Objectives: Research on the immunocastration vaccine is of great significance for animal management. In this study, the gonadotropin-releasing hormone (GnRH) ferritin nanoparticle vaccine was constructed using Spy Catcher-Spy Tag (SC-ST) as a delivery system; Methods: The Spy Catcher was constructed to fuse with the expression vector pET-30a-SF of ferritin nanoparticles. Two polypeptides, STG1: Spy Tag-GnRH I-PADRE and STG2: Spy Tag-GnRH I-GnRH II, coupled to SF in vitro to form two nanoparticles, were designed and synthesized to detect castration effects in mice. We mixed them with the adjuvant MONTANIDE ISA 206 VG to explore the adjuvant’s effect on immunogenicity; Results: All immunized groups produced anti-GnRH specific antibodies after the second immunization, which was significantly higher in the immunized group and the combined adjuvant group than in the control group, and the immune response could still be detected at the 12th week. The concentrations of testosterone, follicle-stimulating hormone, and luteinizing hormone in serum were significantly decreased. The number of sperm in the epididymis of mice in each immune group was significantly reduced, and the rate of sperm deformity was high; Conclusions: The two ferritin-based GnRH nanoparticles developed in this study can significantly cause testicular atrophy, decreased gonadal hormone concentration, decreased sperm count, and increased deformity rate in male mice. These findings provide experimental evidence supporting their potential application in animal immunocastration.

This study aimed to design and evaluate the immunogenicity of a dual-valent virus-like particles (VLP) vaccine that can simultaneously target Canine distemper virus (CDV) and Ca nine parvovirus virus (CPV).By bioinformatic analysis, conserved antigen epitopes of the three major functional proteins of CDV were screened and inserted into CPV-VP2 proteins by two different methods to construct recombinant expression plasmids CDPV1 versus CDPV2.Thr ee-dimensional structure, hydrophobicity and stability predictions of the two recombinant proteins showed that their hydrophobicity were 0.233 and 0.251, and their structural stability scores were 0.77 and 0.78, respectively.Recombinant plasmids were co-transformed with molecular chaperone pTf16 to be expressed in E. coli BL21(DE3), respectively, and the optimal expression conditions were determined after optimization: 0.25 mmol/L IPTG, 2 g/L L-arabinose in duction, and culture at 25°C for 16 h.Purified recombinant proteins can self-assemble in vitro to form VLPs about 23.5 nm in diameter with a hemagglutination titer of 1:2 ⁹ .The mouse immune test showed that the hemagglutination inhibition titer peaked on the 7th day after the third immunization, and the neutralizing Antibody level could reach up to 1:2 ⁸ .The CPV VLP s constructed in this institute carrying CDV antigen epitopes were able to successfully assemble in vitro and were well immunogenic, providing experimental basis for the development of a canine polyvalent vaccine.