This study aims to establish an indirect ELISA method for detecting RVFV antibodies u-sing recombinant proteins of Rift Valley fever virus(RVFV)Gn protein Ⅱ-Ⅲ structural domains as the encapsulated antigen which was expressed by the Escherichia coli(E.coli)expression sys-tem.The gene sequences encoding the Ⅱ and Ⅲ subdomains of RVFV Gn protein were inserted in-to pET-30a(+)to construct the recombinant plasmid pET-RVFV Gn-D Ⅱ-Ⅲ.After transforma-tion of the recombinant plasmid into DE3(BL21)competent cells,the recombinant Gn-D Ⅱ-Ⅲ protein was induced with IPTG and purified using affinity chromatography.An indirect ELISA method for the detection of RVFV antibodies was developed using purified recombinant protein as coating antigen and SPA-HRP as the enzyme-labelled secondary antibody.Western blot analysis confirmed that the RVFV Gn-D Ⅱ-Ⅲ protein was successfully expressed.The optimal expression conditions for RVFV Gn-D Ⅱ-Ⅲ protein were induced with 0.8 mmol/L IPTG at 37 ℃ for 5 h.The Gn-D Ⅱ-Ⅲ protein was purified using affinity chromatography with a purity of 91.9％,and the purified protein was used as the encapsulated antigen to develop an ELISA assay for RVFV anti-bodies.The specificity evaluation showed that the method specifically detected RVFV-positive sera and did not cross-react with sera positive for West Nile virus(WNV),Ebola virus(EBOV),Mar-burg virus(MARV)and tick-borne encephalitis virus(TBEV).When the RVFV Gn-D Ⅲ-Ⅲ posi-tive serum was diluted to 6 400 times,the test result still showed positive results,demonstrating the method had good sensitivity.The repeatability evaluation results indicated that the variation co-efficients for both intra-and inter-batch responses was less than 10％,indicating that the method had good repeatability.In conclusion,the RVFV Gn-D Ⅱ-Ⅲ protein was successfully expressed u-sing the E.coli expression system.The purified recombinant Gn-D Ⅱ-Ⅲ protein was used as the encapsulated antigen to develop an indirect ELISA assay for RVFV antibodies,which provides a preliminary basis for the diagnosis of RVF and the research and development of RVF vaccines.

To establish an indirect enzyme linked immunosorbent assay(ELISA)method for the detection of Zaire Ebola virus(ZEBOV)specific antibodies,the full-length of ZEBOV GP1 gene was amplified by PCR and cloned into pET-30a(+)vector to generate the pET-30a(+)-GP1 plasmid.After expressed in the E.coli expression system,the purified GP1 protein was used as coating antigen to establish the indirect ELISA method for detection of ZEBOV antibody.The con-ditions including concentration of coating antigen and serum dilution were determined by chess-board titration.Specificity,sensitivity,and reproducibility of the established ELISA detection meth-od were evaluated.GP1 protein was successfully prepared by prokaryotic expression,and was used as the coatingantigen for indirect ELISA.By optimizing the reaction conditions,the optimal concen-tration of the coating antigen was determined to be 0.5 g/L;the optimal dilution of serum was cal-culated to be 1∶3 200;the optimal dilution of enzyme-labeled secondary antibody was measured to be 1∶20 000.The established method exhibited excellent specificity,sensitivity,and reproducibili-ty.In the present study,the GP1 protein was successfully expressed in the E.coli expression sys-tem and the high purity GP1 protein was used as the coating protein to establish an indirect ELISA assay for ZEBOV antibody.This method is highly specific,sensitive,and reproducible,which provides technical support for the fur-ther study of the biological function of GP1 and the detection of ZEBOV antibody in serum.

To comprehend the genetic evolutionary characteristics and biological properties of the H4N1 subtype avian influenza virus(AIV)in China,this study conducted whole genome sequen-cing,genetic evolutionary analysis,and pathogenicity test in BALB/c mice of a duck-derived H4N1 subtype AIV strain(DK/GX/E1424/20)isolated from the live poultry market in the southern re-gion in 2020.The results indicated that the cleavage site motif of the HA protein was PEKASR/GLF,which conformed to the characteristics of low pathogenic AIV.All the eight gene fragments were situated in the Eurasian lineage,and the homology of AIV-related genes of the H1N1,H3N8,H4N6,H6N1,and H10N8 subtypes isolated from wild waterfowl was the highest,representing a recombinant virus strain.Without prior adaptation,it replicated effectively in the lungs and turbi-nates of mice,with viral titers of 3.00 and 2.08 log10EID50/mL respectively,and induced weight loss in infected mice.This study suggested that this virus had significant genetic diversity and low pathogenicity in mice,posing a potential risk for mammalian infection.

Feline herpesvirus type Ⅰ(FHV-1)was used as the vector.The gI and gE genes of FHV-1 were replaced with the feline calicivirus(FCV)VP1 gene and the red fluorescent protein(mCherry)gene by CRISPR/Cas9 systems and homologous recombination technology,and the re-combinant virus strain FHV △gI&gE/VP1-mCherry+was successfully rescued.The recombinant virus strain was purified by plaque assay.The biological characteristics and genetic stability of the recombinant virus were analyzed by indirect immunofluorescence assay,plaque morphological anal-ysis,and PCR.The results of the indirect immunofluorescence identification showed that the re-combinant virus FHV △gI&gE/VP1-mCherry+could express the VP1 protein in F81 cells,and the growth characteristics of the recombinant virus were not significantly different from those of the parent virus FHV-1.The plaque morphology and staining results indicated that the area of the plaque formed by the recombinant virus was smaller than that of the parent virus,suggesting that the spread ability of the recombinant virus between cells was reduced after the deletion of the gI and gE genes.The result of PCR showed that the VP1 gene could still be detected after 15 succes-sive passages of the recombinant virus,indicating that the recombinant virus had good genetic stability.In this study,the recombinant virus strain expressing the FCV VP1 protein was successfully prepared,which will lay a foundation for the development of engineered FCV and FHV-1 vaccine.

Moloney leukemia virus 10(MOV10)gene knockout(MKO)mouse neuro 2a(N2a)cell lines was constructed by CRISPR/Cas9(clustered regularly interspaced short palindromic repeat/CRISPR-associated protein 9)gene editing technology.First,a recombinant plasmid pMD18T-U6-sgRNA expressing MOV10 gene-specific guide RNA(sgRNA)was constructed,and then pMD18T-U6-sgRNA and pMJ920-Cas9-eGFP were co-transfected into N2a.The results showed that the MKO N2a cell line had normal cell activity and cell proliferation ability.The infection test of the MKO N2a cell line was carried out using the rabies virus(RABV)and vesicular stomatitis virus(VSV)of the Rhabdoviridae family.The results showed that the replication level of the Rhabdoviridae virus in the MKO N2a cell line was significantly enhanced.The results showed that a MKO N2a cell line was successfully constructed in this study,which provided a preliminary basis for the exploration of the biological function and antiviral mechanism of MOV10 and the develop-ment of a recombinant viral vector vaccine with RABV/VSV as the vector.

This study aims to establish an indirect ELISA method for detecting RVFV antibodies u-sing recombinant proteins of Rift Valley fever virus(RVFV)Gn protein Ⅱ-Ⅲ structural domains as the encapsulated antigen which was expressed by the Escherichia coli(E.coli)expression sys-tem.The gene sequences encoding the Ⅱ and Ⅲ subdomains of RVFV Gn protein were inserted in-to pET-30a(+)to construct the recombinant plasmid pET-RVFV Gn-D Ⅱ-Ⅲ.After transforma-tion of the recombinant plasmid into DE3(BL21)competent cells,the recombinant Gn-D Ⅱ-Ⅲ protein was induced with IPTG and purified using affinity chromatography.An indirect ELISA method for the detection of RVFV antibodies was developed using purified recombinant protein as coating antigen and SPA-HRP as the enzyme-labelled secondary antibody.Western blot analysis confirmed that the RVFV Gn-D Ⅱ-Ⅲ protein was successfully expressed.The optimal expression conditions for RVFV Gn-D Ⅱ-Ⅲ protein were induced with 0.8 mmol/L IPTG at 37 ℃ for 5 h.The Gn-D Ⅱ-Ⅲ protein was purified using affinity chromatography with a purity of 91.9％,and the purified protein was used as the encapsulated antigen to develop an ELISA assay for RVFV anti-bodies.The specificity evaluation showed that the method specifically detected RVFV-positive sera and did not cross-react with sera positive for West Nile virus(WNV),Ebola virus(EBOV),Mar-burg virus(MARV)and tick-borne encephalitis virus(TBEV).When the RVFV Gn-D Ⅲ-Ⅲ posi-tive serum was diluted to 6 400 times,the test result still showed positive results,demonstrating the method had good sensitivity.The repeatability evaluation results indicated that the variation co-efficients for both intra-and inter-batch responses was less than 10％,indicating that the method had good repeatability.In conclusion,the RVFV Gn-D Ⅱ-Ⅲ protein was successfully expressed u-sing the E.coli expression system.The purified recombinant Gn-D Ⅱ-Ⅲ protein was used as the encapsulated antigen to develop an indirect ELISA assay for RVFV antibodies,which provides a preliminary basis for the diagnosis of RVF and the research and development of RVF vaccines.

To establish an indirect enzyme linked immunosorbent assay(ELISA)method for the detection of Zaire Ebola virus(ZEBOV)specific antibodies,the full-length of ZEBOV GP1 gene was amplified by PCR and cloned into pET-30a(+)vector to generate the pET-30a(+)-GP1 plasmid.After expressed in the E.coli expression system,the purified GP1 protein was used as coating antigen to establish the indirect ELISA method for detection of ZEBOV antibody.The con-ditions including concentration of coating antigen and serum dilution were determined by chess-board titration.Specificity,sensitivity,and reproducibility of the established ELISA detection meth-od were evaluated.GP1 protein was successfully prepared by prokaryotic expression,and was used as the coatingantigen for indirect ELISA.By optimizing the reaction conditions,the optimal concen-tration of the coating antigen was determined to be 0.5 g/L;the optimal dilution of serum was cal-culated to be 1∶3 200;the optimal dilution of enzyme-labeled secondary antibody was measured to be 1∶20 000.The established method exhibited excellent specificity,sensitivity,and reproducibili-ty.In the present study,the GP1 protein was successfully expressed in the E.coli expression sys-tem and the high purity GP1 protein was used as the coating protein to establish an indirect ELISA assay for ZEBOV antibody.This method is highly specific,sensitive,and reproducible,which provides technical support for the fur-ther study of the biological function of GP1 and the detection of ZEBOV antibody in serum.

Feline herpesvirus type Ⅰ(FHV-1)was used as the vector.The gI and gE genes of FHV-1 were replaced with the feline calicivirus(FCV)VP1 gene and the red fluorescent protein(mCherry)gene by CRISPR/Cas9 systems and homologous recombination technology,and the re-combinant virus strain FHV △gI&gE/VP1-mCherry+was successfully rescued.The recombinant virus strain was purified by plaque assay.The biological characteristics and genetic stability of the recombinant virus were analyzed by indirect immunofluorescence assay,plaque morphological anal-ysis,and PCR.The results of the indirect immunofluorescence identification showed that the re-combinant virus FHV △gI&gE/VP1-mCherry+could express the VP1 protein in F81 cells,and the growth characteristics of the recombinant virus were not significantly different from those of the parent virus FHV-1.The plaque morphology and staining results indicated that the area of the plaque formed by the recombinant virus was smaller than that of the parent virus,suggesting that the spread ability of the recombinant virus between cells was reduced after the deletion of the gI and gE genes.The result of PCR showed that the VP1 gene could still be detected after 15 succes-sive passages of the recombinant virus,indicating that the recombinant virus had good genetic stability.In this study,the recombinant virus strain expressing the FCV VP1 protein was successfully prepared,which will lay a foundation for the development of engineered FCV and FHV-1 vaccine.

Moloney leukemia virus 10(MOV10)gene knockout(MKO)mouse neuro 2a(N2a)cell lines was constructed by CRISPR/Cas9(clustered regularly interspaced short palindromic repeat/CRISPR-associated protein 9)gene editing technology.First,a recombinant plasmid pMD18T-U6-sgRNA expressing MOV10 gene-specific guide RNA(sgRNA)was constructed,and then pMD18T-U6-sgRNA and pMJ920-Cas9-eGFP were co-transfected into N2a.The results showed that the MKO N2a cell line had normal cell activity and cell proliferation ability.The infection test of the MKO N2a cell line was carried out using the rabies virus(RABV)and vesicular stomatitis virus(VSV)of the Rhabdoviridae family.The results showed that the replication level of the Rhabdoviridae virus in the MKO N2a cell line was significantly enhanced.The results showed that a MKO N2a cell line was successfully constructed in this study,which provided a preliminary basis for the exploration of the biological function and antiviral mechanism of MOV10 and the develop-ment of a recombinant viral vector vaccine with RABV/VSV as the vector.

To comprehend the genetic evolutionary characteristics and biological properties of the H4N1 subtype avian influenza virus(AIV)in China,this study conducted whole genome sequen-cing,genetic evolutionary analysis,and pathogenicity test in BALB/c mice of a duck-derived H4N1 subtype AIV strain(DK/GX/E1424/20)isolated from the live poultry market in the southern re-gion in 2020.The results indicated that the cleavage site motif of the HA protein was PEKASR/GLF,which conformed to the characteristics of low pathogenic AIV.All the eight gene fragments were situated in the Eurasian lineage,and the homology of AIV-related genes of the H1N1,H3N8,H4N6,H6N1,and H10N8 subtypes isolated from wild waterfowl was the highest,representing a recombinant virus strain.Without prior adaptation,it replicated effectively in the lungs and turbi-nates of mice,with viral titers of 3.00 and 2.08 log10EID50/mL respectively,and induced weight loss in infected mice.This study suggested that this virus had significant genetic diversity and low pathogenicity in mice,posing a potential risk for mammalian infection.