Donor–recipient TCR comparisons reveal limited αβ but persistent Vδ2⁺ γδ clonotype overlap after CMV reactivation in allo-HSCT
Allogeneic hematopoietic stem cell transplantation (allo-HSCT) profoundly reshapes T-cell immunity. Moreover, CMV reactivation is known to drive clonal T-cell expansion after allo-HSCT, but it is still unclear how donor-derived ab and gdT-cell clonotypes persist and differentiate in recipients, especially after abT-cell-depleted grafts. We aimed to characterize donor-recipient TCR sharing, gd T-cell clonal dynamics, and effector programming after CMV reactivation in allo-HSCT recipients who received either abT-cell-depleted or T-cell-replete grafts.
We performed 5′ single-cell RNA sequencing on samples collected ~1 year after allo-SCT. The cohort included six recipients, all of whom had experienced CMV reactivation: three who received an αβ T-cell–depleted graft and three who received a T-cell–replete graft. In addition, we analyzed paired donor samples for five of these transplant pairs (αβ T-cell–depleted n=3, T-cell–replete n=2), and we included longitudinal pre- and post-CMV reactivation samples from two recipients. Clonotypes were defined by CDR3 sequence identity.
Donor–recipient comparisons revealed minimal sharing of αβ TCR clonotypes, regardless of graft type, suggesting limited persistence of donor-derived αβ T cells. In contrast, Vδ2⁺ γδ T-cell clonotypes were frequently shared between donors and recipients, indicating selective persistence of this subset. Vδ2⁻ γδ clonotypes expanded post-CMV reactivation, but were typically absent in donor samples, suggesting de novo emergence in the recipient. ~1 year after allo-HSCT, CD8⁺ αβ and Vδ2⁻ γδ T cells exhibited cytotoxic effector phenotypes marked by distinct granzyme expression profiles. Transcriptional imprinting differed by graft type, with AREG enriched in Vδ2⁻ γδ T cells from T-cell–replete allo-HSCT recipients, and KLRC2/3 upregulated in CD8⁺ αβ T cells from αβ-depleted allo-HSCT recipients.
Our findings reveal distinct T-cell reconstitution patterns following allo-HSCT in patients with CMV reactivation, characterized by limited persistence of donor-derived αβ T-cell clones, selective retention of Vδ2⁺ γδ T-cell clonotypes, and expansion of de novo Vδ2- γδ T-cell clonotypes. These findings highlight the contribution of both γδ and αβ T-cell subsets to antiviral immunity after allo-HSCT, with γδ T cells potentially playing a compensatory role when αβ T-cell reconstitution is limited.