Joint Department of Veterinary Medicine, Faculty of Agriculture, Tottori University, Tottori 680-8553, Japan.
The United Graduate School of Veterinary Science, Yamaguchi University, Yamaguchi 753-8511, Japan.
J Vet Med Sci. 2022 Jan 13;84(1):121-128. doi: 10.1292/jvms.21-0527. Epub 2021 Dec 2.
Although verogenic Newcastle disease viruses (NDVs) generally cause subclinical infection in waterfowls such as ducks, NDVs with high virulence in waterfowl have been sporadically reported. We previously reported that the NDV d5a20b strain, which is obtained by serial passaging of the velogenic 9a5b strain in domestic ducks, showed increased virulence in ducks (Hidaka et al., 2021). The d5a20b strain had 11 amino acid substitutions in its P/V, M, F, HN, and L proteins as compared to 9a5b. In the present study, we generated a series of recombinant (r) NDVs with these amino acid substitutions to identify the molecular basis of virulence of NDV in ducks, and evaluated their influences on virulence and in vitro viral properties. Each of the single amino acid substitutions in either the F protein I142M or the M protein Q44R contributed to the enhancement of intracerebral and intranasal pathogenicity in domestic ducks. The cell-cell fusion activity of the virus with F I142M was five times higher than that of the parental r9a5b. The virus with M Q44R rapidly replicated in duck embryo fibroblasts. Additionally, the rM+F+HN strain, which has the same amino acid sequences as d5a20b in M, F, and HN proteins, showed the highest level of virulence and replication efficiency among the generated recombinant viruses, nearly comparable to rd5a20b. These results suggest that multiple factors are involved in the high growth ability of NDV in duck cells, leading to increased virulence in vivo.
虽然禽源性新城疫病毒（NDV）通常在鸭等水禽中引起亚临床感染，但水禽中具有高毒力的 NDV 已被零星报道。我们之前报道过，通过在国产鸭中对强毒力的 9a5b 株进行连续传代获得的 NDV d5a20b 株，在鸭中表现出更高的毒力（Hidaka 等人，2021 年）。与 9a5b 相比，d5a20b 株在其 P/V、M、F、HN 和 L 蛋白中具有 11 个氨基酸取代。在本研究中，我们生成了一系列具有这些氨基酸取代的重组（r）NDV，以鉴定 NDV 在鸭中的毒力分子基础，并评估它们对毒力和体外病毒特性的影响。F 蛋白 I142M 或 M 蛋白 Q44R 中的单个氨基酸取代都有助于增强国产鸭的脑内和鼻腔致病性。具有 F I142M 的病毒的细胞间融合活性是亲本 r9a5b 的五倍。具有 M Q44R 的病毒在鸭胚成纤维细胞中快速复制。此外，在 M、F 和 HN 蛋白中具有与 d5a20b 相同氨基酸序列的 rM+F+HN 株在产生的重组病毒中显示出最高的毒力和复制效率，几乎可与 rd5a20b 相媲美。这些结果表明，多种因素参与了 NDV 在鸭细胞中的高生长能力，导致体内毒力增加。
