Niels Lorenzen

Niels Lorenzen
Aarhus University | AU · Department of Animal Science

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138
Publications
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Publications

Publications (138)
Article
Full-text available
The gill of teleost fish is a multifunctional organ involved in many physiological processes, including protection of the mucosal gill surface against pathogens and other environmental antigens by the gill-associated lymphoid tissue (GIALT). Climate change associated phenomena, such as increasing frequency and magnitude of harmful algal blooms (HAB...
Article
Full-text available
The rapidly increasing Mediterranean aquaculture production of European sea bass is compromised by outbreaks of viral nervous necrosis, which can be recurrent and detrimental. In this study, we evaluated the duration of protection and immune response in sea bass given a single dose of a virus-like particle (VLP)-based vaccine. Examinations included...
Article
Full-text available
Viral Nervous Necrosis (VNN) causes high mortality and reduced growth in farmed European sea bass (Dicentrarchus labrax) in the Mediterranean. In the current studies, we tested a novel Pichia-produced virus-like particle (VLP) vaccine against VNN in European sea bass, caused by the betanodavirus "Red-Spotted Grouper Nervous Necrosis Virus" (RGNNV)....
Article
Viral haemorrhagic septicaemia virus (VHSV) is a negative‐sense single‐stranded RNA virus that infects more than 140 different fish species. In this study, zebrafish larvae were employed as in vivo model organisms to investigate progression of disease, the correlation between propagation of the infection and irreversibility of disease, cell tropism...
Article
Mariculture in Denmark is based on production of rainbow trout grown two years in fresh water followed by one growth season in sea cages. Although the majority of rainbow trout are vaccinated against the most serious bacterial pathogens – Aeromonas salmonicida subsp. salmonicida, Vibrio anguillarum and Yersinia ruckeri, by the use of commercially a...
Article
Oral vaccination is of major interest because it can be used for mass vaccination of fish of various size and age. Given that their administration is relatively easy and stress-free, oral vaccines have both economic and animal welfare benefits. Yet, mostly due to their limited efficacy, only very few oral vaccines are available to aquaculture indus...
Article
In fish, DNA vaccines have been shown to give very high protection in experimental facilities against a number of viral diseases, particularly diseases caused by rhabdoviruses. However, their efficacy in generating protection against other families of fish viral pathogens is less clear. One DNA vaccine is currently in use commercially in fish farms...
Article
The highly effective DNA vaccines against diseases caused by fish rhabdoviruses in farmed fish consist of a DNA plasmid vector encoding the viral glycoprotein under the control of a constitutive cytomegalovirus promoter (CMV). Among others, attempts to improve efficacy and safety of these DNA vaccines have focused on regulatory elements of plasmid...
Article
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Four major genotypes of viral haemorrhagic septicaemia virus (VHSV), which have been isolated from many marine and freshwater fish species, are known to differ in virulence. While fast and low-cost genotyping systems based on monoclonal antibodies (MAbs) have been developed for typing of VHSV virulence, there is a need for supplementing the knowled...
Article
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Although spring viremia of carp virus (SVCV) can cause high mortalities in common carp, a commercial vaccine is not available for worldwide use. Here, we report a DNA vaccine based on the expression of the SVCV glycoprotein (G) which, when injected in the muscle even at a single low dose of 0.1 µg DNA/g of fish, confers up to 100% protection agains...
Article
Homologous and heterologous (genogroup Ia) DNA vaccines against viral hemorrhagic septicemia virus (genogroup IVa) conferred partial protection in Pacific Herring Clupea pallasii. Early protection at 2 weeks postvaccination (PV) was low and occurred only at an elevated temperature (12.6°C, 189 degree days), where the relative percent survival follo...
Article
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The high mutation rate of RNA viruses enables the generation of a genetically diverse viral population, termed a quasispecies, within a single infected host. This high in-host genetic diversity enables an RNA virus to adapt to a diverse array of selective pressures such as host immune response and switching between host species. The negative-sense,...
Conference Paper
Microribonucleic acids or microRNAs (miRNAs) are short (18-22 nucleotides) endogenous RNAs that potently regulate the expression of a wide spectrum of genes through the RNA interference mechanism (RNAi). In RNAi, miRNAs repress the translation of target mRNAs or mediate mRNA degradation, and has been implicated in the regulation of almost all cellu...
Article
Furunculosis, a septicaemic infection caused by the bacterium Aeromonas salmonicida subsp. salmonicida, currently causes problems in Danish seawater rainbow trout production. Detection has mainly been achieved by bacterial culture, but more rapid and sensitive methods are needed. A previously developed real-time PCR assay targeting the plasmid enco...
Article
Full-text available
DNA vaccines encoding viral glycoproteins have been very successful for induction of protective immunity against diseases caused by rhabdoviruses in cultured fish species. However, the vaccine concept is based on a single viral gene and since RNA viruses are known to possess high variability and adaptation capacity, this work aimed at evaluating wh...
Article
Full-text available
Ichthyotoxic algal blooms are normally considered a threat to maricultured fish, only when blooms reach lethal cell concentrations. The degree to which sublethal algal concentrations challenge the health of the fish during blooms is practically unknown. In this study, we analyze whether or not sublethal concentrations of the ichthyotoxic alga Prymn...
Article
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Blooms of the marine dictyochophyte Pseudochattonella farcimen have been associated with fish kills, but attempts to verify ichthyotoxicity of this microalga under experimental conditions have not been successful. In the early spring of 2009 and 2011, P. farcimen bloomed in the inner Danish waters. The blooms occurred at a seawater temperature of ∼...
Article
Full-text available
MicroRNAs (miRNAs) are ~22 base pair-long non-coding RNAs which regulate gene expression in the cytoplasm of eukaryotic cells by binding to specific target regions in mRNAs to mediate transcriptional blocking or mRNA cleavage. Through their fundamental roles in cellular pathways, gene regulation mediated by miRNAs has been shown to be involved in a...
Conference Paper
MicroRNAs (miRNAs) are short non coding RNAs which regulate gene expression in eukaryotic cells by binding to specific target regions in mRNAs thereby mediating transcriptional blocking or mRNA cleavage. Various miRNAs have been shown to be involved in many physiological processes including immunological reactions. We here report a strong upregulat...
Article
Mechanisms that account for the high protective efficacy in teleost fish of a DNA vaccine expressing the glycoprotein (G) of Viral hemorrhagic septicemia virus (VHSV) are thought to involve early innate immune responses mediated by interferons (IFNs). Microribonucleic acids (miRNAs) are a diverse class of small (18-22 nucleotides) endogenous RNAs t...
Article
Viral hemorrhagic septicaemia virus (VHSV) is an important viral pathogen in European rainbow trout farming. Isolates from wild marine fish and freshwater trout farms show highly different virulence profiles: isolates from marine fish species cause little or no mortality in rainbow trout following experimental waterborne challenge, whilst challenge...
Article
In fish, intramuscular (i.m) injection of plasmid DNA encoding viral proteins has proved a highly effective vaccination strategy against some viral pathogens. The efficacy of DNA vaccination in teleost fish is based on the high level of viral antigen expression in muscle cells inducing a strong and long-lasting protection. However, the mechanisms t...
Article
Full-text available
Viral haemorrhagic septicaemia virus (VHSV) is an important viral pathogen in European rainbow trout farming. Isolates from wild marine fish and fresh water trout farms show highly different virulence profiles: isolates from marine fish species cause little or no mortality in rainbow trout following experimental waterborne challenge, while challeng...
Article
A cell line, WE-cfin11f, with a fibroblast-like morphology was developed from a walleye caudal fin and used to study the intersection of thermo-biology of walleye, Sander vitreus (Mitchill), with the thermal requirements for replication of viral haemorrhagic septicaemia virus (VHSV) IVb. WE-cfin11f proliferated from 10 to 32 °C and endured as a mon...
Article
Successful viral infection is a complex mechanism, involving many host-pathogen interactions that developed during coevolution of host and pathogen, and often result in host-species specificity. Nevertheless, many viruses are able to infect several host species and sporadically cross species barriers. The viral haemorrhagic septicaemia virus (VHSV)...
Article
Full-text available
Background: Despite vaccination with a commercial vaccine with a documented protective effect against Vibrio anguillarum O1 disease outbreaks caused by this bacterium have been registered among rainbow trout at Danish fish farms. The present study examined specific serum antibody levels as a valid marker for assessing vaccination status in a fish...
Article
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Rainbow trout (Oncorhynchus mykiss) were immunized with plasmid DNA vaccine constructs encoding selected antigens from the parasite Ichthyophthirius multifiliis. Two immobilization antigens (I-ags) and one cysteine protease were tested as genetic vaccine antigen candidates. Antigenicity was evaluated by immunostaining of transfected fish cells usin...
Article
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Seven mAbs with specific reaction patterns against each of the 4 genotypes and 8 subtypes of VHSV were produced, aiming at establishing immunoassay for typing VHSV isolates according to their genotype. Among the mAbs, VHS-1.24 reacted with all genotypes except genotype Ie, while mAb VHS-9.23 reacted with all genotypes except genotype III. MAb VHS-3...
Article
Surveys among wild marine fish have revealed occurrence of viral haemorrhagic septicaemia virus (VHSV) infections in a high number of diverse fish species. In marine aquaculture of rainbow trout, preying on invading wild fish might thus be a risk factor for introduction and adaptation of VHSV and subsequent disease outbreaks. Our objective was to d...
Article
Full-text available
Small interfering RNAs (siRNAs) are promising new active compounds in gene medicine but the induction of non-specific immune responses following their delivery continues to be a serious problem. With the purpose of avoiding such effects chemically modified siRNAs are tested in screening assay but often only examining the expression of specific immu...
Article
Farming of rainbow trout (Oncorhynchus mykiss) in Europe is hampered by unacceptably heavy losses due to the severe infectious disease viral haemorrhagic septicaemia (VHS). Strain-dependent variation of VHS resistance exists. A long-term breeding programme to increase VHS resistance in rainbow trout has been started in Denmark. This programme will...
Article
Full-text available
Cell lines have been established from different fish species especially for virus isolation and for studying cell-pathogen interactions, and therefore are of interest in aquaculture. In this paper, we have investigated the presence and the regulation of some immune genes in the DLEC (Dicentrarchus labrax embryonic cells) cell line from European sea...
Article
Flavobacterium psychrophilum, the causative agent of RTFS or rainbow trout fry syndrome, causes high mortality among hatchery reared rainbow trout (Oncorhynchus mykiss) fry in Europe and the USA. Despite several attempts, no efficient vaccines have yet been developed, the main obstacle being that the fry have to be vaccinated very early, i.e. aroun...
Article
Full-text available
Infectious haematopoietic necrosis virus (IHNV) causes the lethal disease infectious haematopoietic necrosis (IHN) in juvenile salmon and trout. The nucleocapsid (N) protein gene and partial glycoprotein (G) gene (nucleotides 457 to 1061) of the European isolates IT-217A, FR-32/87, DE-DF 13/98 11621, DE-DF 4/99-8/99, AU-9695338 and RU-FR1 were sequ...
Article
Naïve sea bass juveniles (38.4 + or - 4.5 g) were intramuscularly infected with a sublethal dose of betanodavirus isolate 378/I03, followed after 43 days by a similar boosting. This infection resulted in an overall mortality of 7.6%. At various intervals, sampling of fish tissues was performed to investigate: i) B and T lymphocyte content in organs...
Article
Full-text available
Previous studies have indicated that low transfection efficiency can be a major problem when gene inhibition by the use of small interfering RNAs (siRNAs) is attempted in fish cells. This may especially be true when targeting genes of viruses which are fast replicating and which can still infect cells that have not been transfected with the antivir...
Article
DNA vaccines encoding the viral glycoproteins of viral haemorrhagic septicaemia virus (VHSV) and infectious haematopoietic necrosis virus (IHNV) have proved highly efficient in rainbow trout (Oncorhynchus mykiss) under experimental conditions. Non-specific as well as specific immune mechanisms seem to be activated. Temperature is an important exter...
Article
DNA vaccines encoding the glycoprotein genes of the salmonid rhabdoviruses VHSV and IHNV are very efficient in eliciting protective immune responses against their respective diseases in rainbow trout (Oncorhynchus mykiss). The early anti-viral response (EAVR) provides protection by 4 days post vaccination and is non-specific and transient while the...
Article
The effect of viral hemorrhagic septicemia virus (VHSV) was studied on the established rainbow trout (Oncorhynchus mykiss) monocyte/macrophage-like cell line RTS11. The virus was not able to complete its replication cycle as infectious viral particles were not released from the cells. However, in RTS11, the virus was capable of producing mRNA from...
Article
To identify viral proteins that induce cell-mediated cytotoxicity (CMC) against viral hemorrhagic septicemia virus (VHSV)-infected cells, rainbow trout were immunized with DNA vectors encoding the glycoprotein G or the nucleocapsid protein N of VHSV. The G protein was a more potent trigger of cytotoxic cells than the N protein. Peripheral blood leu...
Article
Full-text available
Despite the promise of small interfering RNAs (siRNAs) in antiviral therapy, few in vivostudies of them as inhibitors of viral replication and disease have been published, a lack that is most probably due to problems with obtaining successful delivery. Here we introduce a novel in vivomodel composed of small juvenile rainbow trout and a fish pathog...
Article
Mammalian cytotoxic T cells as part of the adaptive immune system recognize virus-infected target cells by binding of their T-cell receptors (TCR) to classical MHC class I molecules loaded with viral peptides. Our previous studies have shown that the allele of the single dominant polymorphic classical MHC class I locus Onmy-UBA is identical in the...
Article
In the present study using a luciferase/Mx promoter reporter system, it was shown that the rainbow trout gonad cell line (RTG-P1), a fibroblastic cell line, produces IFN when transfected with a plasmid encoding the glycoprotein of VHSV but not with plasmid vector alone. Only a small percentage of the cells expressed the G protein on the surface mem...
Article
RNA interference by small interfering RNAs (siRNAs) is considered to be a highly specific method for knockdown of gene expression in eukaryotic cells via degradation of target mRNA. Mutated siRNA molecules with 1-4 mismatching nucleotides compared to the target mRNA are regularly used as specificity controls. Using siRNAs for inhibition of a fish-p...
Article
Full-text available
The negative stranded RNA virus viral haemorrhagic septicaemia virus (VHSV) is an important disease-causing agent in aquacultured fish and internationally harmonized diagnostic procedures are continuously under development. The present study concerns the suitability of genotyping by sequencing of RT-PCR products for epidemiological analysis. Focus...