Discovery of targets for tumor immunotherapy using phage display technology

Sammanfattning: This thesis has focused on the development of methods and their applications for the identification of antibodies reactive with tumor associated antigens (TAA). The phage display technology provides a powerful mean to generate antibodies potentially useful for tumor immunotherapy. A phage antibody displays on its surface an antibody fragment encoded by a gene inserted in the phage genome. The phage antibody can be selected by antigen binding from a diverse population of phage, each displaying antibodies with unique specificities. Any antibody gene repertoire that can be genetically assembled, including naive, immune and synthetic repertoires of human antibody genes can be expressed and displayed on phage. Antibody identification by phage display has primarily been performed with purified antigens for selection. This thesis demonstrates that a crude antigen source, i.e. sections of tissues and intact cells can be used directly and dissected as a complex antigen for phage selection, providing a tool for mutual discovery of new antibodies and their targets. A gradual method development in model systems, from straight positive selection using cells or tissue sections to ultimately achieve the most sophisticated subtractive selection method using tissue sections is described in the enclosed papers. The application of these using a phage antibody library constructed from malignant melanoma or colon cancer immunized Cynomolgus Macaque monkeys led to the identification of putative novel tumor specificities. The identified TAA were highly, homogeneously, frequently and selectively expressed on the cell surface in clinical tumor samples and represent potentially excellent targets for tumor immunotherapy.