Two novel engineered antibody fragments binding to antigen CD20 were generated by fusing a murine IgM-type anti-CD20 singie-chain Fv fragment （scFv） to the human IgG1 CH2 （i.e., Cγ2） and CH3 （i.e., Cγ3） domain...Two novel engineered antibody fragments binding to antigen CD20 were generated by fusing a murine IgM-type anti-CD20 singie-chain Fv fragment （scFv） to the human IgG1 CH2 （i.e., Cγ2） and CH3 （i.e., Cγ3） domains with the human IgG1 hinge （i.e. Hγ）. Given the relationship between structure and function of protein, the 3-D structures of the two engineered antibody fragments were modeled using computer-aided homology modeling method. Furthermore, the relationship between 3-D conformation and their binding activity was evaluated theoretically. Due to the change of active pocket formed by CDRs, the HL23 （VH-Linker-VL-Hγ-Cγ2-Cγ3） remained its activity because of its preserved conformation, while the binding activity of the LH23 （VL-Linker-VH-Hγ-Cγ2-Cγ3） was impaired severely. Experimental studies by flow cytometry and fluorescence microscopy showed that HL23 possessed significantly superior binding activity to CD20-expressing target cells than LH23. That is to say, the order of variable regions could influence the binding activity of the fusion protein to CD20^＋ cell lines, which was in accordance with the theoretical results. The study highlights the potential relationship between the antibody binding activity and their 3-D conformation, which appears to be worthwhile in providing direction for future antibody design of recombinant antibody.展开更多
The c-erbB-2 proto-oncogene encodes a 185kDa protein p!85, which belongs to epidermal growth factor receptor family. Amplification of this gene has been shown to correlate with poor clinical prognosis for certain canc...The c-erbB-2 proto-oncogene encodes a 185kDa protein p!85, which belongs to epidermal growth factor receptor family. Amplification of this gene has been shown to correlate with poor clinical prognosis for certain cancer patients. The monoclonal antibody A21 which directed against p185 specifically inhibits proliferation of tumor cells overexpressing p185, hence allows it to be a candidate for targeted therapy. In order to overcome several drawbacks of murine MAb, we cloned its VH and VL genes and constructed the single-chain Fv (scFv) through a peptide linker. The recombinant scFvA21 was expressed in Escherichia coli and purified by the affinity column. Subsequently it was characterized by ELISA, Western blot, cell immunohistochemistry and FACS. All these assays showed the binding activity to extracellular domain (ECD) of p!85. Based on those properties of scFvA21, we further constructed the scFv-Fc fusion molecule with a homodimer form and the recombinant product was expressed in mammalian cells. In a series of subsequent analysis this fusion protein showed identical antigen binding site and activity with the parent antibody. These anti-p185 engineered antibodies have promised to be further modified as a tumor targeting drugs, with a view of application in the diagnosis and treatment of human breast cancer.展开更多
文摘Two novel engineered antibody fragments binding to antigen CD20 were generated by fusing a murine IgM-type anti-CD20 singie-chain Fv fragment （scFv） to the human IgG1 CH2 （i.e., Cγ2） and CH3 （i.e., Cγ3） domains with the human IgG1 hinge （i.e. Hγ）. Given the relationship between structure and function of protein, the 3-D structures of the two engineered antibody fragments were modeled using computer-aided homology modeling method. Furthermore, the relationship between 3-D conformation and their binding activity was evaluated theoretically. Due to the change of active pocket formed by CDRs, the HL23 （VH-Linker-VL-Hγ-Cγ2-Cγ3） remained its activity because of its preserved conformation, while the binding activity of the LH23 （VL-Linker-VH-Hγ-Cγ2-Cγ3） was impaired severely. Experimental studies by flow cytometry and fluorescence microscopy showed that HL23 possessed significantly superior binding activity to CD20-expressing target cells than LH23. That is to say, the order of variable regions could influence the binding activity of the fusion protein to CD20^＋ cell lines, which was in accordance with the theoretical results. The study highlights the potential relationship between the antibody binding activity and their 3-D conformation, which appears to be worthwhile in providing direction for future antibody design of recombinant antibody.
基金This work was supported by funds of Natural Science of Scientific Committee and Educational Committee of AN-HUI Province respectively, and Hi-tech Research and Development Program ("863" Program).
文摘The c-erbB-2 proto-oncogene encodes a 185kDa protein p!85, which belongs to epidermal growth factor receptor family. Amplification of this gene has been shown to correlate with poor clinical prognosis for certain cancer patients. The monoclonal antibody A21 which directed against p185 specifically inhibits proliferation of tumor cells overexpressing p185, hence allows it to be a candidate for targeted therapy. In order to overcome several drawbacks of murine MAb, we cloned its VH and VL genes and constructed the single-chain Fv (scFv) through a peptide linker. The recombinant scFvA21 was expressed in Escherichia coli and purified by the affinity column. Subsequently it was characterized by ELISA, Western blot, cell immunohistochemistry and FACS. All these assays showed the binding activity to extracellular domain (ECD) of p!85. Based on those properties of scFvA21, we further constructed the scFv-Fc fusion molecule with a homodimer form and the recombinant product was expressed in mammalian cells. In a series of subsequent analysis this fusion protein showed identical antigen binding site and activity with the parent antibody. These anti-p185 engineered antibodies have promised to be further modified as a tumor targeting drugs, with a view of application in the diagnosis and treatment of human breast cancer.
