Gene conjugation of molecular adjuvant C3d(3) to hCG beta increased the anti-hCG beta Th2 and humoral immune response in DNA immunization

摘要

Human chorionic gonadotropin (hCG) has been used as an anti-fertility vaccine and as a target for cancer immunotherapy. We have explored the use of three copies of C3d in DNA vaccine as molecular adjuvant to improve the immunogenicity of this hormone in previous work and found that the immune response induced by pcDNA3-hCG beta-C3d(3) has been enhanced 243-fold compared with pcDNA3-hCG beta following DNA immunization in BALB/c mice. In the present study, a new functionally active DNA vaccine of hCG beta-C3d(3) chimera based on pCMV4 vector has been described. We compared the expression efficiency of pCMV4 and pcDNA3 eukaryotic vectors for hCG beta and hCG beta-C3d(3) fusion protein and the immune response of mice immunized with pcDNA3-hCG beta, pCMV4-hCG beta, pcDNA3-hCG beta-C3d(3) and pCMV4-hCG beta-C3d(3), respectively, at 25, 50 and 100 pmol dose, and further analyzed the levels of Th1 and Th2 cytokines produced by spleen lymphocytes of the immunized mice upon hCG restimulation in vitro. It was found that pCMV4 vector achieved 1.3-1.5-fold higher protein expression and raised 1.1-1.2 (primary) and 1.2-1.3 (booster) logs higher titer of anti-hCG beta IgG than pcDNA3. Mice vaccinated with 50 pmol of hCG beta-C3d(3)-DNAs elicited the highest titer of hCG beta-specific antibody among the serial doses and the immune response induced by pCMV4-hCG beta-C3d(3) were, respectively, 1.3, 1.3 and 1.2 logs higher than that of pcDNA3-hCG beta-C3d(3) and 2.2, 2.9 and 2.4 logs higher than that of pCMV4-hCG beta at week 2 following the booster immunization. Moreover, we observed that the production of IL-4 and IL-10 increased in mice vaccinated with hCG beta-C3d(3)-DNAs and the ratio of IL-4/IFN-(gamma) showed a Th2 bias of immune response in the mice immunized with hCG beta-C3d(3)-DNAs. These findings indicated that gene fusion of C3d(3) to hCG beta, as a means of harnessing the adjuvant potential of the innate immune system, may improve the antigen-specific Th2 humoral immune response of the hCG DNA vaccine and the pCMV4 vector is a more ideal eukaryotic vector for DNA vaccine than pcDNA3. Copyright (c) 2006 John Wiley & Sons, Ltd.