Objective:To further study on the biological characteristics of vaccinia virus VG9 strain obtained by passaging from vaccinia virus Tiantan strain(VTT).Methods:The freeze-dried vaccinia virus VG9 strain was reconstituted and inoculated into Vero cells for recovery and sequential passaging. The strain was identified by indirect immunofluorescence and PCR amplification. The whole genome of VG9 was sequenced using next-generation sequencing technology. The sequencing results were compared with the reference sequence of VTT and the genome sequences of other 33 orthopoxviral strains, and a phylogenetic tree was drawn. A purified clone of VG9, namely VG9-V3-3, was obtained by terminal dilution method. Preliminary studies were conducted to characterize the biological properties of this clone, such as virus titer and intradermal virulence in rabbit.Results:VG9 could specifically bind to the rabbit antibody of VTT by indirect immunofluorescence identification, and the PCR amplification results proved that this strain contained the characteristic TK gene fragment of vaccinia virus. Whole-genome sequencing showed that the genome length of VG9 was 183 596 bp, including 165 150 bp in coding region. The sequencing results were compared with the NCBI core nucleotide database, and showed that the sequences of VG9 and multiple existing Tiantan isolates were highly homologous (consistency>99.5%). Sequence comparison revealed a total of 749 nucleotide site differences between the gene sequences of VG9 and TP5 isolate of VTT. The viral titer of the VG9-V3-3 isolate was 6.3 lg (PFU/ml), and the rabbit intradermal virulence assay showed that its virulence was significantly weakened compared with that of VTT.Conclusions:The biological characteristics of vaccinia virus VG9 strain are preliminarily studied and a purified clone strain named VG9-V3-3 is obtained. The viral titer of the isolate is basically stable, and the virulence is significantly weakened compared with that of VTT. In-depth study on the immunogenicity of VG9-V3-3 will be carried out in the future to explore its feasibility as a vaccine production strain.

Objective:To further study on the biological characteristics of vaccinia virus VG9 strain obtained by passaging from vaccinia virus Tiantan strain(VTT).Methods:The freeze-dried vaccinia virus VG9 strain was reconstituted and inoculated into Vero cells for recovery and sequential passaging. The strain was identified by indirect immunofluorescence and PCR amplification. The whole genome of VG9 was sequenced using next-generation sequencing technology. The sequencing results were compared with the reference sequence of VTT and the genome sequences of other 33 orthopoxviral strains, and a phylogenetic tree was drawn. A purified clone of VG9, namely VG9-V3-3, was obtained by terminal dilution method. Preliminary studies were conducted to characterize the biological properties of this clone, such as virus titer and intradermal virulence in rabbit.Results:VG9 could specifically bind to the rabbit antibody of VTT by indirect immunofluorescence identification, and the PCR amplification results proved that this strain contained the characteristic TK gene fragment of vaccinia virus. Whole-genome sequencing showed that the genome length of VG9 was 183 596 bp, including 165 150 bp in coding region. The sequencing results were compared with the NCBI core nucleotide database, and showed that the sequences of VG9 and multiple existing Tiantan isolates were highly homologous (consistency>99.5%). Sequence comparison revealed a total of 749 nucleotide site differences between the gene sequences of VG9 and TP5 isolate of VTT. The viral titer of the VG9-V3-3 isolate was 6.3 lg (PFU/ml), and the rabbit intradermal virulence assay showed that its virulence was significantly weakened compared with that of VTT.Conclusions:The biological characteristics of vaccinia virus VG9 strain are preliminarily studied and a purified clone strain named VG9-V3-3 is obtained. The viral titer of the isolate is basically stable, and the virulence is significantly weakened compared with that of VTT. In-depth study on the immunogenicity of VG9-V3-3 will be carried out in the future to explore its feasibility as a vaccine production strain.

Objective To express and purify the glycoprotein extracellular domain (Ex-GP) of Rabies virus strain CTN in soluble form with high efficiency.Methods A recombinant expression plasmid containing the gene encoding the Ex-GP was constructed.Various expression conditions were screened to obtain an optimum prokaryotic expression system for Ex-GP in soluble form.The expressed target protein was purified using affinity chromatography and gel filtration chromatography.Results The target protein Ex-GP with high antigenicity was efficiently expressed in soluble form by using the recombinant PBCX expression system and effectively purified by using affinity and gel filtration chromatography.Conclusion The soluble form of Ex-GP is successfully expressed and purified in a simple and convenient way.This study paves the way for further researches on the biological functions of rabies virus glycoprotein,the pathogenic mechanism of rabies and the development of diagnostic reagent and vaccines for rabies virus.

Objective To prepare a neutralizing monoclonal antibody against rabies virus. Meth-ods BALB/c mice were immunized with the inactivated rabies virus CTN strains on day 0, 7, 14 and 28. Spleen cell samples were collected and then fused with SP2/0 cells to prepare the hybridoma cell line. Posi-tive hybridoma cells that were screened out with RFFIT technique were injected into BALB/c mice intraper-itoneally. Ascites samples were collected from the mice to separate neutralizing monoclonal antibodies. Affin-ity chromatography was used for the purification of neutralizing monoclonal antibodies. Subtype identification and sequencing analysis were performed for further identification. A colloidal gold strip based method for rap-id detection of rabies vaccine was established with the prepared monoclonal antibodies. Results The hybri-doma cell line, CTN-McAb1, was prepared successfully with stable secretion of neutralizing monoclonal anti-bodies against rabies virus. The purity of those antibodies was more than 95% after purification and the sub-type of them was IgG1. The colloidal gold strip for raid detection of rabies vaccine was successful prepared. Conclusion The neutralizing monoclonal antibody against rabies virus was successfully prepared and could be used for preliminary application. This study will be of great significance for the quality control of rabies vaccine.

Objective To construct the eukaryotic expression plasmid of the rabies virus glycoprotein gene DNA,and detect the immunogenicity.Methods Using RT-PCR amplified the glycoprotein gene of rabies virus CTN strain,sequenced and cloned into pcDNA5.0 (+) vector to construct the recombinant plasmid pcDNA5.0-G plasmid.Detect glycoprotein transient expression with transfecting the plasmid into 293T cells.Intramuscular immunization of BALB/c mice by the recombinant plasmid on day 0 and 7,then challenge by rabies virus CVS strain observed the mice survived.Results The results of the transient expression of glycoprotein abundantly expressed.The survival ratio of mice with CVS challenge after routine intramuscular injection of pcDNA5.0-G plasmid is 73.3％,and 6.7％ for the control group.Conclusion Rabies virus glycoprotein eukaryotic expression plasmid pcDNA5.0-G was successfully constructed,and has been good immunogenicity.It's to be the foundation for candidate DNA vaccine research and development.

Objective To explore the application of atomic force microscopy( AFM ) on the research of morphology of the rabies viruses. Methods To prepare the rabies virus CTN-1v strains by ultracentrifugation, and observe it with transmission electron microscopy (TEM) which negatively stained by phosphotungstic acid. Then study the morphology of rabies virus with AFM based on the result of TEM. AFM image applies the tapping mode to rabies virus without any further treatment in air at room temperature. Results The TEM image is two-dimensional image which can be seen the classical bullet-shaped structure,and the spike structure can also be seen. The AFM image showed the rabies virus morphology with three-dimensional image which can shows the characteristics of the virus surface and edge. The rabies virus particle was successfully observed by TEM or AFM methods. Conclusion It's the first time to get the three-dimensional morphological structure of rabies virus by atomic force microscopy, compared with transmission electron microscopy, AFM is a new research tool for viral morphology study with the advantages of simple sample preparing and intuitionistic and visible interface for researchers.