[The experimental study on idiotypic DNA vaccine against human B-cell lymphoma to induce antitumor immune response].

The purpose of this study was to evaluate whether the DNA vaccine containing idiotypic gene fragment of human B-cell lymphoma cell line Namalwa could elicit the specific anti-idiotypic immune response in vivo. The candidate gene fragment of the lymphoma cell, variable region of heavy chain (VH) of the membranous immunoglobulin, was amplified using Ig superfamily primers by means of RT-PCR. Also, the intact cDNA of murine monocyte chemoattractant protein (MCP-3) was cloned and used as the adjuvant molecular. The two gene fragments of VH and MCP-3 were fused together by 8aa linker peptide with recombinant PCR. Subsequently, the fusion gene fragment was cloned into eukaryonic expression vector pcDNA3.1 to construct DNA vaccine plasmid. Prior to the immunization, the transient transfection coupled with RT-PCR was performed to prove that the recombinant plasmid could express in eukaryonic cells in right way. Then two groups of mice were immunized by intramuscular injection with DNA vaccine and mock plasmid pcDNA3.1 respectively. Three times of injection were performed with 100 micro g plasmid respectively at the beginning of the experiment and 2, 4 weeks after the first injection for all the groups. FACS analysis was chosen to detect the antibodies recognizing lymphoma cells at different time following vaccination. The results demonstrated that specific anti-idiotypic antibody could be detected in the group of DNA vaccine immunized mice as early as eight weeks after the first immunization. Further test demonstrated that the anti-idiotypic antibody could maintain for at least twenty weeks with high titer. Anti-idiotypic antibodies were elicited in three of five mice of the DNA vaccine immunized group. The Abs of DNA vaccine immunized mice could only recognize Namalwa cell line instead of another unrelated human cell line A549. There is no cellular response detected in the DNA vaccine immunized mice. It is concluded that the DNA vaccine containing fused MCP3-VH sequence could elicit specific anti-idiotypic antibody against B-cell lymphoma in vivo and could be used in further study of DNA vaccine against B-cell lymphoma. The results would provide the basis for further studies and optimization of this therapeutic strategy on patients with B-lymphoproliferative disease.