Subcutaneous administration of interleukin-2 in human immunodeficiency virus type 1-infected persons

Oncolytic herpes simplex virus expressing IL-2 controls glioblastoma growth and improves survival

BACKGROUND

Glioblastoma (GBM), a highly immunosuppressive and often fatal primary brain tumor, lacks effective treatment options. GBMs contain a subpopulation of GBM stem-like cells (GSCs) that play a central role in tumor initiation, progression, and treatment resistance. Oncolytic viruses, especially oncolytic herpes simplex virus (oHSV), replicate selectively in cancer cells and trigger antitumor immunity-a phenomenon termed the "in situ vaccine" effect. Although talimogene laherparepvec (T-VEC), an oHSV armed with granulocyte macrophage-colony stimulating factor (GM-CSF), is Food and Drug Administration (FDA)-approved for melanoma, its use in patients with GBM has not been reported. Interleukin 2 (IL-2) is another established immunotherapy that stimulates T cell growth and orchestrates antitumor responses. IL-2 is FDA-approved for melanoma and renal cell carcinoma but has not been widely evaluated in GBM, and IL-2 treatment is limited by its short half-life, minimal tumor accumulation, and significant systemic toxicity. We hypothesize that local intratumoral expression of IL-2 by an oHSV would avoid the systemic IL-2-related therapeutic drawbacks while simultaneously producing beneficial antitumor immunity.

METHODS

We developed G47Δ-mIL2 (an oHSV expressing IL-2) using the flip-flop HSV BAC system to deliver IL-2 locally within the tumor microenvironment (TME). We then tested its efficacy in orthotopic mouse GBM models (005 GSC, CT-2A, and GL261) and evaluated immune profiles in the treated tumors and spleens by flow cytometry and immunohistochemistry.

RESULTS

G47Δ-mIL2 significantly prolonged median survival without any observable systemic IL-2-related toxicity in the 005 and CT-2A models but not in the GL261 model due to the non-permissive nature of GL261 cells to HSV infection. The therapeutic activity of G47Δ-mIL2 in the 005 GBM model was associated with increased intratumoral infiltration of CD8+ T cells, critically dependent on the release of IL-2 within the TME, and CD4+ T cells as their depletion completely abrogated therapeutic efficacy. The use of anti-PD-1 immune checkpoint blockade did not improve the therapeutic outcome of G47Δ-mIL2.

CONCLUSIONS

Our findings illustrate that G47Δ-mIL2 is efficacious, stimulates antitumor immunity against orthotopic GBM, and may also target GSC. OHSV expressing IL-2 may represent an agent that merits further exploration in patients with GBM.

Viral Vectors Expressing Interleukin 2 for Cancer Immunotherapy

Interleukin 2 (IL-2) plays a crucial role in T cell growth and survival, enhancing the cytotoxic activity of natural killer and cytotoxic T cells and thus functioning as a versatile master proinflammatory anticancer cytokine. The FDA has approved IL-2 cytokine therapy for the treatment of metastatic melanoma and metastatic renal cell carcinoma. However, IL-2 therapy has significant constraints, including a short serum half-life, low tumor accumulation, and life-threatening toxicities associated with high doses. Oncolytic viruses (OVs) offer a promising option for cancer immunotherapy, selectively targeting and destroying cancer cells while sparing healthy cells. Numerous studies have demonstrated the successful delivery of IL-2 to the tumor microenvironment without compromising safety using OVs such as vaccinia, Sendai, parvo, Newcastle disease, tanapox, and adenoviruses. Additionally, by engineering OVs to coexpress IL-2 with other anticancer transgenes, the immune properties of IL-2 can be further enhanced. Preclinical and clinical studies have shown promising antitumor effects of IL-2-expressing viral vectors, either alone or in combination with other anticancer therapies. This review summarizes the therapeutic potential of IL-2-expressing viral vectors and their antitumor mechanisms of action.

Immune interventions in HIV infection

Immune-based therapy (IBT) interventions have found a window of opportunity within some limitations of the otherwise successful combined antiretroviral therapy (cART). Two major paradigms drove immunotherapeutic research to combat human immunodeficiency virus (HIV) infection. First, IBTs were proposed either to help restore CD4(+) T-cell counts in cases of therapeutic failures with cytokines, interleukin-2 (IL-2) or IL-7, or to better control HIV and disease progression during treatment interruptions with anti-HIV therapeutic candidate vaccines. The most widely used candidates were HIV-recombinant live vector-based alone or combined with other vaccine compounds and dendritic cell (DC) therapies. A more recent and current paradigm aims at achieving HIV cure by combining IBT with cART using either cytokines to reactivate virus production in latently infected cells and/or therapeutic immunization to boost HIV-specific immunity in a 'shock and kill' strategy. This review summarizes the rationale, hopes, and mechanisms of successes and failures of these cytokine-based and vaccine-based immune interventions. Results from these first series of IBTs have been so far somewhat disappointing in terms of clinical relevance, but have provided lessons that are discussed in light of the future combined strategies to be developed toward an HIV cure.

Cytokine therapies in HIV-1 infection: present and future

Since the introduction of highly active antiretroviral therapy (HAART), HIV-related deaths have declined dramatically in the developed world. However, HAART is neither able to eradicate the virus nor are its immunomodulatory effects sufficient to effect complete control of the virus. In addition, the long-term use of HAART is complicated by drug-related toxicities and compliance issues, both of which impact upon the development of viral resistance. The failure of structured treatment interruption strategies in those with chronic HIV-infection combined with the above limitations, has prompted renewed interest in immunotherapy. Cytokines and therapeutic vaccination have been proposed as HAART-adjunctive and HAART-sparing treatments in HIV-infection, and the current and future role of cytokine therapy in this disease will be the subject of this review.

CD8(+) T-cell effector function and transcriptional regulation during HIV pathogenesis

A detailed understanding of the immune response to human immunodeficiency virus (HIV) infection is needed to inform prevention and therapeutic strategies that aim to contain the acquired immunodeficiency syndrome (AIDS) pandemic. The cellular immune response plays a critical role in controlling viral replication during HIV infection and will likely need to be a part of any vaccine approach. The qualitative feature of the cellular response most closely associated with immunological control of HIV infection is CD8(+) T-cell cytotoxic potential, which is responsible for mediating the elimination of infected CD4(+) T cells. Understanding the underlying mechanisms involved in regulating the elicitation and maintenance of this kind of effector response can provide guidance for vaccine design. In this review, we discuss the evidence for CD8(+) T cells as correlates of protection, the means by which their antiviral capacity is evaluated, and transcription factors responsible for their function, or dysfunction, during HIV infection.

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.

Cytokine therapy of tuberculosis at the crossroads

Drug treatment is the key strategy in TB control. However, the treatment course lasts 6-9 months because the current anti-TB drugs are poorly effective against nondividing (i.e., persistent) bacilli. As a result, completion rates are unsatisfactory, leading to emergence and spread of multidrug-resistant infection. It would, therefore, be very desirable to design a form of complementary treatment that could speed up the recovery process for people afflicted with TB and reduce the relapse rates. With the advancement of our understanding of the immunopathogenesis of TB, it has become increasingly possible to develop novel adjunctive immunotherapies for both drug-susceptible and drug-resistant TB. Notably, cytokines probably offer the most promising prospect of such a therapy being introduced in routine clinical practice. However, in many ways, the cytokine therapy of TB has reached a crossroad, since, although the initial promise failed to live up to expectations, sufficient encouraging evidence exists to warrant further exploration. There are clear arguments in favor as well as against such treatments. This review aims to provide a rationale for cytokine treatment of TB, to describe the current status of several cytokines that have been considered for that purpose and, ultimately, to make a case for the need for further clinical trials.

Cytokine production and dysregulation in HIV pathogenesis: lessons for development of therapeutics and vaccines

Numerous studies have characterized the cytokine modulation observed in human immunodeficiency virus (HIV) infected individuals, from initial infection through chronic disease. Progressive and non-progressive HIV infection models show the cytokine milieu differs in terms of production and responsiveness in these two groups, suggesting an understanding of the role cytokines play during infection is necessary for directing the immune response toward viral control. This review will cover cytokine induction and dysfunction during HIV pathogenesis, with a focus on the interplay between cytokines and transcription factors, T cell activation, and exhaustion. We highlight cytokines that have either vaccine adjuvant or therapeutic potential and discuss the need to identify key factors required for prevention of progression, clearance of infection, or protection from acquisition.

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.

Role of interleukin-2 in patients with HIV infection

Control of viral replication to below the level of quantification using combination antiretroviral therapy (ART) [cART] has led to a dramatic fall in mortality and morbidity from AIDS. However, despite the success of cART, it has become apparent that many patients do not achieve normalized CD4+ T-cell counts despite virological suppression to below the level of quantification (<50 copies/mL). Increasing data from cohort studies and limited data from clinical trials, such as the SMART study, have shown that higher CD4+ T-cell counts are associated with reductions in morbidity and mortality from both AIDS and serious non-AIDS (SNA) conditions, including cardiovascular disease. Enhancement of immune restoration over and above that achievable with ART alone, using a number of strategies including cytokine therapy, has been of interest for many years. The most studied cytokine in this setting is recombinant interleukin (IL)-2 (rIL-2). The purpose of this review is to describe the current status of rIL-2 as a therapeutic agent in the treatment of HIV-1 infection. The review focuses on the rationale underpinning the exploration of rIL-2 in HIV infection, summarizing the phase II and III findings of rIL-2 as an adjunctive therapy to ART and the phase II studies of rIL-2 as an antiretroviral-sparing agent. The phase II studies demonstrated the potential utility of continuous intravenous IL-2 and subsequently intermittent dosing with subcutaneous rIL-2 as a cytokine that could expand the CD4+ T-cell pool in HIV-1-infected patients without any significant detrimental effect on HIV viral load and with an acceptable adverse-effect profile. These data were utilized in designing the phase II studies of rIL-2 as an ART-sparing agent and, more importantly, the large phase III clinical endpoint studies of rIL-2 in HIV-1-infected adults, ESPRIT and SILCAAT. In the latter, subcutaneous rIL-2 was given intermittently (5 days of twice-daily dosing at 4.5-7.5 million international units per dose every 8 weeks) to HIV-1-infected adults receiving cART using an induction/maintenance strategy. Both studies explored the clinical benefit of intermittent subcutaneous rIL-2 with cART versus cART in HIV-infected adults with CD4+ T-cell counts > or = 300 cells/microL (ESPRIT study) and 50-299 cells/microL (SILCAAT study). Both studies showed that receipt of rIL-2 conferred no clinical benefit despite a significantly higher CD4+ T-cell count in the rIL-2 arms of both studies. Moreover, there was an excess of grade 4 clinical events in ESPRIT rIL-2 recipients. The results of the phase III clinical endpoint studies showed that rIL-2 has no place as a therapeutic agent in the treatment of HIV infection.

IL-2 immunotherapy to recently HIV-1 infected adults maintains the numbers of IL-17 expressing CD4+ T (T(H)17) cells in the periphery

Little is known about the manipulation of IL-17 producing CD4+ T cells (T_H17) on a per-cell basis in humans in vivo. Previous studies on the effects of IL-2 on IL-17 secretion in non-HIV models have shown divergent results. We hypothesized that IL-2 would mediate changes in IL-17 levels among recently HIV-1-infected adults receiving anti-retroviral therapy. We measured cytokine T cell responses to CD3/CD28, HIV-1 Gag, and CMV pp65 stimulation, and changes in multiple CD4+ T cell subsets. Those who received IL-2 showed a robust expansion of naive and total CD4+ T cell counts and T-reg counts. However, after IL-2 treatment, the frequency of T_H17 cells declined, while counts of T_H17 cells did not change due to an expansion of the CD4+ naïve T cell population (CD27+CD45RA+). Counts of HIV-1 Gag-specific T cells declined modestly, but CMV pp65 and CD3/CD28 stimulated populations did not change. Hence, in contrast with recent studies, our results suggest IL-2 is not a potent in vivo regulator of T_H17 cell populations in HIV-1 disease. However, IL-2-mediated T-reg expansions may selectively reduce responses to certain antigen-specific populations, such as HIV-1 Gag.

Impact of gamma-chain cytokines on T cell homeostasis in HIV-1 infection: therapeutic implications

CD4(+) T cell lymphocytes are a major target for human immunodeficiency virus type-1 (HIV-1) infection. During this chronic infection, CD4(+) T cell loss (induced through direct viral replication), generalized immune activation and increased susceptibility to apoptosis result in impaired T cell homeostasis with subsequent development of opportunistic infections and cancers. Highly active antiretroviral therapy (HAART) has a well-defined, beneficial effect on HIV-1-related clinical outcome; however, it does not lead to normalization of immune dysregulation. In order to boost both CD4(+) T cell restoration and HIV-1 specific immunity, immunotherapy with gamma-chain cytokines has been used in HIV-1-infected patients during concomitant HAART. In this review, we summarize the role of gamma-chain cytokines, especially interleukin (IL)-2 and IL-7, in influencing T cell homeostasis and proliferation, and discuss how immunotherapy with these cytokines may be beneficial to reconstitute the T cell compartment in the context of HIV-1 infection. The intriguing results of two large trials evaluating the efficacy of IL-2 in restoring immune function during HIV-1 infection are also discussed. In addition, we consider the promises and caveats of the first phase I/II clinical trials with IL-7 in HIV-1-infected patients and the knowledge that is still lacking in the field of T cell reconstitution through gamma-chain cytokines.

Effects of intermittent IL-2 alone or with peri-cycle antiretroviral therapy in early HIV infection: the STALWART study

Background

The Study of Aldesleukin with and without antiretroviral therapy (STALWART) evaluated whether intermittent interleukin-2 (IL-2) alone or with antiretroviral therapy (ART) around IL-2 cycles increased CD4⁺ counts compared to no therapy.

Methodology

Participants not on continuous ART with ≥300 CD4⁺ cells/mm³ were randomized to: no treatment; IL-2 for 5 consecutive days every 8 weeks for 3 cycles; or the same IL-2 regimen with 10 days of ART administered around each IL-2 cycle. CD4⁺ counts, HIV RNA, and HIV progression events were collected monthly.

Principal Findings

A total of 267 participants were randomized. At week 32, the mean CD4⁺ count was 134 cells greater in the IL-2 alone group (p<0.001), and 133 cells greater in the IL-2 plus ART group (p<0.001) compared to the no therapy group. Twelve participants in the IL-2 groups compared to 1 participant in the group assigned to no therapy experienced an opportunistic event or died (HR 5.84, CI: 0.59 to 43.57; p = 0.009).

Conclusions

IL-2 alone or with peri-cycle HAART increases CD4⁺ counts but was associated with a greater number of opportunistic events or deaths compared to no therapy. These results call into question the immunoprotective significance of IL-2-induced CD4⁺ cells.

Trial Registration

ClinicalTrials.gov NCT00110812

Immunotherapies in HIV-1 infection

PURPOSE OF REVIEW

The purpose of this review is to describe the current status of immunotherapies for the treatment of HIV-1 infection. This review is timely, as the results of the phase III clinical trials of recombinant interleukin-2 (rIL-2) as adjuncts to combination antiretroviral therapy are about to be released.

RECENT FINDINGS

For many years, the use of rIL-2 in HIV-infected individuals has been explored. Although the results of the clinical endpoint studies of rIL-2 are awaited, there are now further data for rIL-2 as a stand-alone therapy for the treatment of HIV. Maraviroc, a recently approved anti-HIV agent, is a small molecule antagonist of human chemokine receptor-5. The recent observation that maraviroc-treated patients achieved higher CD4 and CD8 T-cell counts compared with comparator regimens (without a chemokine receptor-5 antagonist) for equivalent viral load reductions has fueled interest in using these host-directed therapies to enhance immune restoration.

SUMMARY

This review summarizes the most recent clinical data for rIL-2 and reviews other immunotherapies in earlier development including cytokines rIL-7, rIL-15, rIL-21, new therapeutic vaccination approaches including infusion of overlapping HIV peptides and dendritic cell immunotherapy and novel agents including luteinizing hormone-releasing hormone analogues and vitamin D3-binding protein macrophage activating factor.

Inferiority of IL-2 alone versus IL-2 with HAART in maintaining CD4 T cell counts during HAART interruption: a randomized controlled trial

OBJECTIVE

To evaluate whether interleukin (IL)-2 in patients with chronic HIV infection can maintain CD4 T cell counts during 6 months of HAART interruption.

DESIGN

Prospective, randomized, controlled, open-label phase II noninferiority trial comparing IL-2 with HAART interruption or continuous HAART.

METHODS

Forty-one IL-2-experienced (three or more prior cycles) HIV-1-infected adults with CD4 cell count at least 500 cells/microl were randomized in the ratio 2: 1 to interrupted (I = 27) or continuous (C = 14) HAART for 6 months following an initial IL-2 cycle. Subsequent IL-2 cycles were triggered by CD4 T cell counts less than 90% of baseline. Immune, metabolic, and quality of life indices were compared (Mann-Whitney and Fisher's exact tests), defining noninferiority as a percentage difference (C- I) in treatment success (CD4 T cells > or =90% of baseline at 6 months) with a 95% confidence interval (CI) lower limit greater than -20%.

RESULTS

Demographic and immune parameters were similar between the groups at baseline. Median CD4 T cell count, HIV viral load, and treatment success differed significantly at 6 months (I: 866 cells/microl, 39,389 copies/ml, 48.1%; C: 1246 cells/microl, <50 copies/ml, 92.3%; P < or = 0.001). Group I was inferior to C (% difference = -44.2%; 95% CI: -64.2%, -11.2%; P = 0.013). Minor statistically significant differences in HgbA1c and energy level occurred at 6 months (I > C). Following HAART interruption, single cases of acute retroviral syndrome, secondary syphilis, non-Hodgkin's lymphoma, and Kaposi's sarcoma recurrence were observed.

CONCLUSION

IL-2 alone was inferior to IL-2 with HAART in maintaining baseline CD4 T cell counts. HAART interruption had a small impact on metabolic parameters and quality of life.

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.

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.

Predictors of CD4 count change over 8 months of follow up in HIV-1-infected patients with a CD4 count>or=300 cells/microL who were assigned to 7.5 MIU interleukin-2

BACKGROUND

ESPRIT is a randomized trial comparing the clinical impact of interleukin (IL)-2 plus antiretrovirals vs antiretrovirals alone. Identification of factors that influence the relationship between IL-2 and CD4 count recovery will enable better personalization of treatment with IL-2 in HIV-1-positive individuals. The IL-2 induction phase consists of three dosing cycles over 6-8 months (7.5 MIU twice a day, for 5 days every 8 weeks).

METHODS

We included patients initiating IL-2 at the 7.5 MIU dose with an 8-month CD4 count, measured at least 30 days after their last cycle. We identified baseline predictors of CD4 count changes over 8 months using linear regression.

RESULTS

Of 2090 patients assigned IL-2, 1673 (80%) were included in the analysis. The median (interquartile range) baseline CD4 count was 461 (370, 587) cells/microL with a median increase of 233 (90, 411) cells/microL at month 8. After adjustments, significant predictors of CD4 count change included CD4 nadir (29.8 cells/microL greater increase per 100 cells/microL higher; P<0.0001), last CD4 count before baseline (mean 36.0 cells/microL greater increase per 100 cells/microL higher; P<0.0001), time from antiretroviral start to baseline (8.3 cells/microL smaller increase per year longer; P=0.001), age (11.7 cells/microL smaller increase per 5 years older; P=0.005) and race (79.7 cells/microL greater increase for black patients vs white patients; P=0.003). A linear relationship existed between total IL-2 dose in the first cycle and CD4 count change (73.1 cells/microL greater increase per 15 MIU higher; P<0.0001).

CONCLUSIONS

Prior nadir and current CD4 counts, age and IL-2 dose are major determinants of CD4 increases induced by with intermittent administration of IL-2 in HIV-1-positive individuals on antiretrovirals. The clinical function of these induced CD4 cells is under study.

Long-term effects of intermittent interleukin-2 therapy in chronic HIV-infected patients (ANRS 048-079 Trials)

OBJECTIVE

Interleukin (IL)-2 therapy leads to significant CD4 cell increases in HIV-infected patients. Since phase III trials are ongoing, studies supporting the long-term feasibility of this strategy are needed.

METHODS

We studied the long-term outcomes of 131 patients treated with IL-2 in two studies initiated either before (ANRS 048) or following (ANRS 079) the advent of HAART.

RESULTS

At the last assessment (median follow-up 3.4 years), these patients experienced a gain of 428 cells/microl and a decrease in plasma HIV RNA to 1.70 log10 copies/ml. In both studies, high CD4 cell counts were maintained with a median of ten 5-day cycles of subcutaneous IL-2. Median time since the last cycle was 2 years. At last assessment, 59% of 048 patients maintained a non-HAART regimen. Detailed analysis at week 170 showed that median CD4 cell counts were 856 (048) and 964 (079) cells/microl. This corresponded to a gain from baseline of 515 (048) and 627 (079) cells/microl. The median viral load decreases from baseline and corresponded to 1.70 (048) and 1.88 (079) log10 copies/ml. Comparisons across the studies showed that CD4 gains and viral load changes were similar whether HAART or non-HAART was used. The frequency of cycling, but not CD4 cell counts, viral loads or antiviral regimen at baseline, was predictive of long-term CD4 gain (P = 0.03).

CONCLUSION

Altogether, these observations support IL-2 as a long-term therapeutic strategy in HIV infection.

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.

A phase I, randomized study of combined IL-2 and therapeutic immunisation with antiretroviral therapy

Background

Fully functional HIV-1-specific CD8 and CD4 effector T-cell responses are vital to the containment of viral activity and disease progression. These responses are lacking in HIV-1-infected patients with progressive disease. We attempted to augment fully functional HIV-1-specific CD8 and CD4 effector T-cell responses in patients with advanced chronic HIV-1 infection.

Design

Chronically infected patients with low CD4 counts T-cell counts who commenced antiretroviral therapy (ART) were subsequently treated with combined interleukin-2 and therapeutic vaccination.

Methods

Thirty six anti-retroviral naive patients were recruited and initiated on combination ART for 17 weeks before randomization to: A) ongoing ART alone; B) ART with IL-2 twice daily for 5 days every four weeks starting at week 17 for 3 cycles; C) ART with IL-2 as in group B and Remune HIV-1 vaccine administered once every 3 months, starting at week 17; and D) ART with Remune vaccine as in group C. Patients were studied for 65 weeks following commencement of ART, with an additional prior 6 week lead-in observation period. CD4 and CD8 T-cell counts, evaluations of HIV-1 RNA levels and proliferative responses to recall and HIV-1 antigens were complemented with assessment of IL-4-secretion alongside quantification of anti-HIV-1 CD8 T-cell responses and neutralizing antibody titres.

Results

Neither IL-2 nor Remune™ vaccination induced sustained HIV-1-specific T-cell responses. However, we report an inverse relationship between HIV-1-specific proliferative responses and IL-4 production which continuously increased in patients receiving immunotherapy, but not patients receiving ART alone.

Conclusion

Induction of HIV-1-specific cell-mediated responses is a major challenge in chronically HIV-1-infected patients even when combining immunisation with IL-2 therapy. An antigen-specific IL-4-associated suppressive response may play a role in attenuating HIV-specific responses.

[Cytokine therapies in HIV infection]

The theoretical objectives of cytokine therapies in HIV infection are to impact T cell homeostasis and/or to improve immune functions or the mobilization of the HIV reservoir. Among cytokines, IL-2 and IL-7 are promising agents under clinical evaluation. Intermittent administration of IL-2 is by far the furthest studied strategy in HIV infection. This cytokine increases CD4 T lymphocytes in HIV-infected individuals. Recent clinical data showed that this effect is sustained over years. IL-2 therapy induces a peripheral expansion of T cells as a consequence of prolonged survival of T cells and decreased immune activation. These effects suggest that a cytokine therapy may interfere with critical factors of HIV disease. Recent data provide arguments that IL-2 therapy improves immune functions in HIV-infected patients. Whether these effects may be translated into clinical benefits is under evaluation in ongoing phase III studies. The potential interest of IL-7 in the treatment of HIV-infection is based on its crucial role on T cell homeostasis both in thymic output and peripheral T proliferation and survival. Although no data in human are still available, recent studies provide arguments to assess this cytokine in HIV infection. Phase I studies are ongoing or planned.

A randomised trial of subcutaneous intermittent interleukin-2 without antiretroviral therapy in HIV-infected patients: the UK-Vanguard Study

Objective:

The objective of the trial was to evaluate in a pilot setting the safety and efficacy of interleukin-2 (IL-2) therapy when used without concomitant antiretroviral therapy as a treatment for HIV infection.

Design and Setting:

This was a multicentre randomised three-arm trial conducted between September 1998 and March 2001 at three clinical centres in the United Kingdom.

Participants:

Participants were 36 antiretroviral treatment naïve HIV-1-infected patients with baseline CD4 T lymphocyte counts of at least 350 cells/mm³.

Interventions:

Participants were randomly assigned to receive IL-2 at 15 million international units (MIU) per day (12 participants) or 9 MIU/day (12 participants) or no treatment (12 participants). IL-2 was administered by twice-daily subcutaneous injections for five consecutive days every 8 wk.

Outcome Measures:

Primary outcome was the change from baseline CD4 T lymphocyte count at 24 wk. Safety and plasma HIV RNA levels were also monitored every 4 wk through 24 wk. The two IL-2 dose groups were combined for the primary analysis.

Results:

Area under curve (AUC) for change in the mean CD4 T lymphocyte count through 24 wk was 129 cells/mm³ for those assigned IL-2 (both dose groups combined) and 13 cells/mm³ for control participants (95% CI for difference, 51.3–181.2 cells/mm³; p = 0.0009). Compared to the control group, significant increases in CD4 cell count were observed for both IL-2 dose groups: 104.2/mm³ (p = 0.008) and 128.4 cells/mm³ (p = 0.002) for the 4.5 and 7.5 MIU dose groups, respectively. There were no significant differences between the IL-2 (0.13 log₁₀ copies/ml) and control (0.09 log₁₀ copies/ml) groups for AUC of change in plasma HIV RNA over the 24-wk period of follow-up (95% CI for difference, −0.17 to 0.26; p = 0.70). Grade 4 and dose-limiting side effects were in keeping with those previously reported for IL-2 therapy.

Conclusions:

In participants with HIV infection and baseline CD4 T lymphocyte counts of at least 350 cells/mm³, intermittent subcutaneous IL-2 without concomitant antiretroviral therapy was well tolerated and produced significant increases in CD4 T lymphocyte counts and did not adversely affect plasma HIV RNA levels.

Background: There is very good trial evidence that combinations of antiretroviral drugs improve the prognosis of people with HIV infection. However, these drugs can have major side effects, and HIV can become resistant to them. The development of alternative treatments might allow antiretroviral use to be delayed in some people, thereby reducing toxicity and the emergence of resistant strains of HIV.

What this trial shows: The researchers studied 36 adult patients in the United Kingdom who were infected with HIV and who had not previously been prescribed antiretrovirals. Participants in the trial were given either one of two different dosage levels of IL-2 (a chemical messenger normally produced in the body by particular immune cells) by injection under the skin or no treatment at all. Patients given IL-2 at either dosage experienced an increase in levels of CD4 T lymphocytes, the type of immune cell depleted by HIV infection, as compared to patients receiving no treatment. The viral load in patients receiving IL-2 did not differ from that of patients in the control arm.

Strengths and limitations: The rationale for this trial—to delay administration of antiretroviral drugs—is sound, as is the experimental design. The results are limited, however, by the short follow-up of patients in the trial and by the lack of clinical endpoints (such as disease progression), so it is not possible to tell whether patients in the trial benefited directly from the IL-2 treatment.

Contribution to the evidence: The clinical effectiveness and safety of IL-2 together with antiretrovirals as a treatment for HIV infection is currently being evaluated in other, large-scale trials. To date, no other study has assessed the outcomes arising from administration of IL-2 alone. Data from the current trial will be useful in planning further research to examine whether IL-2 might help delay antiretrovirals in HIV-positive people.

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.

Effect of IL-2 therapy on CD8+ cell noncytotoxic anti-HIV response during primary HIV-1 infection

Early treatment intervention during human immunodeficiency virus (HIV) infection is a strategy aimed to preserve and/or enhance the developing anti-HIV immune responses. We report the effect of highly active antiretroviral therapy (HAART) combined with intermittent subcutaneous doses of Interleukin 2 (IL-2) on CD8(+) cell noncytotoxic anti-HIV responses (CNAR), as well as on viral loads and CD4(+) cell/CD8(+) cell numbers in subjects with primary HIV-1 infection. Twenty-four patients received HAART, 24 received a combination of HAART plus IL-2, and 12 elected no-therapy. In comparison to HAART alone, IL-2 treatment led to significant increases in CD4(+) cell numbers through week 48 of the study. No effect was observed on viral loads or the CD8(+) cell population. The first cycle of IL-2 enhanced CNAR; later cycles showed no substantial effect. This study suggests that HAART combined with IL-2 could provide an immunologic benefit in the treatment of early HIV infection.

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.

Tetanus vaccination with IL-2 during highly active antiretroviral therapy induces sustained and pronounced specific CD4 T-cell responses

HIV-1 infection results in profound dysfunction of the CD4 T-cell population. Although highly active antiretroviral therapy allows the reconstitution of CD4 T-cell numbers, functional abnormalities remain, including inadequate responses to vaccination. IL-2 increases CD4 T-cell numbers and function. We report the effects of IL-2 given with tetanus vaccination in two patients in a larger immunotherapy study. In one case IL-2 induced sustained responses, which may have been caused by the timing of IL-2 with vaccination.

Induction and maintenance therapy with intermittent interleukin-2 in HIV-1 infection

Studies establishing that intermittent subcutaneous interleukin-2 (IL-2) therapy can lead to substantial CD4 cell increases in many HIV-infected patients have generally been of limited duration. We studied 77 patients participating in active longitudinal studies of subcutaneous IL-2 therapy at our center in order to determine the long-term feasibility of this approach. Following initial induction, patients in each trial were eligible to receive intermittent 5-day cycles of subcutaneous IL-2 treatment at individualized doses and frequencies capable of maintaining CD4 counts at postinduction levels. The mean duration of study participation to date is 5.9 years (range, 1.0-9.3 years). Mean baseline CD4 cell count and CD4 percent values of 0.521 × 109/L (521 cells/μL) and 27% have risen to 1.005 × 109/L (1005 cells/μL) and 38%, respectively, at 90 months. The mean number of subcutaneous IL-2 cycles required to achieve and maintain these increases was 10 cycles (range, 3-29 cycles), and the current mean interval of cycling required to maintain these elevations is 39 months (median, 35 months; range, 2-91 months). We conclude that subcutaneous IL-2 therapy is capable of maintaining CD4 cell increases for an extended period using a remarkably low frequency of intermittent cycling. These observations may contribute to patients' acceptance of subcutaneous IL-2 as a favorable long-term treatment strategy. (Blood. 2004;103:3282-3286)

Il-7/Il-7 Receptor System Regulation following Il-2 Immunotherapy in HIV-Infected Patients

Interleukin-2 (IL-2) and IL-7 are the most intriguing molecules in immune-based HIV infection treatment. An in vitro IL-2/IL-7 cross-talk due to IL-2-driven IL-7 receptor-α-chain (IL-7Rα) down-modulation, potentially blocking IL-7 signalling has been described. We investigated the in vivo IL-2 effect on IL-7/IL-7R system, measuring free IL-7, and IL-7Rα CD4 and CD8 in 12 HIV-positive patients enrolled in a randomized IL-2 trial.

Compared to HAART alone, IL-2 induced a parallel expansion in total and naive CD4, TRECs and IL-7 plasma levels, with no IL-7Rα CD4 and IL-7Rα CD8 changes ( P>0.05), suggesting that in vivo IL-2 boosts IL-7 production without down-modulating IL-7Rα, preserving IL-7-mediated T-lymphocyte homeostatic regulation. Our data confirm the pivotal role of IL-2 and IL-7 in the regulation of T-lymphocyte homeostasis in HIV infection.

Early correction of cell cycle perturbations predicts the immunological response to therapy in HIV-infected patients

OBJECTIVE

To determine whether changes in the indices of HIV-associated cell cycle dysregulation (i.e., increased expression of cyclin B1 and abnormal nucleolar structure) may predict the level of immunological reconstitution in HIV-infected patients treated with highly active antiretroviral therapy (HAART).

METHODS

Cross-sectional and longitudinal analysis of viral load, CD4 T cell counts, cyclin B1 expression, and AgNOR number and area of distribution in 30 HIV-infected patients who were studied before and up to 6 months after initiation of HAART.

RESULTS

In HIV-infected individuals, the level of cell cycle dysregulation correlated with the type of response to HAART. While low levels of dysregulation were present in patients with complete (both virological and immunological) response to HAART, high levels were present in HAART-treated patients with limited CD4 T cell increases despite persistent viral suppression (immunological non-responders). Importantly, the level of correction of cell cycle dysregulation after 60 days of therapy predicted the level of immune reconstitution after 6 months.

CONCLUSION

These observations suggest that correction of cell cycle dysregulation predicts a good immunological response to HAART and that sequential analysis of cell cycle dysregulation might help to identify patients that could benefit from alternative, immune-based interventions in addition to standard HAART.

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?

Nadir CD4+ T Cell Count Predicts Response to Subcutaneous Recombinant Interleukin-2

Community Program for Clinical Research on AIDS 059 was a multicenter study conducted among human immunodeficiency virus (HIV)-infected individuals with CD4+ cell counts > or =300 cells/mm3 who were randomly assigned to receive antiretroviral therapy with or without intermittent subcutaneously administered recombinant interleukin-2 (rIL-2). To identify factors associated with a response to IL-2, a secondary analysis was performed that included the subset of rIL-2 recipients who were able to complete all 3 initial treatment cycles. Predictors of a change in CD4+ cell count between baseline and 1 month after the start of treatment cycle 3 were examined in a multivariate model that included sex, race, body surface area, rIL-2 dose, HIV load, and both baseline and nadir CD4+ cell count. The combination of race and sex (P=.027) and the nadir CD4+ cell count (P=.005) were significant predictors of mean CD4+ cell count response. Baseline CD4+ cell count had no significant effect. The strong association between nadir CD4+ cell count and CD4+ cell count response suggests that immunologic losses resulting from HIV-mediated CD4+ cell depletion may be irreversible.

Identification of a protein fragment of interleukin 2 responsible for vasopermeability

BACKGROUND

The cytokine interleukin 2 (IL-2) is involved in the activation of T cells and has been shown to play a central role in cancer immunotherapy. The full therapeutic potential of IL-2, however, has not been realized because of its dose-limiting systemic toxicity. We sought to identify a region of IL-2 that is responsible for the induction of vasopermeability (leaky tumor endothelium), a property associated with the toxicity of the molecule.

METHODS

Intact IL-2 or overlapping synthetic peptides of IL-2 that were chemically conjugated to tumor-targeting monoclonal antibodies (TNT-1 or Lym-1) were injected into groups of mice (n = 4) that had previously been xenotransplanted with human tumor cells (ME-180 cervical carcinoma and Raji lymphoma). Two hours later, mice received intravenous injections of radiolabeled tracer antibody, and 3 days later they were subjected to biodistribution analysis to measure the ability of each immunoconjugate to enhance tumor uptake of the tracer antibody (i.e., vasopermeability activity). The cytokine activity of the immunoconjugates was determined by assaying their ability to promote the proliferation of a mouse IL-2-dependent cell line.

RESULTS

Pretreatment of mice with an antibody/IL-2 immunoconjugate resulted in an approximately fourfold increase in radiolabeled tracer antibody uptake in the xenograft tumor as compared with uptake in mice injected with antibody alone. One synthetic fragment consisting of amino acids 22-58 contained 100% of the vasopermeability activity of IL-2 and was designated permeability-enhancing peptide (PEP). PEP had vasopermeability activity only when conjugated to a tumor-targeting antibody, had maximal activity as a dimer, and was devoid of cytokine activity.

CONCLUSIONS

The identification of PEP should aid in the discovery of ways to decrease the toxicity of IL-2. Moreover, PEP is a promising candidate for the generation of agents that can enhance the delivery of antibodies and drugs to tumors.

A randomized controlled trial evaluating the efficacy and safety of intermittent 3-, 4-, and 5-day cycles of intravenous recombinant human interleukin-2 combined with antiretroviral therapy (ART) versus ART alone in HIV-seropositive patients with 100-300 CD4+ T cells

The effect of length of therapy on the safety and efficacy profile of continuous intravenous (CIV) interleukin-2 (IL-2) in combination with antiretroviral therapy (ART) was evaluated in 81 HIV-seropositive patients with CD4(+) T-cell counts of 100-300/mm(3). Patients were randomized to CIV IL-2 (12 mIU/day) for 3, 4, or 5 days plus ART every 8 weeks for six cycles, or to ART alone. The mean percent increase in CD4(+) T-cell counts was 24.5% for IL-2 recipients compared with a mean percent decrease of 30.5% for control patients (P = 0.005). Increasing duration of CIV IL-2 therapy resulted in improved CD4(+) T-cell response. The most frequent clinical adverse events and laboratory abnormalities were predominantly of grade 1 or 2 severity. However, grade 3 or 4 events were reported in 57%, 60%, and 84% of the 3-, 4-, and 5-day CIV IL-2 patients, respectively. Serious adverse events, mainly due to the requirement of hospitalization, occurred in 20% of IL-2 recipients, compared with 10% of control patients. Viral load during the course of the study was not different among the treatment groups. IL-2 therapy in cycles of 5 days resulted in an optimal increase in CD4(+) T-cell counts and is the preferred cycle length for IL-2 therapy geared toward increasing CD4(+) T-cell numbers.

Effects of interleukin-2 therapy combined with highly active antiretroviral therapy on immune restoration in HIV-1 infection: a randomized controlled trial

BACKGROUND

Intermittent interleukin-2 (IL-2) therapy leads to a sustained increase of CD4 T cells in HIV-1-infected patients.

METHODS

Symptom-free HIV-1-infected patients who were naive to all antiretroviral drugs (n = 68) and/or to protease inhibitors (n = 50) and had a CD4 cell count of 200-550 x 10(6) cells/l were randomly assigned to start lamivudine/stavudine/indinavir alone (controls) or combined from week 4 with subcutaneous IL-2 (5 x 10(6) IU twice daily for 5 days: every 4 weeks for three cycles, then every 8 weeks for seven cycles). Immunological and virological results were monitored until week 74.

RESULTS

CD4 T cell counts increased more in the IL-2 group than in the controls (median increases 865 and 262 x 10(6) cells/l, respectively; P < 0.0001); an 80% increase in CD4 T cells was achieving by 89% of the IL-2 group and by 47% of the controls (P < 0.0001). Decrease of plasma viral loads was similar in both groups. Compared with controls, IL-2 induced a greater increase of naive and memory CD4 T cells, lymphocyte expression of CD28 and CD25 (P < 0.0001) and natural killer cells (P < 0.001). In a logistic regression analysis, odds of being responders to recall antigens was 8.5-fold higher in IL-2 recipients (P = 0.002) than in controls. The former experienced a higher level of antibody response to tetanus vaccination at week 64 than controls (32 and 8 haemagglutinating units/ml, respectively; P = 0.01).

CONCLUSIONS

The combination of antiviral drugs and IL-2 induced a greater expansion and function of CD4 T cells than antiretroviral drugs alone.

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.

Lymphoid activation: a confounding factor in AIDS vaccine development?

In a previous vaccination trial, inoculation of env gene DNA failed to elicit a detectable antibody response, yet accelerated virus dissemination in most immunized cats following challenge with feline immunodeficiency virus. This result raised the possibility that cell-mediated immune responses had given rise to immune-mediated enhancement of infection. Since high-level replication of immunodeficiency viruses in lymphocytes requires cellular activation, antigen-specific responses or non-specific polyclonal activation may have increased the frequency of optimal target cells. In the present DNA vaccination trial, although designed so as to minimize non-specific polyclonal activation, immune-mediated enhancement was nonetheless observed in certain immunized cats. Moreover, rapid virus dissemination in vivo was associated with the presence of T-helper responses prior to challenge, and was linked to increased susceptibility of lymphocytes to ex vivo infection. Immune activation may thus be a confounding factor in vaccination against lentivirus infection, diminishing vaccine efficacy and giving rise to immune-mediated enhancement.

Long-term effects of intermittent interleukin 2 therapy in patients with HIV infection: characterization of a novel subset of CD4+/CD25+ T cells

The long-term immunologic effects of intermittent interleukin 2 (IL-2) therapy were evaluated in a cross-sectional study by comparing 3 groups: HIV-seronegative volunteers, HIV-infected (HIV+) patients receiving highly active antiretroviral therapy (HAART), and HIV+ patients receiving HAART and intermittent IL-2. Whole-blood immunophenotyping was performed to study expression of the IL-2 receptor chains on T lymphocytes and natural killer cells and to further characterize CD4+/CD25+ T cells. Increased CD25 expression, especially in CD4+ T cells but also in CD8+ T cells, without increases in expression of the β and γ chains of the IL-2 receptor was detected in the IL-2 group. Up to 79% of naive CD4+ T cells (median, 61%) from patients in the IL-2 group expressed CD25, and the number of naive CD4+/CD25+ T cells correlated positively with both the total and naive CD4+ T-cell counts. A discrete population of CD45 double intermediate RA+/RO+CD4+ cells was also preferentially expanded in the IL-2 group, and the number of these cells strongly correlated with the total CD4+ count. Despite increases in CD25 expression, T lymphocytes from patients treated with IL-2 did not have increased expression of early (CD69) or late (CD95) activation markers or evidence of recent proliferation (Ki67). Both CD4+/CD25+ and CD4+/CD25− cells from IL-2–treated HIV+ patients proliferated in response to mitogens, specific antigens, and T-cell-receptor–mediated stimuli. Thus, intermittent administration of IL-2 in HIV+ patients leads to preferential expansion of a unique subset of CD4+ T cells that may represent a critical population in T-cell homeostasis.

Long-term effects of intermittent interleukin 2 therapy in patients with HIV infection: characterization of a novel subset of CD4+/CD25+ T cells

The long-term immunologic effects of intermittent interleukin 2 (IL-2) therapy were evaluated in a cross-sectional study by comparing 3 groups: HIV-seronegative volunteers, HIV-infected (HIV+) patients receiving highly active antiretroviral therapy (HAART), and HIV+ patients receiving HAART and intermittent IL-2. Whole-blood immunophenotyping was performed to study expression of the IL-2 receptor chains on T lymphocytes and natural killer cells and to further characterize CD4+/CD25+ T cells. Increased CD25 expression, especially in CD4+ T cells but also in CD8+ T cells, without increases in expression of the β and γ chains of the IL-2 receptor was detected in the IL-2 group. Up to 79% of naive CD4+ T cells (median, 61%) from patients in the IL-2 group expressed CD25, and the number of naive CD4+/CD25+ T cells correlated positively with both the total and naive CD4+ T-cell counts. A discrete population of CD45 double intermediate RA+/RO+CD4+ cells was also preferentially expanded in the IL-2 group, and the number of these cells strongly correlated with the total CD4+ count. Despite increases in CD25 expression, T lymphocytes from patients treated with IL-2 did not have increased expression of early (CD69) or late (CD95) activation markers or evidence of recent proliferation (Ki67). Both CD4+/CD25+ and CD4+/CD25− cells from IL-2–treated HIV+ patients proliferated in response to mitogens, specific antigens, and T-cell-receptor–mediated stimuli. Thus, intermittent administration of IL-2 in HIV+ patients leads to preferential expansion of a unique subset of CD4+ T cells that may represent a critical population in T-cell homeostasis.

Increased peripheral expansion of naive CD4+ T cells in vivo after IL-2 treatment of patients with HIV infection

Intermittent interleukin-2 (IL-2) therapy has been shown to increase the number of CD4+ T cells, preferentially cells with a naive phenotype, in patients with HIV infection. For this report we investigated the mechanism underlying this expansion by studying the relative roles of peripheral expansion and thymic output. In a cohort of six patients receiving IL-2 over a period of 1 year, the mean number of naive CD4+ T cells increased from 139 to 387 cells per microl while levels of T cell receptor rearrangement excision circles (TRECs) declined from 47,946 to 26,510 copies per 10(6) naive T cells, thus making it unlikely that the CD4+ T cell count increases were secondary to increase in thymic output. To examine directly the impact of IL-2 on peripheral expansion, peripheral blood mature, naive CD4+ T cells were labeled ex vivo with 5-bromodeoxyuridine as well as stained directly for Ki67. These studies revealed a 7-fold increase in the percentage of 5-bromodeoxyuridine-positive cells and a 20-40-fold increase in Ki67 staining in the naive CD4+ T cell pool in the setting of IL-2 administration. This degree of increase in mature CD4+ T cell turnover induced by IL-2 does not compromise the future replicative potential of these cells, because longitudinal measurements of telomere length went from 6,981 to 7,153 bp after 1 year of IL-2 therapy. These data strongly suggest that much of the increase in CD4+ cells associated with IL-2 treatment is caused by peripheral expansion of existing naive CD4+ T cells rather than increased thymic output and that these increases occur without compromising the potential of these cells for further cell division.

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.

Tumor necrosis factor alpha, interleukin 2, and soluble interleukin 2 receptor levels in human immunodeficiency virus type 1-infected individuals receiving intermittent cycles of interleukin 2

HIV-infected individuals with 200-500 CD4(+) T cell/microl were enrolled in a controlled study of three interleukin 2 (IL-2) plus antiretroviral therapy (ART) regimens: (1) continuous intravenous administration of 12 million international units (MIU) of IL-2 followed by subcutaneous high-dose IL-2 (7.5 MIU, twice daily) for 5 days every 8 weeks; (2) high-dose subcutaneous IL-2 for 5 days every 8 weeks; (3) low-dose (3 MIU, twice daily) subcutaneous IL-2 for 5 days every 4 weeks; and (4) ART alone. Serum concentrations of IL-2, soluble IL-2 receptor (sIL-2R), tumor necrosis factor alpha (TNF-alpha), and IL-6 were determined. A progressive decrease over time of the circulating levels of IL-2 was observed in individuals receiving the highest doses of IL-2, but not in those belonging to the low-dose arm. Conversely, increased levels of sIL-2R were observed in all cytokine-treated individuals. The levels of TNF-alpha increased in the high-dose IL-2 regimens, but decreased in individuals receiving low-dose IL-2. IL-2-related toxicity was significantly correlated to the peak IL-2 serum levels, and was substantially lower in those individuals receiving low-dose IL-2. In conclusion, intermittent IL-2 administration causes the elevation of peripheral CD4(+) T cells, but also a profound cytokine response and systemic toxicity. The latter was correlated to the peak serum level of IL-2, but not to those of TNF-alpha and IL-6.