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標題: | 臺灣自2000至2013年間H6N1禽流感病毒之基因、受體親和性、複製動力學與病原性分析 Assessment of Genetic, Receptor Binding, Replication Kinetics and Pathogenicity Features of H6N1 Avian Influenza Viruses Identified in Taiwan during 2000 to 2013 |
作者: | Yi-Chi Wen 温意琪 |
指導教授: | 陳慧文(Hui-Wen Chen) |
關鍵字: | 禽流感病毒,H6N1,序列分析,受體結合親和性,複製動力學,聚合?活性,病原性,免疫反應, Avian influenza virus,H6N1,Sequence analysis,Receptor binding specificity,Growth kinetics,Polymerase activity,Pathogenicity,Immune response, |
出版年 : | 2018 |
學位: | 碩士 |
摘要: | H6亞型禽流感病毒的感染遍及全球,1965年首次自美國麻薩諸塞州的火雞分離到病毒。H6亞型禽流感病毒被視為1997年香港的高病原性H5N1亞型禽流感病毒和2004年台灣高病原性H5N2亞型禽流感病毒的共同祖先群,而此群H6亞型病毒目前仍持續在亞洲的鳥群間傳播。為更加了解於台灣田間流行的H6亞型禽流感病毒特性,本研究以2000至2013年間之H6N1禽流感病毒雞隻分離株進行分析,包含基因體序列、血清抗原性、受體結合親和性、複製動力學、聚合酶活性,以及在雞隻所造成的病原性和免疫反應分析。結果顯示,本研究所分析的19株H6N1病毒可依其HA蛋白質基因序列歸類於不同之分支,主要的遺傳變異累積在HA之球狀頭部區域,並發生血清抗原性的改變,其中2012年後形成之新分支與2013年感染人、及2014年感染犬隻的H6N1分離株同源性甚高,多數的雞隻分離株在HA蛋白質第228個胺基酸變異為具哺乳類適應性的分子特徵 (G228S),且多數分離株中NA蛋白質莖部有12至14個胺基酸的缺損,可能造成病毒致病能力增強。雖然本研究中多數的H6亞型禽流感病毒仍保有對α2,3鍵結唾液酸(禽類型)的結合特異性,但部分新分離株顯示對於α2,6鍵結唾液酸(哺乳類型)有中等之結合能力,且這些毒株不需預先適應,即可有效率地在哺乳類MDCK細胞中複製,並在禽類細胞中有顯著較高之聚合酶活性。在SPF雞隻感染試驗中,新分支中的毒株可在雞隻之呼吸道與腎臟大量複製、快速排毒,並在腎臟產生較高之病原性,而病毒感染後誘導雞隻肺臟表現之Mx1 可能在清除病毒、降低致病性之免疫反應中扮演重要角色。綜合以上,與感染哺乳類之毒株相似的H6N1禽流感病毒正持續在台灣的雞群中傳播、逐漸累積變異,實為公共衛生之隱憂,我們對於H6亞型禽流感病毒需要建立更嚴密的監控與有效的防治策略。 Avian influenza virus (AIV) subtype H6 is distributed worldwide since its first identification from turkeys in Massachusetts, USA in 1965. H6 AIVs were identified as potential progenitors of the highly pathogenic H5N1 AIV that emerged in Hong Kong in 1997 and H5N2 AIV in Taiwan in 2004, and these H6 viruses continue to circulate among the bird populations in Asia. To better understand the mammalian-adapted signatures of H6 AIVs in the field of Taiwan, we analyzed the genetic/antigenic relationship, receptor binding specificity, growth kinetics in vitro, polymerase activity, pathogenicity in vivo and immune responses of the H6 chicken isolates identified between 2000 and 2013 in Taiwan. The analyzed H6 AIVs present frequent substitutions in the globular head domain of the HA protein, undergoing antigenic changes, and can be classified into different clades. Notably, the HA and NA proteins of the new clade of chicken isolates share high sequence homology with the H6N1 human isolate identified in 2013 and the dog isolate found in 2014. Most of the H6 chicken isolates carry the molecular signature for mammalian adaptation, ie. the G228S substitution in the HA protein, and the pathogenicity determinant, ie. a 12-14 a.a. deletion in the NA stalk. While most of the studied H6 AIVs retained the binding specificity to the α2,3-linked sialic acid (avian type), some of the recently isolated strains showed moderate binding to the α2,6-linked sialic acid (mammalian type). The growth kinetic studies in vitro exhibited these H6 AIVs can grow efficiently in MDCK cells without prior adaptation. In the polymerase activity assay, the new clade of H6N1 AIV showed significantly higher polymerase activity than the older virus in avian cells. Upon the experimental infection in SPF chickens, the new clade of H6N1 AIV showed enhanced kidney pathogenesis, rapid shedding, and productive virus replication in major organs including the trachea, lung, and kidney. Furthermore, the upregulation of Mx1 gene may play an important role in chicken immune response for viral clearance and in reducing the pathogenicity of viral infections. Collectively, the “human (or dog)-infecting”-like H6N1 strains continue to circulate among domestic chickens and accumulate changes, which pose a clear threat to public health. Therefore, evolution and spread of H6 AIVs should be closely monitored, and safe and effective preventive countermeasures are warranted. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/71263 |
DOI: | 10.6342/NTU201801912 |
全文授權: | 有償授權 |
顯示於系所單位: | 獸醫學系 |
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