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.

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.

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.

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.