GTPase activity of porcine Mx1 plays a dominant role in inhibiting the N-Nsp9 interaction and thus inhibiting PRRSV replication.

Porcine Mx1 is a type of interferon-induced GTPase that inhibits the replication of certain RNA viruses. However, the antiviral effects and the underlying mechanism of porcine Mx1 for porcine reproductive and respiratory syndrome virus (PRRSV) remain unknown. In this study, we demonstrated that porcine Mx1 could significantly inhibit PRRSV replication in MARC-145 cells. By Mx1 segment analysis, it was indicated that the GTPase domain (68-341aa) was the functional area to inhibit PRRSV replication and that Mx1 interacted with the PRRSV-N protein through the GTPase domain (68-341aa) in the cytoplasm. Amino acid residues K295 and K299 in the G domain of Mx1 were the key sites for Mx1-N interaction while mutant proteins Mx1(K295A) and Mx1(K299A) still partially inhibited PRRSV replication. Furthermore, we found that the GTPase activity of Mx1 was dominant for Mx1 to inhibit PRRSV replication but was not essential for Mx1-N interaction. Finally, mechanistic studies demonstrated that the GTPase activity of Mx1 played a dominant role in inhibiting the N-Nsp9 interaction and that the interaction between Mx1 and N partially inhibited the N-Nsp9 interaction. We propose that the complete anti-PRRSV mechanism of porcine Mx1 contains a two-step process: Mx1 binds to the PRRSV-N protein and subsequently disrupts the N-Nsp9 interaction by a process requiring the GTPase activity of Mx1. Taken together, the results of our experiments describe for the first time a novel mechanism by which porcine Mx1 evolves to inhibit PRRSV replication. IMPORTANCE: Mx1 protein is a key mediator of the interferon-induced antiviral response against a wide range of viruses. How porcine Mx1 affects the replication of porcine reproductive and respiratory syndrome virus (PRRSV) and its biological function has not been studied. Here, we show that Mx1 protein inhibits PRRSV replication by interfering with N-Nsp9 interaction. Furthermore, the GTPase activity of porcine Mx1 plays a dominant role and the Mx1-N interaction plays an assistant role in this interference process. This study uncovers a novel mechanism evolved by porcine Mx1 to exert anti-PRRSV activities.

PRRSV nonstructural protein 11 degrades swine ISG15 by its endoribonuclease activity to antagonize antiviral immune response.

Porcine reproductive and respiratory syndrome virus (PRRSV) is an enveloped positive-stranded RNA virus which causes serious economic losses to pig industry worldwide. Type I IFN induces expression of interferon-stimulated genes 15 (ISG15) to inhibit virus replication. To survive in the host, PRRSV has evolved to antagonize the antiviral response of ISGylation. Previous studies have reported that nonstructural protein 2 of PRRSV inhibits the ISGylation and antiviral function of ISG15 depending on its ovarian tumor (OTU) domain/papain-like protease domain (PLP2). However, whether there are other PRRSV proteins inhibiting ISGylation of cellular proteins is less well understood. In this study, we first found that PRRSV Nsp11 decreased ISGylation of cellular proteins. Meanwhile, the expression level of ISG15 was significantly inhibited by Nsp11. Further mechanistic studies demonstrated that the transcription of ISG15 was reduced by endoribonuclease activity of Nsp11. Finally, we found that the Nsp11-induced degradation of ISG15 was partially relied on autophagy-lysosome system. Taken together, PRRSV Nsp11 antagonizes the antiviral response of ISG15 by its endoribonuclease activity to promote PRRSV replication. Our results reveal a novel mechanism that PRRSV inhibits ISGylation of cellular proteins and impairs host innate immune response.

3Cpro of FMDV inhibits type II interferon-stimulated JAK-STAT signaling pathway by blocking STAT1 nuclear translocation.

Foot-and-mouth disease virus (FMDV) has developed various strategies to antagonize the host innate immunity. FMDV Lpro and 3Cpro interfere with type I IFNs through different mechanisms. The structural protein VP3 of FMDV degrades Janus kinase 1 to suppress IFN-γ signaling transduction. Whether non-structural proteins of FMDV are involved in restraining type II IFN signaling pathways is unknown. In this study, it was shown that FMDV replication was resistant to IFN-γ treatment after the infection was established and FMDV inhibited type II IFN induced expression of IFN-γ-stimulated genes (ISGs). We also showed for the first time that FMDV non-structural protein 3C antagonized IFN-γ-stimulated JAK-STAT signaling pathway by blocking STAT1 nuclear translocation. 3Cpro expression significantly reduced the ISGs transcript levels and palindromic gamma-activated sequences (GAS) promoter activity, without affecting the protein level, tyrosine phosphorylation, and homodimerization of STAT1. Finally, we provided evidence that 3C protease activity played an essential role in degrading KPNA1 and thus inhibited ISGs mRNA and GAS promoter activities. Our results reveal a novel mechanism by which an FMDV non-structural protein antagonizes host type II IFN signaling.

Sodium Butyrate Ameliorates Type 2 Diabetes-Related Sarcopenia Through IL-33-Independent ILC2s/IL-13/STAT3 Signaling Pathway.

Purpose: Sarcopenia has been described as a new complication of type 2 diabetes mellitus (T2DM). T2DM and sarcopenia impact each other, resulting in a variety of adverse outcomes such as frailty, disability, poor quality of life and increased mortality. Sodium butyrate (NaB) is reported to play a protective role against T2DM. The present study aimed to investigate whether NaB could ameliorate T2DM-related sarcopenia and the underlying mechanisms. Materials and Methods: The male db/db mice at 7-weeks were used as T2DM-related sarcopenia animal model with C57BL/6J mice as control. Mice were grouped according to whether they received NaB orally as follows: C57BL/6J+water group, C57BL/6J+NaB group, db/db+water group, and db/db+NaB group. Then, db/db mice receiving NaB orally were administered with inhibitors of group 2 innate lymphocytes (ILC2s), anti-CD90.2 by intraperitoneal injection divided into db/db+NaB+PBS group and db/db+NaB+anti-CD90.2 group. NaB dissolved in water at 150 mM. The skeletal muscle mass was measured by dural X-ray (DXA) test. ILC2s in spleen and skeletal muscle were evaluated by flow cytometry. The expressions of IL-33, IL-13, STAT3, P-STAT3, GATA-3 and peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) were assessed by ELISA or WB. The morphology of skeletal muscle fibers was assessed by immunofluorescence staining. Results: The proportion of ILC2s and the expressions of ILC2s markers IL-13 and GATA-3 were all significantly decreased in db/db mice, and these changes were improved by NaB. NaB increased the proportion of slow-twitch fibers in gastrocnemius, thus partially reversing the reduced exercise capacity of db/db mice. The expression of slow-twitch fibers marker PGC-1α induced by NaB was increased via activation of ILC2s/IL-13/STAT3 pathway. On the other way, IL-33 was not necessary for the activation of ILC2s/IL-13/STAT3 pathway. After depletion of ILC2s by anti-CD90.2, the ameliorating effect of NaB on T2DM-related sarcopenia was partially antagonized. Conclusion: These results indicated that NaB could ameliorate type 2 diabetes-related sarcopenia by activating IL-33-independent ILC2s/IL-13/STAT3 signaling pathway.

Swine NONO is an essential factor to inhibit pseudorabies virus infection.

Pseudorabies virus (PRV) is a member of the genus Varicellovirus, family Herpesviridae and causes Aujeszky's disease to lead to huge economic losses in the global pig industry. The Non-POU domain-containing octamer-binding protein (NONO), as a Drosophila behavior/human splicing (DBHS) protein, plays a key role in multiple biological functions in cells, including transcriptional regulation, RNA splicing, DNA repair and so on. However, whether swine NONO (sNONO) inhibits PRV infection is less understood. In this study, we showed that sNONO was a crucial host factor for antagonizing PRV infection and positive regulated transcription levels of ISGs. After PRV infection, sNONO enhanced the activation of IFN-ß promoter and IFN-ß expression. Furthermore, knockout of sNONO in PAM-KNU cells impaired activation of type I IFN pathway and increased PRV propagation. Taken together, we have first elucidated the anti-PRV function and mechanism of sNONO, which may provide a new strategy for preventing DNA virus infection.

Multiple-Site SUMOylation of FMDV 3C Protease and Its Negative Role in Viral Replication.

Protein SUMOylation represents an important cellular process that regulates the activities of numerous host proteins as well as of many invasive viral proteins. Foot-and-mouth disease virus (FMDV) is the first animal virus discovered. However, whether SUMOylation takes place during FMDV infection and what role it plays in FMDV pathogenesis have not been investigated. In the present study, we demonstrated that SUMOylation suppressed FMDV replication by small interfering RNA (siRNA) transfection coupled with pharmaceutical inhibition of SUMOylation, which was further confirmed by increased virus replication for SUMOylation-deficient FMDV with mutations in 3C protease, a target of SUMOylation. Moreover, we provided evidence that four lysine residues, Lys-51, -54, -110, and -159, worked together to confer the SUMOylation to the FMDV 3C protease, which may make SUMOylation of FMDV 3C more stable and improve the host's chance of suppressing the replication of FMDV. This is the first report that four lysine residues can be alternatively modified by SUMOylation. Finally, we showed that SUMOylation attenuated the cleavage ability, the inhibitory effect of the interferon signaling pathway, and the protein stability of FMDV 3C, which appeared to correlate with a decrease in FMDV replication. Taken together, the results of our experiments describe a novel cellular regulatory event that significantly restricts FMDV replication through the SUMOylation of 3C protease. IMPORTANCE FMD is a highly contagious and economically important disease in cloven-hoofed animals. SUMOylation, the covalent linkage of a small ubiquitin-like protein to a variety of substrate proteins, has emerged as an important posttranslational modification that plays multiple roles in diverse biological processes. In this study, four lysine residues of FMDV 3C were found to be alternatively modified by SUMOylation. In addition, we demonstrated that SUMOylation attenuated FMDV 3C function through multiple mechanisms, including cleavage ability, the inhibitory effect of the interferon signaling pathway, and protein stability, which, in turn, resulted in a decrease of FMDV replication. Our findings indicate that SUMOylation of FMDV 3C serves as a host cell defense against FMDV replication. Further understanding of the cellular and molecular mechanisms driving this process should offer novel insights to design an effective strategy to control the dissemination of FMDV in animals.

The functional role of fecal microbiota transplantation on Salmonella Enteritidis infection in chicks.

The intestinal microbiota plays important roles in animal health and growth. We investigated the efficacy and mechanisms of fecal microbiota transplantation (FMT) from adult SPF chickens against Salmonella Enteritidis (SE) infection in chicks. We transplanted 160 recipient SPF chicks (1-day-old) that were randomly divided into four groups, Ca (challenge), Cb (non-challenge), Fa (FMT and challenge) and Fb (FMT without challenge). The experiment lasted 40 days. We found that FMT reduced mortality as well as liver inflammatory lesions, promoted weight gain, improved immunity, ameliorated the digestion and absorption ability and inhibited SE colonization in the liver of challenged chicks. 16S rRNA gene high-throughput sequencing indicated that SE challenge caused a significant increase in the relative abundance of Parasutterella in the cecal microbiota of the recipient chicks (P < 0.05). FMT led to the maturation of the intestinal flora of recipients and the relative abundance of the Bacteroides, Rikenellaceae_ RC9_ gut_ group, Prevotellaceae_ UCG_ 001, Prevotellaceae_ Ga6A1_ group and Parabacteroides was significantly increased (P < 0.05). FMT from adult SPF chickens regulated the intestinal microbiota of chicks and increased resistance to SE infection.

Humic Acids Inhibit Platelet Activation to Reduce Venous Thromboembolism in Mice.

Objective: We aimed to investigate the effects of the natural product humic acids (HA) on platelet activation and development of venous thromboembolism (VTE) in mice and further explore the relevant mechanism. Methods: Eight-week C57BL/6 mice were randomly assigned to three groups: sham operation group (n = 7), VTE group (n = 8), and VTE + HA group (n = 10). Thrombi were harvested to hematoxylin-eosin staining to evaluate the thrombolysis and recanalization of the thrombus. In addition, flow cytometry was performed to detect the expression levels of protein disulfide isomerase on endothelial-derived exosomes and glycoprotein IIb/IIIa on the surface of the activated platelets surface in plasma. Furthermore, the protein expression level of glycoprotein IIb/IIIa in thrombus was determined by immunohistochemistry and immunofluorescence. Results: The length of thrombosis in the VTE + HA group was significantly shorter than that in the VTE group (P = 0.040). No significant differences were observed in thrombolysis and recanalization between the VTE + HA group and the VTE group (P > 0.05). The content of protein disulfide isomerase carried by endothelial-derived exosomes was significantly increased in the VTE group (P = 0.008) but significantly reduced by native humic acids (P = 0.012). Compared with the VTE group, the expression of glycoprotein IIb/IIIa on activated platelet surface in the VTE + HA group was significantly decreased (P = 0.002). The concentration of plasmatic P-selectin in the VTE group was significantly higher than that in the VTE + HA group (P < 0.001). Conclusion: We demonstrate that HA possess a pharmacological property that decreases venous thrombus formation in mice. The underlying mechanism is that HA could inhibit the expression of glycoprotein IIb/IIIa on the activated platelets surface by suppressing endothelial-derived exosomes carrying on protein disulfide isomerase, thereby blocking platelet activation.

Broad Impact of Exchange Protein Directly Activated by cAMP 2 (EPAC2) on Respiratory Viral Infections.

The recently discovered exchange protein directly activated by cAMP (EPAC), compared with protein kinase A (PKA), is a fairly new family of cAMP effectors. Soon after the discovery, EPAC has shown its significance in many diseases including its emerging role in infectious diseases. In a recent study, we demonstrated that EPAC, but not PKA, is a promising therapeutic target to regulate respiratory syncytial virus (RSV) replication and its associated inflammation. In mammals, there are two isoforms of EPAC-EPAC1 and EPAC2. Unlike other viruses, including Middle East respiratory syndrome coronavirus (MERS-CoV) and Ebola virus, which use EPAC1 to regulate viral replication, RSV uses EPAC2 to control its replication and associated cytokine/chemokine responses. To determine whether EPAC2 protein has a broad impact on other respiratory viral infections, we used an EPAC2-specific inhibitor, MAY0132, to examine the functions of EPAC2 in human metapneumovirus (HMPV) and adenovirus (AdV) infections. HMPV is a negative-sense single-stranded RNA virus belonging to the family Pneumoviridae, which also includes RSV, while AdV is a double-stranded DNA virus. Treatment with an EPAC1-specific inhibitor was also included to investigate the impact of EPAC1 on these two viruses. We found that the replication of HMPV, AdV, and RSV and the viral-induced immune mediators are significantly impaired by MAY0132, while an EPAC1-specific inhibitor, CE3F4, does not impact or slightly impacts, demonstrating that EPAC2 could serve as a novel common therapeutic target to control these viruses, all of which do not have effective treatment and prevention strategies.

Improving the Performance of ZnS Photocatalyst in Degrading Organic Pollutants by Constructing Composites with Ag2O.

ZnS is a promising photocatalyst in water purification, whereas its low photon efficiency and poor visible-light response restrict its application. Constructing composites may help solve these problems. In this work, Ag2O was introduced to ZnS for the first time based on their energy band characteristics to form a novel ZnS/Ag2O composite photocatalyst. In the model reaction of degrading methylene blue, the as-designed catalyst exhibited high catalytic activity among a series of ZnS-based composite photocatalysts under similar conditions. The catalytic rate constant was up to 0.138 min-1, which is 27.4- and 15.6-times higher than those of ZnS and Ag2O. This composite degraded 92.4% methylene blue in 50 min, while the ratios were 31.9% and 68.8% for ZnS and Ag2O. Catalytic mechanism study based on photoluminescence and radical-scavenging experiments revealed that the enhanced photocatalytic activity was attributed to the composite structure of ZnS/Ag2O. The structure not only facilitated the separation and transmission of photogenerated carriers but also extended the light response range of the catalyst. The as-designed ZnS/Ag2O composite is promising in degrading organic pollutants in water.

Inhibition of Antiviral Innate Immunity by Foot-and-Mouth Disease Virus Lpro through Interaction with the N-Terminal Domain of Swine RNase L.

Foot-and-mouth disease virus (FMDV) is the pathogen of foot-and-mouth disease (FMD), which is a highly contagious disease in cloven-hoofed animals. To survive in the host, FMDV has evolved multiple strategies to antagonize host innate immune responses. In this study, we showed that the leader protease (Lpro) of FMDV, a papain-like proteinase, promoted viral replication by evading the antiviral interferon response through counteracting the 2',5'-oligoadenylate synthetase (OAS)/RNase L system. Specifically, we observed that the titers of Lpro deletion virus were significantly lower than those of wild-type FMDV (FMDV-WT) in cultured cells. Our mechanistic studies demonstrated that Lpro interfered with the OAS/RNase L pathway by interacting with the N-terminal domain of swine RNase L (sRNase L). Remarkably, Lpro of FMDV exhibited species-specific binding to RNase L in that the interaction was observed only in swine cells, not human, monkey, or canine cells. Lastly, we presented evidence that by interacting with sRNase L, FMDV Lpro inhibited cellular apoptosis. Taken together, these results demonstrate a novel mechanism that Lpro utilizes to escape the OAS/RNase L-mediated antiviral defense pathway. IMPORTANCE FMDV is a picornavirus that causes a significant disease in agricultural animals. FMDV has developed diverse strategies to escape the host interferon response. Here, we show that Lpro of FMDV antagonizes the OAS/RNase L pathway, an important interferon effector pathway, by interacting with the N-terminal domain of sRNase L. Interestingly, such a virus-host interaction is species-specific because the interaction is detected only in swine cells, not in human, monkey, or canine cells. Furthermore, Lpro inhibits apoptosis through interacting with sRNase L. This study demonstrates a novel mechanism by which FMDV has evolved to inhibit host innate immune responses.

Crystal structures of porcine STINGCBD-CDN complexes reveal the mechanism of ligand recognition and discrimination of STING proteins.

The cyclic dinucleotide (CDN)-stimulator of interferon genes (STING) pathway plays an important role in the detection of viral and bacterial pathogens in animals. Previous studies have shown that the metazoan second messenger cyclic [G(2',5')pA(3',5')p] (2',3'-cGAMP) generated by cyclic GMP-AMP synthase cGAS binds STING with high affinity compared with bacterial CDNs such as c-di-GMP, c-di-AMP, and 3',3'-cGAMP. Despite recent progress indicating that the CDN-binding domain (CBD) of dimeric STING binds asymmetric 2',3'-cGAMP preferentially over symmetric 3',3'-CDNs, it remains an open question whether STING molecules, such as human STING, adopt a symmetric dimeric conformation to efficiently engage its asymmetric ligand. Here, structural studies of the CBD from porcine STING (STINGCBD) in complex with CDNs at 1.76-2.6 Å resolution revealed that porcine STINGCBD, unlike its human and mouse counterparts, can adopt an asymmetric ligand-binding pocket to accommodate the CDNs. We observed that the extensive interactions and shape complementarity between asymmetric 2',3'-cGAMP and the ligand-binding pocket make it the most preferred ligand for porcine STING and that geometry constraints limit the binding between symmetric 3',3'-CDN and porcine STING. The ligand-discrimination mechanism of porcine STING observed here expands our understanding of how the CDN-STING pathway is activated and of its role in antiviral defense.

CRISPR-Cas9 Mediated RNase L Knockout Regulates Cellular Function of PK-15 Cells and Increases PRV Replication.

Ribonuclease L (RNase L) is an important antiviral endoribonuclease regulated by type I IFN. RNase L is activated by viral infection and dsRNA. Because the role of swine RNase L (sRNase L) is not fully understood, in this study, we generated a sRNase L knockout PK-15 (KO-PK) cell line through the CRISPR/Cas9 gene editing system to evaluate the function of sRNase L. After transfection with CRISPR-Cas9 followed by selection using puromycin, sRNase L knockout in PK-15 cells was further validated by agarose gel electrophoresis, DNA sequencing, and Western blotting. The sRNase L KO-PK cells failed to trigger RNA degradation and induced less apoptosis than the parental PK-15 cells after transfected with poly (I: C). Furthermore, the levels of ISGs mRNA in sRNase L KO-PK cells were higher than those in the parental PK-15 cells after treated with poly (I: C). Finally, both wild type and attenuated pseudorabies viruses (PRV) replicated more efficiently in sRNase L KO-PK cells than the parental PK-15 cells. Taken together, these findings suggest that sRNase L has multiple biological functions including cellular single-stranded RNA degradation, induction of apoptosis, downregulation of transcript levels of ISGs, and antiviral activity against PRV. The sRNase L KO-PK cell line will be a valuable tool for studying functions of sRNase L as well as for producing PRV attenuated vaccine.

Review of advanced physical and data-driven models for dynamic bioprocess simulation: Case study of algae-bacteria consortium wastewater treatment.

Microorganism production and remediation processes are of critical importance to the next generation of sustainable industries. Undertaking mathematical treatment of dynamic biosystems operating at any spatial or temporal scale is essential to guarantee their performance and safety. However, constructing physical models remains a challenge due to the extreme complexity of process biological mechanisms. Data-driven models also encounter severe limitations because datasets from large-scale bioprocesses are often scarce without complete information and on a restricted operational space. To fill this gap, the current research compares the performance of advanced physical and data-driven models for dynamic bioprocess simulations subject to incomplete and scarce datasets, which to the best of our knowledge has never been addressed before. In specific, kinetic models were constructed by integrating different classic models, and state-of-the-art hyperparameter selection frameworks were developed to design artificial neural networks and Gaussian process regression models. An algae-bacteria consortium wastewater treatment process was selected to test the accuracy of these modeling strategies, as it is one of the most sophisticated biosystems due to the intricate mutualistic and competitive interactions. Based on the current results and available data, a heuristic model selection procedure is provided. This study paves the way to facilitate future bioprocess modeling.

Characterization of a moderately pathogenic pseudorabies virus variant isolated in China, 2014.

In this study, we reported a moderately pathogenic pseudorabies virus (PRV) variant isolated from one Bartha-K61-vaccinated pig farm in Weifang, Shandong Province, China, 2014. The sick piglets in the farm were characterized by anorexia, weight loss and neurologic symptoms but did not die. Sequence alignment of the gE gene indicated that it belonged to a new mutated PRV strain and about 15% amino acid sites had mutations, deficiencies and insertions compared to the other PRV strains. The gD gene had two amino acid insertions and ten amino acid mutations in comparison with the Bartha-K61 vaccine strain. The TK and gM genes were the same as one highly pathogenic PRV TJ strain. Evidence from virus isolation, laboratory challenge, serological detection and histopathologic examination confirmed that the etiological agent of the disease is PRV SD1404, which is a moderately pathogenic strain and causes piglets to be sick but not to die. PRV SD1404 strain is different from other reports and should be paid more attention to avoid economic losses.

Publisher Correction: Emergence of Different Recombinant Porcine Reproductive and Respiratory Syndrome Viruses, China.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

Crystal structures of manganese-dependent transcriptional repressor MntR (Rv2788) from Mycobacterium tuberculosis in apo and manganese bound forms.

The pathogenic Mycobacterium tuberculosis encodes two members of the DtxR family metalloregulators, IdeR and MntR. IdeR represses gene expression in response to ferrous iron, while MntR (Rv2788) functions as a manganese-dependent transcriptional repressor, which represses the expression of manganese transporter genes to maintain manganese homeostasis. Although the structural study towards IdeR is in-depth, there is no MntR structure available. Herein, we report both apo and manganese bound forms of MntR structures from M. tuberculosis. MntR has evolved into two metal ion binding sites like other DtxR proteins and for the first time, we captured the two sites fully occupied by its natural ions with one Mn2+ ion at the first site and two Mn2+ ions at the second binding site (binuclear manganese cluster). The conformation change of MntR resulting from manganese binding could prime the MntR for DNA binding, which is a conserved activation mechanism among DtxR family.

Establishment and Characterization of a High and Stable Porcine CD163-Expressing MARC-145 Cell Line.

Isolation and identification of diverse porcine reproductive and respiratory syndrome viruses (PRRSVs) play a fundamental role in PRRSV research and disease management. However, PRRSV has a restricted cell tropism for infection. MARC-145 cells are routinely used for North American genotype PRRSV isolation and vaccine production. But MARC-145 cells have some limitations such as low virus yield. CD163 is a cellular receptor that mediates productive infection of PRRSV in various nonpermissive cell lines. In this study, we established a high and stable porcine CD163- (pCD163-) expressing MARC-145 cell line toward increasing its susceptibility to PRRSV infection. Indirect immunofluorescence assay (IFA) and Western blotting assays showed that pCD163 was expressed higher in pCD163-MARC cell line than MARC-145 cells. Furthermore, the ability of pCD163-MARC cell line to propagate PRRSV was significantly increased as compared with MARC-145 cells. Finally, we found that pCD163-MARC cell line had a higher isolation rate of clinical PRRSV samples and propagated live attenuated PRRS vaccine strains more efficiently than MARC-145 cells. This pCD163-MARC cell line will be a valuable tool for propagation and research of PRRSV.

Emergence of Different Recombinant Porcine Reproductive and Respiratory Syndrome Viruses, China.

Epidemiological investigations were conducted on recently emerging porcine reproductive and respiratory syndrome virus (PRRSV) strains in Shandong province in 2014-2015. The proportion of the NADC30 strain identified by ORF7 sequence alignment has been gradually increasing. Three emerging PRRSV strains were successfully isolated, and the complete genomic sequences were determined. Our results indicate the importance of recombinant strains in Shandong province, China. There was a varied degree of recombination of two or three strains (classical, HP-PRRSV and/or NADC30). Moreover, the recombination strains affected the pathogenicity of newly emerged strains.