Development of Human Anti-Murine T-Cell Receptor Antibodies in Both Responding and Nonresponding Patients Enrolled in TCR Gene Therapy Trials

Immune responses to gene-modified cells are a concern in the field of human gene therapy, as they may impede effective treatment. We conducted 2 clinical trials in which cancer patients were treated with lymphocytes genetically engineered to express murine T-cell receptors (mTCR) specific for tumor-associated antigens p53 and gp100. Twenty-six patients treated with autologous lymphocytes expressing mTCR had blood and serum samples available for analysis. Patient sera were assayed for the development of a humoral immune response. Adoptive cell transfer characteristics were analyzed to identify correlates to immune response. Six of 26 (23%) patients' posttreatment sera exhibited specific binding of human anti-mTCR antibodies to lymphocytes transduced with the mTCR. Antibody development was found in both responding and nonresponding patients. The posttreatment sera of 3 of these 6 patients mediated a 60% to 99% inhibition of mTCR activity as measured by a reduction in antigen-specific interferon-γ release. Detailed analysis of posttreatment serum revealed that antibody binding was β-chain specific in 1 patient whereas it was α-chain specific in another. A subset of patients treated with mTCR-engineered T cells developed antibodies directed to the mTCR variable regions and not to the constant region domains common to all mTCR. Overall, the development of a host immune response was not associated with the level of transduced cell persistence or response to therapy. In summary, patients treated with mTCR can develop an immune response to gene-modified cells in a minority of cases, but this may not affect clinical outcome.