Isolation and comprehensive characterization of bovine parvovirus 1 from diarrheic calves in Northeast China: Insights into evolution and biology

Bovine parvovirus (BPV) is among the pathogens associated with respiratory, digestive, and reproductive disorders in cattle, contributing to significant economic losses in the global cattle industry. To investigate the prevalence and genetic variability of BPV in diarrheic cattle, 14 BPV strains were isolated from 673 bovine diarrhea samples (2017–2022, Northeast China) using BT cells. Notably, the DQ7498 strain exhibited the highest proliferation efficiency (titer reaching 108.12TCID50/mL). Sensitive cell detection assays showed isolated strains stably serially passaged only in BT and bovine lung cells. Electron microscopy revealed that all isolates as non-enveloped icosahedrons structures (approximately 25 nm in diameter), consistent with parvovirus morphology. Complete coding sequence (CDS) and phylogenetic analysis revealed that the 14 isolates strains were closely related to BPV1 reference strains (DQ335247, NC001540), with high genetic identity (96.5%-99%). Recombination analysis identified genomic recombination events in four strains (JL108, JL60, DQ7706 and DQ7728), suggesting DQ8186 and ZD0510, or earlier unisolated strains, as potential parental strains. Amino acid sequence analysis revealed multiple coding mutations among the 14 isolates. Although antigenic epitope mutations (A362T and N399D) were identified in VP2, they did not induce significant conformational changes. Physicochemical characterization demonstrated that the virus exhibited sensitivity to chloroform and loses its infectivity after chloroform treatment, which is inconsistent with previous research reports. This study reports the first isolation of 14 BPV1 strains in Northeast China, revealing BPV1 genetic evolution, antigenic variation, and the first documented recombination events among regional strains, providing new insights into the molecular evolution of BPV1 and disease control.

牛细小病毒（BPV）是引发牛呼吸道、消化道及生殖系统疾病的病原之一，给全球养牛业造成了巨额经济损失。为探究腹泻牛群中BPV的流行情况与遗传变异特征，本研究于2017至2022年间在中国东北地区的673份牛腹泻样本中，通过BT细胞（BT cells）分离得到14株BPV。值得注意的是，DQ7498毒株的增殖效率最高，其病毒滴度可达10^8.12 TCID50/mL。敏感细胞检测实验显示，分离得到的毒株仅能在BT细胞与牛肺细胞中稳定连续传代。电子显微镜观察结果显示，所有分离毒株均为无囊膜的二十面体结构，直径约25 nm，符合细小病毒的形态学特征。全编码序列（Complete Coding Sequence, CDS）测序与系统发育分析表明，这14株分离毒株与BPV1参考毒株（DQ335247、NC001540）亲缘关系密切，遗传同源性高达96.5%~99%。重组分析显示，JL108、JL60、DQ7706及DQ7728这4株毒株发生了基因组重组事件，推测DQ8186、ZD0510或更早的未分离毒株为其潜在的亲本毒株。氨基酸序列分析发现，14株分离毒株存在多处编码区突变。尽管在VP2蛋白中发现了A362T与N399D两处抗原表位突变，但并未引发显著的构象变化。理化特性分析结果显示，该病毒对氯仿敏感，经氯仿处理后会丧失感染性，这与既往研究报道的结果并不一致。本研究首次在中国东北地区分离得到14株BPV1毒株，揭示了BPV1的遗传进化与抗原变异特征，同时首次记录了该区域毒株间的重组事件，为BPV1的分子进化研究与疾病防控提供了新的理论依据。