Richard A. Lerner
Title:”Selecting Antibodies from Intracellular Combinatorial Libraries that Regulate Cell Fate”
The Scripps Research Institute, 10550 North Torrey Pines Road, MB-10, La Jolla, CA 92037, USA
Date:March 20, Thursday, 16.15
Host: Bengt Samuelsson
Contact:Tatiana Goriatcheva, Nobelkansliet, Nobel Forum, tel:+46-8-52487805, firstname.lastname@example.org
The advent of combinatorial antibody libraries changed immunochemistry from a science that required the use of live animals to one in which the antibody repertoire is generated in a test tube. Such repertoires, whose nature is controlled by the experimenter, are orders of magnitude larger than any natural repertoire. This approach circumvents the problem of immunological tolerance and has enabled the rapid generation of many antibody reagents and therapeutics. It is especially important that one works with very large numbers so that rare antibodies can be identified and their comparative sequences used to give insight into the chemistry of antigen-antibody union for a particular target. As an example, the power of large numbers was used to generate broadly neutralizing antibodies against the influenza virus. Such antibodies pointed to new, highly conserved regions of the virus that are vulnerable to immunological attack, thereby providing a roadmap to regions of the virus that can be used for the generation of universal vaccines.
Recently, combinatorial antibody libraries have been converted to a format that allows infection of eukaryotic cells and the expression of antibodies within various cellular compartments, including the plasma membrane. Such intracellular antibodies make possible the direct selection of antibodies that regulate cellular phenotypes. In its most powerful form, the selection uses an autocrine system because the target and the antibody both reside within the same cell. In these cases each cell becomes a selection system unto itself, and when agonist activity gives rise to a fluorescent signal, it becomes possible to examine approximately two million events per hour. Such intracellular libraries have been used to generate antibodies that are functional equivalents of erythropoietin, granulocyte colony stimulating factor, thrombopoietin, and adiponectin, as well as those that induce dendritic and neural cells. These antibodies activate CD34+ bone marrow stem cells not only to proceed along the usual lineage-specified pathways, but also to differentiate in unexpected ways to form, for example, neural or brown fat cells. Finally, antibodies have been generated that protect cells from virus-induced death or that induce pluripotent cells by replacing transcription factors. Thus, one can think of the use of intracellular combinatorial antibody libraries as a forward proteomics approach to generate agonists and antagonists that both perturb known pathways and allow the discovery of new pathways to a given phenotype.