The development of antibody

Antibodies play an important role in the diagnosis, treatment and prevention of diseases. The development of antibody technology has gone through three generations. That is, the first generation of antibodies - polyclonal antibodies; the second generation of antibodies - monoclonal antibody; and the third generation of antibodies - genetic engineering antibodies. Monoclonal antibodies, as a new type of biological agents, have been shown to play an important role in the prevention, diagnosis and treatment of human diseases. However, the monoclonal antibodies produced by hybridoma technology are mostly murine, which belong to xenogeneic proteins and have immunogenicity. Therefore, repeated use of monoclonal antibodies in human body can produce different degrees of human anti-mouse antibody (HAMA) reaction, thus weakening the effectiveness of its treatment, and causing damage to the organs clearing antibodies. In addition, mouse-derived monoclonal antibodies are not effective in activating complement and Fc receptor-related effector systems in humans, so their application is limited.

Humanization methods of the modified mouse monoclonal antibody mainly include the replacement of the constant region of the mouse monoclonal antibody with the human constant region (which is named chimeric antibody), the replacement of the part of the mouse monoclonal antibody with the human sequence except the complementary determinant region (which is named humanized antibody), and the direct screening of the human antibody gene from the antibody library.

The advantages of chimeric antibodies

Preparation of humanized antibody

Compared with other humanized antibodies, chimeric antibodies have the following advantages: simple technical route, easy operation; good antibody integrity, long retention time in vivo; affinity and specificity of mouse antibodies have been guaranteed, and have good clinical application prospects.

Types of chimeric antibodies

In recent years, the development of chimeric antibodies is very rapid, and has become an important field in the application of antibodies. There are three types of chimeric antibodies: chimeric IgG, chimeric Fab and chimeric F (ab’) 2.

Chimeric IgG antibody

Most chimeric antibodies currently constructed are human IgG forms. For example, in the process of constructing chimeric IgG antibody, it is most important to accurately clone the variable region of mouse antibody gene.

Antibody variable region genes can be cloned from genomes or cDNA libraries using phages, but both methods have relative limitations. The type of antibody constant region should be chosen purposefully when constructing the chimeric antibody constant region, because the interaction between the human antibody constant region and complement and Fc receptor and the function of triggering cell lysis are not the same in different subgroups. Because antibodies have complex immune regulatory functions, some of which may lead to some side effects, it is possible to improve some biological functions of antibodies by point mutation of a few amino acids in the constant region, so that antibodies can play a more effective role in the immune regulation, thus eliminating their side effects.

Chimeric Fab and chimeric F (ab) 2 antibodies

In order to solve the problem of poor permeability of macromolecular antibodies, chimeric F (ab) 2 and chimeric Fab (ab) 2 antibodies were designed and prepared by recombinant DNA technology. The preparation principle of chimeric Fab is to recombine functional antibody variable region genes with human antibody Kappa chain and heavy-chain CH1 constant region genes, and clone them into expression vector to construct human-mouse chimeric Fab gene expression vector, and then transfer them into host cells for expression. Because Fab is a unit of active antigen binding fragment, its apparent affinity is relatively low. Moreover, the molecular weight of Fab is only about 50kDa, which is easy to be removed from the blood by glomerular filtration. Therefore, it has a short retention time in the target tissue, so it is not suitable for some clinical treatment alone. Because Fab and F (ab) 2 maintain antigen binding capacity and greatly reduce the non-specific adhesion of Fc segment in normal tissues and cells, they can be used as a good carrier of drugs for immuno-directed diagnosis and treatment.

Prospects for chimeric antibodies

Genetically engineered antibody technology puts the antibody gene under the manpower control range. The molecular size, affinity and cytotoxicity of the antibody molecule can be designed and operated according to the requirements of the prepared biological agents, which can not be achieved by hybridoma technology. Chimeric antibody is one of the most mature genetic engineering antibodies among the numerous genetic engineering antibodies. In recent years, great progress has been made in chimeric antibody technology. The theory of chimeric antibody has been developed from the original human mouse antibody to the necessary technology platform for the production of humanized antibodies. How to efficiently express chimeric antibodies in eukaryotic expression system is another important factor restricting the further development of chimeric antibody technology. The in-depth study of this aspect will certainly push the development of chimeric antibody to a new stage of development.

Author's Bio: 

Antibodies-based treatments have been one of the hottest therapies in recent years. Some IgG-based biotherapeutic agents have achieved an obvious efficacy in the treatment of a wide variety of diseases, including cancers and immune disorders. Creative Biolabs can provide the most cost-effective therapeutic antibody products for both in vitro and in vivo researches, been a leading provider of antibody-based therapeutic agents.