Affinity maturation of antiHER2 monoclonal antibody MIL5 using an epitope-specific synthetic phage library by computational design

Abstract

Increased affinities mainly equal to improved biological efficacy in many cases. By now, display methods including phage library are widely exploited to obtain higher affinity antibodies. Traditional library methods mainly focus on complementary determining region mutagenesis, in which extensive screening of variant combinations as well as large library capacity is required to find higher affinity clones. In this study, based on the modeling 3D complex structure of antigen (HER2)–antibody (MIL5) complex, the key residues of contact surface were predicted and identified to guide the synthetic phage library design. Then, epitope-specific site-directed mutagenesis phage library comprised of MIL5_scFv mutants was constructed, from which a higher affinity single chain antibody (M5scFv_ph) was screened out. Following experimental results showed that the novel antibody M5scFv_ph retained superimposed epitope to the parent antibody MIL5_scFv, and possessed similar tumor growth inhibitory activity in vivo on ovarian carcinoma xenografts.

Keywords:

• affinity maturation
• epitope-specific phage library
• HER2/ErbB2 antibody

Acknowledgments

We thank Mrs. Lang’s hard work in data collection of Flow cytometry (Xiaoling Lang from Beijing Mabworks Biotech Co., Ltd. Beijing 101111, China). Research was supported by grants from National Sciences Fund (No. 30901381, No. 31070820), National High Technology Research and Development Program (863 program, No. 2012AA02A302) and National key basic research development program (973 program, No. 2010CB833604).