T cell receptor alpha repertoire of CD8+ T cells following allogeneic stem cell transplantation using next-generation sequencing.

Alloreactivity or opportunistic infections following allogeneic stem cell transplantation are difficult to predict and contribute to post-transplantation mortality. How these immune reactions result in changes to the T cell receptor repertoire remains largely unknown. Using next generation sequencing, the T cell receptor alpha repertoire of naive and memory CD8+ T cells from 25 patients who had received different forms of allogeneic transplantation was analysed. In parallel, reconstitution of the CD8+/CD4+ T cell subsets was mapped using flow cytometry. When comparing the influence of anti-T cell therapy, a delay in the reconstitution of the naive CD8+ T cell repertoire was observed in patients who received in vivo T cell depletion using antithymocyte globulin or post-transplantation cyclophosphamide in case of haploidentical transplantation. Sequencing of the T cell receptor alpha identified a repertoire consisting of more dominant clonotypes (>1% of reads) in these patients at 6 and 18 months post-transplantation. When comparing donor and recipient, ~50% and ~80% of the donors' memory repertoire were later retrieved in the naive and memory CD8+ T cell receptor repertoire of the recipients, respectively. Although there was a remarkable expansion of single clones observed in the recipients' memory CD8+ T cell receptor alpha repertoire, no clear association between graft-versus-host disease or cytomegalovirus infection and T cell receptor diversity was identified. A lower T cell receptor alpha diversity was observed in recipients of a cytomegalovirus-seropositive donor (p=0.014). These findings suggest that CD8+ T cell reconstitution in transplanted patients is influenced by the use of T cell depletion or immunosuppression and the donor repertoire.