RESUMEN
Autologous hematopoietic stem cell transplantation (HSCT), a safer type of HSCT than allogeneic HSCT, is a promising therapy for patients with severe autoimmune diseases (ADs). Despite the long history of medical practice, structural changes in the adaptive immune system as a result of autologous HSCT in patients with various types of ADs remain poorly understood. In this study, we used high-throughput sequencing to investigate the structural changes in the peripheral blood T-cell repertoire in adult patients with ankylosing spondylitis (AS) during two years after autologous HSCT. The implementation of unique molecular identifiers allowed us to substantially reduce the impact of the biases occurring during the preparation of libraries, to carry out a comparative analysis of the various properties of the T-cell repertoire between different time points, and to track the dynamics of both distinct T-cell clonotypes and T-cell subpopulations. In the first year of the reconstitution, clonal diversity of the T-cell repertoire remained lower than the initial one in both patients. During the second year after HSCT, clonal diversity continued to increase and reached a normal value in one of the patients. The increase in the diversity was associated with the emergence of a large number of low-frequency clonotypes, which were not identified before HSCT. Efficiency of clonotypes detection after HSCT was dependent on their abundance in the initial repertoire. Almost all of the 100 most abundant clonotypes observed before HSCT were detected 2 years after transplantation and remained highly abundant irrespective of their CD4+ or CD8+ phenotype. A total of up to 25% of peripheral blood T cells 2 years after HSCT were represented by clonotypes from the initial repertoire.
RESUMEN
αßT-cell-depleted allogeneic hematopoietic cell transplantation holds promise for the safe and accessible therapy of both malignant and non-malignant blood disorders. Here we employed molecular barcoding normalized T-cell receptor (TCR) profiling to quantitatively track T-cell immune reconstitution after TCRαß-/CD19-depleted transplantation in children. We demonstrate that seemingly early reconstitution of αßT-cell counts 2 months after transplantation is based on only several hundred rapidly expanded clones originating from non-depleted graft cells. In further months, frequency of these hyperexpanded clones declines, and after 1 year the observed T-cell counts and TCRß diversity are mostly provided by the newly produced T cells. We also demonstrate that high TCRß diversity at day 60 observed for some of the patients is determined by recipient T cells and intrathymic progenitors that survived conditioning regimen. Our results indicate that further efforts on optimization of TCRαß-/CD19-depleted transplantation protocols should be directed toward providing more efficient T-cell defense in the first months after transplantation.