Ex vivo expansion of PR1-CTL elicited by autologous dendritic cells pulsed with PR1 peptide for adoptive immunotherapy of leukemia (B157)

Abstract

Cytotoxic T lymphocytes (CTL) specific for PR1, a HLA-A*0201-restricted peptide derived from proteinase 3, are capable of killing leukemia cells and contribute to the elimination of CML. Cytogenetic remission of CML after treatment with IFNα correlates with an expansion of PR1-CTL in patients. INFα is also an abundant cytokine produced by plasmacytoid DC which is critical for priming adaptive immune responses and MHC class I antigen cross-presentation. To determine whether a clinical trial with adoptively transferred PR1-CTL will benefit leukemia patients, we used INFα in combination with GM-CSF for ex vivo expansion of PR1-CTL and examined whether theses PR1-CTL can eliminate AML in the established NOD/SCID model. PBMC from HLA-A*0201+health donors were stimulated weekly with autologous DC pulsed with PR1 peptide in the presence of INFα and GM-CSF. By 3 weeks, there were 38.7% of PR1-CTL in the culture compared to 1.83% detected in the original sample using PR1-tetramer staining. We found that PR1-CTL generated in vitro can migrate to sites of disease and maintain their capacity to eliminate the human primary AML cells in NOD/SCID mice. Mice received AML alone had 72–88% blasts in a hypercellular marrow, whereas mice that received AML plus PR1-CTL had normal hematopoietic elements and only 10–11% blasts in a hypocellular marrow. We conclude that ex vivo expansion of PR1-CTL using this method is suitable for adoptive immunotherapy of AML.