Georges Karam

Frequency and Clinical Implications of Development of Donor-Specific and Non–Donor-Specific HLA Antibodies after Kidney Transplantation

The involvement of immunologic and nonimmunologic events in long-term kidney allograft failure is difficult to assess. The development of HLA antibodies after transplantation is the witness of ongoing reactivity against the transplant, and several studies have suggested that the presence of HLA antibodies correlates with poor graft survival. However, they have not discriminated between donor-specific (DS) and non-specific (NDS) antibodies. A total of 1229 recipients of a kidney graft, transplanted between 1972 and 2002, who had over a 5-yr period a prospective annual screening for HLA antibodies with a combination of ELISA, complement-dependent cytotoxicity, and flow cytometry tests were investigated; in 543 of them, the screening was complete from transplantation to the fifth year postgrafting. Correlations were established between the presence and the specificity of the antibodies and clinical parameters. A total of 5.5% of the patients had DS, 11.3% had NDS, and 83% had no HLA antibodies after transplantation. NDS antibodies appeared earlier (1 to 5 yr posttransplantation) than DS antibodies (5 to 10 yr). In multivariate analysis, HLA-DR matching, pretransplantation immunization, and acute rejection were significantly associated with the development of both DS and NDS antibodies and also of DS versus NDS antibodies. The presence of either DS or NDS antibodies significantly correlated with lower graft survival, poor transplant function, and proteinuria. Screening of HLA antibodies posttransplantation could be a good tool for the follow-up of patients who receive a kidney transplant and allow immunosuppression to be tailored.

Inducing CTLA-4–Dependent Immune Regulation by Selective CD28 Blockade Promotes Regulatory T Cells in Organ Transplantation

An improved method of immunosuppression allows better immune function and prolongs the survival of transplanted organs in nonhuman primates. Increasing Tolerance with Less Toxicity According to Chinese legend, 2500 years ago the physician Pien Ch’iao exchanged the hearts of two warriors, one of strong spirit and weak will and the other of weak spirit and strong will, with the aim of achieving balance in their characters. Of course, without modern surgical techniques and the ability to suppress organ rejection by the recipient’s immune system, such transplants would have been impossible. It was not until the discovery of the powerful immunosuppressant drug cyclosporin that organ transplants between unrelated individuals became routinely successful, beginning in the 1980s. Cyclosporin and some newer similar drugs, however, have toxic side effects, and none of them can stop eventual rejection of the organ, so researchers are seeking other options. Now, Vanhove and colleagues test an alternative immunosuppressive strategy. T cells are a major culprit in the immune response directed against transplanted organs, and therefore a number of immunosuppressive drugs target T cells. Cyclosporin, for example, inhibits calcineurin, a protein phosphatase that under normal conditions increases the expression of interleukin 2, which—among other functions—promotes the proliferation of activated T cells. Certain newer approaches to immunosuppression target the process by which T cells become activated. In general, this process is induced by antigen binding to the T cell receptor and reinforced by costimulatory molecules—CD80 and CD86—binding to the T cell CD28 receptor. Additionally, CD80/86 can bind to the CTLA-4 receptor, resulting in T cell inhibition. CTLA-4 is also required for the function of regulatory T cells (Tregs), which suppress aberrant immune responses and are important for inducing tolerance toward transplanted tissue. Several drugs that block CD80/86 have been developed as a nontoxic alternative to calcineurin inhibitors, but in addition to affecting the CD28-mediated pathway of T cell stimulation, these reagents also inhibit the CTLA-4 signals required for Treg function. To avoid inhibiting CTLA-4–dependent regulation of the immune system while suppressing T cell activation, the Vanhove, Blancho, and Pierson labs aimed to block CD28 function directly in experiments on kidney and heart transplantation in baboons and monkeys. Previous work showed that down-regulation of CD28 activity with an anti-CD28 monoclonal antibody inhibited rejection of organ transplants in rodents. For the new nonhuman primate studies, the researchers used a fragment of a human CD28-specific monoclonal antibody fused to a carrier molecule to increase its half-life in vivo. This fusion antibody, sc28AT, recognizes CD28 from monkeys and baboons as well as humans, and it competes with CD80/86 for binding to CD28. sc28AT increased the number of functional Tregs and reduced chronic rejection of the transplanted tissue in the primates when used together with a calcineurin inhibitor. This is good news because it suggests that the dose of such inhibitors (and their toxic side effects) could be reduced in patients when given with a molecule targeting CD28. It remains to be determined whether this approach offers practical advantages over straight CD80/86 blockade when tested in the clinic. Transplantation is the treatment of choice for patients with end-stage organ failure. Its success is limited by side effects of immunosuppressive drugs, such as inhibitors of the calcineurin pathway that prevent rejection by reducing synthesis of interleukin-2 by T cells. Moreover, none of the existing drugs efficiently prevent the eventual rejection of the organ. Blocking the CD28-mediated T cell costimulation pathway is a nontoxic alternative immunosuppression strategy that is now achieved by blockade of CD80/86, the receptor for CD28 on antigen-presenting cells. However, interaction of CD80/86 with cytotoxic T lymphocyte–associated antigen 4 (CTLA-4) is required for immune regulation. Therefore, CD28 blockade, instead of CD80/86 blockade, might preserve regulatory signals mediated by CTLA-4 and preserve immune regulation. By using monovalent antibodies, we identified true CD28 antagonists that induced CTLA-4–dependent decreased T cell function compatible with regulatory T (Treg) cell suppression. In transplantation experiments in primates, blocking CD28 augmented intragraft and peripheral blood Treg cells, induced molecular signatures of immune regulation, and prevented graft rejection and vasculopathy in synergy with calcineurin inhibition. These findings suggest that targeting costimulation blockade at CD28 preserves CTLA-4–dependent immune regulation and promotes allograft survival.

Prognostic Value of Bone Scan in Patients With Metastatic Prostate Cancer Treated Initially With Androgen Deprivation Therapy

PURPOSE We analyzed whether classifying bone prostate cancer metastases correlates with survival in patients treated primarily with androgen deprivation. MATERIALS AND METHODS We identified 86 patients with bone metastases who were followed between September 1988 and September 1999. Only those treated initially with androgen deprivation as monotherapy were included in this study. Clinical, pathological and radiological information were obtained by patient chart review. The 86 patients were divided into 2 groups according to metastasis grade on bone scan at diagnosis. Group 1 included patients with metastases on the axial skeleton and group 2 included those with bone metastases on the appendicular skeleton. In addition to our classification, we stratified patients according to the Soloway and Crawford et al classifications, and analyzed survival. RESULTS There were no statistical differences in the groups with axial versus appendicular metastases in terms of patient age, biopsy Gleason score, serum prostate specific antigen or clinical stage. Median survival was 53 and 29 months in patients with axial and appendicular bone metastases, respectively. Those with axial disease had better survival than those with appendicular bone metastases (p = 0.048). No statistical difference was observed when grading bone scan according to the Soloway and Crawford et al classifications. CONCLUSIONS Classifying bone scans according to the site of metastases (axial versus appendicular) had many advantages. It is easy to understand and helps urologist better predict the patient prognosis. Axial metastases carries a better prognosis than appendicular metastasis.

Kidney and Recipient Weight Incompatibility Reduces Long-Term Graft Survival

Long-term function of kidney allografts depends on multiple variables, one of which may be the compatibility in size between the graft and the recipient. Here, we assessed the long-term consequences of the ratio of the weight of the kidney to the weight of the recipient (KwRw ratio) in a multicenter cohort of 1189 patients who received a transplant between 1995 and 2006. The graft filtration rate increased by a mean of 5.74 ml/min between the third and sixth posttransplantation months among patients with a low KwRw ratio (<2.3 g/kg; P<0.0001). In this low KwRw ratio group, the graft filtration rate remained stable between 6 months and 7 years but then decreased at a mean rate of 3.17 ml/min per yr (P<0.0001). In addition, low KwRw ratios conferred greater risk for proteinuria, more antihypertensive drugs, and segmental or global glomerulosclerosis. Moreover, a KwRw ratio<2.3 g/kg associated with a 55% increased risk for transplant failure by 2 years of follow-up. In conclusion, incompatibility between graft and recipient weight is an independent predictor of long-term graft survival, suggesting that avoiding kidney and recipient weight incompatibility may improve late clinical outcome after kidney transplantation.

Impact of graft mass on the clinical outcome of kidney transplants

The effect of nephronic mass reduction of kidney transplants has not been analyzed specifically in a large cohort. Transplant injuries in cadaver kidney graft may have led to an underestimation of the magnitude of this factor. The aim of this study was to analyze the consequences of kidney mass reduction on transplantation outcome. The weights of 1142 kidney grafts were collected prospectively immediately before grafting. Donors and recipients <15 yr of age, simultaneous kidney/pancreas grafts, and technical failures before day 7 were excluded from the analysis. The analysis was performed on Cockroft-calculated creatinine clearance and proteinuria in 964 patients for whom all of the necessary information was available. This study reports that the smallest kidneys transplanted into the largest recipients (donor kidney weight/recipient body weight [DKW/RBW] <2 g/kg, n = 88) increased their clearance by 2.38 ml/min every month for 6 mo (P < 0.0001) and by 0.27 ml/min thereafter (P < 0.0001). Conversely, creatinine clearance did not change for the largest kidneys transplanted into the smallest recipients (DKW/RBW ratios >/=4 g/kg). Next, using a Cox model analysis, it was shown that the risk of having a proteinuria >0.5 g/kg was significantly increased for the low DKW/RBW ratios <2 g/kg with 50% of patients having a proteinuria, compared with DKW/RBW ratios >/=4 g/kg (P < 0.001). In cadaver transplant recipients, graft mass has a rapid impact on graft filtration rate and proteinuria. Avoiding major kidney/recipient inadequacy should have a significant influence on long-term transplant function.

Recombinant human C1-inhibitor prevents acute antibody-mediated rejection in alloimmunized baboons

Acute antibody-mediated rejection is an unsolved issue in transplantation, especially in the context of pretransplant immunization. The deleterious effect of preformed cytotoxic anti-HLA antibodies through complement activation is well proven, but very little is known concerning complement blockade to prevent/cure this rejection. Here, we used a baboon model of preimmunization to explore the prevention of acute antibody-mediated rejection by an early inhibition of the classical complement pathway using human recombinant C1-inhibitor. Baboons were immunized against peripheral blood mononuclear cells from allogeneic donors and, once a specific and stable immunization had been established, they received a kidney from the same donor. Rejection occurred at day 2 posttransplant in untreated presensitized recipients, with characteristic histological lesions and complement deposition. As recombinant human C1-inhibitor blocks in vitro cytotoxicity induced by donor-specific antibodies, other alloimmunized baboons received the drug thrice daily intravenously during the first 5 days after transplant. Rejection was prevented during this treatment but occurred after discontinuation of treatment. We show here that early blockade of complement activation by recombinant human C1-inhibitor can prevent acute antibody-mediated rejection in presensitized recipients. This treatment could also be useful in other forms of acute antibody-mediated rejection caused by induced antibodies.

Prolonged Hydrodistention of the Bladder for Symptomatic Treatment of Interstitial Cystitis: Efficacy at 6 Months and 1 Year

OBJECTIVE To determine the efficacy of hydrodistention of the bladder for symptomatic treatment of interstitial cystitis after 6 months and 1 year of follow-up and to identify a predictive factor. METHODS The study included 65 consecutive patients (a first retrospective series of 33 and a second prospective series of 32) treated by hydrodistention of the bladder for urinary symptoms attributed to interstitial cystitis. All experienced pain on bladder filling, which was relieved by micturition or bladder voiding, and had more than two nocturias. Glomerulations were detected at short hydrodistention during cystoscopy. No patients were subject to NIH exclusion criteria. Hydrodistention was performed continuously for 3 h without rest intervals under epidural anesthesia using a balloon with a pressure equal to the patients mean arterial pressure. Efficacy was defined as the disappearance of pain on bladder filling or the persistence of moderate, non-disabling pain for which the patient did not request treatment, and a low frequency of nocturia (zero to two times). The efficacy period was estimated according to Kaplan-Meier methods for survival curves. The second series was used to verify the analytic results of the first series. RESULTS Treatment efficacy was 12/32 (37.7% CI: 20.7-54.3) at 6 months and 7/32 (21.9% CI: 7.6-36.2) at 1 year for the first series, and 18/30 (60.0% CI: 45.0-75.0) at 6 months and 13/30 (43.3% CI: 25.6-61.1) at 1 year for the second series. In both series, results were better for the subgroup of patients with a bladder capacity > or = 150 ml during cystometry before distention. CONCLUSIONS This study showed good but transient efficacy in the least developed or least severe forms of the disease.

LOW INCIDENCE OF KIDNEY REJECTION AFTER SIMULTANEOUS KIDNEY-PANCREAS TRANSPLANTATION AFTER ANTITHYMOCYTE GLOBULIN INDUCTION AND IN THE ABSENCE OF CORTICOSTEROIDS: RESULTS OF A PROSPECTIVE PILOT STUDY IN 28 CONSECUTIVE CASES

BACKGROUND Recipients of simultaneous kidney-pancreas transplantation receive a combination of polyclonal antithymocyte globulin (ATG), cyclosporin or tacrolimus, mycophenolate mofetil (MMF) and corticosteroids (Cs). To avoid the side effects and adverse events associated with Cs, we investigated a new immunosuppressive regimen without Cs after simultaneous kidney-pancreas transplantation. METHODS A total of 28 consecutive patients who underwent simultaneous kidney-pancreas transplantation were included in this study. All patients received ATG, cyclosporin, and MMF. RESULTS All patients but one tolerated the ATG course well. MMF was definitively discontinued in three patients because of leukopenia. Cytomegalovirus infection was diagnosed in eight patients (28.5%). Only two patients (7%) required an antirejection treatment. Patient, kidney, and pancreas survival is currently 96.4, 96.4, and 75%, respectively. CONCLUSIONS The combination of ATG, cyclosporin, and MMF, without Cs, was well tolerated. The unexpectedly low (7%) incidence of acute kidney rejection observed suggests that Cs may partially interfere with the immunosuppressive effect of ATG.

Late Ureteral Stenosis Following Renal Transplantation: Risk Factors and Impact on Patient and Graft Survival

The aim of this retrospective study of a cohort of 1787 consecutive kidney transplantations was to analyze the risk factors associated with the occurrence of ureteral stenosis and the impact of ureteral stenosis on graft and patient survival. Between January 1990 and December 2002, 1787 renal transplantations were performed at our center. Only stenosis observed after the first month, were considered. Among the parameters studied were: donor age and serum creatinine before procurement; recipient age, cold ischemia time, delayed graft function (DGF), number of arteries and the presence of a double J stent. The follow‐up parameters were the number and timing of acute rejection episodes, cytomegalovirus (CMV) infection, acute pyelonephritis, renal function and death. Ureteral stenosis occurred in 4.1% of patients and was correlated with donor age > 65 years (p = 0.001), kidneys with more than 2 arteries (p = 0.009) and DGF (p = 0.016). Ureteral stenosis did not affect 10‐year patient and graft survival rates, which were respectively 90% and 64% for the stenosis group, 86% and 63% for the no‐stenosis group (p = NS). These data suggest an important role for donor age, number of renal arteries and DGF for the occurrence of ureteral stenosis following renal transplantation.

Rapid failure of pig islet transplantation in non human primates

Abstract: We have previously demonstrated that adult pig islets of Langerhans are not destroyed in vitro by primate sera. Whether these islets can function when placed into the liver of non‐human primates is not known. We now report on the outcome of pig islet xenotransplantation into five non diabetic primates (four baboons and one macacus fascicularis) receiving intraportally purified adult pig islets. The average number of islet‐equivalent per graft was 110000 (60–180000). All animals received associations of ATG, cyclosporine or LF 195 (a deoxyspergualin analog), mycophenolate mofetil and corticosteroids. A specific porcine C‐peptide (C‐pep) RIA test was used to monitor insulin secretion. Two hours after grafting, porcine C‐peptide was positive (from 0.37 to 4.25 ng/ml) in all monkeys except one. Primate C‐pep was normal in all cases. Only two monkeys had detectable levels of porcine C‐pep on day 1 or 2 with undetectable levels thereafter, even after glucagon challenge between days 6 and 10. Several normal islets with moderate inflammatory infiltration were observed in one animal liver on day 2 (the time of necropsy) as well as islets with IgM and complement deposition. Among animals sacrificed on days 14, 16 and 38, some residual islet cells could be identified only in livers collected on day 14. Partial glycaemic control was achieved in some rats receiving islets from the same preparations. In conclusion, adult pig islets are not able to maintain insulin secretion for more than 24 h when injected intraportally into non diabetic immunosuppressed monkeys, suggesting immediate islet xenograft destruction.