Data from NY-ESO-1 DNA Vaccine Induces T-Cell Responses That Are Suppressed by Regulatory T Cells

Abstract

<div>Abstract<p><b>Purpose:</b> Different vaccination strategies against the NY-ESO-1 antigen have been employed in an attempt to induce antitumor immune responses. Antigen-specific effector T-cell responses have been reported in a subset of vaccinated patients; however, these responses have not consistently correlated with disease regression. Here, we report for the first time clinical and immune responses generated by the NY-ESO-1 DNA vaccine administered by particle-mediated epidermal delivery to cancer patients.</p><p><b>Experimental Design:</b> Eligible patients received treatment with the NY-ESO-1 DNA vaccine. Clinical outcomes and immune responses were assessed.</p><p><b>Results:</b> The NY-ESO-1 DNA vaccine was safely administered and induced both antigen-specific effector CD4 and/or CD8 T-cell responses in 93% (14 of 15) of patients who did not have detectable pre-vaccine immune responses. Despite the induction of antigen-specific T-cell responses, clinical outcomes consisted predominantly of progressive disease. Detectable effector T-cell responses were inconsistent and did not persist in all patients after completion of the scheduled vaccinations. However, high-avidity CD4 T-cell responses that were either undetectable pre-vaccine or found to be diminished at a later time during the clinical trial were detected in certain patients' samples after <i>in vitro</i> depletion of regulatory T cells.</p><p><b>Conclusions:</b> Regulatory T cells play a role in diminishing vaccine-induced antigen-specific effector T-cell responses in cancer patients. The NY-ESO-1 DNA vaccine represents a feasible immunotherapeutic strategy to induce antigen-specific T-cell responses. Counteracting regulatory T-cell activity before vaccination may lead to prolonged effector T-cell responses and possibly antitumor responses in cancer patients.</p></div>