What is a chimeric antibody? Chimeric antibodies are structural chimeras made by fusing variable regions from one species like a mouse, with the constant regions from another species such as a human being. Chimerization of antibodies is a necessary process to reduce immunogenicity and increase serum half-life when preparing monoclonal antibodies (mAbs) for therapeutic purposes.
Researchers could change the constant regions from one species to another, as well as change from one subtype to another subtype within the same species. However, making it happen is not as straight and could be fairly challenging.
Sino Biological has genetically manipulated many antibodies by switching an antibody's constant regions to meet certain desired features. Our experience covers not only human and mouse antibodies, but also rabbit, rat, canine antibodies. Our professional scientists are at your service to support your chimeric antibody production.
Chimeric antibodies can be generated by fairly straightforward genetic engineering, by joining the immunoglobulin (Ig) variable regions of a selected mouse hybridoma to human Ig constant regions, and be used as such or as a first stage towards further humanization.
First, the spleen containing B cells from an immunized mouse is collected. The B cells are fused with myeloma cells to construct hybridoma and isolate a clone producing antigen-specific IgG. The DNA sequences coding mouse VH and VL are then isolated from the clone, as well as the DNA sequences coding human immunoglobulin constant regions from human cells. Mouse/human chimeric genes are constructed by genetic engineering and transfected into mammalian cells. Finally, the clone revealing a high level expression of chimeric IgG is selected and the IgGs are purified from the culture supernatant.
Chimeric monoclonal antibodies are very important and powerful for uses in therapeutics and immunoassays. For in vitro applications such as Immunohistochemistry studies or ELISA assay development, switching the antibody constant regions to match the species of the host or secondary antibody could significantly reduce the background staining.
After the FDA approval of rituximab, two additional chimeric antibodies, cetuximab and dinutuximab, reached the market for oncology indications. Cetuximab was generated by immunizing mice with purified EGFR and replacing the mouse constant domains of the mouse antibody 225 with those of human IgG1. The chimeric molecule, named C225, showed around five-fold higher affinity and increased tumor growth reduction than the parental mouse antibody.
Dinutuximab was developed from a murine antibody specific for GD2. The chimeric molecule (ch14.18), also a human IgG1, showed identical binding as the murine IgG2a antibody but, the ADCC was 50-fold to 100-fold higher than the parental mouse antibody when using human effector cells. Therefore, in addition to rendering less immunogenic molecules, chimerization overcame some of the drawbacks of the early murine monoclonal antibodies by generating therapeutic molecules with the same or improved affinity than the parental mouse antibodies but with enhanced effector functions.
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