Sean McDonough

Low-Dose Interleukin-2 Therapy Restores Regulatory T Cell Homeostasis in Patients with Chronic Graft-Versus-Host Disease

Regulatory T cell homeostasis is restored in patients with chronic graft-versus-host disease who receive low-dose interleukin-2 therapy. Restoring Balance to the Immune System Hematopoietic stem cell transplantation can be a lifesaving therapy for patients with certain types of cancers or other blood disorders. However, it’s rare to find a perfect match, and transplants frequently occur from donors who are antigenically different from the recipient. When this happens, the graft itself can attack the host as foreign tissue, a response called graft-versus-host disease (GVHD). Matsuoka et al. now report that daily low-dose interleukin-2 (IL-2) can expand regulatory T cells (Tregs) and improve chronic GVHD. The authors studied the effects of daily low-dose IL-2 on different subsets of CD4+ T cells in patients with chronic GVHD. Conventional T cells in these patients had altered phosphorylation of the signaling molecule signal transducer and activator of transcription 5 (Stat5) and a functional deficiency in IL-2. When this IL-2 deficiency was replaced with their therapy, Stat5 phosphorylation levels were selectively increased in Tregs but decreased conventional T cells. Indeed, although daily low-dose IL-2 had minimal effects on conventional T cells, it induced a series of changes to Treg homeostasis that likely led to the establishment of immune tolerance. CD4+Foxp3+ regulatory T cells (Tregs) play a central role in the maintenance of immune tolerance after allogeneic hematopoietic stem cell transplantation. We recently reported that daily administration of low-dose interleukin-2 (IL-2) induces selective expansion of functional Tregs and clinical improvement of chronic graft-versus-host disease (GVHD). To define the mechanisms of action of IL-2 therapy, we examined the immunologic effects of this treatment on homeostasis of CD4+ T cell subsets after transplant. We first demonstrated that chronic GVHD is characterized by constitutive phosphorylation of signal transducer and activator of transcription 5 (Stat5) in conventional CD4+ T cells (Tcons) associated with elevated amounts of IL-7 and IL-15 and relative functional deficiency of IL-2. IL-2 therapy resulted in the selective increase of Stat5 phosphorylation in Tregs and a decrease of phosphorylated Stat5 in Tcons. Over an 8-week period, IL-2 therapy induced a series of changes in Treg homeostasis, including increased proliferation, increased thymic export, and enhanced resistance to apoptosis. Low-dose IL-2 had minimal effects on Tcons. These findings define the mechanisms whereby low-dose IL-2 therapy restores the homeostasis of CD4+ T cell subsets and promotes the reestablishment of immune tolerance.

Altered regulatory T cell homeostasis in patients with CD4 + lymphopenia following allogeneic hematopoietic stem cell transplantation

CD4+CD25+Foxp3+ Tregs have an indispensable role in the maintenance of tolerance after allogeneic HSC transplantation (HSCT). Patients with chronic graft-versus-host disease (GVHD) have fewer circulating Tregs, but the mechanisms that lead to this deficiency of Tregs after HSCT are not known. Here, we analyzed reconstitution of Tregs and conventional CD4+ T cells (Tcons) in patients who underwent allogeneic HSCT after myeloablative conditioning. Following transplant, thymic generation of naive Tregs was markedly impaired, and reconstituting Tregs had a predominantly activated/memory phenotype. In response to CD4+ lymphopenia after HSCT, Tregs underwent higher levels of proliferation than Tcons, but Tregs undergoing homeostatic proliferation also showed increased susceptibility to Fas-mediated apoptosis. Prospective monitoring of CD4+ T cell subsets revealed that Tregs rapidly expanded and achieved normal levels by 9 months after HSCT, but Treg levels subsequently declined in patients with prolonged CD4+ lymphopenia. This resulted in a relative deficiency of Tregs, which was associated with a high incidence of extensive chronic GVHD. These studies indicate that CD4+ lymphopenia is a critical factor in Treg homeostasis and that prolonged imbalance of Treg homeostasis after HSCT can result in loss of tolerance and significant clinical disease manifestations.

Double umbilical cord blood transplantation with reduced intensity conditioning and sirolimus-based GVHD prophylaxis

The main limitations to umbilical cord blood (UCB) transplantation (UCBT) in adults are delayed engraftment, poor immunological reconstitution and high rates of non-relapse mortality (NRM). Double UCBT (DUCBT) has been used to circumvent the issue of low cell dose, but acute GVHD remains a significant problem. We describe our experience in 32 subjects, who underwent DUCBT after reduced-intensity conditioning with fludarabine/melphalan/antithymocyte globulin and who received sirolimus and tacrolimus to prevent acute GVHD. Engraftment of neutrophils occurred in all patients at a median of 21 days, and platelet engraftment occurred at a median of 42 days. Three subjects had grade II–IV acute GVHD (9.4%) and chronic GVHD occurred in four subjects (cumulative incidence 12.5%). No deaths were caused by GVHD and NRM at 100 days was 12.5%. At 2 years, NRM, PFS and OS were 34.4, 31.2 and 53.1%, respectively. As expected, immunologic reconstitution was slow, but PFS and OS were associated with reconstitution of CD4+ and CD8+ lymphocyte subsets, suggesting that recovery of adaptive immunity is required for the prevention of infection and relapse after transplantation. In summary, sirolimus and tacrolimus provide excellent GVHD prophylaxis in DUCBT, and this regimen is associated with low NRM after DUCBT.

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.

Bortezomib-Based Graft-Versus-Host Disease Prophylaxis in HLA-Mismatched Unrelated Donor Transplantation

PURPOSE HLA-mismatched unrelated donor (MMUD) hematopoietic stem-cell transplantation (HSCT) is associated with increased graft-versus-host disease (GVHD) and impaired survival. In reduced-intensity conditioning (RIC), neither ex vivo nor in vivo T-cell depletion (eg, antithymocyte globulin) convincingly improved outcomes. The proteasome inhibitor bortezomib has immunomodulatory properties potentially beneficial for control of GVHD in T-cell-replete HLA-mismatched transplantation. PATIENTS AND METHODS We conducted a prospective phase I/II trial of a GVHD prophylaxis regimen of short-course bortezomib, administered once per day on days +1, +4, and +7 after peripheral blood stem-cell infusion plus standard tacrolimus and methotrexate in patients with hematologic malignancies undergoing MMUD RIC HSCT. We report outcomes for 45 study patients: 40 (89%) 1-locus and five (11%) 2-loci mismatches (HLA-A, -B, -C, -DRB1, or -DQB1), with a median of 36.5 months (range, 17.4 to 59.6 months) follow-up. RESULTS The 180-day cumulative incidence of grade 2 to 4 acute GVHD was 22% (95% CI, 11% to 35%). One-year cumulative incidence of chronic GVHD was 29% (95% CI, 16% to 43%). Two-year cumulative incidences of nonrelapse mortality (NRM) and relapse were 11% (95% CI, 4% to 22%) and 38% (95% CI, 24% to 52%), respectively. Two-year progression-free survival and overall survival were 51% (95% CI, 36% to 64%) and 64% (95% CI, 49% to 76%), respectively. Bortezomib-treated HLA-mismatched patients experienced rates of NRM, acute and chronic GVHD, and survival similar to those of contemporaneous HLA-matched RIC HSCT at our institution. Immune recovery, including CD8(+) T-cell and natural killer cell reconstitution, was enhanced with bortezomib. CONCLUSION A novel short-course, bortezomib-based GVHD regimen can abrogate the survival impairment of MMUD RIC HSCT, can enhance early immune reconstitution, and appears to be suitable for prospective randomized evaluation.

Clearance of CMV viremia and survival after double umbilical cord blood transplantation in adults depends on reconstitution of thymopoiesis

Umbilical cord blood grafts are increasingly used as sources of hematopoietic stem cells in adults. Data regarding the outcome of this approach in adults are consistent with delayed and insufficient immune reconstitution resulting in high infection-related morbidity and mortality. Using cytomegalovirus (CMV)-specific immunity as a paradigm, we evaluated the status, mechanism, and clinical implications of immune reconstitution in adults with hematologic malignancies undergoing unrelated double unit cord blood transplantation. Our data indicate that CD8(+) T cells capable of secreting interferon-gamma (IFN-gamma) in a CMV-specific enzyme-linked immunosorbent spot (ELISpot) assay are detectable at 8 weeks after transplantation, before reconstitution of thymopoiesis, but fail to clear CMV viremia. Clearance of CMV viremia occurs later and depends on the recovery of CD4(+)CD45RA(+) T cells, reconstitution of thymopoiesis, and attainment of T-cell receptor rearrangement excision circle (TREC) levels of 2000 or more copies/mug DNA. In addition, overall survival was significantly higher in patients who displayed thymic regeneration and attainment of TREC levels of 2000 or more copies/mug DNA (P = .005). These results indicate that reconstitution of thymopoiesis is critical for long-term clinical outcome in adult recipients of umbilical cord blood transplant. The trial was prospectively registered at http://www.clinicaltrials.gov (NCT00133367).

Rituximab prophylaxis prevents corticosteroid-requiring chronic GVHD after allogeneic peripheral blood stem cell transplantation: results of a phase 2 trial.

B cells are implicated in the pathophysiology of chronic graft-vs-host disease (GVHD), and phase 2 trials suggest that B cell depletion can treat established chronic GVHD. We hypothesized that posttransplantation B cell depletion could prevent the occurrence of chronic GVHD. We performed a 65-patient phase 2 trial of rituximab (375 mg/m(2) IV), administered at 3, 6, 9, and 12 months after transplantation. Rituximab administration was safe without severe infusional adverse events. The cumulative incidences of chronic GVHD and systemic corticosteroid-requiring chronic GVHD at 2 years from transplantation were 48% and 31%, respectively, both lower than the corresponding rates in a concurrent control cohort (60%, P = .1, and 48.5%, P = .015). There was no difference in relapse incidence, but treatment-related mortality at 4 years from transplantation was significantly lower in treated subjects when compared with controls (5% vs 19%, P = .02), and overall survival was superior at 4 years (71% vs 56%, P = .05). At 2 years from transplantation, the B-cell activating factor/B-cell ratio was significantly higher in subjects who developed chronic GVHD in comparison with those without chronic GVHD (P = .039). Rituximab can prevent systemic corticosteroid-requiring chronic GVHD after peripheral blood stem cell transplantation and should be tested in a prospective randomized trial.

Autologous CLL cell vaccination early after transplant induces leukemia-specific T cells

BACKGROUND Patients with advanced hematologic malignancies remain at risk for relapse following reduced-intensity conditioning (RIC) allogeneic hematopoietic stem cell transplantation (allo-HSCT). We conducted a prospective clinical trial to test whether vaccination with whole leukemia cells early after transplantation facilitates the expansion of leukemia-reactive T cells and thereby enhances antitumor immunity. METHODS We enrolled 22 patients with advanced chronic lymphocytic leukemia (CLL), 18 of whom received up to 6 vaccines initiated between days 30 and 45 after transplantation. Each vaccine consisted of irradiated autologous tumor cells admixed with GM-CSF-secreting bystander cells. Serial patient PBMC samples following transplantation were collected, and the impact of vaccination on T cell activity was evaluated. RESULTS At a median follow-up of 2.9 (range, 1-4) years, the estimated 2-year progression-free and overall survival rates of vaccinated subjects were 82% (95% CI, 54%-94%) and 88% (95% CI, 59%-97%), respectively. Although vaccination only had a modest impact on recovering T cell numbers, CD8+ T cells from vaccinated patients consistently reacted against autologous tumor, but not alloantigen-bearing recipient cells with increased secretion of the effector cytokine IFN-γ, unlike T cells from nonvaccinated CLL patients undergoing allo-HSCT. Further analysis confirmed that 17% (range, 13%-33%) of CD8+ T cell clones isolated from 4 vaccinated patients by limiting dilution of bulk tumor-reactive T cells solely reacted against CLL-associated antigens. CONCLUSION Our studies suggest that autologous tumor cell vaccination is an effective strategy to advance long-term leukemia control following allo-HSCT. TRIAL REGISTRATION Clinicaltrials.gov NCT00442130. FUNDING NCI (5R21CA115043-2), NHLBI (5R01HL103532-03), and Leukemia and Lymphoma Society Translational Research Program.

A phase I study of lenalidomide in combination with fludarabine and rituximab in previously untreated CLL/SLL.

Lenalidomide is an immunomodulatory drug related to thalidomide that has recently been reported to have significant single agent activity in relapsed CLL, with response rates of 35-50% including some complete responses1,2. The mechanism of action is unknown but appears to be immune-mediated given that lenalidomide alters cytokine levels and stimulates T and NK cell function, and lacks cytotoxicity against CLL in vitro3. In CLL patients, the administration of lenalidomide can be associated with tumor flare, a syndrome of painful enlarging lymphadenopathy, increased white count, fever, and rash1,2. This tumor flare can potentially escalate to become life-threatening, with renal insufficiency, tumor lysis or a systemic inflammatory response4,5. The mechanism of tumor flare remains unknown.

Low telomerase activity in CD4 + regulatory T cells in patients with severe chronic GVHD after hematopoietic stem cell transplantation

CD4(+)CD25(+)Foxp3(+) regulatory T cells (Treg) play an important role in the control of chronic graft-versus-host disease (cGVHD). In this study, we examined telomere length and telomerase activity of Treg and conventional CD4(+) T cells (Tcon) in 61 patients who survived more than 2 years after allogeneic hematopoietic stem cell transplantation. Cell proliferation and expression of Bcl-2 were also measured in each subset. Treg telomere length was shorter and Treg telomerase activity was increased compared with Tcon (P < .0001). After transplantation, Treg were also more highly proliferative than Tcon (P < .0001). Treg number, telomerase activity, and expression of Bcl-2 were each inversely associated with severity of cGVHD. These data indicate that activation of telomerase is not sufficient to prevent telomere shortening in highly proliferative Treg. However, telomerase activation is associated with increased Bcl-2 expression and higher Treg numbers in patients with no or mild cGVHD. In contrast, patients with moderate or severe cGVHD have fewer Treg with lower levels of telomerase activity and Bcl-2 expression. These results suggest that failure to activate Treg telomerase may restrict proliferative capacity and increase apoptotic susceptibility, resulting in the loss of peripheral tolerance and the development of cGVHD.