To develop an attenuated vaccine against the highly pathogenic porcine reproductive and respiratory syndrome (HP-PRRS) virus, the HP-PRRS virus strain TJ was attenuated by serial passages and plaque cloned every 5 to 10 passages in Marc-145 cells. Genetic variation and pathogenicity of HP-PRRSV strain TJ in the course of attenuation were analyzed. The results showed that the strain TJ sustained various sequence changes during the course of attenuation. Fifty-eight amino acids changes and a new continuous 120 amino acids deletion after the discontinuous 30 amino acids deletion (sites 481 and 533-561) occurred in strain TJ passages 140, and the position of 120 amino acids deletion was between 628 to 747 according to VR-2332. Animal test showed that the pathogenicity of strain TJ passages 20 was attenuated obviously, so we presume that genetic variation in nonstructural protein nsp2-nsp5, nsp7 and structural protein GP5 during the attenuation provides the molecular bases for the observed attenuated phenotype.
Amino Acid Sequence ; Animals ; Genetic Variation ; Molecular Sequence Data ; Porcine Reproductive and Respiratory Syndrome ; virology ; Porcine respiratory and reproductive syndrome virus ; classification ; genetics ; isolation & purification ; pathogenicity ; Sequence Deletion ; Serial Passage ; Swine ; Vaccines, Attenuated ; genetics ; isolation & purification ; Virulence

Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the important pathogens causing serious economic losses to swine industry worldwide. PRRSV is genetically and pathologically heterogenous. PRRSV NT0801 strain was isolated in a pig farm with clinical signs and had high pathogenesis in piglets. But its NSP2 gene did not have 30 amino acids deletion as highly pathogenic JXA1 strain. To elucidate the genetic characteristics of PRRSV NT0801 strain, the full-length genome of NT0801 isolate was sequenced and analyzed. The results showed that the genome of PRRSV NT0801 was 15439bp in length, including 29nt Poly(A) tail. Compared with the highly pathogenic JXA1 strain, it had the nucleotide sequence identity of 96.7%, amino acid sequence homology of 97.2% and 98.5% in GP3 and GP5, respectively. Phylogenetic analysis indicated that NT0801 isolate was located between the traditional strain and the highly pathogenic strain. But no obvious recombination signal was observed, compared with other PRRSV isolates with different virulence. The alignment of amino acid sequence of NT0801 with other PRRSV isolates demonstrated that three out of nine sites, being consistent with the highly pathogenic strain, were different from those in highly pathogenic while same as those in traditional strains and JXA1 vaccine strain. And one out of 9 sites was same as that of JXA1 vaccine strain exclusively, two out of 9 sites were different from all the strains. These results indicated that PRRSV NT0801 strain is closely related to highly pathogenic PRRSV, although there has no 30 amino acids deletions in NSP2 region. The epidemic PRRSV strains variation results from the gene mutation. It should be useful for studying on the virulence genes located in different ORFs of PRRSV in the future.
Amino Acid Sequence ; Animals ; China ; Genome, Viral ; Molecular Sequence Data ; Phylogeny ; Porcine Reproductive and Respiratory Syndrome ; virology ; Porcine respiratory and reproductive syndrome virus ; genetics ; isolation & purification ; Sequence Homology, Amino Acid ; Swine

The objective of this study was to investigate the function of vimentin in PRRSV infection. Vimentin gene from Marc-145 cells was amplified by RT-PCR, cloned into pET-28a vector and expressed in Escherichia coli BL21(DE3). The expressed vimentin was confirmed by Western blot and purified which was used to immunize BALB/c mice for the production of antibodies. Vimentin and antibodies were tested for blocking PRRSV infection of Marc-145 cells. The binding of vimentin to PRRSV N and GP5 proteins were tested by the ELISA. The results showed that vimentin gene was amplified successfully and expressed as identified by SDS-PAGE and Western blot. Mouse anti-vimentin antibodies were produced with the titer of 10(5). PRRSV infection of Marc-145 cells was blocked partially by vimentin while blocked completely by the antibobies. In addition, vimentin was bound N protein, but not GP5. These results provide additional information on PRRSV entry into Marc-145 cells.
Animals ; Antibodies ; immunology ; metabolism ; Cell Line ; Escherichia coli ; genetics ; metabolism ; Female ; Genetic Vectors ; genetics ; Mice ; Mice, Inbred BALB C ; Porcine Reproductive and Respiratory Syndrome ; genetics ; metabolism ; virology ; Porcine respiratory and reproductive syndrome virus ; physiology ; Protein Binding ; physiology ; Recombinant Proteins ; genetics ; immunology ; isolation & purification ; metabolism ; Swine ; Vimentin ; genetics ; immunology ; isolation & purification ; metabolism ; Viral Proteins ; metabolism

The aim of this study is to establish the method of loop-mediated indirect PCR assay for detection of Reproductive and Respiratory Syndrome Virus (PRRSV) infection and differentiation of highly pathogenic PRRSV (HP-PRRSV) and lowly pathogenic PRRSV (LP-PRRSV). Based on the alignments of ORF2 gene sequences and ORFla gene sequences of PRRSV Chinese isolates deposited in GenBank, two pairs of specific probes were designed and labeled to both ends of the soybean Lectin gene fragment by PCR, respectively. The probe-labeled soybean Lectin genes were used to be reporter genes for detection and differentiation of PRRSV. After one round strand displacement reaction, the reporter genes were amplified by reverse PCR. The specific PCR products were 193bp, 355bp for HP-PRRSV and 193bp, 442bp for LP-PRRSV, respectively. The method could detect 5. 6 TCID50/mL LP-PRRSV RNA and 18 TCIDs0/ mL HP-PRRSV RNA, and co-infection did not affect detection sensitivity. No amplification was observed with other porcine originated pathogens including CSFV, PPV, PRV, PCV2, ETEC and Haemophilus parasui. Twenty clinical samples were used for comparative testing with conventional PCR. Fourteen samples were found positive for PRRSV by the loop-mediated indirect PCR, of which 4 were LP-PRRSV, 9 HP-PRRSV and 1 LP/HP-PRRSV co-infection, consistent with the conventional PCR test results. In conclusion, the loop-mediated indirect PCR is a simple, rapid, sensitive and specific etiologic diagnosis tool, and suitable for the differential diagnosis of HP/LP-PRRSV, especially for identification of mixed infection of HP/LP-PRRSV.
Animals ; Coinfection ; veterinary ; DNA Primers ; genetics ; DNA, Complementary ; genetics ; Diagnosis, Differential ; Genes, Reporter ; Genetic Markers ; genetics ; Humans ; Porcine Reproductive and Respiratory Syndrome ; diagnosis ; virology ; Porcine respiratory and reproductive syndrome virus ; genetics ; isolation & purification ; RNA, Viral ; genetics ; Reverse Transcriptase Polymerase Chain Reaction ; methods ; veterinary ; Sensitivity and Specificity ; Swine ; Time Factors ; Viral Proteins ; genetics

Porcine reproductive and respiratory syndrome virus(PRRSV)0, porcine circovirus type 2(PCV-2) and porcine parvovirus (PPV)0 infections were investigated as possible causes of the postweaning multisystemic wasting syndrome(PMWS). Specific primers for RT-PCR and PCR were designed for the differential detection of PRRSV, PCV-2 and PPV. Using PCR, these viruses were detected in homogenized tissue samples from pigs that had respiratory of reproductive problems in the time period between 1998 and 2000; the overall prevalences were: PRRSV 31.4%, PCV-2 46.5%, and PPV 8.1%. PCV-2 was also detected in aborted fetal tissues.
Aborted Fetus/virology ; Animals ; Base Sequence ; Circoviridae Infections/diagnosis/epidemiology/*veterinary ; Circovirus/genetics/isolation&purification ; DNA Primers ; Diagnosis, Differential ; Korea/epidemiology ; Parvoviridae Infections/diagnosis/epidemiology/*veterinary ; Parvovirus, Porcine/genetics/isolation&purification ; Polymerase Chain Reaction/methods/veterinary ; Porcine Reproductive and Respiratory Syndrome/diagnosis/*epidemiology ; Porcine respiratory and reproductive syndrome virus/genetics/isolation & purification ; Prevalence ; Respiratory Tract Infections/veterinary/virology ; Reverse Transcriptase Polymerase Chain Reaction/methods/veterinary ; Sequence Homology ; Swine ; Swine Diseases/diagnosis/*epidemiology ; Wasting Syndrome/*veterinary/virology

The capability of porcine reproductive and respiratory syndrome virus (PRRSV) to be shed in semen for extended periods of time has been suggested to be a principal factor for viral transmission via insemination. In attempts to gain insights into the mechanism of PRRSV persistence in boars, tissue distribution and sites of viral infection were investigated by in situ hybridization (ISH) using digoxigenin-labeled RNA probe and the ISH results were compared with those of reverse transcription-nested polymerase chain reaction (RT-nested PCR). Animals were intranasally inoculated with 104 median tissue culture infectious dose of PRRSV VR-2332 and tissues collected at different times were examined. At day 7 postinfection, limited number of hybridization positive signals was observed in cells within or between seminiferous tubules in the testis sections while relatively abundant hybridization positive signals were observed in the brain stem and tracheobronchial lymph node. At later days of infection, hybridization positive signals were observed in cells within seminiferous tubules with much reduced frequency. Lack of agreement with the RT-nested PCR assay results in testis tissues obtained at days 14, 28, and 59 postinfection suggested that PRRSV infection in the testis may be extremely restricted, and may not necessarily constitute a major viral source in semen during extended periods of seminal shedding.
Animals ; Brain Stem/virology ; Endopeptidase K/metabolism ; *In Situ Hybridization ; Lymph Nodes/virology ; Male ; Microwaves ; Porcine Reproductive and Respiratory Syndrome/transmission/*virology ; Porcine respiratory and reproductive syndrome virus/*genetics/*isolation & purification ; RNA Probes ; Reverse Transcriptase Polymerase Chain Reaction ; Semen/virology ; Seminiferous Tubules/virology ; Sensitivity and Specificity ; Sexually Transmitted Diseases, Viral/transmission/veterinary/virology ; Swine/*virology ; Testis/virology

Porcine reproductive and respiratory syndrome virus (PRRSV) RNA load in sera and tissues during acute phase of infection was evaluated using a PCR- based quantitative assay. More than 80% of infected pigs (21/25) showed the peak level of viral RNA concentrations in serum (up to 8.6 x 108 copies/ml) at day 5 postinfection (PI), and started to clear the virus from the systemic circulation thereafter. Regression analysis using the viral RNA concentrations in sera obtained from days 5 to 14 PI showed that the viral RNA was cleared at the rate of 0.37 log reduction in the number of PRRSV RNA copies per day. It was estimated to be day 27 PI when the viral RNA in the serum of infected pigs becomes undetectable. When correlation analysis was performed between the systemic clearance rate and viral RNA concentrations in tissues of 9 infected pigs obtained at day 14 PI, moderately strong negative correlation was observed in the thymus (r = - 0.62) and brain stem (r = - 0.48), suggesting the capability of host animal to clear PRRSV from the systemic circulation appears to be related to the viral activity in the thymus and brain stem.
Animals ; Brain Stem/virology ; Eye/virology ; Female ; Logistic Models ; Lymphoid Tissue/virology ; Male ; Porcine Reproductive and Respiratory Syndrome/blood/*virology ; Porcine respiratory and reproductive syndrome virus/*genetics/*isolation & purification ; RNA, Viral/*analysis ; Reference Standards ; Reverse Transcriptase Polymerase Chain Reaction ; Swine/*virology ; Time Factors ; *Viral Load ; Viremia/veterinary/virology

The high genetic diversity of porcine reproductive and respiratory syndrome virus (PRRSV) has been an obstacle to developing an effective vaccine for porcine reproductive and respiratory syndrome (PRRS). This study was performed to assess the degree of genetic diversity among PRRSVs from Korean pig farms where wasting and respiratory syndrome was observed from 2005 to 2009. Samples from 786 farms were tested for the presence of PRRSV using reverse transcription PCR protocol. A total of 117 farms were positive for type 1 PRRSV while 198 farms were positive for type 2. Nucleotide sequences encoding the open reading frame (ORF) 5 were analyzed and compared to those of various published PRRSV isolates obtained worldwide. Sequence identity of the ORF 5 in the isolates was 81.6~100% for type 1 viruses and 81.4~100% for type 2 viruses. Phylogenetic analysis of the ORF 5 sequences showed that types 1 and 2 PRRSVs from Korea were mainly classified into three and four clusters, respectively. The analyzed isolates were distributed throughout the clusters independent of the isolation year or geographical origin. In conclusion, our results indicated that the genetic diversity of PRRSVs from Korean pig farms is high and has been increasing over time.
Animal Husbandry ; Animals ; *Genes, Viral ; *Genetic Variation ; Lung/virology ; Lymph Nodes/virology ; *Open Reading Frames ; Phylogeny ; Porcine Reproductive and Respiratory Syndrome/virology ; Porcine respiratory and reproductive syndrome virus/chemistry/classification/*genetics/isolation & purification ; Republic of Korea ; Reverse Transcriptase Polymerase Chain Reaction/veterinary ; Sequence Analysis, DNA/veterinary ; Sequence Analysis, Protein/veterinary ; Swine