Author
Dan Chladek
Bio: Dan Chladek is an academic researcher from Boehringer Ingelheim. The author has contributed to research in topics: Virus & Arterivirus. The author has an hindex of 5, co-authored 5 publications receiving 1800 citations.
Papers
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TL;DR: This is the first isolate of SIRS virus in the United States that fulfills Koch's postulates in producing the respiratory form of the disease in gnotobiotic piglets and the first report of isolation and propagation of the virus on a continuous cell line (CL2621).
Abstract: A recent epizootic of swine infertility and respiratory syndrome (SIRS) in a Minnesota swine herd was investigated. Examination of a sow, neonatal piglets, and stillborn fetuses obtained during the epizootic from the affected herd revealed interstitial pneumonitis, lymphomononuclear encephalitis, and lymphomononuclear myocarditis in the piglets and focal vasculitis in the brain of the sow. Fetuses did not have microscopic lesions. No cause for the infertility and respiratory syndrome was determined. Therefore, attempts were made to experimentally reproduce the disease. Eleven 3-day-old gnotobiotic piglets exposed intranasally to tissue homogenates of piglets from the epizootic became inappetent and febrile by 2-4 days postexposure and had interstitial pneumonitis and encephalitis similar to that seen in the field outbreak. After 2 blind passages in gnotobiotic piglets, tissue homogenates were cultured on continuous cell line CL2621, and a cytopathic virus (ATCC VR-2332), provisionally named SIRS virus, was isolated. Gnotobiotic piglets exposed intranasally to the SIRS virus developed clinical signs and microscopic lesions that were the same as those in piglets exposed to the tissue homogenates, and the virus was reisolated from their lungs. This is the first isolate of SIRS virus in the United States that fulfills Koch's postulates in producing the respiratory form of the disease in gnotobiotic piglets and the first report of isolation and propagation of the virus on a continuous cell line (CL2621). The virus is designated as American Type Culture Collection VR-2332.
818 citations
TL;DR: The characterization of an isolate of swine infertility and respiratory syndrome (SIRS) virus (ATCC VR-2332) is reported and it is indicated that this isolate is a fastidious, nonhemagglutinating, enveloped RNA virus.
Abstract: The characterization of an isolate of swine infertility and respiratory syndrome (SIRS) virus (ATCC VR-2332) is reported. A commercial cell line (CL262 1) was used for the propagation of the virus for all assays. Laboratory studies indicate that this isolate is a fastidious, nonhemagglutinating, enveloped RNA virus. Cesium chloride-purified virions visualized by electron microscopy were spherical particles with an average diameter of 62 nm (range: 48–83 nm) and a 25–30 nm core surrounded by an envelope. Virus replication was restricted to the cytoplasm, as demonstrated by immunofluorescence. The virus did not react serologically with antisera to several common porcine viruses or with antisera to known viruses in the alphavirus, rubivirus, pestivirus, and ungrouped lactic dehydrogenase virus genera of the Togaviridae. However, convalescent sow sera and rabbit hyperimmune sera neutralized the SIRS virus at titers of 1:256 and 1:512, respectively. The virus was stable at 4 and −70 C, but was labile at 37 and...
731 citations
TL;DR: This study reports the antigenic relatedness of isolates of Lelystad virus collected in the Netherlands, Germany, and the United States, and found 4 European isolates resembled each other closely, but differed from the American isolates, and 3 American isolate differed antigenically from each other.
Abstract: This study reports the antigenic relatedness of isolates of Lelystad virus collected in the Netherlands, Germany, and the United States. The binding of antibodies directed against these isolates was tested in a set of field sera collected during outbreaks of porcine epidemic abortion and respiratory syndrome in Europe and outbreaks of swine infertility and respiratory syndrome (SIRS) in North America. Two sets of sera from pigs experimentally infected with Lelystad virus or SIRS virus were also tested. Although all 7 isolates reacted with anti-Lelystad virus sera, antigenic variation was considerable. The 4 European isolates resembled each other closely, but differed from the American isolates, and the 3 American isolates differed antigenically from each other. To reliably diagnose Lelystad virus infection, a common antigen must first be identified.
242 citations
01 Jan 1992
TL;DR: Sera were collected from approximately 30 representative sows at each of these 16 herds and swine infertility and respiratory syndrome and the absence of anorexia in 2 herds and absence of dyspnea in 1 herd may reflect a failure of detection rather than absence of these clinical signs.
58 citations
TL;DR: In this article, the absence of anorexia in two herds and absence of dyspnea in one herd may reflect a failure of detection rather than absence of these clinical signs.
Abstract: and swine infertility and respiratory syndrome (SIRS). tality ranged from 37% to 83% and was accompanied by late term (>day 100) abortion in all but 1 herd. The absence of anorexia in 2 herds and absence of dyspnea in 1 herd may reflect a failure of detection rather than absence of these clinical signs (Table 2). Each case herd was matched with a herd located within 10 miles, of similar size and type of production, and having no history of undiagnosed reproductive failure or respiratory disease in the last 3 years. Sera were collected from approximately 30 representative sows at each of these 16 herds.
55 citations
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TL;DR: The establishment of an arterivirus family acknowledges many many uniquebiological and molecular properties of its four present members and theiation with thecoronaviruses recognizes anriguing chain relationship at the level ofgenomeorganization and replication.
Abstract: .The establishment of an arterivirus family acknowledgesthemanyuniquebiologicalandmolecularpropertiesofitsfourpresent members. On the other hand, the affiliation with thecoronavirusesrecognizesanintriguingancestralrelationshipatthelevelofgenomeorganizationandreplication.ThegenomesequencesofEAV,PRRSV,LDVandSHFVwereinstrumentalin uniting and reclassifying the arteriviruses (den Boon
852 citations
TL;DR: Persistent PRRSV infections are an important factor for virus survival and transmission within a swine herd and will complicate control programs.
Abstract: In 1987, porcine reproductive and respiratory syndrome (PRRS) was recognized in the USA as a new disease of swine causing late-term reproductive failure and severe pneumonia in neonatal pigs. The syndrome is caused by an RNA virus referred to as PRRS virus (PRRSV), which is classified in the family Arteriviridae. Swine macrophages are the only indigenous cell type known to support PRRSV replication. Direct contact between infected and naive pigs is the predominant route of PRRSV transmission. Exposure of a mucosal surface to PRRSV leads to virus replication in regional macrophages, a prolonged viremia and systemic distribution of virus to other macrophage populations. Reproductive failure induced by PRRSV infection in late-gestation sows is characterized by premature farrowing of stillborn, partially autolyzed, and mummified fetuses. Pneumonia caused by PRRSV infection is more severe in young pigs compared to adults and may be complicated by concurrent bacterial infections. Gross lung lesions associated w...
829 citations
TL;DR: This is the first isolate of SIRS virus in the United States that fulfills Koch's postulates in producing the respiratory form of the disease in gnotobiotic piglets and the first report of isolation and propagation of the virus on a continuous cell line (CL2621).
Abstract: A recent epizootic of swine infertility and respiratory syndrome (SIRS) in a Minnesota swine herd was investigated. Examination of a sow, neonatal piglets, and stillborn fetuses obtained during the epizootic from the affected herd revealed interstitial pneumonitis, lymphomononuclear encephalitis, and lymphomononuclear myocarditis in the piglets and focal vasculitis in the brain of the sow. Fetuses did not have microscopic lesions. No cause for the infertility and respiratory syndrome was determined. Therefore, attempts were made to experimentally reproduce the disease. Eleven 3-day-old gnotobiotic piglets exposed intranasally to tissue homogenates of piglets from the epizootic became inappetent and febrile by 2-4 days postexposure and had interstitial pneumonitis and encephalitis similar to that seen in the field outbreak. After 2 blind passages in gnotobiotic piglets, tissue homogenates were cultured on continuous cell line CL2621, and a cytopathic virus (ATCC VR-2332), provisionally named SIRS virus, was isolated. Gnotobiotic piglets exposed intranasally to the SIRS virus developed clinical signs and microscopic lesions that were the same as those in piglets exposed to the tissue homogenates, and the virus was reisolated from their lungs. This is the first isolate of SIRS virus in the United States that fulfills Koch's postulates in producing the respiratory form of the disease in gnotobiotic piglets and the first report of isolation and propagation of the virus on a continuous cell line (CL2621). The virus is designated as American Type Culture Collection VR-2332.
818 citations
TL;DR: The characterization of an isolate of swine infertility and respiratory syndrome (SIRS) virus (ATCC VR-2332) is reported and it is indicated that this isolate is a fastidious, nonhemagglutinating, enveloped RNA virus.
Abstract: The characterization of an isolate of swine infertility and respiratory syndrome (SIRS) virus (ATCC VR-2332) is reported. A commercial cell line (CL262 1) was used for the propagation of the virus for all assays. Laboratory studies indicate that this isolate is a fastidious, nonhemagglutinating, enveloped RNA virus. Cesium chloride-purified virions visualized by electron microscopy were spherical particles with an average diameter of 62 nm (range: 48–83 nm) and a 25–30 nm core surrounded by an envelope. Virus replication was restricted to the cytoplasm, as demonstrated by immunofluorescence. The virus did not react serologically with antisera to several common porcine viruses or with antisera to known viruses in the alphavirus, rubivirus, pestivirus, and ungrouped lactic dehydrogenase virus genera of the Togaviridae. However, convalescent sow sera and rabbit hyperimmune sera neutralized the SIRS virus at titers of 1:256 and 1:512, respectively. The virus was stable at 4 and −70 C, but was labile at 37 and...
731 citations
TL;DR: The presence of substantial variations across the entire genome and in sgmRNA processing indicates that PRRSV has evolved independently on separate continents, and suggests that changes in swine husbandry and management may have contributed to the emergence of PRRS.
Abstract: Porcine reproductive and respiratory syndrome virus (PRRSV) is a recently described arterivirus responsible for disease in swine worldwide. Comparative sequence analysis of 3′-terminal structural genes of the single-stranded RNA viral genome revealed the presence of two genotypic classes of PRRSV, represented by the prototype North American and European strains, VR-2332 and Lelystad virus (LV), respectively. To better understand the evolution and pathogenicity of PRRSV, we obtained the 12,066-base 5′-terminal nucleotide sequence of VR-2332, encoding the viral replication activities, and compared it to those of LV and other arteriviruses. VR-2332 and LV differ markedly in the 5′ leader and sections of the open reading frame (ORF) 1a region. The ORF 1b sequence was nearly colinear but varied in similarity of proteins encoded in identified regions. Furthermore, molecular and biochemical analysis of subgenomic mRNA (sgmRNA) processing revealed extensive variation in the number of sgmRNAs which may be generated during infection and in the lengths of noncoding sequence between leader-body junctions and the translation-initiating codon AUG. In addition, VR-2332 and LV select different leader-body junction sites from a pool of similar candidate sites to produce sgmRNA 7, encoding the viral nucleocapsid protein. The presence of substantial variations across the entire genome and in sgmRNA processing indicates that PRRSV has evolved independently on separate continents. The near-simultaneous global emergence of a new swine disease caused by divergently evolved viruses suggests that changes in swine husbandry and management may have contributed to the emergence of PRRS.
700 citations