Smits S L, Lavazza A, Matiz K, Horzinek M C, Koopmans M P, de Groot R J
Virology Division, Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands.
J Virol. 2003 Sep;77(17):9567-77. doi: 10.1128/jvi.77.17.9567-9577.2003.
Toroviruses (family Coronaviridae, order Nidovirales) are enveloped, positive-stranded RNA viruses that have been implicated in enteric disease in cattle and possibly in humans. Despite their potential veterinary and clinical relevance, little is known about torovirus epidemiology and molecular genetics. Here, we present the first study into the diversity among toroviruses currently present in European swine and cattle herds. Comparative sequence analysis was performed focusing on the genes for the structural proteins S, M, HE, and N, with fecal specimens serving as sources of viral RNA. Sequence data published for animal and human torovirus variants were included. Four genotypes, displaying 30 to 40% divergence, were readily distinguished, exemplified by bovine torovirus (BToV) Breda, porcine torovirus (PToV) Markelo, equine torovirus Berne, and the putative human torovirus. The ungulate toroviruses apparently display host species preference. In phylogenetic analyses, all PToV variants clustered, while the recent European BToVs mostly resembled the New World BToV variant Breda, identified 19 years ago. However, we found ample evidence for recurring intertypic recombination. All newly characterized BToV variants seem to have arisen from a genetic exchange, during which the 3' end of the HE gene, the N gene, and the 3' nontranslated region of a Breda virus-like parent had been swapped for those of PToV. Moreover, some PToV and BToV variants carried chimeric HE genes, which apparently resulted from recombination events involving hitherto unknown toroviruses. From these observations, the existence of two additional torovirus genotypes can be inferred. Toroviruses may be even more promiscuous than their closest relatives, the coronaviruses and arteriviruses.
环曲病毒（冠状病毒科，网巢病毒目）是有包膜的正链RNA病毒，与牛的肠道疾病有关，可能也与人类肠道疾病有关。尽管它们具有潜在的兽医和临床相关性，但关于环曲病毒的流行病学和分子遗传学却知之甚少。在此，我们首次对欧洲猪群和牛群中目前存在的环曲病毒的多样性进行了研究。以粪便标本作为病毒RNA的来源，对结构蛋白S、M、HE和N的基因进行了比较序列分析。还纳入了已发表的动物和人类环曲病毒变体的序列数据。很容易区分出四种基因型，它们之间的差异为30%至40%，以牛环曲病毒（BToV）布雷达株、猪环曲病毒（PToV）马尔克洛株、马环曲病毒伯尔尼株以及假定的人类环曲病毒为代表。有蹄类动物环曲病毒显然表现出宿主物种偏好。在系统发育分析中，所有PToV变体都聚在一起，而最近欧洲的BToV大多与19年前鉴定的新大陆BToV变体布雷达株相似。然而，我们发现了大量反复发生的型间重组的证据。所有新鉴定的BToV变体似乎都源自基因交换，在此过程中，一种类似布雷达病毒的亲本的HE基因的3'端、N基因以及3'非翻译区被PToV的相应部分所取代。此外，一些PToV和BToV变体携带嵌合的HE基因，这显然是由涉及迄今未知环曲病毒的重组事件导致的。从这些观察结果可以推断，还存在另外两种环曲病毒基因型。环曲病毒可能比它们最亲近的亲属冠状病毒和动脉炎病毒更加混杂。
