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標題: 雞傳染性鼻炎菌cdtABC毒素蛋白基因之發現與功能分析
Identification and Functional Analyses of cdtABC Toxin Genes from Avibacterium paragallinarum
作者: 陳意超
Chen, Yi-Chau
Contributors: 張伯俊
Poa-Chun Chang
關鍵字: 雞傳染性鼻炎
Avibacterium paragallinarum
日期: 2013
Issue Date: 2013-11-19 12:51:23 (UTC+8)
Publisher: 微生物暨公共衛生學研究所
摘要: 雞傳染性鼻炎(infectious coryza, IC) 為傳播快速的呼吸道傳染病,病源為Avibacterium paragallinarum,雞隻在感染此病原後會造成體重下降、淘汰率增加,以及產蛋量下降,造成經濟損失。IC目前可以不活化全菌疫苗免疫來預防,但Av. paragallinarum血清型可分 A、B、C三型,彼此之間無交叉保護的效果,形成防疫上之難題。CDT (Cytolethal distending toxin) 已知為許多革蘭氏陰性菌的重要毒素蛋白,完整的CDT分為CdtA、CdtB、CdtC三個次單位,CdtA與CdtC會和細胞膜上的受器結合將CdtB送入胞內,CdtB具有DNase活性可造成細胞DNA斷裂,使細胞週期停滯進而凋亡。本研究首度發現 Av. paragallinarum 之cdt基因序列並探討Cdt蛋白表現與蛋白活性分析,並以動物實驗測試Cdt蛋白做為疫苗之潛力。選用台灣分離血清型C型的野外株TW07,將其cdt基因序列分成cdtABC全長,以及cdtA、cdtB、cdtC四種片段進行蛋白表現,將表現好的全長蛋白以及組合的片段蛋白進行細胞毒性試驗,片段蛋白也分別製成重組蛋白疫苗進行動物實驗觀察是否有保護力。CdtB蛋白則進行DNase活性測試。結果顯示重組CdtB蛋白具有DNase活性,重組CDT全長蛋白具有細胞毒殺與停滯細胞週期的毒性。本研究為首度發現雞傳染鼻炎菌具有cdtABC基因,並證實其具有DNase活性及細胞毒性。
Infectious coryza is an important respiratory disease of chickens caused by Avibacterium paragallinarum in many areas of the world. It is characterised clinically by acute respiratory signs in layer chickens, often accompanied by swelling of the face, nasal discharge, reduced egg production, and increased culling rate in broiler flocks. Although inactivated whole-cell vaccines of A. paragallinarum are widely available, outbreaks of infectious coryza continue to occur and cause significant economic loss worldwide. Cytolethal distending toxin (CDT) is a newly known virulence factor found in a variety of Gram-negative pathogenic bacteria. CDT is an a tripartite complex toxin, in which the CdtA and CdtC subunits are required for binding on the surface of the target cells and allowing internalization of the active CdtB subunit. CdtB is functionally homologous to the mammalian deoxyribonuclease I. The aim of this study was to investigate the function of cdt genes of Av. paragallinarum TW07 (serovar C) and development of recombinant subunit vaccines. The result showed that recombinant CdtB protein from Av. paragallinarum has nuclease activity in vitro and the recombinant CdtABC proteins are able to induce cell death and cellular distension. Recombinant protein contain CDT regions might have potential to be used as the antigens for subunit vaccines against Av. paragallinarum. This study shows for the first time that cdtABC genes are present in Av. paragallinarum. The CDT may be considered a virulence factor of Av. paragallinarum and it may have potential to be used as a antigen for subunit vaccines.
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