1、獨(dú)創(chuàng)性聲明本人鄭重聲明：所呈交的學(xué)位論文，是本人在導(dǎo)師指導(dǎo)下，進(jìn)行研究工作所取得的成果。除文中已經(jīng)注明引用的內(nèi)容外，本學(xué)位論文的研究成果不包含任何他人創(chuàng)作的、己公開(kāi)發(fā)表或者沒(méi)有公開(kāi)發(fā)表的作品的內(nèi)容，也不包含為獲得中國(guó)獸醫(yī)藥品監(jiān)察所或其它教育機(jī)構(gòu)的學(xué)位或證書(shū)而使用過(guò)的材料。對(duì)本論文所涉及的研究工作做出貢獻(xiàn)的其他個(gè)人和集體，均已在文中以明確方式標(biāo)明。本學(xué)位論文原創(chuàng)性聲明的法律責(zé)任由本人承擔(dān)。學(xué)位論文作者簽名：宮世葭2。燁年6月(7日關(guān)于論文

2、使用授權(quán)的說(shuō)明本人完全了解中國(guó)獸醫(yī)藥品監(jiān)察所有關(guān)保留、使用學(xué)位論文的規(guī)定，即：中監(jiān)所有權(quán)保留送交論文的復(fù)印件和磁盤(pán)，允許論文被查閱和借閱，可以采用影印、縮印或掃描等復(fù)制手段保存、匯編學(xué)位論文。同意中國(guó)獸醫(yī)藥品監(jiān)察所可以用不同方式在不同媒體上發(fā)表、傳播學(xué)位論文的全部或部分內(nèi)容。(保密的學(xué)位論文在解密后應(yīng)遵守此協(xié)議)研究生簽名：官世在時(shí)間：zoti4年6月日剔噬轢身踺艇：川諺。乒≥日中國(guó)獸醫(yī)藥品監(jiān)察所碩士學(xué)位論文ABSTRACTABSTRA

3、CTInfectiousbursaldisease(IBD)isanacuteandhighlycontagiousviraldiseaseofyoungchickenscausedbyInfectiousbursaldiseasevirus(IBDV)TheepidemicofveryvirulentIBDVstrainsinthe1atel980smakethecauseofthevirulencevariationofIBDVbe

4、comethefocusofresearchButsofarthevirulencefactorofIBDVwasnotclearInordertoprovidemoremolecularbasisforthevirulenceofIBDvtheattenuatedIBDVstrainswereseriallypassagedinspecificpathogen—free(SPF)chickensinthisstudyandthegen

5、omesequencesoftheattenuatedⅢDVstrainsandthepassagestrainsinchickenswereamplifiedandanalyzedAtthesametimetheIBDVE2strainwaspassaged4successivetimesinchickenembryo，andthethegenomesequencesoftheE2strainandthepassagestrainsi

6、nchickenembryoweTeamplifiedandanalyzedThemainresultsinthisstudyareasfollows：(1】TwoattenuatedIBDVstrainswerepassagedfiveorsixtimesinSPFchickensBothattenuatedstrainsincreasedinvirulenceduringthepassageinsusceptiblechickens

7、asevidencedbythedecreaseinbursa／bodyweightratiosandB：Bindex(2)ThegenomesequencesoftheattenuatedmDVstrainsandthepassagestrainsinchickensweresegmentallyamplifiedbyR]rPCRandmolecularclonetechnologyAdirectsequencealignmentan

8、alysisresultsshowedthatthegenomeBsegmentwereconservativewithnonucleotidemutationduringthepassageinchickens；however，therewere5nueleotidemutationsingenomeAsegment，whichresultedin3aminoacidsubstitutionsatposition80(fromRtoG

9、)、125(fromPtoS1andl30(fromCt)invP5，加aminoacidsubstitudonatposition253(fromHtoQorN)inVP2andanaminoacidsubstitutionatposition778(fromVtoM)inVP3Furtherhomologousanalysisdemonswatedthatthemutationofaminoacidatposition253inVP

10、2madethestrainsafterpassageinchickenshaveahigheridentitywiththeclassicalstrainsandtheveryvirulentstrains，andaloweridentitywiththeattenuatedstrains；Thoseresultssuggestedthatthemutationofaminoacidat253siteinVP2maybeoneofth

11、emolecularmechanismofIBDVvirulenceenhancementduringthepassageinchickensThe3DstructurepredictionofVP2revealedthataminoacidresidueatposition253exposedatthesurfaceofVP2projecdondomaindemostratingtheaminoacidmutationfromHtoQ

12、orNatthissitemayimproveitshydrophilicitywhichmayfacilitatetheinteractionbetweenmDVandthecellreceptorinthehost，soastoincreasethepathogenicityofIBDV(3)SequenceanalysisoftheIBDVE2strainanditspassagestrainsinchickenembryosho

13、wedthatthereweresomeuniqueaminoacidsvariationinVP2betweentheclassicalstrainsandtheattenuatedstrains：253(Q’H)、279(DN)、284(A—T)、330(SR)，whichfurtherelucidatedthemolecularmechanismofIBDVvimlenceagenuationduringthepassageinc