OBJECTIVETo construct a recombined phage vaccine and to evaluate the efficiency of this phage vaccine against EGFR-positive tumors.

METHODST7 phage display system was used to display five fragments of the extracellular domain of chicken EGFR. The EGFR was expressed as a fused protein on the surface of the T7 phage 10B capsid protein. The EGFR expression of the phage vaccine was verified by Western-blot analysis. Anti-EGFR antibody was detected by ELISA. Splenic lymphocytes of the immunized mice were separated and used to determine the immunotoxic effect against A431 cells. The phage vaccines were injected into C57 mice 4 times before Lewis lung cancer cells inoculation. Tumor volume was recorded to evaluate the anti-tumor effect of each vaccine.

RESULTSFive phage vaccines inserted with the chicken EGFR gene were successfully constructed. Western blot assay showed that the extracellular domain of chicken EGFR proteins were displayed on the surface of the phage. Specific antibody was induced in the immunized mice, compared with the control group. Splenic lymphocytes of the immunized mice were shown to be immunotoxic against A431 cells. The killing rates of the experimental groups were higher than that of control group (P < 0.001, t-Student test). The highest killing rate was (45.74 +/- 7.21)%. The tumor growth was inhibited in the experimental groups compared with those of control groups (P < 0.05 in C1, C2, C3, C4 groups, P > 0.05 in C5 group).

CONCLUSIONOur results demonstrated that recombined EGFR phage vaccines may be used to induce therapeutic anti-tumor immunity against EGFR-positive tumors.