Donor NKG2C homozygosity contributes to CMV clearance after haploidentical transplantation

CMV infection remains an important cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Several investigators have reported that adaptive NKG2C(+) NK cells persistently expand during CMV reactivation. In our study, 2 cohorts were enrolled to explore the relationships among the NKG2C genotype, NKG2C(+) NK cell reconstitution, and CMV infection. Multivariate analysis showed that donor NKG2C gene deletion was an independent prognostic factor for CMV reactivation and refractory CMV reactivation. Furthermore, adaptive NKG2C(+) NK cells’ quantitative and qualitative reconstitution, along with their anti-CMV function after transplantation, was significantly lower in patients grafted with NKG2C(wt/del) donor cells than in those grafted with NKG2C(wt/wt) donor cells. At day 30 after transplantation, quantitative reconstitution of NKG2C(+) NK cells was significantly lower in patients with treatment-refractory CMV reactivation than in patients without CMV reactivation and those with nonrefractory CMV reactivation. In humanized CMV-infected mice, we found that, compared with those from NKG2C(wt/del) donors, adaptive NKG2C(+) NK cells from NKG2C(wt/wt) donors induced earlier and stronger expansion of NKG2C(+) NK cells as well as earlier and stronger CMV clearance in vivo. In conclusion, donor NKG2C homozygosity contributes to CMV clearance by promoting the quantitative and qualitative reconstruction of adaptive NKG2C(+) NK cells after haploidentical allo-HSCT.