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The replication kinetics of different strains of Marek's disease virus (MDV) and evaluation of the vaccine regime in Taiwan
|關鍵字:||馬立克病;馬立克病毒;病毒分佈||出版社:||獸醫學系暨研究所||引用:||1 呂榮修。馬立克病。禽病診斷彩色圖譜。中華民國養雞協會。台北市。中華民國。255-263，1995。 2 李宗玄。台灣高病原性馬立克病毒之分離、鑑定及其防疫計劃之建立。國立中興大學。碩士論文。1995。 3 吳龍泰。馬立克病對肉雞影響之研究。國立中興大學。碩士論文。1997。 4 許添桓。台灣雞馬立克病毒之研究。國立中興大學。碩士論文。1989。 5 Abdul-Careem MF, Hunter BD, Nagy E, Read LR, Sanei B, Spencer JL, Sharif S. Development of a real-time PCR assay using SYBR Green chemistry for monitoring Marek’s disease virus genome load in feather tips. J Virol Methods 133: 34-40, 2006. 6 Anderson AS, Francesconi A, Morgan RW. Complete nucleotide sequence of the Marek’s disease virus ICP4 gene. Virology 189: 657–667, 1992. 7 Bacon LD, Witter RL, Silva RF. Characterization and experimental reproduction of peripheral neuropathy in White Leghorn chickens. Avian Patho 30: 487–499, 2001. 8 Baigent SJ, Davison TF. Marek’s disease virus: biology and life cycle. In: Davison, F., Nair, V. (Eds.), Marek’s Disease, an Evolving Problem. 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馬立克病（Marek’s disease, MD）是一種雞的傳染性致腫瘤性疾病，由馬立克病毒（Marek’s disease virus, MDV）引起，造成T細胞淋巴瘤。自1970年MD活毒疫苗開始使用後，已大幅降低馬立克疫情所造成的經濟損失。然而，MDV的毒力日益增強，從疫苗接種過的雞群中陸續分離到超強毒株vvMDV（very virulent MDV），故重新檢討台灣現階段的免疫計畫是很重要的。因此本實驗目的為研究MDV的病毒複製動力學，選用市售疫苗CVI988、HVT以及本實驗室所分離到的野外分離株DW-1，來觀察疫苗株與野外株，彼此間複製動力學的相關性，在病毒接種後1-20天，間隔2天採樣一次，每次共採集14個臟器樣本，利用PCR診斷技術來偵測病毒核酸的存在，同時也觀察疫苗接種對於DW-1病毒複製的影響。結果顯示疫苗接種對於DW-1的早期複製有抑制的效果，這可以幫助我們進一步了解疫苗在各臟器中的分佈情形與保護效力，我們也利用腎臟組織細胞（Chicken kidney cell, CKC）來觀察比較病毒於 in vivo 和 in vitro 的生長情形，於攻毒後第二週、第三週和第四週，將攻毒的雞隻以人道方式犧牲取其腎臟作初代組織培養，計算PFU（Plaque formation unit）的生成數量，結果顯示疫苗對於DW-1的病毒複製能力有些微的抑制效果，但是抑制能力也有限，最終無法抑制攻毒的雞隻發病，這結果與 in vivo 試驗相符合，這些發現有助於日後疫苗計畫的擬定，發展一套更好的馬立克防疫策略，將疾病造成的經濟損失降至最低。
Marek's disease (MD) is one of the most contagious oncogenic lymphotrophic diseases in chicken caused by MDV. In past 30 years, the use of MDV live vaccines have greatly reduced the economic losses from MD. However, vaccines themselves are thought to be responsible for driving the virulence. After the isolation of very virulent MDV (vvMDV) from vaccinated flocks, it is important to evaluate recent vaccine regimes in Taiwan. To investigate the correlation between virus replication kinetics and vaccination, viruses from vaccine strains CVI988 (Rispens), HVT, and very virulent strain DW-1 were used to evaluate virus replication kinetics. We used PCR technique to detect virus in 14 organs in day 1-20 post-vaccination at two-day interval. We also detected the virus of DW-1 and vaccine strains when challenged with or without vaccination. The results showed that the existence of vaccine strains can in vivo reduce the replication of field strain. However, chicken challenged with DW-1 strain enhanced the growth of HVT vaccine strain. It may help us to realize the correlation between vaccine level in different organs and protection. Moreover, we also used the CKC from challenged chickens with or without vaccination to compare the challenge virus yield. Specific plaques were calculated at 14-day after culture from each one, and the plaques of the very virulent DW-1 strain in infected chicken kidney cultures were shown significantly more than other cultures from HVT vaccinated chicken, the results indicated that the growth of field isolate was reduced in vaccinated chicken, in accordance to in vivo test. These findings are useful for developing the vaccine regime of MD in Taiwan.
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