The Significance of the 98th Amino Acid in GP2a for Porcine Reproductive and Respiratory Syndrome Virus Adaptation in Marc-145 Cells.

Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most important pathogens in the pig industry. Marc-145 cells are widely used for PRRSV isolation, vaccine production, and investigations into virus biological characteristics. Despite their significance in PRRSV research, Marc-145 cells struggle to isolate specific strains of the North American virus genotype (PRRSV-2). The involvement of viral GP2a, GP2b, and GP3 in this phenomenon has been noted. However, the vital amino acids have not yet been identified. In this study, we increased the number of blind passages and successfully isolated two strains that were previously difficult to isolate with Marc-145 cells. Both strains carried an amino acid substitution in GP2a, specifically phenylalanine to leucine at the 98th amino acid position. Through a phylogenetic and epidemiologic analysis of 32 strains, those that were not amenable to isolation widely exhibited this mutation. Then, by using the PRRSV reverse genetics system, IFA, and Western blotting, we identified the mutation that could affect the tropism of PRRSV-2 for Marc-145 cells. Furthermore, an animal experiment was conducted. Through comparisons of clinical signs, mortality rates, and viral load in the organs and sera, we found that mutation did not affect the pathogenicity of PRRSV-2. In conclusion, our study firmly establishes the 98th amino acid in GP2a as a key determinant of PRRSV-2 tropism for Marc-145 cells.

Base Excision DNA Repair in Plants: Arabidopsis and Beyond.

Base excision DNA repair (BER) is a key pathway safeguarding the genome of all living organisms from damage caused by both intrinsic and environmental factors. Most present knowledge about BER comes from studies of human cells, E. coli, and yeast. Plants may be under an even heavier DNA damage threat from abiotic stress, reactive oxygen species leaking from the photosynthetic system, and reactive secondary metabolites. In general, BER in plant species is similar to that in humans and model organisms, but several important details are specific to plants. Here, we review the current state of knowledge about BER in plants, with special attention paid to its unique features, such as the existence of active epigenetic demethylation based on the BER machinery, the unexplained diversity of alkylation damage repair enzymes, and the differences in the processing of abasic sites that appear either spontaneously or are generated as BER intermediates. Understanding the biochemistry of plant DNA repair, especially in species other than the Arabidopsis model, is important for future efforts to develop new crop varieties.

Comparative Ubiquitination Proteomics Revealed the Salt Tolerance Mechanism in Sugar Beet Monomeric Additional Line M14.

Post-translational modifications (PTMs) are important molecular processes that regulate organismal responses to different stresses. Ubiquitination modification is not only involved in human health but also plays crucial roles in plant growth, development, and responses to environmental stresses. In this study, we investigated the ubiquitination proteome changes in the salt-tolerant sugar beet monomeric additional line M14 under salt stress treatments. Based on the expression of the key genes of the ubiquitination system and the ubiquitination-modified proteins before and after salt stress, 30 min of 200 mM NaCl treatment and 6 h of 400 mM NaCl treatment were selected as time points. Through label-free proteomics, 4711 and 3607 proteins were identified in plants treated with 200 mM NaCl and 400 mM NaCl, respectively. Among them, 611 and 380 proteins were ubiquitinated, with 1085 and 625 ubiquitination sites, in the two salt stress conditions, respectively. A quantitative analysis revealed that 70 ubiquitinated proteins increased and 47 ubiquitinated proteins decreased. At the total protein level, 42 were induced and 20 were repressed with 200 mM NaCl, while 28 were induced and 27 were repressed with 400 mM NaCl. Gene ontology, KEGG pathway, protein interaction, and PTM crosstalk analyses were performed using the differentially ubiquitinated proteins. The differentially ubiquitinated proteins were mainly involved in cellular transcription and translation processes, signal transduction, metabolic pathways, and the ubiquitin/26S proteasome pathway. The uncovered ubiquitinated proteins constitute an important resource of the plant stress ubiquitinome, and they provide a theoretical basis for the marker-based molecular breeding of crops for enhanced stress tolerance.

Genome-wide identification of CBF genes and their responses to cold acclimation in Taraxacum kok-saghyz.

C-repeat binding factors (CBFs) are transcription factors that are known to play important roles in plant cold acclimation. They are highly conserved in most higher plants. Taraxacum kok-saghyz (TKS) is an herb native to China and Kazakhstan and is well-known for its production of rubber silk with industrial and economic value. To understand cold acclimation mechanisms, we conducted a genome-wide discovery of the CBF family genes in TKS and revealed ten CBF genes. A bioinformatic analysis of the CBF genes was carried out to analyze the phylogenetic relationship, protein conservative motifs, protein physicochemical properties, gene structure, promoter cis-acting elements, and the gene expression patterns under cold acclimation and control conditions. It was found that most of these genes were highly responsive at the late stage of cold acclimation, indicating that they play important roles in the cold acclimation processes of TKS. This study provides a theoretical basis for the study of the molecular functions of the CBF gene family in TKS, and a useful guidance for the genetic improvement of the cold tolerance traits of TKS and other plants, including crops.

A novel amino acid site of N protein could affect the PRRSV-2 replication by regulating the viral RNA transcription.

BACKGROUND: Finding the key amino acid sites that could affect viral biological properties or protein functions has always been a topic of substantial interest in virology. The nucleocapsid (N) protein is one of the principal proteins of the porcine reproductive and respiratory syndrome virus (PRRSV) and plays a vital role in the virus life cycle. The N protein has only 123 or 128 amino acids, some of key amino acid sites which could affect the protein functions or impair the viral biological characteristics have been identified. In this research, our objective was to find out whether there are other novel amino acid sites of the N protein can affect N protein functions or PRRSV-2 replication. RESULTS: In this study, we found mutated the serine78 and serine 99of the nucleocapsid (N) protein can reduce the N-induced expression of IL-10 mRNA; Then, by using reverse genetics system, we constructed and rescued the mutant viruses, namely, A78 and A99.The IFA result proved that the mutations did not affect the rescue of the PRRSV-2. However, the results of the multistep growth kinetics and qPCR assays indicated that, compared with the viral replication ability, the titres and gRNA levels of A78 were significantly decreased compared with the wild-type. Further study showed that a single amino acid change from serine to alanine at position 78 of the N protein could abrogates the level of viral genomic and subgenomic RNAs. It means the mutation could significant decrease the viral replication efficiency in vitro. CONCLUSIONS: Our results suggest that the serine78 of N protein is a key site which could affect the N protein function and PRRSV replication ability.

miR-223-3p contributes to suppressing NLRP3 inflammasome activation in Streptococcus equi ssp. zooepidemicus infection.

Streptococcus equi subsp. zooepidemicus (SEZ) is an essential pathogen in a range of species, causing a worldwide variety of diseases, such as meningitis, endocarditis, and septicaemia. Studies have shown that microRNAs (miRNAs), which regulate target genes at the post-transcriptional level, play an important regulatory role in the organism. In this study, the infection of J774A.1 murine macrophages with SEZ up-regulated NLRP3 inflammasome and downstream pathways accompanied by miR-223-3p down-regulation. Through computational prediction and experimental confirmation, we have shown that miR-223-3p directly targets the NLRP3 mRNA. Consequently, overexpression of miR-223-3p suppressed NLRP3 inflammasome activation and downstream pathways in response to SEZ infection. The miR-223-3p inhibitor exhibited the opposite effect, causing hyperactivation of NLRP3 inflammation activation and downstream pathways. Additionally, we further demonstrated that miRNA-223-3p inhibited the secretion of IL-1ß and IL-18 by regulating the NLRP3/caspase-1 pathway. Furthermore, intravenous administration of miR-223-3p significantly decreased inflammation in mice in response to SEZ. In conclusion, our results demonstrated that miR-223-3p contributes to suppressing the NLRP3 inflammasome activation in SEZ infection, contributing novel evidence to identify a therapeutic target for treating SEZ.

Roles of E3 Ubiquitin Ligases in Plant Responses to Abiotic Stresses.

Plants are frequently exposed to a variety of abiotic stresses, such as those caused by salt, drought, cold, and heat. All of these stressors can induce changes in the proteoforms, which make up the proteome of an organism. Of the many different proteoforms, protein ubiquitination has attracted a lot of attention because it is widely involved in the process of protein degradation; thus regulates many plants molecular processes, such as hormone signal transduction, to resist external stresses. Ubiquitin ligases are crucial in substrate recognition during this ubiquitin modification process. In this review, the molecular mechanisms of plant responses to abiotic stresses from the perspective of ubiquitin ligases have been described. This information is critical for a better understanding of plant molecular responses to abiotic stresses.

Functional Characterization of Sugar Beet M14 Antioxidant Enzymes in Plant Salt Stress Tolerance.

Salt stress can cause cellular dehydration, which induces oxidative stress by increasing the production of reactive oxygen species (ROS) in plants. They may play signaling roles and cause structural damages to the cells. To overcome the negative impacts, the plant ROS scavenging system plays a vital role in maintaining the cellular redox homeostasis. The special sugar beet apomictic monosomic additional M14 line (BvM14) showed strong salt stress tolerance. Comparative proteomics revealed that six antioxidant enzymes (glycolate oxidase (GOX), peroxiredoxin (PrxR), thioredoxin (Trx), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), and dehydroascorbate reductase3 (DHAR3)) in BvM14 were responsive to salt stress. In this work, the full-length cDNAs of genes encoding these enzymes in the redox system were cloned from the BvM14. Ectopic expression of the six genes reduced the oxidative damage of transgenic plants by regulating the contents of hydrogen peroxide (H2O2), malondialdehyde (MDA), ascorbic acid (AsA), and glutathione (GSH), and thus enhanced the tolerance of transgenic plants to salt stress. This work has charecterized the roles that the antioxidant enzymes play in the BvM14 response to salt stress and provided useful genetic resources for engineering and marker-based breeding of crops that are sensitive to salt stress.

Functional Characterization of a Sugar Beet BvbHLH93 Transcription Factor in Salt Stress Tolerance.

The basic/helix-loop-helix (bHLH) transcription factor (TF) plays an important role for plant growth, development, and stress responses. Previously, proteomics of NaCl treated sugar beet leaves revealed that a bHLH TF, BvbHLH93, was significantly increased under salt stress. The BvbHLH93 protein localized in the nucleus and exhibited activation activity. The expression of BvbHLH93 was significantly up-regulated in roots and leaves by salt stress, and the highest expression level in roots and leaves was 24 and 48 h after salt stress, respectively. Furthermore, constitutive expression of BvbHLH93 conferred enhanced salt tolerance in Arabidopsis, as indicated by longer roots and higher content of chlorophyll than wild type. Additionally, the ectopic expression lines accumulated less Na+ and MDA, but more K+ than the WT. Overexpression of the BvBHLH93 enhanced the activities of antioxidant enzymes by positively regulating the expression of antioxidant genes SOD and POD. Compared to WT, the overexpression plants also had low expression levels of RbohD and RbohF, which are involved in reactive oxygen species (ROS) production. These results suggest that BvbHLH93 plays a key role in enhancing salt stress tolerance by enhancing antioxidant enzymes and decreasing ROS generation.

Mechanisms of Sugar Beet Response to Biotic and Abiotic Stresses.

Sugar beet is used not only in the sugar production, but also in a wide range of industries including the production of bioethanol as a source of renewable energy, extraction of pectin and production of molasses. The red beetroot has attracted much attention as health-promoting and disease-preventing functional food. The negative effects of environmental stresses, including abiotic and biotic ones, significantly decrease the cash crop sugar beet productivity. In this paper, we outline the mechanisms of sugar beet response to biotic and abiotic stresses at the levels of physiological change, the genes' functions, transcription and translation. Regarding the physiological changes, most research has been carried out on salt and drought stress. The functions of genes from sugar beet in response to salt, cold and heavy metal stresses were mainly investigated by transgenic technologies. At the transcriptional level, the transcriptome analysis of sugar beet in response to salt, cold and biotic stresses were conducted by RNA-Seq or SSH methods. At the translational level, more than 800 differentially expressed proteins in response to salt, K+/Na+ ratio, iron deficiency and resupply and heavy metal (zinc) stress were identified by quantitative proteomics techniques. Understanding how sugar beet respond and tolerate biotic and abiotic stresses is important for boosting sugar beet productivity under these challenging conditions. In order to minimize the negative impact of these stresses, studying how the sugar beet has evolved stress coping mechanisms will provide new insights and lead to novel strategies for improving the breeding of stress-resistant sugar beet and other crops.

Insights into the evolutionary history and epidemiological characteristics of the emerging lineage 1 porcine reproductive and respiratory syndrome viruses in China.

The newly emerged lineage 1 porcine reproductive and respiratory syndrome viruses (PRRSVs) (especially the NADC30-like and NADC34-like viruses) have posed a direct threat to the Chinese pig industry since 2013. The phylogenetic, epidemic, and recombinant properties of these viruses have not yet systematically analysed in China. This report presents regular surveillance and field epidemiological studies for PRRSV across China from 2007 to 2019. From over 4,000 detected clinical samples, 70 open reading frame five sequences and four complete genomes of lineage 1 viruses were successfully obtained. Combined with global data, we conducted an extensive and systematic molecular phylogeny analysis using a maximum likelihood tree. The Chinese lineage 1 viruses were clustered, and their temporal and spatial distribution was further explored. Multiple viral introductions of lineage 1 virus from the United States to China were detected, and some became endemic in China. There are three sub-lineage 1 clusters: lineage 1.5 (NADC34-like), lineage 1.6 and New Intro cluster (NADC30-like). These viruses show high genetic diversity and a wide distribution in China, with Henan Province showing the highest diversity. Moreover, Chinese lineage 1 viruses have developed an endemic NADC30-like cluster. The demographic feature of this cluster showed a more or less constant population expansion history with a recent decreasing trend. Moreover, the genome recombination of Chinese lineage 1 with two dominant clusters (Chinese HP-PRRSVs: lineage 8.7 and VR2332-like: lineage 5.1) was frequently detected, both of which have commercial vaccine strains available. Furthermore, recombination hotspots were discovered near NSP9 and ORF2-4 regions of the genome. Overall, these findings provide important insights into the evolution and geographical diversity of Chinese lineage 1 PRRSV. These results will facilitate the development of programmes for the control and prevention of the emerging lineage 1 viruses in China.

Whole genome sequence and comparative genome analyses of multi-resistant Staphylococcus warneri GD01 isolated from a diseased pig in China.

Staphylococcus warneri is a coagulase-negative staphylococcus that is a normal inhabitant of the skin. It is also considered to be an opportunistic etiological agent causing significant infections in human and animals. Currently, relatively little attention has been paid to the genome biology of S. warneri pathogenicity and antibiotic resistance, which are emerging issues for this etiological agent with considerably clinical significance. In this study, we determined the complete genome sequence of S. warneri strain GD01 recovered from the sampled muscle abscess tissue of a diseased pig in South China. The genome of S. warneri is composed of a circular chromosome of 2,473,911 base pairs as well as eight plasmid sequences. Genome-wide metabolic reconstruction revealed 82 intact functional modules driving the catabolism of respiration and fermentation for energy production, uptake of distinct sugars as well as two-component regulatory systems. The evidence uncovered herein enables better understanding for metabolic potential and physiological traits of this etiological agent. The antibiotic susceptibility test demonstrated that S. warneri GD01 was resistant to penicillin, amoxicillin, ampicillin, cefalexin, vancomycin, and sulfisoxazole. The associations between antibiotic phenotypes and the related genotypes were identified to reveal the molecular basis conferring resistance to this pathogen. A number of genes coding for potential virulence factors were firstly depicted in the genome of S. warneri GD01, including adhesins, exoenzymes, capsule, and iron acquisition proteins. Our study provides a valuable genomic context of the genes/modules devoting to metabolism, antibiotic resistance, and virulence of S. warneri.

A novel tumour suppressor lncRNA F630028O10Rik inhibits lung cancer angiogenesis by regulating miR-223-3p.

Lung cancer is the world's leading cause of cancer-related morbidity and mortality despite advances in surgery, chemotherapy and immunotherapy; thus, there is an urgent need to find new molecules to develop novel treatment strategies. Although ncRNAs were found to account for 98% transcripts, the number of lncRNAs with distinct function in lung cancer is extremely limited. We previously demonstrated that Plasmodium infection inhibits tumour growth and metastasis, but the exact mechanisms involved have not been fully understood. In this study, we carried out RNA sequencing (RNA-Seq) of tumour tissues isolated from LLC tumour-bearing mice treated with either Plasmodium yoelli (Py)-infected red blood cells or uninfected red blood cells. We found that F630028O10Rik (abbreviated as F63) is a novel lncRNA that was significantly up-regulated in tumours isolated from mice treated with Py-infected red blood cells compared to the control. By using gene silencing technique, F63 was found to inhibit both tumour Vascular Endothelial Growth Factor A (VEGFA) secretion and endothelial cells clone formation, migration, invasion and tube formation. Injection of cholesterol-modified siRNA-F63 into mice tumour tissues produced a significant increase in tumour volume, blood vessel formation and angiogenesis 17 days after injection. We further showed that inhibiting miR-223-3p results in the down-regulation of VEGFA and VEGFR2 which are vital molecules for angiogenesis. These results reveal that F63 inhibit tumour growth and progression by modulating tumour angiogenesis suggesting F63 can be a novel lncRNA with great potential as a candidate molecule for gene therapy in lung cancer.

First report and genetic diversity of porcine bufavirus in China.

BACKGROUND: Bufavirus is a newly discovered zoonotic virus reported in numerous mammals and humans. However, the epidemiological and genetic characteristics of porcine bufaviruses (PBuVs) in China remain unclear. METHODS: To detect PBuVs in China, 384 samples (92 fecal and 292 serum specimens) were collected from 2017 to 2018, covering six provinces in China, and were evaluated by nested PCR. Further, the positive samples from different provinces were selected to obtain the complete genome of Chinese PBuVs. RESULTS: The prevalence rate of PBuV was 16.7% in Chinese domestic pigs in the Guangdong, Guangxi, Fujian, Jiangxi, Anhui, and Henan provinces. Additionally, the positive rate of fecal specimens was higher than that of the serum samples. Next, we sequenced nine near-complete genomes of Chinese field PBuV strains from different provinces. Homology and phylogenetic analyses indicated that Chinese PBuVs have high genetic variation (93.3-99.2%), showed higher nucleotide identity with an Austrian PBuV strain (KU867071.1), and developed into different branches within the same cluster. CONCLUSION: To our knowledge, this is the first report on PBuV in China, expanding the geographic boundaries of PBuV circulation. Our data demonstrate that PBuVs are widely distributed in the six Chinese provinces. Moreover, these Chinese PBuVs exhibit genetic variation and continuous evolution characteristics. Taken together, our findings provide a foundation for future studies on bufaviruses.

Phylogeography, phylodynamics and the recent outbreak of lineage 3 porcine reproductive and respiratory syndrome viruses in China.

Novel highly pathogenic porcine reproductive and respiratory syndrome viruses (PRRSVs) have attracted increasing attention owing to their continual high emergence and recent re-emergence. Recently, lineage 3 PRRSVs, belonging to the type 2 viruses, with novel characteristics and increased virulence have been continuously re-emerging in China, thereby posing a great threat to pig farming. However, available information about lineage 3 is limited. Here, we carried out molecular epidemiological investigations for PRRSV surveillance in most regions of China from 2007 to 2017. More than 3,000 samples were obtained, amounting to 73 sequences of lineage 3 viruses. The origin, demographic history and spread pattern of lineage 3 PRRSVs were investigated combining with the database globally. Phylogeography and phylodynamic analyses within a Bayesian statistical framework revealed that lineage 3 viruses originated in Taiwan. Followed by subsequent propagation to different areas and geography, it dichotomized into two endemic clusters. South China has become an epicentre for these viruses, which diffused into China's interiors in recent years. Furthermore, viral dispersal route analysis revealed the risk of viral diffusion. Overall, the origin, epidemic history and geographical evolution of lineage 3 PRRSVs were comprehensively analysed in this study. In particular, the epicentre of southern China and the diffusion routines of the viruses are highlighted in this study, and the possible continuous transmission of the novel lineages poses the biggest threat to pig farmers.

The phosphorylation of the N protein could affect PRRSV virulence in vivo.

The porcine respiratory and reproductive syndrome virus (PRRSV) nucleocapsid (N) protein is a multiphosphorylated protein.It has been proved that the phosphorylation of N protein could regulate the growth ability of PRRSV in Marc-145 cells. However, further investigation is needed to determine whether phosphorylation of the N protein could affect PRRSV virulence in piglets. In this study, we confirmed that the mutations could impair PRRSV replication ability in porcine primary macrophages (PAMs) as they did in Marc-145 cells. The animal experiments suggested that the pathogenicity of the mutated virus (A105-120) was significantly reduced compared with parent strain (XH-GD). Our results suggested that the phosphorylation of the N protein contributes to virus replication and virulence. This study is the first to identify a specific modification involved in PRRSV pathogenicity. Mutation of PTMs sites is also a novel way to attenuate PRRSV virulence. The mutations could be a marker in a vaccine. In conclusion, our study will improve our understanding of the molecular mechanisms of PRRSV pathogenicity.

Overexpression of a S-Adenosylmethionine Decarboxylase from Sugar Beet M14 Increased Araidopsis Salt Tolerance.

Polyamines play an important role in plant growth and development, and response to abiotic stresses. Previously, differentially expressed proteins in sugar beet M14 (BvM14) under salt stress were identified by iTRAQ-based quantitative proteomics. One of the proteins was an S-adenosylmethionine decarboxylase (SAMDC), a key rate-limiting enzyme involved in the biosynthesis of polyamines. In this study, the BvM14-SAMDC gene was cloned from the sugar beet M14. The full-length BvM14-SAMDC was 1960 bp, and its ORF contained 1119 bp encoding the SAMDC of 372 amino acids. In addition, we expressed the coding sequence of BvM14-SAMDC in Escherichia coli and purified the ~40 kD BvM14-SAMDC with high enzymatic activity. Quantitative real-time PCR analysis revealed that the BvM14-SAMDC was up-regulated in the BvM14 roots and leaves under salt stress. To investigate the functions of the BvM14-SAMDC, it was constitutively expressed in Arabidopsis thaliana. The transgenic plants exhibited greater salt stress tolerance, as evidenced by longer root length and higher fresh weight and chlorophyll content than wild type (WT) under salt treatment. The levels of spermidine (Spd) and spermin (Spm) concentrations were increased in the transgenic plants as compared with the WT. Furthermore, the overexpression plants showed higher activities of antioxidant enzymes and decreased cell membrane damage. Compared with WT, they also had low expression levels of RbohD and RbohF, which are involved in reactive oxygen species (ROS) production. Together, these results suggest that the BvM14-SAMDC mediated biosynthesis of Spm and Spd contributes to plant salt stress tolerance through enhancing antioxidant enzymes and decreasing ROS generation.

CD44 facilitates adherence of Streptococcus equi subsp. zooepidemicus to LA-4 cells.

Streptococcus equi subsp. zooepidemicus (S. zooepidemicus) causes a wide variety of infections in many species. CD44 is a transmembrane adhesion molecule, expressed by various cell types, which has been implicated in several infection processes. The aim of this study was to examine the role of CD44 in S. zooepidemicus adherence to LA-4 cells (mouse lung adenoma). Dose-dependent adhesion with LA-4 may be effectively studied by flow cytometry. Adherence of S. zooepidemicus is reduced after treatment of cells with anti-CD44 antibody. Treatment of S. zooepidemicus with recombinant CD44 significantly reduced bacteria adherence. In addition, CD44 can directly bind to wild-type S. zooepidemicus, while the binding was decreased in the capsule deletion isogenic mutant. These data suggest that CD44 facilitates adherence of S. zooepidemicus to LA-4 cells.

Emergence of novel recombination lineage 3 of porcine reproductive and respiratory syndrome viruses in Southern China.

Lineage 3 of porcine reproductive and respiratory syndrome viruses, which belong to North America type 2, has a long epidemic history in China. The novel lineage 3 viruses constantly emerging in recent years are characterized by a high detection rate and significant pathogenicity. In this study, we investigated the prevalence of lineage 3 in southern China and selected two isolated strains for genome and virulence analyses. A cross-sectional epidemiology investigation indicated that the prevalence of lineage 3 antigens was 35.68% (95% CI: 27.6-44.3%) among 227 samples collected from over 100 infected farms from January 2016 to July 2017 in southern China. Two novel isolates of lineage 3 were selected. After 20 passages, Marc-145 cells were not susceptible to those viruses. Full-length genome analysis indicated that the two strains share 95.2% homology with each other and 95.7%-96.2% with highly pathogenic porcine reproductive and respiratory syndrome viruses (HP-PRRSVs; JXA1-like strain, lineage 8.7). Phylogenetic and molecular evolutionary results showed that for the two isolates, HP-PRRSV provides most of the ORF1 gene. Animal experiment revealed discrepancies in virulence between the strains. Although challenge resulted in 100% morbidity, the isolate carrying most of the HP-PRRSV ORF1 caused severe clinical symptoms and 40% mortality, whereas the other isolate containing part of the ORF1 gene caused no mortality. Overall, these findings suggest that lineage 3 viruses might be commonly circulating in most of southern China. Frequent recombination events within HP-PRRSVs of this lineage with changing virulence could represent potential threats to the pig industry.

Characterization of SeseC_01411 as a surface protective antigen of Streptococcus equi ssp. zooepidemicus.

Streptococcus equi ssp. zooepidemicus (Streptococcus zooepidemicus, SEZ) is a commensal bacterium related to opportunistic infections of many species, including humans, dogs, cats, and pigs. SeseC_01411 has been proven to be immunogenic. However, its protective efficacy remained to be evaluated. In the present study, the purified recombinant SeseC_01411 could elicit a strong humoral antibody response and protect against lethal challenge with virulent SEZ in mice. Our finding confirmed that SeseC_01411 distributes on the surface of SEZ. In addition, the hyperimmune sera against SeseC_01411 could efficiently kill the bacteria in the phagocytosis test. The present study identified the immunogenic protein, SeseC_01411, as a novel surface protective antigen of SEZ.