This study aims to construct a recombinant vaccine containing the tetanus toxin C frag-ment(HC)with a built-in adjuvant of metallothionein 3(MT-3)and evaluate its immune effect in mice.The gene sequences of MT-3 and HC were fused via a linker to create the pET30a-MT-3-HC recombinant plasmid,which was then transformed into E.coli BL21(DE3)competent cells.The re-combinant plasmid was confirmed through double enzyme digestion.The M3C recombinant protein expression was induced,identified by SDS-PAGE and Western blot,and purified using Ni-NTA af-finity chromatography.Five groups of vaccines,including PBS,HC,TT(tetanus toxoid),M3C,and M3C+CpG(composite adjuvant),were administered to mice via intramuscular injection at 7-day intervals for three immunizations.Blood samples were periodically collected from the tail vein.ELISA was used to measure changes in specific IgG antibody titers in the serum,and on day 28,antibody subtypes(IgG1,IgG2a,IgG2b,IgG3,and IgM)and cytokine levels(IL-4,IFN-γ)were also measured.The results demonstrated that the pET30a-MT-3-HC recombinant plasmid was cor-rectly constructed,and the M3C recombinant protein was highly expressed in the supernatant fol-lowing ultrasonic disruption of the induced bacterial culture,with a single band observed post-puri-fication.ELISA results showed that the titer of specific IgG antibodies in the M3C+CpG group peaked at 3.54×105 14 days after the third immunization,which was 141 times,70 times,and 6.6 times higher than that in HC,TT,and TT groups,respectively.Antibody subtype analysis revealed significantly higher specific antibody subtype titers in the M3C and M3C+CpG groups compared to the PBS,HC,and TT groups(P＜0.05),with the M3 C group showing an IgG1/IgG2a ratio greater than 1,and the M3C+CpG group having an IgG1/IgG2a ratio of approximately 1.Serum concentrations of IFN-γ and IL-4 in the M3C and M3C+CpG groups were also significantly higher than those in the other experimental groups(P＜0.05).These results showed that the recombinant antigen containing MT-3 built-in adjuvant and tetanus toxin C fragment was successfully expressed and showed strong immunogenicity,which laid the experimental foundation for the development of this recombinant vaccine.

We collected the positive serum of Echinococcus granulosus infection in sheep,an inter-mediate host with strong immune response,and used healthy serum as negative control,purified the serum and target protein to capture and enrich the corresponding antigen by immunoprecipita-tion,and obtained target protein-antibody-target protein complex.Mass spectrometry strategies were combined to screen and identify specific antigens associated with Echinococcus granulosus,and the proteins with the highest peptide coverage were analyzed bioinformatically using online prediction software.The results showed that 133 Echinococcus granulosus related proteins were i-dentified by IP-MS.Among them,one protein with peptide coverage≥70％was actin Ⅱ,and three proteins with peptide coverage between 30％to 40％were Ton B box domain containing protein,NADH dehydrogenase(ubiquinone)1 α-subcomplex 2(NADH dehydrogenase[ubiquinone])and lactic dehydrogenase.There were six proteins with 20％to 30％peptide coverage,namely,spli-cing factor 3B subunit 5,tumor protein D52,expressed conserved protein,NADH dehydrogenase(ubiquinone)1 alpha subcomplex 7,inosine-5'-monophosphate dehydrogenase,and aldo keto re-ductase family 1 member B4.Bioinformatics analysis revealed that actin protein has no signal pep-tide,it is probably a non-secretory protein and is subcellularly localized to the cytoskeleton,six op-timal potential antigenic epitopes are present,and the secondary and tertiary structures are consist-ently dominated by α-helices and irregular convolutions.The results indicate that immunoprecipita-tion-mass spectrometry is a high-throughput,simple,rapid and effective method for screening and identifying fine-grained Echinococcus granulosus antigens,which can provide a basis for screening specific molecules for serodiagnostic markers in intermediate host sheep and for the development of novel diagnostic techniques for hydatid diseases.

Two thousand five hundred and sixty swab samples were collected from December 2022 to December 2023 in China.PCR was used to detect FBoV and amplify its VP2 and NS1 gene cod-ing equences,and bioinformatics was used to analyze the genetic diversity of FBoV.The results showed that the total positive rate of FBoV was 4.6％(119/2 560).Genetic variation analysis showed that FBoV existed in a variety of genotypes,and FBOV-1 was the main epidemic type in China.The 15 FBoV-1 strains,four FBoV-2 strains and one FBoV-3 strains identified in this study were genetically close to the strains identified in China,the United States,Thailand,Australia and Portugal.Sequence analysis showed that the identities of amino acid sequence of NS1 and VP2 genes between the sequenced strains and the reference strains were 59.13％-99.25％and 96.41％-100.00％,respectively.The amino acid identities of NS1 and VP2 among the newly sequenced FBoV strains were 60.00％-100.00％and 96.41％-100.00％,respectively,which indicated that the FBov strains circulating in China had great genetic diversity.This study enriched the data for elucidating the epidemic status of FBoV in China,and provided the basis for the subsequent diag-nosis,prevention and control of FBoV.

To construct a recombinant fowl adenovirus 4(FAdV-4)expressing the Cap protein of goose astrovirus genotype 2(GoAstV-2),the expression cassette of Cap gene was inserted into the natural 1 966 bp deletion region of the FAdV-4 genome in the infectious clone p15A-cm-FAdV4-HNJZ.The resulted recombinant plasmid p15A-cm-FAdV4-HNJZ-Cap/GoAstV-2 was linearized with restriction enzyme and transfected into chicken hepatoma cell line(LMH)to rescue the recombinant FAdV-4 expressing the Cap protein of GoAstV-2,rF Ad V4-Cap/GoAstV-2.After 15 passages in LMH cells,the recombinant rFAdV4-Cap/GoAstV-2 was identified by PCR using primers flanking the insertion site of the Cap gene expression cassette and using viral genome DNA extracted from rFAdV4-Cap/GoAstV-2 infected LMH cells as template.LMH cells were in-fected with 15th passage rFAdV4-Cap/GoAstV-2 and indirect immunofluorescence was performed with a polyclonal antibody against Cap protein as the primary antibody.Western blot was carried out with lysates of rFAdV4-Cap/GoAstV-2 infected LMH cells.The in vitro replication dynamic of the 15th passage of the rFAdV4-Cap/GoAstV-2 was also investigated in LMH cells.The results demonstrated that the Cap gene of GoAstV-2 was presented in the genome of the recombinant vi-rus rF AdV4-Cap/Go Ast V-2,and could be expressed stably.The prepared recombinant virus in this study will lay a foundation for developing inactivated bivalent vaccine candidate against co-in-fection of FAdV-4 and GoAstV-2 in goose.

The codon was optimized for the bovine nebovirus(BNeV)VP1 gene and the recombi-nant plasmid pFastBac-Dual-VP1 was constructed,and BNeV-VP1 virus-like particles(VLPs)were prepared using a baculovirus expression system,and identified by Western blot,indirect im-munofluorescence and electron microscopy.Successfully validated VLPs were mixed with MF59 adjuvant and CpG-ODG,and mice were immunised by intramuscular injection and evaluated for immunity effects.The results showed that the optimized CAI(codon adaptation index)of VP1 gene was 0.93 and the GC content was 60.4％.The constructed recombinant plasmid was trans-formed into DH10Bac for blue-white spot screening,and after successful verification,it was trans-fected into SF9 cells to obtain recombinant baculovirus Baculo-BNeV-VP1.BNeV virus-like parti-cles with diameters ranging from 35 to 40 nm were observed under the electron microscope,and both IFA and Western blot experiments proved that the target proteins were successfully ex-pressed and biologically active,and protein optimisation revealed that the highest protein expres-sion was found at the infectious dose MOI=0.5.Mice were immunized by intramuscular injection after 50 μg of VLPs were mixed with MF59 adjuvant and CpG-ODN.The results showed that the VLPs immunization group produced IgG antibodies 7 days after the first dose,and the antibody ti-ter increased gradually,reaching a maximum of 1∶102 400,and declined at 35 d,but still main-tained a high level;The blocking titer BT50 is up to 640,which can induce the production of BNeV VP1-specific blocking antibody in mice.In this study,the baculovirus expression system was used to express the VP1 protein of BNeV,and BNeV VLPs were successfully constructed,which could induce humoral immune response in mice,which provided a reference for the follow-up research of BNeV vaccine.

To explore the in vitro and in vivo synergistic effect of paclitaxel in combination with co-listin against MDREscherichia coli(E.coli)and the corresponding mechanism of synergism,we measured the MICs of PTX alone and combination of PTX+antimicrobial drugs on E.coli and Staphylococcus aureus(S.aureus)by broth microdilution method.Then,checkerboard method was used to determine the FICI of PTX+COL combination,and the antibacterial synergies of PTX and COL was further explored through analyzing the membrane permeability and efflux pump ac-tivity.The MICs results showed that the MIC values of PTX alone against E.coli(G5,E25)and S.aureus S238 were＞1 024 mg/L and 512 mg/L,respectively.Meanwhile,we found that the anti-bacterial activity of COL against E.coli could be significantly enhanced(MIC decreased by 4 to 8 times)when used in combination with PTX.The checkerboard test showed that the FICI values of PTX combined with COL for E.coli(G5,E25)were 0.31 and 0.29,respectively,indicating a synergistic antibacterial effect on these strains.The FICI values of PTX combined with COL for E.coli G21,S.aureus(S237 and S238)were 0.51,0.75 and 0.53,respectively,indicating additive effects on these strains.In the mouse abdominal infection model,the combination group could ex-tremely significantly reduce the bacterial burden of E.coli in abdominal compared to the COL or PTX alone group(P＜0.001).The analysis of membrane permeability and efflux pump activity showed that PTX combined with COL significantly increased the inner and outer membrane per-meability of E.coli(G5 and E25),and markedly inhibited the efflux pumping activity of E.coli,when compared that of PTX and COL alone(P＜0.01).The above results indicated that the com-bination of PTX and COL could exert a synergistic in vivo and in vitro antibacterial effect on COL-resistant E.coli through increasing bacterial membrane permeability and inhibiting efflux pump activity.This study provides the theoretical foundation for the development of a novel combi-nation regimen for the treatment of MDR E.coli infection.

In June 2018,sows at a pig farm in Jiamusi,Heilongjiang Province,suffered a large num-ber of miscarriages,and subsequently weaned piglets at the farm began to show persistent high fe-ver symptoms at around 35 days of age,with some pigs having a fever of more than 41.5 ℃.In or-der to determine the cause of this outbreak,63 clinical samples from this farm were tested.The re-sults showed that 60 out of 63 samples were positive for the porcine reproductive and respiratory syndrome virus(PRRSV)antigen.Subsequently,PRRSV antigen-positive plasmid was transfected into African green monkey embryonic kidney cells(Marc-145),and after three generations of blind transmission,indirect immunofluorescence assay(IFA)was performed.The results showed that one PRRSV strain,named HLJ38,was successfully isolated.Then the whole genome of HLJ38 strain was sequenced and then analyzed in detail by bioinformatics software.Sequence analysis showed that there were three deletions of 131 amino acids(323-433 aa,483 aa and 504-522 aa)in the derived sequence of Nsp2 gene of HLJ38 strain,which was consistent with the molecular ge-netic marker of NADC30 PRRSV.The phylogenetic tree analysis showed that HLJ38 and NADC30 PRRSV in GenBank belong to lineage 1 subgroup,and the nucleotide homology of HLJ38 and NADC30 PRRSV in GenBank was only 85.2％and 84.6％.Recombinant analysis showed that HLJ38 was a recombinant NADC30-like PRRSV,and the recombinant gene fragments were de-rived from multiple strains,among which the fragment of 1-201 nt was provided by VR2332 strain and fragment of 6 641-8 061 nt derived from the HP-PRRSV strain.In summary,the re-sults showed that the outbreak in this pig farm may be caused by the recombination of PRRSV strains among different lineages,and the recombinant circulating strains not only have certain pathogenicity but also suggest that the existing commercial vaccines provide limited cross-protec-tion against them.Recombination between different lineages increases the genetic diversity of PRRSV and aggravates the difficulty of prevention and control of PRRS in pig farms.Therefore,it is necessary to continuously monitor the epidemic dynamics of PRRSV in pig farms and take effec-tive measures in time to curb the spread of PRRS.

In order to understand the epidemic situation of European porcine reproductive and re-spiratory syndrome virus 1(PRRSV1)in Henan Province,molecular epidemiological investigation and virus identification were conducted on clinical specimens from some large-scale pig farms in Henan Province.RT-PCR detection and sequencing were carried out using specific primers for PRRSVI ORF5 gene.As a result,eight PRRSV1 positive samples were detected with six ORF5 gene sequences and one full gene sequence obtained.A strain of PRRSVI named as HENZMD-10 was successfully isolated using PAM cells.Based on the genetic variation analysis,the six ORF5 genes obtained were all PRRSVI.The isolated strains have relatively large ORF5 gene genetic vari-ation,belonging to different branches on the genetic evolution tree.Among them,HENJZ-11,HENJY-7,and HENJY-8 were relatively close in genetic evolution and belonged to the same branch.The genome length of HENZMD-10 isolate was 15 071 bp.Alignment analysis showed that HENZMD-10 strain shared an 89.1％of nucleotide sequence with the LV strain;62.1％and 61.5％with PRRSV2 ATCC-VR2332 strain and the American NADC30 strain,respectively.The nucleotide similarity of HENZMD-10 strain with the domestic JXA1 strain was 61.6％.The phylo-genetic analysis using complete genome sequence showed that HENZMD-10 strain was relatively close to the domestic isolated PRRSV1 NVDC-NM1-2011,LNEU12 and FJEU13 strains.The suc-cessful isolation of one PRRSV1 strain in Henan Province provides the basis for understanding the epidemic dynamics and prevention and control of PRRSV1 in China.

This study aims to establish a convenient,new and visual detection method for the field diagnosis of Pasteurella multocida(Pm).With reference to the Pm kmt1 gene conserved sequence published in GenBank,PCR amplification primers were designed,the amplified kmt1 gene was cloned into pMD19-T vector,and the recombinant plasmid standard pMD19-T-kmt 1 was estab-lished and identified by PCR and sequencing.Using pMD1 9-T-kmt 1 plasmid as template and kmt1 gene as target gene,basic primers were designed and synthesized.According to the requirements of LFD,a probe(Pm-P)was designed,and the RPA-LFD method for Pm detection was established by optimizing the reaction conditions.Specificity and sensitivity tests were carried out,and 64 clini-cal samples were tested by the method.The results showed that the established Pm RPA-LFD method could be amplified at 37 ℃ for 15 min.Escherichia coli(E.coli),Salmonella enteriditis(SE),Riemerella anatipestifer(RA),Staphylococcus,goose parvovirus(GPV),duck plague virus(DPV),Muscovy duck parvovirus(MDPV)DNA was extracted as the template,and plasmid standard pMD19-T-kmt 1 was used as the positive control.All the positive controls were negative,indicating that the method had good specificity.The plasmid standard pMD1 9-T-kmt 1 was diluted with a 10-fold ratio,and the plasmid standard with a concentration of 107-100 copies/μL was used as the template.The sensitivity was 1.50×101 copies/μ,,which was 100 times higher than that of PCR.A total of 64 clinical samples with suspected RA were subjected to testing using PCR,RPA and LAMP-LFD,with a 100％compliance rate for all three detection tests.The results show that the established RPA-LFD method has the characteristics of strong specificity,high sensitivity,fast speed and visualization,and can be applied to the field detection of Pm.

A Salmonella bacteriophage,PJN025,was isolated from wastewater and characterized for its biological properties,including whole-genome sequencing and assessment of therapeutic poten-tial in animal infection models.Transmission electron microscopy classified it within the Caudovi-ricetes family.PJN025 selectively lysed S.typhimurium and S.enteritidis with an incubation period of approximately 10 min,a burst time of 80 min,and an average burst size of approximately 132 PFU/cell,demonstrating effective bactericidal activity.The phage showed robust stability at temperatures ranging from 30 to 70 ℃ and pH levels from 3 to 12.Whole-genome sequencing re-vealed a complete genome length of 46 478 bp with a G+C content of 45.9％,consisting of 82 open reading frames and one tRNA.No known virulence or resistance genes were found.In Galleria mellonella infection model,a survival rate of 70％was achieved with a preventative dose of 1 × 108 PFU/mL PJN025,compared to a 5％survival rate in the positive control group after 48 h of bacterial challenge.In SPF mice infected with S.typhimurium via intraperitoneal injection,all mices in the positive control group died within five days.However,in the co-infection group treated with 1×108 PFU/mL PJN025,a promising survival rate of 60％was observed.This study showed that the bacteriophage PJN025 had strong specificity,high lytic efficiency,good acid and alkali tol-erance,strong heat resistance,and good safety and prevention effects,providing materials and ex-perimental basis for the development of subsequent phage products.