Porcine reproductive and respiratory syndrome virus (PRRSV) continues to be a threat, causing economically significant impacts on the swine industry worldwide. Unfortunately, the traditional control strategies and conventional vaccines fail to provide sustainable disease control, in particular against genetically diverse strains, as they suffer from both antigenic heterogeneity and various immune evasion strategies of PRRSV. In this paper, latest research progress in immunology and immune evasion of PRRSVis summarized to provide a referenc for PRSSV prevention and control as well as the design of new vaccines.
Animals ; Immune Evasion ; Porcine Reproductive and Respiratory Syndrome ; immunology ; virology ; Porcine respiratory and reproductive syndrome virus ; genetics ; immunology ; Swine ; Viral Proteins ; genetics ; immunology

Porcine reproductive and respiratory syndrome virus (PRRSV) non-structural protein 7 (Nsp7) plays an important role in the induction of host humoral immune response and could serve as an ideal antigen for serological genotyping assay for PRRSV based on the significant difference in immunoreactivities of North American (NA) and European (EU) PRRSV Nsp7. In this study, Nsp7 of NA and EU PRRSVwas separately expressed and purified using prokaryotic expression system. The purified recombinant Nsp7 proteins reacted with serum antibodies against corresponding genotype PRRSV in Western blotting. However, nonspecific reaction of whole recombinant Nsp7 with antibodies against another genotype PRRSV was observed, indicating that whole NA PRRSV Nsp7 and EU PRRSV Nsp7 have similar antigenic epitopes and recombinant proteins could not be used for genotyping of antibodies against PRRSV. Based on the analysis of similar antigenic epitopes at the hydrophilic region of NA PRRSV Nsp7 and EU PRRSV Nsp7 by bioinformatics assessment, partial Nsp7 gene region deleted sequences encoding similar antigenic epitopes was constructed by fusion PCR. The recombinant truncated Nsp7 (NA-deltaNsp7 and EU-deltaNsp7, about 43 kDa) was expressed and the molecular weight was about 43 kDa. The results of Western blotting showed that NA-deltaNSP7 and EU-deltaNSP7 could be specifically recognized by positive serum to NA or EU PRRSV individually and nonspecific reaction was eliminated. This study provided a basis for further development of serological genotyping assay for North American and European genotype PRRSV infection.
Animals ; Genotype ; Porcine respiratory and reproductive syndrome virus ; classification ; genetics ; immunology ; Recombinant Proteins ; biosynthesis ; immunology ; Swine ; Viral Nonstructural Proteins ; biosynthesis ; immunology

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.
Animals ; Antibodies, Viral/analysis/immunology ; Blotting, Western/veterinary ; Cell Line ; Cricetinae ; Female ; Genotype ; Nucleocapsid Proteins/genetics/*immunology ; Porcine Reproductive and Respiratory Syndrome/diagnosis/*immunology ; Porcine respiratory and reproductive syndrome virus/genetics/*immunology ; Swine ; Transfection/veterinary

In recent years, mass outbreaks of highly pathogenic (HP) porcine reproductive and respiratory syndrome virus (PRRSV) have spread all over the Chinese swine industry. Based on the first infectious cDNA clone of HP PRRSV strain pJX143 and that of an attenuated PRRSV, pAPRRS, constructed in our group, we constructed several chimeric clones with various substitutions of structural protein genes (ORF4-7) and 3' UTR between attenuated pAPRRS and virulent pJX143.Upon transfection of MA-104 cultured cells, all chimeric constructs pSX12, p5NX12, and p56N12 were rescued. The rescued viruses maintained the similar virological properties, based on the results of the growth curve of the rescued viruses. To test if the chimeric viruses can be used as a vaccine candidate, vSX12 and v56N12 vaccinated pigs were challenged with the HP PRRSV JX143 strain. As a result, the vSX12 vaccinated pigs were all seroconverted by 14-day-post vaccination, while v56N12 vaccinated pigs showed poor antibody response. Upon challenge, the vSX12-vaccinated group showed no signs of clinical PRRS syndrome, and virema period was shorten to 6 days post-challenge. Our results demonstrated that 1) vSX12 chimeric virus is a good vaccine candidate; 2) the virulence determinants of HP PRRSV probably located in coding regions other than ORF3-7 and 3' UTR, as our chimeric viruses were proved to be attenuated.
Animals ; Cloning, Molecular ; Open Reading Frames ; Porcine Reproductive and Respiratory Syndrome ; virology ; Porcine respiratory and reproductive syndrome virus ; genetics ; immunology ; Recombinant Fusion Proteins ; genetics ; immunology ; Recombination, Genetic ; genetics ; Swine ; Vaccines, Attenuated ; immunology ; Viral Envelope Proteins ; Viral Proteins ; biosynthesis ; genetics ; Viral Vaccines ; immunology

The cDNA fragment encoding the truncated GP5 and the full-length M protein of Porcine Reproductive and Respiratory Syndrone Virus (PRRSV) were orderly fused to the downstream of glutathione S-transferase (GST) of pGEX-KG expression vector, resulting in the fusion expression plasmid pKG-56. After transformed into E. coli BL21 (DE3) and induced by IPTG, the results of SDS-PAGE showed that the GST-GP5-M fusion protein was expressed in high level. Western-blot was performed to confirm that the expressed fusion protein could specifically react with antiserum against PRRSV. The fusion protein was further purified and used as an antigen to establish a novel PRRSV ELISA diagnose assay (P56-ELISA). Comparison between P56-ELISA and the abroad kit IDEXX-ELISA showed the two methods had 94.1 percent agreement by detecting 205 serum samples, indicating that the indirect P56-ELISA was specific and sensitive. The correlation between virus neutralization antibody of the infected pigs (not convalescent pigs) and antibody response to the fusion protein GP5-M was further studied. The regression function analysis suggested that there was no significant correlation between ELISA antibody response (OD630 nm) to the fusion protein GP5-M in clinical serum and their specific neutralizing titers.
Animals ; Enzyme-Linked Immunosorbent Assay ; Escherichia coli ; genetics ; metabolism ; Glutathione Transferase ; metabolism ; Open Reading Frames ; Porcine Reproductive and Respiratory Syndrome ; diagnosis ; immunology ; Porcine respiratory and reproductive syndrome virus ; genetics ; immunology ; Recombinant Fusion Proteins ; biosynthesis ; genetics ; Swine ; Viral Envelope Proteins ; biosynthesis ; genetics

During the period from January to December of 2001, a total of 3,391 swine sera were submitted to our laboratory from 256 farms for the diagnosis of porcine reproductive and respiratory syndrome (PRRS). The antibody to porcine reproductive and respiratory syndrome virus (PRRSV) was tested by the indirect immunofluorescent antibody (IFA) test. Of the 256 farms tested, 230 farms (89.8%) were positive for the PRRSV antibody. The overall seroprevalence of the PRRSV antibody was 52.1% (1765/3391). Most of the pigs seemed to be infected with PRRSV at around 50 to 60 days old. The seroprevalence of the antibody became higher with age, and peaked at around 100 days old. More than one-third of the adult pigs, including boars, gilts, and sows, was positive for the PRRSV antibody. The infection of PRRSV was chronic and confined to growers and/or finishers in most farms. However, the antibody was detected in all production phases at some farms.
Age Factors ; Animals ; Antibodies, Viral/blood ; Female ; Fluorescent Antibody Technique, Indirect/veterinary ; Korea/epidemiology ; Male ; Porcine Reproductive and Respiratory Syndrome/diagnosis/epidemiology/*virology ; Porcine respiratory and reproductive syndrome virus/immunology/*isolation &purification ; Seroepidemiologic Studies ; Sex Factors ; Swine

Establishment of recombinant porcine reproductive and respiratory syndrome virus (PRRSV) with co-expression E2 Epitope of Classical Swine Fever virus (CSFV) is a crucial step to develop a genetic engineered vaccine against PRRSV and CSFV. Reverse genetic manipulation could be adopted as a com monly used technique. In this study, we focus on using nonessential regions of NSP2 (aa480-532 and aa508-532) as viral vector to express E2 Epitope of CSFV. A neutralizing epitope of classical swine fever virus (CSFV) E2 protein was inserted into the two nonessential region of nsp2 by the method of mutant PCR, basing on the infectious clone of HuN4-F112 vaccine strain. The co-expressed full-length cDNA clones (psk-HuN4-F112-delta508-532 + E2 and psk-HuN4-F112-delta480-532 + E2) were assembled by cloning and splice of the gene fragments. The completely assembled full-length cDNA clones were confirmed by sequence and Swa I enzyme digestion. Capped RNAs were transcribed in vitro from a full-length cDNA clone of the viral genome and transfected into BHK-21 cells by liposome to acquire the rescued virus. The rescued recombinant viruses were passaged on MARC-145 cells. The successfully rescued viruses were tested by RT-PCR, digestion, and genome sequence. The results showed that these rescued viruses could be distinguished from the parental virus (HuN4-F112) with the mutant genetic marker (Mlu I enzyme site of virual genome at 14 667nt was created by synonymous mutation) and the inserted nsp2 gene region. The results of IFA showed that the inserted E2 epitope could be expressed by the recombinant viruses and the E2 epitope gene was stable during the viral serial passage. The results of plaque assay and viral growth curve showed that the recovery viruses possessed similar characterses of viral growth to those of the parental virus. In summary, the full-length infectious cDNA clones containing the marker gene were constructed and the marker recombinant viruses were rescued. The results suggested that these stable infectious clones could be used as an important tool for development of novel vaccine against PRRSV.
Base Sequence ; Cysteine Endopeptidases ; genetics ; Epitopes ; genetics ; Molecular Sequence Data ; Porcine respiratory and reproductive syndrome virus ; genetics ; Viral Envelope Proteins ; genetics ; immunology ; Viral Vaccines ; immunology

To clone porcine bone marrow stromal antigen-2 (BST-2) gene, construct its recombinant eukaryotic expression plasmid and induce the expression of the fusion antiviral protein, we amplified BST-2 gene by RT-PCR from the total RNA extracted from PK15 cells. The recombinant expression plasmid pcDNA-BST-2 was constructed and then was transfected into HEK293T cells to expresse the BST-2 fusion protein. Western blot and indirect immunofluorescence assay (IFA) were performed, and the biological activity was detected. The results showed that the construction of recombinant plasmid pcDNA-BST-2 was confirmed by restriction enzyme digestion and sequencing. The expressed product had antiviral activity against Vesicular stomatitis virus (VSV), Avian influenza virus (AIV) and Porcine reproductive and respiratory syndrome virus (PRRSV). In conclusion, the research paves the way for further research on bioactivity assayand antiviral medication.
Animals ; Antigens, CD ; genetics ; immunology ; Cell Line ; Chickens ; Cloning, Molecular ; Gene Expression ; Humans ; Influenza in Birds ; immunology ; virology ; Orthomyxoviridae ; physiology ; Porcine Reproductive and Respiratory Syndrome ; immunology ; virology ; Porcine respiratory and reproductive syndrome virus ; physiology ; Swine ; Vesicular Stomatitis ; immunology ; virology ; Vesicular stomatitis Indiana virus ; physiology ; Virus Replication

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.
Animals ; Epitopes, B-Lymphocyte/immunology ; Epitopes, T-Lymphocyte/immunology ; Evolution, Molecular ; Korea ; *Open Reading Frames ; Phylogeny ; Pilot Projects ; Porcine Reproductive and Respiratory Syndrome/blood/genetics/immunology/*virology ; Porcine respiratory and reproductive syndrome virus/*genetics/immunology ; RNA, Viral/chemistry/genetics ; Reverse Transcriptase Polymerase Chain Reaction/veterinary ; Swine ; Viral Vaccines/immunology/standards ; Viremia/genetics/immunology/virology

Pseudorabies virus (PRV), an alpha-herpesvirus, has been used as a vector for live-viral animal vaccines. The recombinant PRV TK- / gE- / GP5+, which expressing GP5 of PRRSV, is developed based on the PRV genetic-depleting vaccine-virus strain, TK- / gE- /LacZ+. However, this strain stimulated poorly the vaccinated animals to produce neutralizing antibodies against PRRSV. In order to develop a booster specific immunized response of the PRV recombinant, the ORF5 gene of PRRSV TK- / gE- / LacZ+ was substituted by a modified ORF5 gene, ORF5m. The resultant recombinant PRV, TK- /gE- / GP5m+, was verified by PCR, Southern blotting and Western blotting. TK- / gE- / GP5m+ and TK- / gE- / GP5+ expressed GP5 proteins were inoculated into balb/c mice to evaluate their immunogenicity. The results demonstrated that the amount of neutralization antibodies and cell-immunity responses induced by TK- / gE- /GP5m+ against PRRSV were higher than that of TK- / gE- / GP5+. This study indicated that the new recombinant PRV expressing the modified GP5m protein is a candidate for the development of bivalent genetic engineering vaccines against PRRSV and PRV.
Animals ; Genetic Vectors ; Herpesvirus 1, Suid ; genetics ; immunology ; Mice ; Mice, Inbred BALB C ; Porcine respiratory and reproductive syndrome virus ; genetics ; immunology ; Recombinant Fusion Proteins ; genetics ; immunology ; Recombinant Proteins ; biosynthesis ; genetics ; immunology ; Swine ; Viral Envelope Proteins ; biosynthesis ; genetics ; Viral Vaccines ; genetics ; immunology