Graft γδ TCR Sequencing Identifies Public Clonotypes Associated with Hematopoietic Stem Cell Transplantation Efficacy in Acute Myeloid Leukemia Patients and Unravels Cytomegalovirus Impact on Repertoire Distribution

Abstract

Although the impact of donor graft composition on clinical outcomes after hematopoietic stem cell transplantation (HSCT) has been studied, little is known about the role of intragraft gd TCR repertoire on clinical outcomes following HSCT. Using a highthroughput sequencing platform, we sought to analyze the TCR g-chain (TRG) repertoire of gd T cells within donor stem cell grafts and address its potential impact on clinical response in the corresponding patients. A total of 20 peripheral blood stem cell grafts were analyzed, and donors were classified as CMV +/2 . The respective acute myeloid leukemia recipients were followed for disease relapse and acute graft-versus-host disease (aGvHD) development post-HSCT. In all samples, TRG repertoire showed a reduced diversity and displayed overrepresented clones. This was more prominent in grafts from CMV + donors, which presented a more private repertoire, lower diversity, skewed distribution, and reduced usage of the V9-JP pairing. Grafts given to nonrelapse patients presented a more public repertoire and increased presence of long sequence clonotypes. Variable-joining gene segment usage was not associated with aGvHD development, but a higher usage of V2-JP1 pairing and lower usage of V4-J2/V5-J2/V8-JP2 were observed in grafts given to nonrelapse patients. Our work identified five private overrepresented and one public CDR3 sequence (CATWDGPYYKKLF) associated with CMV infection, in addition to 12 highly frequent public sequences present exclusively in grafts given to nonrelapse patients. Our findings show that, despite CMV infection reshaping the TRG repertoire, TRG composition is not associated with aGvHD development, and several public sequences are associated with clinical remission.

Impact of γδ T cells on clinical outcome of hematopoietic stem cell transplantation: systematic review and meta-analysis

“…The studies included in the qualitative synthesis highlighted that the Vd1 subtype mediates the antiviral effect 31,32,38,48,51 and that distinct gd T-cell clones are important in control of viral infection (Table 1). 12,45 The OS and DFS follow-up period were not consistently reported among the studies, ranging from 2, 7 2.5, 54 3, 5,56 4, 53 and 5, 55 up to 7 years. 4 Only 1 study reported HR between high vs low gd T-cell groups 4 ; for all the others, we estimated the HR following standard guidelines.…”

“…Two qualitative studies also described that gd T-cell clonotypes were associated with less relapse after HSCT (Table 1). 45,47 Only 1 study assessed the gd T-cell graft composition and observed no effect on relapse incidence (RR, 0.99; 95% CI, 0.76-1.29; P 5 .95). 53 The pooled risk effect of both immune reconstitution and graft content further confirmed improved outcome for patients with high gd T cells (RR, 0.65; 95% CI, 0.42-1.29; P 5 .05), although there was evidence of subgroup heterogeneity (I 2 5 81.2%, P 5 .02).…”

“…Studies included on qualitative synthesis also indicated the lack of association between gd T cells and aGVHD development (Table 1). 30,35,36,40,41,43,45,46,48,49,52…”

The complex existence of γδ T cells following transplantation: the good, the bad and the simply confusing

“…There were no public or shared sequences specific to CMV, as individual patients had distinct clonal γδ TCR responses to CMV, although there was some homology . Another study also showed that the TRD repertoire had reduced diversity in patients with CMV, further demonstrating the remarkable impact CMV can exert on γδ T cells …”

“…59 Another study also showed that the TRD repertoire had reduced diversity in patients with CMV, further demonstrating the remarkable impact CMV can exert on cd T cells. 60…”