Extensive clonal expansion of T lymphocytes causes contracted diversity of complementarity-determining region 3 and skewed T cell receptor repertoires after allogeneic hematopoietic cell transplantation

Rapid reconstitution of CMV-specific T-cells after stem-cell transplantation

OBJECTIVE

As reconstitution of virus-specific T-cells is critical to control cytomegalovirus (CMV)-viremia following stem-cell transplantation (SCT), we characterized the dynamics in CMV-specific T-cell reconstitution after SCT.

METHODS

Cytomegalovirus-specific T-cells from 51 SCT-recipients were prospectively quantified and phenotypically characterised by intracellular cytokine-staining after specific stimulation and HLA class-I-specific pentamers using flow cytometry.

RESULTS

Cytomegalovirus-specific CD4 T-cells reconstituted after a median of 2.3 (IQR, 2.0-3.0) weeks following autografting, and 4.0 (IQR, 3.0-5.6) weeks after allografting, with CMV-specific T-cells originating from donors and/or recipients. The time for reconstitution of CMV-specific CD4 and CD8 T-cells did not differ (P = .58). Factors delaying the time to initial reconstitution of CMV-specific CD4 T-cells included a negative recipient serostatus (P = .016) and CMV-viremia (P = .026). Percentages of CMV-specific CD4 T-cells significantly increased over time and reached a plateau after 90 days (P = .043). Relative CMV-specific CD4 T-cell levels remained higher in long-term transplant recipients compared with those in controls (P < .0001). However, due to persisting lymphopenia, absolute numbers of CMV-specific T-cells were similar as in controls.

CONCLUSION

Cytomegalovirus-specific T-cells rapidly reconstitute after SCT and their percentages remain high in the long term. In the face of persistent lymphopenia, this results in similar absolute numbers of CMV-specific T-cells as in controls to ensure sufficient pathogen control.

TRBV kinetics and its association with HLA disparity and aGVHD following allogeneic hematopoietic stem cell transplantation

INTRODUCTION

The relative expression of T cell receptor (TCR) beta variable (TRBV) and TCR diversity was compared between recipients receiving human leukocyte antigen (HLA)-mismatched transplants and those receiving HLA-matched transplants, using granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood stem cells and bone marrow as grafts.

METHODS

The kinetics of the relative expression of TRBV family members were analyzed using real-time quantitative PCR. Additionally, the association of TRBV clonotype with acute graft-versus-host disease (aGVHD) was determined by cloning and sequence analysis of the CDR3 region.

RESULTS

The TCR diversity in recipients receiving HLA-mismatched transplants was significantly lower than in those receiving HLA-matched transplants at 1 month and 2 months after hematopoietic stem cell transplantation (HSCT) (both P < 0.05). However, these differences disappeared 3 months after transplantation. The relative expression of TRBV27 (n = 7 recipients) at the onset of aGVHD was higher than in corresponding donors (P = 0.025), but no significant differences were observed between recipients lacking aGVHD and their donors at serial time points after HSCT.

CONCLUSION

Our results suggest that HLA disparity may affect the relative expression of TRBV in the early phase after transplantation, and TRBV27 may be associated with the onset of aGVHD.

Patterns of T-cell reconstitution by assessment of T-cell receptor excision circle and T-cell receptor clonal repertoire after allogeneic hematopoietic stem cell transplantation in leukemia patients ? a study in Chinese patients

OBJECTIVE

Successful allogeneic hematopoietic stem cell transplantation (HSCT) requires reconstitution normal T-cell immunity. Measurement of T-cell receptor excision circles (TRECs) and T-cell receptor beta (TCRBV) CDR3 repertoire is a means of quantifying recent thymic T-cell production and reflecting antigen-specific T-cell clones proliferation.

METHODS

We used real-time quantitative PCR to detect TRECs from 43 Chinese patients who underwent three kind of allo-HSCT without T-cell depletion. RT-PCR was performed to amplify 24 subfamily genes of TCRBV in 24 patients of them.

RESULTS

For haploidentical-D group, the TRECs numbers were lower up to 24 months. For matched-sibling donor (MSD) group, the recovery of TRECs was faster than those of other two groups. TRECs values in matched-unrelated donor (MUD) were in the middle. During 2-19 months after transplantation, there were 6-16 BV subfamilies expressed and 33-48% of them were polyclones. The usage rate of TCRBV and percentage of polyclones in haploidentical-D were less than those of other two groups. Twenty-three CDR3 molecules were obtained from nine patients who were potentially associated with GVHD or CMV infection.

CONCLUSIONS

Analyzing the changes of TCRBV repertoire and measuring TRECs during immune reconstitution would be useful to determine the host's current immune status and ability of T-cell immune reconstitution and also to find antigen-specific T-cell clones in the three kinds of HSCT.

Skewed T cell receptor repertoire of Vdelta1(+) gammadelta T lymphocytes after human allogeneic haematopoietic stem cell transplantation and the potential role for Epstein-Barr virus-infected B cells in clonal restriction

The proliferation of Vdelta1(+) gammadelta T lymphocytes has been described in various infections including human immunodeficiency virus (HIV), cytomegalovirus (CMV) and malaria. However, the antigen specificity and functions of the human Vdelta1(+) T cells remain obscure. We sought to explore the biological role for this T cell subset by investigating the reconstitution of T cell receptor (TCR) repertoires of Vdelta1(+) gammadelta T lymphocytes after human allogeneic haematopoietic stem cell transplantation (HSCT). We observed skewed TCR repertoires of the Vdelta1(+) T cells in 27 of 44 post-transplant patients. Only one patient developed EBV-associated post-transplant lymphoproliferative disorder in the present patient cohort. The -WGI- amino acid motif was observed in CDR3 of clonally expanded Vdelta1(+) T cells in half the patients. A skew was also detected in certain healthy donors, and the Vdelta1(+) T cell clone derived from the donor mature T cell pool persisted in the recipient's blood even 10 years after transplant. This T cell clone expanded in vitro against stimulation with autologous EBV-lymphoblastoid cell lines (LCL), and the Vdelta1(+) T cell line expanded in vitro from the same patient showed cytotoxicity against autologous EBV-LCL. EBV-infected cells could also induce in vitro oligoclonal expansions of autologous Vdelta1(+) T cells from healthy EBV-seropositive individuals. These results suggest that human Vdelta1(+) T cells have a TCR repertoire against EBV-infected B cells and may play a role in protecting recipients of allogeneic HSCT from EBV-associated disease.

Longitudinal analysis of T-cell receptor variable beta chain repertoire in patients with acute graft-versus-host disease after allogeneic stem cell transplantation

T-cell receptor variable beta chain (TCRBV) repertoire spectratyping involves the estimation of CDR3 length distributions for monitoring T-cell receptor diversity and has proven useful for analyses of immune reconstitution and T-cell clonal expansions in graft-versus-host disease (GVHD) and graft-versus-leukemia after allogeneic stem cell transplantation. We performed a longitudinal spectratype analysis of 23 TCRBV families in 28 patients who underwent allogeneic T cell-depleted peripheral blood stem cell transplantation. Sixteen patients subsequently developed acute GVHD. We recently developed statistical methods that bring increased power and flexibility to spectratype analysis and allow us to analyze TCRBV repertoire development under appropriately complex statistical models. Applying these methods, we found that patients with acute GVHD demonstrated TCRBV repertoire development statistically distinct from that repertoire development in patients without GVHD. Specifically, GVHD patients showed spectratypes indicative of lower diversity and greater deviation from the spectratypes expected in healthy individuals at intermediate times. Most individual TCRBV subfamilies had spectratypes statistically distinguishable between GVHD and non-GVHD patients at 6 months after transplantation. These results suggest that the T-cell receptor repertoire perturbations associated with acute GVHD are widely spread throughout the TCRBV families.

Allogeneic hematopoietic stem cell transplantation: state of the art and new perspectives

Allogeneic hematopoietic stem cell transplantation (ASCT) is a well-established therapy for leukemias and other immunohematopoietic disorders. In more recent years, bone marrow as stem cell source has been replaced by peripheral blood stem cells, which results in faster engraftment. Cord blood grafts are increasingly used. Conditioning prior to transplant may be myeloablative or nonmyeloablative. The latter is used preferentially in patients with high age or organ impairment. Isolation in the hospital during posttransplant pancytopenia has been challenged by promising results using home care. PCR diagnosis and new antifungal and antiviral treatment have reduced morbidity and mortality. The major threat to a successful outcome after ASCT is leukemic relapse. PCR techniques to detect recipient cells in the leukemic cell lineage or minimal residual disease enable early detection of leukemic cells. Donor lymphocyte infusions have an antileukemic effect. ASCT has shown an antitumor effect in metastatic cancers from breast, kidney, colon, ovaries, prostate and pancreas. Mesenchymal stem cells may be derived from bone marrow and have the capacity to differentiate into several mesenchymal tissues, such as bone, cartilage and fat. They seem to escape the immune system and have immunomodulatory effects in vitro and in vivo. To conclude, ASCT is a potent immunotherapy.

An improved methodology to detect human T cell receptor beta variable family gene expression patterns

Comprehensive gene expression analysis of the T cell receptor repertoire of an individual can be very useful in evaluating the immune response in a variety of conditions. Antibody-based analysis methods can detect approximately 60% of the human T cell receptor beta variable (TCRBV) proteins, while gene expression analysis, primarily through employment of the polymerase chain reaction (PCR), has had somewhat greater success in the detection of additional TCRBV families. Many of these previous PCR methods, however, have been unable to detect all 91 alleles of the human TCRBV genes. This is primarily due to either deficiencies in the amplification of all of the variable beta families, subfamilies, and alleles, or the prior lack of a systematic classification of the TCR variable family gene segment sequences. We describe here a real-time reverse transcription polymerase chain reaction-based method, which allows efficient automation and integration of amplification, detection, and analysis with sequence-specific detection of all T cell receptor beta variable gene families, subfamilies, and alleles. This method, which in itself contributes significant improvements over existing technologies through its comprehensiveness and efficiency, also functions independently of variables such as sample source and sample processing and has the ability to run on multiple real-time PCR platforms, affording one the implementation of personal preferences.

Clonality analysis of T cells mediating acute and chronic rejection in kidney allografts

The clonality of T-cell populations mediating acute and chronic rejection (AR and CR, respectively) of kidney allografts was ascertained by investigating the diversity of TCRBV genes expressed by allograft-infiltrating T cells. Both oligoclonality and polyclonality cases were found in biopsy specimens of AR as well as CR. These results indicated that the T-cell clonality in each specimen did not correlate directly with the mode of rejection. When AR and CR specimens were compared, however, the CR specimen group was significantly more polyclonal (or less oligoclonal) than the AR group. This result may reflect the higher chance of epitope spreading in the more slowly progressing CR than in AR.

Immune reconstitution following stem cell transplantation

The period of immune deficiency following stem cell transplantation (SCT) results in significant morbidity and mortality. Whilst supportive therapies have partially improved the outcome of infective episodes, disease relapse remains a considerable obstacle to improvement in overall outcomes. An increased understanding of the importance of the immune system in preventing relapse has derived from studies in the allogeneic setting. Increasing awareness of autologous anti-tumor responses has also focused interest on enhancing such activity. Successful application of some of these newer therapies, such as tumor vaccination approaches, may depend critically on reconstitution of functional immune reactivity. Whilst early recovery of innate immunity (myeloid series and natural killer (NK) cells) results in reconstitution of protective immunity against many bacterial pathogens, both the absolute levels and function of T and B lymphocytes remain abnormal for many months or years. Incorporation of T-cell depletion, choice of graft type (both donor and source), development of graft-vs.-host disease and level of residual thymic activity can all influence aspects of the reconstitution process. Advances in immunological monitoring are providing new insights, particularly into the recovery of specific T-cell subsets. This review focuses mainly on recent advances in the understanding of immune reconstitution in the allogeneic setting.

Molecular TCR diagnostics can be used to identify shared clonotypes after allogeneic hematopoietic stem cell transplantation

OBJECTIVE

In allogeneic hematopoietic stem cell (HSCT) transplantation, recovery of the T cell receptor (TCR) repertoire depends upon the composition of the graft and is modulated by peri-transplant immunosuppression, viral infections, and graft-vs-host disease (GVHD). We hypothesized that after allogeneic HSCT, molecular analysis of the TCR repertoire can be used to identify and quantitate immunodominant T cell clones that may play a role in GVHD or other clinical events.

METHODS

We utilized a rational strategy for the analysis of the expanded CTL clones. First, we studied the VB spectrum in a cohort of patients who had received either matched sibling or unrelated donor grafts. The CDR3 sequences of immunodominant clones were identified and clonotypic PCR and sequencing was applied to determine the level of clonotype sharing.

RESULTS

Significant expansions of VB families were observed following transplantations; 61% were oligo/monoclonal. Immunodeficiency was reflected by depletion of multiple VB families from both the CD8 and CD4 repertoires. The level of sharing varied between clonotypes, suggesting that some antigens have a more "public" spectrum while others are restricted to specific patients. Immunodominant CDR3 sequences common to allogeneic HSCT, healthy controls, and other conditions were identified.

CONCLUSION

The clonotypes of expanded CTL clones may reflect responses to alloantigens (e.g., in correlation with clinical GVHD) or pathogens. In the future, molecular T cell diagnostics may become a powerful clinical tool in transplantation to monitor disease and to direct treatment.

The presence and longevity of peripherally expanded donor-derived TCRalphabeta+ mature T lymphocyte clones after allogeneic bone marrow transplantation for adult myeloid leukemias

There are two major pathways for T-cell regeneration after allogeneic bone marrow transplantation; thymus-dependent T-cell differentiation of T-cell progenitors, and peripheral expansion of mature T cells in the graft. In order to learn to what extent the peripheral expansion of donor-derived mature T lymphocytes contributes to reconstitution of the TCRalphabeta+ T-cell repertoire after allogeneic bone marrow transplantation for adult myeloid leukemias, we pursued the fate of donor-derived T-cell clones using the amino-acid sequences of the complementarity-determining region 3 (CDR3) of the TCR-beta chain as a clonal marker. Clonal expansion of TCRalphabeta+ T lymphocytes with specific TCRBV subfamilies was identified in donor blood. Identical T-cell clones were not found in blood from recipients before transplantation. The donor-derived T-cell clones were identified in the circulating blood from recipients a few months after allogeneic bone marrow transplantation, and they remained in the blood for 18 months after transplant in two recipients, and for 56 months in one. These results suggest that the peripheral expansion of mature T lymphocytes in the graft makes a significant contribution to post-transplant T-cell regeneration during the early period of transplantation in humans, and that mature T cells can survive in recipients for several years. Further investigation will be required to explore which antigens drive the expansion of T-cell clones in donors and recipients, and the mechanisms of maintaining homeostatic balance between the thymus-dependent pathway and the peripheral expansion of mature T cells in post-transplant T-cell regeneration.

Distinct TCRAV and TCRBV repertoire and CDR3 sequence of T lymphocytes clonally expanded in blood and GVHD lesions after human allogeneic bone marrow transplantation

Acute graft-versus-host disease (GVHD) is a disorder involving the skin, gut and liver that is caused by mismatches of major and/or minor histocompatibility antigens between the HLA-identical donor and recipient. If T lymphocytes infiltrating GVHD lesions recognize antigens expressed in these organs, T cell clones should expand in inflammatory tissues. We previously reported that recipients of allogeneic bone marrow grafts have clonally expanded TCRalphabeta(+) T lymphocytes soon after transplantation, which leads to a skew of TCR repertoires. To establish whether or not the same antigens cause clonal expansion of T lymphocytes in both blood and GVHD tissues, we examined the usage of TCR alpha and beta chain variable regions (TCRAV and TCRBV) and determined the complementarity-determining region 3 (CDR3) of T lymphocytes clonally expanded in circulating blood and GVHD lesions. We found that the repertoires and CDR3 diversity of TCRAV and TCRBV differed between the GVHD lesions and circulating blood, suggesting the selective recruitment of antigen-specific T cells into GVHD tissues. We also found that the usage of TCRAV and TCRBV by the clonally expanded T lymphocytes and their CDR3 sequences differed between the GVHD tissues and blood. These results suggest that the antigen specificity of TCRalphabeta(+) T lymphocytes clonally expanded in blood and GVHD lesions is different.