Abstract
AbstractTumor cells with the character of expressing tumor specific antigen could be used in immunotherapy. In this study, we explored the possibility of using PSA, a tumor maker for prostate cancer, as DNA vaccine for the treatment of prostate cancer in a mouse model. The disadvantage of DNA vaccine is its efficiency in inducing host immunity. To overcome this obstacle, a cytokine, interleukin-3(IL-3), was used to enhance its efficiency. IL-3 is a haematopoietic growth factor supports the growth and differentiation of pluripoietent stem cells leading to the differentiation of different types of blood cell.Using gene recombination technique, we constructed a plasmid of pIRES-IL3-PSA for the study of immune efficacy of DNA vaccine. To assess the expression efficiency of this plasmid, this plasmid was transfected into Tramp-C1 cells. The mRNA expression of this plasmid in TRAMP-C1-IRES-IL3-PSA cell was examined by RT-PCR. The results demonstated that IL-3 and PSA mRNAs could be expressed in Trammp-C1-IRES-IL3-PSA cells. To further evaluate the production of these proteins in this cell, ELISA assay was performed. The results demonstrated that these cells could express IL-3 protein, but not detectable PSA protein.Following two doses of intra-muscular injection of this plasmid, serum IgG1 and IgG2a levels were measured to evaluate the immune responses. ELISA result showed that the DNA vaccine couldn’t induce humoral immunity in mice. To further evaluate the cellular immune response, CTL assay was performed. CTL assay showed that DNA vaccine could induce CTL response against Nfsa-PSA cells. This indicated that DNA vaccine could induce cell-mediate immunity in mice. However, this response occurred in both C3H/HeN and C57BL/6J mice indicated that the observed response is likely due to the non-specific killing of NK cells.