Role of feline ANP32 proteins in regulating polymerase activity of influenza A virus

Recently,increasing natural infection cases and experimental animal challenge studies demonstrated domestic cats are susceptible to multiple subtypes influenza A virus(IAV)infections.Notably,some subtype IAV strains could circulate in domestic cats after cross-species transmission and even infected humans,posing a threat to public health.Host factors related to viral polymerase activity could determine host range of IAV and acidic nuclear phosphoprotein 32(ANP32)is the most important one among them.However,role of cat-derived ANP32 on viral polymerase activity and host range of IAV is still unknown.In the present study,a total of 10 feline ANP32(feANP32)splice variants(including 5 feANP32A,3 feANP32B,and 2 feANP32E)were obtained from domestic cats by RT-PCR.Sequence alignment results demonstrated amino acid deletions and/or insertions occurred among feANP32 variants,but all feANP32 proteins were primarily localized to cell nucleus.Minigenome replication systems for several representative IAV strains were established and the support ability of feANP32 on IAV polymerase activity was estimated.The results indicated that most feANP32A and feANP32B splice variants were able to support all the tested IAV strains,though the support activity of a single feANP32 protein on polymerase activity varied among different IAV strains.In addition,the role of feANP32 in supporting H3N2 canine influenza virus was determined by investigating viral replication in vitro.Collectively,our study systematically investigated the support activity of feANP32 on IAV,providing a clue for further exploring the mechanism of susceptibility of cats to IAV.

Use of a Multiplex RT-PCR Assay for Simultaneous Detection of the North American Genotype Porcine Reproductive and Respiratory Syndrome Virus,Swine Influenza Virus and Japanese Encephalitis Virus

A multiplex reverse transcriptase-polymerase chain reaction(multiplex RT-PCR) assay was developed and subsequently evaluated for its efficacy in the detection of multiple viral infections simultaneously,in swine.Specific primers for each of the 3 RNA viruses,North American genotype porcine reproductive and respiratory syndrome virus,Japanese encephalitis virus,and swine influenza virus,were used in the testing procedure.The assay was shown to be highly sensitive because it could detect as little as 10-5 ng of each of the respective amplicons in a single sample containing a composite of all 3 viruses.The assay was also effective in detecting one or more of the same viruses in various combinations in specimens,including lymph nodes,lungs,spleens,and tonsils,collected from clinically ill pigs and in spleen specimens collected from aborted pig fetuses.The results from the multiplex RT-PCR were confirmed by virus isolation.The relative efficiency(compared to the efficiency of separate assays for each virus) and apparent sensitivity of the multiplex RT-PCR method show that this method has potential for application in routine molecular diagnostic procedures.

Porcine Interleukin-2 Expression in Insect Cells and Its Enhancement of Pig Immunity to Swine Influenza Virus Inactivated Vaccine

Mature porcine interleukin-2 （pIL-2） gene was amplified by PCR from the plasmid pGEM-T-pIL2 and cloned into the baculovirus pFastBacTM Dual vector of the Bac-to-Bac baculovirus expression system under the control of the PH promoter. Recombinant plL-2 （rpIL-2） expressed in Sf9 insect cells was detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunofluorescence assay. Western blot analysis confirmed that the rpIL-2 protein had a molecular mass of 20 kDa, which was larger than the molecular mass of the mature protein predicted based on its peptide sequence. The rpIL-2 protein induced in vitro proliferation of ConA-stimulated porcine splenocytes and enhanced in vivo protective immune responses induced by vaccinating the pigs with inactivated oil emulsion vaccine against swine influenza virus. The results showed that the rpIL-2 expressed in Sf9 insect cells has immunoenhancement effects; the finding lays the foundation for the preparation of a specific recombinant IL-2 protein and the development of a novel immune adjuvant of vaccines against various infectious porcine pathogens to increase the immunoprotective efficacy of vaccines.

Association of swine influenza H1N1 pandemic virus(SIV-H1N1p) with porcine respiratory disease complex in sows from commercial pig farms in Colombia

Porcine respiratory disease complex （PRDC） is a serious health problem that mainly affects growing and finishing pigs. PRDC is caused by a combination of viral and bacterial agents, such as porcine reproductive and respiratory syndrome virus （PRRSV）, swine influenza virus （SIV）, Mycoplasma hyopneumoniae （Myh）, Actinobacillus pleuropneumoniae （APP）, Pasteurella multocida and Porcine circovirus 2 （PCV2）. To characterize the specific role of swine influenza virus in PRDC presentation in Colombia, 11 farms from three major production regions in Colombia were examined in this study. Nasal swabs, bronchial lavage and lung tissue samples were obtained from animals displaying symptoms compatible with SIV. Isolation of SIV was performed in 9-day embryonated chicken eggs or Madin-Darby Canine Kidney （MDCK） cells. Positive isolates, identified via the hemagglutination inhibition test, were further analyzed using PCR. Overall, 7 of the 11 farms were positive for SIV. Notably, sequencing of the gene encoding the hemagglutinin （HA） protein led to grouping of strains into circulating viruses identified during the human outbreak of 2009, classified as pandemic H1N1-2009. Serum samples from 198 gilts and multiparous sows between 2008 and 2009 were obtained to determine antibody presence of APP, Myh, PCV2 and PRRSV in both SIV-H1Nlp-negative and -positive farms, but higher levels were recorded for SIV- HI Nlp-positive farms. Odds ratio （OR） and P values revealed statistically significant differences （p〈0.05） in PRDC presentation in gilts and multiparous sows of farms positive for SIV-HINlp. Our findings indicate that positive farms have increased risk of PRDC presentation, in particular, PCV2, APP and Myh.

Expression of Porcine Reproductive and Respiratory Syndrome Virus ORF7 Gene and Purification and Immunological Activity Analysis of the Recombinant Protein

[Objective] The aim of this study was to realize efficient expression of the porcine reproductive and respiratory syndrome virus （PRRSV） ORF7 gene in genetic engineering bacteria and analYze the immunological activity of the recombinant protein after purification. [ Method] The constructed recombinant expression vector pET-ORF7 was transformed into Escherichia co1BL21 （DE3） and induced by IPTG under the optimal condition. After analysis of SDS-PAGE and Western Blot, the expression products were purified by Ni-NTA His · Bind Resin chrom- atographic column under denaturing condition and renatured by gradient dialysis. Subsequently, the immunological activity of the renatured recombinant protein was detected by Westem Blot and indirect ELISA. [ Result] The recombinant plasmid pET-ORF7 expressed in E. coli successfully, and the fusion protein was in the form of inclusion body. By SDS-PAGE detection, the molecular weight of the expression protein was approximate 33 kD, according with the expectation. Analysis by Bandscan software showed that the expressed fusion protein was about 50% of total bacterial protein of BL21 （DE3）. Wastem Blot and indirect ELISA detection showed that the renatured protein could react with PRRSV positive serum specifically, indicating its good immunological activity. [ Conclusion] This study lays a foundation for the preparation of PRRSV monoclonal antibody and diagnostic kit.

Location of Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus in Tissues of Natural Cases

[ Objective] The aim of this study was to provide a theoretical basis for the prevention and treatment of highly pathogenic porcine reproductive and respiratory syndrome （HP-PRRS）. [Method] Antigen location and histopathological observation in natural cases infected by highly pathogenic porcine reproductive and respiratory syndrome virus （HP-PRRSV） were analyzed by immunohistochemistry and H. E. staining. [Result] The virus antigen mainly existed in epithelial calls, and also a few in mecrophages, lymphocytes and brain nerve cells. [ Conclusion] The cell and tissue tropism of HP-PRRSV strain in natural cases is different from that of previous strains.

Development of Multi-PCR for Differentiation of Vaccine Strain and Field Isolate of Porcine Pseudorabies Virus

Three pairs of primer were designed for amplification of porcine pseudorabies virus （PRV） gB, gE, and TK gene by multiplex PCR （multi-PCR） in order to differentiate vaccine strains from field isolates. Three specific bands were obtained respectively at the expected size, 427 bp （gB gene）, 298 bp （gEgene）, and 208 bp （TKgene）, Then four different gene-deleted vaccines of PRV were detected by multi-PCR. One ex- pected specific band was observed in one of samples, while two bands in the others. As shown by the detection results, the multi-PCR has high sensitivity and specificity and should be applied in pathogen diagnosis and epidemiological investigation in the future.

Analysis on Heredity and Variation of the ORF_5 Gene of Prevalence Strains Porcine Reproductive and Respiratory Syndrome Virus

[ Objective] The aim was to analyze the reason and epidemic trend of PRRSV, and provide theoretical basis for preventing and controlling PRRS. [Methed]According to the sequence of ATCC VR-2332 strain porcine reproductive and respiratory syndrome virus published by the GenBank, the primers were designed and synthesized. ORF5 gene sequences of seven prevalence strains were amplified by RT-PCR. The sequences of ORF5 genes were analyzed by DNAStar and compared with those of ATCC VR-2332, CH-1 a, B J-4, LV-M96262 and MLV vaccine strains, phylogenetic tree among isolates was analyzed. [Result] Analysis of nucleotide sequence showed that the homology was 88.1% - 98.8%, 89.9% -95.2%, 85.6% -98.7% between ORF5 genes of seven prevalence strains and VR-2332, CH-1a, BJ-4, and the homology was 54.7% -56.9% between ORF5 genes and LV. Analysis of amino acid sequence showed that the homology was 88.1% -96.8%, 88.1% - 94.5%, 86.1% -96.5% between ORF5 genes of seven prevalence strains and VR-2332, CH-1a, bBJ-4, the homology was 54.7% -56.2% between the ORF5 genes and LV.[ Conclusion] The variation of prevalence strains was great in the ORF5 gene region, the homology of ORF5 gene sequence was higher and genetic relationship was nearer during prevalence strains in the same region, or was far in different regions.

Influence of Hypericum perforatum Extract on Piglet Infected with Porcine Respiratory and Reproductive Syndrome Virus

To study the influence of Hypericum perforatum extract （HPE） on piglets infected with porcine respiratory and reproductive syndrome virus （PRRSV）, enzyme-labeled immunosorbent assay （ELISA） and cytopathic effect （CPE） were used to determine in vitro whether HPE could induce swine pulmonary alveolar macrophages （PAMs） to secrete IFN-γ, and whether PRRSV titers in PAMs were affected by the levels of HPE-induced IFN-γ. HPE （200 mg·kg-1） was administrated by oral gavage to piglets infected with the PRRSV in vivo to observe whether HPE affected the viremia, lung viral titers, and weight gain of piglets infected with PRRSV. The results showed that HPE was capable of inducing PAMs to produce IFN-γ in a dose dependent manner and HPE pretreatment was capable of significantly reducing PRRSV viral titers in PAMs （P〈 0.01）. Administration of HPE to the PRRSV-infected animals significantly （P〈 0.05） reduced viremia over time as compared with the PRRSV-infected animals. But there was not significant decrease in lung viral titers at day 21 post-infection between the HPE- treated animals and the PRRSV-infected control piglets. There were no significant differences in weight gain over time among the HPE-treatment animals, the normal control, and the HPE control animals. The PRRSV-infected animals caused significant （P〈 0.01） growth retardation as compared with the HPE controls and the normal piglets. It suggested that HPE might be an effective novel therapeutic approach to diminish the PRRSV-induced disease in swine.

Development of an Improved DNA-launched Porcine Reproductive and Respiratory Syndrome Virus Reverse Genetics System

[Objective] This study was to improve the virus replication efficiency of full length infectious cDNA clones by making use of the ribozyme＇s self incision property.[Method] By employing three-step PCR,HDV ribozyme（HdvRz）cDNA was isolated,and cloned into the downstream flanking the genome of the porcine reproductive and respiratory syndrome virus,and into which the bovine growth hormone polyadenylation sequence（BGH）was inserted via enzyme digestion and ligation,yielding pAPRRS-HB.The newly constructed pAPRRS-HB was used to transfect MARC-145 cells,in which the N protein and non-structural protein（nsp2）were determined by indirect immunofluorescence assay after 72 h of expression;meanwhile the virus titer of cell supernatant was tested using TCID50 assay.[Result] pAPRRS-HB containing complete infectious PRRSV cDNA has been successfully developed,and it performed about 10-fold higher virus rescue rate than pAPRRS without the engineered ribozyme element.[Conclusion] The results laid a foundation for revealing the structure and function of PRRSV gene.

Expression of Porcine Interleukin-2 and Porcine Interleukin-6 and Their Adjuvant Effects on Gene Deleted Vaccine of Pseudorabies Virus(TK^-/gG^-/LacZ^+)

Porcine interleukin-2 and porcine interleukin-6 cDNA sequences were cloned into the expressing vectors pET-28a and pGEX-KG respectively. They were expressed in E. coli BL21(DE3)with high-level production. The gene deleted vaccine of pseudorabies virus Ea strain(TK-/gG-/LacZ+)was mixed with the two different purified recombinant proteins each, or both, with the doses of 2, 5 or 10 μg ml-1. Ten groups of pseudorabies negative antibody swines were immuned twice with tested vaccines with different doses, or control vaccine, respectively. The antibody liters of the test groups were detected by neutralization test, and the daily weight gains of swines were calculated and analyzed statistically. In the study, all the neutralizing antibody ti-ters in test groups were higher than the control group, and the recombinant proteins appeared a dose dependent adjuvant effect. The tested vaccines with 2 μg ml-1 pIL-2 and with 10 μg ml-1 pIL-2/pIL-6 got significant and extremely significant differences, compared with the vaccines without pILs. The difference of the daily weight gain indicated the potential positive influence of pIL-2 and pIL-6 on immune protection.

Porcine NF-κB p65 Subunit:Molecular Characterization,Tissue Expression and Transcriptional Profile in Porcine Epidemic Diarrhea Virus-infected IPEC-J2 Cells

The p65 protein is a functional subunit of NF-κB family and exhibits a crucial role in host immune and inflammatory responses,apoptosis and tumor proliferation if improperly-regulated.Given its ubiquitous association with nearly all the animal cells and its pleotropic functions,the gene encoding NF-κB p65 subunit was cloned and sequenced from porcine kidney(PK-15)cells.The gene was 1662 bp in length,encoded a 553-amino acid protein and contained the prototypical NF-κB functional domains.Real-time quantitative RT-PCR and Western blot were used to characterize the transcription and expression levels of the p65 in different pig tissues.The results indicated that the p65 gene and protein were both broadly expressed in pig tissues,but most highly expressed in the intestine-associated lymph nodes and the lungs.To localize the recombinant protein in intestinal porcine epithelial cells(IPEC-J2),the gene was subcloned into the vector pEGFP(pEGFP-p65).Using fluorescence microscopy,the protein was found confined to the cytoplasm in normal cells;however,during porcine epidemic diarrhea virus(PEDV)infection,mRNA and protein expression were significantly up-regulated and the protein exhibited an overt tendency for nuclear translocalization consistent with a regulatory role in antiviral innate immunity.

A Review on 2009 Influenza A Virus

[Objective] The paper was to introduce the research progress of 2009 influenza A virus. [Method] 2009 influenza A virus was introduced from the aspects of classification and host, virology, molecular characteristics and vaccine. [Result] A novel influenza A/H1N1 virus emerged in early April 2009 quickly spread worldwide through human-to-human transmission. The virus contained a group of novel gene segments, the nearest known precursor was the virus found in swine. The virus appeared to retain the potential to infect swine again and thus continued reassort with swine viruses. All registered 2009 influenza A vaccines were tested for safety and immunogenicity in clinical trials on human volunteers, and all vaccines were found to be safe, single dose of vaccine could cause protective antibody responses. [Conclusion] The paper provided basis for further study on 2009 influenza A virus.

Porcine reproductive and respiratory syndrome virus vaccines: Immunogenicity, efficacy and safety aspects

Porcine reproductive and respiratory syndrome virus(PRRSV) infection is the leading cause of economic casualty in swine industry worldwide. The virus can cause reproductive failure, respiratory disease, and growth retardation in the pigs. This review deals with current status of commercial PRRS vaccines presently used to control PRRS. The review focuses on the immunogenicity, protective efficacy and safety aspects of the vaccines. Commercial PRRS modified-live virus(MLV) vaccine elicits delayed humoral and cell-mediated immune responses following vaccination. The vaccine confers late but effective protection against genetically homologous PRRSV, and partial protection against genetically heterologous virus. The MLV vaccine is of concern for its safety as the vaccine virus can revert to virulence and cause diseases. PRRS killed virus(KV) vaccine, on the other hand, is safe but confers limited protection against either homologous or heterologous virus. The KV vaccine yet helps reduce disease severity when administered to the PRRSV-infected pigs. Although efforts have been made to improve the immunogenicity, ef-ficacy and safety of PRRS vaccines, a better vaccine is still needed in order to protect against PRRSV.

Vaccination of Plasmid DNA Encoding Somatostatin Gene Fused with GP5 Gene of Porcine Reproductive and Respiratory Syndrome Virus Induces Anti-GP5 Antibodies and Promotes Growth Performance in Immunized Pigs

Somatostatin （SS） is a hormone that inhibits the secretion of growth hormone. Immunization against SS can promote the growth of animals. This paper described the effects of DNA immunization on the growth and antibody response in mice and pigs immunized with a plasmid DNA encoding SS fused with GP5 of porcine reproductive and respiratory syndrome virus （PRRSV）. A fragment of 180 bp encoding partial SS gene was amplified by PCR from the genomic DNA of peripheral blood mononuclear cells of pigs, and cloned as a fusion gene with PRRSV GP5 in plasmid pISGRTK3. Three times of immunization with the resulting plasmid pISG-SS/GP5 induced anti-GP5 antibodies in BALB/c mice and pigs, as demonstrated by GP5-specific ELISA and immunoblotting. Compared with pigs immunized with empty vector pISGRTK3, the growth performance of pigs immunized with pISG-SS/GP5 was increased by 11.1% on the 13th week after the last vaccination. The results indicated the plasmid DNA encoding SS and PRRSV GP5 fusion gene elicited anti-GP5 antibodies and improved the growth performance of immunized pigs.

Structural basis for dsRNA recognition by NS1 protein of influenza A virus

Influenza A viruses are important human pathogens causing periodic pandemic threats. Nonstructural protein 1 （NS1） protein of influenza A virus （NS1A） shields the virus against host defense. Here, we report the crystal structure of NS1A RNA-binding domain （RBD） bound to a double-stranded RNA （dsRNA） at 1.7A. NS1A RBD forms a homodimer to recognize the major groove of A-form dsRNA in a length-independent mode by its conserved concave surface formed by dimeric anti-parallel a-helices, dsRNA is anchored by a pair of invariable arginines （Arg38） from both monomers by extensive hydrogen bonds. In accordance with the structural observation, isothermal titration calorimetry assay shows that the unique Arg38-Arg38 pair and two Arg35-Arg46 pairs are crucial for dsRNA binding, and that Ser42 and Thr49 are also important for dsRNA binding. Agrobacterium co-infiltration assay further supports that the unique Arg38 pair plays important roles in dsRNA binding in vivo.

Evaluation of the Pathogenicity of a Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus Variant in Piglets

Since May 2006,a highly pathogenic porcine reproductive and respiratory syndrome virus （HP-PRRSV） variant characterized by 30 amino acids deletion within its NSP2-coding region emerged and caused extensive economic losses to China＇s pig industry.To investigate the in vivo pathogenicity and immune responses of the newly emerging PRRSV,3 groups of 60-d-old conventional piglets were inoculated intranasally with a representative strain of the HP-PRRSV variant HuN4 with 3 different infection doses （3×103-3×105 TCID50）.The results revealed that the virus variant caused severe disease in piglets and the significant clinical characteristics consisted of persistently high fever （41.0-41.9oC） and high morbidity and mortality （60-100%）,the marked clinical signs of PRRS and severe histopathogenic damages in multiple organs.It induced rapid and intense humoral immune responses and seroconversion was detected in most infected pigs at 7 d post-infection （DPI）.The virus vigorously replicated in vivo and the highest virus average titer was 9.7 log copies mL-1 serum at 7 DPI.Elevated levels of IFN-g and IL-10 cytokine production in serum in this study were also observed.Taken together,our results demonstrated that the HP-PRRSV variant HuN4 strain is highly pathogenic for piglets and suitable to be a reference strain of highly virulent PRRSV for evaluating the efficacy of the new vaccines.

Possible Impact of Global Warming on the Evolution of Hemagglutinins from Influenza A Viruses

Objective To determine if global warming has an impact on the evolution of hemagglutinins from influenza A viruses, because both global warming and influenza pandemics/epidemics threaten the world. Methods 4 706 hemagglutinins from influenza A viruses sampled from 1956 to 2009 were converted to a time‐series to show their evolutionary process and compared with the global, northern hemisphere and southern hemisphere temperatures, to determine if their trends run in similar or opposite directions. Point‐to‐point comparisons between temperature and quantified hemagglutinins were performed for all species and for the major prevailing species. Results The comparisons show that the trends for both hemagglutinin evolution and temperature change run in a similar direction. Conclusion Global warming has a consistent and progressive impact on the hemagglutinin evolution of influenza A viruses.

Molecular Characterization of Avian-like H1N1 Swine Influenza A Viruses Isolated in Eastern China, 2011

Currently, three predominant subtypes of influenza virus are prevalent in pig populations worldwide： H1N1, H3N2, and H1N2. European avian-Hke H1N1 viruses, which were initially detected in European pig populations in 1979, have been circulating in pigs in eastern China since 2007. In this study, six influenza A viruses were isolated from 60 swine lung samples collected from January to April 2011 in eastern China. Based on whole genome sequencing, molecular characteristics of two isolates were determined. Phylogenetic analysis showed the eight genes of the two isolates were closely related to those of the avian-like H1N1 viruses circulating in pig populations, especially similar to those found in China. Four potential glycosylation sites were observed at positions 13, 26, 198, 277 in the HA1 proteins of the two isolates. Due to the presence of a stop codon at codon 12, the isolates contained truncated PB1-F2 proteins. In this study, the isolates contained 591Q, 627E and 701N in the polymerase subunit PB2, which had been shown to be determinants of virulence and host adaptation. The isolates also had a D rather than E at position 92 of the NS1, a marker of mammalian adaptation. Both isolates contained the GPKV motif at the PDZ ligand domain of the 3＇ end of the NS1, a characteristic marker of the European avian-like swine viruses since about 1999, which is distinct from those of avian, human and classical swine viruses. The M2 proteins of the isolates have the mutation （S31N）, a characteristic marker of the European avian-like swine viruses since about 1987, which may confer resistance to amantadine and rimantadine antivirals. Our findings further emphasize the importance of surveillance on the genetic diversity of influenza A viruses in pigs, and raise more concerns about the occurrence of cross-species transmission events.

Porcine Parvovirus Inducing Autophagy to Benefit Its Replication

Porcine parvovirus(PPV) is one of the major causes of reproductive failure in pigs, which poses a great threat to the pig breeding industry and results in tremendous economic losses worldwide. Autophagy is the biological process of cell self-defense and self-protection. Despite many viruses can cause cell autophagy, when they enter cell or copied, the relationship between autophagy and PPV infection has not been reported. In this study, impact of autophagy after swine testicular(ST) cells infected by PPV was studied. Autophagy was demonstrated by the effective replication of PPV through transmission electron microscopy, immunofluorescence and western blot analysis. Moreover, autophagy was confirmed to benefit PPV replication by real-time fluorescence quantitative PCR and determination of median tissue culture infective dose(TCID). For the first time, the complex interaction between PPV infection and autophagy was explored in this study. It indicated that PPV could induce autophagy in ST cells, which in turn facilitated its own replication, which might be one of the mechanisms of the virus infection. These findings could facilitate the study of the pathogenesis of PPV infection and provide new insight into the development of effective therapeutic strategies.