The entry of non-human antibodies into the human body can cause serious body rejection, which in turn affects the safety and therapeutic effect of the antibody in clinical application. Therefore, it is necessary to humanize the antibody to minimize the heterogeneity of the antibody. And keep its specificity and affinity unchanged.
Each variable region of the antibody contains three amino acid sequence hypervariable regions, which are binding sites of the antigen and are complementary to the structure of the antigenic determinant, and are referred to as antibody complementarity determining regions (CDRs), amino acid sequences and spaces of the CDRs. Polymorphism in the structure is a factor determining the heterogeneity and affinity of antibodies. Other amino acids in the variable region serve as a backbone support moiety, called Framework Residue (FR), which is not in direct contact with the antigen. The amino acid sequence and spatial structure are relatively conservative, providing a skeleton for maintaining the typical three-dimensional structure of the antibody, indirectly affecting the antibody. The specificity and affinity of the antibody constant region and the antibody variable region FR are relatively conservative during the evolution process, and the species are specific to the species, which is the main factor causing the body to reject the reaction. Therefore, the basic principle of humanization antibody is to preserve the conserved sequence of the antibody as a human sequence, reduce the body rejection reaction, replace the antigen-binding region with the sequence of the antibody produced by the animal immunization, and maintain the specificity and affinity of the antibody.
Humanization of antibodies requires the use of genetic engineering methods. Therefore, humanized antibodies belong to genetically engineered antibodies, and humanised antibodies can be classified into chimeric antibodies, modified antibodies, and fully humanized antibodies depending on the degree of antibody sequence modification.
Modified antibody
The modified antibody is also called CDR grafting antibody, and the CDR grafting method is used for preliminary humanization of the antibody, that is, the 6 CDR regions of the non-human antibody are moved to the human skeleton, due to the human FR skeleton. The region will indirectly affect the specificity and affinity of the antibody. Based on the CDR grafting, the individual amino acid residues in the human FR framework region are further adjusted to further improve the specificity and affinity of the CDR-grafted antibody.
Full human antibody
The entire sequence of the fully human antibody antibody is a human sequence, which is realized by the antibody library technology. The main antibody library technology is a phage display and ribosome display technology.
Antibody Library Technology Basic Approach to Obtaining Fully Humanized Antibodies: Selecting a Variable Region Light Chain (or Heavy Chain) Gene of a Parent Mouse Monobody to Pair with a Variable Region Heavy Chain (or Light Chain) Gene Library of a Human Antibody The mouse-to-human hybrid antibody library is constructed, and the corresponding antigen is used to select a clone capable of producing a specific binding antibody, thereby obtaining an Fv fragment capable of binding to the parent mouse monoclonal antibody and having specific binding ability to the composition. Human heavy chain (or light chain) variable region gene, combined with another human antibody variable region light chain (or heavy chain), construct a human antibody library, and again use antigen screening to obtain specificity and mouse The human antibody with the same source parent antibody is identical.
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