Department of Ecosystem and Public Health, Faculty of Veterinary Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada; Department of Zoonoses, Faculty of Veterinary Medicine, Cairo University, Giza 12211, Egypt.
Department of Ecosystem and Public Health, Faculty of Veterinary Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada; Department of Poultry Diseases, Faculty of Veterinary Medicine, Assiut University, Assiut 71515, Egypt.
Infect Genet Evol. 2022 Oct;104:105350. doi: 10.1016/j.meegid.2022.105350. Epub 2022 Aug 14.
Infectious laryngotracheitis (ILT), caused by infectious laryngotracheitis virus (ILTV), occurs sporadically in poultry flocks in Canada. Live attenuated chicken embryo origin (CEO) vaccines are being used routinely to prevent and control ILTV infections. However, ILT outbreaks still occur since vaccine strains could revert to virulence in the field. In this study, 7 Canadian ILTV isolates linked to ILT outbreaks across different time in Eastern Canada (Ontario; ON and Quebec; QC) were whole genome sequenced. Phylogenetic analysis confirmed the close relationship between the ON isolates and the CEO vaccines, whereas the QC isolates clustered with strains previously known as CEO revertant and wild-type ILTVs. Recombination network analysis of ILTV sequences revealed clear evidence of historical recombination between ILTV strains circulating in Canada and other geographical regions. The comparison of ON CEO clustered and QC CEO revertant clustered isolates with the LT Blen® CEO vaccine reference sequence showed amino acid differences in 5 and 12 open reading frames (ORFs), respectively. Similar analysis revealed amino acid differences in 32 ORFs in QC wild-type isolates. Compared to all CEO vaccine strains in the public domain, the QC wild-type isolates showed 15 unique mutational sites leading to amino acid changes in 13 ORFs. Our outcomes add to the knowledge of the molecular mechanisms behind ILTV genetic variance and provide genetic markers between wild-type and vaccine strains.
传染性喉气管炎（ILT）由传染性喉气管炎病毒（ILTV）引起，在加拿大的家禽群中零星发生。活的弱毒鸡胚源（CEO）疫苗被常规用于预防和控制 ILTV 感染。然而，由于疫苗株在野外可能恢复毒力，ILT 暴发仍时有发生。在这项研究中，对与加拿大东部不同时间（安大略省；ON 和魁北克省；QC）暴发的 ILT 相关的 7 株加拿大 ILTV 分离株进行了全基因组测序。系统发育分析证实了 ON 分离株与 CEO 疫苗之间的密切关系，而 QC 分离株与先前被称为 CEO 回复突变株和野生型 ILTV 的菌株聚集在一起。ILTV 序列的重组网络分析清楚地表明，加拿大和其他地理区域流行的 ILTV 株之间存在历史重组。对与 LT Blen® CEO 疫苗参考序列聚集的 ON CEO 株和 QC CEO 回复突变株聚集的分离株进行比较，发现 5 和 12 个开放阅读框（ORFs）中的氨基酸差异分别为 5 和 12。类似的分析显示，QC 野生型分离株中 32 个 ORF 中的氨基酸差异。与公共领域中所有 CEO 疫苗株相比，QC 野生型分离株在 13 个 ORF 中有 15 个独特的突变位点，导致氨基酸发生变化。我们的研究结果增加了对 ILTV 遗传变异背后的分子机制的认识，并提供了野生型和疫苗株之间的遗传标记。
