Genetically engineered antibodies.

The technologyneeded to geneticallyengineer antibodiesis evolving rapidly and the potential utility of these novel re-agents is being explored with vigor. The process includes cloningof the antibodygenes, their in vitromanipulationand mutagenesis, expression in a suitable host/vectorsystem, and, for commercial production,scale-up, purification,and productevaluation.At each step, significantadvances have been achieved recently.Forexample:at first,antibodygenes were cloned from genomic librariesby using adjacent DNA probes;techniquesfor rapidsequencingby pnmerextension of total mRNA allowed more specificscreeningwith synthesized oligomers;finally,antibodygenes can now be created de novo by chemical synthesis. Moreover, such synthesis allows total control over the antibody sequence so that molecules of any configuration can be produced. New re-agents created in this way includemunne antibodieswhose constantregionsand variable-regionframeworkshave been replacedwith human sequence to enhance immunocompat-ibility with patients, to switch immunoglobulin class, or both. Additional Keyphrases: monoclonal antibodies gene synthesis expression vector immunotherapy chimeric anti-bodies Monoclonal antibodies have been available for more than 15 years (1). Despite their great utility in the laboratory and in diagnostic testing, and notwithstanding their high promise and the enormous research effort expended on them, they have yet to make a significant impact as clinical tools. Monoclonals are not used routinely to treat or image tumors, to provide passive immunization against infectious diseases, or for immunosuppression after organ transplant all uses for which they have been intended. Among the problems encountered in the effort to translate the diversity and specificity of monoclonals into clinically useful reagents are the following: #{149} The human immune response to foreign antibodies. #{149} Difficulty in making physical contact between the anti-body and the target antigen.. #{149} Change in antigen structure during tumor development or through mutation, as well as antigen shedding. #{149} Low affinity, inappropriate isotype, or nonoptimal sys-temic half-life of immunotherapeutic antibodies. #{149} Difficulty in producing sufficient quantities of antibody for therapy. In 1983, Oi et al. reported (2) that lymphoid cells can express cloned, transfected immunoglobulin genes. This demonstration opened the way to a new technology that may provide solutions to some of the problems listed above, of genes that code for antibodies. Because these methods have been shown capable of creating new kinds of antibody molecules the possibility is now enhanced that the undoubted promise of immunotherapy can someday be realized. The process by which genetically engineered antibody variants can be created has been reviewed extensively elsewhere (e.g., 9, 10). The major goals of such engineering include: #{149} Creating immunocompatible reagents by joining rodent variable regions to human constant regions. …