Inverse correlation of Vδ2 T-cell recovery with EBV reactivation after haematopoietic stem cell transplantation.

Epstein-Barr virus (EBV) reactivation remains a life-threatening complication in recipients of a haploidentical haematopoietic stem cell transplantation (haploHSCT). Reconstitution of adaptive T lymphocytes is generally compromised at the early stages following transplant, suggesting an important role of other effector cells in preventing EBV infection. Our previous studies demonstrated that recovery of CD4 CD8 T cells negatively correlated with EBV reactivation after haploHSCT. In this prospective study on 132 adult patients with haematopoietic malignancy, recovery of T-cell subpopulations was characterized post-haploHSCT. We showed that the median counts of peripheral Vδ2 cells were continuously lower in recipients with EBV reactivation compared with controls at 30, 60 and 90 days after haploHSCT (P values: 0·006, <0·001 and 0·019, respectively). Landmark study further indicated that the cumulative incidence of EBV reactivation was significantly decreased in recipients with higher day-30 Vδ2 counts. Activation of Vδ2 cells upon EBV reactivation was accompanied by an induction of cell apoptosis. Cytotoxic effect of Vδ2 cells on EBV-infected cells was confirmed by in vitro experiments. Together, our findings uncovered a significant correlation of recovered Vδ2 with EBV reactivation following haploHSCT. These results will help to better understand the intrinsic anti-virus immunity and develop γδ T-based therapy strategies after haematopoietic transplantation.