[Gene conjugation of molecular adjuvant C3d3 to hCGbeta enhanced the anti-hCGbeta humoral immune response via upregulation of CXCR4 expression on splenic B cells in DNA vaccination].

To investigate mechanism of the anti-hCGbeta humoral immune responsive enhancement by gene conjugation of the molecular adjuvant C3d3 to hCGbeta in DNA immunization, BALB/c mice were inoculated intramuscularly with pCMV4-hCGbeta-C3d3, pCMV4-hCGbeta and pCMV4, respectively. The titers of anti-hCGbeta IgG/IgA antibody in serum were determined by indirect ELISA. The IgG/IgA ASCs levels were evaluated by ELISPOT. The expressions of chemokine receptors on B cells were analyzed by RT-PCR, and CXCR4 expression was analyzed respectively by RT-PCR and FCM. The expression of CXCL12 in spleen was investigated respectively by RT-PCR and ELISA. We found that anti-hCGbeta IgG antibody titer in serum after pCMV4-hCGbeta-C3d3 immunization was significantly higher than that of pCMV4-hCGbeta immunization. But the anti-hCGbeta IgA antibody titers appeared no difference between the two immunized groups. The level of IgG ASCs in spleen of pCMV4-hCGbeta-C3d3 immunization was significantly higher than that of pCMV4-hCGbeta immunization,but the levels of IgA ASCs appeared no difference between the two groups. The expression of CXCR4 on B cell increased after pCMV4-hCGbeta-C3d3 immunization, and significantly higher than that of pCMV4-hCGbeta immunization. The rate of CXCR4+ cell was correlated to the numbers of the ASC (r = 0.966, P < 0.05). CXCL12 expression increased after pCMV4-hCGbeta and pCMV4-hCGbeta-C3d3 immunization, and appeared no difference between the two groups. These results above indicate that gene fusion of the molecular adjuvant C3d3 to hCGbeta can significantly enhance the antigen-specific antibody response, and the level of IgG ASCs in spleen via upregulation of CXCR4 expression on splenic B cells in DNA vaccination.