Construction and expression of a small molecular chimeric antibody against human carcinoembryonic antigen

ObjectiveA small molecular antibody against human carcinoembryonic antigen was constructed and expressed in order to be used for radioimmunoimage and target therapy. MethodsThe gene of single chain antibody against CEA was cloned into expression vector pKpL-3a and expressed in E.coli pop2136. The antigen binding activity was analysed by ELISA. The light and heavy chain variable region genes were cloned into secretory expression vector pSCMH whose geneⅢ had been excised, and expressed in E.coli XL1-Blue. The antibody activity was assayed by ELISA. The light chain and Fd gene of CEA chimeric antibody were cloned into baculovirus expression vector pAcUW51 and expressed in sf9 cell. The activity, yield and affinity were analysed by ELISA. ResultsAfter being renatured by various methods, the specific antigen binding activity of expression product in E.coli pop2136 was not detected, nor was the secretory expression product in E.coli XL1-Blue.The small molecular chimeric antibody expressed in sf9 cell can specifically bind human CEA antigen and had the yield of 1.7 μg/mL.Competition ELISA showed that antigen epitope recognized by the chimeric antibody was the same as the parent McAb C50 ConclusionA small molecular chimeric antibody against CEA was successfully expressed in sf9 cell. Only in eucaryotic cells can some antibody genes express functional molecules. [