Production

Monoclonal antibodies are artificially produced antibodies.

The technique of cell fusion followed by selection is widely used in the production of monoclonal antibodies.

Body cells can be cultured from a single cell in a controlled medium. The chromosomes involved are large and easily visible as a result of staining (coloring), so individual chromosomes and their arrangements are identifiable Modern techniques allow to fuse the cells in a way that two nuclei function in one cell, which leads to the transfer of DNA into growing culture cells.

Several somatic-cell genetic techniques involve the fusion of two cells in such way that the nuclei from both parents are brought within one joint cytoplasm. Spontaneous fusion of animal and human cells in culture occurs infrequently, but the rate increases substantially when certain viruses that have lipoprotein envelopes similar to the plasma membranes of animal cells are present.

Cell fusion can also be accelerated by the addition of polyethylene glycol, which causes cell plasma membranes to adhere to those of any surrounding cells. In most fused animal cells the nuclei eventually also fuse, producing the desired cells that contain chromosomes from both “parents”. Hybrids between cultured cells from different mammals also have been widely used.

Early production of monoclonal antibodies was fraught with obstacles. The biggest problem was that the antibodies the process yielded were mouse antibodies (murine), and the human immune system frequently reacted against them, as with any other foreign substance entering the body. That reaction produced problems ranging from rashes to swelling of the joints to kidney failure and death; it also destroyed the antibodies and defeated the mission.

Even so, scientists went back to the labs and found a number of ways to address the problem successfully, largely by finding a variety of ways to make the antibodies more human and less murine. One technique is to create “chimeric” antibodies by replacing some of the problematic regions of mouse content with human protein in a fusion process that results in antibodies that are about 65 percent human. At least four monoclonals now on the market in the U.S. are chimerics, including a drug called ReoPro, which binds to platelets to prevent blood clots.

Another approach has been a grafting process that produces what are known as “humanized MAbs,” wherein some 95 percent of the resulting molecule is human in origin. This technique is employed in such drugs as Herceptin, a monoclonal antibody used to target breast cancer.

Meanwhile, other researchers have developed techniques to create hybridomas that produce fully human MAbs, including at least one successful effort in England to fuse fully human B cells and immortalized cells, although scientists say it remains unclear what the long term implications and efficacy of the technology might be.

Other researchers have found ways to genetically alter the mice themselves to produce fully human antibodies, by causing the animals to contain human antibody genes. Still others are experimenting with an altogether different process that dispenses with the mice. “Phage display” (the word is an abbreviated form of bacteriophage, a virus that infests bacteria) involves inserting DNA from B cells into bacteria and then allowing phages to infect the bacteria. As the phages replicate, they also recreate the proteins from the antibody genes, which can be cultured.

Marketwarch reports that total sales of monoclonal antibodies hit $48 billion in 2010 and is expected to exceed $70 billion by 2015.



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