Diagnosis of iridovirus in large yellow croaker by PCR

A rapid and sensitive PCR-based method for the detection of the large yellow croaker iridovirus (LYCIV) is described, which involves the amplification of a 295 bp fragment of the LYCIV ATPase gene from DNA isolated from naturally infected fish spleen. Sequencing of LYCIV ATPase gene fragment showed it shared 100% nucleotide sequence homology with the corresponding region of the ATPase gene of red sea bream iridovirus (RSIV) and sea bass iridovirus (SBIV), suggesting that LYCIV was homologous with RSIV and SBIV at least in part of the gemone. The specificity and sensitivity of the PCR procedure were tested on the iridovirus-infected fishes, the expected fragment was detected from spleen DNA samples of infected fishes, whereas no fragments were amplified from healthy fish spleen DNA, white spot syndrome baculoviruses (WSBV) DNA and pseudorabies virus (PRV) DNA. Detection limit of this method was 10(-7) ng positive plasmid DNA containing target sequence, equal to about 100 virions. In the infected experiment, first positive detection (1/4) appeared at Day 3 post-infection, all fish (4/4) tested positive at Day 7, however obvious symptoms were observed at Day 8, so LYCIV infection could be detected prior to the appearance of obvious symptoms. These results indicate that this PCR method could be used for early, rapid and specific detection of LYCIV infection.

Integrated multi-omics analysis reveals liver metabolic reprogramming by fish iridovirus and antiviral function of alpha-linolenic acid

Iridovirus poses a substantial threat to global aquaculture due to its high mortality rate;however,the molecular mechanisms underpinning its pathogenesis are not well elucidated.Here,a multi-omics approach was applied to groupers infected with Singapore grouper iridovirus(SGIV),focusing on the roles of key metabolites.Results showed that SGIV induced obvious histopathological damage and changes in metabolic enzymes within the liver.Furthermore,SGIV significantly reduced the contents of lipid droplets,triglycerides,cholesterol,and lipoproteins.Metabolomic analysis indicated that the altered metabolites were enriched in 19 pathways,with a notable down-regulation of lipid metabolites such as glycerophosphates and alpha-linolenic acid(ALA),consistent with disturbed lipid homeostasis in the liver.Integration of transcriptomic and metabolomic data revealed that the top enriched pathways were related to cell growth and death and nucleotide,carbohydrate,amino acid,and lipid metabolism,supporting the conclusion that SGIV infection induced liver metabolic reprogramming.Further integrative transcriptomic and proteomic analysis indicated that SGIV infection activated crucial molecular events in a phagosome-immune depression-metabolism dysregulation-necrosis signaling cascade.Of note,integrative multi-omics analysis demonstrated the consumption of ALA and linoleic acid(LA)metabolites,and the accumulation of L-glutamic acid(GA),accompanied by alterations in immune,inflammation,and cell death-related genes.Further experimental data showed that ALA,but not GA,suppressed SGIV replication by activating antioxidant and anti-inflammatory responses in the host.Collectively,these findings provide a comprehensive resource for understanding host response dynamics during fish iridovirus infection and highlight the antiviral potential of ALA in the prevention and treatment of iridoviral diseases.

LAMP for the rapid diagnosis of iridovirus in aquaculture

Iridoviruses are DNA virus and have caused huge economic losses in the aquaculture industry.The aim of this study was to establish a colorimetric loop-mediated isothermal amplification(LAMP)protocol for the on-site detection of Singapore grouper iridovirus(SGIV).The SGIV-VP61 gene was chosen as the target gene to develop a colorimetric LAMP assay.The optimized condition of the colorimetric LAMP assay was incubation at 63℃ for 1 h.Samples infected with SGIV could be detected with the color change from yellow into pink.The sensitivity of the developed assay is 5.66 copies/μL of the viral DNA template.This sensitivity was about 1000 times higher than that of conventional PCR while it was slightly lower than the one-step semi-nested PCR assay.A total of 60 DNA samples extracted from the fin tissue of the SGIV-infected Asian seabass were examined for SGIV by colorimetric LAMP,semi-nested PCR and conventional PCR.The results of the colorimetric LAMP assay showed 94.87%agreement with the semi-nested PCR.In addition,the DNA extraction method using NaOH showed a better performance in the colorimetric LAMP assay.Taken together,the colorimetric LAMP established was a sensitive,rapid and specific method for the detection of SGIV.SGIV was not detected in samples randomly taken from a genetically improved line of the Asian seabass.However,some seabass obtained from the local markets were found to contain SGIV.Thus,the LAMP assay has the potential application in the diagnosis of iridovirus diseases in the aquaculture industry.

大黄鱼幼鱼虹彩病毒感染的电镜研究

目的:探索大黄鱼幼鱼夏季高温病流行的病毒性病原体。方法:应用电子显微镜观察大黄鱼幼鱼内脏组织超薄切片。结果:发现大黄鱼幼鱼脾脏细胞肿胀,细胞内存在大量虹彩病毒颗粒。病毒颗粒直径约120nm,呈六角形,有一层蛋白质外壳,核心为核酸。病毒感染主要位于细胞质内。结论:大黄鱼幼鱼脾细胞感染的病毒是虹彩病毒,虹彩病毒感染及环境因素可能是导致大黄鱼幼鱼夏季高温病暴发流行并致死的主要原因。

虹彩病毒和柱状黄杆菌混合感染大鲵的诊治

2012年7月,贵州省某大鲵养殖场发生了以大鲵体表和四肢多处溃烂、内脏器官出现充血、出血为特征的疾病,经过临床症状观察、病理剖检及实验室诊断,诊断为虹彩病毒(Iridovirus)和柱状黄杆菌(Flabobacterium columnare)的混合感染。通过采取综合有效的防治措施,大鲵疫情得到有效控制。

蛙携带虹彩病毒的分子流行病学研究

运用多重实时PCR对多地的养殖和野生蛙类携带虹彩病毒的本底展开调查,并进行病毒分型。结果表明,检测的样品平均阳性率为8.90%,养殖蛙的平均阳性率为4.57%,野生蛙的平均阳性率为16.82%。从蛙种类来看,养殖牛蛙和黑斑蛙带毒率较低,而养殖的棘胸蛙和野外捕捉的斑腿树蛙带毒率较高。不同蛙携带的蛙病毒的分子序列比较结果显示,不同来源的蛙病毒高度保守,缺乏明显的宿主与地域特异性,表明人工繁育场暴发虹彩病毒可能对其他野生蛙类资源产生了负面影响,建议在野生动物人工驯养繁殖体系中引入病害监测和疫病防控措施。

Recognition of abnormal body surface characteristics of oplegnathus punctatus

To identify the abnormal characteristics of the oplegnathus punctatus is great importance to the detection of iridovirus disease in the breeding environment.In this paper,an advanced neural network model to identify the characteristics of the oplegnathus puncta-tus and predict its different periods of suffering from iridovirus disease is proposed based on the establishment of a data set.First of all,a standard format data set of oplegnathus punctatus and an abnormal format date set are established in order to verify the effective-ness of the method in this paper.And then,the feature extraction fusion method is used for preprocessing in terms of the abnormal format data set,which combines the edge fea-tures extracted by the improved multi-template Sobel operator and the color features extracted by the HSV model.Finally,an improved VGG-GoogleNet network recognition model comes into being through the fusion and improvement of the VGG and GoogleNet neural network structure.The experiments results show that the prediction accuracy rate for oplegnathus punctatus suffering from iridovirus disease in the the abnormal format data set and the standard format data set are improved,which reach 98.55%and 69.18%.

甲壳动物虹彩病毒的研究进展

虹彩病毒是一类以无脊椎动物和变温脊椎动物为主要宿主的二十面体、线性双链DNA病毒。部分虹彩病毒可以感染包括虾在内的甲壳动物,且致死率极高,本文将这类病毒统称为甲壳动物虹彩病毒。本文分别从发现历程、系统发育关系、病毒基因组、病毒检测和宿主症状等方面阐述甲壳动物虹彩病毒的研究现状。对甲壳动物虹彩病毒的深入研究将促进对其感染详细分子机制的认识,并为甲壳动物病害防治提供参考。

Virus genomes and virus-host interactions in aquaculture animals

Over the last 30 years,aquaculture has become the fastest growing form of agriculture production in the world,but its development has been hampered by a diverse range of pathogenic viruses.During the last decade,a large number of viruses from aquatic animals have been identified,and more than 100 viral genomes have been sequenced and genetically characterized.These advances are leading to better understanding about antiviral mechanisms and the types of interaction occurring between aquatic viruses and their hosts.Here,based on our research experience of more than 20 years,we review the wealth of genetic and genomic information from studies on a diverse range of aquatic viruses,including iridoviruses,herpesviruses,reoviruses,and rhabdoviruses,and outline some major advances in our understanding of virus–host interactions in animals used in aquaculture.