Molecular adjuvant C3d3 improved the anti-hCGbeta humoral immune response in vaginal inoculation with live recombinant Lactobacillus expressing hCGbeta-C3d3 fusion protein.

To enhance the contraceptive efficiency of human chorionic gonadotrophin (hCG)-beta contraceptive vaccine, we coupled hCG-beta gene with molecular adjuvant C3d3, and cloned into live Lactobacilli (Lb.) to express fusion protein hCGbeta-C3d3. The recombinant Lb. could survive in BALB/c murine vagina for at least 3 weeks. After inoculating BALB/c and C57BL/6 mice via vagina, we found that the antibody titer peaks induced by the Lb.hCGbeta-C3d3 inoculation were higher significantly than the Lb.hCGbeta. T and B cells in spleen and vagina were significantly increased, and anti-hCGbeta IgG and IgA antibody-secreting cells in uterus and vagina were significantly increased compared to the control in different strain mice. Our study shows that the C3d3 can display apparent adjuvant efficiency to induce more powerful humoral response to the hCGbeta antigen in vaginal mucosal immunization.