Gainor Kerry, Stewart Kimberly M, Picknell Angela, Russ Morgan, Makela Noah, Watson Kierra, Mancuso Diana M, Malik Yashpal Singh, Ghosh Souvik
Department of Biomedical Sciences, Ross University School of Veterinary Medicine, Basseterre P.O. Box 334, Saint Kitts and Nevis.
St. Kitts Sea Turtle Monitoring Network, Basseterre P.O. Box 2298, Saint Kitts and Nevis.
Pathogens. 2023 Apr 15;12(4):601. doi: 10.3390/pathogens12040601.
To date, only a handful of viruses have been identified in sea turtles. Although eukaryotic circular Rep (replication initiation protein)-encoding single-stranded DNA (CRESS DNA) viruses have been reported from a wide variety of terrestrial species, and some of these viruses have been associated with clinical conditions in certain animals, limited information is available on CRESS DNA viruses from marine life. The present study aimed to investigate the presence of CRESS DNA viruses in sea turtles. In the present study, two (samples T3 and T33) of the 34 cloacal samples from 31 sea turtles (found in ocean waters around the Caribbean Islands of St. Kitts and Nevis) tested positive for CRESS DNA viruses by a pan- nested PCR assay. The partial Rep sequence of T3 shared 75.78% of a deduced amino acid (aa) identity with that of a CRESS DNA virus (classified under family ) from a mollusk. On the other hand, the complete genome (2428 bp) of T33 was determined by an inverse nested PCR assay. The genomic organization of T33 mirrored those of type II CRESS DNA viral genomes of cycloviruses, characterized by the putative "origin of replication" in the 5'-intergenic region, and the putative Capsid (Cap)- and Rep-encoding open reading frame on the virion-sense- and antisense-strand, respectively. The putative Rep (322 aa) of T33 retained the conserved "HUH endonuclease" and the "super 3 family helicase" domains and shared pairwise aa identities of ~57% with unclassified CRESS DNA viruses from benthic sediment and mollusks. Phylogenetically, the T33 Rep formed a distinct branch within an isolated cluster of unclassified CRESS DNA viruses. The putative Cap (370 aa) of T33 shared maximum pairwise aa identity of 30.51% with an unclassified CRESS DNA virus from a capybara. Except for a blood sample from T33 that tested negative for CRESS DNA viruses, other tissue samples were not available from the sea turtles. Therefore, we could not establish whether the T3 and T33 viral strains infected the sea turtles or were of dietary origin. To our knowledge, this is the first report on the detection of CRESS DNA viruses from sea turtles, adding yet another animal species to the rapidly expanding host range of these viruses. Complete genome analysis of T33 identified a novel, unclassified CRESS DNA virus, providing insights into the high genetic diversity between viruses within the phylum . Considering that sea turtles are an at-risk species, extensive studies on virus discovery, surveillance, and pathogenesis in these marine animals are of the utmost importance.
迄今为止，仅在海龟中鉴定出少数几种病毒。尽管已在多种陆生物种中报道了真核生物环状Rep（复制起始蛋白）编码单链DNA（CRESS DNA）病毒，并且其中一些病毒与某些动物的临床病症有关，但关于海洋生物中CRESS DNA病毒的信息有限。本研究旨在调查海龟中CRESS DNA病毒的存在情况。在本研究中，对来自31只海龟（在圣基茨和尼维斯加勒比群岛周围海域发现）的34份泄殖腔样本中的两份（样本T3和T33）进行了泛巢式PCR检测，结果显示它们对CRESS DNA病毒呈阳性。T3的部分Rep序列与一种来自软体动物的CRESS DNA病毒（归类于 科）的推导氨基酸（aa）序列具有75.78%的同一性。另一方面，通过反向巢式PCR检测确定了T33的完整基因组（2428 bp）。T33的基因组结构与环病毒属II型CRESS DNA病毒基因组相似，其特征在于5'-基因间隔区的假定“复制起点”，以及分别位于病毒链和反义链上的假定衣壳（Cap）和Rep编码开放阅读框。T33的假定Rep（322个氨基酸）保留了保守的“HUH核酸内切酶”和“超3家族解旋酶”结构域，并且与来自底栖沉积物和软体动物的未分类CRESS DNA病毒的氨基酸序列同一性约为57%。在系统发育上，T33的Rep在未分类CRESS DNA病毒的一个孤立簇内形成了一个独特的分支。T33的假定Cap（370个氨基酸）与来自水豚的未分类CRESS DNA病毒的最大氨基酸序列同一性为30.51%除了T33的一份血液样本对CRESS DNA病毒检测呈阴性外，没有从海龟获得其他组织样本。因此，我们无法确定T3和T33病毒株是感染了海龟还是来源于食物。据我们所知，这是关于从海龟中检测到CRESS DNA病毒的首次报告，为这些病毒迅速扩大的宿主范围又增加了一个动物物种。对T33的全基因组分析鉴定出一种新型的、未分类的CRESS DNA病毒，为该门内病毒之间的高遗传多样性提供了见解。鉴于海龟是濒危物种，对这些海洋动物中的病毒发现、监测和发病机制进行广泛研究至关重要。
