Development of a novel anti-HER2 scFv by ribosome display and in silico evaluation of its 3D structure and interaction with HER2, alone and after fusion to LAMP2B.

HER2 is a member of epidermal factor receptor (EGFR) family which is overexpressed in breast cancer, ovarian cancer and gastric cancer. Development of new binders for cancer cell surface receptors and expressing them at the surface of exosomes would be a great approach in targeted cancer therapy. We found a high affinity scFv against HER2 using ribosome display with the approach of applying it as a targeting moiety at the surface of exosomes by fusion to lysosomal associated membrane protein 2B (LAMP2B). We also provide some structural information about the ribosome display selected scFv (scFv HFS2) through modeling the 3D structure of scFv HFS2 using RosettaAntibody and docked it at the extracellular domain of HER2. We also evaluated the structure of scFv HFS2 and its binding to HER2 after fusion to LAMP2B. Our results showed no significant change in 3D structure of scFv HFS2 when fused to LAMP2B (RMSD 1.3) and interaction analysis represented that scFv HFS2 binds HER2 domain III before and after fusion to LAMP2B. Although binding domain of scFv HFS2 on HER2 was the same at both state, residues involved in their interactions showed significant differences as it was probably due to the spatial hindrance of scFv HFS2 when fused to LAMP2B through a short linker and it should be considered before proceeding to experiment.