Kinetics of lymphokine production in HIV+ patients treated with highly active antiretroviral therapy and interleukin 2

Phase I clinical trial combining imatinib mesylate and IL-2: HLA-DR+ NK cell levels correlate with disease outcome

We performed a Phase I clinical trial from October 2007 to October 2009, enrolling patients affected by refractory solid tumors, to determine the maximum tolerated dose (MTD) of interleukin (IL)-2 combined with low dose cyclophosphamide (CTX) and imatinib mesylate (IM). In a companion paper published in this issue of OncoImmunology, we show that the MTD of IL-2 is 6 MIU/day for 5 consecutive days, and that IL-2 increases the impregnation of both IM and of its main metabolite, CGP74588. Among the secondary objectives, we wanted to determine immunological markers that might be associated with progression-free survival (PFS) and/or overall survival (OS). The combination therapy markedly reduced the absolute counts of B, CD4⁺ T and CD8⁺ T cells in a manner that was proportional to IL-2 dose. There was a slight (less than 2-fold) increase in the proportion of regulatory T cells (Tregs) among CD4⁺ T cells in response to IM plus IL-2. The natural killer (NK)-cell compartment was activated, exhibiting a significant upregulation of HLA-DR, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and CD56. The abundance of HLA-DR⁺ NK cells after one course of combination therapy positively correlated with both PFS and OS. The IL-2-induced rise of the CD4⁺:CD8⁺ T-cell ratio calculated after the first cycle of treatment was also positively associated with OS. Overall, the combination of IM and IL-2 promoted the rapid expansion of HLA-DR⁺ NK cells and increased the CD4⁺:CD8⁺ T-cell ratio, both being associated with clinical benefits. This combinatorial regimen warrants further investigation in Phase II clinical trials, possibly in patients affected by gastrointestinal stromal tumors, a setting in which T and NK cells may play an important therapeutic role.

Serum soluble interleukin 2 receptor (sIL-2R) as a marker of acute rejection in renal transplant children

The aim of the study was to evaluate whether or not serum levels of soluble interleukin 2 receptor (sIL-2R) predict acute rejection in pediatric recipients. We studied 51 pediatric renal transplant recipients divided into three groups: Group 1) Biopsy-proven cellular acute rejection (n = 19), Group 2) Graft dysfunction with histological diagnosis other than acute rejection (n = 8) and Group 3) Patients with stable graft function, no biopsy (n = 24). Serum samples for sIL-2R measurement by sandwich ELISA were obtained at the time of renal transplant and at the time of renal biopsy due to graft dysfunction (Groups 1 and 2) or at six months post-transplant in the case of Group 3. The mean ± s.e. serum values of sIL-2R were higher in patients during acute rejection (6539 ± 1802 pg/mL) compared to patients with other causes of graft dysfunction (2217 ± 256 pg/mL) or stable graft function at six months (2183 ± 283 pg/mL) (Kruskal-Wallis p = 0.004). When the sIL2-R levels at the time of transplant were compared to those at the time of biopsy (Groups 1 and 2) or at six months post-transplant in Group 3, there was no significant difference between baseline and biopsy in the acute rejection group (paired t-test = 0.07), whereas there was a significant reduction in Groups 2 and 3.

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.

Changes in thymic function in HIV-positive patients treated with highly active antiretroviral therapy and interleukin-2

Despite its potent antiviral activity, highly active antiretroviral therapy (HAART) only exerts a marginal effect on CD4+ T-cell regeneration in HIV-infected subjects. Combination therapies aimed at boosting T-cell activity and maturation may provide an important contribution to the restoration of immune function. Here, we report the results obtained by a two-year follow-up of a cohort of HIV-infected patients treated with a combination of HAART and interleukin-2 (IL-2). In these patients, in addition to a series of quantitative virological and immunological parameters, we investigated T-cell regeneration by an immunophenotypic assay monitoring CD4+ naïve T cells, and by analysis of thymic function, through the quantification of the excision DNA products of T-cell receptor rearrangement (TRECs) in lymphocytes. Compared with HAART alone, we found that the IL-2 combination therapy was equally effective in reducing the levels of viremia and marginally more effective in decreasing proviral DNA load. Strikingly, the IL-2 combination produced a marked increase in the number of CD4+ T cells bearing a naïve phenotype (CD45RA+, CD62L+), which was apparent for over 96 weeks after therapy. To assess whether these cells were the product of improved T-cell generation, we exploited a competitive quantitative molecular assay to quantify TRECs in peripheral blood lymphocytes. Surprisingly, we found that the levels of these molecules were unchanged in these patients. These findings indicate that improved thymic function does not account for the early rise of CD4 naïve cells in HIV-positive patients treated with IL-2, and suggest that alternative mechanisms of T-cell maturation and differentiation are responsible for this event.

The HIV protease inhibitor Indinavir inhibits cell-cycle progression in vitro in lymphocytes of HIV-infected and uninfected individuals

Indinavir (IDV) is a potent and selective human immunodeficiency virus type 1 (HIV-1) protease inhibitor (PI) widely used in antiretroviral therapy for suppression of HIV, but its effects on the immune system are relatively unknown. Recently, it has been reported that PIs inhibit lymphocyte apoptosis. In the present study we have investigated the effects of ex vivo addition of IDV on lymphocyte activation and apoptosis in cells from HIV-infected children (n = 18) and from healthy uninfected individuals (controls, n = 5) as well as in Jurkat and PM1 T-cell lines. Pretreatment of control peripheral blood mononuclear cell (PBMC) cultures with IDV resulted in a dose-dependent inhibition of lymphoproliferative responses to different activation stimuli. Additionally, this treatment led to cell-cycle arrest in G0/G1 phase in anti-CD3 monoclonal antibody-stimulated PBMC cultures in controls and in 15 of 18 HIV-infected children. Spontaneous- or activation-induced apoptosis of PBMCs from HIV-infected or uninfected individuals or of Fas-induced apoptosis in Jurkat and PM1 T cell lines were not inhibited by IDV. Moreover, IDV did not inhibit activation of caspases-1, -3, -4, -5, -9, and -8 in lysates of Jurkat T cells undergoing Fas-induced apoptosis. The findings indicate that IDV interferes with cell-cycle progression in primary cells but does not directly affect apoptosis. It is concluded that IDV may prolong cell survival indirectly by inhibiting their entry into cell cycle. In individuals on PI therapy, PI-mediated effects could potentially modulate immunologic responses independently of antiviral activity against HIV.

Cytokines and HIV-1: interactions and clinical implications

Cytokines play an important role in controlling the homoeostasis of the immune system. Infection with HIV results in dysregulation of the cytokine profile in vivo and in vitro. During the course of HIV-1 infection secretion of T-helper type 1 (Th1) cytokines, such as interleukin (IL)-2, and antiviral interferon (IFN)-gamma, is generally decreased, whereas production of T helper type 2 (Th2) cytokines, IL-4, IL-10, proinflammatory cytokines (IL-1, IL-6, IL-8) and tumour necrosis factor (TNF)-alpha, is increased. Such abnormal cytokine production contributes to the pathogenesis of the disease by impairing cell-mediated immunity. A number of cytokines have been shown to modulate in vitro HIV-1 infection and replication in both CD4 T lymphocytes and cells of macrophage lineage. HIV-inductive cytokines include: TNF-alpha, TNF-beta, IL-1 and IL-6, which stimulate HIV-1 replication in T cells and monocyte-derived macrophages (MDM), IL-2, IL-7 and IL-15, which upregulate HIV-1 in T cells, and macrophage-colony stimulating factor, which stimulates HIV-1 in MDM. HIV-suppressive cytokines include: IFN-alpha, IFN-beta and IL-16, which inhibit HIV-1 replication in T cells and MDM, and IL-10 and IL-13, which inhibit HIV-1 in MDM. Bifunctional cytokines such as IFN-gamma, IL-4 and granulocyte-macrophage colony-stimulating factor have been shown to have both inhibitory and stimulatory effects on HIV-1. The beta-chemokines, macrophage-inflammatory protein (MIP)-1alpha, MIP-1beta and RANTES are important inhibitors of macrophage-tropic strains of HIV-1, whereas the alpha-chemokine stromal-derived factor-1 suppresses infection of T-tropic strains of HIV-1. This review outlines the interactions between cytokines and HIV-1, and presents clinical applications of cytokine therapy combined with highly active antiretroviral therapy or vaccines.

Interleukin 2 leads to dose-dependent expression of the alpha chain of the IL-2 receptor on CD25-negative T lymphocytes in the absence of exogenous antigenic stimulation

Expression of the alpha chain of the interleukin 2 receptor on T lymphocytes is restricted, increasing in the setting of activation, particularly after antigenic stimulation via the TCR. The effects of IL-2 in vitro on the expression of CD25 and proliferation as well as the cytokine induction in CD25-depleted T cells were studied. CD25-depleted and PBMC of healthy donors were cultured for 7 days with 0, 10, or 100 IU/ml of IL-2. Phenotypic analysis and measurement of cytokines in the culture supernatants were performed. IL-2 led to a dose-dependent induction of the IL-2R alpha chain on both CD4 and CD8 T lymphocytes. In the CD25-depleted cultures, IL-2 treatment (100 IU/ml) increased the percentage of CD4 T cells expressing CD25 by 30.6% (P = 0.05) and of CD8 T cells by 48.2% (P = 0.01) on day 7 compared to no treatment. In the PBMC cultures the increase on day 7 was 36.4% for CD4 (P = 0.01) and 50.8% (P = 0.025) for CD8 T lymphocytes. The patterns of cytokine induction in the CD25-depleted and control cultures were similar with increases of IFN-gamma, GM-CSF, IL-16, TNF alpha, and soluble IL-2 receptor in the IL-2-containing cultures. CFSE experiments demonstrated the proliferative capacity of both CD25-positive and -negative T cells. Interleukin 2 alone can lead to a dose-dependent induction of the alpha chain of its receptor on resting CD4 and CD8 T lymphocytes. IL-2 as a sole stimulant is also associated with generation of a cytokine milieu that includes IFN-gamma, GM-CSF, IL-16, and TNF alpha.

Therapeutic targeting of human immunodeficiency virus type-1 latency: current clinical realities and future scientific possibilities

Factors affecting HIV-1 latency present formidable obstacles for therapeutic intervention. As these obstacles have become a clinical reality, even with the use of potent anti-retroviral regimens, the need for novel therapeutic strategies specifically targeting HIV-1 latency is evident. However, therapeutic targeting of HIV-1 latency requires an understanding of the mechanisms regulating viral quiescence and activation. These mechanisms have been partially delineated using chronically infected cell models and, clearly, HIV-1 activation from latency involves several key viral and cellular components. Among these distinctive therapeutic targets, cellular factors involved in HIV-1 transcription especially warrant further consideration for rational drug design. Exploring the scientific possibilities of new therapies targeting HIV-1 latency may hold new promise of eventual HIV-1 eradication.