Japan Fisheries Research and Education Agency, Pathology Division, Aquaculture Research Department, Fisheries Technology Institute, Minami-Ise, Mie, Japan.
Okayama University of Science, Department of Veterinary Medicine, Faculty of Veterinary Medicine, Imabari, Ehime, Japan.
PeerJ. 2024 Apr 30;12:e17321. doi: 10.7717/peerj.17321. eCollection 2024.
The Akoya pearl oyster ( (Gould)) is the most important species for pearl cultivation in Japan. Mass mortality of 0-year-old juvenile oysters and anomalies in adults, known as summer atrophy, have been observed in major pearl farming areas during the season when seawater temperatures exceed about 20 °C since 2019. In this study, we identified a novel birnavirus as the pathogen of summer atrophy and named it birnavirus (PiBV). PiBV was first presumed to be the causative agent when it was detected specifically and frequently in the infected oysters in a comparative metatranscriptomics of experimentally infected and healthy pearl oysters. Subsequently, the symptoms of summer atrophy were reproduced by infection tests using purified PiBV. Infection of juvenile oysters with PiBV resulted in an increase in the PiBV genome followed by the atrophy of soft body and subsequent mortality. Immunostaining with a mouse antiserum against a recombinant PiBV protein showed that the virus antigen was localized mainly in the epithelial cells on the outer surface of the mantle. Although the phylogenetic analysis using maximum likelihood method placed PiBV at the root of the genus Entomobirnavirus, the identity of the bi-segmented, genomic RNA to that of known birnaviruses at the full-length amino acid level was low, suggesting that PiBV forms a new genus. The discovery of PiBV will be the basis for research to control this emerging disease.
日本海水珍珠贝（(Gould)）是日本最重要的珍珠养殖物种。自 2019 年以来，在海水温度超过约 20°C 的季节，主要珍珠养殖区观察到 0 龄幼贝大量死亡和成年贝异常（称为夏季萎缩）。在这项研究中，我们鉴定了一种新型双 RNA 病毒作为夏季萎缩的病原体，并将其命名为双 RNA 病毒 (PiBV)。当在实验感染和健康珍珠贝的比较宏转录组学中特异性和频繁地检测到 PiBV 时，最初推测它是病原体。随后，通过使用纯化的 PiBV 进行感染试验再现了夏季萎缩的症状。PiBV 感染幼贝会导致 PiBV 基因组增加，随后软体重度萎缩，最终死亡。用针对重组 PiBV 蛋白的小鼠抗血清进行免疫染色显示，病毒抗原主要定位于外套膜外表面的上皮细胞中。尽管使用最大似然法进行的系统发育分析将 PiBV 置于昆虫双 RNA 病毒属的根部，但全长氨基酸水平的双节、基因组 RNA 与已知双 RNA 病毒的同一性较低，表明 PiBV 形成了一个新属。PiBV 的发现将为控制这种新出现疾病的研究奠定基础。
