Hennie R. Hoogenboom
Dyax Corp., Liège, Belgium; Liège University, Liège, Belgium

Targeting MHC-Peptide Complexes With Antibodies Derived From Phage Display Libraries

The permanent engraftment via gene therapy of autologous T cells with cell surface receptors directed towards tumor related antigens holds great promise for the development of more specific tumor therapies. We have explored the use of antibodies directed to MHC-peptide complexes (or ‘TCR-like’ antibodies) to generate CTLs with exquisite specificity for cancer cells. We have recently found that the generation of antibodies with such exquisite specificity using phage display libraries is surprisingly straight forward. Several examples of antibodies selected against HLA-A1 and HLA-A2 molecules complexed to peptides derived from cancer related antigens such as MAGE-A1, telomerase, MUC1 and gp100 will be discussed. The antibody specific for the HLA-A1-MAGE-A1 complex was in vitro affinity matured: a combination of light chain shuffling, heavy chain targeted mutagenesis, and in vitro selection of phage display libraries yielded an antibody derivative with an 18-fold improved affinity yet identical peptide fine specificity. The high and low affinity antibodies were expressed on primary human T lymphocytes as cell-surface anchored Fab fragments, to demonstrate that T cells expressing the high affinity Fab molecule eradicate tumor cells much more effectively. Furthermore, the gain in ligand-binding affinity resulted in a 2-log improvement in the detection of peptide/MHC complexes on MAGE-A1 peptide loaded cells.

In summary, phage display is a powerful method to obtain antibodies specific for MHC-peptide complexes; such selected human TCR-like Fab’s may prove to be very useful for monitoring and visualizing the expression of specific MHC-peptide complexes on the surface of tumor cells, antigen-presenting cells, and lymphoid tissues, as well as for developing a new family of targeting agents for immunotherapy. Furthermore, the strategy based on engraftment of T cells with in vitro engineered antibodies is an attractive alternative to the laborious, and in many cases unsuccessful generation of highly potent tumor-specific T lymphocytes.

Major collaborators:

Patrick Chames, Maastricht University, NL; Ralph A. Willemsen and Reinder Bolhuis, Clinical and Tumor Immunology, Department of Medical Oncology, Academic Hospital Rotterdam/Daniel den Hoed Cancer Center, Rotterdam, NL; Yoram Reiter, Faculty of Biology, Technion-Israel Institute of Technology, Haifa, Israel.