Antibody humanization is an important part of research in the production and preparation of recombinant antibodies (monoclonal antibodies). Antibody humanization is the process of development from murine antibodies to human antibodies. More than a hundred years ago, the revelation of the principles of specific binding of antibodies to antigens and passive immunological properties of antibodies opened up new ways of disease diagnosis. The introduction of monoclonal antibody technology in 1975 accelerated the widespread use of this method. Initially, most of the monoclonal antibodies used in clinical practice were mouse-derived monoclonal antibodies, and there were various limitations in the use of mouse-derived antibodies due to the specificity of human and mouse species. Although murine antibodies are specific to the target antigen and can bind specifically to the target antigen, they cannot activate the corresponding human effector systems, such as antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC), so that antigen-antibody reactions cannot occur normally. On the other hand, murine antibodies which enter the human body, may be seen as exogenous proteins, which can cause the human immune system to respond and produce specific antibodies using mouse antibodies as antigens, i.e. human anti-mouse antibody (HAMA), which is usually cleared quickly in the human body with a short half-life. Because of the limitations of mouse-derived antibodies in clinical applications, humanization of mouse-derived antibodies has been carried out using recombinant DNA technology to humanize the antibodies.
Humanization of mouse-derived antibodies is to genetically modify them to have an extremely similar profile to human antibody, thus evading recognition by the human immune system and avoiding the induction of HAMA. Two basic principles should be followed when performing antibody humanization: 1) to maintain or improve the affinity and specificity of the antibody. 2) to greatly reduce or largely eliminate the immunogenicity of the antibody. The antibody humanization process goes through three stages: chimeric antibody, humanized antibody and human antibody. Depending on the principle of action, humanized antibodies can be divided into four categories: chimeric antibody, reshaped antibody, resurfacing antibody and fully humanized antibody.
Figure 1. Schematic overview of mouse antibodies (green structural domain) to fully human antibodies (orange structural domain) and related antibody humanization. a Mouse-derived monoclonal antibodies. b Chimeric monoclonal antibodies: variable region is mouse-derived, remaining chains are human-derived. CH: heavy chain constant region; CL: light chain constant region; Fab and Fc: fragments resulting from proteolysis; VH: heavy variable region; VL: light chain variable region.【1】
Figure 2. Humanized Antibody Discovery Methods
In recent years, the emergence of humanized antibodies and fully human antibodies has brought new hope for clinical applications in the treatment of oncology, autoimmune diseases and cardiovascular diseases, as well as anti-transplant rejection and antiviral infections. These include reducing the adverse effects of traditional oncology drug therapy, acting as a tumor-specific marker, minimizing and avoiding rejection that occurs after transplantation, protecting the function of transplanted organs, and acting as an induction for solid organ transplantation therapy. The first chimeric Fab antibody-Abciximab (ReoPro) was approved by the US FDA in 1994 and has been widely used in the treatment of various cardiovascular diseases, mainly for the prevention of restenosis after coronary artery formation surgery. Recent studies have shown that humanized antibodies have promising applications in antiviral infections (e.g. HBV, HCV, HIV and other viral infectious diseases).
Figure 3. Abciximab (ReoPro)
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1.Rossotti MA, Bélanger K, Henry KA, Tanha J. Immunogenicity and humanization of single-domain antibodies. FEBS J. 2022 Jul;289(14):4304-4327. doi: 10.1111/febs.15809. Epub 2021 Mar 25. PMID: 33751827.
2.Lu RM, Hwang YC, Liu IJ, Lee CC, Tsai HZ, Li HJ, Wu HC. Development of therapeutic antibodies for the treatment of diseases. J Biomed Sci. 2020 Jan 2;27(1):1. doi: 10.1186/s12929-019-0592-z. PMID: 31894001; PMCID: PMC6939334.