To investigate the recent prevalence and molecular epidemiological characteristics of por-cine diarrhea viruses in Sichuan Province,this study used fluorescence quantitative PCR to detect porcine diarrhea samples from multiple regions in Sichuan Province from 2021 to 2023.RT-PCR was used to identify the genotypes of PEDV,PoRVA,PDCoV,and PTV,and their genetic variabil-ity,evolutionary characteristics,and recombination events were analyzed.The results showed that PEDV,PoRVA,PDCoV,and PTV were still prevalent in Sichuan region,with overall positive rates of 14.2％(40/281),13.2％(37/281),15.6％(44/281),and 12.5％(35/281),respectively.PEDV mixed infection with other pathogens was the most common.This study obtained a total of six strains of G2b PEDV,three strains of G3 PDCoV,three strains of G9P[13]PoRVA,one strain of G3P[13]PoRVA,three strains of Type 5 PTV,and one strain of Type 9 PTV.Compared to the seven vaccine strains including CV777,DR13,KPEDV-9,Chinju99,KNU-0801,AJ1102,and LW/L,the 6 PEDV strains showed multiple amino acid mutation sites in the COE region and S1D epitope region.Among them,the strains PSCLZ01 and PSCMY04 formed a separate branch in the phylogenetic tree.The three PDCoV strains have a closer genetic evolution distance to the previ-ously prevalent strains in Sichuan,but they also have 6-48 amino acid mutations compared to them.The four PoRVA strains have 104-108 amino acid variations in the VP4 gene compared to the early vaccine strain LLR,and they have 25 common amino acid variations in the VP7 gene.From the phylogenetic tree,the VP7 gene of RSCMY01/G3P[13]belongs to the same branch as the Heilongjiang strain LNCY,but its VP4 gene clusters with the Sichuan strain SCYA-C7,indica-ting that this PoRVA strain may have undergone genetic reassortment during inter-provincial transmission between different genotypes.It is worth noting that in the detected samples of PTV-5 and PTV-9,other diarrheal viruses tested negative,indicating that these two genotypes of PTV may be important pathogens causing porcine diarrhea.Additionally,the S gene of PEDV PSCLZ01 strain and PDCoV PCSCMY02 strain have undergone recombination events,and their parental strains come from different regions,both domestic and international.These findings reveal the main types of porcine diarrheal viruses,as well as their genetic diversity and variations in Sichuan Province in recent years.This study enriches the molecular epidemiological data of porcine diarrhe-al pathogens in the region and provides an important theoretical basis for the prevention,control,and purification of porcine diarrhea in the local area.

In order to meet the market demand for the fast and accurate genetic detection of African swine fever virus(ASFV),a new method for EIS-qPCR detection was established with a rapid,high sensitivity,and pollution prevention.Primers and probes for a duplex qPCR were designed based on the conserved region of ASFV virus p72 gene and the endogenous internal standard(EIS)cytb gene sequence in pigs.An anti-contamination system was established with uracil DNA N-gly-cosylase enzyme in the reaction system.The results showed that the method can finish the rapid qPCR detection of ASFV within 30 min with a minimal detection limit of 4.12 copies/μL.Moreo-ver,the method only detected the ASFV p72 gene,and no amplifications of classical swine fever vi-rus(CSFV),pseudorabies virus(PRV),porcine parvo virus(PPV),porcine reproductive and re-spiratory syndrome virus(PRRSV)and porcine circovirus type 2(PCV2)were observed.Repeti-tive results showed a coefficient of variation below 2％.With strong anti-pollution capacity,the method can effectively eliminate false-positive amplification caused by low-dose aerosol pollution.Detection results of 146 clinical samples showed a 100％consistence with the results of the com-mercial ASFV detection kit.Compared with similar technologies,the EIS-qPCR established in this study was faster,sensitive,and suitable for the rapid diagnosis of ASFV infection in the early stage,which provided the tool for the monitoring and precise prevention and control of African swine fever.

In order to investigate the changes in lipid metabolism of the host after infection with porcine epidemic diarrhea virus(PEDV),blood,intestinal and cellular samples were collected from PEDV-infected piglets and Vero cells,and the levels of triglyceride(TG)and total cholesterol(TC)were detected by blood biochemical analyses,flow cytometry,and immunofluorescence,and changes in the gene levels of the enzymes related to lipid metabolism of the hosts were detected by qPCR.The results showed that PEDV infection significantly elevated host total lipid levels and sig-nificantly promoted the expression of enzymes related to fatty acid and cholesterol metabolism in the intestine and Vero cells of piglets.In conclusion,PEDV infection leads to an increase in host to-tal lipid levels,remodeling of lipid metabolism in piglets intestine and Vero cells,and lipid metabo-lism gene changes.The results of this study show that lipid metabolism-related genes can be used as a key target to influence PEDV replication,which will provide a new theoretical basis for the subsequent prevention,control and treatment of PEDV infection.

The aim of this study is to investigate the immune effect of H9 subtype avian influenza virus(AIV)NP protein on mice and lay the foundation for the development of avian influenza vi-rus(AIV)vaccine.The H9N2 virus NP gene amplification product was cloned into the pET-32a expression vector,and the protein expression was verified by SDS-PAGE and Western blot,and the immune effect was evaluated by measuring the secretion of supernatant multicytokines in mouse splenocytes culture.The results showed that the total length of the coding region sequence of NP gene was 1 497 bp,NP recombinant proteins exist in both soluble and insoluble protein forms,and the specific bands were visible in Western blot.After immunizing mice,serum produces IgG-bind-ing antibodies with antibody titers of 1∶40 000.Compared with the control group,IL-2,IL-5 and IL-13 were significantly increased(P＜0.001),and the secretion of IL-6 was significantly increased compared with the control group.IL-4 and IL-12 p70 secretions were elevated compared with con-trols,but there was no significant difference.Compared with the control group,the secretions of IL-1β,IL-18,GM-CMF,TNF-α and IFN-γ were inhibited,but the difference was not significant(P＞0.05).The results showed that NP recombinant protein is a good immunogen,laying a foundation for in-depth research on influenza vaccine.

The E protein of dengue virus type Ⅱ was presented on ferritin of Helicobacter pylori to construct a novel dengue nanoparticle vaccine candidate,and the immunological indexes of the vac-cine were evaluated,aiming to provide new ideas for the development of dengue vaccine.The re-combinant plasmid of E-Ferritin was optimized and synthesized,and then transfected into HEK-293F cells.The recombinant protein was expressed,identified,purified and analyzed.Mice were im-munized with E-Ferritin nanoparticle vaccine by intramuscular injection on the hind limbs on the day 0,14 and 28.ELISA,neutralization test,flow cytometry and lymphocyte proliferation test were used to detect the levels of specific antibodies,neutralizing antibodies,CD3+,CD4+and CD8+T lymphocytes in spleen cells and the proliferation of spleen lymphocytes after specific stimulation.The target protein with a size of about 69 kDa was expressed in the cells with a single band.The purified protein concentration was 0.407 g/L,and the purity was 82.32％.The results from transmission electron microscopy showed that E-Ferritin protein could be recombined into a particle structure with a particle size of about 50 nm.The results of mouse immune experiments showed that E-Ferritin protein had good immunogenicity.The average specific antibody titer of E-ferritin protein in serum was 1∶92 160 after immunization 42 d.The main subclass of antibody was IgGl.The results of flow cytometry showed that E-Ferritin as an immunogen could induce higher levels of CD4+and CD8+T lymphocyte immune response.In lymphocyte proliferation test,the level of specific stimulation in the vaccine group was significantly higher than that in the non-specific stimulation group.In conclusion,the dengue virus envelope protein ferritin nanoparticle vaccine constructed in this study has good immunogenicity,which can provide reference for the de-velopment of new dengue vaccine candidates.

In order to achieve the purpose of rapid detection of duck astrovirus type 1(DAstV-1),specific primers were designed based on the conservative region of ORF1a which belonged to DAstV-1(WF1202 strain).A real-time fluorescent quantitative PCR(qPCR)detective method for DAstV-1 was established.Clinical samples were detected by the qPCR method and the positive samples were used for virus isolation and identification.Results showed that the detection limit of the established method was 4.64×103 copies/μL,which was 10 times higher than the normal RT-PCR method.In addition,no cross-reactions were found with other common infectious disease pathogens in poultry,indicating that the qPCR method had good specificity.What's more,the coef-ficient of variations(Cv)in intra-and inter-assays were 0.85％-2.85％and 0.21％-2.94％,re-spectively,both less than 3％,indicating that the qPCR method had a good repeatability.Using this method,35 tissue samples from different duck farms in 10 provinces from 2020 to 2022 were detected for DAstV-1.Results showed that the positive rate was 25.71％(9/35),and the coinci-dence rate was 94.29％when compared with the normal RT-PCR method.A positive sample ran-domly taken for the virus isolation through duck embryo passage,and the allantoic fluid was col-lected and then was verified by the qPCR method and inoculated with 1-day-old healthy ducklings for the animal regression experiment.The infected ducklings suffered from transient disease but did not die.The liver tissues were all positive with DAstV-1 when detected by qPCR.Meanwhile,autopsy showed that there were slight changes in the livers,and the histopathological observation showed that the liver cells were steatosis.These findings indicated that the isolated DAstV-1 strain had weak pathogenicity and might be a low virulent strain.To sum up,the qPCR detection method of DAstV-1 was successfully established in this work,and could provide technical support for clini-cal diagnosis,isolation and identification,and molecular epidemiology monitoring of DAstV-1.

The codon sequence of the S1 protein of the SARS-CoV-2 Beta variant was optimized ac-cording to the preference of CHO cells and cloned into pSN expression vector to construct the re-combinant plasmid pSN-Beta-sl.Recombinant protein was expressed in CHO cells,identified using SDS-PAGE and Western blot,and purified through affinity chromatography.BALB/c mice were immunized with purified recombinant protein Beta-S1 combined with aluminum hydroxide adju-vant.Specific IgG antibody and its subtypes in serum and the cross-neutralization antibody activity against SARS-CoV-2 variants were evaluated.The results showed that the recombinant plasmid pSN-Beta-S1 was successfully constructed,and the recombinant protein Beta-S1 was produced u-sing the CHO cell expression system.The purified recombinant protein had a single band of about 120 kDa with the purity exceeding 85％and can bind to RBD pAb and strep-tag mAb.The recom-binant S1 protein showed good immunogenicity in BALB/c mice.The titers of specific IgG antibodies against RBD protein and S1 protein reached 1∶66 260 and 1∶133 120 on average 21 d after the third immunization,the antibody subtypes were mainly inclined to IgG1.Serum neutrali-zing antibody titer was 1∶629 for wild type,1∶1 720 for Beta,1∶374 for Delta,1∶77 for Omi-cron BA1 and 1∶101 for Omicron BA2.In this study,S1 recombinant protein of SARS-CoV-2 Beta variant was successfully expressed in CHO cell expression system and produced good immunoge-nicity and cross-neutralizing activity in BALB/c mice.These results provide a reference for the fur-ther development of broad-spectrum SARS-CoV-2 vaccine.

Caprine enterovirus(CEV)is one of the most important infectious diarrheal diseases for goats.In order to understand the prevalence of CEV in different areas of Jiangsu province,410 goat fecal samples(212 diarrhea and 198 non-diarrhea samples)were collected from goat farms in 8 re-gions.127 CEV positive samples were detected by RT-PCR,and the positive rates varied greatly from 12.50％to 62.50％among different areas,with a total positive rate as 30.98％.Through the significance analysis of the positive rate of diarrhea and non-diarrhea samples,CEV was found to be one of the important pathogens causing diarrhea in goats.The results of homology and genetic evolution analysis for the 5'-UTR sequences showed that the EV-G5、G7、G21、G22 and G23 were epidemic types in Jiangsu province,and G21-G23 are new found CEV types.The homologies of 5'-UTR,VP1 and 2AB genes with the classical CEV strains in China were 78.6％-95.8％,56.9％-95.0％and 77.9％-98.4％,respectively.Of these sequences,the 5'-UTR and 2AB gene of HaiMen-SJH strain was significantly different from other sequences,and belonged to an independent branch in the genetic evolution trees.According to the results of epidemiological survey,the infection of CEV was widespread in most areas of Jiangsu province,and the epidemic types and situation varied in different areas.This study will enrich the epidemiological data of CEV in China,and provide the-oretical basis for the targeted prevention and control of new enterovirus infections in sheep.

In order to study the biological characteristics and whole-genome sequence of Streptococ-cus equi,a sheep-derived Streptococcus equi preserved in our laboratory was subjected to recovery,biochemical experiments,drug susceptibility tests and animal experiments,and followed by whole genome sequencing and annotation of the gene functions of the genome by using the biogenetic da-tabase.The biochemical identification results showed that this strain could ferment sugars,but the results of nitrate,catalase,V-P test,and M-R test were negative;the drug susceptibility test results showed that this strain was highly sensitive to most antibiotics and was resistant to kanaphylaxis.It was resistant to amikacin and amikacin;animal experiments showed that the lethality rate of this strain to mice was 100％,and the median lethal dose of this strain was measured to be 4.86X 106 CFU/kg.According to the pathological section results of mice,it showed that the lungs,liver,kidneys,and spleen all had varying degrees of lesions.The whole genome sequencing results showed that the total genome length of this strain is 2 272 497 bp,the G+C content was 41.1％,and it was predicted to contain 2 124 CDS regions.The RNA prediction results showed that the number of rRNA and tRNA was 15,and the number of tRNA was 57.There were four prophages and gene islands,and there were 362 pathogenicity-related genes in the VFDB database without CRISPR sequences.This study analyzed the complete genome of Streptococcus equi derived from sheep,and also provided a theoretical basis for the treatment,prevention and control of the disease.

Trueperella pyogenes(TP),an important livestock and poultry pathogen,can cause vari-ous diseases such as suppurative pneumonia,arthritis,and mastitis in animals.The newly brought calves of one cattle farm occurred respiratory diseases and accompanied death in Yunyang,Chongqing,based on post-mortem examination,suppuration nodules were found in the lungs,and microscopic observation of tissue smears with staining showed that a lot of short rod shape bacteri-a were in tissue.The bacteria were isolated and purified from the clinic lung tissue and analyzed by 16S rRNA sequence,the result showed the infectious bacteria was Rueperella pyogenes,and it was nominated as TpCQ-yy1.TpCQ-yy1 cultured on rabbit blood agar plates could form double-zone hemolysis,and can utilize glucose and lysine.Interestingly,the drug-resistance characteristics of TpCQ-yy1 partially changed along with the variation of the culture medium.Pathogenicity analysis showed that TpCQ-yy1 could make suppurative lesions in the lungs of mice infected via the thorac-ic and intraperitioneal route,and later led mice to death,while the subcutaneous and intramuscular routes of infection had only suppurative foci at the site of injection and were dose-dependent and non-lethal.The genome size of TpCQ-yy1 is 2.335 Mb,which encoding 2 107 proteins,and the phy-logenetic analysis showed TpCQ-yy1 is close to Trueperella pyogenes TP1 strain but away from other strains.TpCQ-yy1 infection could promote the secretion of inflammatory factors of macro-phage.TpCQ-yy1 inactivated bacterial vaccine and recombinant hemolysin(rPLO)subunit vaccine could induce high levels of antibodies production in mice immunized via subcutaneous and muscle route,but only provided 33.3％-66.7％protection to the immunized mice against TpCQ-yyl infec-tion via intraperitioneal route.This research provides a fundamental basis for the understanding of the biological characteristics,pathogenicity,and prevention and control of Trueperella pyogenes.