Regulatory T-cell responses to low-dose interleukin-2 in HCV-induced vasculitis

Application of IL-2 therapy to target T regulatory cell function

Interleukin-2 (IL-2) was originally discovered as a growth factor for activated T cells in vitro. IL-2 promotes CD8(+) T cell growth and differentiation in vivo, but has little effect on CD4(+) T cell function. Regulatory T cells (Treg cells) express all three chains (CD25, CD122, and CD132) of the IL-2 receptor complex and are dependent on IL-2 for survival and function. Exogenous IL-2 can augment Treg cell numbers in vivo and may have therapeutic value in the treatment of autoimmune and inflammatory diseases. Complexes of IL-2 with different IL-2 antibodies can target delivery to cells expressing all three receptor chains (Treg cells and activated T effector cells) or to cells expressing just CD122 and CD132 (NK cells and memory phenotype CD8(+) T cells).

IL-2: fine-tuning the germinal center reaction

T follicular cells help B cells to drive germinal center formation. In this issue of Immunity, Ballesteros-Tato et al. (2012) demonstrate that high amounts of interleukin-2 inhibit production of this critical T effector subset.

Immunotherapy in autoimmune type 1 diabetes

Type 1 diabetes (T1D) is a chronic autoimmune disease affecting millions of people worldwide. The disease is characterized by the loss of self-tolerance to the insulin-producing β-cells in the pancreas, the destruction of β-cells, and finally the development of chronic hyperglycemia at diagnosis of T1D. Its incidence and prevalence are rising dramatically, highlighting the need for immunotherapeutic strategies able to prevent or treat the disease in a safe and specific manner. Immunotherapeutic strategies are being developed, and aim to restore immunological self-tolerance, thereby limiting unwanted immunity and β-cell destruction. Foxp3+ regulatory T (Treg) cells exert essential functions to maintain and restore immunological self-tolerance. The identification of the transcription factor Foxp3 as the specification factor for the Treg cell lineage facilitated our understanding in the biology of Treg generation and function. This review highlights the current understanding of immunotherapeutic approaches as preventative and curative measures for autoimmune T1D. It includes an overview on early immunointervention studies, which made use of general immunosuppressive agents such as cyclosporin A, followed by a discussion on newly emerging clinical trials. Besides non-antigen-specific therapies, particular attention is given to antigen-specific generation of Foxp3+ Treg cells and their potential use to limit autoimmunity such as T1D.

Hepatitis C virus infection, mixed cryoglobulinemia, and kidney disease

Hepatitis C virus (HCV) may instigate mixed cryoglobulinemia; the most significant accompanying kidney lesion is type I membranoproliferative glomerulonephritis, usually occurring in the context of type II mixed cryoglobulinemia. Additionally, recent data support a link between HCV infection and proteinuria in population-based studies, raising the possibility that kidney diseases associated with HCV may be more common than previously thought. A number of strategies have been used to treat HCV-related glomerulonephritis, including antiviral agents, immunosuppressive therapies such as corticosteroids and cytotoxic agents, and plasma exchange. Limited but encouraging data about the utility of antiviral treatment in the setting of HCV-associated glomerulonephritis exist, with one pooled analysis noting a sustained viral response of 42%, albeit with significant heterogeneity. Immunosuppressive therapy may be most useful for cryoglobulinemic kidney disease, with individualized approaches considered for the treatment of HCV-associated cryoglobulinemic glomerulonephritis based on the level of proteinuria and kidney failure. Of note, rituximab, a chimeric monoclonal antibody that blocks CD20 receptors on B cells, has been reported to be effective for the treatment of mixed cryoglobulinemia symptoms, including glomerulonephritis.

Regulatory T cells in HIV infection: can immunotherapy regulate the regulator?

Regulatory T cells (Tregs) have a dominant role in self-tolerance and control of autoimmune diseases. These cells also play a pivotal role in chronic viral infections and cancer by limiting immune activation and specific immune response. The role of Tregs in HIV pathogenesis remains poorly understood as their function, changes according to the phases of infection. Tregs can suppress anti-HIV specific responses and conversely can have a beneficial role by reducing the deleterious impact of immune activation. We review the frequency, function and homing potential of Tregs in the blood and lymphoid tissues as well as their interaction with dendritic cells in the context of HIV infection. We also examine the new insights generated by recombinant IL-2 and IL-7 clinical trials in HIV-infected adults, including the immunomodulatory effects of Tregs. Based on their detrimental role in limiting anti-HIV responses, we propose Tregs as potential targets for immunotherapeutic strategies aimed at decreasing Tregs frequency and/or immunosuppressive function. However, such approaches require a better understanding of the time upon infection when interfering with Treg function may not cause a deleterious state of hyperimmune activation.

From IL-2 to IL-37: the expanding spectrum of anti-inflammatory cytokines

Feedback regulatory circuits provided by regulatory T cells (T(reg) cells) and suppressive cytokines are an intrinsic part of the immune system, along with effector functions. Here we discuss some of the regulatory cytokines that have evolved to permit tolerance to components of self as well as the eradication of pathogens with minimal collateral damage to the host. Interleukin 2 (IL-2), IL-10 and transforming growth factor-β (TGF-β) are well characterized, whereas IL-27, IL-35 and IL-37 represent newcomers to the spectrum of anti-inflammatory cytokines. We also emphasize how information accumulated through in vitro as well as in vivo studies of genetically engineered mice can help in the understanding and treatment of human diseases.

Differential effects of IL-12 on Tregs and non-Treg T cells: roles of IFN-γ, IL-2 and IL-2R

Complex interactions between effector T cells and Foxp3⁺ regulatory T cells (Treg) contribute to clinical outcomes in cancer, and autoimmune and infectious diseases. Previous work showed that IL-12 reversed Treg-mediated suppression of CD4⁺Foxp3⁻ T cell (Tconv) proliferation. We and others have also shown that Tregs express T-bet and IFN-γ at sites of Th1 inflammation and that IL-12 induces IFN-γ production by Tregs in vitro. To investigate whether loss of immunosuppression occurs when IFN-γ is expressed by Tregs we treated mouse lymphocyte cultures with IL-12. IFN-γ expression did not decrease the ability of Tregs to suppress Tconv proliferation. Rather, IL-12 treatment decreased Treg frequency and Foxp3 levels in Tregs. We further showed that IL-12 increased IL-2R expression on Tconv and CD8 T cells, diminished its expression on Tregs and decreased IL-2 production by Tconv and CD8 T cells. Together, these IL-12 mediated changes favored the outgrowth of non-Tregs. Additionally, we showed that treatment with a second cytokine, IL-27, decreased IL-2 expression without augmenting Tconv and CD8 T cell proliferation. Notably, IL-27 only slightly modified levels of IL-2R on non-Treg T cells. Together, these results show that IL-12 has multiple effects that modify the balance between Tregs and non-Tregs and support an important role for relative levels of IL-2R but not for IFN-γ expression in IL-12-mediated reversal of Treg immunosuppression.

Increased IL-17A expression in temporal artery lesions is a predictor of sustained response to glucocorticoid treatment in patients with giant-cell arteritis

BACKGROUND

Interleukin 17A (IL-17A) exerts pivotal proinflammatory functions in chronic inflammatory and autoimmune diseases.

OBJECTIVE

To investigate IL-17A expression in temporal artery lesions from patients with giant-cell arteritis (GCA), and its relationship with disease outcome.

METHODS

Fifty-seven patients with biopsy-proven GCA were prospectively evaluated, treated and followed for 4.5 years (52-464 weeks). Relapses, time (weeks) required to achieve a maintenance prednisone dose <10 mg/day, and time (weeks) to complete prednisone withdrawal were prospectively recorded. IL-17A mRNA was measured by real-time quantitative RT-PCR in temporal arteries from all patients and 19 controls. IL-17 protein expression was assessed by immunohistochemistry/immunofluorescence.

RESULTS

IL-17A expression was significantly increased in temporal artery samples from GCA patients compared with controls (6.22±8.61 vs 2.50±3.9 relative units, p=0.016). Surprisingly, patients with strong IL-17A expression tended to experience less relapses, and required significantly shorter treatment periods (median 25 vs 44 weeks to achieve <10 mg prednisone/day, p=0.0079). There was no correlation between IL-17A and RORc or RORα expression suggesting that these transcription factors may not exclusively reflect Th17 differentiation, and that cells other than Th17 cells might contribute to IL-17 expression in active patients. Accordingly, FoxP3(+)IL-17A(+) cells were identified in lesions by confocal microscopy and were dramatically reduced in specimens from treated patients.

CONCLUSIONS

IL-17A expression is increased in GCA lesions, and is a predictor of response to glucocorticoid treatment. The contribution of FoxP3+ cells to IL-17A production in untreated patients suggests that induced-Tregs may facilitate disease remission when proinflammatory cytokine production is downregulated by glucocorticosteroids.

The dual roles of inflammatory cytokines and chemokines in the regulation of autoimmune diseases and their clinical implications

Cytokines and chemokines are secreted, small cell-signaling protein molecules, whose receptors are expressed on immune cells. These factors play a critical role in immune cell differentiation, migration, and polarization into functional subtypes and in directing their biological functions. Much attention has been devoted to exploring the role of key inflammatory cytokines and promigratory chemokines in autoimmune, autoinflammatory, and allergic diseases, leading to development of therapeutic strategies that are based on their targeted neutralization. Recent studies, including those coming from our groups, show that several major proinflammatory cytokines and chemokines, including IFN-γ, IL-2, CCL2, and CXCL12, may also function as anti-inflammatory mediators and therefore, may have potential as anti-inflammatory drugs. Likewise, major anti-inflammatory mediators, such as TGF-β, may under certain conditions, in combination with other cytokines, exhibit proinflammatory function and direct the polarization of the highly inflammatory CD4(+) Th17 cells. We show here that the biological function of pro- and anti-inflammatory cytokines is dependent on three key parameters: the local concentration of a given cytokine, the stage of disease in which it is administered, and its combination with other cytokines. The therapeutic implications of these findings are discussed, including two very recent studies summarizing clinical trials, in which low-dose administration of IL-2 was used to successfully suppress HCV and GVHD.

Rapamycin/IL-2 combination therapy in patients with type 1 diabetes augments Tregs yet transiently impairs β-cell function

Rapamycin/interleukin-2 (IL-2) combination treatment of NOD mice effectively treats autoimmune diabetes. We performed a phase 1 clinical trial to test the safety and immunologic effects of rapamycin/IL-2 combination therapy in type 1 diabetic (T1D) patients. Nine T1D subjects were treated with 2-4 mg/day rapamycin orally for 3 months and 4.5 × 10(6) IU IL-2 s.c. three times per week for 1 month. β-Cell function was monitored by measuring C-peptide. Immunologic changes were monitored using flow cytometry and serum analyses. Regulatory T cells (Tregs) increased within the first month of therapy, yet clinical and metabolic data demonstrated a transient worsening in all subjects. The increase in Tregs was transient, paralleling IL-2 treatment, whereas the response of Tregs to IL-2, as measured by STAT5 phosphorylation, increased and persisted after treatment. No differences were observed in effector T-cell subset frequencies, but an increase in natural killer cells and eosinophils occurred with IL-2 therapy. Rapamycin/IL-2 therapy, as given in this phase 1 study, resulted in transient β-cell dysfunction despite an increase in Tregs. Such results highlight the difficulties in translating therapies to the clinic and emphasize the importance of broadly interrogating the immune system to evaluate the effects of therapy.

CTLA4-Ig restores rejection of MHC class-II mismatched allografts by disabling IL-2-expanded regulatory T cells

Allograft acceptance and tolerance can be achieved by different approaches including inhibition of effector T cell responses through CD28-dependent costimulatory blockade and induction of peripheral regulatory T cells (Tregs). The observation that Tregs rely upon CD28-dependent signals for development and peripheral expansion, raises the intriguing possibility of a counterproductive consequence of CTLA4-Ig administration on tolerance induction. We have investigated the possible negative effect of CTLA4-Ig on Treg-mediated tolerance induction using a mouse model of single MHC class II-mismatched skin grafts in which long-term acceptance was achieved by short-term administration of IL-2/anti-IL-2 complex. CTLA4-Ig treatment was found to abolish Treg-dependent acceptance in this model, restoring skin allograft rejection and Th1 alloreactivity. CTLA4-Ig inhibited IL-2-driven Treg expansion, and prevented in particular the occurrence of ICOS(+) Tregs endowed with potent suppressive capacities. Restoring CD28 signaling was sufficient to counteract the deleterious effect of CTLA4-Ig on Treg expansion and functionality, in keeping with the hypothesis that costimulatory blockade inhibits Treg expansion and function by limiting the delivery of essential CD28-dependent signals. Inhibition of regulatory T cell function should therefore be taken into account when designing tolerance protocols based on costimulatory blockade.

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.

Calcium/calmodulin-dependent protein kinase IV suppresses IL-2 production and regulatory T cell activity in lupus

The activity of calcium/calmodulin-dependent protein kinase IV (CaMK4) is increased in T cells from patients with systemic lupus erythematosus (SLE) and has been shown to reduce IL-2 production by promoting the effect of the transcriptional repressor cAMP responsive element modulator-α on the IL2 promoter. In this article, we demonstrate that T cells from MRL/lpr mice display increased levels of CaMK4 in the nucleus, and that genetic deletion of Camk4 results in improved survival. We demonstrate that absence of CaMK4 restores IL-2 production, curbs increased T cell activation, and augments the number and activity of regulatory T cells. Analogously, silencing of CaMK4 in T cells from patients with SLE increases the expression of FoxP3 on stimulation in the presence of TGF-β. Our results demonstrate the importance of the serine/threonine kinase CaMK4 in the generation and function of regulatory T cells in patients with SLE and lupus-prone mice, and its potential to serve as a therapeutic target.

The place of immunotherapy in the management of HCV-induced vasculitis: an update

Patients with chronic hepatitis C virus (HCV) can develop systemic cryoglobulinemic vasculitis. Combination of pegylated-interferon α and ribavirin is the first-line treatment of this condition. However, in case of severe or life-threatening manifestations, absence of a virological response, or autonomized vasculitis, immunotherapy (alone or in addition to the antiviral regimen) is necessary. Rituximab is to date the only biologic with a sufficient level of evidence to support its use in this indication. Several studies have demonstrated that rituximab is highly effective when cryoglobulinaemic vasculitis is refractory to antiviral regimen, that association of rituximab with antiviral regimen may induce a better and faster clinical remission, and, recently, that rituximab is more efficient than traditional immunosuppressive treatments. Some issues with regard to the optimal dose of rituximab or its use as maintenance treatment remain unsolved. Interestingly, in balance with this anti-inflammatory strategy, a recent pilot study reported the significant expansion of circulating regulatory T lymphocytes with concomitant clinical improvement in patients with refractory HCV-induced cryoglobulinaemic vasculitis using low dose of subcutaneous interleukin-2. This paper provides an updated overview on the place of immunotherapy, especially biologics, in the management of HCV-induced cryoglobulinaemic vasculitis.

The 20th anniversary of interleukin-2 therapy: bimodal role explaining longstanding random induction of complete clinical responses

Background

This year marks the twentieth anniversary of the approval by the US Food and Drug Administration of interleukin-2 (IL2) for use in cancer therapy, initially for renal cell carcinoma and later for melanoma. IL2 therapy for cancer has stood the test of time, with continued widespread use in Europe, parts of Asia, and the US. Clinical complete responses are variably reported at 5%–20% for advanced malignant melanoma and renal cell carcinoma, with strong durable responses and sustained long-term 5–10-year survival being typical if complete responses are generated.

Methods

The literature was reviewed for the actions and clinical effects of IL2 on subsets of T cells. The influence of IL2 on clinical efficacy was also sought.

Results

The review revealed that IL2 is capable of stimulating different populations of T cells in humans to induce either T effector or T regulatory responses. This apparent “functional paradox” has confounded a clear understanding of the mechanisms behind the clinical effects that are observed during and following administration of IL2 therapy. An average complete response rate of around 7% in small and large clinical trials using IL2 for advanced renal cell carcinoma and malignant melanoma has been shown from a recent review of the literature.

Conclusion

This review considers the published literature concerning the actions and emerging clinical effects of IL2 therapy, spanning its 20-year period in clinical use. It further details some of the recently described “bimodal” effects of IL2 to explain the apparent functional paradox, and how IL2 might be harnessed to emerge rapidly as a much more effective and predictable clinical agent in the near future.

Autoimmune manifestations in viral hepatitis

Infections by the viruses responsible for hepatitis B, C and D are accompanied by a number of immunopathological manifestations. A link between infection and autoimmunity is particularly well documented for the hepatitis C virus. Immunopathological manifestations range from production of autoantibodies to overt autoimmune disease, including thyroiditis and autoimmune hepatitis, and to immune-complex-mediated disorders, including cryoglobulinaemia, glomerulonephritis and vasculitis. Several of these manifestations improve with successful antiviral treatment, directly incriminating the virus in their pathogenesis. Mechanisms considered responsible for hepatitis virus-related immunopathology, including molecular mimicry, impairment of regulatory T cells and activation of B lymphocytes, will be examined in this review.

Tolerogenic therapies in transplantation

Since the concept of immunologic tolerance was discovered in the 1940s, the pursuit of tolerance induction in human transplantation has led to a rapid development of pharmacologic and biologic agents. Short-term graft survival remains an all-time high, but successful withdrawal of immunosuppression to achieve operational tolerance rarely occurs outside of liver transplantation. Collaborative efforts through the NIH sponsored Immune Tolerance Network and the European Commission sponsored Reprogramming the Immune System for Establishment of Tolerance consortia have afforded researchers opportunity to evaluate the safety and efficacy of tolerogenic strategies, investigate mechanisms of tolerance, and identify molecular and genetic markers that distinguish the tolerance phenotype. In this article, we review traditional and novel approaches to inducing tolerance for organ transplantation, with an emphasis on their translation into clinical trials.

The potential of Fas ligand (apoptosis-inducing molecule) as an unconventional therapeutic target in type 1 diabetes

The development of type 1 diabetes (T1D) is driven by autoreactive T cells that attack and destroy the insulin-producing β-cells in pancreatic islets, forcing patients to take multiple daily insulin injections. Insulin therapy, however, is not a cure and diabetic patients often develop serious long-term microvascular and cardiovascular complications. Therefore, intensive efforts are being directed toward developing safe immunotherapy for the disease that does not impair host defense and preserves β-cells, leading to better glycemic control than exogenous insulin therapy. Engineering therapies that differentially cripple or tolerate autoreactive diabetogenic T cells while sparing protective T cells necessary for maintaining a competent immune system has proven challenging. Instead, recent efforts have focused on modulating or resetting the immune system through global but transient deletion of T cells or B cells using anti-CD3 or anti-CD20 mAb, respectively. However, phase III clinical trials have shown promising but modest efficacy so far with these approaches. Therefore, there is a need to identify novel biological targets that do not fit the classic properties of being involved in adaptive immune cell activation. In this prospective, we provide preclinical evidence that targeting Fas ligand (FasL) may provide a unique opportunity to prevent or cure T1D and perhaps other organ-specific autoimmune diseases without causing immune suppression. Unlike conventional targets that are involved in T and B lymphocyte activation (such as CD3 and CD20, respectively), FasL is an apoptosis-inducing surface molecule that triggers cell death by binding to Fas (also known as CD95 Apo-1). Therefore, targeting FasL is not expected to cause immune suppression, the Achilles Heel of conventional approaches. We will discuss the hypothesis that targeting FasL has unique benefits that are not offered by current immunomodulatory approaches.

Hepatitis C virus infection and mixed cryoglobulinemia

Hepatitis C virus (HCV) chronic infection is recognized as the major cause of mixed cryoglobulinemia (MC). Its persistence represents a continuous stimulus for host immune system with production of circulating immune complexes (ICs), one-third of them with cryoprecipitate property. Several factors contribute to the biological activities of ICs, many of which are not completely known. Among them, complement factors play a crucial role in the cold-insoluble ICs-mediated vasculitis, involving primarily small blood vessels in different tissues including skin, kidney, peripheral, and central nervous system. Liver represents the major target of HCV infection with inflammatory infiltrates, resembling secondary lymphoid follicles. Cytokine like CXCL13 contribute to B-cell homing in intraportal lymphoid aggregates, in which B-cell clonal selection may arise. B-cell clonal expansion starts as an antigen-driven event and expands towards indolent and malignant B-cell proliferation. Occurrence of intrahepatic B-cell clonalities correlates with extrahepatic clinical manifestations of HCV infection. In this context, cryoglobulinemic patients should be considered a peculiar HCV-infected population that needs a clinical multidisciplinary approach and more articulated therapeutic measures.

Interleukin-2 and type 1 diabetes: new therapeutic perspectives

A new sort of CD4+T cells, so-called regulatory T cells (Tregs), has been described in 1996. Tregs are suggested to have an important function consisting in controlling autoimmune reactions. In humans, absence of Tregs induces the IPEX syndrome characterized by the presence of several autoimmune diseases. These cells depend on interleukin-2 (IL-2) for proliferating and controlling the T effector cells (Teff) reaction, but they do not have the capacity to produce IL-2. In type 1 diabetes (T1DM), a hypothesis is that a lack of IL-2 in pancreas could prevent Tregs action and lead to beta cells destruction. In NOD mice, low dose IL-2 treatment at the initial time of diabetes can rescue insulin secretion by restoring proteins expression that are necessary for Tregs regulatory function in the pancreas. Using low doses instead of high doses IL-2 prevents Teff activation which also depends on IL-2. These results led to conduct a dose-effect trial in human T1DM. This trial aimed at determining the therapeutic condition, which induces Tregs activation without major side effects, in a therapeutic perspective to recover insulin secretion at the apparition of diabetes.

IL-2/IL-2Ab complexes induce regulatory T cell expansion and protect against proteinuric CKD

Regulatory T cells (Tregs) help protect against autoimmune renal injury. The use of agonist antibodies and antibody/cytokine combinations to expand Tregs in vivo may have therapeutic potential for renal disease. Here, we investigated the effects of administering IL-2/IL-2Ab complexes in mice with adriamycin nephropathy, a model of proteinuric kidney disease that resembles human focal segmental glomerulosclerosis. Injecting IL-2/IL-2Ab complexes before or, to a lesser extent, after induction of disease promoted expansion of Tregs. Furthermore, administration of this complex was renoprotective, evidenced by improved renal function, maintenance of body weight, less histologic injury, and reduced inflammation. IL-2/IL-2Ab reduced serum IL-6 and renal expression of IL-6 and IL-17 but enhanced expression of IL-10 and Foxp3 in the spleen. In vitro, the addition of IL-2/IL-2Ab complexes induced rapid STAT-5 phosphorylation in CD4 T cells. In summary, these data suggest that inducing the expansion of Tregs by administering IL-2/IL-2Ab complexes is a possible strategy to treat renal disease.

Pharmacological modulation of humoral immunity in a nonhuman primate model of AAV gene transfer for hemophilia B

Liver gene transfer for hemophilia B has shown very promising results in recent clinical studies. A potential complication of gene-based treatments for hemophilia and other inherited disorders, however, is the development of neutralizing antibodies (NAb) against the therapeutic transgene. The risk of developing NAb to the coagulation factor IX (F.IX) transgene product following adeno-associated virus (AAV)-mediated hepatic gene transfer for hemophilia is small but not absent, as formation of inhibitory antibodies to F.IX is observed in experimental animals following liver gene transfer. Thus, strategies to modulate antitransgene NAb responses are needed. Here, we used the anti-B cell monoclonal antibody rituximab (rtx) in combination with cyclosporine A (CsA) to eradicate anti-human F.IX NAb in rhesus macaques previously injected intravenously with AAV8 vectors expressing human F.IX. A short course of immunosuppression (IS) resulted in eradication of anti-F.IX NAb with restoration of plasma F.IX transgene product detection. In one animal, following IS anti-AAV6 antibodies also dropped below detection, allowing for successful AAV vector readministration and resulting in high levels (60% or normal) of F.IX transgene product in plasma. Though the number of animals is small, this study supports for the safety and efficacy of B cell-targeting therapies to eradicate NAb developed following AAV-mediated gene transfer.

Trial Watch: Adoptive cell transfer immunotherapy

During the last two decades, several approaches for the activation of the immune system against cancer have been developed. These include rather unselective maneuvers such as the systemic administration of immunostimulatory agents (e.g., interleukin-2) as well as targeted interventions, encompassing highly specific monoclonal antibodies, vaccines and cell-based therapies. Among the latter, adoptive cell transfer (ACT) involves the selection of autologous lymphocytes with antitumor activity, their expansion/activation ex vivo, and their reinfusion into the patient, often in the context of lymphodepleting regimens (to minimize endogenous immunosuppression). Such autologous cells can be isolated from tumor-infiltrating lymphocytes or generated by manipulating circulating lymphocytes for the expression of tumor-specific T-cell receptors. In addition, autologous lymphocytes can be genetically engineered to prolong their in vivo persistence, to boost antitumor responses and/or to minimize side effects. ACT has recently been shown to be associated with a consistent rate of durable regressions in melanoma and renal cell carcinoma patients and holds great promises in several other oncological settings. In this Trial Watch, we will briefly review the scientific rationale behind ACT and discuss the progress of recent clinical trials evaluating the safety and effectiveness of adoptive cell transfer as an anticancer therapy.

Stable IL-2 decision making by endogenous c-Fos amounts in peripheral memory T-helper cells

The cytokine IL-2 performs opposite functions supporting efficient immune responses and playing a key role in peripheral tolerance. Therefore, precise fine-tuning of IL-2 expression is crucial for adjusting the immune response. Combining transcription factor analysis at the single cell and the single nucleus level using flow cytometry with statistical analysis, we showed that physiological differences in the expression levels of c-Fos and NFATc2, but not of c-Jun and NF-κBp65, are limiting for the decision whether IL-2 is expressed in a strongly activated human memory T-helper (Th) cell. Variation in the expression of c-Fos leads to substantial diversity of IL-2 expression in ∼40% of the memory Th cells. The remaining cells exhibit an equally high c-Fos expression level, thereby ensuring robustness in IL-2 response within the population. These findings reveal how memory Th cells benefit from regulated variation in transcription factor expression to achieve a certain stability and variability of cytokine expression in a controlled manner.

TSLP: from allergy to vaccine adjuvant

The field of vaccine adjuvants has been an area of active research and development because of the need to improve the generation of protective immunity to a large number of pathogens, as well as in diseases such as cancer. Adjuvants can also help induce stronger immune responses with fewer injections, and consequently improve both the feasibility and success rate of large-scale population vaccine campaigns in developing countries. A current challenge is to identify vaccine adjuvants of various classes (cytokines, toll-like receptor ligands, etc.) with specific immune-modulating properties in order to tailor the immune response to certain pathological situations. In this issue, Van Roey et al. [Eur. J. Immunol. 2012. 42: 353-363] explore one of these challenges, namely to identify novel mucosal adjuvants. Van Roey et al. show that the pro-allergic cytokine thymic stromal lymphopoietin (TSLP) promotes a strong B-cell response with production of secretory IgA at mucosal sites. Here, we discuss the importance and limits of these findings within the broader field of vaccine adjuvants, and the potential development of TSLP as a mucosal and B-cell adjuvant in humans.

The role of interleukin-2 during homeostasis and activation of the immune system

Interleukin-2 (IL-2) signals influence various lymphocyte subsets during differentiation, immune responses and homeostasis. As discussed in this Review, stimulation with IL-2 is crucial for the maintenance of regulatory T (T(Reg)) cells and for the differentiation of CD4(+) T cells into defined effector T cell subsets following antigen-mediated activation. For CD8(+) T cells, IL-2 signals optimize both effector T cell generation and differentiation into memory cells. IL-2 is presented in soluble form or bound to dendritic cells and the extracellular matrix. Use of IL-2 - either alone or in complex with particular neutralizing IL-2-specific antibodies - can amplify CD8(+) T cell responses or induce the expansion of the T(Reg) cell population, thus favouring either immune stimulation or suppression.

The role of regulatory T cells in familial Mediterranean fever (FMF)

The role of regulatory T cells (T-regs) in familial Mediterranean fever (FMF) was never evaluated. Preliminary studies that we have conducted suggested a rise in the number of regulatory T cells after FMF attacks reaching a maximal level at 7 days. The aim of this study was to evaluate the percentage and activity of regulatory T cells in FMF. Six patients with refractory FMF and six healthy controls were evaluated. The percentage of T-reg cells and forkhead box protein 3 (Foxp3) expression was evaluated and compared between four states: FMF in remission, FMF at the first day of an attack, FMF 7 days after the start of the attack, and healthy controls. Four females and two males were included. All patients had FMF with high severity score, 2.8 ± 0.4 (0-3). The mean age was 31.6 ± 6.2. The mean age at onset was 9.3 ± 9.3. The mean colchicine dose was 2.6 mg ± 0.4. The expression of Foxp3 7 days after the attacks was significantly higher than in FMF at the first day of the attack, FMF in remission, and healthy controls 10.08 ± 2.36 vs. 7.005 ± 0.3 vs. 5.3 ± 1.06 vs. 4.44 ± 1.8; p < 0.05 (Fig.1). The percentage of T-regs in peripheral blood was not statistically different between the four groups. Theexpression of Foxp3 by T-regs increases 7 days after attacks of FMF. Anti-inflammatory cytokines interleukin-10 and TGF-β are known to activate T-regs and have been reported to increase in FMF attacks in line with the present findings. It is suggested that T-regs may have a role in terminating FMF attacks.

[Kidney involvement in mixed cryoglobulinemia: which treatment?]

A kidney involvement is found in 20 to 56% of patients presenting with a cryoglobulinemic vasculitis, type II IgMk, associated to hepatitis C virus infection (HCV). Patients present with a membrano-proliferative glomerulonephritis. In HCV-associated cases, treatment guidelines are adapted to the severity of the disease. In severe forms, including those with kidney involvement, treatment starts with rituximab then an optimal antiviral combination. In non-HCV cases combination with steroids, immunosuppressants and plasmapheresis showed variable efficacy. Retrospective analysis of rituximab showed a great efficacy in more than 80% patients with an increased risk of severe infections (14.1/100 patient-years), particularly in patients over 70 years, with a renal insufficiency and previously treated with high dose steroids.

The adult respiratory distress syndrome. Clinical features, factors influencing prognosis and principles of management

Low-dose IL-2 is efficacious in steroid-refractory cGVHD, with objective responses in >50% of patients, and durable disease control. IL-2 initiation earlier after cGVHD onset, prior to severe impairment of Treg:Tcon ratios, improves likelihood of clinical response.