Inhibition of the IL-15 pathway in anti-CD25 mAb treated renal allograft recipients

Pediatric Cardiac Intensive Care Society 2014 Consensus Statement: Pharmacotherapies in Cardiac Critical Care Immune Therapy

OBJECTIVE

In this Consensus Statement, we review the etiology and pathophysiology of inflammatory processes seen in critically ill children with cardiac disease. Immunomodulatory therapies aimed at improving outcomes in patients with myocarditis, heart failure, and transplantation are extensively reviewed.

DATA SOURCES

The author team experience and along with an extensive review of the medical literature were used as data sources.

DATA SYNTHESIS

The authors synthesized the data in the literature to present current immumodulatory therapies. For each drug, the physiologic rationale, mechanism of action, and pharmacokinetics are synthesized, and the evidence in the literature to support the therapy is discussed.

CONCLUSIONS

Immunomodulation has a crucial role in the treatment of certain pediatric cardiac diseases. Immunomodulatory treatments that have been used to treat myocarditis include corticosteroids, IV immunoglobulin, cyclosporine, and azathioprine. Contemporary outcomes of pediatric transplant recipients have improved over the past few decades, partly related to improvements in immunomodulatory therapy to prevent rejection of the donor heart. Immunosuppression therapy is commonly divided into induction, maintenance, and acute rejection therapy. Common induction medications include antithymocyte globulin, muromonab-CD3, and basiliximab. Maintenance therapy includes chronic medications that are used daily to prevent rejection episodes. Examples of maintenance medications are corticosteroids, cyclosporine, tacrolimus, sirolimus, everolimus, azathioprine, and mycophenolate mofetil. Rejection of the donor heart is diagnosed either by clinically or by biopsy and is treated with intensification of immunosuppression.

IL-15 is decreased upon CsA and FK506 treatment of acute rejection following heart transplantation in mice

The aim of this study was to investigate the effect of cyclosporine A (CsA) and tacrolimus (FK506) on interleukin-15 (IL-15) production during acute rejection following heart transplantation in mice. Inbred male Balb/c (H‑2d) and C57BL/6 (H-2b) mice were used to establish a heterotopic intra-abdominal cardiac transplantation model. The mice were divided in four groups: syngeneic control, allogeneic acute rejection, allogeneic rejection treated with CsA, and allogeneic rejection treated with FK506. The expression of IL-15, IL-2, and tumor necrosis factor-α (TNF-α) was measured using reverse transcription-polymerase chain reaction (RT-PCR) and western blotting. A low level of IL-15 was detected in transplanted hearts of the control group, with a significant increase observed in the allogeneic acute rejection group. Compared to the allogeneic acute rejection group, IL-15 expression was significantly decreased in the CsA- and FK506-treated allogeneic rejection groups. The TNF-α expression pattern was similar to that of IL-15 in all groups. IL-2 expression was increased in the allogeneic acute rejection group and was inhibited in mice treated with CsA and FK506. In conclusion, increased IL-15 expression in rejected murine heart grafts may be reduced by CsA and FK506 in vivo.

Basiliximab: efficacy and safety evaluation in kidney transplantation

INTRODUCTION

Basiliximab is a chimeric monoclonal antibody directed against the alpha chain of interleukin-2 receptor (IL-2R). When administered intravenously at a dosage of 20 mg at the time of transplantation and 4 days later, basiliximab saturates the alpha chain of IL-2R for 4 weeks.

AREAS COVERED

This review evaluates the efficacy and safety of basiliximab in kidney transplantation. Randomized controlled trials showed that basiliximab can significantly reduce the incidence of acute rejection without increasing the risk of adverse events. When compared with other antibodies used for induction, basiliximab showed efficacy and safety profiles similar to daclizumab, another monoclonal antibody directed against the alpha chain of IL-2R. In comparison with rabbit anti-thymocyte globulins (rATG), basiliximab showed a similar efficacy. However, in patients at higher risk of rejection, rATG proved to be more effective. No serious safety problems related to basiliximab have been reported.

EXPERT OPINION

There is a solid evidence that basiliximab can significantly decrease the risk of acute rejection in kidney transplant recipients without increasing adverse events. This can allow decreased dosage or avoidance of glucocorticoids and reduced dosage of calcineurin inhibitors. On the basis of efficacy, tolerability, ease of administration, and cost effectiveness, basiliximab may be considered the drug of choice for the prophylaxis of acute rejection in standard renal transplant recipients.

Immune reactivity of renal transplant recipients receiving interleukin-2 receptor antagonists during the early posttransplant period

PURPOSE

There is a need for methods that would enable monitoring of the effects of immunosuppression on the recipient's immune system to avoid rejection, immunodeficiency-related complications and non-immune toxicities of the drugs used in therapy.

METHODS

This prospective trial included thirty patients who underwent renal transplantation in our center. All patients received an interleukin-2 receptor (IL-2R) antagonist in combination with mycophenolate, corticosteroid and calcineurin inhibitor. During the first 6 weeks after transplantation, the anti-CD3-stimulated proliferative response of peripheral blood T lymphocytes (PBTL) was studied by cell cycle analysis. The proportion of PBTL in different phases of the cell cycle and expression of IL-2R were determined by flow cytometry.

RESULTS

As an effect of quadruple immunosuppressive therapy including IL-2R antagonists, cell cycle analysis showed an incremental decrease in the proliferative response of PBTL during the first 6 weeks after renal transplantation. A sudden drop in the proportion of IL-2R-positive cells was observed immediately after the first dose of the IL-2R antagonist and a significant antiproliferative effect on PBTL after the second dose. In vitro, IL-2R antagonists showed a dose-dependent inhibition of the anti-CD3-stimulated proliferation of PBTL of healthy blood donors.

CONCLUSIONS

Cell cycle analysis of the immune reactivity of renal allograft recipients may represent a valuable tool for the immunological posttransplant follow-up and optimization of the immunosuppressive therapy.

Induction therapy: why, when, and which agent?

The long-term outcome of paediatric transplantation has improved over the last decade with an increase in the armamentarium of immunosuppressive agents. However, the battle against the hostile immune response at the time of and after transplantation continues. Induction therapy can reduce early injury, to optimize the long-term allograft survival. The goal of induction immunosuppression in paediatric transplantation is to permit the use of lower doses of maintenance immunosuppressive agents without increased rates of acute allograft rejection and chronic allograft damage. The aim of this review is to summarize the current literature relating to the use of antibody agents for induction in paediatric solid organ transplantation.

Long-term results (10 years) of a prospective trial comparing Lo-tact-1 monoclonal antibody and anti-thymocyte globulin induction therapy in kidney transplantation

To evaluate long-term patient and graft survival, and the incidence of acute and chronic rejection, infectious diseases and malignancies following induction therapy with a rat monoclonal interleukin 2 receptor antibody, Lo-Tact-1, or anti-thymocyte globulin (ATG). Forty first-time kidney transplant patients were prospectively randomized to two groups between May 1990 and June 1991. Twenty recipients were treated with Lo-Tact-1 (group 1) and the other 20, with ATG (group 2) during the first 14 days of the transplantation protocol. All patients were treated with azathioprine, steroids and cyclosporin A. Data were collected over 10 years. Median age was 42.1 years in group 1 and 39.3 years in group 2. Six recipients died during the 10 years of follow-up. All had functioning grafts. Death-censored graft survival was 35% in group 1 and 45% in group 2 after 10 years (P = NS). The number of acute rejection was similar in the two groups. Chronic allograft rejection was significantly more frequent in group 2 (n = 9) than in group 1 (n = 3), P < 0.05. Viral and bacterial infections were more frequent in group 2 than in group 1 (respectively 8 vs. 2 and 16 vs. 10, P < 0.05). Three patients had cancer. Although both Lo-tact-1 and ATG effectively prevented acute renal rejection, fewer bacterial and viral infections and cases of chronic allograft rejection were observed in Lo-tact-1-treated patients after 10 years of follow-up, demonstrating the potential value of this treatment for kidney transplantation.

Anti-CD25 antibody treatment of mice vaccinated and challenged with Borrelia spp. does not exacerbate arthritis but inhibits borreliacidal antibody production

CD4(+) CD25(+) T cells are a population of regulatory T cells responsible for the modulation of the immune response in several autoimmune and infectious disease models. We previously showed that adoptive transfer of enriched CD4(+) CD25(+) T cells also plays a major role in the prevention of arthritis in Borrelia-vaccinated (Borrelia burgdorferi isolate 297) and -challenged (B. bissettii) mice. Here, we present evidence that administration of anti-CD25 antibody at the time of challenge or at later intervals fails to enhance the development of severe destructive osteoarthropathy in Borrelia-vaccinated C57BL mice. However, Borrelia-vaccinated and -challenged mice receiving anti-CD25 antibody developed decreased borreliacidal antibody titers compared to vaccinated and challenged controls. These findings suggest that additional mechanisms besides CD4(+) CD25(+) T cells are involved in the regulation of the immune response to Borrelia infection following vaccination.

Disassociation between risk of graft loss and risk of non-Hodgkin lymphoma with induction agents in renal transplant recipients

BACKGROUND

It is widely assumed that the graft-enhancing properties of antilymphocyte induction agents and their lymphoma-inducing potential are intimately related.

METHODS

The Collaborative Transplant Study (CTS) database was used to evaluate graft survival and non-Hodgkin lymphoma at 3 years according to type of induction in 112,122 patients receiving a deceased-donor renal transplant during 1985 to 2004.

RESULTS

The relative risk of 3-year graft loss versus no induction was 1.07 (95% confidence interval [CI], 1.01-1.13; P=0.016) with murine anti-CD3 monoclonal antibody (OKT3), 1.03 (95% CI, 0.95-1.11; NS) with antithymocyte globulin (ATG)-Fresenius, 1.18 (95% CI, 1.02-1.35; P=0.021) with ATGAM, 0.74 (95% CI, 0.68-0.81; P<0.001) with Thymoglobulin, and 0.78 (95% CI, 0.72-0.84; P<0.001) with interleukin (IL)-2RA induction. The standardized incidence ratio of lymphoma compared with a similar nontransplant population was 21.5 (95% CI, 15.7-28.8; P<0.001) with OKT3, 4.9 (95% CI, 1.6-11.5; P=0.008) with ATG-Fresenius, 29.0 (95% CI, 12.5-57.1; P<0.001) with ATGAM, 21.6 (95% CI, 14.3-31.2; P<0.001) with Thymoglobulin, 7.8 (95% CI, 4.4-12.9; P<0.001) with IL-2RAs, and 9.4 (95% CI, 8.3-10.6 P<0.001) with no induction.

CONCLUSIONS

Those agents that offered the highest rates of graft survival were not necessarily associated with the highest risk of lymphoma. Graft survival was significantly improved with Thymoglobulin and IL-2RA induction, whereas lymphoma rates were highest with ATGAM, OKT3, and Thymoglobulin. IL-2RA agents seem to offer the best risk-to-benefit ratio for this patient population overall in terms of graft survival and lymphoma.

Interleukin-2 receptor antagonist induction in modern immunosuppression regimens for renal transplant recipients

Addition of interleukin-2 receptor antagonist (IL-2RA) induction to calcineurin inhibitor (CNI)-based regimens reduces biopsy-proven acute rejection by 30-40%. IL-2RA induction facilitates early withdrawal of steroids, and supports the safe use of reduced-exposure CNI or delayed CNI introduction. IL-2RAs and rabbit antithymocyte globulin (Thymoglobulin) show comparable efficacy in patients at standard or low immunologic risk, but the adverse event profiles of lymphocyte-depleting agents are less favorable. IL-2RAs, uniquely, provide effective immunosuppression with similar tolerability to placebo.

Initial data on basiliximab in critically ill children undergoing heart transplantation

BACKGROUND

More children are coming to heart transplantation on extracorporeal membrane oxygenation (ECMO), or inotropic support and/or with renal impairment. The use of basiliximab, a chimeric monoclonal antibody against CD25 (interleukin 2 receptor alfa) has not been previously reported in critically ill pediatric heart transplant recipients. Basiliximab has potential advantages in the treatment of patients with renal impairment.

METHODS

Basiliximab was provided to 29 patients (median age 7.8 years; range 0.4-16 years) on ECMO, with renal impairment or receiving intravenous inotropes at transplantation. Children normally received 2 doses on Day 0 and Day 4 after transplantation. Calcineurin inhibitor was provided in low dose or withheld altogether in patients with renal impairment. Flow cytometry was used to monitor CD25.

RESULTS

At transplantation, 11 patients were prescribed cyclosporine; the remaining 18 received tacrolimus. All but 4 patients had subtherapeutic levels of calcineurin inhibitor in the first postoperative week. Excluding these 4, there were 19 patients who had more than 4 consecutive doses of calcineurin inhibitor canceled in the first week (median 8 doses; range 3-40 doses). A total of 71 surveillance biopsies were performed, and 4 episodes of severe acute rejection occurred in the first 6 months. In all but one child, the glomerular filtration rate had returned to, or improved on baseline measurement by 1 month after transplantation. Infections rates were low and acceptable. CD25 was undetectable at first assessment, and in all but 1 patient (on ECMO) for at least 2 to 3 weeks thereafter. There were no adverse effects.

CONCLUSIONS

Basiliximab was well tolerated in this group of very ill children. In children with pre- or postoperative renal dysfunction, where doses of calcineurin inhibitor were low or canceled, basiliximab was associated with a low incidence of rejection. Posttransplant ECMO may reduce the efficacy of basiliximab. These preliminary results are encouraging and now need confirmation in a large, randomized trial.

Efficacy and safety of basiliximab in kidney transplantation

The efficacy and safety of basiliximab, in combination with different maintenance regimens, are extensively addressed in the available literature. Basiliximab reduces the incidence of acute rejection, allows a safe reduction of steroid dosage, and is associated with economic savings, although there is substantially no proof that basiliximab prolongs either patient or graft survival. Initial basiliximab administration entails a low-risk and is associated with fewer adverse events than T cell depleting agents. However, life-threatening reactions were reported following re-exposure to basiliximab in recipients who lost graft function early after transplantation and, therefore, discontinued all immunosuppressive agents.

Daclizumab therapy in kidney transplantation—different mechanisms of action in- versus ex-vivo?

Stimulated human T cells from healthy volunteers demonstrate attenuated early interleukin (IL)-2 receptor (R) signaling in the presence of daclizumab (Dac). Aiming to confirm that this ex-vivo effect of Dac is also observed in-vivo, we studied T cells from 3 kidney transplant recipients before and 2-3 weeks and 4-6 months after transplantation. We found by flow cytometry that T cells obtained pre-transplant and stimulated ex-vivo with phytohemeagglutinine upregulated the IL-2R alpha-(CD25) and beta-(CD122) chains as expected. Moreover, exogenous IL-2 induced characteristic tyrosine phosphorylation events detectable by immunoblotting in these cells. However, T cells studied post-transplant neither exhibited CD25 or -122 upregulation nor IL-2-induced tyrosine phosphorylation events, indicating broad, persistent suppression of the IL-2R signaling machinery which thus appears largely inaccessible for Dac in actual transplant recipients. We therefore conclude that the clinical efficacy of this agent may depend on additional mechanisms in-vivo other than those identified ex-vivo.

Biological effects of induction immunosuppression

The concept of induction immunosuppression is evolving. Once used to buttress the inadequacies of past maintenance immunosuppressive regimens, it is now being used to permit effective maintenance immunosuppression using ever decreasing amounts of modern agents. In addition to lymphocyte depletion, with which it was once synonymous, it is now recognized that induction immunosuppression is associated with a host of non-depletional effects such as receptor modulation and blockade, which profoundly alter the lymphocyte's capacity to mount an effective response. Additionally, the recent focus on the effect of induction agents on antigen presenting cells and on regulatory factors controlling homeostatic repopulation may ultimately permit a safer, more refined and more effective approach to induction immunosuppression.

Effects of CD25 monoclonal antibody on proliferative and effector functions of alloactivated human T cellsin vitro

Prophylactic treatment with CD25 mAb has led to a significant decrease of acute rejection rates after renal transplantation. However, despite its inhibitory effect on T cell proliferation and effector functions, rejections still occur. To obtain more insight in persistent alloreactivity, we evaluated the effects of the chimeric IgG1kappa CD25 mAb Basiliximab on proliferation and differentiation of alloactivated T cells from healthy individuals in vitro. Moreover, the capacity of other members of the common cytokine-receptor gamma-chain family to overcome the inhibitory effects of CD25 mAb was studied. The CD25 mAb appeared to limit expansion of alloreactive lymphocytes rather than blocking entry into cell cycle, and it did so irrespective of the previous antigen experience of the cells. Both CD4+ and CD8+ alloresponsive lymphocytes showed diminished intracellular expression of IFN-gamma, TNF-alpha, perforin and granzyme B. Remarkably, cytotoxicity was completely abolished. IL-7, IL-15 and IL-21 could bypass the inhibitory effects of the CD25 mAb on both proliferation and cytotoxicity. In conclusion, persistent alloreactivity in the presence of therapeutic concentrations of CD25 mAb may be caused by alloreactive T cells that still produce cytokines that can damage the allograft. In addition, other members of the common cytokine-receptor gamma-chain family can rescue the proliferative and cytotoxic activity of these alloreactive T cells.