Delayed-type hypersensitivity reactions to tumor-associated antigens in colon carcinoma patients immunized with an autologous tumor cell/Bacillus Calmette-Guérin vaccine.

Five different colon tumor-associated antigens (CTAA) were tested for their ability to induce an immune response in vivo and in vitro in ten colon carcinoma patients immunized with an irradiated autologous tumor cell/Bacillus Calmette-Guérin vaccine (active specific immunization) after resection of the primary tumor. The CTAA were defined by two different human monoclonal antibodies (MCA 1688 and MCA 28A32) derived by immortalization of peripheral blood B-lymphocytes from an active specific immunization patient. Delayed-type cutaneous hypersensitivity responses against a mixture of CTAA 28A32-50K and -32K were positive in seven of ten patients tested. In vitro T-cell responses upon stimulation with CTAA 28A32-32K were found to be positive in seven of ten patients and correlated with delayed-type cutaneous hypersensitivity responses to the antigen mixture. These data suggest that CTAA 28A32-32K might contain an important tumor-related T-cell epitope. Moreover, this method is suitable to define potential future candidates for antitumor vaccine development.