RESUMO
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.