Immunotherapy of advanced ovarian carcinomas by activation of the idiotypic network.

The positive effect of an immunotherapy using tumor-associated antigens or tumor cells of ovarian carcinomas has not yet been proven. Although many unique tumor-associated antigens have been described and a tumor rejection could be seen in occasional cases, the failure of the immune system to destroy tumor cells is not clearly understood. An alternative approach is to initiate the idiotypic network utilizing antibodies (Ab1 or 2) against a tumor-associated antigen, which induces the production of anti-idiotypic-antibodies (Ab2 beta), mimicking the "internal image" of the tumor-associated antigen. These antibodies are able to induce a specific antitumor immunity in two ways: (1) the Ab2 can present the critical epitope in a different way and so modulates the immune system, or (2) it can induce the production of an Ab3, which by itself binds to the tumor antigen. Our first results on 22 patients with advanced ovarian carcinomas show that the induction of an anti-idiotypic antibody (Ab2 beta) against OC 125 mimicking the TAA Class III CA 125 leads to a prolongation of the survival rate also for extended stages. We see a beneficial role of the induction of the idiotypic network against a tumor-associated antigen showing delayed clinical courses of the disease after vaccination of the patients with antibody fragments of the OC 125.