Absence of pre-transplant T cell response against LAA is associated with Flt3-ITD mutation and increased relapse-risk in AML patients with HSCT.

Aims: This study aimed to examine changes in the repertoire of functional T-cells specific for six leukemia-associated antigens (LAA), including WT1, PRAME, MUC1, CCNA1, NPM1, and NPM1c, during immune reconstitution following allogeneic transplantation of hematopoietic stem cells (HSCT) in patients with acute myeloid leukemia.

Patients & methods: LAA-specific T cell response was measured by ELISPOT- IFNγ and intracellular cytokine staining in 47 patients before starting conditioning therapy (baseline) and 7 months after HSCT.

Results: The positive cumulative LAA-specific T cell response before HSCT was associated with a decreased risk of relapse after HSCT. The prevalent genetic aberration - an internal tandem duplication of Fms 3 - related receptor tyrosine kinase, which has been previously implicated in immune escape mechanisms, is presented here for the first time as a factor associated with the absence of an adaptive T cell response against multiple LAAs. T-cell specific responses against wild-type and mutated NPM1 antigens were less frequent in the study cohort and did not correlate with mutations in the NPM1 gene.

Conclusions: Our results showed that the T-cell response to LAA can be reconstituted after HSCT. Measurement of functional pre-transplant T-cell responses against multiple LAAs could help to find patients with an increased risk of relapse.