CMV reactivation drives post-transplant T cell reconstitution and results in defects in the underlying TCRβ repertoire

immuneACCESS ◽  
2018 ◽  
Author(s):  
Y Suessmuth ◽  
R Mukherjee ◽  
B Watkins ◽  
DT Koura ◽  
K Finstermeier ◽  
...  
2012 ◽  
Vol 18 (2) ◽  
pp. S224
Author(s):  
U.E. Burkhardt ◽  
C. Desmarais ◽  
H.S. Robins ◽  
D. Wu ◽  
J. Wong ◽  
...  

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 4066-4066
Author(s):  
Brett Glotzbecker ◽  
Heidi Mills ◽  
Jacalyn Rosenblatt ◽  
Robin Joyce ◽  
James Levine ◽  
...  

Abstract Abstract 4066 The fundamental challenge in designing an effective conditioning regimen for allogeneic transplantation involves the prevention of disease relapse while minimizing the risk for Graft versus Host Disease (GVHD). Treatment with total lymphocyte irradiation (TLI) and anti-thymocyte globulin (ATG) has been shown to minimize the risk of GVHD through the biasing of the T cell reconstitution towards an inhibitory phenotype. However, disease relapse remains a significant concern. Clofarabine is a second generation nucleoside analog with potent cytoreductive capacity and demonstrates efficacy in hematological malignancies. In this study, we examined the combination of clofarabine, TLI and ATG with respect to T cell reconstitution, risk for GVHD and transplant outcome. Sequential cohorts of 5 patients were treated with TLI and ATG alone or in conjunction with 20 mg/m2, 30 mg/m2 or 40 mg/m2 of clofarabine for 5 days. Cyclosporine and mycophenolate mofetil were administered as GVHD prophylaxis. Twenty patients have been enrolled (5 AML/MDS, 2 ALL, 6 lymphoma, 2 CLL, 5 myeloma) and received HLA matched peripheral blood stem cells collected from related (N=11) and unrelated donors (N=9). Of 19 evaluable patients, 15 are alive with a median follow up of 665 days. Day 30 and 100 mortality was 0% for TLI and ATG and 0% and 10% for those receiving clofarabine. The maximum tolerated dose (MTD) of clofarabine was 30 mg/m2 as 2 patients experienced treatment related mortality at the 40 mg/m2 dose level. Grade 5 infections and multiorgan failure occurred in both patients. All patients demonstrated engraftment with mean bone marrow donor chimerism of 92.5% at Day 30. The first cohort's ANC did not drop below 500 cells/uL, while median time to neutrophil engraftment in the patients who received clofarabine was 9 days. The median time to platelet recovery was 11 and 12 days for patients receiving TLI and ATG alone or with clofarabine, respectively (p=0.39). T cell reconstitution studies demonstrated a significant decrease in CD4+ cells to (<200 cells/uL) persisting for more than 6 months and a more than a two fold increase in circulating CD56+ NK cells. No significant decrease in CD8 T cells in the early post-transplant period was seen in either group. The mean percentage of regulatory T cells (CD4+/25+/FoxP3+) rose in the early post-transplant period following TLI and ATG (5.5 to 14.2% from baseline to day 30; p=0.015), but not in those receiving clofarabine (8.1 to 6%; p=0.15). Assessment of T cell polarization at these time points demonstrated a two fold increase in CD8+ T cells expressing IL-4 at Day 30 in patients receiving TLI and ATG alone (p=0.04); but not following clofarabine containing conditioning. Consistent with these findings, the incidence of grade II-IV GVHD was 0% and 42% in those receiving TLI and ATG alone or in conjunction with clofarabine, respectively. cGVHD was seen in 20% and 42% of patients, respectively. In contrast, disease progression was seen in 60% of patients receiving TLI and ATG alone as compared to 27% receiving clofarabine, TLI, and ATG. In summary, the addition of clofarabine to TLI and ATG conditioning resulted in a decrease in circulating regulatory T cells, decreased CD8+ T cell expression of IL-4, and was associated with an increased risk of GVHD and a potential for a decrease in the risk of relapse. Disclosures: Chen: Genzyme: Membership on an entity's Board of Directors or advisory committees. Avigan:Genzyme: Research Funding.


Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 3905-3905
Author(s):  
Sakura Hosoba ◽  
Christopher R. Flowers ◽  
Catherine J Wu ◽  
Jens R. Wrammert ◽  
Edmund K. Waller

Abstract Introduction: Rituximab (R) administration results in depletion of blood B cells and suppression of B cell reconstitution for several months after, with suggestions that T cell reconstitution may also be impaired. We hypothesized that pre-transplant R would be associated with delayed B and T cell reconstitution after allo-HSCT compared with non-R-treated allo-HSCT recipients. Methods: We conducted a retrospective analysis of 360 patients who underwent allo-HSCT using BM or G-CSF mobilized PB. Recipients of cord blood, T cell depleted grafts and 2nd allo-HSCT were excluded. Analysis of lymphocyte subsets in at least one blood at 1, 3, 6, 12, and 24 months post-allo-HSCT was available for 255 eligible patients. Data on lymphocyte recovery was censored after DLI or post-transplant R therapy. Post-HSCT lymphocyte recovery in 217 patients who never received R (no-R) was compared to 38 patients who had received R before allo-HSCT (+R) including 12 CLL, 19 NHL, and 7 B-cell ALL patients. +R patients received a median of 9 doses of R with the last dose of R at a median of 45 days pre-transplant. Results: Mean lymphocyte numbers in the blood at 1, 3, 6, 12, and 24 months were B-cells: 55 ± 465/µL, 82 ± 159/µL, 150 ± 243/µL, 255 ± 345/µL, and 384 ± 369/µL (normal range 79-835); and T-cells: 65 ± 987/µL, 831 ± 667/µL, 1058 ± 788/µL, 1291 ± 985/µL, and 1477 ± 1222/µL (normal range 675-3085). Lymphocyte reconstitution kinetics did not vary significantly based upon the intensity of the conditioning regimen or related vs. unrelated donors allowing aggregation of patients in the +R and no-R groups (Figure). B cell reconstitution in the +R patients was higher at 1 month post-allo-HSCT (relative value of 143% p=0.008) and lower at 3 months post-transplant (19.2%, p=0.069) compared to no-R patients. Blood B cells in the +R group rebounded by the 6th month post-allo-HSCT and remained higher than the no-R group through the 24th month post-HSCT (197% at the 6th month, p=0.037). Higher levels of B-cells at 1 month in the +R group was due to higher blood B-cells at 1 month post-HSCT among 12 CLL patients compared with no-R patients (423%, p<0.001; Figure), while B-cell counts in the remaining +R patients (B-cell NHL and B-cell ALL) were lower than the no-R patients at both 1 and 3 months. Reconstitution of CD4+ and CD8+ T cells among +R patients were similar to no-R patients in the first month post-allo-HSCT and then rebounded to higher levels than the no-R group of patients (relative value 194%, p=0.077 at the 24th month for CD4+ T cell subset, and 224%, p=0.020 for CD8+ T cell subset; Figure). CLL patients had a striking increase in blood levels of donor-derived CD4+ and CD8+ T cells at 3 months post-transplant concomitant with the disappearance of blood B cells compared with no-R patients (relative value of 178% and 372%, p=0.018 and p=0.003, respectively; Figure). Long term T cell reconstitution remained higher for +R patients compared with no-R patients, even when CLL patients were excluded (relative value of 203%, p=0.005 at 24 months post-HSCT; Figure). Conclusions: We observed higher levels of blood B cells and T cells ³ 6 months post-allo-HSCT in +R patients compared with no-R patients. B cell recovery at 6 months post-transplant is consistent with clearance of residual plasma R given the 1-2 months half-life of R, and the median of 1.5 months between the last dose of R and allo-HSCT. The increased blood CD8+ T cells in the blood of CLL patients at 3 months post-allo-HSCT associated with clearance of the B-cells seen 1 month post-HSCT is consistent with a donor T cell-mediated GVL effect. Pre-transplant R therapy does not appear to have any long-term deleterious effect on immune reconstitution, indicating that post-allo-HSCT vaccination at ≥6 months may be efficacious. Figure: Kinetics of lymphocyte reconstitution after allo-HSCT varied by history of pre-transplant R administration and primary disease. Panels show mean counts of each lymphocyte subset at 1, 3, 6, 12 and 24 months post-allo-HSCT for: (1) B cell, (2) T cell, (3) CD4+ and (4) CD8+ T cells. Solid lines with triangle show no-R group; dashed lines with circles shows subgroups of CLL and NHL/ALL +R patients. Asterisks show p values from t-test of the comparison between CLL +R or the NHL/ALL +R patients with no-R patients. *p<0.05; ** p<0.01; *** p<0.001. Figure:. Kinetics of lymphocyte reconstitution after allo-HSCT varied by history of pre-transplant R administration and primary disease. Panels show mean counts of each lymphocyte subset at 1, 3, 6, 12 and 24 months post-allo-HSCT for: (1) B cell, (2) T cell, (3) CD4+ and (4) CD8+ T cells. Solid lines with triangle show no-R group; dashed lines with circles shows subgroups of CLL and NHL/ALL +R patients. Asterisks show p values from t-test of the comparison between CLL +R or the NHL/ALL +R patients with no-R patients. *p<0.05; ** p<0.01; *** p<0.001. Disclosures No relevant conflicts of interest to declare.


Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 5462-5462
Author(s):  
Ayman Saad ◽  
Samantha B Langford ◽  
Shin Mineishi ◽  
Lawrence S. Lamb

Abstract Background: Post-transplant cyclophosphamide (PTCy) is increasingly used for GVHD prophylaxis after allogeneic hematopoietic stem cell transplantation (HCT) using alternative donors. However, immune reconstitution can be delayed posing an increased risk for CMV reactivation. We evaluated the outcomes of patients who received HCT-apheresis products comparing the impact of PTCy on lymphocyte recovery, CMV reactivation and CMV-specific CD8+ T cell recovery following haplo-identical (HAPLO), matched unrelated donor (MUD), and mismatched unrelated donor (mMUD) grafts vs. with conventional matched related donor (MRD) graft recipients. Methods: We examined 26 patients (median age, 49 years; range, 20-72 years) with advanced hematologic malignancies; n=5 (HAPLO); 6 (MRD); 15 (MUD). All patients received myeloablative conditioning regimens that was either busulfan- or total body irradiation (TBI)-based. PTCy (50 mg/kg/day) was administered on days +3 and +4 following HAPLO and on day +3 following MUD/mMUD transplant. Peripheral blood lymphocyte reconstitution and frequency of circulating CMV-directed CD8+ T cells was assessed (day ± 10 days) on post-transplant days +30, +60, and +90. Circulating anti-CMV T cell frequency was assessed using a phycoerythrin-tagged MHC dextramer against HLA-specific CMV pp65, IE-1, or pp50 peptides (Immudex; Copenhagen, DK) in combination with Tru-Count¨ tubes and fluorescent-labeled monoclonal antibodies against CD3, CD8, CD4, CD16/56, and CD19 (BD Biosciences; San Jose, CA). Anti-CMV CD8+ T cell immunity was defined as a CMV-dextramer (CMV/DEX) positive count of ≥7cells/ml. CMV reactivation was defined as a serologic titer of >500IU/mL. All patients with CMV reactivation received ganciclovir therapy until CMV titer became negative. Results: Day +30 total T cell recovery was significantly faster in MRD than CY-treated recipients (p=0.015) due principally to more robust CD8+ T cell recovery. CD4 T cell recovery remained below normal range in all groups through day +100. NK cells recovered to normal numbers at day +28 in all groups. Neither PTCy nor donor source significantly impacted the percentage of patients that recovered anti-CMV CD8+ T cells at each time interval (p = 0.8232). Excluding donors (D) and recipients (R) that were both negative, CMV/DEX+ T cells recovery was >7/mL in 4/5 MRD, 7/14 MUD, and 3/5 HAPLO by day +100. Among MRD recipients either D+ or R+ (n=5), 2 patients showed CMV reactivation within 40 days of transplant that was associated with <7 CMV/DEX+ T cells on day +30. Subsequent high (>90/mL) CMV/DEX T cell response in one patient shortened the duration of viremia to 10 days (vs. 16 days with poor responder) and 3 patients showed no CMV reactivation and a high CMV/DEX+ T cell response by day +60. For MUD CMV D+ and/or R+ recipients (n=14), 3 showed CMV reactivation within 50 days of transplant. All 3 patients had suboptimal CMV/DEX T cell response on day +30. Robust CMV/DEX+ T cell response on day +60 predicted shorter duration of viremia (20 days vs. average of 32 days). For HAPLO CMV D+ and/or R+ (n=5) recipients, 4 experienced CMV reactivation within 50 days of transplant. All patients had a <7 CMV/DEX+ T cells/mL +30. Robust CMV/DEX+ T cell response by day +60 was associated with shorter duration of viremia (range 7-21 days), while one patient with <7/mL CMV/DEX+ T cells had continued CMV viremia for 36 days. Conclusion: In this preliminary analysis, neither PTCy nor donor source significantly impacted the percentage of patients that recovered anti-CMV CD8+ T cells at each time interval. A weak CMV/DEX+ response (<7 cells/mL) on day +30 was consistent with increased risk of CMV reactivation (viremia) in all groups. A CMV/DEX+ T cell count ≥7 cells/mL was not immediately protective against CMV reactivation, but higher counts were associated with a shortened duration of viremia while on antiviral therapy. Conversely, subnormal counts were associated with a longer duration of viremia. This interim analysis suggests that CMV/DEX+ T cell enumeration is a useful biologic correlate for determining clinical response to antiviral therapy, and that donor-derived CMV specific T cell immunity is not further compromised with following PTCy in alternative donor HCT. Disclosures No relevant conflicts of interest to declare.


2021 ◽  
Vol 11 ◽  
Author(s):  
Toshiki Terao ◽  
Ken-ichi Matsuoka ◽  
Kentaro Narita ◽  
Takafumi Tsushima ◽  
Satoshi Yuyama ◽  
...  

The prevention of chronic graft-versus-host disease (cGVHD) is important for recipients of hematopoietic stem-cell transplantation (HSCT). As one of the etiologies, the relationship between early T-cell recovery and subsequent cGVHD development has been the focus of attention. Recently, letermovir (LTV) was approved for preventing cytomegalovirus (CMV) reactivation in the early transplantation phase. Although CMV affects the immune reconstitution after HSCT, the impacts of LTV to prevent CMV reactivation on early T-cell recovery and cGVHD have not been fully investigated. We aimed to identify early T-cell recovery under LTV at day 30 in 15 and 33 recipients from matched related donors (MRDs) and haploidentical donors with post-transplant cyclophosphamide (PTCy-haplo), respectively. Early increases in the levels of total lymphocytes and HLA-DR+ activated T-cells at day 30 were observed under CMV prophylaxis by LTV only in PTCy-haplo recipients and not in MRD recipients. Moreover, PTCy-haplo recipients with LTV showed a significantly higher incidence of cGVHD, but not acute GVHD. Our observations suggest that an early increase in the levels of HLA-DR+ activated T-cells may be implicated in the development of cGVHD in patients treated with PTCy who received LTV. Further studies are warranted to validate our results and elucidate the detailed mechanisms of our new insights.


Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 4536-4536
Author(s):  
Maddalena Noviello ◽  
Elena Tassi ◽  
Pantaleo De Simone ◽  
Francesca Serio ◽  
Maria Teresa Lupo Stanghellini ◽  
...  

Introduction: Cytomegalovirus (CMV) reactivation and disease are important risk factors after allogeneic hematopoietic stem cell transplantation (allo-HSCT), and strongly affect morbidity and mortality after transplant. CMV-specific T cell reconstitution controls CMV reactivation and protects against serious adverse events but a protective level of CMV-specific T cell response or standardized method for its monitoring have not been yet determined. Methods: We designed a prospective, single-center observational study to assess if the kinetic and quality of CMV specific T-cell reconstitution impact the incidence and severity of CMV reactivations. We have enrolled 84 consecutive patients affected by hematological malignancies receiving allo-HSCT followed by Cyclophosphamide and Rapamycin between December 2017 and February 2019. Here we report preliminary data on the first 61 patients. Patients received allo-HSCT from family (siblings=10; HLA haploidentical=24), unrelated HLA-matched (n= 24) donors or cord blood (CB, n=3). The CMV serostatus of host (H) and donor (D) pairs was: H+/D+(n=40, 65%), H+/D-(n=20, 33%) and H-/D+ (n=1, 2%); H-/D-(7% of the overall transplanted population at our center) were excluded. CMV DNAemia was assessed weekly in whole blood (WB). Absolute numbers of polyclonal and CMV-specific T cells were quantified by flow cytometry using Troucount™Tubes (BD) and Dextramer®CMV-Kit (Immudex), respectively, in the graft and fresh WB at days -7, +30, +45, +60, +90, +120, +150, +180 and +360. Dextramer CMV kit includes reagents for the identification of CMV-specific lymphocytes restricted for several HLA class I molecules: A*01:01/*02:01/*03:01/*24:02 and B*07:02/*08:01/*35:01. These alleles allowed the longitudinal evaluation of 54 out of 61 (89%) patients. Results: At a median follow-up of 226 days post-HSCT, 31 (57%) patients experienced a CMV-related clinically relevant event (CRE, median +63 days), including 8 patients (15%) with CMV disease (median +59 days). Univariate analyses showed that the incidence of CMV clinically-relevant reactivation (CRE) was influenced by H/D CMV serostatus (0.90 in H+/D- versus 0.44 in H+/D+pairs, p=0.015) and by previous acute Graft-versus-Host Disease (aGvHD) requiring systemic immunosuppression (0.82 in aGvHD grade II-IV versus 0.52 in aGvHD grade 0-I, p=0.051). The disease status at transplant, the donor type (HLA-matched versus HLA-haploidentical/CB donors), donor's or host's age did not significantly affect the probability to develop CRE. For each time-point, we compared the absolute number of CMV-specific lymphocytes in patients experiencing or not a subsequent CRE. Our data demonstrate that higher levels of CMV-specific CD8+T cells in the donor apheresis and at +45 days after allo-HSCT are associated with reduced risk of subsequent CRE (median CMV-specific CD8+cells/kg in the apheresis=5x103in CRE-positive patients (CRE+) and 5x105in CRE-negative patients (CRE-), p=0.012; median CMV-specific CD8+at +45 days=0.14 cells/μL in CRE+and 1.21 cells/μL in CRE-, p=0.034). Furthermore, patients with any Dextramer positivity at +45 days displayed a lower incidence of CRE compared with subjects who were negative (CRE probability: 0.5 vs 1.0, p=0.003). Conversely, the absolute number of neither polyclonal CD3+CD8+T lymphocytes nor total CD3+T cells correlate with subsequent CRE. Taking advantage of the HLA mismatched-HSCT setting, we then dissected CMV-specific T-cell response according to HLA restriction elements (H/D=shared n=45, D-restricted n=14, H-restricted n=11). In H+/D+pairs, we observed a fast and similar kinetic of reconstitution of CMV-specific lymphocytes restricted by H/D and D HLAs. Conversely, in H+/D-pairs, we detected only CMV-specific CD8+lymphocytes restricted for H/D haplotypes. Host-restricted cells remained undetectable for the first 180 days after HSCT. Conclusion: Early after allo-HSCT and in the donor apheresis, the level of CMV-specific CD8+T cells measured by Dextramer staining differs in patients experiencing or not subsequent CRE. Furthermore, our findings indicate that CMV reactivations can prime H/D-restricted T cells presumably educated in the donor thymus; conversely, D- and H-restricted donor-derived lymphocytes have not yet undergone neither cross-priming nor thymic education respectively. Disclosures Brix: Immudex: Employment. Bonini:Kite/Gilead: Consultancy; Intellia Therapeutics: Consultancy; Intellia Therapeutics: Research Funding; Novartis: Consultancy; GSK: Consultancy; Allogene: Consultancy; Molmed: Consultancy; TxCell: Consultancy; -: Patents & Royalties: Adoptive T cell therapy field.


Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 2859-2859
Author(s):  
Lip Leong Chong ◽  
Chelsea Chia ◽  
Yin Teng Koh ◽  
Yang Liang Boo ◽  
Chun Tsu Lee ◽  
...  

Abstract Background: Cytomegalovirus (CMV) is a common cause of morbidity and mortality after allogeneic hematopoietic cell transplantation (HCT) despite major advances in diagnostic techniques and antiviral prophylactic strategies. The relative impacts of donor/recipient CMV serologic status, disease-specific and transplant-related prognostic factors on the risk of CMV reactivation and survival are undefined. Methods: We studied the outcome of 199 patients (median age, 46 years; range 17-71 years) receiving allogeneic HCT at National University Cancer Institute of Singapore (NCIS) between January 2016 and December 2020. Their hematologic diseases included AML (n=92), ALL (n=46), MDS (n=19), lymphomas (n=19), MPN (n=7) and others (n=16) such as refractory myelomas and aplastic anemias. The conditioning regimens used were either myeloablative (n=80) or reduced intensity conditioning (n=119) prior to an allograft from different donor sources. T-cell depletion (TCD) was used for GVHD prophylaxis in 124 patients; and this included post-transplant cyclophosphamide (PTCy, n=31), ex-vivo T-cell receptor alpha-beta / CD45RA depletion (TCRab/CD45RA) (ex-vivo TCD, n=31) for haploidentical HCT, or thymoglobulin (ATG, n=62) for matched unrelated donor (MUD) HCT. Results: With a median follow-up duration of 15.6 months (range, 0.2-63.6 months), 136 (68.3%) patients had CMV reactivation (median onset, 27.5 days) while 6 (3.0 %) patients developed clinically significant CMV disease, such as colitis, retinitis and encephalitis. The cumulative incidences of CMV reactivation within the first 100 days among the recipients of matched unrelated donor (MUD) (n=60), mismatched related donor or unrelated donor (MMRD/MMUD) (n=60), umbilical cord blood (UCB) (n=18) and matched related donor (MRD) (n=61) HCT were 71.6 %, 61.7 %, 50.0 % and 32.7 %, respectively (p&lt;0.001). There were no statistically significant differences in overall survival (OS, p=0.830) and disease-free survival (DFS, p=0.983) at 5 years between CMV-seropositive (D+/R+ or D-/R+, n=181) and CMV-seronegative recipients (D-/R- or D+/R-, n=18). There were also no significant differences in the cumulative incidences of CMV reactivation within 100 days (p=0.879), CMV end-organ disease (p=0.522) and non-relapse mortality (NRM, p=0.202), respectively. HCT-CI score of ≥1 (p=0.005) and the use of reduced intensity conditioning regimen (p&lt;0.001) were associated with a higher NRM at 2 years. There was also a trend towards higher NRM among patients with peak CMV DNA titers of above 1000 IU/ml, but this did not reach statistical significance (p=0.188). The secondary objective of this study was to determine the risk factors associated with CMV reactivation within the first 100 days post-transplant. There was no statistically significant impact of the donor or recipient CMV serostatus (p=0.790) on the risk of CMV reactivation. In multivariable analysis, the use of any T-cell depletion (p&lt;0.001) was a significant predictor of CMV reactivation. In a subset analysis comparing the 3 different methods of TCD, the use of ATG (p=0.004) and PTCy (p=0.005) was found to be associated with an increased risk of CMV reactivation, but not in patients receiving ex-vivo TCD (p=0.184) (Figure 1). Notably, patients receiving ex-vivo TCD haploidentical HCT was not associated with a higher risk of CMV reactivation as compared to the recipients of MRD HCT without any TCD. Conclusions: Our study concluded that CMV serologic status did not affect the incidence of CMV reactivation, NRM, OS and DFS in patients undergoing allogeneic HCT. The use of PTCy and ATG for GVHD prophylaxis, remains the most important risk factor for CMV reactivation in the era of pre-emptive therapy and hence, the need for aggressive prevention strategies in this vulnerable group of patients. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.


Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 4618-4618
Author(s):  
Ute E. Burkhardt ◽  
Joseph Kaplinsky ◽  
Cindy Desmarais ◽  
Kristen E. Stevenson ◽  
Edwin P. Alyea ◽  
...  

Although allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a highly effective treatment modality for many hematologic malignancies, a major treatment-associated toxicity is the induction of a prolonged state of T cell immunodeficiency in the transplant recipient, which in turn contributes to critical clinical outcomes such as infectious complications, and the risk of relapse. Targeted deep sequencing of the T cell receptor beta-chain (TCRβ) has emerged as a promising technology for enabling the qualitative and quantitative monitoring of T cell recovery following transplant with unprecedented resolution. Major challenges remain, however, in the establishment of informative analysis tools for characterization of global TCRβ repertoire dynamics. In the current work, we developed and applied a novel analysis approach as a mean to gain detailed biological insight into T cell reconstitution following allo-HSCT. To this end, we isolated naïve and memory CD4+ and CD8+ T cells from peripheral blood mononuclear cells of 14 patients with advanced chronic lymphocytic leukemia who underwent allo-HSCT following reduced-intensity doses of fludarabine and busulfan. From these T cell subpopulations, genomic DNA was extracted at post-transplant day 30 (d30) and later time points informative for thymic-independent (4 month post-transplant; d120) and thymic-dependent (1 year post-transplant; d365) T cell immune recovery. Subsequently, a template library for sequencing on an Illumina GA2 system was generated through PCR amplification of the TCRβ CDR3 region using an established panel of 45 Vβ- and 13 Jβ-specific primers. We obtained a median of 394,872 (range 0-26,426,784) productive reads across our 168 samples. As a comparison group, we further studied repertoire data from naïve and memory CD4+ and CD8+ T cells collected from 9 healthy adult volunteers. To characterize how transplant perturbs the TCR repertoire, we first compared VDJ usage between the transplanted patients and the healthy controls. For each of the post-transplant and control samples, we tallied the number of clones from all sequenced compartments (CD4+ and CD8+, naïve and memory) that used each of the several thousand possible VDJ combinations. We performed pairwise comparisons of the resulting VDJ distributions for all 253 sample pairs at days 30, 120 and 365 by calculating the R2 and, separately, X2 statistics. Permutation analysis demonstrated that control samples were more similar to each other than either post-transplant day 30, 120 or 365 samples (P=2.5-5.0x10-5, 2.5-5.0x10-5 and ≤2.5x10-5 by X2; 2.5-5.0x10-5, 5.5-5.7x10-4 and 1.0-1.2x10-4 by R2, respectively). Of note, whereas control samples demonstrated a similar VDJ usage, such similarity was not observed among post-transplant samples at day 30, 120 or 365 (P=0.65, 0.53, and 0.60 by X2; P=0.014, 0.38, and 0.43 by R2, respectively). These results demonstrate that VDJ usage in transplant recipients remains more heterogeneous than in healthy controls throughout the entire first year of reconstitution. To understand whether this heterogeneity reflects equilibrium or dynamic changes of the TCR repertoire, we visualized the time course of reconstitution using principal component analysis of VDJ usage. We observed marked dynamism, in which most transplant recipients both experienced a greater degree of change than was represented by the controls, and explored regions of VDJ usage very different from that of controls. Preliminarily, we observed that several transplant recipients became more similar to controls over time, while others did not. Our results demonstrate that post-transplant T cell reconstitution follows both personal and highly dynamic trajectories across a range of clinical courses, and suggest that TCR sequencing in larger sample sizes is a promising avenue for future study. Ongoing analyses focus on investigating the correlates of this dynamism among the 14 transplant recipients through subgroup analysis based on their clinical course and sequence-level analysis. The results obtained through these novel computational and systems methods will be integrated with other experimental measures of immune reconstitution including immunophenotyping and TCR excision circle (TREC) analysis. Disclosures: No relevant conflicts of interest to declare.


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