Wang Yong, Ge Jinying, Ding Yulin, Xie Xidi, Bu Zhigao
National Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, China.
Wei Sheng Wu Xue Bao. 2008 May;48(5):638-43.
The hemagglutinin-neuraminidase (HN) and fusion protein of Newcastle disease virus (NDV) plays a crucial role in the process of budding and infection. To understand the exact contribution of the HN gene to NDV pathogenecity, a reverse genetics system was developed using the lentogenic NDV LaSota strain .
the HN genes of an avirulent recombinant NDV strain (rLaSota) was replaced by an HN gene from Mukteswar mesogenic NDV strain by reverse genetics. Furthermore, the F gene of rL-MuHN was replaced with that of Mukteswar strain, resulting the double genes replaced chmeric virus, rL-MuFHN.
Although the rescued chimeric virus (rL-MuHN) did not show significant increase in ability of hemadsorption, the intracerebral pathogenicity index test (ICPI = 0) in chickens and mean death time for eggs (MDT > or = 90 h). rL-MuHN kept the low pathogenicity similar to its parent rLaSota strain. Compared to single gene replaced rL-MuHN, rL-MuFHN induced stronger cell fusion and showed a mild increase in ICPI (from 0 to 0.59) and no significant change in MDT (> or = 90 h). rL-MuFHN showed much lower pathogenicity than that of Mukteswar (ICPI. = 1.32 and MDT = 46, respectively). A HN gene exchange alone within the context of the NDV rLaSota backbone failed to increase virus virulence from unvelogenic to mesogenic pathotype.
These results indicated that the virulence of NDV is determined multigenically. The heterotypic HN and F pairs were not equally effective in virus pathogenicity. The HN gene derivated from mesogenic strain dose not alter the lentogenic property of NDV LaSota strain. NDV can be manipulated by gene replacement in the future for use as a vaccine candidate.
新城疫病毒（NDV）的血凝素神经氨酸酶（HN）和融合蛋白在出芽和感染过程中起关键作用。为了解HN基因对NDV致病性的确切贡献，利用弱毒NDV LaSota株建立了反向遗传系统。
通过反向遗传学，将无毒重组NDV株（rLaSota）的HN基因替换为 Mukteswar中等毒力NDV株的HN基因。此外，将rL-MuHN的F基因替换为Mukteswar株的F基因，得到双基因替换嵌合病毒rL-MuFHN。
虽然拯救的嵌合病毒（rL-MuHN）的血细胞吸附能力没有显著增加，但鸡的脑内致病性指数试验（ICPI = 0）和鸡胚平均死亡时间（MDT≥90小时）。rL-MuHN保持了与其亲本rLaSota株相似的低致病性。与单基因替换的rL-MuHN相比，rL-MuFHN诱导更强的细胞融合，ICPI略有增加（从0增加到0.59），MDT无显著变化（≥90小时）。rL-MuFHN的致病性远低于Mukteswar株（ICPI分别为1.32和MDT为46）。仅在NDV rLaSota骨架背景下进行HN基因交换未能将病毒毒力从非致病毒型提高到中等毒力型。
这些结果表明，NDV的毒力是由多个基因决定的。异型HN和F对在病毒致病性方面的效果并不相同。源自中等毒力株的HN基因不会改变NDV LaSota株的弱毒特性。未来可通过基因替换操作NDV用作候选疫苗。
