Riassunto analitico
NPM1-mutated protein, a leukemia-specific antigen, may be considered an ideal target for AML immunotherapy. We investigated the dynamics of NPM1-mutated-specific T cells on bone marrow (BM) and peripheral blood (PB) samples, collected from 31 adult NPM1-mutated AML patients throughout the disease course, and stimulated with mixtures of 18 short and long peptides (9-18mers), derived from the complete spanning of C-terminal of NPM1-mutated protein. Two 9-mer peptides, namely LAVEEVSLR and AVEEVSLRK (13.9-14.9), were identified as the most immunogenic epitopes. NPM1-mutated-specific T cells producing IFNγ were shown by ELISPOT assay after stimulation with peptides 13.9-14.9 in 51/61 (83.6%) BM and 63/85 (74.1%) PB samples. Significantly higher responses were found in PB samples, in patients younger than 60 years, without FLT3 gene mutations and following allogeneic HSCT. An inverse correlation between kinetics of MRD and anti-leukemic specific T cells was observed. Cytokine production and memory profiles documented NPM1-mutated-specific T cells, mainly producing IFNγ and IL2. Either Effector Memory or Central Memory T cells were predominantly identified among IFNγ–producing and IL2–producing T cells, respectively. Moreover, NPM1-mutated-specific CTLs can be expanded from NPM1-mutated AML patients or primed in healthy donors. Cr51-release assays showed the ability of 13.9-14.9 peptides combined with CLAVEEVSLRK, to induce cytolytic activity against primary leukemic blasts or PHA-blasts pulsed with different peptide pools. We observed spontaneous occurrence and persistence of NPM1-mutated-specific T cells, which may contribute to maintain long-lasting remissions. Future studies are warranted to investigate the potential role of either autologous or allogeneic adaptive immunotherapy in NPM1-mutated AML.
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