Résumé
AIM: DNA vaccines expressing protective domain of surface protective antigen A（spaA）of Erysipelothrix rhusiopathiae have been relatively ineffective at generating high-titer, long-lasting, neutralizing antibodies in murine models. METHODS: This paper report using a DNA vaccine expressing a fusion of the spaA protein and various elements, such as a secretion leader sequence from the highly expressed human gene encoding α1-antitrypsin (AAT), a highly soluble and stably folded domain from the rat cartilage oligomerization matrix protein (COMP), and three copies of the complement component, C3d3, to enhance the titers of neutralizing spaＡ-specific antibody. RESULTS: Analysis of titers of the antibody raised in vaccinated mice at different time points indicated that immunizations with the DNA expressing pcDNA3-AAT-COMP-spaAN-3C3d((pcD-ACSC)) had higher titers than pcDNA3-spaA_N(pcD-S) at weeks 4. Furthermore, the immune protective efficacy of the spaA-chimeras was demonstrated by lethal challenge with a virulent homologous strain 1249 against immunized mice. CONCLUSION: These results suggest that using a plasmid vector containing a strong heterologous signal sequence that mediate efficient antigen secretion in vivo and a fused piece of sequence improving antigens solubility, as well as C3d3, genetic adjuvant, could enhance the antibody responses level. This approach might be an efficient way to improve the antibody level of spaA_N DNA vaccination.
Résumé
Mammalian zona pellucida 3(ZP3) plays an important role in the induction of capacitating sperm acrosome reaction. In this study, we obtained the soluble mZP3 fusion protein and identified its immunoreactivity. mZP3 cDNA was cloned into plasmid pMAL-p2x, and the recombinant plasmid was transformed into Escherichia coli BL21. To get the soluble mZP3 fusion protein, we tried to optimize the expression conditions, including additives, IPTG concentrations, temperatures and induction duration. Then, Western blotting and ELISA were used to identify the immunoreactivity of the purified protein. Based on the optimization experiments, we concluded that the best soluble expression conditions for the mZP3 fusion protein involved incubation to an A600 of 0.6, addition of glucose to a final concentration of 0.02 mol/L, addition of IPTG to a final concentration of 0.6 mmol/L and then further incubation for 4 h at 25 degrees C. Western blotting and ELISA showed that the mZP3 fusion protein retained immunoreactivity. The fusion protein can be used as solubility antigens for developing the immunocontraception vaccines of mZP3 and detecting the immune effects of the vaccine.