Phenotypic and Functional Characterization of NK Cells in αβT-Cell and B-Cell Depleted Haplo-HSCT to Cure Pediatric Patients with Acute Leukemia.

Raffaella Meazza,Mattia Algeri,Franco Locatelli,Lorenzo Moretta,Alessandro Moretta,Letizia Muccio,Maria Cristina Mingari,Daria Pagliara,Daniela Pende,Pietro Merli,Paolo Canevali,Andrea Pession,Michela Falco,Natalia Colomar-Carando,Alice Bertaina,Mariella Della Chiesa,Francesca Moretta,Simona Sivori,Fabrizio Loiacono,Valentina Indio,Federica Galaverna

doi:10.3390/cancers12082187

Abstract

NK cells can exert remarkable graft-versus-leukemia (GvL) effect in HLA-haploidentical hematopoietic stem cell transplantation (haplo-HSCT). Here, we dissected the NK-cell repertoire of 80 pediatric acute leukemia patients previously reported to have an excellent clinical outcome after αβT/B-depleted haplo-HSCT. This graft manipulation strategy allows the co-infusion of mature immune cells, mainly NK and γδT cells, and hematopoietic stem cells (HSCs). To promote NK-cell based antileukemia activity, 36/80 patients were transplanted with an NK alloreactive donor, defined according to the KIR/KIR-Ligand mismatch in the graft-versus-host direction. The analysis of the reconstituted NK-cell repertoire in these patients showed relatively high proportions of mature and functional KIR+NKG2A−CD57+ NK cells, including the alloreactive NK cell subset, one month after HSCT. Thus, the NK cells adoptively transfused with the graft persist as a mature source of effector cells while new NK cells differentiate from the donor HSCs. Notably, the alloreactive NK cell subset was endowed with the highest anti-leukemia activity and its size in the reconstituted repertoire could be influenced by human cytomegalovirus (HCMV) reactivation. While the phenotypic pattern of donor NK cells did not impact on post-transplant HCMV reactivation, in the recipients, HCMV infection/reactivation fostered a more differentiated NK-cell phenotype. In this cohort, no significant correlation between differentiated NK cells and relapse-free survival was observed.

Highlights

Hematopoietic stem cell transplantation from an HLA-haploidentical donor, represented by a relative sharing half of HLA alleles with the recipient, is a suitable option for patients with hematologic diseases in urgent need of an allograft, but lacking an HLA-matched donor [1]
We focused on Allo C2, since KIR2DL1 displays a more and a greater number of of HLA-C1/C1 than HLA-C2/C2 leukemia in additionthan to the pediatric stringent recognition
Since within the activating receptors involved in natural cytotoxicity NCRs play a major role in leukemia recognition [21], we examined the NK-cell expression of NKp46, which may vary among different donors, privileging those with higher surface density

Summary

Introduction

Hematopoietic stem cell transplantation from an HLA-haploidentical donor (haplo-HSCT), represented by a relative sharing half of HLA alleles (i.e., one haplotype) with the recipient, is a suitable option for patients with hematologic diseases in urgent need of an allograft, but lacking an HLA-matched donor [1]. Haplo-HSCT became feasible in the 1990s by intensifying the conditioning regimen to prevent graft rejection, and by the infusion of “megadoses” of CD34+ purified cells, depleting T cells responsible of the occurrence of graft-versus-host disease (GvHD) [2]. This graft manipulation causes a prolonged lymphopenia and a delayed immune reconstitution, leading to severe opportunistic infections. Controversial results have been described in un-manipulated (T-cell replete) haplo-HSCT, with studies showing that NK alloreactivity was associated with a better [6,7,8] or worse [9,10,11] clinical outcome.

Methods

Results

Conclusion