Immune Response to Koi Herpesvirus (KHV) of Koi and Koi × Red Common Carp (Cyprinus carpio).
ABSTRACT: Koi herpesvirus (KHV), also known as Cyprinid herpes virus 3 (Cyprinid 3) is lethal disease in common carp and koi (Cyprinus carpio). Two different groups (KK and RK) were infected KHV by intraperitoneal injection. Fish for gene expression analysis were sampled at 0 h, 12 h, 24 h, 48 h and 72 h post infection (p.i). The results showed that two immune related gene, Interferons (INFs) ?? and Interleukin (IL)-12 p35 induced a high response in RK. The IL-12 p35 cytokine and Toll-like receptor (TLR) 9 were significantly high expressed on 48 h post infection (p.i) in RK as compared to the KK. The histopatological examination reveals focal necrosis in liver and infiltrate of lymphocytes in spleen of KK as compared to the RK. In immunohistochemistry analysis, the KHV protein high expressed in the infected kidney cell and slenocyte of KK. Therefore, the expression of IL-12 p35, IFN ?? and TLR 9 may provide a potentially genes related with KHV resistance in Koi and red common carp × koi.
Project description:Koi herpesvirus (KHV), recently designated Cyprinid herpesvirus 3, is the causative agent of a lethal disease in koi and common carp. In the present study, we investigated the portal of entry of KHV in carp by using bioluminescence imaging. Taking advantage of the recent cloning of the KHV genome as a bacterial artificial chromosome (BAC), we produced a recombinant plasmid encoding a firefly luciferase (LUC) expression cassette inserted in the intergenic region between open reading frame (ORF) 136 and ORF 137. Two viral strains were then reconstituted from the modified plasmid, the FL BAC 136 LUC excised strain and the FL BAC 136 LUC TK revertant strain, including a disrupted and a wild-type thymidine kinase (TK) locus, respectively. In vitro, the two recombinant strains replicated comparably to the parental FL strain. The FL BAC 136 LUC TK revertant strain was shown in vitro to induce a bioluminescent signal allowing the detection of single positive cells as early as 24 h postinfection, while in vivo, it induced KHV infection in carp that was indistinguishable from that induced by the parental FL strain. To identify the KHV portal of entry, carp were analyzed by bioluminescence imaging at different times postinfection with the FL BAC 136 LUC TK revertant strain. These analyses demonstrated that the skin of the fish covering the fins and also the body is the major portal of entry for KHV in carp. Finally, to further demonstrate the role of the skin as the KHV portal of entry, we constructed an original system, nicknamed "U-tube," to perform percutaneous infection restricted to the posterior part of the fish. All the data obtained in the present study demonstrate that the skin, and not the gills, is the major portal of entry for KHV in carp.
Project description:Koi herpesvirus (KHV) (species Cyprinid herpesvirus 3) ORF134 was shown to transcribe a spliced transcript encoding a 179-amino-acid (aa) interleukin-10 (IL-10) homolog (khvIL-10) in koi fin (KF-1) cells. Pairwise sequence alignment indicated that the expressed product shares 25% identity with carp IL-10, 22 to 24% identity with mammalian (including primate) IL-10s, and 19.1% identity with European eel herpesvirus IL-10 (ahvIL-10). In phylogenetic analyses, khvIL-10 fell in a divergent position from all host IL-10 sequences, indicating extensive structural divergence following capture from the host. In KHV-infected fish, khvIL-10 transcripts were observed to be highly expressed during the acute and reactivation phases but to be expressed at very low levels during low-temperature-induced persistence. Similarly, KHV early (helicase [Hel] and DNA polymerase [DNAP]) and late (intercapsomeric triplex protein [ITP] and major capsid protein [MCP]) genes were also expressed at high levels during the acute and reactivation phases, but only low-level expression of the ITP gene was detected during the persistent phase. Injection of khvIL-10 mRNA into zebrafish (Danio rerio) embryos increased the number of lysozyme-positive cells to a similar degree as zebrafish IL-10. Downregulation of the IL-10 receptor long chain (IL-10R1) using a specific morpholino abrogated the response to both khvIL-10 and zebrafish IL-10 transcripts, indicating that, despite the structural divergence, khvIL-10 functions via this receptor. This is the first report describing the characteristics of a functional viral IL-10 gene in the Alloherpesviridae.
Project description:Koi herpesvirus (KHV) has recently been classified as a member of the family of Alloherpesviridae within the order of Herpesvirales. One of the unique features of Herpesviridae is latent infection following a primary infection. However, KHV latency has not been recognized. To determine if latency occurs in clinically normal fish from facilities with a history of KHV infection or exposure, the presence of the KHV genome was investigated in healthy koi by PCR and Southern blotting. KHV DNA, but not infectious virus or mRNAs from lytic infection, was detected in white blood cells from investigated koi. Virus shedding was examined via tissue culture and reverse transcription-PCR (RT-PCR) testing of gill mucus and feces from six koi every other day for 1 month. No infectious virus or KHV DNA was detected in fecal secretion or gill swabs, suggesting that neither acute nor persistent infection was present. To determine if KHV latent infections can be reactivated, six koi were subjected to a temperature stress regime. KHV DNA and infectious virus were detected in both gill and fecal swabs by day 8 following temperature stress. KHV DNA was also detectable in brain, spleen, gills, heart, eye, intestine, kidney, liver, and pancreas in euthanized koi 1 month post-temperature stress. Our study suggests that KHV may become latent in leukocytes and other tissues, that it can be reactivated from latency by temperature stress, and that it may be more widespread in the koi population than previously suspected.
Project description:BACKGROUND:Koi Herpesvirus (KHV) affects both juvenile and adult common carp and koi, and is especially lethal to fry. The high mortalities caused by the disease have had a negative impact on the international koi trade. Different diagnostic techniques have been used to detect KHV, including: isolation of the virus in cell culture, electron microscopy, several PCR tests, ELISA and in situ hybridisation. All of these methods are time consuming, laborious and require specialised equipment. RESULTS:A rapid field diagnosis of KHV in common and koi carp was developed using loop-mediated isothermal amplification (LAMP). The LAMP reaction rapidly amplified nucleic acid with high specificity and efficiency under isothermal conditions using a simple water bath. Two methods of extracting DNA from host tissue were compared: extraction by boiling and by using a commercial extraction kit. A set of six primers--two inner primers, two outer primers and two loop primers--was designed from a KHV amplicon. The reaction conditions were optimised for detection of KHV in 60 min at 65 degrees C using Bst (Bacillus stearothermophilus) DNA polymerase. When visualised by gel electrophoresis, the products of the KHV LAMP assay appeared as a ladder pattern, with many bands of different sizes from 50 base-pairs (bp) up to the loading well. The KHV LAMP product could also be simply detected visually by adding SYBR Green I to the reaction tube and observing a colour change from orange to green. All samples positive for KHV by visual detection were confirmed positive by gel electrophoresis. The KHV LAMP had the same sensitivity as a standard PCR assay for the detection of KHV. CONCLUSION:This paper describes an accelerated LAMP assay for diagnosis of KHV. The entire procedure took only 90 minutes to produce a result: 15 minutes for DNA extraction; 60 min for the LAMP reaction; 2 min for visual detection using SYBR Green I. The test can be used under field conditions because the only equipment it requires is a water bath.
Project description:Koi herpesvirus (KHV) is the causative agent of a lethal disease in koi and common carp. In the present study, we describe the cloning of the KHV genome as a stable and infectious bacterial artificial chromosome (BAC) clone that can be used to produce KHV recombinant strains. This goal was achieved by the insertion of a loxP-flanked BAC cassette into the thymidine kinase (TK) locus. This insertion led to a BAC plasmid that was stably maintained in bacteria and was able to regenerate virions when permissive cells were transfected with the plasmid. Reconstituted virions free of the BAC cassette but carrying a disrupted TK locus (the FL BAC-excised strain) were produced by the transfection of Cre recombinase-expressing cells with the BAC. Similarly, virions with a wild-type revertant TK sequence (the FL BAC revertant strain) were produced by the cotransfection of cells with the BAC and a DNA fragment encoding the wild-type TK sequence. Reconstituted recombinant viruses were compared to the wild-type parental virus in vitro and in vivo. The FL BAC revertant strain and the FL BAC-excised strain replicated comparably to the parental FL strain. The FL BAC revertant strain induced KHV infection in koi carp that was indistinguishable from that induced by the parental strain, while the FL BAC-excised strain exhibited a partially attenuated phenotype. Finally, the usefulness of the KHV BAC for recombination studies was demonstrated by the production of an ORF16-deleted strain by using prokaryotic recombination technology. The availability of the KHV BAC is an important advance that will allow the study of viral genes involved in KHV pathogenesis, as well as the production of attenuated recombinant candidate vaccines.
Project description:Common carp (including ornamental koi carp) Cyprinus carpio L. are ecologically and economically important freshwater fish in Europe and Asia. C. carpio have recently been endangered by a third cyprinid herpesvirus, known as cyprinid herpesvirus-3 (CyHV-3), the etiological agent of koi herpesvirus disease (KHVD), which causes significant morbidity and mortality in koi and common carp. Clinical and pathological signs include epidermal abrasions, excess mucus production, necrosis of gill and internal organs, and lethargy. KHVD has decimated major carp populations in Israel, Indonesia, Taiwan, Japan, Germany, Canada, and the USA, and has been listed as a notifiable disease in Germany since 2005, and by the World Organisation for Animal Health since 2007. KHVD is exacerbated in aquaculture because of the relatively high host stocking density, and CyHV-3 may be concentrated by filter-feeding aquatic organisms. CyHV-3 is taxonomically grouped within the family Alloherpesviridae, can be propagated in a number of cell lines, and is active at a temperature range of 15 to 28°C. Three isolates originating from Japan (KHV-J), USA (KHV-U), and Israel (KHV-I) have been sequenced. CyHV-3 has a 295 kb genome with 156 unique open reading frames and replicates in the cell nucleus, and mature viral particles are 170 to 200 nm in diameter. CyHV-3 can be detected by multiple PCR-based methods and by enzyme-linked immunosorbent assay. Several modes of immunization have been developed for KHVD; however, fish immunized with either vaccine or wild-type virus may become carriers for CyHV-3. There is no current treatment for KHVD.
Project description:Since the mid-1990s, lethal infections of koi herpesvirus (KHV) have been spreading, threatening the worldwide production of common carp and koi (both Cyprinus carpio). The complete genome sequences of three KHV strains from Japan, the United States, and Israel revealed a 295-kbp genome containing a 22-kbp terminal direct repeat. The finding that 15 KHV genes have clear homologs in the distantly related channel catfish virus (ictalurid herpesvirus 1) confirms the proposed place of KHV in the family Herpesviridae, specifically in the branch with fish and amphibian hosts. KHV thus has the largest genome reported to date for this family. The three strains were interpreted as having arisen from a wild-type parent encoding 156 unique protein-coding genes, 8 of which are duplicated in the terminal repeat. In each strain, four to seven genes from among a set of nine are fragmented by frameshifts likely to render the encoded proteins nonfunctional. Six of the affected genes encode predicted membrane glycoproteins. Frameshifts or other mutations close to the 3' ends of coding sequences were identified in a further six genes. The conclusion that at least some of these mutations occurred in vivo prompts the hypothesis that loss of gene functions might be associated with emergence of the disease and provides a basis for further investigations into the molecular epidemiology of the virus.
Project description:BACKGROUND:Infections with carp edema virus, a pox virus, are known from Japanese koi populations since 1974. A characteristic clinical sign associated with this infection is lethargy and therefore the disease is called "koi sleepy disease". Diseased koi also show swollen gills, enophthalmus, and skin lesions. Mortality rates up to 80 % are described. For a long period of time, disease outbreaks seemed to be restricted to Japan. However, during the last years clinical outbreaks of koi sleepy disease also occurred in the UK and in the Netherlands. CASE PRESENTATION:In spring 2014 koi from different ponds showing lethargic behavior, skin ulcers, inflammation of the anus, enophthalmus, and gill necrosis were presented to the laboratory for diagnosis. In all cases, new koi had been purchased earlier that spring from the same retailer and introduced into existing populations. Eleven koi from six ponds were examined for ectoparasites and for bacterial and viral infections (cyprinid herpesviruses in general and especially koi herpesvirus (KHV) known formally as Cyprinid herpesvirus 3 (CyHV-3); and Carp Edema Virus). In most of the cases parasites were not detected from skin and gills. Only opportunistic freshwater bacteria were isolated from skin ulcers. In cell cultures no cytopathic effect was observed, and none of the samples gave positive results in PCR tests for cyprinid herpesviruses. By analyzing gill tissues for CEV in seven out of eleven samples by a nested PCR, PCR products of 547 bp and 180 bp (by using nested primers) could be amplified. An outbreak of Koi Sleepy Disease was confirmed by sequencing of the PCR products. These results confirm the presence of CEV in German koi populations. CONCLUSION:A clinical outbreak of "koi sleepy disease" due to an infection with Carp Edema Virus was confirmed for the first time in Germany. To avoid transmission of CEV to common carp testing of CEV should become part of fish disease surveillance programs.
Project description:One of the unique features of herpesvirus infection is latent infection following an initial exposure, which is characterized by viral genome persistence in a small fraction of cells within the latently infected tissue. Investigation of the mechanisms of herpesvirus latency has been very challenging in tissues with only a small fraction of cells that are latently infected. Cyprinid herpesvirus 3, also known as koi herpesvirus (KHV), is an important and deadly pathogen of koi and common carp, Cyprinus carpio. Acute infection can cause up to 100% mortality in exposed fish, and fish that survive the infection become latently infected. KHV becomes latent in a small percentage of B lymphocytes and can reactivate under stressful conditions. During latency, KHV ORF6 transcript is expressed in the latently infected B lymphocytes. In order to study KHV latent infection in cells that are only latently infected, a nanoflare probe specific to ORF6 RNA was used to separate KHV latently infected cells from total peripheral white blood cells (WBC). Using the ORF6 nanoflare probe, less than 1% of peripheral WBC was isolated from KHV latently infected koi. When this enriched population of WBC was examined by real-time PCR specific for KHV, it was estimated that about 1-2 copies of viral genome persists in the sorted cells. In addition, KHV ORF6 transcript was shown to be the major transcript expressed during latency by RNA-seq analysis. This study demonstrated that an RNA nanoflare probe could be used to enrich latently infected cells, which can subsequently be used to investigate the molecular mechanisms of KHV latency.
Project description:Cyprinid herpesvirus 3 (CyHV-3), also known as koi herpesvirus (KHV), is the aetiological agent of an emerging and lethal disease in common and koi carp. In this work we studied the immune response of two genetically different lines of common carp (Polish K and Polish R3) infected with CyHV-3 by immersion. The two carp lines presented a 20% difference in survival rate and, furthermore, significant difference in virus loads measured at day 3 post infection (p.i.). Microarray analysis revealed that 581 genes in line K (330 up-regulated, 251 down-regulated) and 107 genes in line R3 (77 up-regulated, 30 down-regulated), were at least 2-fold differentially expressed at day 3 p.i. compared to day 0. Genes which were at least 4-fold differentially expressed in both lines were selected as potential markers of an infection of common carp by CyHV-3. This group includes 17 up-regulated and only 1 down-regulated genes. In addition, microarray analysis revealed no significant differences in gene expression between line K and R3 at day 0. At day 3 p.i. there were, however, 76 genes that were at least 2-fold differentially expressed between the two lines. The kinetics of expression of T cell markers and selected cytokines indicate for higher activation of immune response in more resistant R3 line. Thus, our study revealed that differences in resistance to CyHV-3 between two carp lines can be correlated with differentially expressed immune-related genes. Overall design: The experiment included four biological replicates with no dye swaps for (i) each strain (K and R3) and (ii) each condition (day 0 and day 3).