Analysis of DNA-Vaccinated Fish Reveals Viral Antigen in Muscle, Kidney and Thymus, and Transient Histopathologic Changes

A highly efficacious DNA vaccine against a fish rhabdovirus, infectious hematopoietic necrosis virus (IHNV), was used in a systematic study to analyze vaccine tissue distribution, persistence, expression patterns, and histopathologic effects. Vaccine plasmid pIHNw-G, containing the gene for the viral glycoprotein, was detected immediately after intramuscular injection in all tissues analyzed, including blood, but at later time points was found primarily in muscle tissue, where it persisted to 90 days. Glycoprotein expression was detected in muscle, kidney, and thymus tissues, with levels peaking at 14 days and becoming undetectable by 28 days. Histologic examination revealed no vaccine-specific pathologic changes at the standard effective dose of 0.1 μg DNA per fish, but at a high dose of 50 μg an increased inflammatory response was evident. Transient damage associated with needle injection was localized in muscle tissue, but by 90 days after vaccination no damage was detected in any tissue, indicating the vaccine to be safe and well tolerated.     

MH-DAB gene polymorphism and disease resistance to Flavobacterium columnare in grass carp (Ctenopharyngodon idellus)

In this study, the association between MH-DAB gene polymorphism and disease resistance was evaluated by challenging grass carp (Ctenopharyngodon idellus) with Flavobacterium columnare. Eight genotypes and six alleles were found, and named by common nomenclature. The genotypes AA, BB, EE, and DE, and the alleles Ctid-DAB1*0101, Ctid-DAB1*0201 and Ctid-DAB1*0401 were more preponderant in fish. The genotype BB was associated with higher resistance to F. columnare, as well as two alleles Ctid-DAB*0101 and Ctid-DAB*0201. Allele Ctid-DAB*0102 has decreased resistance to F. columnare. The expression of MH-DAB gene was decreased in the liver, kidney, and intestine but not in the spleen, gill, and skin at 2 days post infection (dpi), versus to that in the control group. MH-DAB gene expression was up-regulated in most tissues but remained at normal levels in the intestine at 15 days post infection. Our data suggested that MH-DAB polymorphism can be used as a potential genetic marker for disease resistance breeding of grass carp in the future.     

实时定量RT-PCR检测鱼类传染性造血器官坏死病毒方法的建立与应用

建立了Taqman 实时定量RT-PCR方法检测传染性造血器官坏死病毒(IHNV).选取IHNV病毒的N蛋白基因保守序列,利用Primer Express 2.0软件设计引物和探针.以梯度稀释的含有IHNV目的扩增片段的质粒作为标准品,进行定量RT-PCR反应以确定检测灵敏度.病毒浓度在5×106 -5个拷贝,共7个数量级的范围内,定量RT-PCR反应有"S"型扩增曲线,检测灵敏度为5个拷贝.根据病毒拷贝数与定量反应Ct值的关系,绘制了标准曲线.该方法具有特异性,对鲤春血症病毒(SVCV)、病毒性出血性败血症(VHSV)、传染性胰脏坏死病毒(IPNV)、草鱼呼肠孤病毒(GCRV)、流行性造血器官坏死病毒(EHNV)、EPC细胞系、牙鲆的核酸都没有扩增反应.在50批待检样品中,有3批鱼类感染IHNV,利用标准曲线进行了定量分析.实时定量RT-PCR检测IHNV方法,灵敏度高,特异性好,可以进行定量分析,在鱼病的快速检测上具有重要意义.     

一例虹鳟低死亡率疾病的病原学及病理学研究

为确定病原类型和造成虹鳟低死亡率的原因,研究对患病虹鳟进行了病理学观察、病毒的分离和鉴定以及动物感染实验。临床检查发现发病虹鳟体色变黑,肌肉和腹壁点状出血。病理学观察发现虹鳟造血器官脾和肾间组织严重坏死。通过反转录PCR法检测坏死组织和病变细胞中传染性造血器官坏死病毒、出血性败血病毒和传染性胰腺坏死病毒,并对得到的371 bp大小片段进行测序和构建进化树分析,发现感染病原为传染性造血器官坏死病毒。同时,给体重为1.5 kg健康虹鳟腹腔注射104 TCID50的组织滤液,累计死亡率达到35%。除此之外,将组织滤液接种到鲤鱼上皮瘤细胞系后出现了特征性病变。在实验过程中未发现细菌或寄生虫感染。结果证实引起虹鳟低死亡率的病原为传染性造血器官坏死病毒。     

The Antiviral Innate Immune Response in Fish: Evolution and Conservation of the IFN System

Innate immunity constitutes the first line of the host defense after pathogen invasion. Viruses trigger the expression of interferons (IFNs). These master antiviral cytokines induce in turn a large number of interferon-stimulated genes, which possess diverse effector and regulatory functions. The IFN system is conserved in all tetrapods as well as in fishes, but not in tunicates or in the lancelet, suggesting that it originated in early vertebrates. Viral diseases are an important concern of fish aquaculture, which is why fish viruses and antiviral responses have been studied mostly in species of commercial value, such as salmonids. More recently, there has been an interest in the use of more tractable model fish species, notably the zebrafish. Progress in genomics now makes it possible to get a relatively complete image of the genes involved in innate antiviral responses in fish. In this review, by comparing the IFN system between teleosts and mammals, we will focus on its evolution in vertebrates.     

中国本溪虹鳟一株弹状病毒的分离及初步研究

１９９０年４月,辽宁省本溪市虹鳟鱼种场的虹鳟稚鱼爆发大规模疾病,死亡率近１００％。取病鱼组织处理后接种于鱼类细胞,出现明显的细胞病变,测定细胞培养物中的病毒滴度,最高达１０￣（６．３）ＴＣＩＤ＿（５０／０．１ｍｌ）。感染病毒的细胞用１％营养琼脂糖覆盖后可形成０．５－１．５ｍｍ的蚀斑。分离到的病毒对氯仿敏感,不耐热、不耐酸,在细胞内复制的最适温度为１５℃。室内人工感染的虹鳟稚鱼能复制出与天然发病相同的症状。对感染病毒的细胞制成超薄切片,透射电镜观察,病毒长为１３１－１７３ｎｍ,平均１４８ｎｍ,直径为５８－９１ｎｍ,平均７１ｎｍ,形状为子弹状,表明是弹状病毒,有囊膜及纤突。采用挑斑法得到了纯化的病毒株,暂称之为传染性造血器官坏死症病毒中国本溪株ＩＨＮＶ－Ｂ。