Instituto Nacional de Tecnología Agropecuaria Balcarce, Departamento de Producción Animal, Laboratorio de Virología, Ruta 226, km 73,5, Balcarce 7620, Argentina.
Vet Microbiol. 2012 Nov 9;160(1-2):1-8. doi: 10.1016/j.vetmic.2012.04.039. Epub 2012 May 17.
Bovine herpesvirus 4 (BoHV-4) is a γ-herpesvirus that has been isolated both from apparently healthy animals and from cattle with a variety of clinical signs, including post-partum endometritis and abortion. BoHV-4 causes either a persistent or a latent infection in cells of the monocyte/macrophage lineage. Two groups of BoVH-4 strains have been defined based on their restriction patterns: the Movar-like strains (European prototype) and the DN 599-like strains (American prototype). The purpose of the present study was to genetically characterize wild type BoHV-4 strains isolated from vaginal discharges of aborted cows in Argentina. The virus was identified by isolation and nested PCR in all vaginal discharge samples from aborted cows, either as a sole agent or in association with other pathogens. Restriction enzyme profiling and phylogenetic analysis demonstrated that there is a high genetic variability among the studied field isolates. The existence of three groups of strains, which were designated as genotypes 1, 2 and 3, is described. Genotypes 1 and 2 possibly correspond to the Movar-like and DN 599-like groups, respectively, whereas Genotype 3 corresponds to a novel group. Two viral strains did not cluster into any of these three groups, indicating that other genotypes could be circulating in Argentina. These results suggest a complex epidemiological background for the Argentinean BoHV-4 strains, probably influenced by independent events of genetic drift. This hypothesis cannot be rejected based on the available data. However, there is no direct evidence supporting this possibility. Thus, it seems speculative to suggest that interspecific jumps are responsible for the observed phylogenetic grouping. On the other hand, our analyses suggest a geographical structure for the observed viral genotypes, since genotypes 1 and 2 included the European (Movar-like) and American (DN599-like) reference strains, respectively. Geographic dispersion is known to be a driver of herpes viruses diversification, and independent evolution in geographical isolated places ensures the emergence of particular mutations in each location due to genetic drift (Compans, 2007; Zong et al., 1999). Therefore, at this point, the genetic drift hypothesis is the one that requires less ad-hoc considerations and thus, to our understanding, is the one that fits to the findings from this study. The involvement of this genetic variability in the detection and pathogenesis of BoHV-4 remains to be investigated.
牛疱疹病毒 4 型（BoHV-4）是一种 γ-疱疹病毒，既能从无明显临床症状的动物中分离出来，也能从表现出多种临床症状的牛中分离出来，包括产后子宫内膜炎和流产。BoHV-4 可在单核细胞/巨噬细胞系的细胞中引起持续性或潜伏性感染。根据其限制模式，已将两组 BoVH-4 株定义为 Movar 样株（欧洲原型）和 DN 599 样株（美国原型）。本研究的目的是对从阿根廷流产牛阴道分泌物中分离出的野生型 BoHV-4 株进行基因特征分析。在所有流产牛的阴道分泌物样本中，通过分离和巢式 PCR 均鉴定到了病毒，病毒是唯一的病原体或与其他病原体共同存在。限制性内切酶图谱分析和系统进化分析表明，研究的田间分离株存在高度的遗传变异。描述了三个株系，分别命名为基因型 1、2 和 3。基因型 1 和 2 可能分别对应 Movar 样株和 DN 599 样株，而基因型 3 则对应一个新的株系。有两个病毒株没有聚类到这三个组中的任何一个，这表明其他基因型可能在阿根廷流行。这些结果表明，阿根廷 BoHV-4 株具有复杂的流行病学背景，可能受到遗传漂变的独立事件的影响。这一假说不能仅基于现有数据来否定。然而，没有直接证据支持这种可能性。因此，将种间跳跃归因于观察到的系统发育分组似乎是推测性的。另一方面，我们的分析表明，观察到的病毒基因型存在地理结构，因为基因型 1 和 2 分别包含欧洲（Movar 样）和美国（DN599 样）参考株。众所周知，地理分散是疱疹病毒多样化的驱动因素，在地理隔离的地方独立进化可以确保在每个地点由于遗传漂变而出现特定的突变（Compans，2007；Zong 等人，1999）。因此，在这一点上，遗传漂变假说需要较少的特别考虑，因此，在我们的理解中，这一假说最符合本研究的发现。BoHV-4 的这种遗传变异性与检测和发病机制的关系仍有待研究。
