Saraiva Giuliana Loreto, Santos Marcus Rebouças, Pereira Claiton Gonçalves, Vidigal Pedro Marcus Pereira, Fietto Juliana Lopes Rangel, de Oliveira Mendes Tiago Antonio, Bressan Gustavo Costa, Soares-Martins Jamária A P, de Almeida Márcia Rogéria, Silva-Júnior Abelardo
Laboratório de Virologia Animal, Departamento de Veterinária, Universidade Federal de Viçosa, Av. PH Rolfs, s/n, Viçosa, MG, 36570-900, Brazil.
Laboratório de Infectologia Molecular Animal, Instituto de Biotecnologia Aplicada a Agropecuária (BIOAGRO), Universidade Federal de Viçosa, Av. PH Rolfs, s/n, Viçosa, MG, 36570-900, Brazil.
Virus Genes. 2018 Feb;54(1):77-85. doi: 10.1007/s11262-017-1515-2. Epub 2017 Nov 11.
Infectious bronchitis virus (IBV) is currently one of the most important pathogens in the poultry industry. The H120 and Ma5 are the only viral strains approved by the Brazilian government as the constituent of vaccines. Despite the systematic vaccination in Brazil, IBV has not yet been controlled and diseases associated with this virus have been reported in vaccinated chickens. Here, we investigated the genetic variability of H120 and Ma5 strains present in the IBV vaccines from different Brazilian manufacturers. We performed DNA sequencing analyses of the S1 spike glycoprotein gene to investigate its genetic variability and the presence of viral subpopulations among vaccines, between batches, and also in each vaccine after a single passage was performed in chicken embryonated eggs. Our results revealed up to 13 amino acid substitutions among vaccines and some of them were localized in regions of the S1 glycoprotein that play a role in virus-host interaction. Secondary nucleotide peaks identified in the chromatogram for the S1 gene sequence revealed that all original vaccines (H120 and Ma5) were composed by different subpopulations of IBV. Moreover, new viral subpopulations were also found in vaccines after a single passage in chicken embryonated eggs. These findings indicate that H120 and Ma5 viral strains used in vaccines market in Brazil can still mutate very rapidly during replication, leading to amino acid substitutions in proteins involved in the stimulation of the immune response, such as the S1 glycoprotein. Therefore, our data suggest that the genetic variability of these viral strains should be taken into consideration to ensure an effective immune response against IBV.
传染性支气管炎病毒（IBV）是目前家禽业中最重要的病原体之一。H120和Ma5是巴西政府批准作为疫苗成分的仅有的病毒株。尽管巴西进行了系统的疫苗接种，但IBV尚未得到控制，并且在接种疫苗的鸡中已报告了与该病毒相关的疾病。在此，我们调查了来自不同巴西制造商的IBV疫苗中H120和Ma5毒株的遗传变异性。我们对S1刺突糖蛋白基因进行了DNA测序分析，以研究其遗传变异性以及疫苗之间、批次之间以及在鸡胚中传代一次后的每种疫苗中病毒亚群的存在情况。我们的结果显示，疫苗之间存在多达13个氨基酸替换，其中一些位于S1糖蛋白中在病毒-宿主相互作用中起作用的区域。S1基因序列色谱图中鉴定出的二级核苷酸峰表明，所有原始疫苗（H120和Ma5）均由不同的IBV亚群组成。此外，在鸡胚中传代一次后的疫苗中也发现了新的病毒亚群。这些发现表明，巴西疫苗市场上使用的H120和Ma5病毒株在复制过程中仍可非常迅速地发生突变，导致参与刺激免疫反应的蛋白质（如S1糖蛋白）中的氨基酸替换。因此，我们的数据表明，应考虑这些病毒株的遗传变异性，以确保针对IBV的有效免疫反应。
