ABSTRACT
<p><b>OBJECTIVE</b>To investigate the specific anti-tumor immunity induced by gene immunization with ectopic hCG encoding gene.</p><p><b>METHODS</b>BALB/c mice were immunized with plasmid TR421-hCGbeta coding for hCGbeta and mock DNA for 3 times at 3 weekly intervals. The level of specific anti-hCGbeta IgG antibody in the serum was determined by ELISA at the indicated time in the two groups. The growth inhibitory activity of the sera against tumor cells was examined in vitro by [(3)H]-Thymidine incorporation assay. Specific lympho-proliferation versus hCGbeta was detected by [(3)H]-Thymidine incorporation assay with hCGbeta protein or inactivated SP2/0-hCGbeta cells as specific stimulating antigen. Cytotoxic T lymphocyte (CTL) activity of the splenocytes derived from the immunized mice was measured by [(3)H]-Thymidine release assay. Protective assay was performed by subcutaneous inoculation of SP2/0-hCGbeta cells into the immunized mice. The weight and formation rate of the tumor were evaluated after challenge.</p><p><b>RESULTS</b>All mice immunized with plasmid TR421-hCGbeta developed high level of anti-hCGbeta antibodies, which could inhibit the growth of Hela cells and SP2/0-hCGbeta cells compared with the serum from animals immunized with mock DNA (P < 0.05). The high-level specific lympho-proliferation against hCGbeta protein or/and inactivated SP2/0-hCGbeta cells were shown in TR421-hCGbeta immunized mice, whereas no significant proliferative activity was found in mock DNA immunized animals (P < 0.01). A strong cytotoxic activity against SP2/0-hCGbeta in TR421-hCGbeta immunized mice was found. Inoculation of SP2/0-hCGbeta cells into the mice immunized with mock DNA developed large tumors within 25 days. But a marked reduction of tumor weight and formation rate was found after the tumor cells challenge in the mice immunized with TR421-hCGbeta plasmid DNA (P < 0.01).</p><p><b>CONCLUSION</b>The gene immunization of ectopic hCGbeta encoding gene, eliciting high-level of specific humoral and cellular immune responses, could inhibit the growth of tumor cells harboring ectopic hCGbeta in vitro and in vivo.</p>