Codon optimization was performed for the M and HN genes of bovine parainfluenza virus type 3(BPIV3),and the recombinant shuttle plasmid Dual-M+HN was constructed.BPIV3 VLPs was prepared using the baculovirus expression system,and verified by Western blot,IFA and elec-tron microscopy.The successfully verified virus-like particle(VLPs)were mixed with MF59 adjuvant and CpG-ODN immunoenhancer to immunize mice by intramuscular-injection,and BPIV3 inactivated vaccine group and adjuvant control group were set up.The immune effect of BPIV3 VLPs was evaluated by monitoring mouse serum specific antibodies,neutralizing antibodies and hemagglutination inhibition antibodies.The results showed that the optimized codon adaptation in-dex(CAI)of the M and HN protein genes were 0.96 and 0.95,respectively,and the CG content reached 54.1％and 53.1％,respectively.The constructed recombinant plasmid was transformed in-to DHI0Bac for blue and white spot screening.The validated recombinant rod particles were trans-fected into Sf9 cells to obtain the rod-shaped virus pFastBac-M+HN.Under electron microscopy,BPIV3 VLPs with a diameter of approximately 180 nm were observed.IFA and Western blot ex-periments confirmed the successful expression and biological activity of the target protein.Through protein optimization,it was found that the protein expression was highest at an infection dose of MOI=5.After mixing 50 μg VLPs with MF59 adjuvant and CpG-ODN,mice were immunized by intramuscular injection.The results showed that the antibodies in the VLPs immunized group be-gan to rise at 2 weeks of the first immunization and reached their peak at 21 days of the second im-munization,with an average IgG antibody titer of 1∶40 228;The average titer of neutralizing anti-bodies is 1∶298;The titer of hemagglutination inhibition antibody is 1∶549,reaching the level of inactivated vaccine(P≥0.05),indicating that the VLPs prepared in this experiment can induce hu-moral immune response in the body.In summary,this study successfully prepared VLPs capable of self-assembly expression of BPIV3 HN and M proteins,and induced humoral immune response in mice,providing research basis for subsequent BPIV3 VLPs vaccine research.

Codon optimization was performed for the M and HN genes of bovine parainfluenza virus type 3(BPIV3),and the recombinant shuttle plasmid Dual-M+HN was constructed.BPIV3 VLPs was prepared using the baculovirus expression system,and verified by Western blot,IFA and elec-tron microscopy.The successfully verified virus-like particle(VLPs)were mixed with MF59 adjuvant and CpG-ODN immunoenhancer to immunize mice by intramuscular-injection,and BPIV3 inactivated vaccine group and adjuvant control group were set up.The immune effect of BPIV3 VLPs was evaluated by monitoring mouse serum specific antibodies,neutralizing antibodies and hemagglutination inhibition antibodies.The results showed that the optimized codon adaptation in-dex(CAI)of the M and HN protein genes were 0.96 and 0.95,respectively,and the CG content reached 54.1％and 53.1％,respectively.The constructed recombinant plasmid was transformed in-to DHI0Bac for blue and white spot screening.The validated recombinant rod particles were trans-fected into Sf9 cells to obtain the rod-shaped virus pFastBac-M+HN.Under electron microscopy,BPIV3 VLPs with a diameter of approximately 180 nm were observed.IFA and Western blot ex-periments confirmed the successful expression and biological activity of the target protein.Through protein optimization,it was found that the protein expression was highest at an infection dose of MOI=5.After mixing 50 μg VLPs with MF59 adjuvant and CpG-ODN,mice were immunized by intramuscular injection.The results showed that the antibodies in the VLPs immunized group be-gan to rise at 2 weeks of the first immunization and reached their peak at 21 days of the second im-munization,with an average IgG antibody titer of 1∶40 228;The average titer of neutralizing anti-bodies is 1∶298;The titer of hemagglutination inhibition antibody is 1∶549,reaching the level of inactivated vaccine(P≥0.05),indicating that the VLPs prepared in this experiment can induce hu-moral immune response in the body.In summary,this study successfully prepared VLPs capable of self-assembly expression of BPIV3 HN and M proteins,and induced humoral immune response in mice,providing research basis for subsequent BPIV3 VLPs vaccine research.