Durability of clinical and immunologic responses to extended low-dose interleukin-2 therapy in patients with refractory chronic graft-versus-host disease.

Chronic graft-versus-host disease (cGVHD) remains a frequent cause of non-relapse morbidity and mortality after allogeneic hematopoietic stem cell transplantation. In our single center trials of low-dose interleukin-2 (LD IL-2), the immunomodulatory properties of regulatory T cells (Tregs) have been harnessed to treat steroid-refractory cGVHD (SR-cGVHD) safely and effectively in adults and children. In these trials, 50-60% of patients showed clinical improvement of their cGVHD manifestations with partial responses at the primary response endpoint of 8-12 weeks. Many patients continued extended duration LD IL-2 therapy and achieved deeper clinical responses, including some complete responses. However, the durability of the clinical and immunologic improvement following IL-2 discontinuation has not been reported previously. We examined 20 adult and 2 pediatric patients who received extended duration LD IL-2 for a median of 103 weeks (range, 21-258) and had stable improvement or resolution of their cGVHD symptoms before discontinuing LD IL-2 therapy. The median follow-up after stopping IL-2 was 203 weeks (range 92-599). During this time, 16 patients (73%) were able to wean off all systemic immunosuppression without disease flare or progression. Among 13 patients with available immune cell data, the median fold change in absolute Treg count was 0.58 between 1 to 10 weeks after stopping IL-2 whereas CD4+ conventional T-cell (Tcon) and CD8+ T-cell numbers remained stable. Despite a decline in Treg numbers after IL-2 discontinuation, Treg numbers remained above the pre-treatment baseline. In addition, many patients had sustained clinical improvement after stopping IL-2, suggesting that extended IL-2 therapy can lead to immune tolerance.

A phase 1 study of donor regulatory T-cell infusion plus low-dose interleukin-2 for steroid-refractory chronic graft-vs-host disease.

Chronic graft-versus-host disease (cGVHD) remains a frequent cause of nonrelapse morbidity and mortality after allogeneic hematopoietic stem cell transplantation. Despite recent advances, options for steroid-refractory (SR) cGVHD are limited. In previous trials of low-dose interleukin-2 (LD IL-2), the immunomodulatory properties of regulatory T cells (Tregs) have been harnessed to treat SR-cGVHD safely and effectively. In the present study, we combined a single infusion of Treg-enriched lymphocytes (Treg DLI) from the original stem cell donor with in vivo Treg expansion using LD IL-2 (1 × 106 IU/m2 per day for 8 weeks) in 25 adult patients with SR-cGVHD. Treg were not expanded ex vivo. Treg DLI was initiated at 0.1 × 106 cells per kg patient and escalated to a maximum dose of 1 × 106 cells per kg. Treg DLI plus LD IL-2 was well tolerated and led to partial responses (PR) in 5 of 25 patients (20%) after 8 weeks of therapy. Ten additional patients (40%) had stable disease with minor responses not meeting PR criteria. Patients at all dose levels had similar Treg expansion without significant changes in CD4+ conventional T cells or CD8+ T cells. High-throughput sequencing of the T-cell receptor ß locus showed selective improvement of Treg diversity. A subset of DLI-derived Treg clones showed preferential expansion at week 8 and long-term persistence 1-year postinfusion. We demonstrate for the first time that infusion of polyclonal healthy donor Tregs followed by expansion with LD IL-2 is safe in patients with SR-cGVHD, thus establishing a foundation for future adoptive Treg therapies in the posttransplant setting. This trial was registered at www.clinicaltrials.gov as #NCT01937468.

Microbiota dynamics in a randomized trial of gut decontamination during allogeneic hematopoietic cell transplantation.

BACKGROUNDGut decontamination (GD) can decrease the incidence and severity of acute graft-versus-host disease (aGVHD) in murine models of allogeneic hematopoietic cell transplantation (HCT). In this pilot study, we examined the impact of GD on gut microbiome composition and the incidence of aGVHD in HCT patients.METHODSWe randomized 20 patients undergoing allogeneic HCT to receive (GD) or not receive (no-GD) oral vancomycin-polymyxin B from day -5 through neutrophil engraftment. We evaluated shotgun metagenomic sequencing of serial stool samples to compare the composition and diversity of the gut microbiome between study arms. We assessed clinical outcomes in the 2 arms and performed strain-specific analyses of pathogens that caused bloodstream infections (BSI).RESULTSThe 2 arms did not differ in the predefined primary outcome of Shannon diversity of the gut microbiome at 2 weeks post-HCT (genus, P = 0.8; species, P = 0.44) or aGVHD incidence (P = 0.58). Immune reconstitution of T cell and B cell subsets was similar between groups. Five patients in the no-GD arm had 8 BSI episodes versus 1 episode in the GD arm (P = 0.09). The BSI-causing pathogens were traceable to the gut in 7 of 8 BSI episodes in the no-GD arm, including Staphylococcus species.CONCLUSIONWhile GD did not differentially affect Shannon diversity or clinical outcomes, our findings suggest that GD may protect against gut-derived BSI in HCT patients by decreasing the prevalence or abundance of gut pathogens.TRIAL REGISTRATIONClinicalTrials.gov NCT02641236.FUNDINGNIH, Damon Runyon Cancer Research Foundation, V Foundation, Sloan Foundation, Emerson Collective, and Stanford Maternal & Child Health Research Institute.

Monitoring PD-1 Phosphorylation to Evaluate PD-1 Signaling during Antitumor Immune Responses.

PD-1 expression marks activated T cells susceptible to PD-1-mediated inhibition but not whether a PD-1-mediated signal is being delivered. Molecular predictors of response to PD-1 immune checkpoint blockade (ICB) are needed. We describe a monoclonal antibody (mAb) that detects PD-1 signaling through the detection of phosphorylation of the immunotyrosine switch motif (ITSM) in the intracellular tail of mouse and human PD-1 (phospho-PD-1). We showed PD-1+ tumor-infiltrating lymphocytes (TILs) in MC38 murine tumors had high phosphorylated PD-1, particularly in PD-1+TIM-3+ TILs. Upon PD-1 blockade, PD-1 phosphorylation was decreased in CD8+ TILs. Phospho-PD-1 increased in T cells from healthy human donors after PD-1 engagement and decreased in patients with Hodgkin lymphoma following ICB. These data demonstrate that phosphorylation of the ITSM motif of PD-1 marks dysfunctional T cells that may be rescued with PD-1 blockade. Detection of phospho-PD-1 in TILs is a potential biomarker for PD-1 immunotherapy responses.

Impact of cryopreservation and transit times of allogeneic grafts on hematopoietic and immune reconstitution.

We sought to evaluate the impact of cryopreservation of unrelated donor (URD) peripheral blood stem cell (PBSC) grafts on engraftment, chimerism, and immune reconstitution in the context of the COVID-19 pandemic. We reviewed stem cell product characteristics and clinical outcomes in 101 patients receiving cryopreserved PBSCs from URDs between January 1, 2019 and 31 December, 2020, compared with 203 patients receiving fresh URD PBSCs. We observed no differences in 6-month overall survival, progression-free survival, or nonrelapse mortality. Patients receiving cryopreserved PBSCs had delayed platelet engraftment and impaired reconstitution of white blood cells and T-cell subsets at day 30. Thirty-four percent of patients receiving cryopreserved grafts had CD3 chimerism <50% at day 30 after transplantation, compared with 14% of patients receiving fresh PBSCs (P = .0002). At day 100, this difference persisted (CD3+ chimerism <50%: 17% of cryopreserved cohort vs 6% of fresh cohort; P = .016). Greater product age at infusion was associated with increased graft failure, independent of cryopreservation. Receipt of grafts >48 hours old at time of cryopreservation or infusion significantly increased the risk of graft failure (subdistribution hazard ratio = 4.57; 95% confidence interval, 1.71-12.3; P = .0025). Our data indicate that cryopreservation is associated with similar overall short-term clinical outcomes compared with fresh PBSC. However, patients must be monitored closely for increased risk of other potentially adverse outcomes, including graft failure and poor immune recovery, particularly for grafts with older overall age at infusion. Longer-term follow-up is needed to determine impact on relapse and survival.

Efficacy and immunologic effects of extracorporeal photopheresis plus interleukin-2 in chronic graft-versus-host disease.

Chronic graft-versus-host disease (cGVHD) affects >50% of hematopoietic stem cell transplant patients. Extracorporeal photopheresis (ECP), an immunomodulatory therapy, provides clinical benefit in steroid-refractory (SR) cGVHD, possibly via regulatory T (Treg) and natural killer (NK) cell expansion. We demonstrated that low-dose interleukin-2 (IL2) led to clinical improvement in SR-cGVHD and stimulated preferential Treg and NK-cell expansion with minimal effect on conventional T (Tcon) cells. We evaluated the effect of ECP (weeks 1-16) plus IL2 (1 × 106 IU/m2, weeks 9-16) in 25 adult patients with SR-cGVHD in a prospective phase 2 trial. Objective responses occurred in 29% and 62% of evaluable patients at weeks 8 (ECP alone) and 16 (ECP plus IL2), respectively. Eight weeks of ECP alone was associated with a marked decline in CD4+ Tcon (P = .03) and CD8+ T cells (P = .0002), with minimal change in Treg cells, Treg:Tcon cell ratio, or NK cells. Adding IL2 induced an increase in Treg cells (P < .05 at weeks 9-16 vs week 8), Treg:Tcon cell ratio (P < .0001 at weeks 9-16 vs week 8), and NK cells (P < .05 at weeks 9-16 vs week 8). Patients responding to ECP alone had significantly fewer CD4+ Tcon and CD8+ T cells at baseline compared with patients who responded after IL2 addition and patients who did not respond; neither Treg nor NK cells were associated with response to ECP alone. Altogether, ECP plus IL2 is safe and effective in patients with SR-cGVHD. ECP and IL2 have distinct immunologic effects, suggesting different therapeutic mechanisms of action. This trial was registered at www.clinicaltrials.gov as #NCT02340676.

Functional analysis of clinical response to low-dose IL-2 in patients with refractory chronic graft-versus-host disease.

Patients with chronic graft-versus-host disease (cGVHD) have a paucity of regulatory CD4 T cells (CD4Tregs) that mediate peripheral tolerance. In clinical trials, daily low-dose interleukin-2 (IL-2) has been administered safely for prolonged periods in patients with steroid-refractory cGVHD. Peripheral CD4Tregs expand dramatically in all patients during IL-2 therapy but clinical improvement was observed in ∼50% of patients. Here, we examined the impact of low-dose IL-2 therapy on functional T-cell markers and the T-cell repertoire within CD4Tregs, conventional CD4 T cells (CD4Tcons), and CD8+ T cells. IL-2 had profound effects on CD4Tregs homeostasis in both response groups including selective expansion of the naive subset, improved thymic output, and increased expression of Ki67, FOXP3, and B-cell lymphoma 2 within CD4Tregs. Similar changes were not seen in CD4Tcons or CD8 T cells. Functionally, low-dose IL-2 enhanced, in vitro, CD4Treg-suppressive activity in both response groups, and all patient CD4Tcons were similarly suppressed by healthy donor CD4Tregs. High-throughput sequencing of the T-cell receptor ß (TCRß) locus demonstrated that low-dose IL-2 therapy increased TCR repertoire diversity and decreased evenness within CD4Tregs without affecting CD4Tcons or CD8 T cells. Using clone-tracking analysis, we observed rapid turnover of highly prevalent clones in CD4Tregs as well as the conversion of CD4Tcons to CD4Tregs. After 12 weeks of daily IL-2, clinical responders had a greater influx of novel clones within the CD4Treg compartment compared with nonresponders. Further studies to define the function and specificity of these novel CD4Treg clones may help establish the mechanisms whereby low-dose IL-2 therapy promotes immune tolerance.

Effect of Antihuman T Lymphocyte Globulin on Immune Recovery after Myeloablative Allogeneic Stem Cell Transplantation with Matched Unrelated Donors: Analysis of Immune Reconstitution in a Double-Blind Randomized Controlled Trial.

We recently conducted a randomized double-blind study in which we demonstrated that moderate/severe chronic graft-versus-host disease (cGVHD) but not cGVHD-free survival was reduced in patients receiving anti-T lymphocyte globulin (ATLG) versus placebo. In a companion study we performed immunophenotypic analysis to determine the impact of ATLG on immune reconstitution (IR) and to correlate IR with clinical outcomes. The randomized study (n = 254) included patients (aged 18 to 65 years) who underwent myeloablative transplants for acute myeloid leukemia, myelodysplastic syndrome, or acute lymphoblastic leukemia from HLA-matched unrelated donors. Ninety-one patients consented for the companion IR study (ATLG = 44, placebo = 47). Blood samples were collected on days 30, 100, 180, and 360 after hematopoietic cell transplantation (HCT), and multiparameter flow cytometry was performed in a blinded fashion. Reconstitution of CD3+ and CD4+ T cells was delayed up to 6 months post-HCT in the ATLG arm, whereas absolute regulatory T cell (Treg) (CD4+25+127-) numbers were lower only in the first 100 days. Analysis of the CD4+ Treg and conventional T cells (Tconv) (CD4+25-127+) compartments showed a profound absence of naive Tregs and Tconv in the first 100 days post-HCT, with very slow recovery for 1 year. B cell and natural killer cell recovery were similar in each arm. Higher absolute counts of CD3+, CD4+, CD8+ T, Tregs, and Tconv were associated with improved overall survival, progression-free survival, and nonrelapse mortality but not moderate/severe cGVHD. Although ATLG delays CD3+ and CD4+ T cell recovery post-transplant, it has a relative Treg sparing effect after the early post-HCT period, with possible implications for protection from cGVHD. ATLG severely compromises the generation of naive CD4+ cells (Treg and Tconv), potentially affecting the diversity of the TCR repertoire and T cell responses against malignancy and infection.

Bortezomib-based immunosuppression after reduced-intensity conditioning hematopoietic stem cell transplantation: randomized phase II results.

Aprior phase I/II trial of bortezomib/tacrolimus/methotrexate prophylaxis after human leukocyte antigen (HLA)-mismatched reduced intensity conditioning allogeneic hematopoietic stem cell transplantation documented low acute graft-versus-host disease incidence, with promising overall and progression-free survival. We performed an open-label three-arm 1:1:1 phase II randomized controlled trial comparing grade II-IV acute graft-versus-host disease between conventional tacrolimus/methotrexate (A) versus bortezomib/tacrolimus/methotrexate (B), and versus bortezomib/sirolimus/tacrolimus (C), in reduced intensity conditioning allogeneic transplantation recipients lacking HLA-matched related donors. The primary endpoint was grade II-IV acute graft-versus-host disease incidence rate by day +180. One hundred and thirty-eight patients (A 46, B 45, C 47) with a median age of 64 years (range: 24-75), varying malignant diagnoses and disease risk (low 14, intermediate 96, high/very high 28) received 7-8/8 HLA-mismatched (40) or matched unrelated donor (98) grafts. Median follow up in survivors was 30 months (range: 14-46). Despite early immune reconstitution differences, day +180 grade II-IV acute graft-versus-host disease rates were similar (A 32.6%, B 31.1%, C 21%; P=0.53 for A vs B, P=0.16 for A vs C). The 2-year non-relapse mortality incidence was similar (A 14%, B 16%, C 6.4%; P=0.62), as were relapse (A 32%, B 32%, C 38%; P=0.74), chronic graft-versus-host disease (A 59%, B 60% C 55%; P=0.66), progression-free survival (A 54%, B 52%, C 55%; P=0.95), and overall survival (A 61%, B 62%, C 62%; P=0.98). Overall, the bortezomib-based regimens evaluated did not improve outcomes compared with tacrolimus/methotrexate therapy. clinicaltrials.gov Identifier: 01754389.

Unbalanced recovery of regulatory and effector T cells after allogeneic stem cell transplantation contributes to chronic GVHD.

The development and maintenance of immune tolerance after allogeneic hematopoietic stem cell transplantation (HSCT) requires the balanced reconstitution of donor-derived CD4 regulatory T cells (CD4Tregs) as well as effector CD4 (conventional CD4 T cells [CD4Tcons]) and CD8 T cells. To characterize the complex mechanisms that lead to unbalanced recovery of these distinct T-cell populations, we studied 107 adult patients who received T-replete stem cell grafts after reduced-intensity conditioning. Immune reconstitution of CD4Treg, CD4Tcon, and CD8 T cells was monitored for a 2-year period. CD3 T-cell counts gradually recovered to normal levels during this period but CD8 T cells recovered more rapidly than either CD4Tregs or CD4Tcons. Reconstituting CD4Tregs and CD4Tcons were predominantly central memory (CM) and effector memory (EM) cells and CD8 T cells were predominantly terminal EM cells. Thymic generation of naive CD4Tcon and CD8 T cells was maintained but thymic production of CD4Tregs was markedly decreased with little recovery during the 2-year study. T-cell proliferation was skewed in favor of CM and EM CD4Tcon and CD8 T cells, especially 6 to 12 months after HSCT. Intracellular expression of BCL2 was increased in CD4Tcon and CD8 T cells in the first 3 to 6 months after HSCT. Early recovery of naive and CM fractions within each T-cell population 3 months after transplant was also strongly correlated with the subsequent development of chronic graft-versus-host disease (GVHD). These dynamic imbalances favor the production, expansion, and persistence of effector T cells over CD4Tregs and were associated with the development of chronic GVHD.

A Bortezomib-Based Regimen Offers Promising Survival and Graft-versus-Host Disease Prophylaxis in Myeloablative HLA-Mismatched and Unrelated Donor Transplantation: A Phase II Trial.

Hematopoietic stem cell transplantation (HSCT) recipients lacking HLA-matched related donors have increased graft-versus-host disease (GVHD) and nonrelapse mortality (NRM). Bortezomib added to reduced-intensity conditioning can offer benefit in T cell-replete HLA-mismatched HSCT and may also benefit myeloablative conditioning (MAC) transplants. We conducted a phase II trial of short-course bortezomib plus standard tacrolimus/methotrexate after busulfan/fludarabine MAC in 34 patients with predominantly myeloid malignancies. Fourteen (41%) received 8/8 HLA-matched unrelated donor (MUD) and 20 (59%) received 7/8 HLA-mismatched related/unrelated donor peripheral blood stem cell grafts. Median age was 49 years (range, 21 to 60), and median follow-up was 25 months (range, 11 to 36). The regimen was well tolerated. No dose modifications were required. Neutrophil and platelet engraftment occurred at a median of 14 (range, 10 to 33) and 17 (range, 10 to 54) days, respectively. Median 30-day donor chimerism was 99% (range, 90 to 100), and 100-day grades II to IV and III to IV acute GVHD incidence was 32% and 12% respectively. One-year chronic GVHD incidence was 50%. Two-year cumulative incidence of both NRM and relapse was 16%. Two-year progression-free and overall survival rates were 70% and 71%, respectively. Outcomes were comparable to an 8/8 MUD MAC cohort (n = 45). Immune reconstitution was robust. Bortezomib-based MAC HSCT is well tolerated, with HLA-mismatched outcomes comparable with 8/8 MUD MAC HSCT, and is suitable for randomized evaluation. (clinicaltrials.gov: NCT01323920.).

Post-transplantation B cell activating factor and B cell recovery before onset of chronic graft-versus-host disease.

Excessive levels of B cell activating factor (BAFF) are found in patients with active chronic graft-versus-host disease (cGVHD). In mice, BAFF has been shown to be essential for B cell recovery after myeloablation. To assess how BAFF levels relate to transplantation factors and subsequent development of cGVHD, we prospectively monitored 412 patients in the first year after allogeneic peripheral blood or bone marrow hematopoietic stem cell transplantation (HSCT) and censored data at time of cGVHD onset. In patients who did not develop cGVHD, we affirmed a temporal pattern of gradually decreasing BAFF levels as B cell numbers increase after myeloablative conditioning. In contrast, after reduced-intensity conditioning, BAFF levels remained high throughout the first post-HSCT year, suggesting that the degree of myeloablation resulted in delayed B cell recovery associated with persistence of higher BAFF levels. Given that high BAFF/B cell ratios have been associated with active cGVHD, we examined differences in early BAFF/B cell ratios and found significantly different BAFF/B cell ratios at 3 months post-HSCT only after myeloablative conditioning in patients who subsequently developed cGVHD. In addition to HSCT conditioning type, the use of sirolimus was significantly associated with higher BAFF levels after HSCT, and this also was potentially related to lower B cell numbers. Taken together, our results are important for interpreting BAFF measurements in cGVHD biomarker studies.

Immune reconstitution after double umbilical cord blood stem cell transplantation: comparison with unrelated peripheral blood stem cell transplantation.

Double umbilical cord blood (DUCB) transplantation is an accepted transplantation strategy for patients without suitable human leukocyte antigen (HLA) matched donors. However, DUCB transplantation is associated with increased morbidity and mortality because of slow recovery of immunity and a high risk of infection. To define the differences in immune reconstitution between DUCB transplantation and HLA matched unrelated donor (MUD) transplantation, we performed a detailed, prospective analysis of immune reconstitution in 42 DUCB recipients and 102 filgrastim-mobilized unrelated peripheral blood stem cell recipients. Reconstitution of CD3 T cells was significantly delayed in the DUCB cohort compared with the MUD cohort for 1 to 6 months posttransplantation (P < .001), including naive (CD45RO-) and memory (CD45RO+) CD4 T cells, regulatory (CD4CD25) T cells, and CD8 T cells. In contrast, CD19 B cells recovered more rapidly in the DUCB cohort and numbers remained significantly greater from 3 to 24 months after transplantation (P = .001). CD56CD16 natural killer (NK) cells also recovered more rapidly in DUCB recipients and remained significantly greater from 1 to 24 months after transplantation. B cell activating factor (BAFF) levels were higher in the DUCB cohort at 1 month (P < .001), were similar in both cohorts at 3 and 6 months, and were lower in the DUCB cohort at 12 months (P = .002). BAFF/CD19 B cell ratios were lower in the DUCB cohort at 3 (P = .045), 6 (P = .02), and 12 months (P = .002) after transplantation. DUCB recipients had more infections within the first 100 days after transplantation (P < .001), and there was less chronic graft-versus-host disease (P < .001), but there were no differences in cumulative incidence of relapse, nonrelapse death, progression-free survival, or overall survival between the 2 groups. These results suggest that increased risk of infections is specifically associated with delayed reconstitution of all major T cell subsets, but the increased risk is limited to the first 3 months after DUCB transplantation. There is no increased risk of relapse, suggesting that graft-versus-leukemia activity is maintained. Early reconstitution of B cells and NK cells may, in part, account for these findings.