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ABSTRACT: The Toggenburg orbivirus (TOV), a recently discovered virus related to bluetongue virus (BTV), has been identified in goats in Switzerland, Italy and Germany. Isolation of TOV in vitro has not yet been achieved and the transmission mechanisms are still unknown. In the experimental infection of pregnant goats described here, TOV could not be detected in secretion/excretion samples or fetal blood. Material from the goat experiment was used as inoculum for propagating the virus in vitro. To enhance the infectivity of TOV several modified protocols, e.g. pretreatment of the virus with trypsin, polyethylene glycol-mediated infection and lipofection were applied. Isolation of TOV, attempts to infect Culicoides nubeculosus by feeding TOV-positive blood and intracerebral inoculation of newborn mice were unsuccessful. The results of these studies suggest that TOV requires specific but different factors than other BTVs for infection and replication outside of its natural caprine host.
Research in Veterinary Science 03/2011; 91(3):e163-8. · 1.65 Impact Factor
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ABSTRACT: After the spread of H5N1 highly pathogenic avian influenza virus (AIV) from Asia into Russia, the Middle East, Europe, and Africa in 2005-06, the Swiss national AIV surveillance program was extended. One of the new focal points was Lake Constance, where sentinel duck stations and swim-in traps were established within the project Constanze in collaboration with Germany and Austria. More than 2000 samples from 41 species were collected in Switzerland between September 2006 and December 2008. Approximately 4% were AIV-positive by quantitative reverse transcriptase-PCR. Subsequent typing revealed 13 different AIV subtypes, of which H5N2 and H9N2 were the most prevalent. All H7 isolates and all but one H5 isolate were characterized as low pathogenic; however, a highly pathogenic H5N1 AIV was detected in a healthy pochard. This study demonstrates that a wide selection of different AIV subtypes can cocirculate among the waterfowl population in wild bird habitats.
Avian Diseases 06/2010; 54(2):875-84. · 1.46 Impact Factor
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ABSTRACT: Toggenburg Orbivirus (TOV) has been detected recently in healthy goats in Switzerland. The virus is related closely to bluetongue virus (BTV) and is considered tentatively as a 25th serotype of BTV. Upon detection of additional TOV-positive goats in Switzerland, Germany, and Italy, these TOV isolates were characterized genetically by partial sequencing of the viral genome segment 2 which encodes VP2, the major outer capsid protein of orbiviruses. A TOV-specific RT-qPCR was developed, targeting conserved areas within segment 2. Since TOV cannot be propagated up to now outside its natural host, a synthetic positive control for the RT-qPCR was constructed by cloning the entire coding region of segment 2 and subsequent in vitro transcription of RNA from both ends to obtain double-stranded RNA. The TOV-specific RT-qPCR was able to detect as few as 30 dsRNA copies and proved to be equally sensitive as a pan BTV assay that was shown previously to have a detection limit of 0.001 TCID(50).
Journal of virological methods 02/2010; 165(2):325-9. · 2.13 Impact Factor
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ABSTRACT: Since the advent of highly pathogenic variants of avian influenza virus (HPAIV), the main focus of avian influenza research has been the characterization and detection of HPAIV hemagglutinin (HA) from H5 and H7 subtypes. However, due to the high mutation and reassortation rate of influenza viruses, in theory any influenza strain may acquire increased pathogenicity irrespective of its subtype. A comprehensive antigenic characterization of influenza viruses encompassing all 16 HA and 9 neuraminidase subtypes will provide information useful for the design of differential diagnostic tools, and possibly, vaccines. We have expressed recombinant HA proteins from 3 different influenza virus HA subtypes in the baculovirus system. These proteins were used to generate polyclonal rabbit antisera, which were subsequently employed in epitope scanning analysis using peptide libraries spanning the entire HA. Here, we report the identification and characterization of linear, HA subtype-specific as well as inter subtype-conserved epitopes along the HA proteins. Selected subtype-specific epitopes were shown to be suitable for the differentiation of anti-HA antibodies in an ELISA.
PLoS ONE 01/2010; 5(2):e9097. · 4.09 Impact Factor
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ABSTRACT: Twenty-seven sheep of the four most common Swiss breeds and the English breed Poll Dorset were experimentally infected with a northern European field strain of bluetongue virus serotype 8 (BTV-8). Animals of all breeds developed clinical signs, viremia and pathological lesions, demonstrating that BTV-8 is fully capable of replicating and inducing bluetongue disease (BT) in the investigated sheep. Necropsy performed between 10 and 16 days post-infectionem (d.p.i.) revealed BT-typical hemorrhages, effusions, edema, erosions and activation of lymphatic tissues. Hemorrhages on the base of the Arteria pulmonalis and the left Musculus papillaris subauricularis were frequently present. Histology confirmed the macroscopical findings. Using a score system, clinical manifestation and pathology were found to be significantly related. Furthermore, clinical signs and fever were shown to be indicative for the concurrent presence of high amounts of viral ribonucleic acid (RNA) in blood. Spleen, lung, lymph nodes and tonsils from all animals were analyzed regarding viral RNA loads and infectivity using real-time reverse transcriptase PCR (rRT-PCR) and virus isolation in cell culture, respectively. The highest amount of viral RNA was detected in spleen and lung and rRT-PCR revealed to be a more sensitive method for virus detection compared to virus isolation. A long-term follow-up was performed with three sheep showing that BTV-8 viral RNA in blood was present up to 133 d.p.i. and in certain tissues even on 151 d.p.i. No significant breed-related differences were observed concerning clinicopathological picture and viremia, and the Swiss sheep were as susceptible to BTV-8 infection as Poll Dorset sheep, demonstrating a remarkably high virulence of BTV-8 for indigenous sheep breeds.
Veterinary Microbiology 01/2010; 144(3-4):264-73. · 3.33 Impact Factor
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ABSTRACT: A novel bluetongue virus (BTV) termed Toggenburg orbivirus (TOV) was detected in goats from Switzerland by using real-time reverse transcription-PCR. cDNA corresponding to the complete sequence of 7 of 10 double-stranded RNA segments of the viral genome was amplified by PCR and cloned into a plasmid vector. Five clones for each genome segment were sequenced to determine a consensus sequence. BLAST analysis and dendrogram construction showed that TOV is closely related to BTV, although some genome segments are distinct from the 24 known BTV serotypes. Maximal sequence identity to any BTV ranged from 63% (segment 2) to 79% (segments 7 and 10). Because the gene encoding outer capsid protein 2 (VP2), which determines the serotype of BTV, is placed within the BTV serogroup, we propose that TOV represents an unknown 25th serotype of BTV.
Emerging Infectious Diseases 01/2009; 14(12):1855-61. · 6.79 Impact Factor
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Nicolas Ruggli,
Artur Summerfield,
Ana R Fiebach,
Laurence Guzylack-Piriou,
Oliver Bauhofer,
Catherine G Lamm,
Sandro Waltersperger,
Keita Matsuno,
Luzia Liu,
Markus Gerber,
Kyung H Choi, Martin A Hofmann,
Yoshihiro Sakoda,
Jon-Duri Tratschin
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ABSTRACT: Pestiviruses prevent alpha/beta interferon (IFN-alpha/beta) production by promoting proteasomal degradation of interferon regulatory factor 3 (IRF3) by means of the viral N(pro) nonstructural protein. N(pro) is also an autoprotease, and its amino-terminal coding sequence is involved in translation initiation. We previously showed with classical swine fever virus (CSFV) that deletion of the entire N(pro) gene resulted in attenuation in pigs. In order to elaborate on the role of the N(pro)-mediated IRF3 degradation in classical swine fever pathogenesis, we searched for minimal amino acid substitutions in N(pro) that would specifically abrogate this function. Our mutational analyses showed that degradation of IRF3 and autoprotease activity are two independent but structurally overlapping functions of N(pro). We describe two mutations in N(pro) that eliminate N(pro)-mediated IRF3 degradation without affecting the autoprotease activity. We also show that the conserved standard sequence at these particular positions is essential for N(pro) to interact with IRF3. Surprisingly, when these two mutations are introduced independently in the backbones of highly and moderately virulent CSFV, the resulting viruses are not attenuated, or are only partially attenuated, in 8- to 10-week-old pigs. This contrasts with the fact that these mutant viruses have lost the capacity to degrade IRF3 and to prevent IFN-alpha/beta induction in porcine cell lines and monocyte-derived dendritic cells. Taken together, these results demonstrate that contrary to previous assumptions and to the case for other viral systems, impairment of IRF3-dependent IFN-alpha/beta induction is not a prerequisite for CSFV virulence.
Journal of Virology 12/2008; 83(2):817-29. · 5.40 Impact Factor
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ABSTRACT: Bovine spongiform encephalopathy (BSE) rapid tests and routine BSE-testing laboratories underlie strict regulations for approval. Due to the lack of BSE-positive control samples, however, full assay validation at the level of individual test runs and continuous monitoring of test performance on-site is difficult. Most rapid tests use synthetic prion protein peptides, but it is not known to which extend they reflect the assay performance on field samples, and whether they are sufficient to indicate on-site assay quality problems. To address this question we compared the test scores of the provided kit peptide controls to those of standardized weak BSE-positive tissue samples in individual test runs as well as continuously over time by quality control charts in two widely used BSE rapid tests. Our results reveal only a weak correlation between the weak positive tissue control and the peptide control scores. We identified kit-lot related shifts in the assay performances that were not reflected by the peptide control scores. Vice versa, not all shifts indicated by the peptide control scores indeed reflected a shift in the assay performance. In conclusion these data highlight that the use of the kit peptide controls for continuous quality control purposes may result in unjustified rejection or acceptance of test runs. However, standardized weak positive tissue controls in combination with Shewhart-CUSUM control charts appear to be reliable in continuously monitoring assay performance on-site to identify undesired deviations.
Veterinary Microbiology 09/2008; 134(3-4):218-26. · 3.33 Impact Factor
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ABSTRACT: The nonstructural protein NS2-3 of pestiviruses undergoes tightly regulated processing. For bovine viral diarrhea virus it was shown that uncleaved NS2-3 is required for infectious particle formation while cleaved NS3 is essential for genome replication. To further investigate the functions of NS2-3 and NS4A in the pestivirus life cycle, we established T7 RNA polymerase-dependent trans-complementation for p7-NS2-3-4A of classical swine fever virus (CSFV). Expression of NS2-3 and NS4A in trans restored the production of infectious particles from genomes lacking NS2-3 expression. Co-expression of cleaved NS4A was essential. None of the enzymatic activities harbored by NS2-3 were required for infectious particle formation. Importantly, expression of uncleavable NS2-3 together with NS4A rescued infectious particles from a genome lacking NS2, demonstrating that cleaved NS2 per se has no additional essential function. These data indicate that NS2-3 and NS3, each in association with NS4A, have independent functions in the CSFV life cycle.
Virology 10/2007; 365(2):376-89. · 3.35 Impact Factor
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ABSTRACT: The use of attenuated classical swine fever virus (CSFV) strains as live vaccines is no longer allowed for the control of classical swine fever in Europe, due to the inability to differentiate between infected and vaccinated animals (Differentiating Infected from Vaccinated Animals; DIVA), except as emergency vaccines or as bait vaccines for wild boars. Thus, the establishment of a DIVA vaccine(s) is of pivotal importance for the control of this infectious disease. In this study, recombinant versions of the live-attenuated vaccine strain CSFV Riems were generated by replacing parts of the E2 gene with the corresponding sequence of border disease virus strain Gifhorn. Three cDNA clones were constructed: pRiems-ABC-Gif, pRiems-A-Gif and pRiems-BC-Gif. Infectious particles were obtained from clones pRiems-ABC-Gif and pRiems-BC-Gif only, whereas transfected RNA from clone pRiems-A-Gif behaved like a replicon. Based on its ability to be differentiated in vitro from wild-type CSFV by mAbs, vRiems-ABC-Gif was assessed for immunogenicity and protection against challenge infection in pigs. Before challenge, no CSFV-specific anti-E2 antibodies could be detected with commercial E2-blocking ELISAs in vRiems-ABC-Gif-vaccinated animals, whereas vRiems-vaccinated pigs developed high titres of anti-E2 antibodies, confirming the marker properties of this vaccine candidate. After oral vaccination, only partial protection against challenge infection was observed in the vRiems-ABC-Gif vaccinees, whereas all intramuscularly vaccinated animals and all vRiems-vaccinated animals were fully protected. These experiments suggest that the strategy of exchanging specific antigenic epitopes among pestiviruses is a promising tool for the development of new CSFV marker vaccines.
Journal of General Virology 09/2007; 88(Pt 8):2247-58. · 3.36 Impact Factor
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ABSTRACT: Viruses have evolved a multitude of strategies to subvert the innate immune system by interfering with components of the alpha/beta interferon (IFN-alpha/beta) induction and signaling pathway. It is well established that the pestiviruses prevent IFN-alpha/beta induction in their primary target cells, such as epitheloidal and endothelial cells, macrophages, and conventional dendritic cells, a phenotype mediated by the viral protein N(pro). Central players in the IFN-alpha/beta induction cascade are interferon regulatory factor 3 (IRF3) and IRF7. Recently, it was proposed that classical swine fever virus (CSFV), the porcine pestivirus, induced the loss of IRF3 by inhibiting the transcription of IRF3 mRNA. In the present study, we show that endogenous IRF3 and IRF3 expressed from a cytomegalovirus (CMV) promoter are depleted in the presence of CSFV by means of N(pro), while CSFV does not inhibit CMV promoter-driven protein expression. We also demonstrate that CSFV does not reduce the transcriptional activity of the IRF3 promoter and does not affect the stability of IRF3 mRNA. In fact, CSFV N(pro) induces proteasomal degradation of IRF3, as demonstrated by proteasome inhibition studies. Furthermore, N(pro) coprecipitates with IRF3, suggesting that the proteasomal degradation of IRF3 is induced by a direct or indirect interaction with N(pro). Finally, we show that N(pro) does not downregulate IRF7 expression.
Journal of Virology 05/2007; 81(7):3087-96. · 5.40 Impact Factor
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ABSTRACT: Classical swine fever virus replicon particles (CSF-VRP) deficient for Erns were eval- uated as a non-transmissible marker vaccine. A cDNA clone of CSFV strain Alfort/187 was used to obtain a replication-competent mutant genome (replicon) lacking the sequence encoding the 227 amino acids of the glycoprotein Erns (A187delErns). For packaging of A187delErns into virus parti- cles, porcine kidney cell lines constitutively expressing Erns of CSFV were established. The rescued VRP were infectious in cell culture but did not yield infectious progeny virus. Single intradermal vaccination of two pigs with 107 TCID50 of VRP A187delErns elicited neutralizing antibodies, anti- E2 antibodies, and cellular immune responses determined by an increase of IFN-γ producing cells. No anti-Erns antibodies were detected in the vaccinees confirming that this vaccine represents a negative marker vaccine allowing differentiation between infected and vaccinated animals. The two pigs were protected against lethal challenge with the highly virulent CSFV strain Eystrup. In con- trast, oral immunization resulted in only partial protection, and neither CSFV-specific antibodies nor stimulated T-cells were found before challenge. These data represent a good basis for more extended vaccination/challenge trials including larger numbers of animals as well as more thorough analysis of virus shedding using sentinel animals to monitor horizontal spread of the challenge virus. pestivirus / classical swine fever virus / Erns / replicon / marker vaccine
Veterinary Research - VET RES. 01/2006; 37(5):655-670.
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ABSTRACT: Classical swine fever virus (CSFV) protects cells from double-stranded (ds) RNA-mediated apoptosis and IFN-alpha/beta induction. This phenotype is lost when CSFV lacks N(pro) (DeltaN(pro) CSFV). In the present study, we demonstrate that N(pro) counteracts dsRNA-mediated apoptosis and IFN-alpha/beta induction independently of other CSFV elements. For this purpose, we generated porcine SK-6 and PK-15 cell lines constitutively expressing N(pro) fused to the enhanced green fluorescent protein (EGFP). The survival of the SK6-EGFP-N(pro) cell line after polyinosinic polycytidylic acid [poly(IC)] treatment was comparable to that of CSFV-infected SK-6 cells and was significantly higher than the survival of the parent cell line. In PK-15 cells, the presence of EGFP-N(pro) prevented the DeltaN(pro) CSFV- and poly(IC)-mediated IFN-alpha/beta production. Importantly, N(pro) also inhibited IFN-alpha and IFN-beta promoter-driven luciferase expression in human cells and blocked IFN-alpha/beta induction mediated by Newcastle disease virus. This establishes a novel function for N(pro) in counteraction of the IFN-alpha/beta induction pathway.
Virology 10/2005; 340(2):265-76. · 3.35 Impact Factor
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ABSTRACT: A cDNA clone of the classical swine fever virus (CSFV) strain Alfort/187 [Ruggli N, Tratschin JD, Mittelholzer C, Hofmann MA. Nucleotide sequence of classical swine fever virus strain Alfort/187 and transcription of infectious RNA from stably cloned full-length cDNA. J Virol 1996;70(6):3478-87] was used to construct two E2 deletion mutants lacking either the complete E2 gene or, alternatively, a stretch of 204 nucleotides encoding 68 amino acids located in the C-terminal region of the E2 glycoprotein. The respective in vitro synthesized mutant RNAs replicated in SK-6 cells but no infectious virus was generated. Both replicons could be packaged into virus particles in SK-6 cells constitutively expressing E2 of CSFV. For the resulting CSF virus replicon particles (CSF-VRP) A187-E2del373 and A187-E2del68 titers of 10(6) and 10(7) TCID(50)/ml, respectively, were obtained. Oronasal vaccination with 10(7) TCID(50) of either of the two CSF-VRP protected pigs against a challenge with a lethal dose of CSFV strain Eystrup. In contrast, after intradermal vaccination VRP A187-E2del68 but not VRP A187-E2del373 lacking the complete E2 gene induced a protective immune response. We conclude that E2-complemented CSF-VRP have the potential to be used as live-attenuated non-transmissible oral vaccines for pigs. In addition, our data suggest that E2 of CSFV is dispensable for the induction of mucosal but not of parenteral immunity.
Vaccine 06/2005; 23(25):3318-28. · 3.77 Impact Factor
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ABSTRACT: We have reported earlier that replacement of the N(pro) gene of classical swine fever virus (CSFV) by the murine ubiquitin gene only slightly affects the characteristics of virus replication in the porcine kidney cell line SK-6 [J. Virol. 72 (1998) 7681]. Here, for the moderately virulent CSFV strain Alfort/187 as well as for the highly virulent strain Eystrup we show that the respective N(pro)-deleted viruses are attenuated. Vaccination of pigs with either of the two deletion mutants resulted in the induction of a strong antibody response. Animals were protected against challenge with a lethal dose of highly virulent CSFV indicating that N(pro) deletion mutants are excellent candidates for a modified live virus vaccine. A chimeric virus obtained by replacement of the N(pro) gene in the Eystrup virus by the corresponding sequence of the avirulent CSFV vaccine strain Riems resulted in a virus that was highly virulent. This indicates that the virulence of CSFV correlates with the presence of N(pro) and also suggests that N(pro) is not responsible for the varying virulence observed between individual strains of CSFV.
Vaccine 02/2004; 22(3-4):317-28. · 3.77 Impact Factor
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ABSTRACT: The virulence of classical swine fever virus (CSFV) strains including established laboratory strains as well as field isolates ranges from avirulent to highly virulent. Here, we describe the construction and characterisation of two cDNA-derived CSFV strains, each corresponding to one of these extremes. The recombinant virus vEy-37 caused acute disease indistinguishable from that provoked by infection with the highly virulent parent strain Eystrup. In contrast, vRiems-3, a molecular clone of the CSFV vaccine strain Riems, was avirulent and induced protective immunity in pigs. After repeated passage of vEy-37 in porcine kidney SK-6 cells adaptive mutations in the E(rns) gene were observed. The respective reconstructed mutant virus grew to titres that were almost 4log units higher when compared to vEy-37. The mutation in the E(rns) gene had only a minor effect on the virulence of the virus. The complete genomic sequences of the two CSFV strains, Eystrup and Riems, have been deposited in GenBank (accession number AF326963 for CSFV Eystrup, AY259122 for CSFV Riems/IVI).
Virus Research 01/2004; 98(2):105-16. · 2.94 Impact Factor
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Martin A Hofmann
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ABSTRACT: RT-PCR is used widely as a diagnostic method to detect and differentiate pestiviruses. The construction of two chimeric classical swine fever virus (CSFV) recombinants based on a marker virus constructed previously [J. Virol. 72 (1998) 5318-5322] is described. These viruses, termed vA187CAT_5UTRBVD and vA187CAT_IRESBVD, contain the entire 5' untranslated region (5'UTR) or the internal ribosome entry site (IRES) of bovine viral diarrhea virus (BVDV), respectively. Both chimeric viruses proved to be infectious in cell culture. Hence, the 5'UTR as well as the IRES element only of BVDV can substitute for the corresponding genome region of CSFV. Next, two sets of primers and corresponding dual-labeled TaqMan probes were designed; one detecting specifically a conserved but CSFV-specific area within the 5'UTR of wild-type CSFV, the other one targeting the CAT gene inserted in vA187CAT_5UTRBVD. The two primer/probe sets were combined in a closed-tube multiplex one-step RT-PCR. To monitor the entire extraction and detection process limited amounts of vA187CAT_5UTRBVD were added directly to clinical samples before RNA extraction. The multiplex RT-PCR proved to be as sensitive as the single primer/probe set method, but allowed the validation of each sample tested individually, based on the detection of the CAT marker gene. vA187CAT_5UTRBVD was also used successfully for foot-and-mouth disease virus (FMDV) TaqMan RT-PCR. Therefore, it is considered a universal internal positive control for RT-PCR assays to exclude loss of RNA during extraction, or failure of amplification due to inhibitory substances present in the sample.
Journal of Virological Methods 01/2004; 114(1):77-90. · 2.01 Impact Factor
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ABSTRACT: Classical swine fever virus (CSFV) replicates efficiently in cell lines and monocytic cells, including macrophages (MPhi), without causing a cytopathic effect or inducing interferon (IFN) secretion. In the present study, the capacity of CSFV to interfere with cellular antiviral activity was investigated. When the porcine kidney cell line SK-6 was infected with CSFV, there was a 100-fold increased capacity to resist to apoptosis induced by polyinosinic-polycytidylic acid [poly(IC)], a synthetic double-stranded RNA. In MPhi, the virus infection inhibited poly(IC)-induced alpha/beta IFN (type I IFN) synthesis. This interference with cellular antiviral defense correlated with the presence of the viral N(pro) gene. Mutants lacking the N(pro) gene (DeltaN(pro) CSFV) did not protect SK-6 cells from poly(IC)-induced apoptosis, despite growth properties and protein expression levels similar to those of the wild-type virus. Furthermore, DeltaN(pro) CSFV did not prevent poly(IC)-induced type I IFN production in MPhi but rather induced type I IFN in the absence of poly(IC) in both MPhi and the porcine kidney cell line PK-15, but not in SK-6 cells. With MPhi and PK-15, an impaired replication of the DeltaN(pro) CSFV compared with wild-type virus was noted. In addition, DeltaN(pro) CSFV, but not wild-type CSFV, could interfere with vesicular stomatitis virus replication in PK-15 cells. Taken together, these results provide evidence for a novel function associated with CSFV N(pro) with respect to the inhibition of the cellular innate immune system.
Journal of Virology 08/2003; 77(13):7645-54. · 5.40 Impact Factor
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Journal of Virology - J VIROL. 01/2003; 77(13):7645-7654.
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ABSTRACT: Two types of porcine reproductive and respiratory syndrome virus (PRRSV) have been reported, the European type (EU PRRSV) and the North American type (US PRRSV). We developed a dual enzyme-linked immunosorbent assay (ELISA) for the simultaneous detection and differentiation of serum antibodies directed against either of the two PRRSV types. This tandem PRRS ELISA is based on affinity-purified recombinant nucleocapsid protein expressed in Escherichia coli. Sensitivity and specificity were assessed by using the IDEXX HerdChek PRRS ELISA and the indirect immunofluorescence assay as reference tests. A total of 1571 sera originating from the United States, Europe, and two PRRS-free countries, i.e., Switzerland and New Zealand, were used for validation of the tandem PRRS ELISA. The new test performed at least as well as the reference tests in regard to sensitivity (0.94 for the US PRRS ELISA and 0.93 for the EU PRRS ELISA) and specificity (0.96 for the US PRRS ELISA and 0.99 for the EU PRRS ELISA). Positive sera were correctly differentiated in 582 of 591 cases, indicating a high differentiation capability of this dual ELISA. The robustness and repeatability of the test were assessed and found to be appropriate for diagnostic applications. Taken together, the data indicate that the tandem PRRS ELISA described here is the first differentiation ELISA for PRRSV serology based on recombinant antigen. It is convenient with respect to antigen production, and it is reliable, economical, and highly sensitive and specific. Thus, it is considered to be a powerful tool for routine diagnostics, epidemiological surveys, and outbreak investigations.
Clinical and Diagnostic Laboratory Immunology 12/2002; 9(6):1183-91. · 2.51 Impact Factor
