Repeated PR1 and WT1 peptide vaccination in Montanide-adjuvant fails to induce sustained high-avidity, epitope-specific CD8+ T cells in myeloid malignancies.
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ABSTRACT: We previously showed that vaccination with one dose of PR1 and WT1 peptides induces transient anti-leukemia immunity. We hypothesized that maintenance of a sustained anti-leukemia response may require frequent boost injections.Eight patients with myeloid malignancies were enrolled in this phase II study, and 6 completed 6 injections of PR1 and WT1 peptides in Montanide-adjuvant with GM-CSF, every two weeks.Both high- and low-avidity PR1 or WT1-specific CD8(+) T cells were detected in all evaluable patients after the first vaccine dose. Repeated vaccination led to selective deletion of high avidity PR1- and WT1-specific CD8(+) T cells and was not associated with significant reduction in WT1-expression. Additional boosting failed to increase vaccine-induced CD8(+) T-cell frequencies further and in all patients the response was lost before the 6(th) dose. PR1- or WT1-specific CD8(+) T cells were not detected in bone marrow samples, excluding their preferential localization to this site. Following a booster injection three months after the 6(th) vaccine dose, no high-avidity PR1 or WT1-specific CD8(+) T cells could be detected, whereas low-avidity T cells were readily expanded.These data support the immunogenicity of PR1 and WT1 peptide vaccines. However, repeated delivery of peptides with Montanide-adjuvant and GM-CSF leads to rapid loss of high-avidity peptide-specific CD8(+) T cells. These results may offer an explanation for the lack of correlation between immune and clinical responses observed in a number of clinical trials of peptide vaccination. New approaches are needed to induce long-term high-avidity memory responses against leukemia antigens.
SUBMITTER: Rezvani K
PROVIDER: S-EPMC3046275 | biostudies-literature | 2011 Mar
REPOSITORIES: biostudies-literature
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