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.

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 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.

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.

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.

A direct real-time polymerase chain reaction assay for rapid high-throughput detection of highly pathogenic North American porcine reproductive and respiratory syndrome virus in China without RNA purification

Background： Porcine reproductive and respiratory syndrome virus （PRRSV）, and particularly its highly pathogenic genotype （HP-PRRSV）, have caused massive economic losses to the global swine industry. Results： To rapidly identify HP-PRRSV, we developed a direct reaL-time reverse transcription polymerase chain reaction method （dRT-PCR） that could detect the virus from serum specimen without the need of RNA purification Our dRT-PCR assay can be completed in 1.5 h from when a sample is received to obtaining a result. Additionally, the sensitivity of dRT-PCR matched that of conventional reverse transcription PCR （cRT-PCR） that used purified RNA The lowest detection limit of HP-PRRSV was 6.3 TCIDs0 using dRT-PCR. We applied dRT-PCR assay to 144 field samples and the results showed strong consistency with those obtained by cRT-PCR. Moreover, the dRT-PCR method was able to tolerate 5-20% （v/v） serum. Conclusions： Our dRT-PCR assay allows for easier, faster, more cost-effective and higher throughput detection of HP-PRRSV compared with cRT-PCR methods. To the best of our knowledge, this is the first report to describe a real-time RT-PCR assay capable of detecting PRRSV in crude serum samples without the requirement for purifying RNA. We believe our approach has a great potential for application to other RNA viruses.

Application of GP5 Protein to Develop Monoclonal Antibody against Porcine Reproductive and Respiratory Syndrome Virus

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.

Characterization of Porcine Reproductive and Respiratory Syndrome Virus Deletion Mutant

The genome of the isolate of porcine reproductive and respiratory syndrome virus （PRRSV） from China, designated HPBEDV, was sequenced and analyzed. The size of the genome of HPBEDV was 15 334 nucleotides （nt）. Comparative analysis of HPBEDV with the genomic sequences of the domestic and other isolates （JXA 1, HUN4, CH-1 a, B J-4, VR2332, and LV） revealed that HPBEDV shared 98.4, 98.0, 89.0, 88.7, and 88.6% identity with the American strain JXA1, HUN4, CH- 1a, BJ-4, and VR2332, respectively, but only 54.7% identity with the European reference strain Lelystad virus. The NSP2 gene had 2 850 nt and encoded 950 amino acids （aa）, with two discontiguous deletions of 1 aa and 29 aa at positions 482 and 534-562, respectively, relative to VR-2332. Also, phylogenetic analysis with the published PRRSV genomic sequences indicated that the newly emerging isolate form a clade with the VR-2332 isolates. Therefore, HPBEDV was a novel strain with deletions in NSP2 gene.

Analysis of molecular variation in porcine reproductive and respiratory syndrome virus in China between 2007 and 2012

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.

Molecular Characterization of a Highly Pathogenetic Porcine Reproductive and Respiratory Syndrome Virus Variant in Hubei, China

Porcine reproductive and respiratory syndrome virus (PRRSV) has been recognized as one of the most important pathogens of pigs throughout the world. In 2006, more than 10 provinces of China have experienced an epizootic outbreak of pig diseases characterized by high fever, reddened skin and high morbidity and mortality. From June 2006 to April 2007, we have investigated some clinical samples in Hubei province by RT-PCR and cloned several major genes, N, GP5 and NSP2 gene, shown in this study. Phylogenetic analysis of these genes revealed that the highly pathogenic PRRSV variant, ZB, was responsible for 2006 emergent outbreak of pig disease in Hubei province similar with those variants isolated from other provinces in China in 2006, and belongs to the NA-type PRRSV. In the PRRSV variants, the N and GP5 shear about 90% identity with prototypic ATCC VR-2332 and some typical NA-type Chinese isolates, except the 2850bp NSP2 gene (only shares 65% identity with ATCC VR-2332). But they all shear more than and 97% identity with other highly pathogenetic Chinese PRRSV strains. Additionally, there are extensive amino acid (aa) mutations in the GP5 protein and 2 deletions in the Nsp2 protein when compared with the previous isolates. Most of the variants found in 2006 epizootic outbreak of pig diseases in China were the farthest variants from the typical NA-type PRRSV in phylogenetic distance, and these diversities may be responsible for the differences in the pathogenicity observed between these variants and original Chinese PRRSV strains.

Identification of the strain-specifically truncated nonstructural protein 10 of porcine reproductive and respiratory syndrome virus in infected cells

The nonstructural protein 10（nsp10） of porcine reproductive and respiratory syndrome virus（PRRSV） encodes for helicase which plays a vital role in viral replication. In the present study, a truncated form of nsp10, termed nsp10 a, was found in PRRSV-infected cells and the production of nsp10 a was strain-specific. Mass spectrometric analysis and deletion mutagenesis indicated that nsp10 a may be short of about 70 amino acids in the N terminus of nsp10. Further studies by rescuing recombinant viruses showed that the Glu-69 in nsp10 was the key amino acid for nsp10 a production. Finally, we demonstrated that nsp10 a exerted little influence on the growth kinetics of PRRSV in vitro.

Generation of Monoclonal Antibody to Porcine Reproductive and Respiratory Syndrome Virus GP4 Protein and Identification of Its Minic Epitopes

Porcine reproductive and respiratory syndrome virus(PRRSV)GP4 protein was prokaryotically expressed,and used as an antigen to immunize six-week-old BALB/c female mice.With conventional cell fusion method,an anti-PRRSV GP4 protein monoclonal antibody(Mab)5F12 was successfully prepared.It was identified as IgG2b subclass and had better stability and specificity,which not only responded with recombinant PRRSV GP4 protein,but also with PRRSV.Phage display technique had varieties of applications,in particular,the identification of key antigen epitopes for the development of therapeutic and diagnostic reagents and vaccines.In this study,Mab-5F12 was used as the target for biopanning a 12-mer phage random peptide library.After four rounds of biopanning,two phage-displayed peptides,named P-A and P-G(AKFEVCSPVVLG and GVNQENMLHFSF)were identified that recognized Mab-5F12 specifically.Sequence analysis showed that one or more of the peptides exhibited partial sequence similarity to the native GP4 protein sequence,which corresponded to 69-80 and 84-95 aa segments of the HP-PRRSV GP4 protein.Furthermore,real-time quantitative RT-PCR and indirect immunofluorescence assay indicated consistently the abilities of P-A and P-G to block viral infection in Marc-145 cells and they could function as antiviral agents for PRRSV.

Attenuation of Virulent Porcine Reproductive and Respiratory Syndrome Virus Strain CH-1a and Genetic Variation of ORF5 Gene

To develop a modified live vaccine （MLV） against porcine reproductive and respiratory syndrome virus （PRRSV）, virulent CH-Ia strain was attenuated by serial passages up to 130 passage （P130） in Marc-145 cells. The virulence and immune efficacy of the attenuated CH-1 a were evaluated in pigs. The results showed that animals inoculated with P130 did not develop any clinical sign of the disease, but produced rapid and effective humoral immune responses against PRRSV challenge, indicating that attenuated CH-1 a P 130 is the candidate as the effective vaccine against PRRSV. To define the potential mutations in the attenuated CH-la genome, we sequenced and analyzed the ORF5 gene of CH-la strain of different passages （P39, P55, P65, P70, P85, P100, P115, P120, P125, and P130） and found that three mutations （C5Y, H38Q and L146Q） which may be related with the attenuation of CH-la. In addition, we also found a unique restriction enzyme site （TspEI） in the ORF5 gene of attenuated CH-la, which can be used as a genetic marker to distinguish original and attenuated CH- 1 a.

Review for Porcine Reproductive and Respiratory Syndrome Virus

Abstract Porcine reproductive and respiratory syndrome(PRRS)is the severest disease of pigs worldwide,caused by a highly genetically diverse RNA virus,called Porcine reproductive and respiratory syndrome virus(PRRSV).The research summarized the genome characteristics of PRRSV particles and the most updated knowledge of structure protein function,and introduced the intellectual of PRRSV transmission and host immune response,which is very important for prevention and control for PRRS.A report showed that mass vaccination can stabilize the immunity of the entire herd,and this is the first required step for a PRRS eradication plan.However,the attenuated live vaccines may not achieve a valid prevention.The final goal of the EU project is to develop new generation,efficacious and safe maker vaccines that can be adapted to temporary changes and geographical differences.Robinson reported that broadly antibodies could neutralize all rapidly evolving typeⅠand typeⅡviruses,while further studies are expected to elucidate mechanisms of neutralizing antibody production and maturation and to investigate conserved epitope targets of cross-neutralization in this rapidly evolving virus.

Generation and Immunogenicity of a Recombinant Adenovirus Co-Expressing the E2 Protein of Classical Swine Fever Virus and the GP5 Protein of Porcine Reproduction and Respiratory Syndrome Virus

Classical swine fever （CSF） and porcine reproduction and respiratory syndrome （PRRS） are both economically important, highly contagious diseases of swine worldwide. To develop an effective vaccine to control these two diseases, we constructed a recombinant adenovirus rAdV-GP52AE2, using a replication-defective human adenovirus serotype 5 as a delivery vector, to co-express the GP5 protein of highly pathogenic porcine reproduction and respiratory syndrome virus （PRRSV） and the E2 protein of classical swine fever virus （CSFV）. Foot-and-mouth disease virus （FMDV） 2A peptide was used as a linker between the GP5 and E2 proteins to allow automatic self-cleavage of the polyprotein. The GP5 and E2 genes were expressed as demonstrated by immunofluorescence assay and Western blotting. Immunization of mice resulted in a CSFV-neutralizing antibody titer of 1：128 and a PRRSV-neutralizing antibody titer of 1：16. The lymphoproliferative responses were detected by Cell Counting Kit-8 assay and the stimulation index of CFSV-specific and PRRSV-specific lymphocytes in the rAdV-GP52AE2 group was significantly higher than that in the negative control group. The results show that rAdV-GP52AE2 can induce both effective humoral and cell-mediated immune responses in mice. The protective efficacy of the recombinant virus against CSF was evaluated in immunized rabbits, which were protected from fever induced by challenge with C-strain. Our study provides supporting evidence for the use of FMDV 2A to develop a bivalent genetically-engineered vaccine.

miR-204 suppresses porcine reproductive and respiratory syndrome virus(PRRSV)replication via inhibiting LC3B-mediated autophagy

Porcine reproductive and respiratory syndrome(PRRS)caused by PRRS virus(PRRSV)has been regarded as a persistent challenge for the swine farms worldwide.microRNAs(miRNAs)play key roles in regulating almost every important biological process,including virus-host interaction.In this study,we found that miR-204 was highly expressed in cells that were not permissive to PRRSV infection compared with cells susceptible to PRRSV infection.Subsequently,we demonstrated that overexpression of miR-204 significantly inhibited PRRSV replication in porcine alveolar macrophages(PAMs).Through bioinformatic analysis,we found that there existed a potential binding site of miR-204 on the 30UTR of microtubule associated protein 1 light chain 3B(MAP1LC3B,LC3B),a hallmark of autophagy.Applying experiments including luciferase reporter assay and UV cross-linking and immunoprecipitation(CLIP)assay,we demonstrated that miR-204 directly targeted LC3B,thereby downregulating autophagy.Meanwhile,we investigated the interplay between autophagy and PRRSV replication in PAMs,confirming that PRRSV infection induces autophagy,which in turn facilitates viral replication.Overall,we verify that miR-204 suppresses PRRSV replication via inhibiting LC3B-mediated autophagy in PAMs.These findings will provide a novel potential approach for us to develop antiviral therapeutic agents and controlling measures for future PRRSV outbreaks.

Identification of Nonstructural Protein 8 as the N-Terminus of the RNA-Dependent RNA Polymerase of Porcine Reproductive and Respiratory Syndrome Virus

Porcine reproductive and respiratory syndrome virus (PRRSV) is a member within the family Arteriviridae of the order Nidovirales. Replication of this positive-stranded RNA virus within the host cell involves expression of viral replicase proteins encoded by two ORFs, namely ORF1 a and ORF1 b. In particular, translation of ORF1 b depends on a-1-ribosomal frameshift strategy. Thus, nonstructural protein 9 (nsp9), the first protein within ORF1 b that specifies the function of the viral RNA-dependent RNA polymerase, is expressed as the C-terminal extension of nsp8, a small nsp that is encoded by ORF1 a. However, it has remained unclear whether the mature form of nsp9 in virus-infected cells still retains nsp8,addressing which is clearly critical to understand the biological function of nsp9. By taking advantage of specific antibodies to both nsp8 and nsp9, we report the following findings. (1) In infected cells, PRRSV nsp9 was identified as a major product with a size between 72 and 95 k Da (72–95 KDa form), which exhibited the similar mobility on the gel to the in vitro expressed nsp8–9 ORF1 b, but not the ORF1 b-coded portion (nsp9 ORF1 b). (2) The antibodies to nsp8, but not to nsp7 or nsp10, could detect a major product that had the similar mobility to the 72–95 KDa form of nsp9. Moreover, nsp9 could be co-immunoprecipitated by antibodies to nsp8, and vice versa. (3) Neither nsp4 nor nsp2 PLP2 was able to cleave nsp8–nsp9 in vitro. Together, our studies provide experimental evidence to suggest that nsp8 is an N-terminal extension of nsp9.Our findings here paves way for further charactering the biological function of PRRSV nsp9.

Nsp2 and GP5-M of Porcine Reproductive and Respiratory Syndrome Virus Contribute to Targets for Neutralizing Antibodies

Porcine reproductive and respiratory syndrome virus(PRRSV)is characterized by its genetic variation and limited cross protection among heterologous strains.Even though several viral structural proteins have been regarded as inducers of neutralizing antibodies(NAs)against PRRSV,the mechanism underlying limited cross-neutralization among heterologous strains is still controversial.In the present study,examinations of NA cross reaction between a highly pathogenic PRRSV(HP-PRRSV)strain,JXwn06,and a low pathogenic PRRSV(LP-PRRSV)strain,HB-1/3.9,were conducted with viral neutralization assays in MARC-145 cells.None of the JXwn06-hyperimmuned pigs’sera could neutralize HB-1/3.9 in vitro and vice versa.To address the genetic variation between these two viruses that are associated with limited crossneutralization,chimeric viruses with coding regions swapped between these two strains were constructed.Viral neutralization assays indicated that variations in nonstructural protein 2(nsp2)and structural proteins together contribute to weak cross-neutralization activity between JXwn06 and HB-1/3.9.Furthermore,we substituted the nsp2-,glycoprotein2(GP2)-,GP3-,and GP4-coding regions together,or nsp2-,GP5-,and membrane(M)protein-coding regions simultaneously between these two viruses to construct chimeric viruses to test cross-neutralization reactivity with hyperimmunized sera induced by their parental viruses.The results indicated that the swapped nsp2 and GP5-M viruses increased the neutralization reactivity with the donor strain antisera in MARC-145 cells.Taken together,these results show that variations in nsp2 and GP5-M correlate with the limited neutralization reactivity between the heterologous strains HP-PRRSV JXwn06 and LP-PRRSV HB-1/3.9.

Cellular membrane cholesterol is required for porcine reproductive and respiratory syndrome virus entry and release in MARC-145 cells

Cholesterol represents one of the key constituents of small,dynamic,sterol-and sphingolipid-enriched domains on the plasma membrane.It has been reported that many viruses depend on plasma membrane cholesterol for efficient infection.In this study,the role of the plasma membrane cholesterol in porcine reproductive and respiratory syndrome virus(PRRSV) infection of MARC-145 cells was investigated.Pretreatment of MARC-145 cells with methyl-β-cyclodextrin(MβCD),a drug used to deplete cholesterol from cellular membrane,significantly reduced PRRSV infection in a dose-dependent manner.This inhibition was partially reversed by supplementing exogenous cholesterol following MβCD treatment,suggesting that the inhibition of PRRSV infection was specifically mediated by removal of cellular cholesterol.Further detailed studies showed that depletion of cellular membrane cholesterol significantly inhibited virus entry,especially virus attachment and release.These results indicate that the presence of cholesterol in the cellular membrane is a key component of PRRSV infection.

Identification of Porcine Reproductive and Respiratory Syndrome Virus Inhibitors Through an Oriented Screening on Natural Products

Porcine reproductive and respiratory syndrome（PRRS） caused by porcine reproductive and respiratory syndrome virus（PRRSV） is one of the most infectious diseases in the swine industry worldwide, causing big eco- nomic losses. Vaccines are major weapons against PRRSV, however, current available vaccines have several limita- tions. Developing chemical drugs as alternatives is required. On the basis of traditional medical knowledge, we pur- posely selected 15 natural products originated from Chinese herbs with anti-infectious effects. Their antiviral activi- ties were evaluated by PRRSV-indueed cytopathic effect（CPE） on MARC-145 cells and reverse transcription poly- merase chain reaction（RT-PCR） assay. Compounds ethoxysanguinarine（EOSG） and atractylodinol were found to be the hits which could significantly reduce PRRSV-associated CPE with 50% inhibited concentration（ICso） values of 7.9 and 39.4 ~tmol/L, respectively. Meanwhile, compounds ethoxysanguinarine and atractylodinol significantly de- creased mRNA expression of ORF7 gene in a dose-dependent manner. Study results suggest that compounds ethoxy- sanguinarine and atractylodinol may be useful anti-PRRSV drugs for swine industry or the hits for further lead opti- mization.