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The Infectious Pancreatic Necrosis Virus (IPNV) and its Virulence Determinants: What is Known and What Should be Known. Pathogens 2020; 9:pathogens9020094. [PMID: 32033004 PMCID: PMC7168660 DOI: 10.3390/pathogens9020094] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Revised: 01/25/2020] [Accepted: 01/31/2020] [Indexed: 12/30/2022] Open
Abstract
Infectious pancreatic necrosis (IPN) is a disease of great concern in aquaculture, mainly among salmonid farmers, since losses in salmonid fish—mostly very young rainbow trout (Salmo gairdnery) fry and Atlantic salmon (Salmo salar) post-smolt—frequently reach 80–90% of stocks. The virus causing the typical signs of the IPN disease in salmonids, named infectious pancreatic necrosis virus (IPNV), has also been isolated from other fish species either suffering related diseases (then named IPNV-like virus) or asymptomatic; the general term aquabirnavirus is used to encompass all these viruses. Aquabirnaviruses are non-enveloped, icosahedral bisegmented dsRNA viruses, whose genome codifies five viral proteins, three of which are structural, and one of them is an RNA-dependent RNA polymerase. Due to the great importance of the disease, there have been great efforts to find a way to predict the level of virulence of IPNV isolates. The viral genome and proteins have been the main focus of research. However, to date such a reliable magic marker has not been discovered. This review describes the processes followed for decades in the attempts to discover the viral determinants of virulence, and to help the reader understand how viral components can be involved in virulence modulation in vitro and in vivo. There is also a brief description of the disease, of host defenses, and of the molecular structure and function of the virus and its viral components.
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Dahle MK, Jørgensen JB. Antiviral defense in salmonids - Mission made possible? FISH & SHELLFISH IMMUNOLOGY 2019; 87:421-437. [PMID: 30708056 DOI: 10.1016/j.fsi.2019.01.043] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Revised: 01/24/2019] [Accepted: 01/27/2019] [Indexed: 06/09/2023]
Abstract
Viral diseases represent one of the major threats for salmonid aquaculture. Survival from viral infections are highly dependent on host innate antiviral immune defense, where interferons are of crucial importance. Neutralizing antibodies and T cell effector mechanisms mediate long-term antiviral protection. Despite an immune cell repertoire comparable to higher vertebrates, farmed fish often fail to mount optimal antiviral protection. In the quest to multiply and spread, viruses utilize a variety of strategies to evade or escape the host immune system. Understanding the specific interplay between viruses and host immunity at depth is crucial for developing successful vaccination and treatment strategies in mammals. However, this knowledge base is still limited for pathogenic fish viruses. Here, we have focused on five RNA viruses with major impact on salmonid aquaculture: Salmonid alphavirus, Infectious salmon anemia virus, Infectious pancreatic necrosis virus, Piscine orthoreovirus and Piscine myocarditis virus. This review explore the protective immune responses that salmonids mount to these viruses and the existing knowledge on how the viruses counteract and/or bypass the immune response, including their IFN antagonizing effects and their mechanisms to establish persisting infections.
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Affiliation(s)
- Maria K Dahle
- Norwegian College of Fishery Science, Faculty of Biosciences, Fisheries & Economics, University of Tromsø, The Arctic University of Norway, Norway; Department of Fish Health, Norwegian Veterinary Institute, Oslo, Norway
| | - Jorunn B Jørgensen
- Norwegian College of Fishery Science, Faculty of Biosciences, Fisheries & Economics, University of Tromsø, The Arctic University of Norway, Norway.
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Quantitative Flow Cytometry to Measure Viral Production Using Infectious Pancreatic Necrosis Virus as a Model: A Preliminary Study. APPLIED SCIENCES-BASEL 2018. [DOI: 10.3390/app8101734] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
In recent decades, flow cytometry (FCM) has become an important tool in virology, due to its applications in viral replication and viral-cell interactions, as well as its capacity to quantify proteins (qFCM). In the present study, we have designed and evaluated a qFCM procedure for the in vitro analysis and quantification of fish viral proteins, using the infectious pancreatic necrosis virus (IPNV) as a model. We have also tested its use for viral titration and adapted the MARIS (method for analysing RNA following intracellular sorting) method for simultaneous quantification of viral RNA expression in infected cells. The procedure has proved to be repeatable and reproducible to an acceptable level, although to ensure reproducibility, the repetition of standard curves is inevitable. Regarding its use for viral quantification, a direct relationship (by a second-degree polynomial regression) between viral titres and Molecules of Equivalent Soluble Fluorochrome (MESF) was observed. Finally, the results support the use of this technology, not only for virus quantification, but also to study viral replication from a quantitative approach.
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Collet B, Collins C, Lester K. Engineered cell lines for fish health research. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2018; 80:34-40. [PMID: 28108246 DOI: 10.1016/j.dci.2017.01.013] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 01/13/2017] [Accepted: 01/16/2017] [Indexed: 06/06/2023]
Abstract
As fish farming continues to increase worldwide, the related research areas of fish disease and immunology are also expanding, aided by the revolution in access to genomic information and molecular technology. The genomes of most fish species of economic importance are now available and annotation based on sequence homology with characterised genomes is underway. However, while useful, functional homology is more difficult to determine, there being a lack of widely distributed and well characterised reagents such as monoclonal antibodies, traditionally used in mammalian studies, to help with confirming functions and cellular interactions of fish molecules. In this context, fish cell lines and the possibility of their genetic engineering offer good prospects for studying functional genomics with respect to fish diseases. In this review, we will give an overview of available permanently genetically engineered fish cell lines, as cell-based reporter systems or platforms for expression of endogenous immune or pathogen genes, to investigate interactions and function. The advantages of such systems and the technical challenge for their development will be discussed.
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Bols NC, Pham PH, Dayeh VR, Lee LEJ. Invitromatics, invitrome, and invitroomics: introduction of three new terms for in vitro biology and illustration of their use with the cell lines from rainbow trout. In Vitro Cell Dev Biol Anim 2017; 53:383-405. [DOI: 10.1007/s11626-017-0142-5] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 02/14/2017] [Indexed: 12/25/2022]
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Parreño R, Torres S, Almagro L, Belló-Pérez M, Estepa A, Perez L. Induction of viral interference by IPNV-carrier cells on target cells: A cell co-culture study. FISH & SHELLFISH IMMUNOLOGY 2016; 58:483-489. [PMID: 27693199 DOI: 10.1016/j.fsi.2016.09.052] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Revised: 09/20/2016] [Accepted: 09/26/2016] [Indexed: 06/06/2023]
Abstract
IPNV is a salmonid birnavirus that possesses the ability to establish asymptomatic persistent infections in a number of valuable fish species. The presence of IPNV may interfere with subsequent infection by other viruses. In the present study we show that an IPNV-carrier cell line (EPCIPNV) can induce an antiviral state in fresh EPC by co-cultivating both cell types in three different ways: a "droplet" culture system, a plastic chamber setup, and a transmembrane (Transwell®) system. All three cell co-culture methods were proven useful to study donor/target cell interaction. Naïve EPC cells grown in contact with EPCIPNV cells develop resistance to VHSV superinfection. The transmembrane system seems best suited to examine gene expression in donor and target cells separately. Our findings point to the conclusion that one or more soluble factors produced by the IPNV carrier culture induce the innate immune response within the target cells. This antiviral response is associated to the up-regulation of interferon (ifn) and mx gene expression in target EPC cells. To our knowledge this is the first article describing co-culture systems to study the interplay between virus-carrier cells and naive cells in fish.
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Affiliation(s)
- Ricardo Parreño
- Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, Av. Universidad s/n, 03202 Elche, Spain
| | - Susana Torres
- Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, Av. Universidad s/n, 03202 Elche, Spain
| | - Lucía Almagro
- Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, Av. Universidad s/n, 03202 Elche, Spain
| | - Melissa Belló-Pérez
- Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, Av. Universidad s/n, 03202 Elche, Spain
| | - Amparo Estepa
- Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, Av. Universidad s/n, 03202 Elche, Spain
| | - Luis Perez
- Instituto de Biología Molecular y Celular, Universidad Miguel Hernández, Av. Universidad s/n, 03202 Elche, Spain.
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Julin K, Johansen LH, Sommer AI, Jørgensen JB. Persistent infections with infectious pancreatic necrosis virus (IPNV) of different virulence in Atlantic salmon, Salmo salar L. JOURNAL OF FISH DISEASES 2015; 38:1005-1019. [PMID: 25557127 DOI: 10.1111/jfd.12317] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2014] [Revised: 09/02/2014] [Accepted: 09/03/2014] [Indexed: 06/04/2023]
Abstract
Infectious pancreatic necrosis virus (IPNV) is a prevalent pathogen in fish worldwide. The virus causes substantial mortality in Atlantic salmon juveniles and smolts when transferred to sea water and persistent infection in surviving fish after disease outbreaks. Here, we have investigated the occurrence of the virus as well as the innate immune marker Mx in the head kidney (HK) of Atlantic salmon throughout an experimental challenge covering both a fresh and a seawater phase. The fish were challenged with a high (HV) and low virulence (LV) IPNV. Both isolates caused mortality due to reactivation of the virus after transfer to sea water. In the freshwater phase, higher levels of virus transcripts were detected in the HK of fish infected with LV IPNV compared to HV, suggesting that the HV isolate is able to limit its own replication to a level where the innate immune system is not alerted. Further, ex vivoHK leucocytes derived from fish infected with the two isolates were stimulated with CpG DNA. Significantly, higher IFN levels were found in the LV compared to the HV group in the freshwater phase. This suggests that the viruses attenuate the antiviral host immune response at different levels which may contribute to the observed differences in disease outcome.
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Affiliation(s)
| | | | | | - J B Jørgensen
- Norwegian College of Fisheries Science, UiT The Arctic University of Norway, Tromsø, Norway
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Ballesteros NA, Rodriguez Saint-Jean S, Perez-Prieto SI. Immune responses to oral pcDNA-VP2 vaccine in relation to infectious pancreatic necrosis virus carrier state in rainbow trout Oncorhynchus mykiss. Vet Immunol Immunopathol 2015; 165:127-37. [PMID: 25892368 DOI: 10.1016/j.vetimm.2015.04.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Revised: 03/10/2015] [Accepted: 04/01/2015] [Indexed: 10/23/2022]
Abstract
The VP2 gene of infectious pancreatic necrosis virus, encoded in an expression plasmid and encapsulated in alginate microspheres, was used for oral DNA vaccination of fish to better understand the carrier state and the action of the vaccine. The efficacy of the vaccine was evaluated by measuring the prevention of virus persistence in the vaccinated fish that survived after waterborne virus challenge. A real-time RT-qPCR analysis revealed lower levels of IPNV-VP4 transcripts in rainbow trout survivors among vaccinated and challenged fish compared with the control virus group at 45 days post-infection. The infective virus was recovered from asymptomatic virus control fish, but not from the vaccinated survivor fish, suggesting an active role of the vaccine in the control of IPNV infection. Moreover, the levels of IPNV and immune-related gene expression were quantified in fish showing clinical infection as well as in asymptomatic rainbow trout survivors. The vaccine mimicked the action of the virus, although stronger expression of immune-related genes, except for IFN-1 and IL12, was detected in survivors from the virus control (carrier) group than in those from the vaccinated group. The transcriptional levels of the examined genes also showed significant differences in the virus control fish at 10 and 45 days post-challenge.
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Affiliation(s)
- Natalia A Ballesteros
- Centro de Investigaciones Biologicas (CSIC), Dpto Microbiologia Molecular y Biología de las Infecciones, C/ Ramiro de Maeztu 9, 28040 Madrid, Spain.
| | - Sylvia Rodriguez Saint-Jean
- Centro de Investigaciones Biologicas (CSIC), Dpto Microbiologia Molecular y Biología de las Infecciones, C/ Ramiro de Maeztu 9, 28040 Madrid, Spain.
| | - Sara I Perez-Prieto
- Centro de Investigaciones Biologicas (CSIC), Dpto Microbiologia Molecular y Biología de las Infecciones, C/ Ramiro de Maeztu 9, 28040 Madrid, Spain.
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Rodriguez Saint-Jean S, González C, Monrás M, Romero A, Ballesteros N, Enríquez R, Perez-Prieto S. Establishment and characterization of a new cell line (SSP-9) derived from Atlantic salmon Salmo salar that expresses type I ifn. JOURNAL OF FISH BIOLOGY 2014; 85:1526-1545. [PMID: 25230295 DOI: 10.1111/jfb.12503] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Accepted: 07/11/2014] [Indexed: 06/03/2023]
Abstract
In the present work, the establishment and biological characterization of a new cell line, SSP-9, derived from the pronephros of the Atlantic salmon Salmo salar, are reported. These cells grew well in Leibovitz's (L15) medium supplemented with 10% foetal calf serum at temperatures from 15 to 25° C, and they have been sub-cultured over 100 passages to produce a continuous cell line with an epithelial-like morphology. The SSP-9 cells attached and spread efficiently at different plating densities, retaining 80% of cell viability after storage in liquid nitrogen. When karyotyped, the cells had 40-52 chromosomes, with a modal number of 48. Viral susceptibility tests showed that SSP-9 cells were susceptible to infectious pancreatic necrosis virus and infectious haematopoietic necrosis virus, producing infectious virus and regular cytopathic effects. Moreover, these cells could be stimulated by poly I:C, showing significant up-regulation in the expression of the genes that regulate immune responses, such as ifn and mx-1. SSP-9 cells constitutively express genes characteristic of macrophages, such as major histocompatibility complex (mhc-II) and interleukin 12b (il-12b), and flow cytometry assays confirmed that SSP-9 cells can be permanently transfected with plasmids expressing a reporter gene. Accordingly, this new cell line is apparently suitable for transgenic manipulation, and to study host cell-virus interactions and immune processes.
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Ballesteros NA, Rodríguez Saint-Jean S, Pérez-Prieto SI, Aquilino C, Tafalla C. Modulation of genes related to the recruitment of immune cells in the digestive tract of trout experimentally infected with infectious pancreatic necrosis virus (IPNV) or orally vaccinated. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2014; 44:195-205. [PMID: 24370535 DOI: 10.1016/j.dci.2013.12.009] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2013] [Revised: 12/16/2013] [Accepted: 12/17/2013] [Indexed: 05/13/2023]
Abstract
There are still many details of how intestinal immunity is regulated that remain unsolved in teleost. Although leukocytes are present all along the digestive tract, most immunological studies have focused on the posterior segments and the importance of each gut segment in terms of immunity has barely been addressed. In the current work, we have studied the regulation of several immune genes along five segments of the rainbow trout (Oncorhynchus mykiss) digestive tract, comparing the effects observed in response to an infectious pancreatic necrosis virus (IPNV) infection to those elicited by oral vaccination with a plasmid coding for viral VP2. We have focused on the regulation of several mucosal chemokines, chemokine receptors, the major histocompatibility complex II (MHC-II) and tumor necrosis factor α (TNF-α). Furthermore, the recruitment of IgM(+) cells and CD3(+) cells was evaluated along the different segments in response to IPNV by immunohistochemical techniques. Our results provide evidences that there is a differential regulation of these immune genes in response to both stimuli along the gut segments. Along with this chemokine and chemokine receptor induction, IPNV provoked a mobilization of IgM(+) and IgT(+) cells to the foregut and pyloric caeca region, and CD3(+) cells to the pyloric caeca and midgut/hindgut regions. Our results will contribute to a better understanding of how mucosal immunity is orchestrated in the different gut segments of teleost.
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Affiliation(s)
- Natalia A Ballesteros
- Centro de Investigaciones Biológicas, (CSIC), Dpto. Microbiología Molecular y Biología de la Infección, 28040 Madrid, Spain
| | - Sylvia Rodríguez Saint-Jean
- Centro de Investigaciones Biológicas, (CSIC), Dpto. Microbiología Molecular y Biología de la Infección, 28040 Madrid, Spain
| | - Sara I Pérez-Prieto
- Centro de Investigaciones Biológicas, (CSIC), Dpto. Microbiología Molecular y Biología de la Infección, 28040 Madrid, Spain
| | - Carolina Aquilino
- Centro de Investigación en Sanidad Animal (CISA-INIA), Valdeolmos, Madrid, Spain
| | - Carolina Tafalla
- Centro de Investigación en Sanidad Animal (CISA-INIA), Valdeolmos, Madrid, Spain.
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Ballesteros NA, Rodriguez Saint-Jean S, Perez-Prieto SI. Food pellets as an effective delivery method for a DNA vaccine against infectious pancreatic necrosis virus in rainbow trout (Oncorhynchus mykiss, Walbaum). FISH & SHELLFISH IMMUNOLOGY 2014; 37:220-228. [PMID: 24561129 DOI: 10.1016/j.fsi.2014.02.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Revised: 02/07/2014] [Accepted: 02/09/2014] [Indexed: 06/03/2023]
Abstract
A DNA vaccine based on the VP2 gene of infectious pancreatic necrosis virus (IPNV) was incorporated into feed to evaluate the effectiveness of this oral delivery method in rainbow trout. Lyophilized alginate-plasmid complexes were added to feed dissolved in water and the mixture was then lyophilized again. We compared rainbow trout that were fed for 3 consecutive days with vaccine pellets with fish that received the empty plasmid or a commercial pellet. VP2 gene expression could be detected in tissues of different organs in the rainbow trout that received the pcDNA-VP2 coated feed (kidney, spleen, gut and gill) throughout the 15 day time-course of the experiments. This pcDNA-VP2 vaccine clearly induced an innate and specific immune-response, significantly up-regulating IFN-1, IFN-γ, Mx-1, IL8, IL12, IgM and IgT expression. Strong protection, with relative survival rates of 78%-85.9% were recorded in the vaccinated trout, which produced detectable levels of anti-IPNV neutralizing antibodies during 90 days at least. Indeed, IPNV replication was significantly down-regulated in the vaccinated fish 45 days pi.
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Affiliation(s)
- Natalia A Ballesteros
- Dept. Microbiología Molecular y Biología de las infecciones, Centro de Investigaciones Biológicas (CSIC), C/Ramiro de Maeztu 9, 28040 Madrid, Spain
| | - Sylvia Rodriguez Saint-Jean
- Dept. Microbiología Molecular y Biología de las infecciones, Centro de Investigaciones Biológicas (CSIC), C/Ramiro de Maeztu 9, 28040 Madrid, Spain
| | - Sara I Perez-Prieto
- Dept. Microbiología Molecular y Biología de las infecciones, Centro de Investigaciones Biológicas (CSIC), C/Ramiro de Maeztu 9, 28040 Madrid, Spain.
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Collet B. Innate immune responses of salmonid fish to viral infections. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2014; 43:160-73. [PMID: 23981327 DOI: 10.1016/j.dci.2013.08.017] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Revised: 08/19/2013] [Accepted: 08/19/2013] [Indexed: 05/07/2023]
Abstract
Viruses are the most serious pathogenic threat to the production of the main aquacultured salmonid species the rainbow trout Oncorhynchus mykiss and the Atlantic salmon Salmo salar. The viral diseases Infectious Pancreatic Necrosis (IPN), Pancreatic Disease (PD), Infectious Haemorrhagic Necrosis (IHN), Viral Haemorrhagic Septicaemia (VHS), and Infectious Salmon Anaemia (ISA) cause massive economic losses to the global salmonid aquaculture industry every year. To date, no solution exists to treat livestock affected by a viral disease and only a small number of efficient vaccines are available to prevent infection. As a consequence, understanding the host immune response against viruses in these fish species is critical to develop prophylactic and preventive control measures. The innate immune response represents an important part of the host defence mechanism preventing viral replication after infection. It is a fast acting response designed to inhibit virus propagation immediately within the host, allowing for the adaptive specific immunity to develop. It has cellular and humoral components which act in synergy. This review will cover inflammation responses, the cell types involved, apoptosis, antimicrobial peptides. Particular attention will be given to the type I interferon system as the major player in the innate antiviral defence mechanism of salmonids. Viral evasion strategies will also be discussed.
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Antiviral activity produced by an IPNV-carrier EPC cell culture confers resistance to VHSV infection. Vet Microbiol 2013; 166:412-8. [DOI: 10.1016/j.vetmic.2013.06.022] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Revised: 06/24/2013] [Accepted: 06/25/2013] [Indexed: 11/18/2022]
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Julin K, Mennen S, Sommer AI. Study of virulence in field isolates of infectious pancreatic necrosis virus obtained from the northern part of Norway. JOURNAL OF FISH DISEASES 2013; 36:89-102. [PMID: 22966863 DOI: 10.1111/j.1365-2761.2012.01423.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2012] [Revised: 05/21/2012] [Accepted: 06/27/2012] [Indexed: 06/01/2023]
Abstract
In order to study the variety of infectious pancreatic necrosis virus (IPNV) strains involved in outbreaks of infectious pancreatic necrosis (IPN) in Atlantic salmon fish farms, samples were collected from 19 different outbreaks of IPN in the northern part of Norway. The main objective of this study was to examine whether IPNV isolates of different virulence were involved in the outbreaks and could explain the variable IPN protection observed in vaccinated post-smolts in the field. Both the molecular basis of virulence of all field isolates and virulence expressed by mortality after bath challenge of unvaccinated post-smolts with eight of the isolates were studied. Very little variation among the field isolates was detected when the 578-bp variable region encoding the VP2 protein known to be involved in virulence was sequenced. The cumulative mortality after experimental challenge with field isolates genetically characterized as highly virulent was always high (40-56%), while the cumulative mortality of the same strains in vaccinated post-smolts during the field outbreaks varied from 1 to 50%. Although the tested samples came from fish vaccinated with the same vaccine product, the protection against IPN varied. These results demonstrate that differences in virulence of the isolates were not the main reason for the variation in mortality in the field outbreaks. Most of the field isolates were of high virulence, which is shown in experimental challenges to be important for mortality, but clearly other factors that might affect the susceptibility of IPN also play an important role in the outcome of an IPNV infection.
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Rønneseth A, Pettersen EF, Wergeland HI. Flow cytometry assay for intracellular detection of Infectious Pancreatic Necrosis virus (IPNV) in Atlantic salmon (Salmo salar L.) leucocytes. FISH & SHELLFISH IMMUNOLOGY 2012; 33:1292-1302. [PMID: 23032441 DOI: 10.1016/j.fsi.2012.09.020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Revised: 09/20/2012] [Accepted: 09/20/2012] [Indexed: 06/01/2023]
Abstract
Infectious Pancreatic Necrosis virus (IPNV) is traditionally detected in adherent leucocytes using immunofluorescence labelled specific antibodies, PCR or by further cultivation of infected cell material in cell lines. We present a flow cytometry (FCM) assay for detection of intracellular IPNV in salmon leucocytes, where each single cell is analysed for presence of virus. The method is established using in vitro challenge of salmon leucocytes and CHSE-214 cells. For detection of intracellular virus antigen the Cytofix/Cytoperm kit from BD is optimal compared with paraformaldehyde or acetone/methanol for cell permeabilisation. This is combined with labelling procedures allowing both internal virus antigen labelling and external antibody labelling of cell markers to identify B-cells and neutrophils. The secondary antibodies were Alexa Fluor 647 for the internal labelling and RPE for the external labelling of bound cell subtype specific antibodies. The presences of virus within cells are also demonstrated by confocal and light microscopy of infected cells. IPNV is successfully detected in blood and head kidney leucocyte samples. IPNV is found both in B-cells and neutrophils as well as in other types of leucocytes that could not be identified due to lack of cell-specific antibodies. Serial samples from cultivation of in vitro infected leucocytes and CHSE-214 cells analysed by flow cytometry showed that number of infected cells increased with increasing number of days. The flow cytometry protocol for detection of intracellular IPNV is verified using CHSE-214 cells persistently infected with IPNV. These analyses are compared with virus titre and virus infected naive CHSE-214 cells. The detection of IPNV in persistently infected cells indicates that carrier fish can be analysed, as such cells are considered to have virus titres similar to carriers.
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Affiliation(s)
- Anita Rønneseth
- Department of Biology, University of Bergen, Bergen High-Technology Center, PO Box 7803, NO-5020 Bergen, Norway.
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Adamek M, Rakus KŁ, Chyb J, Brogden G, Huebner A, Irnazarow I, Steinhagen D. Interferon type I responses to virus infections in carp cells: In vitro studies on Cyprinid herpesvirus 3 and Rhabdovirus carpio infections. FISH & SHELLFISH IMMUNOLOGY 2012; 33:482-493. [PMID: 22683518 DOI: 10.1016/j.fsi.2012.05.031] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Revised: 05/06/2012] [Accepted: 05/29/2012] [Indexed: 06/01/2023]
Abstract
Interferons (IFNs) are secreted mediators that play a fundamental role in the innate immune response against viruses among all vertebrate classes. Common carp is a host for two highly contagious viruses: spring viraemia of carp virus (Rhabdovirus carpio, SVCV) and the Cyprinid herpesvirus 3 (CyHV-3), which belong to Rhabdoviridae and Alloherpesviridae families, respectively. Both viruses are responsible for significant losses in carp aquaculture. In this paper we studied the mRNA expression profiles of genes encoding for proteins promoting various functions during the interferon pathway, from pattern recognition receptors to antiviral genes, during in vitro viral infection. Furthermore, we investigated the impact of the interferon pathway (stimulated with poly I:C) on CyHV-3 replication and the speed of virus spreading in cell culture. The results showed that two carp viruses, CyHV-3 and SVCV induced fundamentally different type I IFN responses in CCB cells. SVCV induced a high response in all studied genes, whereas CyHV-3 seems to induce no response in CCB cells, but it induces a response in head kidney leukocytes. The lack of an IFN type I response to CyHV-3 could be an indicator of anti-IFN actions of the virus, however the nature of this mechanism has to be evaluated in future studies. Our results also suggest that an activation of type I IFN in CyHV-3 infected cells can limit the spread of the virus in cell culture. This would open the opportunity to treat the disease associated with CyHV-3 by an application of poly I:C in certain cases.
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Affiliation(s)
- Mikołaj Adamek
- Fish Disease Research Unit, Centre of Infectious Diseases, University of Veterinary Medicine Hannover, Bünteweg 17, D-30559 Hannover, Germany.
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Characterization of an infectious pancreatic necrosis (IPN) virus carrier cell culture with resistance to superinfection with heterologous viruses. Vet Microbiol 2011; 149:48-55. [DOI: 10.1016/j.vetmic.2010.10.017] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2010] [Revised: 07/19/2010] [Accepted: 10/20/2010] [Indexed: 01/02/2023]
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