OKT3 prophylaxis in renal grafts with prolonged cold ischemia times: association with improvement in long-term survival

Polyclonal and monoclonal antibodies for induction therapy in kidney transplant recipients

BACKGROUND

Prolonging kidney transplant survival is an important clinical priority. Induction immunosuppression with antibody therapy is recommended at transplantation and non-depleting interleukin-2 receptor monoclonal antibodies (IL2Ra) are considered first line. It is suggested that recipients at high risk of rejection should receive lymphocyte-depleting antibodies but the relative benefits and harms of the available agents are uncertain.

OBJECTIVES

We aimed to: evaluate the relative and absolute effects of different antibody preparations (except IL2Ra) when used as induction therapy in kidney transplant recipients; determine how the benefits and adverse events vary for each antibody preparation; determine how the benefits and harms vary for different formulations of antibody preparation; and determine whether the benefits and harms vary in specific subgroups of recipients (e.g. children and sensitised recipients).

SEARCH METHODS

Randomised controlled trials (RCTs) comparing monoclonal or polyclonal antibodies with placebo, no treatment, or other antibody therapy in adults and children who had received a kidney transplant.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing monoclonal or polyclonal antibodies with placebo, no treatment, or other antibody therapy in adults and children who had received a kidney transplant.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data and assessed risk of bias. Dichotomous outcomes are reported as relative risk (RR) and continuous outcomes as mean difference (MD) together with their 95% confidence intervals (CI).

MAIN RESULTS

We included 99 studies (269 records; 8956 participants; 33 with contemporary agents). Methodology was incompletely reported in most studies leading to lower confidence in the treatment estimates.Antithymocyte globulin (ATG) prevented acute graft rejection (17 studies: RR 0.63, 95% CI 0.51 to 0.78). The benefits of ATG on graft rejection were similar when used with (12 studies: RR 0.61, 0.49 to 0.76) or without (5 studies: RR 0.65, 0.43 to 0.98) calcineurin inhibitor (CNI) treatment. ATG (with CNI therapy) had uncertain effects on death (3 to 6 months, 3 studies: RR 0.41, 0.13 to 1.22; 1 to 2 years, 5 studies: RR 0.75, 0.27 to 2.06; 5 years, 2 studies: RR 0.94, 0.11 to 7.81) and graft loss (3 to 6 months, 4 studies: RR 0.60, 0.34 to 1.05; 1 to 2 years, 3 studies: RR 0.65, 0.36 to 1.19). The effect of ATG on death-censored graft loss was uncertain at 1 to 2 years and 5 years. In non-CNI studies, ATG had uncertain effects on death but reduced death-censored graft loss (6 studies: RR 0.55, 0.38 to 0.78). When CNI and older non-CNI studies were combined, a benefit was seen with ATG at 1 to 2 years for both all-cause graft loss (7 studies: RR 0.71, 0.53 to 0.95) and death-censored graft loss (8 studies: RR 0.55, 0.39 to 0.77) but not sustained longer term. ATG increased cytomegalovirus (CMV) infection (6 studies: RR 1.55, 1.24 to 1.95), leucopenia (4 studies: RR 3.86, 2.79 to 5.34) and thrombocytopenia (4 studies: RR 2.41, 1.61 to 3.61) but had uncertain effects on delayed graft function, malignancy, post-transplant lymphoproliferative disorder (PTLD), and new onset diabetes after transplantation (NODAT).Alemtuzumab was compared to ATG in six studies (446 patients) with early steroid withdrawal (ESW) or steroid minimisation. Alemtuzumab plus steroid minimisation reduced acute rejection compared to ATG at one year (4 studies: RR 0.57, 0.35 to 0.93). In the two studies with ESW only in the alemtuzumab arm, the effect of alemtuzumab on acute rejection at 1 year was uncertain compared to ATG (RR 1.27, 0.50 to 3.19). Alemtuzumab had uncertain effects on death (1 year, 2 studies: RR 0.39, 0.06 to 2.42; 2 to 3 years, 3 studies: RR 0.67, 95% CI 0.15 to 2.95), graft loss (1 year, 2 studies: RR 0.39, 0.13 to 1.30; 2 to 3 years, 3 studies: RR 0.98, 95% CI 0.47 to 2.06), and death-censored graft loss (1 year, 2 studies: RR 0.38, 0.08 to 1.81; 2 to 3 years, 3 studies: RR 2.45, 95% CI 0.67 to 8.97) compared to ATG. Creatinine clearance was lower with alemtuzumab plus ESW at 6 months (2 studies: MD -13.35 mL/min, -23.91 to -2.80) and 2 years (2 studies: MD -12.86 mL/min, -23.73 to -2.00) compared to ATG plus triple maintenance. Across all 6 studies, the effect of alemtuzumab versus ATG was uncertain on all-cause infection, CMV infection, BK virus infection, malignancy, and PTLD. The effect of alemtuzumab with steroid minimisation on NODAT was uncertain, compared to ATG with steroid maintenance.Alemtuzumab plus ESW compared with triple maintenance without induction therapy had uncertain effects on death and all-cause graft loss at 1 year, acute rejection at 6 months and 1 year. CMV infection was increased (2 studies: RR 2.28, 1.18 to 4.40). Treatment effects were uncertain for NODAT, thrombocytopenia, and malignancy or PTLD.Rituximab had uncertain effects on death, graft loss, acute rejection and all other adverse outcomes compared to placebo.

AUTHORS' CONCLUSIONS

ATG reduces acute rejection but has uncertain effects on death, graft survival, malignancy and NODAT, and increases CMV infection, thrombocytopenia and leucopenia. Given a 45% acute rejection risk without ATG induction, seven patients would need treatment to prevent one having rejection, while incurring an additional patient experiencing CMV disease for every 12 treated. Excluding non-CNI studies, the risk of rejection was 37% without induction with six patients needing treatment to prevent one having rejection.In the context of steroid minimisation, alemtuzumab prevents acute rejection at 1 year compared to ATG. Eleven patients would require treatment with alemtuzumab to prevent 1 having rejection, assuming a 21% rejection risk with ATG.Triple maintenance without induction therapy compared to alemtuzumab combined with ESW had similar rates of acute rejection but adverse effects including NODAT were poorly documented. Alemtuzumab plus steroid withdrawal would cause one additional patient experiencing CMV disease for every six patients treated compared to no induction and triple maintenance, in the absence of any clinical benefit. Overall, ATG and alemtuzumab decrease acute rejection at a cost of increased CMV disease while patient-centred outcomes (reduced death or lower toxicity) do not appear to be improved.

Anti-CD3 mAbs for treatment of type 1 diabetes

The use of anti-CD3 monoclonal antibodies (mAbs) has moved from the bench to the bedside. The experience with the anti-human CD3 mAb OKT3 for treatment of transplant rejection identified limitations that were largely overcome with the creation of humanized non-FcR binding antibodies: Teplizumab, Otelixizumab and Visilizumab. Preclinical studies showed the ability of the drugs to reverse hyperglycaemia in diabetic non-obese diabetic (NOD) mice providing rationale for clinical trials with the agents. The former two drugs have been tested in subjects with new onset type 1 diabetes. They have both shown, in randomized clinical trials, an ability to reduce the loss of insulin production over the first 2 years of the disease. In addition, the need for exogenous insulin to maintain glucose control has been reduced. However, these agents alone do not restore normal glucose control, and future approaches will likely require combinations of agents with complementary immune or metabolic activity.

Cold ischemia is a major determinant of acute rejection and renal graft survival in the modern era of immunosuppression

BACKGROUND

The aim of our study was to examine, in a recent cohort of kidney transplant recipients who have received modern immunosuppressive therapy, the respective role of cold ischemia time (CIT) and delayed graft function (DGF) on acute rejection (AR) rates and long-term graft survival.

METHODS

We retrospectively reviewed the charts of 611 renal transplantations between 1996 and 2005. Most patients received a calcineurin inhibitor as maintenance therapy, either cyclosporine (43%) or tacrolimus (52%) and 76% of the patients received an antilymphocyte induction therapy. Study endpoints were DGF, first-year AR, and long-term graft survival. Uni- and multivariate analyses were performed to determine factors that may have influenced the study outcomes.

RESULTS

DGF was observed in 16.2% of patients. Both older donor age and longer CIT were significant risk factors for DGF. DGF rates were similar whether patients received a calcineurin inhibitor before transplantation or not. AR occurred in 16.5% of grafts during the first year. Independent predictors of AR by multivariate analysis were duration of dialysis, CIT, current panel-reactive lymphocytotoxic antibody more than 5%, and the number of human leukocyte antigen-A, B, and DR mismatches. Each hour of cold ischemia increases the risk of rejection by 4%. With respect to death-censored graft survival, three pretransplant parameters emerged as independent predictors of graft loss: younger recipient age, peak panel-reactive lymphocytotoxic antibody more than 5% and longer CIT. The detrimental effect of CIT on graft survival was entirely because of its propensity to trigger AR. When AR was added to the multivariate Cox model, CIT was no longer significant whereas first-year AR became the most important predictor of graft loss (Hazards ratio, 4.6).

CONCLUSION

Shortening CIT will help to decrease not only DGF rates but also AR incidence and hence graft loss. Patients with prolonged CIT should receive adequate immunosuppression, possibly with antilymphocyte preparations, to prevent AR occurrence.

Heme oxygenase 1 and renal ischemia and reperfusion injury: The impact of immunosuppressive drug

This study was undertaken to investigate the involvement of cyclooxygenase-2 (COX-2) in allergic nasal inflammation in actively sensitized rats. An allergic rhinitis model was developed by the repeated topical application of antigen into the nasal cavities in the sensitized rats. The severity of allergic rhinitis was studied by measuring the nasal behavior, as well as electroencephalogram (EEG) activity by antigen challenge. The electrodes were implanted chronically into the bilateral olfactory bulb of the rats and the EEG was measured monopolarly with an electroencephalograph (EEG, Nohon Kohden, Japan). The intranasal application of antigen caused the increase of nasal allergic signs as well as an EEG spike in a dose-dependent fashion, and at a dose of 50 microg/site, it showed a significant effect. The responses induced by the antigen were evaluated with certain drugs, etodolac (a selective COX-2 inhibitor), indomethacin (a non-selective COX inhibitor), ramatroban (a thromboxane A2 receptor antagonist) and zafirlukast (a cys-leukotriene receptor antagonist). Etodolac showed the inhibition of nasal behavior and EEG spike in a dose-related fashion, and at doses of 3 and 10 mg/kg, it showed a significant effect. Moreover, ramatroban also caused the dose-related inhibition of nasal behavior and EEG spike induced by antigen. On the other hand, both indomethacin and zafirlukast had no effects on the responses induced by antigen, even at a higher dose. Therefore, it can be concluded that cyclooxygenase-2 actively participates in the allergic nasal inflammation in actively sensitized rats.

FTY720-induced lymphocyte homing modulates post-transplant preservation/reperfusion injury

BACKGROUND

A novel immunomodulator, FTY720, modulates lymphocyte migration to injured tissues via enhanced lymphocyte sequestration to secondary lymphoid organs. We tested whether or not single-dose FTY720 (0.5 mg/kg) pretreatment rescues renal grafts from post-transplant preservation/reperfusion injury.

METHODS

Rat renal grafts were cold-preserved in University of Wisconsin (UW) solution for 4 hours and then transplanted into syngeneic or allogeneic recipients that received a single dose of FTY720 24 hours before transplantation. Flow cytometry analysis of peripheral blood and lymph nodes was performed to confirm the biologic effect of FTY720. Grafts were harvested after 24 hours. Renal sections were examined histologically and stained for intracellular adhesion molecule-1 (ICAM-1), vascular cellular adhesion molecule-1 (VCAM-1), platelet endothelial cellular adhesion molecule-1 (PECAM-1), major histocompatibility complex (MHC) class II, and inflammatory cells. Interleukin-1 (IL-1) production was determined in renal protein extracts.

RESULTS

FTY720 pretreatment significantly increased CD3+ T-cell sequestration to lymph nodes in the face of peripheral lymphopenia. Isografts and allografts from the FTY720-treated groups did not develop increased creatinine (0.55 +/- 0.12 in isografts and 0.62 +/- 0.08 mg/dL in allografts), compared with vehicle controls (2.28 +/- 0.20 in isografts and 2.24 +/- 0.18 mg/dL in allografts). Kidneys from FTY720-treated groups also showed lower acute tubular damage scores. Furthermore, FTY720 decreased neutrophil influx, although circulating neutrophils were unchanged. FTY720 also prevented postischemic IL-1 intragraft production not affecting infiltration with recipient ED-1+ macrophages and MHC class II-positive cells. Expression of ICAM-1, VCAM-1, and PECAM did not differ among groups.

CONCLUSION

FTY720 ameliorated morphologic and functional consequences of post-transplant reperfusion injury. Thus, FTY720-induced peripheral T-cell absence may influence intragraft IL-1 production and neutrophil infiltration, despite proadhesive endothelial properties. FTY720 may broaden the utility in renal transplantation as a pretreatment strategy against preservation/reperfusion injury.

Immune Responses in Kidney Preservation and Reperfusion Injury

Organ preservation and reperfusion injury have significant detrimental effects on both short- and long-term organ function. Ischemia reperfusion injury (IRI) underlies organ transplant dysfunction, myocardial infarction, stroke, and shock. Multiple molecular pathways are engaged in reactive oxygen production, apoptosis, signaling, and tissue regeneration. There has been an increased understanding of the important role of immune and inflammatory pathways in IRI, both in humans and in experimental models. Both cellular and soluble components of the immune system are directly activated during IRI, and there is evidence that immune mediators directly contribute to organ dysfunction. Immune activation during IRI likely underlies the enhanced immunogenicity of ischemic organs, with resultant increased rejection and fibrosis. Novel human therapies targeting T and B cells for classic immune diseases can now be considered to prevent and treat IRI. Organ preservation injury and cold ischemia could well have distinct pathophysiology from warm IRI and represent an opportunity to develop improved preservation methods.

Effect of immunosuppression on damage, leukocyte infiltration, and regeneration after severe warm ischemia/reperfusion renal injury

BACKGROUND

Post-ischemia/reperfusion (I/R) damage, accompanied by leukocyte infiltration, is unavoidable in renal transplantation, as is the need for immunosuppressive treatment. Influence of immunosuppressive treatment on post-I/R renal damage, nonalloimmune cellular infiltration, and regeneration is not well studied.

METHODS

Uninephrectomized inbred LEW rats were submitted to warm renal ischemia of 45 minutes/60 minutes, and received different immunosuppressive regimens: cyclosporine (CsA) 10 mg/kg/day subcutaneously in the neck daily, or mycophenolate mofetil (MMF) 20 mg/kg/day by daily oral gavage. Control animals underwent sham operation (unilateral nephrectomy) with immunosuppressive treatment or ischemia with vehicle administration. In addition the effect of MMF/mycophenolic acid (MPA) on renal tubule cell proliferation in culture was studied with bromodeoxyuridine incorporation.

RESULTS

The post-I/R interstitial cellular infiltration/proliferation consisted mainly of mononuclear leukocytes [first monocytes/macrophages (Mo/MPhi) followed by CD4+ cells]. This mononuclear cell infiltration became apparent 24 hours after injury at the time of acute tubular necrosis, and was most prominent during the phase of regeneration. Severe I/R combined with CsA aggravated morphologic damage and dysfunction, without effect on tubular cell proliferation and tubular regeneration. Early leukocyte infiltration was qualitatively and quantitatively comparable to control animals, yet decreased moderately later in time. In contrast, MMF in combination with severe I/R did not influence initial morphologic damage and dysfunction. Although the initial leukocyte infiltration was comparable to control animals, the subsequent mononuclear cell accumulation, especially CD4 T cells decreased dramatically during MMF treatment. This was concomitant with a decrease of tubular cell proliferation and hence tubular regeneration. Increasing MPA concentrations in renal tubular cell culture caused a significant decrease in total cell number, and an almost arrest of bromodeoxyuridine incorporation, as measurement of cell proliferation.

CONCLUSION

Immunosuppressive treatment with CsA or MMF affected significantly and in a different manner post-I/R renal morphologic damage, interstitial leukocyte, accumulation and regeneration.

The use of basiliximab in solid organ transplantation

The risk of acute rejection is at its highest early post-transplant. The use of various antibodies early after transplant achieves potent immunosuppression to prevent acute rejection, allowing the clinician the opportunity to optimise baseline immunosuppressive management and to delay the use of nephrotoxic agents (calcineurin inhibitors), while the graft reaches a baseline function. Basiliximab (Simulect trade mark, Novartis) is a monoclonal antibody that binds specifically to the alpha-subunit of the human high-affinity interleukin-2 receptor (IL-2r) complex, consequently inhibiting interleukin-2 (IL-2) binding. IL-2 receptors are selectively expressed on the surface of the activated lymphocytes. Administration of basiliximab inhibits IL-2 mediated activation of lymphocytes, a critical pathway involved in allograft rejection. Several clinical studies have shown that basiliximab administration as an induction agent significantly reduces the incidence of acute rejection, even in high risk patients. In addition, basiliximab is well-tolerated with minimal side effects.

Immunoprophylaxis with basiliximab compared with antithymocyte globulin in renal transplant patients receiving MMF-containing triple therapy

Acute graft rejection remains a major problem in renal transplant recipients, and there is no consensus on the optimal immunosuppressive strategy. Immunoprophylaxis with Thymoglobulin or basiliximab has significantly reduced the incidence of acute rejection episodes and graft loss following kidney transplantation. This open, randomized, multicenter study investigated the efficacy and tolerability of basiliximab (20mg day 0-day 4) plus early cyclosporine from day 0 (n = 50) compared with Thymoglobulin plus delayed cyclosporine (n = 50) in adult kidney transplant patients. In addition, all patients received steroids and mycophenolate mofetil (MMF) at standard doses from day 0. Patient and graft survival rates at 12 months were 98 and 94% in the basiliximab group, respectively, compared with 100 and 96% in the Thymoglobulin' group. The incidences of biopsy-confirmed acute rejection (8.0% in each group) and treatment failure (14% in the basiliximab group vs. 8% in the Thymoglobulin group) were comparable in the two groups. There was a non-significant tendency to more dialysis (14 vs. 6%), and fewer cytomegalovirus (CMV) infections (p = 0.005) in the basiliximab group, but the percentage of clinical CMV was not different between the two groups (6 vs. 12%). Both strategies give excellent results, despite the differences in patterns, in nonhyperimmunized patients receiving their first cadaveric renal allograft.

A randomized prospective trial of OKT3 induction in the current immunosuppression era

Recent improvements in immunosuppression and subsequent decreases in the incidence of acute rejection have brought into question the benefit of the use peri-transplant antibody therapy (i.e. induction therapy). In the current era of immunosuppression that includes mycophenolate mofetil (MMF) and cyclosporine emulsion (Neoral, Novartis, Basle, Switzerland), we designed and have completed a prospective, randomized trial to address this question. Cadaveric and living donor renal allograft recipients were randomized to receive either OKT3/MMF/delayed Neoral/prednisone or MMF/immediate Neoral/prednisone without OKT3. The incidence of rejection episodes was the primary end point. Patients with delayed graft function were excluded. All rejection episodes were biopsy proven and all patients have been followed for a minimum of 2 yr. Fifty-four patients received OKT3 induction, of which 6 patients suffered a rejection episode (11%), while 13 patients (27%) not receiving OKT3 (p=0.04) had a rejection episode. Four patients in the no OKT3 group suffered multiple rejections, while there were only 2 with more than one episode in the OKT3 group. There was no increased incidence of infectious complications in the group receiving OKT3. Hospital costs tended to be higher in the OKT3-treated group, but were not significantly different. The low incidence of rejection in the OKT3-treated group was intriguing and validates the use of antibody therapy in the early post-operative periods even in the era of improved baseline immunosuppression.

Contemporary immunosuppression in renal transplantation

Over the past 3 decades, renal allograft survival has improved significantly as a result of the development of powerful immunosuppressive agents. Nevertheless, the overall half-life of renal allografts has increased marginally during that time period, owing to drug-related nephrotoxicity and chronic rejection. New immunosuppressive agents are being evaluated because of the need for a reduction in the dose of nephrotoxic calcineurin inhibitors and corticosteroids. Additional agents have demonstrated the ability to retard the onset of chronic rejection in preclinical transplant models. In concert with these efforts, approaches are in development to alleviate the ever increasing shortage of donor organs, including the as yet unrealized goals of successful and practical xenotransplantation and the bioartificial kidney. Further identification and development of novel agents that target the specific components of the allograft response will provide the key to the achievement of donor-specific tolerance, the "Holy Grail" of solid organ transplantation.

A randomized prospective trial of low-dose OKT3 induction therapy to prevent rejection and minimize side effects in recipients of kidney transplants

BACKGROUND

We attempted to minimize the undesired side effects and maximize the benefit of OKT3 induction therapy in renal transplantation.

METHODS

One hundred and one recipients of kidney-only transplants were randomized to three groups. Each received low-dose 2.5-mg OKT3 induction for 7-14 days, but different premedication on days 0, 1, and 2. Group I was given 250 mg i.v. methylprednisolone at 1 and 6 hr, and group II received another 500 mg at 1 hr before initial OKT3. Group III received Atgam 15 mg/kg on day 0 and began OKT3 on day 1. A CD3+ T-cell cut-off of 50/mm3 was used to guide therapy. Maintenance therapy included cyclosporine and steroids for each patient. However, groups I and II were also given mycophenolate mofetil, and group III received azathioprine as a third agent. All rejections were biopsy confirmed and Banff scored.

RESULTS

No differences in demographic or transplant characteristics were noted between groups I, II, and III, and mean follow-up was 25.7 (1-38) months. There was no significant difference in actuarial patient (90%, 91%, 94%) or graft survival (83%, 88%, 84%) at 3 years between the respective groups. Mean creatinine values and infectious complications were similar for each group. No patient experienced acute rejection during induction, and eight patients required dose escalation to sustain suppression of CD3 counts. The incidence of acute rejection at 6 and 12 months was significantly (P=0.004) greater in group III (38.2, 44.1%) than in either group I (15.1, 18.1%) or group II (14.7, 17.6%); relative risk 1.988 (95% CI 1.012-3.906). Formation of anti-OKT3 antibody was significantly (P=0.006) greater in group III (26.5%) than in group I (6%) or group II (2.9%). Group I recipients enjoyed significantly (P=0.001) fewer (2.17) OKT3 side effects on days 0, 1, and 2 than group II (3.03) or group III (2.49), and contained the largest number (61%) of recipients who experienced no side effects. Group I also exhibited the most suppressed profile of OKT3-induced release of tumor necrosis factor-alpha (P=0.006), interferon-gamma (P=NS), and interleukin-6 (P=0.01) on days 0 and 1.

CONCLUSIONS

Low-dose 2.5-mg OKT3 with pretreatment of split-dose steroids on days 0, 1, and 2 provides the most effective method for OKT3 induction, which minimizes side effects for most patients. Subsequent maintenance therapy with cyclosporine, mycophenolate mofetil, and steroids provides effective rejection prophylaxis without increased complications for up to 3 years. Predepletion of T cells before exposure to OKT3 does not prevent cytokine release.

In vitro characterization of five humanized OKT3 effector function variant antibodies

Orthoclone OKT 3 (mOKT3) is a highly effective agent for the reversal of steroid-resistant renal allograft rejection. However, its wider use has been limited by the development of a human anti-mouse antibody response (HAMA) and by the "cytokine release syndrome" (CRS). CRS has been associated with T cell/monocyte activation and, secondarily, with activation of the complement cascade. These processes are mediated through Abs' Fc regions by their abilities to cross-link T cells and mononuclear cells and to activate complements. To alleviate these problems, a group of five huIgG1- and huIgG4-based OKT3 wild-type antibodies and their corresponding Fc mutants with altered residues at amino acids 234, 235, and 318, reported to be required for FcgammaRI and FcgammaRII binding and complement fixation, were constructed. Characterization of these humanized OKT3 Abs, denoted huOKT3gamma1, huOKT3gamma4, huOKT3gamma1(A(234), A(235)), huOKT3gamma4(A(234), A(235)), and huOKT3gamma1(A(318)), has demonstrated that huOKT3gamma1(A(234), A(235)) and huOKT3gamma4(A(234), A(235)), and have at least a 100-fold reduced binding to FcgammaRI and FcgammaRII. As expected, they are much less potent in the induction of T cell activation and cytokine release, yet retain in vitro immunosuppressive effects as potent as those of mOKT3. Unexpectedly, while huOKT3gamma1(A(318)) did not show any reduction in its ability to bind C1q and to fix a complement, huOKT3gamma1(A(234), A(235)) was completely inactive. The in vitro characteristics of huOKT3gamma1(A(234), A(235)) are consistent with recent in vivo studies, in which this Ab showed greatly reduced HAMA and CRS with the retention of its ability to reverse ongoing graft rejection in man.

Immunosuppressant-induced nephropathy: pathophysiology, incidence and management

Immunosuppressant-induced nephrotoxicity, in particular chronic progressive tubulointerstitial fibrosis/arteriopathy induced by the calcineurin inhibitors cyclosporin and tacrolimus, has become the 'Achilles heel' of immunosuppressive agents. The use of calcineurin inhibitors as primary immunosuppressants in hepatic and cardiac transplantation has led to end-stage renal disease and dialysis. Calcineurin inhibitor-induced acute renal failure may occur as early as a few weeks or months after initiation of cyclosporin therapy. The clinical manifestations of acute renal dysfunction are caused by vasoconstriction of renal arterioles, and include reduction in glomerular filtration rate, hypertension, hyperkalaemia, tubular acidosis, increased reabsorption of sodium and oliguria. The acute adverse effects of calcineurin inhibitors on renal haemodynamics are thought to be directly related to the cyclosporin or tacrolimus dosage and blood concentration. However, new clinical data indicate that calcineurin inhibitor-induced chronic nephropathy can occur independently of acute renal dysfunction, cyclosporin dosage or blood concentration. Several strategies have been evaluated to attenuate cyclosporin-induced nephropathy, but their efficacy remains unknown. Cytokine release syndrome associated with the use of muronomab-CD3 (OKT-3) can also contribute to the pathogenesis of transient acute tubular necrosis and renal dysfunction following renal transplantation. Continued research and clinical experience should provide information regarding the aetiology of cyclosporin-induced chronic progressive tubulointerstitial fibrosis/arteriopathy and its potential treatment.

Down-regulation of interleukin-2 and interferon-gamma and maintenance of interleukin-4 and interleukin-10 production after administration of an anti-CD3 monoclonal antibody in mice

BACKGROUND

Activating anti-CD3 monoclonal antibodies (mAbs), such as OKT3, are potent immunosuppressive agents that are widely used in clinical transplantation. We investigated whether the in vivo induction of T cell unresponsiveness contributes to the immunosuppressive properties of the anti-mouse-CD3 mAb 145-2C11.

METHODS

After a single in vivo administration of 145-2C11 residual T cells were restimulated in vivo and in vitro to assess cytokine production. Mice were also transplanted with allogeneic skin 9 days after 145-2C11 administration to investigate whether the immunosuppressive properties of the antibody persist after the reexpression of the T cell receptor.

RESULTS

Pretreatment with anti-CD3 mAbs caused a profound deficit in both interleukin- (IL) 2 and interferon- (IFN) y secretion upon restimulation in vivo, whereas IL-4 was only partially inhibited and IL-10 production was significantly increased. Purified T cells obtained from mice injected with anti-CD3 mAb also displayed deficient IL-2 and IFN-gamma production together with persisting IL-4 and IL-10 secretion. 145-2C11 had immunosuppressive properties that per sisted after the reexpression of the T cell receptor because mice transplanted with allogeneic skin 9 days after a single anti-CD3 mAb injection still had significantly prolonged graft survival (14.1+/-0.6 days vs. 10.7+/-0.4 days in controls, P<0.02). Blocking IL-4 and IL-10 by neutralizing mAbs further prolonged skin graft survival in mice injected with 145-2C11 (18.3+/-0.7 vs. 14.8+/-0.6 days, P<0.02).

CONCLUSION

The in vivo administration of the 145-2C11 anti-CD3 mAb results in the selective inhibition of Thl-type cytokine secretion upon restimulation, which correlates with a state of immunosuppression. The persistent production of Th2-type cytokines does not contribute to the anti-CD3 mAb-mediated prolonged survival of skin allografts in our experimental model.

A randomized multicenter trial of the anti-ICAM-1 monoclonal antibody (enlimomab) for the prevention of acute rejection and delayed onset of graft function in cadaveric renal transplantation: a report of the European Anti-ICAM-1 Renal Transplant Study Group

BACKGROUND

T-cell activation through T-cell receptor engagement requires co-stimulatory molecules and also adhesion molecules such as ICAM-1. Moreover ICAM-1 mediates leukocyte invasion from the blood into tissue during inflammatory processes. In animal studies using mouse monoclonal antibodies against ICAM-1 (enlimomab), renal allograft survival has been improved and reperfusion damage from ischemia reduced. The European Anti-ICAM-1 Renal Transplant Study (EARTS) was a randomized, double-blind, parallel-group, placebo-controlled study lastingl year and performed in 10 transplant centers in Europe.

METHODS

A total of 262 recipients of cadaveric kidneys were given either enlimomab or a placebo for 6 days and were given triple immunosuppressive therapy of cyclosporine, azathioprine, and prednisolone. The primary efficacy endpoint was the incidence of the first acute rejection within 3 months, and each event was assessed by a committee including investigators and independent pathologists.

RESULTS

There was no significant difference in the incidences of first acute rejection at 3 months between the placebo and enlimomab groups (39% vs. 45%), and enlimomab did not reduce the risk of delayed onset of graft function (DGF) (26% vs. 31%). Neither was there a difference in patient survival (95% vs. 91%) or graft survival (89% vs. 84%) at 1 year. Fatal events occurred in 19 (7%) patients (7 placebo, 12 enlimomab). Clinically, the most important non-fatal adverse events were infections; however, there was no statistically significant difference between the incidences in the two groups (70% vs. 79%).

CONCLUSION

Short term enlimomab induction therapy after renal transplantation did not reduce the rate of acute rejection or DGF.

A pilot trial of recombinant human interleukin-10 in kidney transplant recipients receiving OKT3 induction therapy

BACKGROUND

We conducted a randomized, double-blind, placebo-controlled, rising single-dose study to investigate the effects of recombinant human (rh) interleukin (IL) 10 in renal transplant patients who received OKT3 as induction therapy.

METHODS

Patients received 0.1 (n=6), 1 (n=6), or 10 microg/kg (n=3) rhIL-10 or placebo (n=6) intravenously 30 min before the first injection of 5 mg of OKT3. We monitored IL-10 serum levels, the effect of rhIL-10 on OKT3-induced cytokine production, clinical toxicity, and the incidence of immunization against OKT3.

RESULTS

Serum IL-10 levels in the three experimental groups reached 0.8+/-0.2, 7.9+/-1.3, and 118.6+/-7.3 ng/ml (mean+/-SEM), respectively, 30 min after rhIL-10 injection. Peak plasma levels of tumor necrosis factor-alpha (TNF-alpha) were reduced from 2953+/-1599 pg/ml in patients injected with OKT3 and placebo to 447+/-155, 703+/-246, and 459+/-246 pg/ml in patients injected with 0.1, 1, and 10 microg/kg rhIL-10, respectively. Values for 24-hr TNF-alpha area under the curve decreased from 8988+/-3551 pg x hr/ml in control patients to 2284+/-494, 3950+/-955, and 2420+/-931 pg x hr/ml for the 0.1, 1, and 10 microg/kg rhIL-10 dose groups, respectively (P=0.045). There was also a trend toward reduced plasma levels of IL-2, IL-8, and interferon-gamma in rhIL-10-pretreated patients. Although none of the patients who received placebo or 0.1 or 1 microg/kg rhIL-10 developed an IgM antibody response directed against OKT3 during the first 10 days, this occurred in all three patients who received the highest rhIL-10 dose. In two of these patients, neutralization of OKT3 was associated with a reversible acute rejection episode.

CONCLUSIONS

Pretreatment with doses of up to 1 microg/kg rhIL-10 is safe and reduces the release of TNF-alpha induced by OKT3. However, higher doses might promote early sensitization to OKT3.

Muromonab CD3: a reappraisal of its pharmacology and use as prophylaxis of solid organ transplant rejection

The murine monoclonal antibody muromonab CD3 (OKT3) is directed against the CD3 antigen on peripheral human T cells and effectively blocks all T cell function. Prophylaxis with muromonab CD3 (5mg intravenously once daily for 10 to 14 days) as induction therapy together with corticosteroids, azathioprine and delayed cyclosporin (sequential therapy) optimises early graft function by delaying the potentially nephrotoxic and hepatotoxic effects of cyclosporin until graft function is established. Although clinical data are limited (by inconsistencies in trial design and trial size), prophylactic muromonab CD3-based sequential therapy is significantly more effective than standard triple therapy in the prophylaxis of allograft rejection in renal and hepatic, but not cardiac, transplant recipients. Benefits are particularly notable in patients with delayed graft function. No significant between-treatment differences in patient survival have been observed. The overall efficacy of muromonab CD3- and polyclonal-based prophylactic regimens appears to be similar, although results vary between investigators and confirmation is needed. An anti-interleukin-2 monoclonal antibody-based prophylactic regimen improved graft and patient survival compared with muromonab CD3-based prophylaxis in hepatic transplant recipients. Antimuromonab CD3 antibodies may develop; however, muromonab CD3 may be successfully reused in patients with low titres. Preliminary pharmacoeconomic data suggest that mean drug costs are greater with quadruple immunosuppressive regimens containing muromonab CD3, antithymocyte globulin (ATG) or antilymphocyte globulin (ALG) than with triple therapy. Drug costs with prophylactic muromonab CD3-based regimens were similar or greater than those with polyclonal-based protocols. The first doses of muromonab CD3 are associated with the 'cytokine-release syndrome'. More severe first-dose events include aseptic meningitis, intragraft thromboses, seizures and potentially fatal pulmonary oedema. The incidence and/or severity of cytomegalovirus infection with prophylactic muromonab CD3 based immunosuppression is similar to or greater than that with triple therapy and ATG- or ALG-based regimens. However, the risk of infection and also the observed increase in lymphoproliferative disorders appears to be related to the degree of immunosuppression rather than to the drug itself Thus, sequential muromonab CD3-based therapy is more effective than standard triple therapy (in renal and hepatic transplant recipients) and appears to be similar to that of polyclonal-based regimens in the prophylaxis of transplant rejection. Although the routine use of prophylactic muromonab CD3 in low-risk patients with primary graft function does not appear to be justified, prophylactic muromonab CD3-based therapy has a role in patients at high risk of rejection.