese)
[32] 汪最, 李麗, 劉鵬, 劉麗娜, 汪琛, 周康, 羅青平. ALV-J、REV和MDV多重?zé)晒舛縋CR檢測(cè)方法的建立. 中國動(dòng)物傳染病學(xué)報(bào), 2020, 28(6): 73-78.
WANG Z, LI L, LIU P, LIU L N, WANG C, ZHOU K, LUO Q P. Establishment of a triple real-time pcr for detecting alv-j, rev and mdv. Chinese Journal of Animal Infectious Diseases, 2020, 28(6): 73-78. (in Chinese)
[33] LóPEZ-OSORIO S, VILLAR D, PIEDRAHITA D, RAMíREZ- NIETO G, NAIR V, BAIGENT S, CHAPARRO-GUTIéRREZ J. Molecular detection of Marek’s disease virus in feather and blood samples from young laying hens in Colombia. Acta Virologica, 2019, 63(4): 380-391.
[34] ZHANG Z J, LIU S Q, MA C T, ZHAO P, CUI Z Z. Absolute quantification of a very virulent Marek’s disease virus dynamic quantity and distributions in different tissues 1. Poultry Science, 2015, 94(6): 1150-1157.
[35] SU S, CUI N, ZHOU Y, CHEN Z M, LI Y P, DING J B, WANG Y X, DUAN L T, CUI Z Z. A recombinant field strain of Marek’s disease (MD) virus with reticuloendotheliosis virus long terminal repeat insert lacking the meq gene as a vaccine against MD. Vaccine, 2015, 33(5): 596-603.
[36] WAJID S J, KATZ M E, RENZ K G, WALKDEN-BROWN S W. Prevalence of Marek’s disease virus in different chicken populations in Iraq and indicative virulence based on sequence variation in the ecoRI-q (meq) gene. Avian Diseases, 2013, 57(2 Suppl.): 562-568.
[37] MESCOLINI G, LUPINI C, FELICE V, GUERRINI A, SILVEIRA F, CECCHINATO M, CATELLI E. Molecular characterization of thegene of Marek’s disease viruses detected in unvaccinated backyard chickens reveals the circulation of low- and high-virulence strains. Poultry Science, 2019, 98(8): 3130-3137.
[38] MURATA S, HASHIGUCHI T, HAYASHI Y, YAMAMOTO Y, MATSUYAMA-KATO A, TAKASAKI S, ISEZAKI M, ONUMA M, KONNAI S, OHASHI K. Characterization of Meq proteins from field isolates of Marek’s disease virus in Japan. Infection, Genetics and Evolution, 2013, 16: 137-143.
[39] MURATA S, YAMAMOTO E, SAKASHITA N, MAEKAWA N, OKAGAWA T, KONNAI S, OHASHI K. Research Note: characterization of S-Meq containing the deletion in Meq protein’s transactivation domain in a Marek’s disease virus strain in Japan. Poultry Science, 2021, 100(11): 101461.
[40] MOHAMED M H A, EL-SABAGH I M, AL-HABEEB M A, AL-HAMMADY Y M. Diversity of Meq gene from clinical Marek’s disease virus infection in Saudi Arabia. Veterinary World, 2016, 9(6): 572-578.
[41] GUPTA M, DEKA D. Sequence analysis of Meq oncogene among Indian isolates of Marek’s disease herpesvirus. Meta Gene, 2016, 9: 230-236.
[42] GIMENO I M, DUNN J R, CORTES A L, EL-GOHARY A E G, SILVA R F. Detection and differentiation of CVI988 (Rispens vaccine) from other serotype 1 Marek’s disease viruses. Avian Diseases, 2014, 58(2): 232-243.
[43] BAIGENT S J, NAIR V K, LE GALLUDEC H. Real-time PCR for differential quantification of CVI988 vaccine virus and virulent strains of Marek’s disease virus. Journal of Virological Methods, 2016, 233: 23-36.
[44] CORTES A L, MONTIEL E R, LEMIERE S, GIMENO I M. Comparison of blood and feather pulp samples for the diagnosis of Marek’s disease and for monitoring Marek’s disease vaccination by real time-PCR. Avian Diseases, 2011, 55(2): 302-310.
[45] ISLAM A, CHEETHAM B F, MAHONY T J, YOUNG P L, WALKDEN-BROWN S W. Absolute quantitation of Marek’s disease virus and Herpesvirus of turkeys in chicken lymphocyte, feather tip and dust samples using real-time PCR. Journal of Virological Methods, 2006, 132(1/2): 127-134.
[46] 李冬冬. 重組火雞皰疹病毒rHVT-VP2實(shí)時(shí)熒光定量PCR檢測(cè)方法的建立及應(yīng)用[D]. 南京: 南京農(nóng)業(yè)大學(xué), 2017.
LI D D. Establishment and application of real-time fluorescence quantitative PCR detection method for recombinant Turkey herpesvirus rHVT-VP2[D]. Nanjing: Nanjing Agricultural University, 2017. (in Chinese)
Establishment of Real-Time PCR Method for Detection of Extraneous Marek’s Disease Virus
SU Jia, ZHAO Wei, LIU Dan, WANG Jia, BAI HongXu, WU HuaWei, XUE QingHong, CHEN XiaoChun
China Institute of Veterinary Drug Control, Beijing 100081
【Objective】 In order to solve the problems of low sensitivity, long detection time, and poor discrimination of existing exogenous Marek’s disease virus (MDV) testing methods, this study was designed to establish two real-time PCR detection methods for the identification of MDV serotype 1 (MDV 1) and MDV serotype 3 (MDV 3) strains, which could be used for purity control of poultry-derived biological products. 【Method】Thesequences of MDV 1, MDV serotype 2 (MDV 2) and MDV 3 strains were downloaded from the NCBI database and were used for nucleotide and amino acid homology comparison. A pair of specific primers and corresponding Taqman probe was designed from the known sequence of conservedof MDV 1 CVI988 strain and MDV 3 FC126 strain, respectively, and two real-time PCR detection methods were established. The corresponding recombinant plasmids were constructed and used as positive standards to make standard curves, and the sensitivity of gene copy number of the methods were evaluated. Other avian virus-associated biological products, virus, the full-length plasmid ofof MDV 2 SB-1 strain and the raw materials for production (SPF chicken embryo allantoic fluid, embryonic body, allantoic membrane, chicken embryo fibroblasts) were detected to evaluate the specificity of the established methods. 600, 60, 6, 0.6, 0.06, 0.006 and 0.0006 PFU of CVI988 or FC126 strains were detected, respectively, and the sensitivity of the established two methods for detecting live virions was evaluated. Three repeatability tests were performed using corresponding recombinant plasmids of different dilutions, and the correlation coefficient were calculated to analyze the reproducibility of the two established detection methods. 【Result】 The nucleotide and the derived amino acid homology of MDV=-3.351+38.828 (= Ct,= lg ( copy number)). About the MDV 3 real-time PCR detection method, the amplification efficiency was 95%, the correlation coefficient was 0.998, and the standard curve:=-3.447+36.496 (= Ct,= lg ( copy number)). The established detection methods could specially detect MDV 1 or MDV 3 without detecting any other avian virus-associated biological products, virus, the full-length plasmid ofof MDV 2 SB-1 strain, along with production materials for poultry. The sensitivity of MDV 1 real-time PCR detection method was high, with the gene copy number detection limit of 32.8 copies/μL, which could detect at least 0.006 PFU of CVI988 strain. The sensitivity of MDV 3 real-time PCR detection method was high, with the gene copy number detection limit of 10 copies/μL, which could detect at least 0.006 PFU of FC126 strain. The coefficient of variation of the repeatability test was less than 1% in MDV 1 real-time PCR detection method, and less than 1.5% in MDV 3 real-time PCR detection method, respectively. 【Conclusion】 The established real-time PCR detection methods would be beneficial for detecting exogenous MDV 1 and MDV 3 strains in poultry-derived biological products.
Marek’s disease virus; real-time PCR; extraneous virus; detection
10.3864/j.issn.0578-1752.2023.20.016
2022-11-11;
2023-04-04
獸藥行業(yè)公益性重點(diǎn)項(xiàng)目(GY202105)
蘇佳,E-mail:hnzk912@163.com。通信作者陳曉春,E-mail:chunxiao1981@126.com
(責(zé)任編輯 林鑒非)