14日齡雞胚胎累代感染造成之H5N2低病原性家禽流行性感冒病毒毒力變異

The Virulence Variation in a H5N2 Low Pathogenic Avian Influenza Virus after Passage in 14-day-old Chicken Embryonic Eggs

鄭明珠(Ming-Chu Cheng) ； 李敏旭(Ming-Shiuh Lee) ； 李淑慧(Shu-Hwae Lee) ； 王金和(Ching-Ho Wang)

《臺灣獸醫學雜誌》 37卷3期 (2011/09) Pp. 221-226

https://doi.org/10.7009/TVJ.201109.0221

摘要

為瞭解H5N2低病原性禽流感病毒毒力演化趨勢，以臺灣2003年12月分離之H5N2低病原性禽流感分離株1209/03進行試驗，設計以14日齡雞胚胎繼代感染後探討病原性變化情形。結果在無胰蛋白酶的培養液中，病毒對雞胚胎纖維芽細胞感染由第10代開始形成病毒斑，且ICPI由第5代之0.71提高為1.64，對細胞及腦部感染毒力明顯升高。有胰蛋白酶的培養之下，感染CEF細胞皆可形成病毒斑，但有大小之差異，第20代開始病毒斑由1.4mm變大為2.0mm。IVPI值在第40代時，由原來毒株的0提高為1.45；試驗結果顯示1209/03病毒經過14日齡雞胚胎繼代之後，毒力有逐代增強的趨勢。但值得注意的是，HA蛋白切割位胺基酸序列雖然在第20代及第30代由－REKR-之3個鹼性氨基酸轉變為－RRKKR-5個鹼性氨基酸，但在第40代及第50代又轉變回到原來的3個鹼性氨基酸序列，表示影響H5N2禽流感病毒的病原性不完全是HA切位鹼性胺基酸的多寡所決定。

關鍵字

家禽流行性感冒 ； 毒力變異 ； 14日齡雞胚胎繼代

並列摘要

In order to understand the virulence change of H5N2 low pathogenic avian influenza virus, the virus strain isolated in Taiwan in 2003 was used in this study. After serial passages in 14-day-old chicken embryonic eggs, the virulence of different passages were compared. The results showed that in the trypsin-free chicken fibroblast cell culture, the plaque formed in the 10(superscript th) passage, but not in the original and the 5(superscript th) passage. The intracerebral pathogenicity index (ICPI) in the 10(superscript th) passage was 1.64, higher than that in the 5(superscript th) passage of 0.71. The plaque sizes of 20th passage increased from 1.4 mm to 2.0 mm. The intravenous pathogenicity index (IVPI) of the 40(superscript th) passage was 1.45 (＞1.2), while the original strain was 0.0. All the tests indicated that, by passing in 14-day-old chicken embryo, the virulence of 1209/03 strain increased. However, the numbers of basic amino acid at the haemagglutinin cleavage were inconsistent among different passages. The amino acid sequence at the cleavage site changed from-REKR-in the original to-RRKKR-in the 20(superscript th) and the 30(superscript th) passages, and then changed back to-REKR-by the 40(superscript th) and the 50(superscript th) passages. Thus, the number of basic amino acid at the haemagglutinin cleavage site is not completely account for the virulence of the virus. Our study demonstrated that LPAI may gain virulence gradually when persisted or circulated in the field.

並列關鍵字

14-day-old chicken embryonic egg passage ； Avian Influenza Virus ； virulence variation