Isolation and Evaluation of Specific Human Recombinant Antibodies from a Phage Display Library against HER3 Cancer Signaling Antigen

Background: the human epidermal growth factor receptor family comprises fourhomologous members: egfr (erbb1), erbb2 (her2), erbb3 (her3) and erbb4(her4).this family plays an important role in the signaling pathway and cellproliferation. the heterodimerization of her2 with her3 leads to tumor cellproliferation. monoclonal antibody to the human her3 receptor blocks her3 het-erodimerization and inhibits the growth of breast cancer cells. due to their human origin,small size, rapid penetration and high affinity properties, recombinant single chainantibodies (scfv) have been introduced as the most desired agents for cancerimmunotherapy. in this study, we use a phage display system to select specific scfvsagainst her3 for their use in cancer targeted therapy.methods: a phage antibody display library of scfv was panned against animmunodominant epitope of her3. phage rescue was performed on the library. thesupernatant that contained the appropriate scfv (109 pfu/ml) was added to animmunotube which was coated with the peptide. elution was done using log phase e.coli tg1. the clones were amplified by pcr and dna fingerprinted to select the specificclones against the epitope. the specificity of the selected antibodies was tested in elisa.results: the results represented two predominant patterns with the frequency of25%. the other patterns showed the frequencies of 5%-10%. scfv1 and scfv2demonstrated positive elisa with absorbances of 0.63 and 0.46, respectively whilethe absorbances of wells without peptide were 0.19 and 0.11, respectively. conclusion: in this study two specific scfvs were selected against her3 antigenin a successful panning process. phage elisa represented the specific binding of scfvsagainst her3.the selected scfvs reacted only with the corresponding peptides.however, no reaction with the other peptides was detected. the selected anti-her3scfvs have suggested that these human high affinity and small antibodies that bindspecifically to her3 epitope can be considered in her3 targeted approaches.