Humanized antibodies are antibodies from non-human species whose protein sequences have been modified to increase their similarity to the antibody variants produced naturally in humans. The process of "humanization" is usually applied to monoclonal antibodies developed for administration to humans (eg, antibodies developed as anti-cancer drugs). Humanization can be needed when the process of developing specific antibodies involves generations in a non-human immune system (as in mice). The sequence of antibody proteins produced in this way is partially different from homologous antibodies that occur naturally in humans, and is therefore potentially immunogenic when administered to human patients (see also human antibody antibodies). There are other types of antibodies that are developed. International Nonproprietary Names of humanized antibodies end in -zumab , as in omalizumab (see Nomenclature of monoclonal antibodies).
Human antibodies are different from chimeric antibodies. The latter also has a protein sequence that is made more similar to human antibodies, but carries a larger stretch of non-human protein.
Video Humanized antibody
Penggunaan DNA rekombinan dalam proses humanisasi
The humanization process takes advantage of the fact that the production of monoclonal antibodies can be achieved by using recombinant DNA to make constructions capable of expression in mammalian cell cultures. That is, the gene segments capable of producing antibodies are isolated and cloned into cells that can be grown in bioreactors so that the antibody proteins produced from cloned gene DNA can be harvested en masse . Steps involving recombinant DNA provide an intervention point that can be easily exploited to alter the protein sequence of expressed antibodies. Changes in the structure of antibodies achieved in the humanization process are therefore all effected through techniques at the DNA level. Not all methods for lowering antibodies intended for human therapy require humanization measures (eg the appearance of phage) but basically all depend on the same technique allowing "insertion" or "swapping-out" part of the antibody molecule.
Maps Humanized antibody
Differences from "chimeric antibody"
Humanization usually looks different from the formation of human-rat chimera antibodies. Thus, although the formation of chimera antibodies is usually performed to achieve more human-like antibodies (by replacing the Fc rat of the antibody region with that of humans) this simple chimera is not usually referred to as humans. In contrast, the sequence of proteins from human antibodies is essentially identical to that of human variants, although non-human origins from some segments of the complementarity determination region (CDR) are responsible for the antibody's ability to bind to its target antigen.
Name of chimeric antibody contains stem -xi - . Examples of chimeric antibodies approved for human therapy include abciximab (ReoPro), basiliximab (Simulect), cetuximab (Erbitux), infliximab (Remicade) and rituximab (MabThera). There are also some examples of chimerics currently in clinical trials (eg bavituximab, see the list that can be sorted for additional examples).
Humanizing through a chimeric intermediate
The humanization process may, however, include the creation of a human-mouse chimera in the initial step (Fab mouse is connected to human Fc). After that chimera may be more humane by the selective change of the amino acid sequence in the Fab part of the molecule. The process must be "selective" to maintain the specificity originally developed by antibodies. That is, because the Fab CDR part is crucial for antibody ability to tie the intended target, the amino acids in these parts can not be changed without the risk of damaging the development goal. Apart from the CDR segment, part of the Fab sequence that differs from that in humans can be corrected by exchanging the appropriate individual amino acids. This is achieved at the DNA level using mutagenesis.
The naming of the human chimera includes the stem for both titles ( -xi - -zu - ). Otelixizumab is an example of a human chimera currently in clinical trials for the treatment of rheumatoid arthritis and diabetes mellitus.
Humanization by inserting the relevant CDR into human antibodies "scaffolding"
It is possible to produce human antibodies without creating a chemical intermediate. The "direct" creation of human antibodies can be achieved by incorporating the appropriate segment of CDR coding (called 'donor', responsible for the desired binding properties) into the "scaffold" of human antibodies (so-called 'acceptor'). As discussed above, this is achieved through recombinant DNA methods using vectors and proper expression in mammalian cells. That is, once the antibodies are developed to have the desired properties in the mouse (or other non-humans), the DNA coding for the antibodies can be isolated, cloned into vectors and sorted. The DNA sequence corresponding to the antibody CDR can then be determined. Once the exact sequence of the desired CDR is known, strategies can be designed to incorporate this sequence appropriately into constructs containing DNA for human antibody variants. This strategy can also use the synthesis of linear DNA fragments based on CDR sequence readings.
Alemtuzumab is an early example of antibodies whose humanization does not include chimeric intermediates. In this case, the monoclonal dubbed "Campath-1" was developed to bind CD52 using the mouse system. The hypervariable loop from Campath-1 (which contains CDRs and thus gives its ability to bind to CD52) is then extracted and inserted into the framework of human antibodies. Alemtuzumab is approved for the treatment of chronic lymphocytic leukemia of B cells and is currently in clinical trials for a variety of other conditions including multiple sclerosis.
Antibodies for human therapies are taken down without a mouse
There is a technology that completely avoids the use of mice or other non-human mammals in the process of discovering antibodies to human therapy. Examples of such systems include various "display" methods (especially the phage look) as well as methods that exploit elevated B-cell levels that occur during a human immune response.
Display method
It uses the selective principle of producing specific antibodies but exploits micro-organisms (as in the phag display) or even cell-free extract (as in the ribosome display). This system relies on the creation of a "library" of antibody genes that can be completely derived from human RNA isolated from peripheral blood. The direct product of this system is an antibody fragment, usually Fab or scFv).
This means that, although the antibody fragments created using the display method are a complete human sequence, they are not full antibodies. Therefore, the process is essentially identical to humanization used to combine and express inherited affinity in full antibodies.
Adalimumab (Humira) is an example of an approved antibody for human therapy created through the appearance of phage.
Antibodies from human patients or vaccine recipients
It is possible to exploit human immune reactions in the discovery of monoclonal antibodies. Simply put, human immune responses work in the same way as in mice or other non-human mammals. Therefore, people who experience challenges to their immune systems, such as infectious diseases, cancer or vaccination are potential sources of monoclonal antibodies directed at the challenge. This approach seems very appropriate for the development of anti-viral therapy that exploits the principles of passive immunity. Variants of this approach have been shown in principle and some people find their way into commercial development.
See also
- List of monoclonal antibodies
References
Source of the article : Wikipedia
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