Rational interleukin 2 therapy for HIV positive individuals: daily low doses enhance immune function without toxicity

Oscillatory IL-2 stimulus reveals pertinent signaling timescales of T cell responsiveness

Cell response to extracellular ligand is affected not only by ligand availability, but also by pre-existing cell-to-cell variability that enables a range of responses within a cell population. We developed a computational model that incorporates cell heterogeneity in order to investigate Jurkat T cell response to time dependent extracellular IL-2 stimulation. Our model predicted preferred timing of IL-2 oscillatory input for maximizing downstream intracellular STAT5 nuclear translocation. The modeled cytokine exposure was replicated experimentally through the use of a microfluidic platform that enabled the parallelized capture of dynamic single cell response to precisely delivered pulses of IL-2 stimulus. The in vitro results demonstrate that single cell response profiles vary with pulsatile IL-2 input at pre-equilibrium levels. These observations confirmed our model predictions that Jurkat cells have a preferred range of extracellular IL-2 fluctuations, in which downstream response is rapidly initiated. Further investigation into this filtering behavior could increase our understanding of how pre-existing cellular states within immune cell populations enable a systems response within a preferred range of ligand fluctuations, and whether the observed cytokine range corresponds to in vivo conditions.

Development of Interleukin-2 Loaded Chitosan-Based Nanogels Using Artificial Neural Networks and Investigating the Effects on Wound Healing in Rats

The aim of this study was to develop and characterize rh- IL-2 loaded chitosan-based nanogels for the healing of wound incision in rats. Nanogels were prepared using chitosan and bovine serum albumin (BSA) by ionic gelation method and high temperature application, respectively. Particle size, zeta potential, and polydispersity index were measured for characterization of nanogels. The morphology of nanogels was examined by using SEM and AFM. The IL-2 loading capacity of nanogels was determined using ELISA method. In vitro release of IL-2 from nanogels was performed using Franz diffusion cells. Artificial neural network (ANN) models were developed using selected input parameters (stirring rate, chitosan%, BSA%, TPP%) where particle size was an output parameter for IL-2 free nanogels. Wound healing effect of IL-2 loaded chitosan-TPP nanogel was evaluated by determining the malondialdehyde (MDA) and glutathione (GSH) levels of wound tissues in rats. The particle size of IL-2 loaded chitosan-TPP nanogels was found to be larger than that of IL-2 loaded BSA-based chitosan nanogels. Drug loading capacity of nanogels was found 100% ± 0.010 for both nanogels. IL-2 was released slowly after the initial burst effect. According to SEM and AFM imaging, BSA-chitosan nanogel particles were of nanometer size and presented a swelling tendency, and chitosan-TPP nanogel particles were found to be spherical and homogenously dispersed. IL-2 loaded chitosan-TPP nanogel was found suitable for improving wound healing because it decreased the MDA levels and increased the GSH levels wound tissues comparing to control group.

Interleukin-2 Therapy Induces CD4 Downregulation, Which Decreases Circulating CD4 T Cell Counts, in African Green Monkeys

African green monkeys (AGMs) are natural hosts of simian immunodeficiency virus (SIVAGM). Because these animals do not develop simian AIDS despite maintaining high viral loads, there is considerable interest in determining how these animals have evolved to avoid SIV disease progression. Unlike nonnatural hosts of SIV, adult AGMs maintain low levels of CD4(+) T cells at steady states and also have a large population of virus-resistant CD8αα T cells that lack CD4 expression despite maintaining T helper cell functionalities. In recent work, we have shown that homeostatic cytokines can induce CD4 downregulation in AGM T cells in vitro Through administering therapeutic doses of recombinant human interleukin-2 (IL-2) to AGMs, we show here that this mechanism is operative in vivo IL-2 therapy induced transient yet robust proliferation in all major T cell subsets. Within the CD4(+) T cell population, those that were induced into cycle by IL-2 exhibited characteristics of CD4-to-CD8αα conversion. In all animals receiving IL-2, circulating CD4(+) T cell counts and proportions tended to be lower and CD4(-) CD8αα(+) T cell counts tended to be higher. Despite reductions in circulating target cells, the viral load was unaffected over the course of study.

IMPORTANCE

The data in this study identify that homeostatic cytokines can downregulate CD4 in vivo and, when given therapeutically, can induce AGMs to sustain very low levels of circulating CD4(+) T cells without showing signs of immunodeficiency.

Structured Treatment Interruptions and Low Doses of IL-2 in Patients with Primary HIV Infection. Inflammatory, Virological and Immunological Outcomes

BACKGROUND

Interventions during primary HIV infection (PHI) can modify the clinical course during the chronic phase. The long-term effect of structured treatment interruptions (STI) followed by low doses of interleukin-2 (IL-2) in treated PHI patients is unknown.

METHODS

Twelve PHI patients with viral load (VL) <20 copies/mL, CD4 cells >500 cells/mm3, and CD4/CD8 ratio >1, on antiretroviral therapy (ART) initiated within the first 90 days of infection and continued for at least 12 months were included. They underwent four STI and were then allocated (week 0 of the study) to ART alone or ART plus low doses of IL-2. ART was stopped once VL <20 copies/mL ('final stop'). Primary endpoints were VL<3000 copies/mL and CD4 cells >500 cells/mm3 at 48 weeks; secondary endpoints were immune activation, inflammatory markers until 48 weeks and the time before resuming ART (CD4 <350 cells/mm3 or AIDS) after 'final stop', compared between groups.

RESULTS

Ten out of 12 patients were males, median age was 35 years and the main risk was men-who-have-sex-with-men. Only one out of 12 patients (in the STI group) maintained VL<3000 copies/mL and CD4 cells >500 cells/mm3 without ART at 48 weeks. All other virological and immunological parameters were comparable between groups at week 0, 'final stop' and week 48. However, the proportion of CD8-CD38+ cells, tumor necrosis factor and srIL-2 were higher in the IL-2 group at 'final stop' and week 24. All these differences vanished during follow-up. At 5 years after the final stop 3 out of 6 patients in the IL-2 group and 6 out of 6 patients in the STI group have resumed ART (P = 0.19).

CONCLUSIONS

STI and IL-2 failed to achieve virological control after ART interruption. STI were not deleterious in long-term follow-up, an important issue for eradication and functional cure trials.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02300623.

Multifarious immunotherapeutic approaches to cure HIV-1 infection

Immunotherapy in the context of treated HIV-1 infection aims to improve immune responses to achieve better control of the virus. To date, multifaceted immunotherapeutic approaches have been shown to reduce immune activation and increase CD4 T-lymphocyte counts, further to the effects of antiretroviral therapy alone, in addition to improving HIV-1-specific T-cell responses. While sterilizing cure of HIV-1 would involve elimination of all replication-competent virus, a functional cure in which the host has long-lasting control of viral replication may be more feasible. In this commentary, we discuss novel strategies aimed at targeting the latent viral reservoir with cure of HIV-1 infection being the ultimate goal, an achievement that would have considerable impact on worldwide HIV-1 infection.

Maintenance biotherapy with interleukin-2 and interferon for metastatic renal cell cancer

The term maintenance immunotherapy comprises at least two different therapeutic approaches: the continuation of immunotherapy beyond disease progression and the use of chronic immunotherapy after the achievement of an initial response (or disease stabilization) with more intensive treatment modalities, such as chemotherapy. The former therapeutic approach was proposed in renal cell carcinoma some years ago relying on several immunological considerations. Some years later, we have learned that it is feasible and endowed with a favorable therapeutic index; furthermore, its immunologic effects are well described and reproducible, and it has antitumor activity. However, due to the lack of adequate randomized Phase III studies, the actual impact of this treatment strategy on patient survival has not yet been proved. The rationale of this treatment, its immunological and clinical results, as well as its pitfalls and perspectives, will be presented and discussed in this review.

Epstein-Barr virus-driven lymphomagenesis in the context of human immunodeficiency virus type 1 infection

Epstein-Barr virus (EBV) is a ubiquitous human γ-herpes virus which establishes a life-long asymptomatic infection in immunocompetent hosts. In human immunodeficiency virus type 1 (HIV-1) infected patients, the impaired immunosurveillance against EBV may favor the development of EBV-related diseases, ranging from lymphoproliferative disorders to B cell non-Hodgkin's lymphomas (NHL). Antiretroviral therapy (ART) has significantly modified the natural course of HIV-1 infection, resulting in decreased HIV-1 plasmaviremia, increased CD4 lymphocytes, and decreased opportunistic infections, indicating a restoration of immune functions. However, the impact of ART appears to be less favorable on EBV-related malignancies than on other AIDS-defining tumors, such as Kaposi's sarcoma, and NHL remains the most common cancer during the ART era. EBV-driven tumors are associated with selective expression of latent oncogenic proteins, but uncontrolled lytic cycle with virus replication and/or reactivation may favor cell transformation, at least in the early phases. Several host's factors may promote EBV reactivation and replication; besides immunodepression, inflammation/chronic immune stimulation may play an important role. Microbial pathogen-associated molecular patterns and endogenous damage-associated molecular patterns, through Toll-like receptors, activate the immune system and may promote EBV reactivation and/or polyclonal expansion of EBV-infected cells. A body of evidence suggests that chronic immune stimulation is a hallmark of HIV-1 pathogenesis and may persist even in ART-treated patients. This review focuses on lymphomagenesis driven by EBV both in the context of the natural history of HIV-1 infection and in ART-treated patients. Understanding the mechanisms involved in the expansion of EBV-infected cells is a premise for the identification of prognostic markers of EBV-associated malignancies.

PD-L1 blockade synergizes with IL-2 therapy in reinvigorating exhausted T cells

The inhibitory receptor programmed cell death 1 (PD-1) plays a major role in functional exhaustion of T cells during chronic infections and cancer, and recent clinical data suggest that blockade of the PD-1 pathway is an effective immunotherapy in treating certain cancers. Thus, it is important to define combinatorial approaches that increase the efficacy of PD-1 blockade. To address this issue, we examined the effect of IL-2 and PD-1 ligand 1 (PD-L1) blockade in the mouse model of chronic lymphocytic choriomeningitis virus (LCMV) infection. We found that low-dose IL-2 administration alone enhanced CD8+ T cell responses in chronically infected mice. IL-2 treatment also decreased inhibitory receptor levels on virus-specific CD8+ T cells and increased expression of CD127 and CD44, resulting in a phenotype resembling that of memory T cells. Surprisingly, IL-2 therapy had only a minimal effect on reducing viral load. However, combining IL-2 treatment with blockade of the PD-1 inhibitory pathway had striking synergistic effects in enhancing virus-specific CD8+ T cell responses and decreasing viral load. Interestingly, this reduction in viral load occurred despite increased numbers of Tregs. These results suggest that combined IL-2 therapy and PD-L1 blockade merits consideration as a regimen for treating human chronic infections and cancer.

Pathogenesis and treatment of HIV infection: the cellular, the immune system and the neuroendocrine systems perspective

Infections with HIV represent a great challenge for the development of strategies for an effective cure. The spectrum of diseases associated with HIV ranges from opportunistic infections and cancers to systemic physiological disorders like encephalopathy and neurocognitive impairment. A major progress in controlling HIV infection has been achieved by highly active antiretroviral therapy (HAART). However, HAART does neither eliminate the virus reservoirs in form of latently infected cells nor does it completely reconstitute immune reactivity and physiological status. Furthermore, the failure of the STEP vaccine trial and the only marginal efficacies of the RV144 trial together suggest that the causal relationships between the complex sets of viral and immunological processes that contribute to protection or disease pathogenesis are still poorly understood. Here, we provide an up-to-date overview of HIV-host interactions at the cellular, the immune system and the neuroendocrine systems level. Only by integrating this multi-level knowledge one will be able to handle the systems complexity and develop new methodologies of analysis and prediction for a functional restoration of the immune system and the health of the infected host.

In vitro restoration of Th17 response during HIV infection with an antiretroviral drug and Th17 differentiation cytokines

The Th17 subset is preferentially depleted as compared to the Th1 subset in chronically HIV-infected patients, even after successful antiretroviral therapy. In this study, we have established an in vitro system utilizing primary human CD4 T cell cultures that recapitulates the dramatic loss of Th17 response upon HIV-1 infection that is accompanied with a less profound Th1 decrease. With this experimental system, we showed that blocking viral entry with CCR5 ligands or TAK779 reduced the infection and enhanced Th17 response but not Th1 response. Antiretroviral drug 3TC (lamivudine), given at the time of infection, completely prevented the loss of Th17 and Th1 responses but was ineffective when given after infection was already established. Only when Th17 differentiation cytokines were given along with 3TC to the cultures with established HIV infection was Th17 response fully restored and virus replication kept suppressed. Finally, a significant increase of Th17 response was achieved in peripheral lymphocytes of HIV-infected patients on antiretroviral therapy after treatment with Th17 differentiation cytokines. These data demonstrate the presence of CD4 T cells remaining capable of mounting Th17 response during HIV infection and indicate the potential use of immunotherapeutic modalities to supplement antiretroviral drugs for restoring Th17 response in chronically HIV-infected patients.

HIV-1 POPULATION DYNAMICS IN VIVO: IMPLICATIONS FOR PATHOGENESIS, EFFECT OF CYTOKINE AND THERAPY STRATEGY

In this paper, we present a dynamical model to study the spread of HIV-1 in vivo. Our goal is to better understand the interaction between HIV-1 and the human immune system. Making use of the Hill function, we describe two kinds of processions occurring in the immune response: the activation interactions or inhibitory interactions occurring between different components in the immune response, and the autocatalytic maintenance of the CD4+ T cells and CD8+ T cells populations. We also consider the impact of the cytokine interleukin-2 (IL-2) and the CD8 antiviral factor (CAF) on HIV-1 infection. Through numerical simulations we get several results. First, we find that the effects of IL-2 and CAF in the treatment for the infected are limiting. Namely, the curative effect will not always increase along with the dose of IL-2 or CAF or both. The increasing trend will stagnate at a certain dose that we used. Second, we find some possible reasons for the collapse of the lymph system in HIV-1 infection — the loss of these restraining functions, and/or the genetic variability of the virus due to immune escape that enhances the virulence, which then bring the collapse of the immune system. In some conditions the system will produce a Hopf bifurcation. We also simulate the theoretical warrant of the feasibility of the combined chemotherapy strategies for the HIV-1 infected patient.

Increased CD4+ T cell levels during IL-7 administration of antiretroviral therapy-treated simian immunodeficiency virus-positive macaques are not dependent on strong proliferative responses

CD4(+) T cell depletion is a fundamental component of HIV infection and AIDS pathogenesis and is not always reversed following antiretroviral therapy (ART). In this study, the SIV-infected rhesus macaque model was used to assess recombinant simian IL-7 in its glycosylated form (rsIL-7gly) to enhance regeneration of CD4(+) T cells, particularly the crucial central memory compartment, after ART. We assessed the impact of rsIL-7gly administration as single injections and as a cluster of three doses. Irrespective of the dosing strategy used, the rsIL-7gly administration transiently increased proliferation of both central memory and naive cells, in both CD4(+) and CD8(+) subsets, without increasing SIV levels in the blood. Administration of rsIL-7gly at intervals of 4-6 wk maximized the proliferative response to therapy but resulted in only transient increases in peripheral blood T cell counts. Although more frequent rsIL-7gly "clustered" dosing (three times weekly with 2 wk of rest and then repeat) induced only an initial proliferative burst by CD4(+) T cells, this dosing strategy resulted in sustained increases in peripheral blood CD4(+) T cell counts. The clustered rsIL-7gly treatment regimen was shown to increase the half-life of a BrdU label among memory T cells in the blood when compared with that of macaques treated with ART alone, which is consistent with enhanced cell survival. These results indicate that dosing intervals have a major impact on the response to rsIL-7gly in SIV-positive ART-treated rhesus macaques and that optimum dosing strategies may be ones that induce CD4(+) T cell proliferation initially and provide increased CD4(+) T cell survival.

Changes in the levels of some acute-phase proteins in human immunodeficiency virus-1 infected patients, following interleukin-2 treatment

Intermittent interleukin (IL)-2 administration to human immunodeficiency virus (HIV)-1 infected patients is well documented and generally used, but there is limited information about the changes of acute-phase protein (APP) levels in response to this treatment. Fifteen patients undergoing highly active anti-retroviral therapy (HAART) treatment, with undetectable viral load, but low CD4+ cell count (<300/microl), have been treated with 3.6 M IU Proleukine administered twice daily by subcutaneous injection over 5 days. C-reactive protein (CRP), D-dimer, C3, C9, C1-inh and alpha-2HS glycoprotein levels were measured immediately before IL-2 administration, as well as on day 5 and 2-3 weeks thereafter. After IL-2 administration, both mean D-dimer and CRP levels increased significantly (P<0.001), but returned (P<0.001) to baseline within the subsequent 2-3 weeks. Alpha-2HS glycoprotein decreased immediately after IL-2 administration. No significant differences were detected in the levels of C3, C9 and C1-inh. A significant, positive correlation (r=0.5178, P=0.0008) was ascertained between the changes of CRP level, measured immediately before as well as 5 days after IL-2 administration, and changes in CD4 T cell counts measured 2-3 weeks before and after treatment, respectively. IL-2 administration induces rapid elevation of two major APPs (CRP, D-dimer). The positive correlation observed between the changes of CRP levels and CD4+ cell counts after IL-2 administration may indicate that the abrupt, but transitory overproduction of CRP might contribute to the CD4+ cell count-increasing effect of the drug and/ or may be associated with serious side effects.

Safety and efficacy of treatment using interleukin-2 in a patient with idiopathic CD4(+) lymphopenia and Mycobacterium avium-intracellulare

We present the case of a 39-year-old white man with a Myobacterium avium-intracellulare pulmonary infection found to have a CD4(+) count of 172 cells/mm(3) and diagnosed subsequently with idiopathic CD4(+) lymphopenia (ICL). After receiving clathromycin for 4 months with minimal improvement, the patient was started on pegylated subcutaneous interleukin (IL)-2 at 600,000 units daily. Later, he received incrementally higher pegylated IL-2 doses until he reached a maintenance dose 3 months later of 11 million units weekly divided into three equal doses. After 5 months of therapy, the patient's chronic cough resolved completely, sputum cultures became negative for Myobacterium avium-intracellulare and the CD4(+) T cell count increased to 553 cells/mm(3). After 35 months of well-tolerated IL-2 treatments and no recurrence of any opportunistic infections, IL-2 treatment was stopped. CD4(+) counts 6 and 9 months after discontinuing IL-2 treatment were 596 and 378 cells/mm(3) respectively, and he remains asymptomatic. This report supports IL-2 treatment for ICL-associated opportunistic infections as a safe and potentially efficacious treatment option, especially when combined with more traditional treatment regimens.

Safety, tolerability, pharmacokinetics, and efficacy of an interleukin-2 agonist among HIV-infected patients receiving highly active antiretroviral therapy

We sought to determine the safety, maximum tolerated dose, optimal dose, and preliminary dose efficacy of intermittent subcutaneously (s.c.) administered BAY 50-4798 among patients with HIV infection receiving highly active antiretroviral therapy (HAART) compared with patients receiving HAART alone. A phase I/II randomized, double-blind, dose-escalation study was conducted of the safety, tolerability, pharmacokinetics, and efficacy of s.c. BAY 50-4798 administered to HIV-infected patients already receiving stable HAART. There were no unexpected safety findings in a population of HIV-infected patients receiving HAART plus SC BAY 50-4798 as adjunctive therapy. BAY 50-4798 exhibited nearly dose-proportional pharmacokinetics, and accumulation was minimal during multiple-dose treatment. Limited efficacy data indicated that treatment with BAY 50-4798 caused at least a transient increase in CD4(+) T cell counts in some recipients, particularly at the early time points. In general, this effect appeared to increase with increasing dose. Bay 50-4798 was generally well tolerated across the dose range tested, but a lack of potent, sustained immunologic activity suggests that further optimization of dose and schedule will be necessary.

Immune reconstitution of CD56(dim) NK cells in individuals with primary HIV-1 infection treated with interleukin-2

Natural killer (NK) cells are believed to play a role in human immunodeficiency virus type 1 (HIV-1) disease progression, and NK cell levels are reduced in individuals with chronic HIV-1 infection. Interleukin (IL)-2 therapy results in an expansion of CD4(+) T cells as well as NK cells; however, little is known about the detailed effects of IL-2 therapy on NK cells in HIV-1 infection in general and in early infection in particular. Here, we investigated the effects of combined IL-2 therapy and antiretroviral therapy (ART) on the number, frequency, phenotype, and interferon (IFN)-gamma production of NK cells in individuals with early HIV-1 infection. Patients randomized to receive combined ART and IL-2 therapy predominantly expanded CD56(dim) NK cells, and the expansion was greater than in patients randomized to receive ART alone. Importantly, NK cell receptor expression and IFN-gamma production were maintained over time. This reconstitution of NK cells may be useful in helping contain viremia if patients discontinue therapy or develop drug resistance.

Failure of low-dose recombinant human IL-2 to support the survival of virus-specific CTL clones infused into severe combined immunodeficient foals: lack of correlation between in vitro activity and in vivo efficacy

Although CTL are important for control of lentiviruses, including equine infectious anemia virus (EIAV), it is not known if CTL can limit lentiviral replication in the absence of CD4 help and neutralizing antibody. Adoptive transfer of EIAV-specific CTL clones into severe combined immunodeficient (SCID) foals could resolve this issue, but it is not known whether exogenous IL-2 administration is sufficient to support the engraftment and proliferation of CTL clones infused into immunodeficient horses. To address this question we adoptively transferred EIAV Rev-specific CTL clones into four EIAV-challenged SCID foals, concurrent with low-dose aldesleukin (180,000U/m2), a modified recombinant human IL-2 (rhuIL-2) product. The dose was calculated based on the specific activity on equine PBMC in vitro, and resulted in plasma concentrations considered sufficient to saturate high affinity IL-2 receptors in humans. Despite specific activity on equine PBMC that was equivalent to recombinant equine IL-2 and another form of rhuIL-2, aldesleukin did not support the engraftment and expansion of infused CTL clones, and control of viral load and clinical disease did not occur. It was concluded that survival of Rev-specific CTL clones infused into EIAV-challenged SCID foals was not enhanced by aldesleukin at the doses used in this study, and that in vitro specific activity did not correlate with in vivo efficacy. Successful adoptive immunotherapy with CTL clones in immunodeficient horses will likely require higher doses of rhuIL-2, co-infusion of CD4+ T lymphocytes, or administration of equine IL-2.

Blockade of hyaluronan inhibits IL-2-induced vascular leak syndrome and maintains effectiveness of IL-2 treatment for metastatic melanoma

Vascular leak syndrome (VLS) is a life-threatening toxicity induced during IL-2 treatment of cancer patients. The mechanism of IL-2-induced VLS is still poorly understood. At present, there is no specific therapy for VLS. Previous studies from our laboratory demonstrated that hyaluronan (HA), a large glycosaminoglycan, abundant in the extracellular matrix and on the cell surface, caused a marked increase of IL-2-induced VLS in the lungs and liver of C57BL/6 mice. Conversely, blockade or knockout of its major receptor, CD44, resulted in a marked decrease of VLS, thereby suggesting a role for HA in VLS. In this study, we report a novel means to prevent IL-2-induced VLS by blocking endogenous HA with HA-specific binding peptide, Pep-1, a newly isolated peptide which specifically binds to soluble, cell-associated, and immobilized forms of HA. Our results demonstrated that blocking HA with Pep-1 dramatically inhibited IL-2-induced VLS in both normal mice as well as in mice bearing melanoma. Moreover, Pep-1 treatment maintained the effectiveness of IL-2 and prevented the metastasis of melanoma. IL-2-induced emigration of lymphocytes across the endothelium and cytotoxicity against tumor by lymphokine-activated killer cells were not affected by Pep-1. Instead, use of Pep-1 maintained endothelial integrity and reduced their apoptosis during IL-2-induced VLS. These data suggested that HA plays a critical role in regulating endothelial cell damage and induction of IL-2-mediated VLS. Also, blockade of HA using Pep-1 could constitute a novel therapeutic modality to prevent IL-2-mediated toxicity, thereby facilitating the effectiveness of high-dose IL-2 in the treatment of metastatic melanomas.

Latent reservoirs for HIV-1

Combination therapy for HIV-1 infection can reduce viremia to undetectable levels, suggesting that prolonged treatment might eradicate the infection. However, one potential mechanism for viral persistence involves the establishment of a state of latent infection. Recent studies have directly confirmed that HIV-1 establishes a state of latent infection in resting memory CD4(+) T cells in vivo. This reservoir is likely to frustrate current efforts to eradicate the infection with combination therapy.

Low-dose interleukin-2 administered pre-operatively to patients with gastric cancer activates peripheral and peritumoral lymphocytes but does not affect prognosis

BACKGROUND

There is evidence that cancer is immunogenic under certain situations. IL-2 is described to stimulate an effective antitumor immune response in vitro and in vivo. The ability of cancer patients to undergo surgical resection is still the most important prognostic factor for many solid tumors, including gastric adenocarcinoma. The host immune system may be further compromised by surgical procedures leading to a generalized state of immunodepression in the post-operative period. The aim of this randomized case-control study is to evaluate the effects of pre-operative low-dose IL-2 treatment on patients with gastric adenocarcinoma who undergo surgery.

METHODS

Sixty-eight patients with gastric adenocarcinoma were enrolled in the study and randomized in two groups: 36 patients were pre-treated with IL-2 and 32 underwent surgery without any treatment. Total peripheral WBC, neutrophils, CD3(+) T, CD4(+) T, CD8(+) T and NK cells were obtained before and after surgery, at different times. Peritumoral infiltration was analyzed on all surgical specimens. Overall survival and relapse-free survival were studied with a median follow-up of 51 months.

RESULTS

Low-dose IL-2 treatment resulted in an increase peritumoral lymphocytic and eosinophilic infiltrations and in a minor decrease in CD3(+) T and CD4(+) T cells after surgery (P < 0.05). A stepwise multivariate analysis revealed that overall survival and relapse-free survival were affected only by stage of tumor and age of patients.

CONCLUSIONS

According to our data low-doses of IL-2 administered pre-operatively to patients with gastric cancer activate peripheral and peri-tumoral lymphocytes but did not affect prognosis.

Identification of a novel G245R polymorphism in the IL-2 receptor beta membrane proximal domain associated with human visceral leishmaniasis

Binding of the interleukin-2 (IL-2) to the IL-2 receptor (IL-2R) triggers a series of intracellular events culminating in lymphocyte proliferation and differentiation. We report here the identification of a novel G245R polymorphism in the membrane proximal domain of the IL-2 receptor beta chain (IL-2Rbeta). Present at a frequency of 7.2%, the IL-2-Rbeta G245R was identified in a population of Eastern Sudan exposed to a severe outbreak of visceral leishmaniasis (VL), a disease associated with a marked depression of T-cell antigen-specific responses. The location of the G245R polymorphism next to the box1/box2 proximal cytokine receptor homology segment and suggestive genetic association with the development of disease (P=0.043), suggest that it may affect Janus kinase (JAK) association and impair growth signal transduction. However, additional genetic association with a synonymous single nucleotide polymorphism (IL2RB+8777T) suggests that other variations of IL2RB or nearby genes participate in the highly significant linkage with VL at 22q12 previously reported for this population.

Integrated non-invasive system for quantifying secreted human therapeutic hIL2

Cell encapsulation has been used to treat diabetes, amyotrophic lateral sclerosis, and other chronic ailments by the secretion of therapeutic proteins in vivo. Detection of these proteins typically requires invasive procedures such as blood sampling or device extraction, however. In this article, a non-invasive means of measuring secreted protein concentration using a co-expressed red fluorescent protein marker is developed. A bicistronic expression vector was constructed for the intracellular production of a red fluorescent protein marker and the secreted production of human interleukin-2 (hIL2). The destabilized red fluorescent protein, DsExDR, was selected for its rapid turnover, as well as its ability to emit red light, which is readily transmitted through mammalian tissue. Transfections of this bicistronic vector into three cell lines C2C12, HEK293, and Jurkat showed linear correlations between the expressed proteins, DsExDR (intracellular) and hIL2 (secreted), with transfection DNA concentration. Correspondingly, there was a linear correlation between secreted product (hIL2) and intracellular marker (DsExDR). As transfection DNA was increased, Jurkat cells were found to increase secreted hIL2 in direct proportion to the accumulated DsExDR. HEK293 and C2C12 cells expressed and secreted significantly more hIL2 than the Jurkat cells, while still maintaining a linear relationship. Thus, all three cell lines were suitable hosts for the bicistronic expression of DsExDR and expression and secretion of therapeutic hIL2. This reporting strategy may find the greatest use in cell encapsulation therapy.

Secretion of human interleukin-2 fused with green fluorescent protein in recombinant Pichia pastoris

Methylotrophic yeast Pichia pastoris is convenient for the expression of eukaryotic foreign proteins owing to its potential for posttranslational modifications, protein folding, and facile culturing. In this work, human interleukin (hIL)-2 was successfully produced as a secreted fusion form in recombinant P. pastoris. By employing green fluorescent protein (GFP) as a monitoring fusion partner, clear identification of fusion protein expression and quantification of intracellular hIL-2 were possible even though there was no correlation between culture supernatant fluorescence and secreted hIL-2 owing to high media interference. Importantly, by the addition of casamino acids in basal medium, we were able to enhance threefold amount of secreted hIL-2, which was present both as a fusion and as a clipped fragment.

Daily low-dose subcutaneous interleukin-2 added to single- or dual-nucleoside therapy in HIV infection does not protect against CD4+ T-cell decline or improve other indices of immune function: results of a randomized controlled clinical trial (ACTG 248)

CONTEXT

Approaches to preserve or enhance immune function in HIV-1 infection are needed.

OBJECTIVES

To examine the ability of daily low-dose interleukin-2 (IL-2) in combination with antiretroviral therapy to preserve circulating CD4+ T-cell counts, the clinical safety and tolerability of this treatment, and safety with respect to changes in plasma HIV-1 RNA levels.

DESIGN

Twenty-four-week, phase 2, multicenter, randomized, open-label trial conducted at 12 AIDS Clinical Trials Units between September 1995 and May 1997.

PARTICIPANTS

A total of 115 HIV-infected persons with screening CD4+ T-cell counts between 300 and 700 cells/mm who were on stable single- or dual-nucleoside therapy for at least 2 months, 11% of whom were also on a protease inhibitor at study entry.

INTERVENTIONS

Patients were randomly assigned to receive IL-2 at a dose of 1 million IU subcutaneously once daily plus continued anti-retroviral therapy (ART + IL-2, n = 57) vs. continued ART alone (ART alone, n = 58). IL-2 dose reductions were made for objective or subjective toxicities. All subjects randomly assigned to the IL-2 arm who interrupted ART were also required to discontinue IL-2 for the same period.

MAIN OUTCOME MEASURES

The primary endpoint was a decrease in CD4 T-cell count from baseline; the safety analysis was based on change in plasma HIV RNA by bDNA; and clinical safety and tolerability were analyzed by standard clinical criteria.

RESULTS

Of the patients with a baseline CD4 T-cell count recorded, 15 (27%) of 55 patients randomly assigned to ART alone had a drop of > or =25% in their CD4 T-cell count and 23 (41%) of 56 patients randomly assigned to ART + IL-2 had a drop of > or =25% in their CD4 T-cell count at some time over the 24 weeks of the study. This difference was not statistically significant. There was a statistically significant greater variance in CD4 T-cell counts in the IL-2-treated group. More patients in the IL-2 group had at least a 25% increase in CD4 T-cell counts over baseline (34 vs. 13%, P = 0.007). A comparison of grade 3 or worse toxicity showed no differences between the arms, but IL-2 was associated with significantly more grade 2 or worse general body symptoms, primarily discomfort and fatigue. There was no significant difference between the groups with regard to changes in plasma HIV RNA, lymphocyte proliferation, natural killer cell activity, skin test responses to recall antigens, or antibody responses to immunization. Plasma markers of immune activation all increased significantly in IL-2 recipients.

CONCLUSIONS

In patients with baseline CD4 T-cell counts > or =300 cells/mm primarily treated with single- or dual-nucleoside ART, subcutaneously administered IL-2 at a dose of 1 million IU daily for up to 24 weeks had low toxicity but showed no consistent benefit in preventing decline in CD4 T-cell counts and minimal evidence of immunologic improvement vs. continued ART alone.

IL-2 responsiveness of CD4 and CD8 lymphocytes: further investigations with human IL-2Rbeta transgenic mice

Responsiveness to IL-2 varies from one lympho-mononuclear subset to another. NK lymphocytes and monocytes spontaneously respond to IL-2 whereas it is generally accepted that T and B lymphocytes need to be activated to fully acquire this competence. To further investigate this phenomenon, we studied human IL-2Rbeta (hIL-2Rbeta) transgenic mice constitutively expressing heterospecific, intermediate-affinity IL-2R (hIL-2Rbeta/mouse IL-2Rgamma(c)). We noted that the B lymphocytes and monocytes from spleens of these hIL-2Rbeta transgenic animals failed to grow when cultured in IL-2-containing medium. Under the same experimental conditions, CD4 lymphocytes survived, again without growth, whereas CD8 lymphocytes and NK cells were able to proliferate and develop potent LAK cytotoxicity. The properties of these CD4 and CD8 lymphocytes were then compared after purification. Both subsets expressed functional IL-2R able to induce global protein phosphorylation and, more precisely, signal transducer and activation of transcription 5 and Erk phosphorylation. Therefore, the differential growth potential of these CD4 and CD8 lymphocytes cannot be explained by the lack of IL-2R-dependent early signaling events. When the entrance of purified CD4 and CD8 lymphocytes into the cell cycle was analyzed, we found that the CD4 lymphocytes were unable to enter the G1 phase in the absence of anti-CD3 stimulation. This correlates with the effect of IL-2 on cyclin-dependent kinase inhibitor p27(kip1). In CD4 lymphocytes, IL-2 does not affect p27(kip1) expression. But in CD8 lymphocytes, IL-2 down-modulates p27(kip1). These results indicate that, aside from IL-2R expression and function, IL-2 responsiveness is also controlled by lineage-specific mechanisms.

Contrasting Effects of Low-Dose IL-2 on Vaccine-Boosted Simian Immunodeficiency Virus (SIV)-Specific CD4+and CD8+T Cells in Macaques Chronically Infected with SIVmac251

IL-2, the first cytokine discovered with T cell growth factor activity, is now known to have pleiotropic effects on T cells. For example, it can promote growth, survival, and differentiation of Ag-selected cells, or facilitate Ag-induced cell death of T cells when Ag persists, and in vivo, it is thought to contribute to the regulation of the size of adaptive T cell response. IL-2 is deficient in HIV-1 infection and has been used in the management of HIV-1-infected individuals undergoing antiretroviral therapy. In this study, we investigated how continuous low-dose IL-2 affected the CD4+ and CD8+ T cell response induced by two inoculations of a canarypox recombinant SIV-based vaccine candidate in healthy macaques chronically infected with SIVmac251. These macaques had normal levels of CD4+ T cells at the beginning of antiretroviral therapy treatment. Vaccination in the presence of IL-2 significantly augmented Gag-specific CD8+ T cell responses, but actually reduced Gag-specific CD4+ T cell responses. Although IL-2 at low doses did not change the overall concentration of circulating CD4+ or CD8+ T cells, it expanded the frequency of CD4+CD25+ T cells. Depletion of the CD4+CD25+ T cells in vitro, however, did not result in a reconstitution of Gag-specific CD4+ responses or augmentation of SIV-specific CD8+ T cell responses. Thus, we conclude that the decrease in virus-specific CD4+ T cell response may be due to IL-2-promoted redistribution of cells from the circulation, or due to Ag-induced cell death, rather than suppression by a T regulatory population.

The Use of Interleukin-2 in Human Immunodeficiency Virus Infection

Advances in antiretroviral therapy for human immunodeficiency virus (HIV) have led to reductions in HIV-related morbidity and mortality. Although antiretroviral therapy has shown success in suppressing viral loads, it does not adequately restore the immune system in all individuals infected with HIV. In light of this incomplete success, interleukin (IL)-2 is being evaluated as adjunctive therapy to antiretroviral therapy. The agent has demonstrated mixed yet promising results in restoring immune function in patients who are HIV positive.

Interleukin-2, Interleukin-15, and Their Roles in Human Natural Killer Cells

Natural killer (NK) cells are CD56+CD3- large granular lymphocytes that constitute a key component of the human innate immune response. In addition to their potent cytolytic activity, NK cells elaborate a host of immunoregulatory cytokines and chemokines that play a crucial role in pathogen clearance. Furthermore, interactions between NK and other immune cells are implicated in triggering the adaptive, or antigen-specific, immune response. Interleukin-2 (IL-2) and IL-15 are two distinct cytokines with partially overlapping properties that are implicated in the development, homeostasis, and function of NK cells. This review examines the pervasive effects of IL-2 and IL-15 on NK cell biology, with an emphasis on recent discoveries and lingering challenges in the field.

Immunologic and clinical outcomes of vaccination with a multiepitope melanoma peptide vaccine plus low-dose interleukin-2 administered either concurrently or on a delayed schedule

PURPOSE

A phase II trial was performed to test whether systemic low-dose interleukin-2 (IL-2) augments T-cell immune responses to a multipeptide melanoma vaccine. Forty patients with resected stage IIB-IV melanoma were randomly assigned to vaccination with four gp100- and tyrosinase-derived peptides restricted by human leukocyte antigen (HLA) -A1, HLA-A2, and HLA-A3, and a tetanus helper peptide plus IL-2 administered daily either beginning day 7 (group 1), or beginning day 28 (group 2).

PATIENTS AND METHODS

T-cell responses were assessed by an interferon gamma ELIspot assay in peripheral blood lymphocytes (PBL) and in a lymph node draining a vaccination site (sentinel immunized node [SIN]). Patients were followed for disease-free and overall survival.

RESULTS

T-cell responses to the melanoma peptides were observed in 37% of PBL and 38% of SINs in group 1, and in 53% of PBL and 83% of SINs in group 2. The magnitude of T-cell response was higher in group 2. The tyrosinase peptides DAEKSDICTDEY and YMDGTMSQV were more immunogenic than the gp100 peptides YLEPGPVTA and ALLAVGATK. T-cell responses were detected in the SINs more frequently, and with higher magnitude, than responses in the PBL. Disease-free survival estimates at 2 years were 39% (95% CI, 18% to 61%) for group 1, and 50% (95% CI, 28% to 72%) for group 2 (P = .32).

CONCLUSION

The results of this study support the safety and immunogenicity of a vaccine composed of four peptides derived from gp100 and tyrosinase. The low-dose IL-2 regimen used for group 1 paradoxically diminishes the magnitude and frequency of cytotoxic T lymphocyte responses to these peptides.

NK cells and polymorphonuclear neutrophils are both critical for IL-2-induced pulmonary vascular leak syndrome

The mechanism of IL-2-induced vascular leak syndrome (VLS) is still poorly understood. Cells of both innate and adaptive immune systems have been implicated, but no definitive conclusions have been reached concerning their respective roles. In this study we report a new mouse model of IL-2-induced pulmonary VLS used to obtain a detailed analysis of the early events (sequestration of polymorphonuclear neutrophils and bronchoconstriction) and late events (modifications in the cell and protein content of bronchoalveolar lavages, followed by edema) that characterize this lung injury. This model and knockout animals are used to reconsider the importance of the different leukocyte lineages in early and late events. Recombinase-activating gene 2(-/-) mice are used to demonstrate that adaptive lymphocytes, including NK T cells, are not required for pulmonary VLS induction. By contrast, results obtained with newly described recombinase-activating gene 2(-/-)/IL-15(-/-) mice indicate that NK cells play a key role in both early and late events. In parallel, polymorphonuclear neutrophil depletion is used to evaluate the contributions made by these cells to the late alterations occurring in the lung. Furthermore, when used in combination with inhibition of NO synthase, granulocyte depletion was completely effective in protecting mice from the late events of IL-2-induced pulmonary VLS. Together our results indicate that both NK and PMN cells play a central role in the late events of IL-2-induced VLS.

Assessment of the Toxicities of Systemic Low-Dose Interleukin-2 Administered in Conjunction with a Melanoma Peptide Vaccine

In this phase 2 study, the authors assessed the hematologic and clinical toxicities of a melanoma peptide vaccine administered in conjunction with low-dose interleukin-2 (IL-2) therapy. Forty patients were randomized to receive a weekly vaccine paired with a regimen of subcutaneous IL-2 (3 x 10(6) IU/m2/day) administered daily for 6 weeks beginning either at week 1 or at week 4 of vaccine therapy. The differences in the time course of the IL-2 between the two groups permitted assessment of the cause of the toxicities, due either to IL-2 or to vaccine components. Both treatment regimens were well tolerated in the outpatient setting. Toxicities attributable to the vaccine components were principally limited to grade 1 injection site reactions. Systemic clinical toxicities correlated with the initiation of IL-2 therapy. These toxicities coincided temporally and in magnitude with changes in circulating eosinophil counts, suggesting that systemic clinical toxicities and eosinophilia may have common etiologic pathways. Other minor toxicities attributable to this low-dose IL-2 regimen were clinically insignificant hepatic toxicity, mild anemia, and mild thrombocytosis. The hematologic effects of this therapy were delayed in time between the two treatment groups, without dramatic differences in magnitude, which suggests minimal modulation of the IL-2 toxicity by components of the vaccine.

Enhancement of human immunodeficiency virus type 1-DNA vaccine potency through incorporation of T-helper 1 molecular adjuvants

It is clear that the development of a safe and effective vaccine for human immunodeficiency virus type 1 (HIV-1) remains a crucial goal for controlling the acquired immunodeficiency syndrome epidemic. At present, it is not clear what arm of the immune response correlates with protection from HIV-1 infection or disease. Therefore, a strong cellular and humoral immune response will likely be needed to control this infection. Among different vaccine alternatives, DNA vaccines appeared more than a decade ago, demonstrating important qualities of inducing both humoral and cellular immune responses in animal models. However, after several years and various clinical studies in humans, supporting the safety of the HIV-DNA vaccine strategies, it has become clear that their potency should be improved. One way to modulate and enhance the immune responses induced by a DNA vaccine is by including genetic adjuvants such as cytokines, chemokines, or T-cell costimulatory molecules as part of the vaccine itself. Particularly, vaccine immunogenicity can be modulated by factors that attract professional antigen-presenting cells, provide additional costimulation, or enhance the uptake of plasmid DNA. This review focuses on developments in the coadministration of molecular adjuvants for the enhancement of HIV-1 DNA-vaccine potency.

Expansion of human Valpha24+ NKT cells by repeated stimulation with KRN7000

Changes in Valpha24+Vbeta11+ NKT cell number and function are associated with human autoimmune diseases and cancer. Restoration of this corresponding NKT cell population in mice or in vivo activation with alpha-galactosylceramide (KRN7000) can prevent or reduce tumor growth and autoimmunity. Although the therapeutic value of these natural killer T (NKT) cells in man remains to be determined, large numbers of functional antigen-specific NKT cells can be expanded in vitro. We show that Valpha24+Vbeta11+ human NKT cells are expanded by repeated stimulation with KRN7000, unfractionated donor peripheral blood mononuclear cells (PBMC), and recombinant human interleukin-2 (rhIL-2). NKT cells were expanded continuously for more than 2 months with a potential yield of >10(12) cells. The expanded NKT cells retained their CD4+ or CD4- phenotype after restimulation and were functional as shown by cytokine secretion, killing of antigen-pulsed target cells, and activation of NK cell cytotoxicity. This expansion method may be useful for proof-of-concept studies involving adoptive transfer of ex vivo-expanded NKT cells as a new therapeutic option for cancer and autoimmune diseases.

Interleukin-2--where are we going?

We have seen many advances in treatment modalities for patients infected with HIV. Trying to improve the immune system of our patients is one of them. An interesting treatment being investigated for this purpose is the use of interleukin-2. Interleukin-2 has been used in many clinical trials and is being used in ongoing trials. The successes/limitations of these trials have given us much information. Is immune reconstitution aided by the use of interleukin-2?

Targeted deletion of CD44v7 exon leads to decreased endothelial cell injury but not tumor cell killing mediated by interleukin-2-activated cytolytic lymphocytes

In the current study, we investigated the nature and role of CD44 variant isoforms involved in endothelial cell (EC) injury and tumor cell cytotoxicity mediated by IL-2-activated killer (LAK) cells. Treatment of CD44 wild-type lymphocytes with IL-2 led to increased gene expression of CD44 v6 and v7 variant isoforms and to significant induction of vascular leak syndrome (VLS). CD44v6-v7 knockout (KO) and CD44v7 KO mice showed markedly reduced levels of IL-2-induced VLS. The decreased VLS in CD44v6-v7 KO and CD44v7 KO mice did not result from differential activation and expansion of CD8+ T cells, NK, and NK-T cells or from altered degree of perivascular lymphocytic infiltration in the lungs. LAK cells from CD44v7 KO mice showed a significant decrease in their ability to adhere to and mediate lysis of EC but not lysis of P815 tumor cells in vitro. CD44v7-mediated lysis of EC by LAK cells was dependent on the activity of phosphatidylinositol 3-kinase and tyrosine kinases. Interestingly, IL-2-activated LAK cells expressing CD44hi but not CD44lo were responsible for EC lysis. Furthermore, lysis of EC targets could be blocked by addition of soluble or enzymatic cleavage of CD44v6-v7-binding glycosaminoglycans. Finally, anti-CD44v7 mAbs caused a significant reduction in the adherence to and killing of EC and led to suppression of IL-2-induced VLS. Together, this study suggests that the expression of CD44v7 on LAK cells plays a specific role in EC injury and that it may be possible to reduce EC injury but not tumor cell killing by specifically targeting CD44v7.

Immunodeficiency and cancer: prospects for correction

Cellular immunodeficiency is associated with human cancer. Extensive reviews on cancer of the head and neck, lung, esophagus and breast convince the author that for these diseases the immunodeficiency is reasonably well established yet the mechanisms are poorly understood. Evidence indicates that other tumors are similarly associated with cellular immune deficiency. The advent of recombinant cytokines and of antitumor monoclonal antibodies has served to focus attention toward direct tumoricidal mechanisms. As tumor antigens relating to cellular and humoral immune mechanisms are being defined and vaccine strategies are increasingly being attempted, it is critical to confront issues of the mechanism of anergy and effective immunorestoration in order to maximize the potential of cellular immune response to address these tumor antigens. Intrinsic to this approach is the introduction of contrasuppressive therapy to alleviate the tumor-associated immune suppression. Encouraging attempts have been made with plasmapheresis, indomethacin, low-dose cyclophosphamide, anti CTLA-4, anti FAS ligand and, perhaps in the future, more judiciously applied chemotherapy. In contrast to the popular notion that thymic involution cannot be reversed in the adult, studies from the author's laboratory indicate that in aged hydrocortisone stressed mice, a natural Type 1-cytokine mixture (IRX-2) hastens the reversal of thymic involution and promotes T-cell responses to cytokines and mitogens. Recombinant IL-1 and IL-2 by themselves, and in combination, were inactive. Similar positive effects were observed with oral zinc, zinc-thymulin and thymosin alpha(1). The combination of a natural cytokine mixture (IRX-2) with thymosin alpha1 had a very large effect and increased the absolute number of peripheral T lymphocytes as measured in the spleen. In studies of combination immunotherapy in lymphocytopenic squamous cell head and neck cancer patients using IRX-2 (18 patients) and IRX-2 plus thymosin alpha(1) (IRX-3) in IRX-2-refractory patients (7 patients), marked increases in CD(45)RA(+) 'naïve' T cells (>250/mm(3)) were observed. These are among the first insights into how to generate T lymphocyte replacement in the adult. These and many other experimental efforts point to ways to achieve more effective immunotherapy of human cancer in the future, particularly if tumor-induced immune deficiency can be effectively addressed.

Therapeutic use of IL-2 to enhance antiviral T-cell responses in vivo

Interleukin (IL)-2 is currently used to enhance T-cell immunity but can have both positive and negative effects on T cells. To determine whether these opposing results are due to IL-2 acting differently on T cells depending on their stage of differentiation, we examined the effects of IL-2 therapy during the expansion, contraction and memory phases of the T-cell response in lymphocytic choriomeningitis virus (LCMV)-infected mice. IL-2 treatment during the expansion phase was detrimental to the survival of rapidly dividing effector T cells. In contrast, IL-2 therapy was highly beneficial during the death phase, resulting in increased proliferation and survival of virus-specific T cells. IL-2 treatment also increased proliferation of resting memory T cells in mice that controlled the infection. Virus-specific T cells in chronically infected mice also responded to IL-2 resulting in decreased viral burden. Thus, timing of IL-2 administration and differentiation status of the T cell are critical parameters in designing IL-2 therapies.

IL-2 therapy and thymic production of naive CD4 T cells in HIV-infected patients with severe CD4 lymphopenia

OBJECTIVES

IL-2 therapy increases memory and naive CD4 T cells in HIV-infected patients, but its effect on thymopoiesis is unknown. To investigate this effect, we quantified T-cell receptor rearrangement excision circles (TREC) in CD4 T cells from lymphopenic AIDS patients treated with highly active antiretroviral therapy and IL-2.

METHODS

CD4 cell subsets were evaluated by flow cytometry using anti-CD45RO/RA, CD62L, Ki67 and CD95 monoclonal antibodies. The proportion of recent thymic emigrant had been quantified by a real-time polymerase chain reaction assay for signal joint TREC in peripheral blood mononuclear and purified CD4 T cells.

RESULTS

At initiation of IL-2, TREC copies/microl of blood were correlated with naive T cell numbers and age. Both naive and TREC numbers/microl significantly increased over time in all patients, with a wide range of TREC increases. Higher percentages of CD4+CD45RO-negative cells positive for the Ki67 cell-cycle marker were found in patients with a low TREC increase, but remained stable under IL-2. TREC and naive cell recovery were correlated; they also correlated with the numbers of TREC and naive cells at the start of IL-2, and with age, suggesting a thymic origin for naive T-cell recovery. A mathematical model showing the linear recovery of naive cells and TREC under IL-2 also strongly suggested that a naive T-cell increase reflects thymic export and involves little net death and proliferation.

CONCLUSION

Although we cannot rule out a mechanism of altered proliferation or death rate, the thymus plays an important role in the long-term recovery of naive T cells under IL-2 therapy.

Immune intervention strategies for HIV-1 infection of humans in the SIV macaque model

Studies in the SIVmac macaque model have demonstrated that the extent of virus-specific CD4+ and CD8+ T-cell responses induced by vaccination prior to virus-challenge exposure correlate with viremia containment following establishment of infection. These findings led to the hypothesis that active immunization with vaccines able to induce virus-specific T-cell responses following the establishment of infection could also ameliorate the virological outcome. Here, we will review the relative effect of ART and vaccination during primary SIVmac infection of macaques.

Systemic immune parameters and sleep after ultra-low dose administration of IL-2 in healthy men

A somnogenic function is suspected for various cytokines. Foregoing experiments in humans indicated a selective increase in the production of interleukin-2 (IL-2) during sleep as compared with nocturnal wakefulness. Here, we examined whether conversely, IL-2 exerts a promoting influence on sleep. Also, the effects of IL-2 administered at ultra-low doses on systemic immune and endocrine parameters were assessed. Eighteen healthy men participated in three night sessions, receiving subcutaneously at 19:00 h either placebo or recombinant human IL-2 at doses of 1000 and 10,000 IU/kg bw. Polysomnographical recordings were obtained between 23:00 and 07:00 h. Blood was collected repeatedly to determine (i) white blood cell (WBC) counts including the enumeration of monocytes, natural killer (NK) cells, and lymphocyte subsets, (ii) serum concentrations of IL-2, soluble IL-2 receptor (sIL-2r), IL-4, IL-6, and interferon-gamma (IFN-gamma), and (iii) concentrations of adrenocorticotropin (ACTH), cortisol, thyreotropin (TSH), and growth hormone (GH). Changes after 1000 IU/kg bw IL-2 generally remained non-significant. However, distinct effects occurred after 10,000 IU/kg bw IL-2, inducing serum IL-2 concentrations selectively activating the high affinity IL-2 receptor. At this dose, IL-2 reduced the number of circulating lymphocytes (including all major subtypes) and NK cells, while counts of monocytes and neutrophils were increased. IL-4 release was stimulated and IFN-gamma concentration reduced after IL-2. Also, IL-2 increased the TSH concentration. There were no hints at a sleep promoting effect of IL-2. Immune changes suggest that nocturnal IL-2 administration induces a shift towards Th2 mediated defense.

Vaccination of macaques with long-standing SIVmac251 infection lowers the viral set point after cessation of antiretroviral therapy

A cohort of rhesus macaques with long-standing SIVmac251 infection (> or =5 mo) was treated with continuous antiretroviral therapy (ART). A group of eight macaques was vaccinated with or without simultaneous administration of low dose IL-2 with the highly attenuated poxvirus vector (NYVAC) vaccine candidate expressing the SIVmac structural gag-pol-env (gpe) genes and a novel chimeric fusion protein derived from the rev-tat-nef (rtn) regulatory genes. Control groups consisted of mock-vaccinated macaques or animals treated only with IL-2. Vaccination significantly expanded both virus-specific CD4(+) and CD8(+) T cell responses, and IL-2 further increased the vaccine-induced response to an immunodominant Gag epitope. Following antiretroviral treatment interruption, the viral set point was significantly lower in vaccinated than in control macaques for at least 4 consecutive mo, and viral containment was inversely correlated with vaccine-induced, virus-specific CD4(+) and CD8(+) T cell responses. These data provide the proof of concept that therapeutic vaccination before cessation of ART may be a feasible approach in the clinical management of HIV-1 infection.

Effects of interleukin-2 plus highly active antiretroviral therapy on HIV-1 replication and proviral DNA (COSMIC trial)

BACKGROUND

The effect of interleukin-2 (IL-2) in combination with antiretroviral therapy on HIV-1 replication and reservoirs was investigated.

METHODS

In a prospective, open-label trial, 56 asymptomatic HIV-1-infected subjects (CD4 T cell count > 350 x 10(6) cells/l) were randomized to highly active antiretroviral therapy (HAART: stavudine, lamivudine, nelfinavir, saquinavir) with or without IL-2 (9 megaunits daily for 5 days in 6-weekly intervals for a total of eight cycles). Productive and latent infection were analysed in peripheral blood, and residual virus replication in the lymphoid tissue and in the cerebrospinal fluid. The influence of IL-2 on viral rebound after treatment discontinuation was studied.

RESULTS

Virus replication was detected in 21 of 31 on-treatment lymph nodes despite undetectable plasma viraemia. Viral RNA was found in resting as well as in proliferating cells. RNA-negative patients tended towards more rapid proviral DNA elimination. Supplementary IL-2 led to a greater increase in CD4 T cell counts than HAART alone (P < 0.001), resulting in normalization in approximately 90% of IL-2-treated patients compared with approximately 50% HAART-only subjects. IL-2 had no beneficial effect on virus replication and on proviral DNA in peripheral blood.

CONCLUSIONS

Viral persistence during HAART is partly a result of continued low-level replication, calling for more active regimens. IL-2 accelerates the normalization of CD4 T cell counts but does not impact on virus production or latency.