Covalent linkage of antigens to plasma membrane proteins on the surface of dendritic cells as a means of enhancing immunogenicity

Vaccination strategies employing dendritic cells (DCs) have been used extensively in both pre-clinical models as well as in clinical trials for the treatment of human tumors. One of the challenges for optimizing the treatment of cancer through DC immunotherapy is determining the most efficacious method of delivering antigen (Ag) to DCs. A simple approach to increase the uptake and presentation of Ag by DCs is proposed and tested in this thesis work. This approach involves the covalent coupling of Ag to proteins present on the DC's surface. The mild biochemical modification employed by this approach avoids its denaturation of the Ag. In addition, this reaction proceeds under physiological pH in isotonic media thus preserving cell viability. In this study a model tumor antigen, β-galactosidase (β-gal) was covalently coupled to proteins on the surface of DCs. DCs with covalently linked Ag on their surface were compared to DCs pulsed with soluble Ag for the ability to generate a tumor specific immune response in mice. Covalently linked β-gal-DCs proved to be superior to soluble β-gal loaded DCs in generating both protective and therapeutic anti-tumor immunity. This technique has the potential to be used with a wide range of antigens such as peptide fragments of known tumor or microbial proteins or tumor cell and bacterial lysates that contain a variety of antigenic components. Preliminary studies with a murine B cell tumor, and with human lung tumors provide a foundation upon which to test the efficacy of this Ag covalent linkage protocol using both naturally expressed tumor specific antigens and tumor cell lysates.