Abstract
In a first clinical trial, 45 patients with advanced ovarian carcinoma and recurrences were treated with the murine monoclonal anti-idiotypic antibody (Ab2) designated ACA125 for active immunotherapy. The monoclonal antibody (MAb) ACA125 mimics a specific epitope of the tumor-associated antigen CA125 expressed by most malignant ovarian tumors. Patients with CA125-positive tumors are immunologically tolerant to CA125, which could be overcome by the use of an anti-idiotypic antibody as a surrogate for the tumor antigen CA125. An immunological response to the anti-idiotype ACA125 in these patients was associated with a statistically significant survival prolongation. Humoral immunity to ACA125 was assessed by induction of anti-anti-idiotypic antibodies (Ab3) directed against CA125. Using flow cytometric detection methods we observe alterations of the intracellular cytokines IFN-γ, IL-2, and IL-4 at the single-cell level during the course of immunization. There was a strong increase of intracellular IFN-γ and IL-2 characteristic for a Th1 cell type immune response after treatment with ACA125. A delayed induction of Th2 type response, which promotes antibody-mediated immunity by B cells, could also be detected. The understanding of the kinetics of Thl and Th2 responses could be important to improve treatment schedules for effective immunotherapy with anti-idiotype vaccines.
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