OBJECTIVETo develop an oral DNA vaccine based on MG(7)-Ag mimotope of gastric cancer using attenuated Salmonella typhimurium and evaluate its efficacy and protective effect.

METHODSThe eukaryotic expression vector including the MG(7)-Ag mimotope and a Th epitope was constructed, and then transduced into an attenuated Salmonella typhimurium to get the oral DNA vaccine. C57BL/6 J mice were orally immunized with 1 x 10(8) cfu Salmonella transfectants, with Salmonella harboring empty plasmid, with phophate buffered saline (PBS) as control. At the 6th week, serum titer of MG(7) antibody was detected by ELISA. In the 8th week, a [(3)H]-thymidine incorporation assay was performed to test the proliferation of murine spleen cells to the stimulant of MG(7)-Ag mimicry peptide. At the same time, Ehrlich ascites carcinoma cells expressing MG(7)-Ag were used in tumor challenge assay to evaluate the protective effect of the immunization.

RESULTSThe oral DNA vaccine induced MG(7) antibody in mice, while in vivo unprimed proliferation assay of the spleenocytes showed no difference among the three groups. Two weeks after tumor challenge, 2 in 7 immunized mice were tumor free, while none in the control group was protected.

CONCLUSIONOral DNA vaccine based on the MG(7)-Ag momitope is immunogenic. It is able to induce specific immunity response against tumor in mice, and the vaccine is partially protective.

Administration, Oral ; Amino Acid Sequence ; Animals ; Antigens, Neoplasm ; blood ; genetics ; immunology ; Base Sequence ; Cancer Vaccines ; genetics ; immunology ; therapeutic use ; Epitopes ; genetics ; immunology ; Female ; Mice ; Mice, Inbred C57BL ; Molecular Mimicry ; genetics ; immunology ; Molecular Sequence Data ; Plasmids ; genetics ; Polymerase Chain Reaction ; Stomach Neoplasms ; drug therapy ; immunology ; Treatment Outcome ; Vaccines, DNA ; genetics ; immunology ; therapeutic use

Epidermal growth factor receptor (EGFR) is an attractive target for tumor therapy because it is overexpressed in the majority of solid tumors and the increase in receptor expression levels has been linked with a poor clinical prognosis. Also it is well established that blocking the interaction of EGFR and the growth factors could lead to the arrest of tumor growth and possibly result in tumor cell death. A13 is a murine monoclonal antibody (mAb) that specifically binds to various sets of EGFR-expressing tumor cells and inhibits EGF-induced EGFR phosphorylation. We isolated human immunoglobulin genes by guided selection based on the mAb A13. Four different human single chain Fvs (scFvs) were isolated from from hybrid scFv libraries containing a human VH repertoire with the VL of mAb A13 and a human VL repertoire with the VH of mAb A13. All the 4 scFvs bound to EGFR-expressing A431 cells. One scFv (SC414) with the highest affinity was converted to IgG1 (ER414). The ER414 exhibited ~17 fold lower affinity compared to the A13 mAb. In addition the ER414 inhibited an EGF-induced tyrosine phosphorylation of EGFR with much lower efficacy compared to the A13 mAb and Cetuximab (Merck KgaA, Germany). We identified that the epitope of A13 mAb is retained in ER414. This approach will provide an efficient way of converting a murine mAb to a human mAb.
Animals ; Antibodies, Monoclonal, Humanized/*genetics/immunology/therapeutic use ; Antibody Affinity ; Cell Line, Tumor ; Directed Molecular Evolution/*methods ; Epitope Mapping ; Epitopes/genetics/immunology/therapeutic use ; Humans ; *Immunotherapy ; Mice ; Neoplasms/*therapy ; Phosphorylation/drug effects ; Protein Binding ; Receptor, Epidermal Growth Factor/*antagonists & inhibitors/immunology ; Selection, Genetic ; Single-Chain Antibodies/*genetics/immunology/therapeutic use

AIMTo investigate the antitumor immunity by a dendritic cell (DC) vaccine encoding secondary lymphoid chemokine gene and tumor lysate on murine prostate cancer.

METHODSDC from bone marrow of C57BL/6 were transfected with a plasmid vector expressing secondary lymphoid chemokine (SLC) cDNA by Lipofectamine 2,000 liposome and tumor lysate. Total RNA extracted from SLC+lysate-DC was used to verify the expression of SLC by reverse transcriptase-polymerase chain reaction (RT-PCR). The immunotherapeutic effect of DC vaccine on murine prostate cancer was assessed.

RESULTSWe found that in the prostate tumor model of C57BL/6 mice, the administration of SLC+lysate-DC inhibited tumor growth most significantly when compared with SLC-DC, lysate-DC, DC or phosphate buffer solution (PBS) counterparts (P < 0.01). Immunohistochemical fluorescent staining analysis showed the infiltration of more CD4(+), CD8(+) T cell and CD11c(+) DC within established tumor treated by SLC+lysate-DC vaccine than other DC vaccines (P < 0.01).

CONCLUSIONDC vaccine encoding secondary lymphoid chemokine and tumor lysate can elicit significant antitumor immunity by infiltration of CD4(+), CD8(+) T cell and DC, which might provide a potential immunotherapy method for prostate cancer.

Animals ; Antibodies, Neoplasm ; biosynthesis ; Antigens, Neoplasm ; immunology ; CD11 Antigens ; immunology ; Cancer Vaccines ; immunology ; therapeutic use ; Cell Line ; Chemokines ; biosynthesis ; Dendritic Cells ; immunology ; metabolism ; Epitopes ; immunology ; Fluorescent Antibody Technique ; Killer Cells, Natural ; immunology ; Lymphocytes ; metabolism ; Male ; Mice ; Mice, Inbred C57BL ; Neoplasm Transplantation ; Plasmids ; genetics ; Prostatic Neoplasms ; immunology ; pathology ; prevention & control ; Reverse Transcriptase Polymerase Chain Reaction ; T-Lymphocytes ; immunology