The Association of HLA-E Ligand and NKG2 Receptor Variation with Relapse and Mortality after Haploidentical Related Donor Transplantation.

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Recurrence of blood malignancy is the major cause of mortality after hematopoietic cell transplantation. NKG2 receptor/HLA-E ligand complexes play a fundamental role in the surveillance and elimination of transformed cells but their role in the control of leukemia in transplantation is unknown. We tested the hypothesis that gene variation of patient and/or donor HLA-E ligand and donor NKG2C-NKG2A receptors are associated with the risks of relapse and mortality (primary endpoints) and GVHD and non-relapse mortality (secondary endpoints) after haploidentical transplantation. We retrospectively defined donor NKG2 receptor haplotypes and patient HLA-E ligands in 1629 haploidentical related transplantations. HLA-E residue 107 was genotyped in patients and donors. Single nucleotide polymorphisms descriptive of NKG2C and NKG2A haplotypes were characterized in donors. Overall mortality, relapse, non-relapse mortality and chronic GVHD were studied using Cox regression models. Acute GVHD was studied by logistic regression. The hazard of relapse for patients transplanted from NKG2C-del/del donors was 51% lower than that from wt/wt donors (hazard ratio, HR, 0.49 [95% confidence interval, CI, 0.26-0.89) contributing to a HR for mortality of 0.62 (95% CI, 0.38-1.02). The HR of mortality among patients transplanted from a donor with 2 vs. 0 copies of the NKG2A rs35909400-rs2734440-rs12824474 CCC haplotype was HR 2.28 (95% CI, 1.34-3.86). The HRs of mortality for ArgArg and ArgGly patients compared to GlyGly patients were 1.42 (95% CI, 1.11-1.82) and 1.43 (95% CI, 1.13-1.81), respectively. Hazard ratios for non-relapse mortality for patients with ArgGly or ArgArg genotypes compared to patients with GlyGly genotype were HR 1.60 (95% CI, 1.06-2.41) and HR 1.79 (95% CI, 1.21-2.66), respectively. Assessment of donor receptor/patient ligand pairings showed that among Arg-positive patients, the HR of mortality from donors with any wt-CCC/CCC haplotype was HR 2.52 (95% CI, 1.45-4.38) relative to donors with any wt-non CCC/CCC haplotype. The success of haploidentical transplantation may be defined by the cumulative effects of donor NKG2 receptor and patient HLA-E ligand polymorphisms. Patient HLA-E ligand and donor NKG2C-NKG2A receptor haplotypes shed new light on their role in the control of malignancy.