ABSTRACT
Objective To obtain alpaca single domain antibody targeting Her2.Methods An alpaca was immunized with human recombination Her2 protein mixed with Freund's adjuvant.Total RNA was extracted from the alpaca's blood and was used to synthesize first strand cDNA.Single domain antibody variable region (VHH) gene of the alpaca was amplified by PCR and cloned into pMES4 vector for library construction.After screening, E.coli BL21 (DE3) was transformed with selected clones and was induced with IPTG for the expression of recombinant proteins.The nanobody was purified by nickel ion affinity chromatography column.The affinity of the nanobodies to Her2 was tested.Results After the second round of screening, two antibody clones were selected, H3 and H5.The affinity of H5 was 8.106×10-10mol/L.Histochemistry results showed that H5 could recognize Her2 antigen in breast tumor tissue.Conclusion An Her2 specific nanobody derived from alpaca is obtained through phage display library screening, which can recognize human Her2 antibody in human breast tumor tissue.