Distinct activities of Vδ1 T-cells upon different cytomegalovirus reactivation status after haematopoietic transplantation.

Cytomegalovirus (CMV) reactivation is the most frequent viral infectious complication correlating to non-relapse mortality after allogeneic haematopoietic cell transplantation (alloHCT). The intrinsic anti-CMV immunity has not been completely elucidated. γδ T-cells have drawn increasing attentions due to their distinct biological features and potential ability against viral infections. Previous studies reported a general association of γδ T-cells or Vδ2-negative γδ T-cells with CMV reactivation. Whereas researches for the direct responses and specific functions of γδ T subsets remain limited, especially in the scenario of alloHCT. Herein, we initially demonstrated that Vδ1 T-cells directly and independently recognized cell-free CMV and CMV-infected target cells, and inhibited CMV replication in vitro. The anti-CMV effect of Vδ1 T-cells was partially through TCRγδ, TLR2 and NKG2D receptor pathways. Further investigation about the anti-CMV characteristics of Vδ1 T-cells was performed in a clinical cohort with different CMV reactivation status after alloHCT. We found that occasional CMV reactivation remarkably increased the recovery levels and stimulated the functional activity of Vδ1 T-cells. Whereas disability of Vδ1 T-cells was observed upon refractory CMV reactivation indicating the differential responses of Vδ1 T-cells under different CMV reactivation status. CXCL10 and IFN-β that were dramatically induced by occasional CMV reactivation could re-activate the deficient Vδ1 T-cells from recipients with refractory CMV reactivation. These findings unveiled the distinct activities of Vδ1 T-cells in anti-CMV immunity after alloHCT and may help develop novel strategies for the treatment of CMV infectious diseases.