AIM:Using a monoclonal antibody against gastric cancerantigen named MGbl to screen a phage-displayed randompeptide library fused with coat protein pⅢ in order to getsome information on mimotopes.METHODS:Through affinity enrichment and ELISA screening,positive clones of phages were amplified.10 phage cloneswere selected after three rounds of biopanning and the abilityof specific binding of the positive phage clones to MGb1-Abwere detected by ELISA assay(DNA sequencing wasperformed and the amino acid sequences were deduced)By blocking test,specificity of the mimic phage epitopeswas identified.RESULTS:There were approximately 200 times ofenrichment about the titer of bound phages after threerounds of biopanning procedures.DNA of 10 phage clonesafter the third biopanning was assayed and the result showedthat the positive clones had a specific binding activity toMGb1-Ab and a weak ability of binding to control mAb or tomouse IgG.DNA sequencing of 10 phage clones wasperformed and the amino acid sequences were deduced.According to the homology of the amino acid sequences ofthe displayed peptides,most of the phage clones had motifsof H(x)Q or L(x)S.And these 10 phage clones could alsopartly inhibit the binding of MGbl-Ab to gastric cancer cellKATO-Ⅲ.The percentage of blocking was from(21.0±1.6)%to(39.0±2.7)%.CONCLUSION:Motifs of H(x)Q and L(x)S selected andidentified show a high homology in the mimic epitopes ofgastric cancer associated antigen.There may be one or moreclones which can act as candidates of tumor vaccines. AIM: Using a monoclonal antibody against gastric cancerantigen named MGbl to screen a phage-displayed random peptide library fused with coat protein pIII in order to getome information on mimotopes. METHODS: Through affinity enrichment and ELISA screening, positive clones of phages were amplified.10 phage cloneswere selected after three rounds of biopanning and the ability of specific binding of the positive phage clones to MGb1-Abwere detected by ELISA assay (DNA sequencing was established and the amino acid sequences were deduced) By blocking test, specificity of the mimic phage epitopeswas identified .RESULTS : There were approximately 200 times ofenrichment about the titer of bound phages after threerounds of biopanning procedures. DNA of 10 phage clonesafter the third biopanning was assayed and the result showed that the positive clones had a specific binding activity to MGb1-Ab and a weak ability of binding to control mAb or tomouse IgG. DNA sequencing of 10 phage clones wasperformed and the amino acid sequences were deduced. According to the homology of the amino acid sequences of the displayed peptides, most of the phage clones had motifsof H (x) Q or L (x) S.And these 10 phage clones could alsopartly inhibit the binding of MGbl- Ab to gastric cancer cell KATO-III. The percentage of blocking was from (21.0 ± 1.6)% to (39.0 ± 2.7)%. CONCLUSION: Motifs of H (x) Q and L (x) S selected and identified to show a high homology in the mimic epitopes ofgastric cancer associated antigen. There may be one or moreclones which can act as candidates of tumor vaccines.