Development of an effective one-step double-antigen sandwich ELISA based on p72 to detect antibodies against African swine fever virus.

African swine fever (ASF), caused by ASF virus (ASFV), is a highly contagious and lethal disease of domestic pigs leading to tremendous economic losses. As there are no vaccines and drugs available. An effective diagnosis to eliminate ASFV-infected pigs is a crucial strategy to prevent and control ASF. To this end, ASFV capsid protein p72 was expressed using Chinese hamster ovary (CHO) cells and subsequently conjugated with horseradish peroxidase (HRP) to develop a one-step double-antigen sandwich enzyme-linked immunosorbent assay (one-step DAgS-ELISA). The performance of this ELISA for detecting ASFV antibodies was evaluated. Overall, a diagnostic sensitivity of 97.96% and specificity of 98.96% was achieved when the cutoff value was set to 0.25. No cross-reaction with healthy pig serum and other swine viruses was observed. The coefficients of variation of the intra-assay and inter-assay were both <10%. Importantly, this ELISA could detect antibodies in standard serum with 12,800-fold dilution, and seroconversion started from the 7th day post-inoculation (dpi), showing excellent analytical sensitivity and great utility. Furthermore, compared to the commercial kit, this ELISA had a good agreement and significantly shorter operation time. Collectively, a novel one-step DAgS-ELISA for detecting antibodies against ASFV is developed, which will be reliable and convenient to monitor ASFV infection.

The Alpha-1 Subunit of the Na+/K+-ATPase (ATP1A1) Is a Host Factor Involved in the Attachment of Porcine Epidemic Diarrhea Virus.

Porcine epidemic diarrhea (PED) is an acute and severe atrophic enteritis caused by porcine epidemic diarrhea virus (PEDV) that infects pigs and makes huge economic losses to the global swine industry. Previously, researchers have believed that porcine aminopeptidase-N (pAPN) was the primary receptor for PEDV, but it has been found that PEDV can infect pAPN knockout pigs. Currently, the functional receptor for PEDV remains unspecified. In the present study, we performed virus overlay protein binding assay (VOPBA), found that ATP1A1 was the highest scoring protein in the mass spectrometry results, and confirmed that the CT structural domain of ATP1A1 interacts with PEDV S1. First, we investigated the effect of ATP1A1 on PEDV replication. Inhibition of hosts ATP1A1 protein expression using small interfering RNA (siRNAs) significantly reduced the cells susceptibility to PEDV. The ATP1A1-specific inhibitors Ouabain (a cardiac steroid) and PST2238 (a digitalis toxin derivative), which specifically bind ATP1A1, could block the ATP1A1 protein internalization and degradation, and consequently reduce the infection rate of host cells by PEDV significantly. Additionally, as expected, overexpression of ATP1A1 notably enhanced PEDV infection. Next, we observed that PEDV infection of target cells resulted in upregulation of ATP1A1 at the mRNA and protein levels. Furthermore, we found that the host protein ATP1A1 was involved in PEDV attachment and co-localized with PEDV S1 protein in the early stage of infection. In addition, pretreatment of IPEC-J2 and Vero-E6 cells with ATP1A1 mAb significantly reduced PEDV attachment. Our observations provided a perspective on identifying key factors in PEDV infection, and may provide valuable targets for PEDV infection, PEDV functional receptor, related pathogenesis, and the development of new antiviral drugs.

Genome-Wide mRNA and Long Non-Coding RNA Analysis of Porcine Trophoblast Cells Infected with Porcine Reproductive and Respiratory Syndrome Virus Associated with Reproductive Failure.

Porcine reproductive and respiratory syndrome (PRRS) is a vertically transmitted reproductive disorder that is typically characterized by miscarriage, premature birth, and stillbirth in pregnant sows after infection. Such characteristics indicate that PRRSV can infect and penetrate the porcine placental barrier to infect fetus piglets. The porcine trophoblast is an important component of the placental barrier, and secretes various hormones, including estrogen and progesterone, to maintain normal pregnancy and embryonic development during pregnancy. It is conceivable that the pathogenic effects of PRRSV infection on porcine trophoblast cells may lead to reproductive failure; however, the underlying detailed mechanism of the interaction between porcine trophoblast (PTR2) cells and PRRSV is unknown. Therefore, we conducted genome-wide mRNA and long non-coding RNA (lncRNA) analysis profiling in PRRSV-infected PTR2. The results showed that 672 mRNAs and 476 lncRNAs were significantly different from the control group after viral infection. Target genes of the co-expression and co-location of differential mRNAs and lncRNAs were enriched by GO (gene ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) analysis, revealing that most of the pathways were involved in cell nutrient metabolism, cell proliferation, and differentiation. Specifically, the estrogen signaling pathway, the PI3K (PhosphoInositide-3 Kinase)-Akt (serine/threonine kinase) signaling pathway, and the insulin secretion related to embryonic development were selected for analysis. Further research found that PRRSV inhibits the expression of G-protein-coupled estrogen receptor 1 (GPER1), thereby reducing estrogen-induced phosphorylation of AKT and the mammalian target of rapamycin (mTOR). The reduction in the phosphorylation of AKT and mTOR blocks the activation of the GPER1- PI3K-AKT-mTOR signaling pathway, consequently restraining insulin secretion, impacting PTR2 cell proliferation, differentiation, and nutrient metabolism. We also found that PRRSV triggered trophoblast cell apoptosis, interrupting the integrity of the placental villus barrier. Furthermore, the interaction network diagram of lncRNA, regulating GPER1 and apoptosis-related genes, was constructed, providing a reference for enriching the functions of these lncRNA in the future. In summary, this article elucidated the differential expression of mRNA and lncRNA in trophoblast cells infected with PRRSV. This infection could inhibit the PI3K-AKT-mTOR pathway and trigger apoptosis, providing insight into the mechanism of the vertical transmission of PRRSV and the manifestation of reproductive failure.

Establishment of a Real-Time Quantitative PCR Assay for Porcine Circovirus-Like Virus and the First Evidence of Its Spread to Hainan and Jiangxi Provinces of China.

Porcine Circovirus-like (PCL) virus, a new emerging virus, has been widely detected in Guangdong, Guangxi, and Anhui provinces in China, which may be a novel agent causing severe diarrhea in newborn piglets and tending to spread widely. Evidence suggests that the virus is related to hemorrhagic enteritis and diarrhea, and many newborn piglets were emaciated to death after infection. Therefore, a sensitive, quick, and accurate detection system for virus detection and epidemiological investigation is necessary. In this study, we developed a real-time quantitative PCR assay based on SYBR green for the detection of PCL virus. The ORF4 conserved region of PCL virus was found by the alignment of the uploaded genome sequences to design specific primers, and the primers were tested and showed good specificity, sensitivity, and reproducibility. Approximately, 138 fecal samples were obtained from diarrheal pigs in South China from June to December 2021. Approximately, 22.46% (31/138) of the samples and 40% (8/20) of the pig farms were positive for PCL virus, respectively, by using this method. Moreover, it is worth noting that the virus was first detected in Hainan and Jiangxi Provinces of China, which means that the virus may spread widely in China. Through evolutionary tree analysis and partial sequence comparison, there are some differences of virus genes in each province, suggesting that there is a risk of variation, and the four PCL virus strains showed a sequence similarity of 86.7%-87.8% for the rep gene and 92.2%-92.9% for the Rep protein, respectively, with Bo-Circo-like virus that is detected in bovine, which further demonstrates a close relationship between the two viruses that originated from different animals. In conclusion, our study provides a useful diagnostic approach to PCL virus detection and epidemiological inquiry. Meanwhile, the epidemic data using this real-time qPCR assay provide evidence for the widespread variations and epidemic of the virus in South China, and warn the appropriate measures for prevention, and control of porcine circovirus-like virus infection should be under consideration in pig production.

A Nectin1 Mutant Mouse Model Is Resistant to Pseudorabies Virus Infection.

The present study generated nectin1-mutant mice with single amino acid substitution and tested the anti-pseudorabies virus (PRV) ability of the mutant mice, with the aim to establish a model for PRV-resistant livestock. A phenylalanine to alanine transition at position 129 (F129A) of nectin1 was introduced into the mouse genome to generate nectin1 (F129A) mutant mice. The mutant mice were infected with a field-isolated highly virulent PRV strain by subcutaneous injection of virus. We found that the homozygous mutant mice had significantly alleviated disease manifestations and decreased death rate and viral loading in serum and tissue compared with heterozygous mutant and wild-type mice. In addition to disease resistance, the homozygous mutant mice showed a defect in eye development, indicating the side effect on animals by only one amino acid substitution in nectin1. Results demonstrate that gene modification in nectin1 is an effective approach to confer PRV resistance on animals, but the mutagenesis pattern requires further investigation to increase viral resistance without negative effect on animal development.

One-Step Assembly of a Porcine Epidemic Diarrhea Virus Infectious cDNA Clone by Homologous Recombination in Yeast: Rapid Manipulation of Viral Genome With CRISPR/Cas9 Gene-Editing Technology.

Porcine epidemic diarrhea virus (PEDV), a swine enteric coronavirus causing acute diarrhea in piglets, is one of the major threatens to the pork industry globally. Reverse genetics is a valuable tool for the virological study and vaccine development for coronaviruses. Due to the large size and unstable problem in Escherichia coli of coronavirus genome, construction and manipulation of reverse genetics system for coronaviruses remain laborious and time-consuming. In this study, a reverse genetics system of the genotype II PEDV strain HM was generated using the transformation-associated recombination (TAR) technology in yeast within 1 week. The rescued virus (rPEDV) exhibited similar growth properties to the wild-type virus in vitro. With this PEDV infectious cDNA clone, CRISPR/Cas9 technology and homologous recombination were combined to generate a recombinant virus rPEDV-EGFP in which the ORF3 gene was swapped with an EGFP gene. The reporter virus displayed similar growth properties to the parental virus rPEDV and remained stable during serial passage in vitro. Of note, the strategies of construction and manipulation of PEDV infectious cDNA clone are extremely simple and efficient, which could be applied for other RNA viruses and DNA viruses.

A strain of highly pathogenic porcine reproductive and respiratory syndrome virus: genomic characterization, pathogenicity, and construction of an infectious full-length cDNA clone.

Porcine reproductive and respiratory syndrome (PRRS) is a highly contagious infectious disease caused by porcine reproductive and respiratory syndrome virus (PRRSV), which inflicts major economic losses on the global pig farming industry. Based on its similarity to highly pathogenic strains, the GDzj strain isolated in this study was predicted to be highly pathogenic. We therefore analyzed the pathogenicity of this strain experimentally in piglets. All piglets challenged with this virus experienced fever or high fever, loss of appetite, decreased food intake, daily weight loss, shortness of breath, and listlessness, and the necropsy results showed that they had experienced severe interstitial pneumonia. We then used the BAC system to construct a full-length cDNA infectious clone of GDzj, and the rescued virus displayed in vitro proliferation characteristics similar to those of the parental PRRSV strain. In summary, we successfully isolated a highly pathogenic PRRSV strain and constructed a full-length infectious cDNA clone from it, thereby providing an effective reverse genetics platform for further study of viral pathogenesis.

Emergence of porcine circovirus-like viruses associated with porcine diarrheal disease in China.

BACKGROUND: The circular replication-associated protein (Rep)-encoding single-stranded (CRESS) DNA virus emergence in diverse host has been associated with severe disease. Porcine circovirus-like virus (Po-Circo-like [PCL] virus) is a CRESS DNA virus, the prevalence and pathogenicity of which are rarely studied. METHODS: We obtained two blood samples, four faecal samples, and two intestinal samples from a pig farm suffered from diarrheal disease in the delivery room in September 2020 and attempted to isolate and identify a causative pathogen. Subsequently, only PCL virus was positive, and qRT-PCR was designed to detect the loading titre of PCL virus. We then initiated a heightened surveillance program on the pathogenicity and epidemiology of PCL virus. RESULTS: Six PCL virus strains, with severe diarrhoea and haemorrhagic enteritis, have been found in six different pig farms in Guangdong province, China. A multiple sequence alignment of these PCL viruses and bovine circovirus-like virus/CH showed a similarity of 92.5-94.8% for the Rep protein, indicating these PCL viruses are highly homologous to Bo-Circo-like virus associated with calf diarrhoea. There were striking similarities between the PCL virus and bovine circovirus-like virus outbreaks in aetiological settings and Genomic sequence. We found that 11.2% (20/178) of diarrhoea samples and 13.3% (6/45) of pig farms were positive for PCL virus, suggesting that PCL virus may have spread widely in Pig farms. Moreover, this article underscores the risk of PCL virus spilling over and adapting to new species. CONCLUSIONS: Porcine circovirus-like virus was found to be associated with porcine diarrheal disease in China.

Genetic variation analysis of Type 2 porcine reproductive and respiratory syndrome virus in Guangdong Province from 2016 to 2018.

Porcine reproductive and respiratory syndrome virus (PRRSV) is a notable threat to the pig industry. Long-term epidemiological investigations and genetic variation analyses of PRRSV isolates benefit PRRSV prevention and control. In our study, 43 PRRSV strains were  successfully isolated from the lungs of sick pigs, and the genetic variations of these isolates were analyzed. Phylogenetic analysis showed that the isolates belonged to PRRSV2 and that lineage 8 (8.7) subgroup III strains remained the dominant type circulating in South China. In addition, sequence alignment analysis identified many novel deletions and mutations in the Nsp2 and GP5 genes. Furthermore, phylogenetic analysis showed that highly frequent recombination events of PRRSV between different lineages might occur in Guangdong Province. These results may help to elucidate the epidemiology and genetic variation of PRRSV isolates in Guangdong Province. Keywords: GP5; Nsp2; phylogenetic analysis; sequence alignment; porcine reproductive and respiratory syndrome virus (PRRSV).

Porcine circovirus type 3 capsid protein induces NF-κB activation and upregulates pro-inflammatory cytokine expression in HEK-293T cells.

Porcine circovirus type 3 (PCV3) has been widely detected throughout the world since it was first discovered on pig farms in 2015. PCV3 is closely associated with cardiac and multisystem inflammation, respiratory disease, congenital tremors, myocarditis, diarrhea, encephalitis and neurologic disease, and periarteritis. However, there have been few reports on the relationship between PCV3 and inflammatory pathways. The NF-κB signaling pathway plays an important role in the defense against viral infection. Here, we demonstrate that the capsid protein (Cap) of PCV3 plays a key role in the activation of NF-κB signaling in HEK-293T cells. Furthermore, PCV3 Cap promotes the mRNA expression of the pro-inflammatory cytokines IL6 and TNFα. In addition, PCV3 Cap promotes RIG-I and MDA5 mRNA expression in RIG-like receptor (RLR) signaling and MyD88 mRNA expression in Toll-like receptor (TLR) signaling but does not influence TRIF mRNA expression in TLR signaling. These results show that PCV3 Cap activates NF-κB signaling, possibly through the RLR and the TLR signaling pathways. This work illustrates that PCV3 Cap activates NF-κB signaling and thus may provide a basis for the pathogenesis of PCV3 and the innate immunity of the host.

Resistance to pseudorabies virus by knockout of nectin1/2 in pig cells.

Pseudorabies virus (PRV) is a pig pathogen that causes substantial economic losses to the pig industry. Infection of host cells by PRV is mediated by the membrane proteins nectin1 and nectin2, which are presumed to be receptors for PRV infection. Here, we generated nectin1/2 knockout (KO) cells with the aim of establishing a PRV-resistant cell model. Nectin1 and 2 were ablated in PK15 cells by CRISPR/Cas9-mediated gene targeting. PRV infection in either nectin1 or nectin2 KO cells showed a significant reduction in viral growth compared with wild-type (WT) cells. We further simultaneously deleted nectin1 and nectin2 in PK15 cells and found that double KO cells showed no further increase in resistance to PRV compared with single gene-KO cells, despite being more resistant than WT. By investigating the cell entry steps of PRV infection, we found that nectin1 or/and nectin2 KO did not greatly affect virus attachment or internalization to cells but blocked cell-to-cell spread. Our results demonstrate that KO of either nectin1 or nectin2 confers PRV resistance to PK15 cells. This strategy could be applied to establish PRV-resistant pigs with nectin1/2 modifications to benefit the pig industry.

Cellular poly(C) binding protein 2 interacts with porcine epidemic diarrhea virus papain-like protease 1 and supports viral replication.

Porcine epidemic diarrhea virus (PEDV) belongs to the Alphacoronavirus genus in the Coronaviridae family. Similar to other coronaviruses, PEDV encodes two papain-like proteases. Papain-like protease (PLP)2 has been proposed to play a key role in antagonizing host innate immunity. However, the function of PLP1 remains unclear. In this study, we found that overexpression of PLP1 significantly promoted PEDV replication and inhibited production of interferon-ß. Immunoprecipitation and mass spectrometry were used to identify cellular interaction partners of PLP1. Host cell poly(C) binding protein 2 (PCBP2) was determined to bind and interact with PLP1. Both endogenous and overexpressed PCBP2 co-localized with PLP1 in the cytoplasm. Overexpression of PLP1 upregulated expression of PCBP2. Furthermore, overexpression of PCBP2 promoted PEDV replication. Silencing of endogenous PCBP2 using small interfering RNAs attenuated PEDV replication. Taken together, these data demonstrated that PLP1 negatively regulated the production of type 1 interferon by interacting with PCBP2 and promoted PEDV replication.

Genome-wide analysis of long noncoding RNA profiles in Vero cells infected with porcine epidemic diarrhea virus.

Porcine epidemic diarrhea (PED) is an acute enteric disease caused by porcine epidemic diarrhea virus (PEDV). In China, variant PEDV causes severe watery diarrhea, vomiting, and dehydration in piglets, leading to very high morbidity and mortality. However, the pathogenesis of PEDV is still not fully understood. In our study, we analyzed the long noncoding RNA (lncRNA) and mRNA expression profiles of PEDV GDgh16 in infected Vero cells at 60 h postinfection. A total of 61,790 annotated mRNAs, 14,247 annotated lncRNAs and 1290 novel lncRNAs were identified. A total of 227 annotated lncRNAs and 13 novel lncRNAs were significantly and differentially expressed after viral infection. The Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) databases were used to identify genes adjacent to the lncRNAs, and it was found that these lncRNAs were enriched in pathways related to immune and antiviral responses. Next, we selected candidate lncRNAs and their predicted target genes for study. RT-qPCR demonstrated that these lncRNAs and genes were differentially expressed after PEDV infection. Our study investigated the function of lncRNAs involved in PEDV infection, providing new insight into the pathogenic mechanisms of PEDV.

Molecular Characteristics and Pathogenicity of Porcine Epidemic Diarrhea Virus Isolated in Some Areas of China in 2015-2018.

Since 2010, Porcine epidemic diarrhea virus (PEDV) has caused severe diarrhea disease in piglets in China, resulting in large economic losses. To understand the genetic characteristics of the PEDV strains that circulated in some provinces of China between 2015 and 2018, 375 samples of feces and small intestine were collected from pigs and tested. One hundred seventy-seven samples tested positive and the PEDV-positive rate was 47.20%. A phylogenetic tree analysis based on the entire S gene showed that these strains clustered into four subgroups, GI-a, GI-b, GII-a, and GII-b, and that the GII-b strains have become dominant in recent years. Compared with previous strains, these strains have multiple variations in the SP and S1-NTD domains and in the neutralizing epitopes of the S protein. We also successfully isolated and identified a new virulent GII-b strain, GDgh16, which is well-adapted to Vero cells and caused a high mortality rate in piglets in challenge experiments. Our study clarifies the genetic characteristics of the prevalent PEDV strains in parts of China, and suggests that the development of effective novel vaccines is both necessary and urgent.

Porcine Circovirus Type 3 Cap Inhibits Type I Interferon Induction Through Interaction With G3BP1.

Porcine circovirus 3 (PCV3) infections cause clinical diseases similar to those seen in porcine circovirus 2 (PCV2) infections. It is unclear whether PCV3 infections can also cause immunosuppression like that seen with PCV2. Here, we report that Cap inhibits DNA-induced IFN-ß mRNA transcription and IFN promoter activation. Cap was also found to inhibit cyclic GMP-AMP (cGAMP) synthase (cGAS) binding to interferon-stimulating DNA (ISD). Immunoprecipitation and mass spectrometry were used to identify cellular interaction partners of Cap. Cap interacted with G3BP1 and inhibited the interaction between GTPase-activating protein-(SH3 domain)-binding protein 1 (G3BP1) and cGAS. Furthermore, the destruction of endogenously expressed G3BP1 by siRNA significantly reduced IFN promoter activation, and phosphorylation of tank-binding kinase 1 (TBK1) was induced by ISD. Overexpression of G3BP1 attenuated the inhibition of ISD binding of cGAS by Cap and promoted phosphorylation of TBK1 and IRF3 induced by ISD. Collectively, our results show that the interaction between Cap and G3BP1 prevents cGAS from recognizing DNA, thereby inhibiting the IFN production.

Porcine circovirus 3 Cap inhibits type I interferon signaling through interaction with STAT2.

Porcine circovirus 3 (PCV3) is a novel circovirus that is associated with porcine dermatitis and nephropathy syndrome, reproductive failure, and multi-systemic inflammation. The type I Interferon (IFN) signaling pathway is an important innate immune signaling pathway for defense against viral infection. Many mammalian viruses inhibit host innate immune signaling through diverse strategies. Here, we found that the PCV3 capsid protein (Cap) significantly inhibited IFN-ß-stimulated response element (ISRE) promoter activity, suggesting that Cap suppresses IFN signaling. However, Cap did not affect expression and phosphorylation levels of STAT1 and STAT2 and did not interrupt the heterodimerization of pSTAT1 and pSTAT2. Although Cap interacted with KPAN1, it did not block the interaction between KPNA1 and pSTAT1 or the nuclear translocation of pSTAT1 and pSTAT2. Interestingly, we found that Cap inhibited the activation of ISRE promoter induced by IRF9-S2C. Mechanistically, Cap interacted with the transactivation domain of STAT2, a key protein in type I IFN signaling. In addition, we found that Cap bound to ISRE and prevented ISRE binding of IRF9-S2C. This work is the first to describe the mechanism of inhibition of IFN signaling by PCV3 Cap.

Porcine epidemic diarrhea virus nsp4 induces pro-inflammatory cytokine and chemokine expression inhibiting viral replication in vitro.

Porcine epidemic diarrhea virus (PEDV) causes severe economic loss in the pig industry each year. To better understand the relationship between cytokines and PEDV replication, in this study, pro-inflammatory cytokine and chemokine expression profiles in Vero cells infected with PEDV were analyzed. Real-time quantitative PCR assay indicated that IL-1α, IL-1ß, TNF-α, CCL2, CCL5 and CXCL8 expression levels were significantly upregulated. Moreover, overexpression and siRNA silencing assays showed that overexpression of IL-1α, IL-1ß, TNF-α, CCL2, CCL5 and CXCL8 could significantly inhibit PEDV replication, while silencing of IL-1α, IL-1ß, TNF-α, CCL2, CCL5 and CXCL8 could significantly promote PEDV replication. Finally, a dual-luciferase reporter assay showed that nsp4 contributed to the expression of IL-1α, IL-1ß, TNF-α, CCL2, CCL5 and CXCL8 via the NF-κB pathway. Together, these data determined that PEDV nsp4 could upregulate pro-inflammatory cytokine and chemokine expression, inhibiting viral replication in vitro. These results provided novel insights for understanding the roles of cytokines in PEDV replication.

Constitutive expression of antimicrobial peptide PR-39 in transgenic mice significantly enhances resistance to bacterial infection and promotes growth.

Use of huge amounts of antibiotics in farm animal production has promoted the prevalence of antibiotic-resistant bacteria, which poses a serious threat to public health. Therefore, alternative approaches are needed to reduce or replace antibiotic usage in the food animal industry. PR-39 is a pig-derived proline-rich antimicrobial peptide that has a broad spectrum of antibacterial activity and a low propensity for development of resistance by microorganisms. To test whether ubiquitous expression of PR-39 in transgenic (TG) mice can increase resistance against bacterial infection, we generated TG mice that ubiquitously express a pig-derived antimicrobial peptide PR-39 and analyzed their growth and resistance to infection of the highly pathogenic Actinobacillus pleuropneumoniae (APP) isolated from swine. The growth performance was significantly increased in TG mice compared with their wild-type (WT) littermates. After the APP challenge, TG mice exhibited a significantly higher survival rate and significantly lower tissue bacterial load than WT littermates. Furthermore, the tissue lesion severity that resulted from APP infection was milder in TG mice than that in their WT littermates. This study provides a good foundation for the development of PR-39-expressing TG animals, which could reduce the use of antibiotics in the farm animal industry.

A new recombined porcine reproductive and respiratory syndrome virus virulent strain in China.

Porcine reproductive and respiratory syndrome (PRRS) is one of the most important swine diseases worldwide. In the present study, a new virulent strain of PRRS virus (PRRSV), GDsg, was isolated in Guangdong province, China, and caused high fever, high morbidity, and high mortality in sows and piglets. The genome of this new strain was 15,413 nucleotides (nt) long, and comparative analysis revealed that GDsg shared 82.4% to 94% identity with type 2 PRRSV strains, but only 61.5% identity with type 1 PRRSV Lelystad virus strain. Phylogenetic analysis indicated that type 2 PRRSV isolates include five subgenotypes (I, II, III, IV, and V), which are represented by NADC30, VR-2332, GM2, CH-1a, and HuN4, respectively. Moreover, GDsg belongs to a newly emerging type 2 PRRSV subgenotype III. More interestingly, the newly isolated GDsg strain has multiple discontinuous nt deletions, 131 (19 + 18 + 94) at position 1404-1540 and a 107 nt insertion in the NSP2 region. Most importantly, the GDsg strain was identified as a virus recombined between low pathogenic field strain QYYZ and vaccine strain JXA1-P80. In conclusion, a new independent subgenotype and recombinant PRRSV strain has emerged in China and could be a new threat to the swine industry of China.

Identification and characterization of atypical porcine pestivirus genomes in newborn piglets with congenital tremor in China.

Recently, a novel atypical porcine pestivirus (APPV) in pig was reported. In this study, two APPV strains, APPV-China/GZ01/2016 (GZ01) and APPV-China/GD-SD/2016 (GD-SD), were identified in two newborn piglet herds with congenital tremor from China. The open reading frame of the two strains shared an 83.5% nucleotide identity. Phylogenetically, the APPV strains were placed into two groups: GZ01 belonged to group I and GD-SD belonged to group II. A high viral load was detected in the cerebellum (quantification cycles ＜ 26). Further studies should be carried out to thoroughly elucidate the development of congenital tremors caused by APPV.