Development of an oral DNA vaccine against MG7-Ag of gastric cancer using attenuated salmonella typhimurium as carrier.
OBJECTIVE
To develop an oral DNA vaccine against gastric cancer and evaluate its efficacy in mice.


METHODS
The genes of the MG7-Ag mimotope and a universal Th epitope (Pan-DR epitope, PADRE) were included in the PCR primers. By PCR, the fusion gene of the two epitopes was amplified. The fusion gene was confirmed by sequencing and was then cloned into pcDNA3.1(+) plasmid. The pcDNA3.1 (+)-MG7/PADRE was used to transfect an attenuated Salmonella typhimurium. C57BL/6 mice were orally immunized with 1X10(8) cfu Salmonella transfectants. Salmonella harboring the empty pcDNA3.1(+) plasmid and phosphate buffer saline (PBS) were used as negative controls. At the 6th week, serum titer of MG7-Ag specific antibody was detected by ELISA. At the 8th week cellular immunity was detected by an unprimed proliferation test of the spleenocytes by using a ((3)H)-thymidine incorporation assay. Ehrlich ascites carcinoma cells expressing MG7-Ag were used as a model in tumor challenge assay to evaluate the protective effect of the vaccine.


RESULTS
Serum titer of antibody against MG7-Ag was significantly higher in mice immunized with the vaccine than that in control groups (0.841 vs 0.347, P<0.01; 0.841 vs 0.298, P<0.01), while in vitro unprimed proliferation assay of the spleenocytes showed no statistical difference between those three groups. Two weeks after tumor challenge, 2 in 7 immunized mice were tumor free, while all the mice in the control groups showed tumor formation.


CONCLUSIONS
Oral DNA vaccine against the MG7-Ag momitope of gastric cancer is immunogenic. It can induce significant humoral immunity against tumor in mice, and the vaccine has partially protective effects.
Guo
Chang-Cun
CC
Institute of Digestive Disease, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, Shaanxi Province, China.
Ding
Jie
J
Pan
Bo-Rong
BR
Yu
Zhao-Cai
ZC
Han
Quan-Li
QL
Meng
Fan-Ping
FP
Liu
Na
N
Fan
Dai-Ming
DM
D000284:Administration, Oral; D000818:Animals; D000951:Antigens, Neoplasm / Q000235:genetics* / Q000276:immunology*; D019496:Cancer Vaccines / Q000008:administration & dosage*; D005822:Genetic Vectors; D051379:Mice; D008810:Mice, Inbred C57BL; D012486:Salmonella typhimurium / Q000235:genetics*; D013274:Stomach Neoplasms / Q000517:prevention & control*; D014162:Transfection; D019444:Vaccines, DNA / Q000008:administration & dosage*
D000951:Antigens, Neoplasm; D019496:Cancer Vaccines; D019444:Vaccines, DNA