Absolute Antibody is developing engineered antibodies for the research and diagnostics markets. A major advantage of using sequenced and engineered recombinant antibodies is the ability to create chimeric antibodies (Figure 1). A chimeric antibody (cAb) is an antibody made by fusing the antigen binding region (variable domains of the heavy and light chains, VH and VL ) from one species like a mouse, with the constant domain (effector region) from another species such as a rabbit. The chimeric antibodies retain the original antibody’s antigen specificity and affinity and are valuable tools for in vivo and in vitro research. Our current list of catalog items is given below.
Chimeric antibodies for in vivo research
- Biotherapeutic research – Many therapeutic monoclonal antibodies have been generated originally in mice. Chimeric antibodies were made to reduce the immunogenicity of mouse antibodies before humanization was widely adopted. Examples of chimeric antibodies containing human constant domains and mouse variable domains in the clinic include infliximab, rituximab and abciximab (please note some of these are available in our Research Grade Biosimilars range). Since a chimeric antibody is substantially cheaper to make than a fully humanized antibody, they may be useful at the early stages of biotherapeutics research. Indeed, we routinely make them as controls as part of our humanization service.
- In vivo research – ‘Species switched’ chimeric antibodies allow the use of an antibody in animal models with reduced anti-species immune responses. Quite often antibodies may be generated in one species, for example rat, and the disease animal model being used maybe another, for example mouse – here a chimeric antibody with mouse constant regions (partially “murinized”) will result in reduced immunogenicity. Note that by subtype switching or using our Fc Silent™ mutations you can also modulate effector functions (ADCC or CDC).
Example Product – OX86; the original monoclonal antibody [OX86] (which has been extensively used in vivo) is rat anti-mouse CD134 antibody (Ab00110-6.1), using our proprietary recombinant antibody platform, we have generated a mouse anti-mouse version Ab00110-1.1.
Chimeric antibodies for Assay Development and Diagnostics
Use as calibrators (standards) or controls in Immunoassays
Serological immunoassays designed to detect a specific antibody in patient samples rely on serum calibrators (standards) and or positive controls. Calibrators can be used in an immunoassay to generate standard curves to quantify the test antibody concentration in the patient serum and or as positive controls to assess the performance of the assay and reagents. For a serological assay, calibrators (standards) are derived from seropositive serum or plasma and are heterogeneous by nature and thus suffer from significant drawbacks including:
- Lot to lot variability with respect to antibody class IgG, IgM composition, specificity and affinity
- Difficulty in sourcing large amounts with high titre
- Limitations with respect to characterisation
Chimeric antibodies as calibrators (standards) or positive controls offer a viable and more reliable alternative to serum based calibrators. Advantages of using chimeric antibody calibrators (standards) or positive controls in immunoassays are:
- Minimal lot to lot variation with respect to antibody class, composition, titre, specificity and affinity therefore is a more consistent and reliable calibrator (standard)
- Chimeric antibodies can be generated in unlimited quantities and are homogeneous in specificity and affinity
- Fully characterised calibrator (standard)
Chimeric antibody calibrators (standards) are applicable to any diagnostic immunoassays designed to detect the presence of human antibodies specific for a given antigen.
Example Product – At Absolute Antibody we have generated an anti-PEG [E11] mouse/human chimeric IgG monoclonal antibody (Ab00116-10.0) which has successfully been used to as a calibrator (standard) in a PEG immunoassay (ELISA) (Hale, G, et al., 2016 –in preparation).
Interference from heterophilic antibodies
Heterophilic antibodies are found in human patient serum and plasma. They are poly-reactive antibodies recognising IgG from different animal species. These antibodies are non-specific, have no defined antigen and bind to the Fc region of the assay antibody causing a false positive test signal. Heterophilic antibodies found in patient serum react with mouse (HAMA) and rat IgG. Since conventional specific and high affinity monoclonal antibodies can only be obtained from the mouse and rat, heterophilic antibodies present a limitation for a diagnostic test. Chimeric monoclonal antibodies (in particular human chimeric antibodies) are an obvious solution to the problem. Human chimeric antibody can be genetically engineered by fusing the mouse or rat (or other species) variable regions (VH and VL) with a human constant domain (Figure 1).
Chimeric antibodies for in vitro R&D
- Chimeric antibodies allow the antibody to be tailored to a specific application without being limited by the original antibody species
- Chimeric antibodies allow the researcher the flexibility to adapt the monoclonal antibody of their choice to any platform or binding module/surface whilst retaining the original antibody’s specificity and sensitivity for a particular antigen, for example: protein microarray (chip) platforms or support beads.
- Flow cytometry and IHC : Chimeric antibodies can circumvent potential non-specific binding issues associated with binding of secondary antibodies to the test cell or tissue (common problem for Flow Cytometry and IHC).
As an example – we have generated a family of anti-myc tag antibodies for use as controls or affinity capture antibodies (eg. ChIP assays; immunoprecipitation) for a number of platforms (see data sheet). The original anti- c-myc monoclonal antibody [9E10] is a mouse monoclonal IgG1 (Ab00100-1.1), using our proprietary recombinant antibody platform, we have generate a rat IgG1 (Ab00100-6.1), IgG2B (Ab00100-8.0), rabbit IgG (Ab00100-23.0) and human IgG1 (Ab00100-10.0), see below.
Current Catalog of Chimeric Antibodies
We offer a range of recombinant chimeric antibodies and fusion proteins for in vivo and in vitro applications. Our antibody engineering platform allows us to quickly generate chimeric versions of any monoclonal antibody in our catalog. We also offer a range of species specific and genetically engineered Fc domains (Fc Silent™) and species and isotype switching- for further information contact firstname.lastname@example.org.
You can find our full product catalogue here.
If a monoclonal antibody of your interest is not listed in our expanding product line, please contact email@example.com. For bulk and bespoke custom orders of you own antibodies please contact firstname.lastname@example.org.