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.

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.

Genetic analysis of reproductive performance in sows during porcine reproductive and respiratory syndrome(PRRS)and porcine epidemic diarrhea(PED)outbreaks

Background: Porcine reproductive and respiratory syndrome(PRRS) is one of the most infectious swine diseases in the world, resulting in over 600 million dollars of economic loss in the USA alone. More recently, the USA swine industry has been having additional major economic losses due to the spread of porcine epidemic diarrhea(PED).However, information regarding the amount of genetic variation for response to diseases in reproductive sows is still very limited. The objectives of this study were to identify periods of infection with of PRRS virus(PRRSV) and/or PED virus(PEDV), and to estimate the impact their impact on the phenotypic and genetic reproductive performance of commercial sows.Results: Disease(PRRS or PED) was significant(P < 0.05) for all traits analyzed except for total piglets born.Heritability estimates for traits during Clean(without any disease), PRRS, and PED ranged from 0.01(number of mummies;Clean and PED) to 0.41(abortion;PED). Genetic correlations between traits within disease statuses ranged from-0.99(proportion born dead with number weaned;PRRS) to 0.99(number born dead with born alive;Clean). Within trait, between disease statuses, estimates ranged from-0.17(number weaned between PRRS and PED) to 0.99(abortion between Clean and PRRS).Conclusion: Results indicate that selection for improved performance during PRRS and PED in commercial sows is possible and would not negatively impact performance in Clean environments.

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.

Diagnosis of Mixed Infection of Classical Swine Fever Virus and Porcine Reproductive and Respiratory Syndrome Virus and Pathogenic Characteristics

[ Objective] To diagnose swine diseases caused by CSFV （ Classical swine fever virus）, PRRSV （ Porcine reproductive and respiratory syndrome virus） and PRV （Pseudo-rabies virus） and analyze the pathogenic characteristics. [ Methodl The tissues and viscera of the diseased swine were collected from a hoggery in Fujian Province. DNA and RNA were extracted for PCR amplification and sequencing. ELISA method was used to determine CSFV, PRRSV and PRV infection. [ Result] The sequencing analysis and ELISA results showed that the mixed infection was caused by CSFV, PRRSV and PRV. [ Conclusion] The swine epidemic situation was mainly caused by CSFV and PRRSV.

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.

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.

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.

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.

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.

The C/EBPβ-Dependent Induction of TFDP2 Facilitates Porcine Reproductive and Respiratory Syndrome Virus Proliferation

Porcine reproductive and respiratory syndrome(PRRS) is an important infectious disease caused by porcine reproductive and respiratory syndrome virus(PRRSV), leading to significant economic losses in swine industry worldwide. Although several studies have shown that PRRSV can affect the cell cycle of infected cells, it is still unclear how it manipulates the cell cycle to facilitate its proliferation. In this study, we analyzed the mRNA expression profiles of transcription factors in PRRSV-infected 3D4/21 cells by RNA-sequencing. The result shows that the expression of transcription factor DP2(TFDP2) is remarkably upregulated in PRRSV-infected cells. Further studies show that TFDP2 contributes to PRRSV proliferation and the PRRSV nucleocapsid(N) protein induces TFDP2 expression by activating C/EBPb. TFDP2 positively regulates cyclin A expression and triggers a less proportion of cells in the S phase, which contributes to PRRSV proliferation. This study proposes a novel mechanism by which PRRSV utilizes host protein to regulate the cell cycle to favor its infection. Findings from this study will help us for a better understanding of PRRSV pathogenesis.

Over-expression of CD163, CD169, and CD151 is not sufficient to improve the susceptibility to porcine reproductive and respiratory syndrome virus infection in transgenic mice

Porcine reproductive and respiratory syndrome virus(PRRSV)is a major pathogen that causes reproductive failure and respiratory disease in pigs,resulting in devastating economic losses worldwide[1].Porcine alveolar macrophages(PAMs)are the primary target cells of PRRSV[2],and the putative receptors,including CD163,CD169,and CD151,play key roles during infection[3–6].However,the understanding of PRRSV infection and pathogenesis is

Visualizing the Transport of Porcine Reproductive and Respiratory Syndrome Virus in Live Cells by Quantum Dots-Based Single Virus Tracking

Quantum dots(QDs)-based single particle analysis technique enables real-time tracking of the viral infection in live cells with great sensitivity over a long period of time.The porcine reproductive and respiratory syndrome virus(PRRSV)is a small virus with the virion size of 40–60 nm which causes great economic losses to the swine industry worldwide.A clear understanding of the viral infection mechanism is essential for the development of effective antiviral strategies.In this study,we labeled the PRRSV with QDs using the streptavidin–biotin labeling system and monitored the viral infection process in live cells.Our results indicated that the labeling method had negligible effect on viral infectivity.We also observed that prior to the entry,PRRSV vibrated on the plasma membrane,and entered the cells via endosome mediated cell entry pathway.Viruses moved in a slow–fast–slow oscillatory movement pattern and finally accumulated in a perinuclear region of the cell.Our results also showed that once inside the cell,PRRSV moved along the microtubule,microfilament and vimentin cytoskeletal elements.During the transport process,virus particles also made contacts with non-muscle myosin heavy chainⅡ-A(NMHCⅡ-A),visualized as small spheres in cytoplasm.This study can facilitate the application of QDs in virus infection imaging,especially the smaller-sized viruses and provide some novel and important insights into PRRSV infection mechanism.

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.

The Construction of Marc-145 Cell Lines Expressing Nsp2 Gene of PRRSV and the Effects of Nsp2 Protein on PRRSV Replication

[Objective]The study aimed to investigate the effects of Nsp2 protein on porcine reproductive and respiratory syndrome virus （ PRRSV） replication. [Method]Through in vitro cloning,the Nsp2 gene of highly pathogenic PRRSV TJ and attenuated TJM were amplified by RT-PCR and cloned into the plasmid pEGFP-N1,which containing enhanced green fluorescent protein expression box. The constructed plasmids pEGFP-TJ Nsp2 and pEGFP-TJM Nsp2 were transfected into Marc-145 cells and screened by G418. Anti-G418 Marc-145-TJ Nsp2 and Marc-145-TJM Nsp2 cells were obtained,and the expression of Nsp2 protein in anti-G418 Marc-145-TJ Nsp2 and Marc-145-TJM Nsp2 cells was proved by PCR and RT- PCR. The Marc-145-TJ Nsp2 and Marc-145-TJM Nsp2 cells were infected by PRRSV,and TCID 50 was determined. [Result]The cells expressing Nsp2 gene of highly pathogenic PRRSV TJ and attenuated TJM,Marc-145-TJ Nsp2 and Marc-145-TJM Nsp2,were stable. PRRSV replication was fast in early stage on these cells. That is to say,Nsp2 protein played a positive role in early phase of PRRSV proliferation,and the effect of Nsp2 protein of highly pathogenic PRRSV TJ was more obvious. [Conclusion]The construction of Marc-145-Nsp2 cell lines provided data for the further discuss of PRRSV replication mechanism.

Construction and immunogenicity of recombinant pseudorabies virus expressing the modified GP5m protein of porcine reproduction and respiratory syndrome virus

Pseudorabies virus(PRV),an alpha-herpesvirus,has been developed as a live viral vector for animal vaccines.However,the PRV recombinant virus TK^(-)/gE^(-)/GP5^(+)expressing GP5 of porcine reproductive and respiratory syn-drome virus(PRRSV),based on the PRV genetically depleted vaccine strain TK^(-)/gE^(-)/LacZ^(+),scarcely stimulated the vaccinated animals to produce neutralizing antibodies against PRRSV.To develop a booster-specific immune response of such PRV recombinants,the ORF5m gene(the modified ORF5 gene having better immune responses)was substituted for the ORF5 gene and introduced into PRV TK^(-)/gE^(-)/LacZ^(+),resulting in a PRV recombinant named TK^(-)/gE^(-)/GP5m^(+),which expressed the modified GP5m protein.The recombinant virus was confirmed using PCR,Southern blotting and Western blotting.TK^(-)/gE^(-)/GP5m^(+)and TK^(-)/gE^(-)/GP5^(+)expressing the authentic GP5 protein were inoculated into Balb/c mice to evaluate their immune responses.The results indicated that the protecting neutralization antibodies(the 3/6 vaccinated mice obtained 1:16)and cell immune responses induced by TK^(-)/gE^(-)/GP5m^(+)against PRRSV were higher than that induced by TK^(-)/gE^(-)/GP5^(+).Thus,the development of the new PRV recombinant expressing the modified GP5m protein as a candidate vaccine established the basis for the study of bivalent genetic engineering vaccines against PRRSV and PRV.

The Origin of PRRSV and Advances in the Evolution and Pathogenicity of PRRSV 1

Porcine reproductive and respiratory syndrome virus(PRRSV) has been mutating and evolving constantly since its emergence in the1980s, which has brought inestimable economic losses to the global swine industry. The virus has two genotypes, of which genotype 1 PRRSV(PRRSV 1) first broke out in Germany and mainly prevailed in Europe, which can be clustered into four subtypes based on the ORF5 sequence. Al-though few cases of PRRSV 1 have been reported in China, the prevention and control of PRRSV should not be ignored. The origin of PRRSV, ge-netic evolution and pathogenicity of PRRSV 1 were retrospectively analyzed, in order to provide valuable evidences for molecular epidemiology and immune prevention and control of PRRSV 1.

Study on PRRSV Receptor Genes Differential Expression in Lung Tissues in Different Breeds of Pigs after Infecting with HP-PRRSV

[ Objective] In order to study the susceptibility molecular mechanism of highly pathogenic porcine reproductive and respiratory syndrome virus （ HP- PRRSV） JXA1 isolate on Tibetan pig, Zangmei pig and Yorkshire pig. [ Method ] In the study, real-time quantitative RT-PCR method was established to compare and analyze the differential expression of five porcine reproductive and respiratory syndrome virus （PRRSV） receptor genes （HSPG2, SIGLEC1, CD163, VIM and NMMHC-H A） in lung tissues in Tibetan pig, Zangmei pig and Yorkshire pig before the challenge and at the 4th ,7th and 14th days after the challenge with JXAI isolate. [ Results ] HSPG2 expression in Tibetan pig lung tissues increased significantly at the 4th and 14th days after the challenge with JXAI （ P 〈 0.05 ）, while decreased significantly at the 7th day after the challenge （P 〈 0.05 ）, HSPG2 expression in Zangmei pig lung tissues increased significantly at the 14th day after the challenge （P〈0.05）. SIGLECl expression in Tibetan pig lung tissues increased significantly at the 4th and 14th days after the infection（P 〈 0.05 ）, while SIGLEC 1 expression in Yorkshire pig decreased significantly at the 4th, 7th and 14th days after the challenge （P 〈0. 05 ）. CD163 expression in lung tissues of Tibetan pig and Zangmei pig both increased significantly at the 14th day after the challenge （P 〈 0.05 ）, while CD163 expression in lung tissues of Yorkshire pig decreased significantly at the 7th and 14th days after the challenge （ P 〈 0. 05 ）. VIM expression in lung tissues of Tibetan pig increased significantly at the 7th day after the challenge （ P 〈 0. 05 ）, while which of Yorkshire pig at the 7th day after the challenge decreased significantly （ P 〈 0. 05 ）. NMMHC-II A expression in lung tissues of Zangmei pig increased significantly at the 4th day after the challenge （ P 〈 0. 05 ）, and which of Yorkshire pig increased significantly at the 4th and 14th days after the challenge （P 〈 0. 05 ）. [ Conclusion] SIGLEC1 and VIM genes might be the potential key genes affecting the susceptibility of JXA1 isolate on Tibetan pig, Zangrnei pig and Yorkshire pig. Key words JXA1 isolate; Tibetan pig; Zangmei pig; Yorkshire pig; Porcine reproductive and respiratory syndrome virus receptor genes; Differential expression