Low-dose IL-2 Therapy Research Articles

Research Highlights

Single-cell RNA-seq Reveals New Types of Human Blood Dendritic Cells, Monocytes, and Progenitors Villani A-C, Satija R, Reynolds G, et al. Science. 2017; 356(6335). Research in immunology is often complicated by challenges in clear communication: when we publish our work, are we talking about the same cells? The field is often fluid, with new cell types announced every few months. The past decade alone has seen the arrival of Th17 and Th22 cells, regulatory B cells, and a raft of innate lymphoid cells. When investigating leukocyte subsets in basic or translational studies, or when immune phenotyping patient cells in clinical trials, it is often frustrating to find comparisons between different studies impossible. Markers used to phenotype cells are different, and the gating strategies diverse. Replicating studies can be problematic, and understanding how various cells sit in a classification system is virtually impossible. To overcome the biased strategy of identifying and classifying leukocyte populations using expression of a specific set of surface markers or transcription factors, Villani and colleagues used deep single-cell RNA sequencing (scRNA-Seq) analysis of approximately 2400 cells from healthy donors.1 In this study, the focus was on dendritic cells and monocytes, and therefore HLA-DR+ lineage− cells were used. Transcriptomics have revolutionised studies in immunology and the rapidly evolving technology has accelerated discoveries. scRNA-Seq in particular, has brought about a radical shift in cellular analysis. RNA-Seq is largely replacing gene expression microarrays, because it allows highly sensitive and powerful analysis of expression across the transcriptome, returning data on both known and novel RNA. Villani et al used this strategy coupled with functional analyses to completely reclassify dendritic cells and monocytes based on a specific cell surface molecules. The proposed new classification system includes 6 dendritic cell subsets and 4 monocyte subsets, termed DC1-6 and Mono1-4, respectively. This hugely simplifies and validates the classification of cells in what is often a confusing field and ensures that dialogue is not lost in translation between different studies. Such an approach may be applied to a number of other leukocyte populations, with the hope that one day, we all have a common immunological language. REFERENCE Villani AC, Satija R, Reynolds G, et al. Single-cell RNA-seq reveals new types of human blood dendritic cells, monocytes, and progenitors. Science. 2017;356. IL-2 Therapy Restores Regulatory T-cell Dysfunction Induced by Calcineurin Inhibitors Whitehouse G, Gray E, Mastoridis S, et al. Proc Natl Acad Sci U S A. 2017 ;114(27):7083–7088. Regulatory T (Treg) cells are one of the major contenders in the field of transplant tolerance, and with trials in full swing, an accessible clinical therapy is fast approaching. The reality of introducing new therapies to transplantation, however, is complicated by the presence of regimens which already produce excellent short-term results. Immunosuppression withdrawal may help reveal the effects of a new therapy but is risky. The lack of useful primary outcome measures other than biopsy-proven rejection, and the inability for clinical trials to monitor outcomes over the long-term further complicate the situation. The current status is therefore to introduce cellular therapies, such as Treg cells, into a cocktail of active immunosuppressants with the risk that these completely neutralize any beneficial effect. Understanding how Treg cells behave in these situations is therefore vital. In the experimental setting, the challenge is separating the effects of drug immunosuppression from those of Treg cells. Although there are some data to show that certain immunosuppressive regimens appear more facilitative, such as alemtuzumab and rapamycin, the data are limited. In general, there is some agreement that the majority of immunosuppressants are unlikely to spare Treg cells, with calcineurin inhibitors (CNIs) being obvious culprits. In the study from Whitehouse and colleagues, CNIs were shown to be specifically detrimental to the most effective Treg cells by reducing their access to IL-2.1 Treg cells from patients on tacrolimus have reduced CD25 expression, low sensitivity to low levels of IL-2, and increased cell death. In an important finding, exogenous IL-2 was found to restore the functionality of Tregs. IL-2 synergized with CNI treatment in an in vivo model, without enhancing the activity of effector T cells. Interest in IL-2 is not new, with low-dose IL-2 therapy showing significant promise in the treatment of autoimmune diseases.2 The study from Whitehouse et al. however provides a useful mechanistic explanation for these findings and a rationale for combined application of drug immunosuppression with Treg cellular therapy. REFERENCES Whitehouse G, Gray E, Mastoridis S, et al. IL-2 therapy restores regulatory T-cell dysfunction induced by calcineurin inhibitors. Proc Natl Acad Sci U S A. 2017;114:7083–7088. Klatzmann D, Abbas AK. The promise of low-dose interleukin-2 therapy for autoimmune and inflammatory diseases. Nat Rev Immunol. 2015;15:283–294.

Novel therapies for immune-mediated inflammatory diseases: What can we learn from their use in rheumatoid arthritis, spondyloarthritis, systemic lupus erythematosus, psoriasis, Crohn's disease and ulcerative colitis?

The past three decades have witnessed remarkable advances in our ability to target specific elements of the immune and inflammatory response, fuelled by advances in both biotechnology and disease knowledge. As well as providing superior treatments for immune-mediated inflammatory diseases (IMIDs), such therapies also offer unrivalled opportunities to study the underlying immunopathological basis of these conditions.In this review, we explore recent approaches to the treatment of IMIDs and the insights to pathobiology that they provide. We review novel biologic agents targeting the T-helper 17 axis, including therapies directed towards interleukin (IL)-17 (secukinumab, ixekizumab, bimekizumab), IL-17R (brodalumab), IL-12/23p40 (ustekinumab, briakinumab) and IL-23p19 (guselkumab, tildrakizumab, brazikumab, risankizumab, mirikizumab). We also present an overview of biologics active against type I and II interferons, including sifalumumab, rontalizumab, anifrolumab and fontolizumab. Emerging strategies to interfere with cellular adhesion processes involved in lymphocyte recruitment are discussed, including both integrin blockade (natalizumab, vedolizumab, etrolizumab) and sphingosine-1-phosphate receptor inhibition (fingolimod, ozanimod). We summarise the development and recent application of Janus kinase (JAK) inhibitors in the treatment of IMIDs, including first-generation pan-JAK inhibitors (tofacitinib, baricitinib, ruxolitinib, peficitinib) and second-generation selective JAK inhibitors (decernotinib, filgotinib, upadacitinib). New biologics targeting B-cells (including ocrelizumab, veltuzumab, tabalumab and atacicept) and the development of novel strategies for regulatory T-cell modulation (including low-dose IL-2 therapy and Tregitopes) are also discussed. Finally, we explore recent biotechnological advances such as the development of bispecific antibodies (ABT-122, COVA322), and their application to the treatment of IMIDs.

Two separate effects contribute to regulatory T cell defect in systemic lupus erythematosus patients and their unaffected relatives.

SummaryForkhead box P3 (FoxP3)+ regulatory T cells (Tregs) are functionally deficient in systemic lupus erythematosus (SLE), characterized by reduced surface CD25 [the interleukin (IL)‐2 receptor alpha chain]. Low‐dose IL‐2 therapy is a promising current approach to correct this defect. To elucidate the origins of the SLE Treg phenotype, we studied its role through developmentally defined regulatory T cell (Treg) subsets in 45 SLE patients, 103 SLE‐unaffected first‐degree relatives and 61 unrelated healthy control subjects, and genetic association with the CD25‐encoding IL2RA locus. We identified two separate, uncorrelated effects contributing to Treg CD25. (1) SLE patients and unaffected relatives remarkably shared CD25 reduction versus controls, particularly in the developmentally earliest CD4+FoxP3+CD45RO–CD31+ recent thymic emigrant Tregs. This first component effect influenced the proportions of circulating CD4+FoxP3highCD45RO+ activated Tregs. (2) In contrast, patients and unaffected relatives differed sharply in their activated Treg CD25 state: while relatives as control subjects up‐regulated CD25 strongly in these cells during differentiation from naive Tregs, SLE patients specifically failed to do so. This CD25 up‐regulation depended upon IL2RA genetic variation and was related functionally to the proliferation of activated Tregs, but not to their circulating numbers. Both effects were found related to T cell IL‐2 production. Our results point to (1) a heritable, intrathymic mechanism responsible for reduced CD25 on early Tregs and decreased activation capacity in an extended risk population, which can be compensated by (2) functionally independent CD25 up‐regulation upon peripheral Treg activation that is selectively deficient in patients. We expect that Treg‐directed therapies can be monitored more effectively when taking this distinction into account.

Low-dose IL-2 therapy - a complex scenario that remains to be further explored.

Low-dose IL-2 therapy - a complex scenario that remains to be further explored.

Low-dose IL-2 selectively activates subsets of CD4+ Tregs and NK cells.

CD4+ regulatory T cells (CD4Tregs) play a critical role in the maintenance of immune tolerance and prevention of chronic graft-versus-host disease (GVHD) after allogeneic hematopoietic stem cell transplantation. IL-2 supports the proliferation and survival of CD4Tregs and previous studies have demonstrated that IL-2 induces selective expansion of CD4Tregs and improves clinical manifestations of chronic GVHD. However, mechanisms for selective activation of CD4Tregs and the effects of low-dose IL-2 on other immune cells are not well understood. Using mass cytometry, we demonstrate that low concentrations of IL-2 selectively induce STAT5 phosphorylation in Helios+ CD4Tregs and CD56brightCD16- NK cells in vitro. Preferential activation and expansion of Helios+ CD4Tregs and CD56brightCD16- NK cells was also demonstrated in patients with chronic GVHD receiving low-dose IL-2. With prolonged IL-2 treatment for 48 weeks, phenotypic changes were also observed in Helios- CD4Tregs. The effects of low-dose IL-2 therapy on conventional CD4+ T cells and CD8+ T cells were limited to increased expression of PD-1 on effector memory T cells. These studies reveal the selective effects of low-dose IL-2 therapy on Helios+ CD4Tregs and CD56bright NK cells that constitutively express high-affinity IL-2 receptors as well as the indirect effects of prolonged exposure to low concentrations of IL-2 in vivo.

Clinical trials: The rise of IL-2 therapy - a novel biologic treatment for SLE.

An unmet need exists for more-effective and selective therapeutics in systemic lupus erythematosus. Advances in understanding of the pathogenetic mechanisms of this severe autoimmune disease have led to the clinical translation of low-dose IL-2 therapy, which primarily aims to restore the activity of regulatory T cells.

Promoting Immune Regulation in Type 1 Diabetes Using Low-Dose Interleukin-2.

Dysregulation of the immune system contributes to the breakdown of immune regulation, leading to autoimmune diseases, such as type 1 diabetes (T1D). Current therapies for T1D include daily insulin, due to pancreatic β-cell destruction to maintain blood glucose levels, suppressive immunotherapy to decrease the symptoms associated with autoimmunity, and islet transplantation. Genetic risks for T1D have been linked to IL-2 and IL-2R signaling pathways that lead to the breakdown of self-tolerance mechanisms, primarily through altered regulatory T cell (Treg) function and homeostasis. In attempt to correct such deficits, therapeutic administration of IL-2 at low doses has gained attention due to the capacity to boost Tregs without the unwanted stimulation of effector T cells. Preclinical and clinical studies utilizing low-dose IL-2 have shown promising results to expand Tregs due to their high selective sensitivity to respond to IL-2. These results suggest that low-dose IL-2 therapy represents a new class of immunotherapy for T1D by promoting immune regulation rather than broadly suppressing unwanted and beneficial immune responses.

Therapeutic potential of low-dose IL-2 in a chronic GVHD patient by in vivo expansion of regulatory T cells

Chronic graft-versus-host disease (cGVHD) is a common complication following allogeneic hematopoietic stem cell transplantation (HSCT), which is characterized by autoimmune like inflammatory responses and reduced levels of regulatory T cells (Tregs). Recently, the use of low-dose IL-2 has been reported to selectively increase Tregs and therefore facilitate immune regulation and promote clinical improvements in cGVHD patients. In this report, we describe the case of a cGVHD patient who was treated with daily low-dose IL-2 therapy. Our observations demonstrate that low-dose IL-2 could induce significant expansion of Tregs in vivo leading to improved Treg/Th17 ratios. The patient showed moderate clinical benefits suggesting that multiple factors may be involved in the immunological responses. Therefore, while the therapeutic potential of low-dose IL-2 is promising, strategic approaches may be needed to induce a clinically significant and sustained Treg effect.

In this issue

ORIGINAL ARTICLE Androgen deprivation therapy accompanied by loss of cognitive function ORIGINAL ARTICLE Post-operative chemotherapy for gastric cancer improves survival ORIGINAL ARTICLE Platelet-lymphocyte ratio serves as good prognosis factor for renal cell carcinoma ORIGINAL ARTICLE High-volume hospitals have better adherence to breast cancer quality core indicators ORIGINAL ARTICLE Single agent chemotherapy and low-dose IL-2 therapy for advanced melanoma

Low-dose interleukin-2 selectively corrects regulatory T cell defects in patients with systemic lupus erythematosus

ObjectivesDefects in regulatory T cell (Treg) biology have been associated with human systemic autoimmune diseases, such as systemic lupus erythematosus (SLE). However, the origin of such Treg defects and their...

Enhanced Expression of PD-1 Modulates CD4+Foxp3+ Regulatory T Cell Homeostasis during Low-Dose IL-2 Therapy in Patients with Chronic Graft-Versus-Host Disease

CD4+Foxp3+ regulatory T cells (Treg) play a central role in the maintenance of tolerance after allogeneic hematopoietic stem cell transplantation (HSCT). We previously reported that low-dose IL-2 administration preferentially increased Treg in patients with active cGVHD and resulted in clinical improvement with only minor toxicities (NEJM 2011). In the clinical trial, IL-2 induced selective and rapid proliferation of Treg in the first week of therapy but proliferation subsequently returned to baseline levels despite continued daily administration of IL-2 (Matsuoka et al. Sci Trans Med 2013). Mechanisms that limit Treg proliferation may play an important role in Treg homeostasis as continuous high-level proliferation may increase Treg susceptibility to apoptosis resulting in overall reduction of the Treg population (Matsuoka et al. JCI 2010). To examine mechanisms for negative regulation of Treg proliferation we examined expression of Programed Death-1 (PD-1) on Treg during IL-2 therapy. Serial blood samples from 14 patients who received daily subcutaneous IL-2 (3x105-3x106IU/m2/day) for 8 weeks were studied before and at 1, 2, 4, 6, 8, 10 and 12 weeks after starting IL-2. Treg were compared to conventional CD4+Foxp3- T cells (Tcon) within individual patient samples and examined for expression of PD-1. Treg and Tcon were further divided into subpopulations by the expression of CD45RA. Before IL-2 therapy, both CD45RA+ naïve Treg and Tcon showed little expression of PD-1 (%PD-1+ cells; median 2.1%, 1.8%, respectively). However, both CD45RA- activated/memory Treg and Tcon showed significantly higher expression of PD-1 than their naïve counterparts (%PD-1+ cells: median 22%, p<0.0001; median 19%, p<0.0001, respectively) and there was no significant difference in PD-1 expression between CD45RA- Treg and Tcon. After starting IL-2, expression of PD-1 rapidly increased, mainly on the CD45RA- activated/memory Treg subpopulation and this was sustained during 8 weeks of IL-2 therapy (%PD-1+ Treg; median 38.7% at 4 weeks, p<0.002 vs baseline). In contrast, Tcon PD-1 expression did not change during IL-2 therapy. To confirm the inhibitory function of PD-1 on Treg in patients receiving IL-2, we purified Treg and Tcon by cell-sorting, labeled cells with CFSE and cultured each subset separately with or without blocking anti-PD-L1 antibody, in the presence of anti-CD3 and anti-CD28 stimulation for 4 days. Treg obtained during IL-2 therapy showed resistance to in vitro proliferation, but vigorous proliferation was regained in the presence of anti-PD-L1 mAb. In contrast the effect of PD-L1 blockade on Tcon was relatively small. These data suggest that the PD-1 selectively limits Treg proliferation during IL-2 therapy. Based on these findings, we explored the possibility of a novel immune strategy to enhance Treg expansion during low-dose IL-2 by combination with PD-1 blockade using a murine BMT model. Lethally irradiated B6D2F1 mice were transplanted with 1x106 spleen cells from the control B6 mice together with 5x106 TCD-BM from either PD-1 KO B6 or control B6 donors. Recipients were treated with 5x103 IU IL-2 or control vehicle from day 35 to 49. As expected, recipients transplanted with cells from control donors showed significantly higher expression of PD-1 on Treg than Tcon when treated with IL-2 (%PD-1+ cells; median 47.2%, 8.9%, respectively, p<0.0001) and the increase of Treg after IL-2 treatment was more evident in recipients transplanted from PD-1 KO donors (p<0.05). To examine this clinically, we tested whether anti-PD-1 mAb can boost Treg proliferation during IL-2 administration and we confirmed that IL-2 induced Treg proliferation was significantly enhanced with the combined use of anti-PD-1 antibody (%Ki-67 + cells; median 22.9% vs 33.2%, p<0.05). In conclusion, these findings indicate that the self-regulation of Treg homeostasis through the PD-1/PD-L1 pathway can limit the expansion of Treg mediated by exogenously administered IL-2. Blockade of PD-1/PD-L1 pathway may provide an opportunity for in vivo manipulation of Treg homeostasis. Our data provide important information for developing therapeutic strategies to modulate Treg homeostasis in vivo to promote immune tolerance. DisclosuresNo relevant conflicts of interest to declare.

SP0189 Induction of Remission by Low-Dose IL-2-Therapy in One SLE Patient with Increased Disease Activity Refractory to Standard Therapies

IL-2 deficiency and associated regulatory T cell (Treg) defects critically contribute to SLE pathogenesis. In our previous translational work we proved the efficacy and safety of a low-dose IL-2 therapy...

Evaluation of IL-2 therapy on human immune system homeostasis in humanized mice (LYM8P.731)

Abstract Regulatory T cells (Treg) are an IL-2 dependent subset of CD4 T cells with the capacity to suppress immune responses. In mice, IL-2 treatment can prevent autoimmune disease and rejection of allogeneic tissues by selective expansion of Treg populations. Moreover clinical trials have shown that low dose IL-2 therapy increases Treg in humans and is effective in ameliorating immune disorders. However, low dose IL-2/rapamycin therapy in type 1 diabetic individuals was less effective and had potentially detrimental effects on beta cell function. The unpredictability of IL-2 therapy in humans emphasizes the need for novel models to fully evaluate therapies targeting human Treg before being used in the clinic. Here we have evaluated the impact of IL-2 treatment on human immune systems using a humanized mouse model. For these studies we used NOD-scid IL2rγnull (NSG) mice engrafted with fetal thymus and liver tissues and human HSC [NSG-BLT (bone marrow, liver, thymus) mice]. Human T cell populations develop efficiently in NSG-BLT mice making this model ideal to study T cell specific therapies. NSG-BLT mice treated with an AAV vector expressing human IL-2 showed a significant increase in the number of both functional human Tregs and human NK cells. IL-2 expression did not alter T effector/memory T cells subsets. Collectively, these data show that humanized mouse models are an ideal platform for testing human-specific immune therapies.

A3.11 Induction of remission by low-dose IL-2-therapy in one SLE patient with increased disease activity refractory to standard therapies: A case report

IL-2 deficiency and associated regulatory T cell (Treg) defects contribute essentially to SLE pathogenesis. In our previous translational work we proved the efficacy and safety of a low-dose IL-2 therapy...

Preactivation with IL-12, IL-15, and IL-18 Induces CD25 and a Functional High-Affinity IL-2 Receptor on Human Cytokine-Induced Memory-like Natural Killer Cells

Natural killer (NK) cells are effector lymphocytes that are under clinical investigation for the adoptive immunotherapy of hematologic malignancies, especially acute myeloid leukemia. Recent work in mice has identified innate memory-like properties of NK cells. Human NK cells also exhibit memory-like properties, and cytokine-induced memory-like (CIML) NK cells are generated via brief preactivation with IL-12, IL-15, and IL-18, which later exhibit enhanced functionality upon restimulation. However, the optimal cytokine receptors and signals for maintenance of enhanced function and homeostasis after preactivation remain unclear. Here, we show that IL-12, IL-15, and IL-18 preactivation induces a rapid and prolonged expression of CD25, resulting in a functional high-affinity IL-2 receptor (IL-2Rαβγ) that confers responsiveness to picomolar concentrations of IL-2. The expression of CD25 correlated with STAT5 phosphorylation in response to picomolar concentrations of IL-2, indicating the presence of a signal-competent IL-2Rαβγ. Furthermore, picomolar concentrations of IL-2 acted synergistically with IL-12 to costimulate IFN-γ production by preactivated NK cells, an effect that was CD25 dependent. Picomolar concentrations of IL-2 also enhanced NK cell proliferation and cytotoxicity via the IL-2Rαβγ. Further, after adoptive transfer into immunodeficient NOD-SCID-γc−/− mice, human cytokine–preactivated NK cells expand preferentially in response to exogenous IL-2. Collectively, these data demonstrate that human CIML NK cells respond to IL-2 via IL-2Rαβγ with enhanced survival and functionality, and they provide additional rationale for immunotherapeutic strategies that include brief cytokine preactivation before adoptive NK cell transfer, followed by low-dose IL-2 therapy.

Highlights from Recent Cancer Literature

Highlights from Recent Cancer Literature

Cytokine activation induces CD25 expression and a functional high-affinity IL-2 receptor on CD56dim human NK Cells (P4349)

Abstract The heterotrimeric high affinity IL-2 receptor (IL-2Rαβγ) is expressed on CD56bright human NK cells and confers responsiveness to picomolar concentrations of IL-2. In contrast, resting CD56dim NK cells lack IL-2Rα (CD25), but constitutively express the intermediate affinity IL-2Rβγ chains. Here, we show that cytokine-activation induces rapid and prolonged expression of CD25 on CD56dim NK cells, especially the combination of IL-15 plus IL-18. This expression of CD25 correlated with STAT5 phosphorylation in response to picomolar concentrations of IL-2, indicating the presence of a signal-competent IL-2Rαβγ. Furthermore, picomolar concentrations of IL-2 acted synergistically with IL-12 to co-stimulate IFN-γ production by pre-activated CD56dim NK cells. Similarly, low dose IL-2 enhanced the cytotoxicity of pre-activated CD56dim NK cells against K562 tumor targets. Both effects were dependent on the expression of CD25. Preliminary experiments also suggest that the induction of CD25 on CD56dim NK cells enhances proliferative capacity and survival in cultures supplemented with low dose IL-2. Since CD56dim NK cells represent the major subset of human peripheral blood NK cells, these data support a rationale for immunotherapeutic strategies that include cytokine pre-activation prior to adoptive NK cell transfer, followed by low dose IL-2 therapy.

Human regulatory T cells are hyper-responsive to low levels of IL-2 (P5156)

Abstract Our recent work demonstrates that weak IL-2R signaling supports the development and homeostasis of mouse Treg cells. This finding provides a conceptual framework for the use of low dose IL-2 in immunotherapy to selectively promote Treg cells for tolerance induction. To begin to examine the extent that low dose IL-2 may selectively activate human Treg cells, we assessed IL-2-dependent tyrosine-phosphorylation of STAT5 (pSTAT5) in various populations of IL-2R-bearing human lymphocytes. Dose-response studies indicate that Treg cells are 50-100 fold more responsive to IL-2 for pSTAT5 activation than CD4 T memory and T effector (Teff) cells. Relative high levels of high affinity IL-2Rs on Treg cells provide a partial explanation for this enhanced signaling sensitivity to IL-2. However, other factors are also clearly involved in this response because in vitro-derived CD4 Teff cells express much higher levels of CD25, CD122, and CD132 than Treg cells, but these Teff cells remain much less responsive to IL-2 when compared to Treg cells. This finding indicates that human Treg cells utilize a cell intrinsic mechanism to amplify IL-2R signaling when IL-2 is limiting. Overall these studies provide an explanation for the apparent safety of low dose IL-2 therapy for patients with autoimmune conditions where Treg cells were enhanced without re-activation of autoreactive T cells.

Gastric Cancer Immunotherapy: An Overview

Gastric adenocarcinoma is the third most common cancer and the second most common cause of death due to cancer worldwide. Surgery is still the major prognostic factor for gastric cancer. Patients who could not be resected have a poor prognosis with survival ranging from 3 to 11 months. There is evidence that surgical operations can cause a variety of immunological disturbances in man both in vivo and in vitro. The postoperative changes in the systemic immune response are proportional to the degree of surgical trauma leading to a generalized state of immunosuppression, which is implicated in the development of septic complications and provided a “fertile soil” for tumor cell metastasis. Immunotherapy may be a potentially promising alternative strategy for gastric cancer. In early clinical trials, systemic immunotherapy included both active vaccination directed against defined tumor-associated antigens expressed in gastric carcinoma cells and passive administration of IL-2 with some evidence of regression of metastatic gastric cancer. Other studies have applied immunotherapy in the adjuvant setting with equally promising results. For example, OK-432, a streptococcal preparation, demonstrated marginal improvement in survival for patients with stage III gastric cancer and a meta-analysis of centrally randomized controlled clinical trials indicated a significant survival benefit with combination OK-432 and chemotherapy compared to chemotherapy alone (p 0.05). Additional data suggesting a biological and clinical benefit of subcutaneous, preoperative administration of low-dose IL-2 in colon cancer encouraged us to evaluate low-dose IL-2 therapy in the neoadjuvant setting for patients with gastric adenocarcinoma who undergo surgery and to evaluate its effects on systemic and tumor infiltrating lymphocyte numbers. We also sought to determine if neoadjuvant low-dose IL-2 could influence the clinical outcome for patients undergoing gastric resection for cancer. We report the biological, histological and clinical results with the full accrual of patients and a median follow-up of 51 months.

Low-Dose IL-2 for In Vivo Expansion of CD4+ and CD8+ Regulatory T Cells in Nonhuman Primates

IL-2 is a known potent T cell growth factor that amplifies lymphocyte responses in vivo. This capacity has led to the use of high-dose IL-2 to enhance T cell immunity in patients with AIDS or cancer. However, more recent studies have indicated that IL-2 is also critical for the development and peripheral expansion of regulatory T cells (Tregs). In the current study, low-dose IL-2 (1 million IU/m(2) BSA/day) was administered to expand Tregs in vivo in naïve nonhuman primates. Our study demonstrated that low-dose IL-2 therapy significantly expanded peripheral blood CD4(+) and CD8(+) Tregs in vivo with limited expansion of non-Treg cells. These expanded Tregs are mainly CD45RA(-) Foxp3(high) activated Tregs and demonstrated potent immunosuppressive function in vitro. The results of this preclinical study can serve as a basis to develop Treg immunotherapy, which has significant therapeutic potential in organ/cellular transplantation.