Abstract

Background: Bovine orthopneumovirus, formerly known as bovine respiratory syncytial virus (BRSV), is frequently associated with bovine respiratory disease (BRD).

Aim: To perform the molecular characterization of the G and F proteins of Brazilian wild-type BRSV strains derived from bovine respiratory infections in both beef and dairy cattle.

Materials and Methods: Ten BRSV strains derived from a dairy heifer rearing unit (n = 3) in 2011 and steers of three other feedlots (n = 7) in 2014 and 2015 were analyzed. For the BRSV G and F partial gene amplifications, RT-nested-PCR assays were performed with sequencing in both directions with forward and reverse primers used.

Results: The G gene-based analysis revealed that two strains were highly similar to the BRSV sequences representative of subgroup III, including the Bayovac vaccine strain. However, the remaining seven Brazilian BRSV strains were diverse when compared with strains representative of the BRSV I to VIII subgroups. The central hydrophobic region of the Brazilian BRSV G gene showed the replacement of conserved cysteines and other residues of importance to antibody reactivity. The deduced F gene amino acid sequences from the Brazilian BRSV strains showed changes that were absent in the representative sequences of the known subgroups. Viral isolation on the nasopharyngeal swab suspensions failed to isolate BRSV.

Conclusion: Results suggest that these strains represent a putative new subgroup of BRSV with mutations observed in the immunodominant region of the G protein. However, further studies on these Brazilian BRSV strains should be performed to establish their pathogenic potential.

摘要

背景：牛正肺病毒，以前称为牛呼吸道合胞病毒（BRSV），经常与牛呼吸道疾病（BRD）相关。

目的：对来自牛和奶牛的牛呼吸道感染的巴西野生型BRSV菌株的G和F蛋白进行分子表征。

材料和方法：分析 了2011年来自乳牛小母牛饲养单元（n = 3）的10株BRSV菌株，以及 2014和2015年分析了其他三个饲养场（n = 7）的公牛。对于BRSV G和F部分基因扩增，使用两个正向和反向引物在两个方向进行测序，进行RT巢式PCR检测。

结果：基于G基因的分析显示，包括Bayovac疫苗株在内的两个株与代表亚组III的BRSV序列高度相似。但是，与代表BRSV I至VIII亚组的菌株相比，其余7株巴西BRSV菌株是多种多样的。巴西BRSV G基因的中央疏水区显示出保守的半胱氨酸和其他对抗体反应性重要的残基的取代。从巴西BRSV菌株推导的F基因氨基酸序列显示出在已知亚组的代表性序列中不存在的变化。鼻咽拭子悬液的病毒分离未能分离出BRSV。

结论：结果表明，这些菌株代表了一个假定的BRSV新亚组，在G蛋白的免疫优势区域中观察到了突变。但是，应该对这些巴西BRSV菌株进行进一步的研究以确定其致病潜力。