title: Phage-based molecular directed evolution yields multiple tandem human IgA affibodies with intramolecular binding avidity.
abstract: Affibodies are a group of affinity proteins that are based on a 58-amino-acid residue protein domain derived from one of the IgG-binding domains of staphylococcal protein A. A single human IgA affibody with high IgA affinity has been generated by directed evolution. It remains interesting whether tandem IgA affibody proteins could increase binding capacity. Here, we report the generation of multiple tandem IgA affibodies by directed evolution using a combinatorial phage library displaying the IgA affibody A1 and/or A2 linked with three random amino acids. These affibodies exhibited markedly increased IgA binding capacity, as shown by enzyme linked immunosorbent assay, immunoblotting and surface plasmon resonance assays. We further showed that these tandem IgA affibodies displayed preferential binding to intact IgA molecules compared to individual IgA chain, suggesting intramolecular binding avidity. Our data demonstrates that artificial multiple tandem human IgA affibodies with relevant biological binding avidity were successfully yielded by phage-based molecular evolution. These results have broad implications for the design and development of binding proteins that target important biological molecules.
authors.affiliation: Department of Microbiology, Shanghai Key Laboratory of Medical Biodefense, Second Military Medical University, Shanghai 200433, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Cao
authors.forename: Zong-Mei
authors.initials: ZM
authors.lastname: Wen
authors.forename: Song-Hua
authors.initials: SH
authors.lastname: Deng
authors.forename: Xia
authors.initials: X
authors.lastname: Zhou
authors.forename: Qiu-Li
authors.initials: QL
authors.lastname: Chen
authors.forename: Wen-Ting
authors.initials: WT
authors.lastname: Liao
authors.forename: Shao-Hua
authors.initials: SH
authors.lastname: Jiang
authors.forename: Jian-An
authors.initials: JA
authors.lastname: Jia
authors.forename: Zhong-Tian
authors.initials: ZT
authors.lastname: Qi
authors.forename: Shu-Han
authors.initials: SH
authors.lastname: Sun
authors.forename: Wei
authors.initials: W
authors.lastname: Pan
mesh_terms: D019020:Directed Molecular Evolution / Q000379:methods*; D006801:Humans; D007070:Immunoglobulin A / Q000737:chemistry* / Q000235:genetics; D019151:Peptide Library; D011993:Recombinant Fusion Proteins / Q000737:chemistry* / Q000235:genetics*; D013205:Staphylococcal Protein A / Q000737:chemistry* / Q000235:genetics*
chemical_list: D007070:Immunoglobulin A; D019151:Peptide Library; D011993:Recombinant Fusion Proteins; D013205:Staphylococcal Protein A