Bovine respiratory syncytial virus (BRSV) is an etiologic agent of bovine respiratory disease. The rapid evolutionary rate of BRSV contributes to genetic and antigenic heterogeneity of field strains and causes occasional vaccine failure. We conducted molecular epidemiologic characterization of BRSV circulating in Japan to obtain genetic information for vaccine-based disease control. Phylogenetic analysis of G and F gene sequences revealed that all of the isolated Japanese BRSV strains clustered in the same genetic subgroup, which was distinct from the 9 known groups. We assigned the Japanese group to subgenotype X. The Japanese isolates formed 2 temporal clusters: isolates from 2003 to 2005 clustered in lineage A; isolates from 2017 to 2019 formed lineage B. The alignment of the deduced amino acid sequences of the G gene revealed that the central hydrophobic region responsible for viral antigenicity is conserved in all of the isolates; unique amino acid mutations were found mainly in mucin-like regions. Our results suggest that BRSV has evolved uniquely in Japan to form the new subgenotype X; the antigenic homogeneity of the viruses within this group is inferred.

牛呼吸道合胞病毒 (BRSV) 是牛呼吸道疾病的病原体。BRSV 的快速进化速度导致了野外菌株的遗传和抗原异质性，并导致偶尔的疫苗失败。我们对日本流行的 BRSV 进行了分子流行病学表征，以获得基于疫苗的疾病控制的遗传信息。G和F的系统发育分析基因序列显示，所有分离的日本 BRSV 菌株都聚集在同一遗传亚组中，这与 9 个已知组不同。我们将日本组分配到亚基因型 X。日本分离株形成了 2 个时间簇：2003 年至 2005 年的分离株聚集在谱系 A 中；从 2017 年到 2019 年的分离株形成了 B 系。G基因推导的氨基酸序列的比对表明，负责病毒抗原性的中央疏水区在所有分离株中都是保守的；独特的氨基酸突变主要在粘蛋白样区域中发现。我们的结果表明 BRSV 在日本独特地进化形成了新的亚基因型 X；推断出该组中病毒的抗原同质性。