Research progress in porcine reproductive and respiratory syndrome virus and vaccine against it / 中国生物制品学杂志

@#Porcine reproductive and respiratory syndrome(PRRS),also known as blue ear disease,is an immunosuppressive disease caused by porcine reproductive and respiratory syndrome virus(PRRSV). PRRSV is an important infectious pathogen of porcine,which has the characteristics of easy recombination and mutation,high transmission ability,and has been widely spread in the world. At the same time,because of the characteristics of immunosuppression,immune evasion,and easy-to-cause antibody-dependent enhancement(ADE),the pathogen has brought serious challenges to the disease prevention and control of PRRS and the development of related vaccines. In this paper,the pathogenic process of PRRSV,immune evasion mechanism,and research progress in different types of PRRSV vaccines were reviewed,in order to provide ideas for the development of related vaccines in the future

Development of porcine induced pluripotent stem cells with a CD163 reporter system / 生物工程学报

As main recipient cells for porcine reproductive and respiratory syndrome virus (PRRSV), porcine alveolar macrophage (PAM) are involved in the progress of several highly pathogenic virus infections. However, due to the fact that the PAM cells can only be obtained from primary tissues, research on PAM-based virus-host interactions remains challenging. The improvement of induced pluripotent stem cells (iPSCs) technology provides a new strategy to develop IPSCs-derived PAM cells. Since the CD163 is a macrophage-specific marker and a validated receptor essential for PRRSV infection, generation of stable porcine induced pluripotent stem cells lines containing CD163 reporter system play important roles in the investigation of IPSCs-PAM transition and PAM-based virus-host interaction. Based on the CRISPR/Cas9- mediated gene editing system, we designed a sgRNA targeting CD163 locus and constructed the corresponding donor vectors. To test whether this reporter system has the expected function, the reporter system was introduced into primary PAM cells to detect the expression of RFP. To validate the low effect on stem cell pluripotency, we generated porcine iPSC lines containing CD163 reporter and assessed the pluripotency through multiple assays such as alkaline phosphatase staining, immunofluorescent staining, and EdU staining. The red-fluorescent protein (RFP) expression was detected in CD163-edited PAM cells, suggesting that our reporter system indeed has the ability to reflect the expression of gene CD163. Compared with wild-type (WT) iPSCs, the CD163 reporter-iPSCs display similar pluripotency-associated transcription factors expression. Besides, cells with the reporter system showed consistent cell morphology and proliferation ability as compared to WT iPSCs, indicating that the edited-cells have no effect on stem cell pluripotency. In conclusion, we generated porcine iPSCs that contain a CD163 reporter system. Our results demonstrated that this reporter system was functional and safe. This study provides a platform to investigate the iPS-PAM development and virus-host interaction in PAM cells.

Construction of recombinant PRRSV ORF5 gene by DNA shuffling technique / 生物工程学报

Recombinant PRRSV △2ORF5 gene was constructed using DNA shuffling from four genetically different strains of PRRSV to study its heterologous cross-neutralizing ability. The △2ORF5 mutant gene was cloned into the vector pET-32a and transferred into E. coli BL21. SDS-PAGE confirmed that the molecular weight of the recombinant △2ORF5 was about 42 kDa, consistent with the predicted result. Then the purified recombinant protein was injected into BALB/c mouse to obtain polyclonal antibody. Western blotting analysis with mouse-anti-△2ORF5 polyclonal serum indicated that the parental virus recombinant GP5 protein reacted with the specific antibodies. Four parental viruses could be inhibited by the anti-△2ORF5 polyclonal antibody and the inhibition rates were higher than 53%. This work has laid a foundation for further development vaccine for PRRSV.

Genetic variation analysis of Nsp2, ORF5 and ORF3 of PRRSV SC-GY strain from Sichuan province / 中国兽医学报

To monitor genetic variation of porcine reproductive and respiratory syndrome virus (PRRSV),RT-PCR was used to identify a sample suspected of PRRSV infection.A PRRSV named SC-GY strain was obtained,and its Nsp2,ORF5 and ORF3 genes were used for sequence alignment and phylogenetic tree construction.The results showed that SC-GY strain is highly pathogenic PRRSV American variant strains with Nsp2 gene discontinuous deletion of 30 amino acids,ORF3 gene aa17 a serine (S) insert.Comparing to VR2332,CH-1a,JXA1,HUN4,NADC30,HENAN-XINX and SC2012,the Nsp2,ORF5 and ORF3 of SC-GY shared 70.3％-97.9％,82.4％-97.6％ and 83.1％-98.2％ of nucleotide similarity,and 62.3％-96.3％,78.0％-95.7％ and 81.6％-96.5％ of deduced amino acid similarity;and compared to LV they shared only 18.9％,60.8％ and 63.7％ of nucleotide similarity,and 14.0％,54.9％ and 57.2％ of deduced amino acid similarity.The phylogenetic tree revealed that the SC-GY formed independent small branches although it belonged to the same subgroup as highly pathogenic PRRSV strains.The results showed that in high frequency live vaccine immunization of currently PRRSV,the gene of PRRSV epidemic strain is still in constant variation.Vaccination of live PRRSV vaccines should be reduced and surveillance of PRRSV strains should be enhanced.

Susceptibility screening of highly pathogenic porcine reproductive and respiratory syndrome virus in several strains of minipigs / 中国比较医学杂志

Objective To screen strains of minipigs sensitive to highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) for evaluation of HP-PRRS live vaccine.Methods Lantang pigs, Juema, Bama and Wuzhishan ( white) minipigs were inoculated with virulent strain NVDC-JXA1 of PRRSV, and local binary hybrid pigs were used as control.The animals were continuously observed for 5 weeks on mental status, appetite, survival, etc.after inoculation of virus.The dead pigs were autopsied and the lung tissue samples were collected for detecting virus by RT-PCR.By the end of the experiment, serum of survival animals were collected for detecting PRRSV antibody by ELISA assay.Result The animals showed depression, anorexia, and other clinical signs and death in each group after inoculation.Meanwhile, the testing results were all positive in the RT-PCR and ELISA detection.Bama and Wuzhishan ( white) minipigs were the most sensitive to virulent strain NVDC-JXA1 of PRRSV regarding mortality rate.Conclusions Bama and Wuzhishan ( white) minipigs are sensitive to HP-PRRSV, and can be used for the inspection of HP-PRRS live vaccine.

Recombinant Kluyveromyces lactis expressing highly pathogenic porcine reproductive and respiratory syndrome virus GP5 elicits mucosal and cell-mediated immune responses in mice

Currently, killed-virus and modified-live porcine reproductive and respiratory syndrome virus (PRRSV) vaccines are used to control porcine reproductive and respiratory syndrome. However, both types of vaccines have inherent drawbacks; accordingly, the development of novel PRRSV vaccines is urgently needed. Previous studies have suggested that yeast possesses adjuvant activities, and it has been used as an expression vehicle to elicit immune responses to foreign antigens. In this report, recombinant Kluyveromyces lactis expressing GP5 of HP-PRRSV (Yeast-GP5) was generated and immune responses to this construct were analyzed in mice. Intestinal mucosal PRRSV-specific sIgA antibody and higher levels of IFN-gamma in spleen CD4+ and CD8+ T cells were induced by oral administration of Yeast-GP5. Additionally, Yeast-GP5 administered subcutaneously evoked vigorous cell-mediated immunity, and PRRSV-specific lymphocyte proliferation and IFN-gamma secretion were detected in the splenocytes of mice. These results suggest that Yeast-GP5 has the potential for use as a vaccine for PRRSV in the future.

Analysis of molecular variation in porcine reproductive and respiratory syndrome virus in China between 2007 and 2012 / 中国病毒学·英文版

In the present study, 89 porcine reproductive and respiratory syndrome virus (PRRSV) isolates in China during 2007 to 2012 were randomly selected from the GenBank genetic sequence database. Evolutionary characteristics of these isolates were analyzed based on the sequences of non-struc-tural protein 2 (Nsp2) and glycoprotein 5 (GP5). The genetic variations of the isolates were also compared with six representative strains. The results showed that a high degree of genetic diversity exists among the PRRSV population in China. Highly pathogenic PRRSV isolates, with a discon-tinuous deletion of a 30 amino acid residue in the Nsp2 region, remained the most dominant virus throughout 2007-2012 in China. Owing to the extensive use of representative vaccine strains, natu-ral recombination events occurred between strains. Three isolates-HH08, DY, and YN-2011-were more closely related to vaccine strains than the other isolates. Both YN-2011 and DY were the evolu-tionary products of recombination events between strains SP and CH-1R. The results of the present study provide useful information for the epidemiology of PRRSV as well as for vaccine development.

Immunosuppression mediated by porcine FcγRⅢin PRRSV infection to PAMS / 中国免疫学杂志

Objective:To study immunosuppression mediated by the porcine FcγRⅢ in porcine reproductive and respiratory syndrome virus ( PRRSV ) infection to pulmonary alveolar macrophages ( PAMS ).Methods: In this study pulmonary alveolar macrophages cells were treated with containing 200 TCID50 PRRSV,lipopolysaccharide (LPS) (100 ng/ml) and purified mouse anti-pig FcγRⅢIgG (550 μg/ml) separately,simultaneously,PAM cells treated with purified mouse anti-pig FcγRⅢIgG (550 μg/ml) was infected by 200 TCID50 PRRSV ,untreated PAM cells as the control group.Each group were post-cultured 12,24,36,48,60,72 h, the cells and the supernatant were collected.The dynamic variation of PRRSV RNA copies in inoculation group were detected by using real-time fluorescence quantitative PCR method.mRNA level of IFN-αand TNF-αin each group were detected by using relative fluorescence quantitative PCR.Results:The result showed that mRNA level of IFN-αwas improved during PRRSV infection to PAMS 12-24 h,and mRNA level of IFN-αwas inhibited during 36-72 h,then mRNA level of IFN-αrecovered normally; mRNA level of TNF-αwas increased slightly post-infection 12-72 h.IFN-αand TNF-αmRNA levels of PAM cells treated with LPS were both up-regu-lated,using the purified mouse anti-pig FcγRⅢ IgG to treat the PAM cells,selective activation of porcine FcγRⅢ in the PAM cells down-regulated significantly mRNA levels of IFN-αand TNF-α.PRRSV infection assay mediated by selective activation FcγRⅢof the PAM cells inhibited antiviral cytokine ( IFN-αand TNF-α) mRNA levels.Conclusion:The results show selective activation of FcγRⅢinhibited significantly mRNA levels of the antiviral cytokine IFN-αand TNF-αof host cells,and innate antiviral immune response to PRRSV infection.

Development of porcine respiratory and reproductive syndrome virus replicon vector for foot-and-mouth disease vaccine

PURPOSE: Foot-and-mouth disease (FMD) is an economically important global animal disease. To control FMD virus (FMDV) outbreaks, a lot of different novel approaches have been attempted. In this study, we proposed a novel porcine reproductive and respiratory syndrome virus (PRRSV) as a replicon vector to express FMDV structural protein. MATERIALS AND METHODS: PRRSV infectious clone (PRRSVK418DM) was used to develop an expression vector through the reverse genetic manipulation of PRRSV; FMDVP12A3C gene of serotype O was synthesized and used for an antigen. MARC-145 cells (African green monkey kidney epithelial cell line) were used for electroporation mediated transfection. The transfection or the expression of P12A3C and N protein of PRRSV was analyzed by either replicon containing PRRSV alone or by co-infection of helper PRRSV. RESULTS: We constructed PRRSVK418DM replicon vector containing FMDVP12A3C, and genome sequences were confirmed by subsequent sequence analysis. In vitro expression of P12A3C and PRRSV N protein was confirmed by immunofluorescence antibody assay using antibodies specific for PRRSV N protein (anti-PRRSV N MAb), FMDV-VP1 (anti-VP1 MAb). CONCLUSION: The results indicate that PRRSV replicon vector can be a promising novel vector system to control FMDV and useful for vaccine development in the future.

Expresión de citocinas en cerdos co-infectados con circovirus porcino tipo 2 y el virus del síndrome respiratorio y reproductivo porcino / Cytokine expression in growing pigs co-infected with porcine circovirus type 2 and porcine reproductive and respiratory syndrome virus

The aim of this work was to quantify porcine circovirus type 2 (PCV2), porcine reproductive and respiratory syndrome virus (PRRSV), as well as cytokine mRNA expression (IL-6, IL-12, TNF-α, and IFN-γ) in superficial inguinal lymph nodes (SILN) of pigs from postweaning multisystemic wasting syndrome (PMWS)-affected and healthy farms. Genetic characterization of detected PCV2 sequences was also carried out. Based on the clinical outcome and the quantification of PCV2 nucleic acid by in situ hybridization and real time PCR, pigs were grouped into three categories: 1) PMWS, pigs with signs of wasting and high viral load in SILN (n = 4); 2) wasted-non-PMWS, pigs with signs of wasting and low to intermediate viral loads in SILN (n = 3); and 3) healthy, pigs with no clinical signs and low viral loads (n = 3). PRRSV was detected in three PMWS affected and two-wasted-non-PMWS pigs. The genetic analysis of PCV2 sequences revealed the presence of two genotypes PCV2a and PCV2b in PMWS-affected farms. Cytokine mRNA expression revealed that PMWS affected pigs had low expression of IFN-γ, whereas wasted-non-PMWS pigs showed higher amounts of IFN-γ. These results suggest that an imbalance in cytokines could be involved in the pathogenesis of PMWS.

Los objetivos de este trabajo fueron la cuantificación de circovirus porcino tipo 2 (PCV2) de virus del síndrome respiratorio y reproductivo porcino (PRRSV), así como la expresión de citocinas (IL-6, IL-12, TNF-α, e IFN-γ) en nódulos linfáticos inguinales superficiales (NLIS) de cerdos afectados por el síndrome de desmedro posdestete (postweaning multisystemic wasting syndrome, PMWS) y en cerdos sanos. Con base en el diagnóstico clínico y a la cuantificación de PCV2 por hibridación in situ y qRT-PCR, los cerdos se distribuyeron en tres grupos: 1) PMWS, cerdos con signos de desmedro y con cargas virales altas en NLIS (n = 4); 2) con desmedro sin PMWS, cerdos con signos de desmedro y cargas virales de intermedias a bajas en NLIS (n = 3); y 3) cerdos sanos, sin signos clínicos y con cargas virales bajas (n = 3). El PRRSV fue detectado en tres de los cerdos afectados por el PMWS y en dos cerdos con desmedro, pero sin el síndrome. Se caracterizaron las secuencias nucleotídicas del ORF2 de los PCV2 encontrados y los análisis genéticos revelaron la presencia de 2 genotipos PCV2a y PCV2b en las granjas afectadas con el PMWS. El perfil de expresión de citocinas mostró una baja expresión de IFN-γ en los cerdos con PMWS, mientras que los cerdos con desmedro sin PMWS mostraron valores elevados de esta citocina. Estos resultados sugieren que existe un desbalance en la producción de citocinas que puede estar implicado en la patogénesis de la enfermedad.

Sequence Analysis and Expression of ORF5 in Korean Isolate of Porcine Reproductive and Respiratory Syndrome Virus

Porcine reproductive and respiratory syndrome virus (PRRSV) is the causative agent of reproductive failure and respiratory disorders in pigs. The viral genome consists of eight overlapping open reading frames (ORFs). ORF5 encodes one of the major glycoproteins and is known as an immunologically important structural protein associated with virus neutralization. The ORF5 gene of the Korean PRRSV isolate, CNV-1, was amplified by reverse transcription-polymerase chain reaction (RT-PCR), cloned and sequenced. The nucleotide and amino acid sequences of CNV-1 ORF5 shared 91% and 83% identity, respectively, with the American isolate (VR2332 strain) and 57% and 49% identity with the European isolate. For the expression and easy purification of ORF5, the cDNA containing the complete ORF5 sequence fused in-frame with sequence encoding glutathione S-transferase (GST) was cloned into a baculovirus transfer vector and transfected into Sf9 cells. The GST-ORF5 fusion protein produced in Sf9 cells was detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting. Sequencing results confirmed that the recombinant baculovirus from Sf9 cells contains the complete ORF5 gene. Further studies in this direction will address whether ORF5 can be a good candidate for a subunit vaccine against PRRSV in Korea.

Application of GP5 Protein to Develop Monoclonal Antibody against Porcine Reproductive and Respiratory Syndrome Virus / 中国病毒学·英文版

In this study,a panel of monoclonal antibodies (mAbs) against Porcine reproductive and respiratory syndrome virus(PRRSV),named as 8C9 and4B4,were produced by fusing SP2/0 myeloma cells and spleen cells of BALB/c mice immunized with the PRRSV (TCID50=5.5),screened by the indirect ELISA and subjected to several limiting dilutions.mAbs were then identified by biological characterization.Among the two fusion cell strains,8C9 belonged to the IgG1 subclass and 4B4 belonged to the IgG2a subclass.The titers in cell culture supernatant and abdomen liquor reached to 1:104and 1:105,respectively.The specificity test indicated that the two cells had specific reactions for the PRRSV and GP5 protein respectively,and no reaction with Classical swine fever virus (CSFV) or Swine vesicular disease virus (SVDV).The molecular weights of the heavy chain and light chain were about 45.0 kDa and 25.0 kDa,respectively.In neutralization activity tests,the results showed that the prepared mAb 4B4 can protect 50% of cells with no CPE in dilution up to 1:512,but mAB 8C9 has no neutralization activities to PRRSV.

Rapid and Sensitive Detection of PRRSV by a Reverse Transcription-Loop-mediated Isothermal Amplification Assay / 中国病毒学·英文版

A real-time monitoring reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay was developed for the sensitive and specific detection of prototypic,prevalent North American porcine reproductive and respiratory syndrome virus (PRRSV)strains.As a higher sensitivity and specificity method than reverse transcription polymerase chain reaction (RT-PCR),the RT-LAMP method only used a turbidimeter,exhibited a detection limit corresponding to a 10-4 dilution of template RNA extracted from 250 μL of 105 of the 50% tissue culture infective dose (TCID50) of PRRSV containing cells,and no cross-reactivity was observed with other related viruses including porcine circovirus type 2,swine influenza virus,porcine rotavirus and classical swine fever virus.From forty-two field samples,33 samples in the RT-LAMP assay was detected positive,whereas three of which were not detected by RT-PCR.Furthermore,in 33 strains of PRRSV,an identical detection rate was observed with the RT-LAMP assay to what were isolated using porcine alveolar macrophages.These findings demonstrated that the RT-LAMP assay has potential clinical applications for the detection of highly pathogenic PRRSV isolates,especially in developing countries.

Indirect ELISA with Recombinant GP5 for Detecting Antibodies to Porcine Reproductive and Respiratory Syndrome Virus / 中国病毒学·英文版

Porcine reproductive and respiratory syndrome is caused by the PRRS virus(PRRSV), which has six structural proteins(GP2, GP3, GP4, GP5, M and N). GP5 and N protein are important targets for serological detection by enzyme-linked immunosorbent assay(ELISA)and other methods. Toward this goal, we developed an indirect ELISA with recombinant GP5 antigens and this method was validated by comparison to the LSI PRRSV-Ab ELISA kit. The results indicated that the optimal concentration of coated recombinant antigen was 0.2 μg/well for a serum dilution of 1:40. The rate of agreement with the LSI PRRSV-Ab kit was 88.7%(266/300). These results support the potential use of recombinant GP5 as an antigen for indirect ELISA to detect PRRSV antibodies in pigs.

Epidemiological characteristics of pulmonary pneumocystosis and concurrent infections in pigs in Jeju Island, Korea

Epidemiological characteristics of swine pulmonary Pneumocystis (P.) carinii and concurrent infections were surveyed on Jeju Island, Korea, within a designated period in 172 pigs submitted from 54 farms to the Department of Veterinary Medicine, Jeju National University. The submitted cases were evaluated by histopathology, immunohistochemistry, PCR/RT-PCR, and bacteriology. P. carinii infection was confirmed in 39 (22.7%) of the 172 pigs. Histopathologically, the lungs had moderate to severe lymphohistioctyic interstitial pneumonia with variable numbers of fungal organisms within lesions. Furthermore, porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus type 2 (PCV-2) co-infection was a common phenomenon (12.8%, 20.5%, and 48.7% were positive for PRRS, PCV-2, or both, respectively, as determined by PCR/RT-PCR). Infection was much more concentrated during winter (December to March) and 53.8% of the infected pigs were 7- to 8-weeks old. In addition, three pigs showed co-infection with bacteria such as Pasteurella multocida and Streptococcus suis. The results of the present study suggest that the secondary P. carinii infection is common following primary viral infection in swine in Korea. They further suggest that co-infection of P. carinii might be enhanced by the virulence of primary pathogens or might have synergistic effects in the pigs with chronic wasting diseases.

Vacunas contra el virus del síndrome reproductivo y respiratorio porcino (PRRSV): escribiendo una historia / Vaccines against porcine reproductive and respiratory syndrome virus (PRRSV): writing a history

The porcine reproductive and respiratory syndrome virus (PRRSV) constitutes one of the most serious problems of the pig industry in the world. It affects pigs of all ages and causes reproductive and respiratory disorders that create great economic losses. These increase due to the rapid spread of the disease and the inefficiency of the commercial vaccines. Modified live and killed vaccines are the two types of commercial vaccines currently available on the market for American and European strains. Although these vaccines can reduce disease symptoms and viremia, they do not prevent infection in any way and cross-presentation is variable against heterologous virus. Furthermore, it has been reported that the vaccine's virus can spread to other susceptible animals. For these reason, many studies focused on the development of new vaccines that include different vectors for the development of DNA vaccines by evaluating various structural proteins. The use of PRRSV infectious clones, as well as the construction of viral chimeras between the vaccine virus and highly infectious virus have also been evaluated. All these strategies have failed to develop an effective vaccine against PRRSV; therefore it remains as a major challenge.

El virus del síndrome reproductivo y respiratorio porcino (PRRSV) constituye uno de los problemas más grandes de la industria porcina. Afecta a cerdos de todas las edades, causa problemas reproductivos y respiratorios que generan pérdidas económicas millonarias. Éstas van en aumento debido a la rápida diseminación del virus y a la poca eficiencia de las vacunas comerciales para su tratamiento. Actualmente existen dos tipos de vacunas contra el PRRSV: una utiliza el virus atenuado y otra el virus inactivado. Existen en el mercado ambos tipos, tanto para cepas americanas como europeas. Aun cuando dichas vacunas disminuyen los síntomas de la enfermedad y la viremia, no evitan la infección y la protección cruzada es variable frente a virus heterólogos. Además, se ha informado que el virus vacunal puede diseminarse a otros animales susceptibles. Por esta razón muchos estudios se han orientado al desarrollo de nuevas vacunas que incluyen diferentes vectores para el desarrollo de vacunas de ADN evaluando varias proteínas estructurales. También se ha evaluado el empleo de clones infecciosos de PRRSV, así como la construcción de quimeras virales entre el virus vacunal y un virus altamente infeccioso. Todas estas estrategias no han logrado desarrollar una vacuna eficaz contra el PRRSV, por lo que dicho propósito sigue siendo un reto muy importante.

Development and characterization of stable cell lines constitutively expressing the porcine reproductive and respiratory syndrome virus nucleocapsid protein

Despite global efforts to control porcine reproductive and respiratory syndrome virus (PRRSV) infection, the virus continues to cause economic problems in the swine industry worldwide. In this study, we attempted to generate and characterize a panel of stable BHK cell lines that constitutively express the nucleocapsid (N) protein of type 1 or type 2 PRRSV. The established BHK cell lines were found to react well with N-specific antibodies as well as the hyperimmune serum of pigs raised against each genotype of PRRSV. Taken together, the data implicate a potential usefulness for the newly generated stable cell lines as a diagnostic reagent for PRRSV serology.

Genetic analysis of ORF5 of recent Korean porcine reproductive and respiratory syndrome viruses (PRRSVs) in viremic sera collected from MLV-vaccinating or non-vaccinating farms

The 23 open reading frame (ORF) 5 sequences of Korean type II porcine reproductive and respiratory syndrome virus (PRRSV) were collected from viremic sera from the (modified live vaccine) MLV-vaccinating and non-vaccinating farms from 2007 to 2008. The samples were phylogenetically analyzed with previous ORF5 sequences, including type I Korean PRRSV, and previously reported or collected sequences from 1997 to 2008. A MN184-like subgroup of type II Korean PRRSV was newly identified in the viremic sera collected from 2007 to 2008. And of the type I PRRSVs, one subgroup had 87.2~88.9% similarity with the Lelystad virus, showing a close relationship with the 27~2003 strain of Spain. The maximum parsimony tree of type II PRRSV from 1997 to 2008 showed that they had evolved to four lineages, subgroups 1, 2, 3 and 4. Most of the recently collected type II PRRSVs belonged to subgroup 4 (48%). The region of three B-cell epitopes and two T-cell epitopes of ORF5 amino acids sequences was considerably different from the MLV in subgroups 3 and 4. In conclusion, the existence of type I PRRSV, which was genetically different from Lelystad virus (Prototype of type I PRRSV), and heterologous type II PRRSVs of viremic pigs detected even in the MLV-vaccinating farms indicated the need for new vaccine approaches for the control of PRRSV in Korea.

Isolation,identification and sequence analysis of the strain JL/07/SW with deletion mutations of PRRSV / 中国兽医学报

One strain of PRRSV was isolated from tissue of piglets died of obvious respiratory syndrome and high fever.It was identified as a strain of American type PRRSV by serological test and gene sequencing.According to American type PRRSV VR-2332,we designed 3 pairs of primers to aim directly at N gene,GP5 gene and variation sequence of NSP2.The results of sequence analysis indicated a discontinuous deletion of 30 amino acids in nonstructural protein 2 (NSP2).N and GP5 gene is conservative relatively.

Genetic Variation Analyses of nsp2 Gene of PRRSV in Ningxia Hui Autonomous Region of China / 中国病毒学·英文版

To gain a better understanding of the genetic diversity and evolution of PRRSV in the Ningxia Hui Nationality Autonomous Region (Ningxia) of China, the nsp2 genes from a series of PRRSV strains collected from the region in 2007 were partially sequenced. These sequences were then analyzed along with the classical strain (ch-la) and two other epidemic strains SD (3) and SD2006. Comparison of the nucleotide sequence with ch-la indicated that nsp2 genes of seventeen Ningxia isolates (NX strain) have deletions of 87 nucleotides. Sequence analysis indicated that homology between the Ningxia strain and ch-la was 60.3%-79.9% in the nucleotide sequence, and homology between the NX strains and SD strains was 80.3%-98.8% in the nucleotide sequence. The nsp2 genes of the seventeen isolates had 74.9%-100% nucleotide sequence identities with each other. This study was undertaken to assess the regional variation of prevalent PRRSV and to establish a sequence database for PRRSV molecular epidemiological studies.