PDF(Pubmed)
Abstract：
During their blood-feeding process, ticks are known to transmit various viruses to vertebrates, including humans. Recent viral metagenomic analyses using next-generation sequencing (NGS) have revealed that blood-feeding arthropods like ticks harbor a large diversity of viruses. However, many of these viruses have not been isolated or cultured, and their basic characteristics remain unknown. This study aimed to present the identification of a difficult-to-culture virus in ticks using NGS and to understand its epidemic dynamics using molecular biology techniques. During routine tick-borne virus surveillance in Japan, an unknown flaviviral sequence was detected via virome analysis of host-questing ticks. Similar viral sequences have been detected in the sera of sika deer and wild boars in Japan, and this virus was tentatively named the Saruyama virus (SAYAV). Because SAYAV did not propagate in any cultured cells tested, single-round infectious virus particles (SRIP) were generated based on its structural protein gene sequence utilizing a yellow fever virus-based replicon system to understand its nationwide endemic status. Seroepidemiological studies using SRIP as antigens have demonstrated the presence of neutralizing antibodies against SAYAV in sika deer and wild boar captured at several locations in Japan, suggesting that SAYAV is endemic throughout Japan. Phylogenetic analyses have revealed that SAYAV forms a sister clade with the Orthoflavivirus genus, which includes important mosquito- and tick-borne pathogenic viruses. This shows that SAYAV evolved into a lineage independent of the known orthoflaviviruses. This study demonstrates a unique approach for understanding the epidemiology of uncultured viruses by combining viral metagenomics and pseudoinfectious viral particles.
摘要：
在他们的血液喂养过程中，已知蜱能将各种病毒传播给脊椎动物，包括人类。最近使用下一代测序（NGS）进行的病毒宏基因组分析显示，像蜱这样的以血液为食的节肢动物携带着大量的病毒。然而,其中许多病毒尚未分离或培养，它们的基本特征仍然未知。本研究旨在使用NGS鉴定壁虱中难以培养的病毒，并使用分子生物学技术了解其流行动态。在日本的常规蜱传病毒监测中，通过宿主寻求蜱的病毒学分析检测到未知的黄病毒序列。在日本的梅花鹿和野猪血清中也检测到了类似的病毒序列,该病毒暂定名为Saruyama病毒（SAYAV）。因为SAYAV在任何测试的培养细胞中都没有繁殖，使用基于黄热病毒的复制子系统，基于其结构蛋白基因序列产生了单轮感染性病毒颗粒（SRIP），以了解其全国流行状况。使用SRIP作为抗原的血清流行病学研究表明，在日本多个地点捕获的梅花鹿和野猪中存在针对SAYAV的中和抗体，这表明SAYAV在日本各地都很流行。系统发育分析表明，SAYAV与正黄病毒属形成姐妹进化枝，其中包括重要的蚊子和蜱传播的致病病毒。这表明SAYAV进化成独立于已知的正黄病毒的谱系。这项研究展示了一种独特的方法，通过结合病毒宏基因组学和假感染病毒颗粒来了解未培养病毒的流行病学。
