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A member of the family Coronaviridae, genus alphacoronavirus, porcine epidemic diarrhea virus (PEDV) is an enveloped, single-stranded positive-sense RNA virus (1). PEDV is the major causative agent of porcine epidemic [...]

Abstract Background Extraintestinal pathogenic Escherichia coli (ExPEC) can cause a variety of infections outside the gastrointestinal tract in humans and animals. Infections due to swine ExPECs have been occurring with increasing frequency in China. These ExPECs may now be considered a new food-borne pathogen that causes cross-infections between humans and pigs. Knowledge of the clonal structure and virulence genes is needed as a framework to improve the understanding of phylogenetic traits of porcine ExPECs. Results Multilocus sequence typing (MLST) data showed that the isolates investigated in this study could be placed into four main clonal complexes, designated as CC10, CC1687, CC88 and CC58. Strains within CC10 were classified as phylogroup A, and these accounted for most of our porcine ExPEC isolates. Isolates in the CC1687 clonal complex, formed by new sequence types (STs), was classified as phylogroup D, with CC88 isolates considered as B2 and CC58 isolates as B1. Porcine ExPECs in these four clonal complexes demonstrated significantly different virulence gene patterns. A few porcine ExPECs were indentified in phylogroup B2, the phylogroup in which human ExPECs mainly exist. However some STs in the four clonal groups of porcine ExPECs were reported to cause extraintestinal infections in human, based on data in the MLST database. Conclusion Porcine ExPECs have different virulence gene patterns for different clonal complexes. However, these strains are mostly fell in phylogenentic phylogroup A, B1 and D, which is different from human ExPECs that concentrate in phylogroup B2. Our findings provide a better understanding relating to the clonal structure of ExPECs in diseased pigs and indicate a need to re-evaluate their contribution to human ExPEC diseases.

Pasteurella multocida is a leading cause of respiratory disease in pigs worldwide. In this study, we determined the genetic characteristics of 115 P. multocida isolates from the lungs of pigs with respiratory disease in China in 2015 using capsular typing, lipopolysaccharide (LPS) genotyping, and virulence genotyping based on the detection of virulence-associated genes. The results showed that the isolates belonged to three capsular types: A (49.6%), D (46.1%), and nontypable (4.3%); and two LPS genotypes: L3 (22.6%) and L6 (77.4%). When combining the capsular types with the LPS genotypes, a genotype group D: L6 (46.1%) was the most prevalent among the strains. Among the 23 virulence-associated genes detected in this study, a small number of them displayed a certain level of 'genotype-preference'. We found that pfhA, hgbA, and hgbB had a close association with P. multocida LPS genotypes, while tadD was more associated with P. multocida capsular types. In addition, multilocus sequence typing (MLST) on 40 P. multocida isolates identified four sequence types: ST3, ST10, ST11, and ST16, and the distribution of ST11 was significantly higher than the other MLST genotypes. Interestingly, all of the ST11 isolates detected in this study were genotype D: L6 strains and they were 100% positive for hgbB. Our data suggest that a capsule/LPS/MLST genotype D/L6/ST11 is likely to be strongly associated with respiratory clinical manifestation of the disease in pigs. [ABSTRACT FROM AUTHOR]

Objective: Glutamyl tRNA Synthetase (Gts) is a protease which catalyzes esterification between tRNA and glutamine. The immunogenicity of Gts was evaluated through immunization and challenge experiment., Methods and Results: We cloned gts from the genome of SC19, and inserted it into prokaryotic expression plasmid pET28a-gts. The recombinant vector was transformed into E. coli BL21. Induced by IPTG, one 58 kD protein, was expressed and purified by using Ni - NTA column (Novagen). The purity of rGtS was 93.3% and the concentration of purified protein was 433 microg/mL. We proved the immunogenicity of recombinant protein rGtS by western blot analysis. We immunized Balb/c mice with rGtS and Freund's adjuvant, and after two boost vaccinations, all mice were challenged with 4 times LD50 amount of SC19 (1.2 x 10(9) CFU). The survive rate of vaccination group is 50% (4/8), significantly higher than blank vector control group (1/8)., Conclusion: These results proved that GtS has certain immunogenicity and can offer partial protection against high dose challenge. Therefore Gts could be a potential candidate of subunit vaccine against Streptococcus suis.

Salmonella enterica serovar Choleraesuis strain C500 is a live, attenuated vaccine that has been used in China for over 40 years to prevent piglet paratyphoid. The objective of this study was to evaluate the potential of attenuated Salmonella enterica serovar Choleraesuis C500 strain with a delta asd mutant as an effective live vaccine vector by the Asd+ balanced-lethal host-vector system. Here, we compared the characteristics of S. enterica serovar Choleraesuis delta asdC500 strain with the parent C500 strain, including phenotype, growth rate, virulence, safety, and expression for heterologous antigen. The mean generation times of delta asdC500 mutant, the vector control delta asdC500 (pYA3493), and the parent avirulent C500 vaccine strain in Luria broth were 30.7, 28.1, and 27.9 min, respectively. The fermentation patterns of theses three strains on different carbohydrates, and the levels of production of H2S, were similar. The O and H antigens of delta asdC500 mutant, delta asdC500 (pYA3493) and delta asdC500 (pYA-F1P2) were 6,7:C:1,5, identical to the parent strain C500. By the method of Reed and Muench, groups of mice were challenged by the intraperitoneal route with different amounts of delta asdC500 (pYA3493) or the parent C500 strain, and the virulence of delta asdC500 (pYA3493) with LD50 of 1.1 x 10(7) CFU was a little lower than C500 with LD50 of 4.4 x 10(6) CFU. All piglets inoculated with delta asdC500 (pYA3493) or C500 survived, and no signs of disease were observed during the entire experimental period. No major differences were found in these two groups. In addition, the recombinant pYA-F1P2 plasmid was very stable in the recombinant delta asdC500 (pYA-F1P2) strain, which expressed secretorily a large amount of the recombinant filamentous hemagglutinin type I domain and pertactin region 2 domain antigen (rF1P2) of Bordetella bronchiseptica. In this study, we have shown that the delta asdC500 mutant had a series of biological characteristics similar to the parent vaccine strain C500. Furthermore, the strain could express secretorily a large amount of heterologous antigen. It is likely that this Salmonella expression and delivery system could be easily adapted to develop multivalent recombinant Salmonella vaccines against infectious agents using the Asd+ balanced-lethal host-vector system.

Objective: We developed an indirect ELISA method for detecting Bordetella bronchiseptica (Bb) pertactin antibodies based on the recombinant pertactin protein expressed in Escherichia coli (DE3) strain., Methods and Results: The prn gene encoding Bb pertactin was fused to the downstream of glutathione S-transferase (GST) of pGEX-KG expression vector, resulting in the fusion expression plasmid pGEX-prn. SDS-PAGE showed that the GST-PRN fusion protein was expressed in high level in BL21 carrying pGEX-prn. The strong reactivity of the GST-PRN fusion protein, specifically with antiserum against porcine Bordetellosis caused by Bb HH0809, was identified by Western blot. The recombinant protein fragment of rPRN was purified from the GST-PRN fusion protein digested by protease thrombin with the purity of 93.1%. The rPRN-based indirect ELISA was developed for detecting antibodies against PRN. The ELISA could detect positive samples in experimentally infected pigs fourteen days post inoculation and the degree of sensitivity was over 4 times higher than the latex agglutination test with the coating antigen of killed Bb. Thirty-two point seven percent of positive samples were detected in 1,229 clinical samples while no false positive results were found in detecting 7 antisera against porcine bacterial diseases. Sera samples from two bordetellosis-positive pig fields were tested by the indirect ELISA method and the results indicated that pigs were infected by Bb during the nursery periods., Conclusion: The assay showed excellent specificity, sensitivity and reduplication, and can be useful for epidemiological survey and clinical diagnosis of swine bordetellosis.

Objective: We evaluated the efficacy of the recombinant pertactin (PRN)-specific active or passive immunization against Bordetella bronchiseptica (Bb) in an aerosol challenge model established by using BALB/c mice., Methods and Results: Mice, immunized subcutaneously with two doses of purified glutathione S-transferase (GST)-PRN protein mixed with an equal volume of Freund's adjuvant, produced robust PRN-specific IgG antibody activity. All 20 mice vaccinated with GST-PRN protein survived aerosol challenge with three times the 50% lethal dose (LD50) of virulent Bb HH0809 compared with 3 of 20 GST protein-treated controls and 4 of 20 PBS-treated controls that survived. Furthermore, we observed complete protection against intraperitoneal challenge with ten times the LD50 of virulent HH0809 strain in mice that were injected intraperitoneally with 0.5 ml rabbit anti-GST-PRN serum. No survivors were observed in mice that received either rabbit anti-GST serum or PBS alone., Conclusion: The recombinant PRN protein had strong immunogenicity against Bb infection.

In this study, five fragments of recombinant subunit Pasteurella multocida toxin (PMT) were constructed. Only pET28a-N1518 and pET28b-C2115 could be expressed efficiently in Escherichia coli. The molecular weight of the fusion proteins was 57 kDa and 78 kDa .Western blot confirmed that the two proteins could specifically react with antiserum against Pasteurella multocida toxin. No mice died after the intraperitoneal administration of these two proteins with the dose of 200 microg per mouse, but Vero cell was pathologically changed after administration of 896ng/mL rPMT-N. The fusion protein of rPMT-N and rPMT-C was purified, and emulsified with Freund's adjuvant in equal volumes to get subunit vaccine. Groups of Kunming mice were immunized subcutaneously twice at interval of two weeks. All mice were challenged intraperitoneally with 8.2 x 10(5) CFU HN-13 strain of T+Pm. The protection efficiency of rPMT-N, rPMT-C and crude PMT against HN-13 strain were 90%, 50% and 80%, respectively. The data revealed that the fusion protein of rPMT-N had immunogenicity and potential for developing a subunit vaccine against PAR in pigs.