[C3d molecular adjuvant increases the immunity of human chorionic gonadotropin beta DNA contraceptive vaccination and...

To testify the effect of C3d molecular adjuvant on the immunogenicity of human chorionic gonadotropin beta (hCG beta) DNA vaccination as well as the mode of immune response.

BALB/c mice aged 6 weeks were immunized intramuscularly two times at an interval of 3 weeks with by the plasmid pcDNA3 (A1-3 groups), pcDNA3-hCG beta (B-3 groups), pcDNA3-hCG beta-C3d3 (C1-3 groups), or pCMV4-hCG beta-C3d3 (D1-3 groups), at dosage of 5 pmol, 10 pmol, and 20 pmol, respectively. Three weeks after the second vaccination the animals were killed, specimens of their peripheral blood were extracted to determine the anti-hCG beta antibody titer by indirect ELISA. Their spleen cells were harvested and stimulated in vitro by hCG antigen for 24 hours. The Th1/Th2 cytokines in the culture supernatant were determined by ELISA.

At the dosage of 20 pmol, C3d molecular adjuvant significantly enhanced the anti-hCG beta antibody titer. The utmost anti-hCG beta antibody titer of C3 group was 1:450, 9 times higher than that of B3 group, and the utmost anti-hCG beta antibody titer of D3 group was 1:12 150, 243 times higher than that of B3 group. Stimulated in vitro by 5,000 IU hCG beta antigen, the splenic cells of the C3 and D3 immunization group produced significantly lower IL-2, INF-gamma and TNF-alpha than those of the B3 immunization group (P < 0.01 or P < 0.05). The IL-4 level of the C3 group was higher than that of the B3 group while the IL-10 level of the D3 group was significantly higher than that of the B3 group (P < 0.01).

The C3d molecular adjuvant increases significantly the hCG beta immunogenicity of hCG beta DNA vaccination; meanwhile decreases the secretion of Th1 cytokines (IL-2, INF-gamma, and TNF-alpha), and increases the expression of Th2 cytokines (IL-4 and IL-10) in response to hCG antigen. So C3d changes the anti-hCG immune response from Th1 type to Th2 type.