Humoral immunity to SARS-CoV-2 in kidney transplant recipients and dialysis patients: IgA and IgG patterns unraveled after SARS-CoV-2 infection and vaccination.

BACKGROUND: Infection with SARS-CoV-2 in high-risk groups such as kidney transplant and dialysis patients is shown to be associated with a more serious course of the disease. Four years after the start of the COVID-19 pandemic, crucial knowledge on the immune responses in these patient groups is still lacking. Therefore, this study aimed at investigating the humoral immune response after a SARS-CoV-2 infection compared to vaccination as well as the evolution of immunoglobulins over time. METHODS: Kidney transplant recipients, patients on haemodialysis or on peritoneal dialysis and healthy controls were included in this longitudinal multicenter study. SARS-CoV-2 anti-RBD, anti-NP and anti-S1S2 immunoglobulin G (IgG) and A (IgA) as well as the neutralizing antibody capacity were measured. RESULTS: Kidney transplant recipients had a significantly better humoral response to SARS-CoV-2 after infection (86.4%) than after a two-dose mRNA vaccination (55.8%) while seroconversion was comparable in patients on haemodialysis after infection (95.8%) versus vaccination (89.4%). In individuals without prior COVID-19, the IgG levels after vaccination were significantly lower in kidney transplant recipients when compared to all other groups. However, the IgA titres remained the highest in this patient group at each time point, both after infection and vaccination. A history COVID-19 was associated with higher antibody levels after double-dose vaccination in all patient categories and, while decreasing, titres remained high six months after double-dose vaccination. CONCLUSION: Kidney transplant recipients had a more robust humoral response to SARS-CoV-2 following infection compared to a two-dose mRNA vaccination, while patients on haemodialysis exhibited comparable seroconversion rates. Notably, individuals with prior COVID-19 exhibited higher IgG levels in response to vaccination. Hybrid immunity is thus the best possible defence against severe COVID-19 disease and seems also to hold up for these populations. Next, it is not clear whether the higher IgA levels in the kidney transplant recipients is beneficial for neutralizing SARS-CoV-2 or if it is a sign of disease severity.

Long-term cardiovascular outcome of renal transplant recipients after early conversion to everolimus compared to calcineurin inhibition: results from the randomized controlled MECANO trial.

Long-term data on cardiovascular (CV) outcome of renal transplant recipients (RTR) on mTOR-i (mammalian Target Of Rapamycin-inhibitors) are scarce. In a sub-study of the MECANO trial we investigated changes in intima media thickness (IMT), CV risk profile, Major Adverse CV Events (MACE) and survival in RTR on a mTORi versus CNI based regimen. Patients (enrolled 361) were treated with (basiliximab) and triple IS (CsA-Cyclosporine A-(C), MPS (M), prednisolone (P)). At M6 patients were randomized (n = 224) to the CsA group (C, P, N = 89), MPS group (M, P, N = 39) EVL group (Everolimus, P, N = 96). At week 2, M6 and M 24, IMT measurements of the Common Carotid Artery were performed. Cardiovascular risk factors were assessed at baseline, 6 and 24 months of follow-up. Seven years survival and MACE-free survival probability were calculated by the Cardiovascular Risk Calculator for RTR. After 7 years of follow-up, incidence of cardiovascular events and patient survival were assessed. Mean IMT at baseline (N = 192), was 0.64 ± 0.14 mm. At M6 (N = 158), 0.66 ± 0.15, M24 IMT was 0.68 ± 0.15 (N = 95). No significant differences between groups concerning IMT, true CV events and mortality, CV risk profile, predicted MACE/Mortality were found between mTORi and CNI-based regimen after 7 years of follow-up.

The Association of Combined Total Kidney and Liver Volume with Pain and Gastrointestinal Symptoms in Patients with Later Stage Autosomal Dominant Polycystic Kidney Disease.

BACKGROUND: There is an ongoing debate if and how kidney and liver volume are associated with pain and gastrointestinal (GI) symptoms in autosomal dominant polycystic kidney disease (ADPKD) patients. Since both kidney and liver volume could interact, we investigated whether combined total kidney and liver volume had stronger associations with ADPKD-related pain and GI symptoms than the volumes of the organs separately. METHODS: We used baseline data from the DIPAK-1 study, which included ADPKD patients with an estimated glomerular filtration rate (eGFR) between 30 and 60 mL/min/1.73 m2. MR imaging was performed to measure height-adjusted total kidney volume (hTKV), height-adjusted total liver volume (hTLV) and the combination of both (height-adjusted total kidney liver volume [hTKLV]). RESULTS: Three hundred nine ADPKD patients were included with a mean age of 48 ± 7 years, 53% female, eGFR 50 ± 11 mL/min/1.73 m2 and median hTKV, hTLV and hTKLV of 1,095 (758-1,669), 1,173 (994-1,523) and 2,496 (1,972-3,352) mL/m, respectively. ADPKD-related pain and GI symptoms were present in, respectively, 27.5 and 61.2% of patients. Gender was no effect modifier in the association between kidney and/or liver volume, and symptom burden, indicating that all models could be tested in the overall study population. hTKLV and hTLV were significantly associated with pain and GI symptoms, whereas hTKV was not. Model testing revealed that the associations of pain and GI symptoms with hTKLV were significantly stronger than with hTKV (p = 0.04 and p = 0.04, respectively) but not when compared to hTLV (p = 0.2 and p = 0.5, respectively). CONCLUSIONS: This study indicates that combined kidney and liver volume was associated with the presence and severity of pain and GI symptoms in ADPKD, with a more prominent role for hTLV than for hTKV.

Simultaneous pancreas-kidney transplantation in patients with type 1 diabetes reverses elevated MBL levels in association with MBL2 genotype and VEGF expression.

AIMS/HYPOTHESIS: High levels of circulating mannan-binding lectin (MBL) are associated with the development of diabetic nephropathy and hyperglycaemia-induced vasculopathy. Here, we aimed to assess the effect of glycaemic control on circulating levels of MBL and the relationship of these levels with vascular damage. METHODS: We assessed MBL levels and corresponding MBL2 genotype, together with vascular endothelial growth factor (VEGF) levels as a marker of vascular damage, in type 1 diabetes patients with diabetic nephropathy before and after simultaneous pancreas-kidney (SPK) transplantation. We included diabetic nephropathy patients (n = 21), SPK patients (n = 37), healthy controls (n = 19), type 1 diabetes patients (n = 15) and diabetic nephropathy patients receiving only a kidney transplant (n = 15). Fourteen diabetic nephropathy patients were followed up for 12 months after SPK. RESULTS: We found elevated circulating MBL levels in diabetic nephropathy patients, and a trend towards elevated circulating MBL levels in type 1 diabetes patients, compared with healthy control individuals. MBL levels in SPK patients completely normalised and our data indicate that this predominantly occurs in patients with a polymorphism in the MBL2 gene. By contrast, MBL levels in kidney transplant only patients remained elevated, suggesting that glycaemic control but not reversal of renal failure is associated with decreased MBL levels. In line, levels of glucose and HbA1c, but not creatinine levels and estimated GFR, were correlated with MBL levels. VEGF levels were associated with levels of MBL and HbA1c in an MBL-polymorphism-dependent manner. CONCLUSIONS/INTERPRETATION: Taken together, circulating MBL levels are associated with diabetic nephropathy and are dependent on glycaemic control, possibly in an MBL2-genotype-dependent manner.

How delayed graft function impacts exposure to mycophenolic acid in patients after renal transplantation.

INTRODUCTION: Mycophenolic acid (MPA) plasma concentrations are highly variable on standard-dose mycophenolate mofetil therapy. At creatinine clearances below 25 mL/min, MPA clearance increases as a result of a higher nonprotein-bound fraction. Patients with delayed graft function (DGF) after renal transplantation are exposed to low total MPA concentrations, when risk of rejection is highest. This study investigated the influence of DGF on MPA exposure and on clinical outcome. METHODS: Adult renal transplantation patients treated with mycophenolate mofetil, corticosteroids, and either microemulsified cyclosporine (n = 459) or tacrolimus (n = 371) participated in a randomized controlled trial (the Fixed-Dose Concentration-Controlled [FDCC] Study). Abbreviated MPA areas under the curve (AUCs) were obtained on Day 3, Day 10, Week 4, and Month 3, to calculate MPA AUC0₋12. Free MPA AUC values were available for a subgroup of patients (n = 269). RESULTS: The overall incidence of DGF was 187 of 830 (23%) and did not differ between cyclosporine-treated (24%) and tacrolimus- (21%) treated patients. The incidence of biopsy-proven acute rejection at 12 months was significantly higher in patients with DGF (13.8% versus 21.4%). Patients with DGF had significantly lower dose-corrected MPA AUC on Day 3 and Day 10. Free MPA fraction and dose-corrected free MPA AUC were significantly higher in patients with DGF, from Day 3 until Month 3. The total number of patients with at least one opportunistic infection was significantly higher in patients with DGF (33.2%) compared with patients without DGF (25.8%) (P = 0.048). Patients with DGF developing opportunistic infections did not have higher total MPA AUC nor higher free MPA AUC compared with those without opportunistic infections. CONCLUSION: Patients with DGF have significantly lower dose-corrected MPA AUC in the first month after renal transplantation, presumably as a result of enhanced MPA clearance on account of the elevated MPA free fraction. Because patients with DGF have a higher rate of acute rejection and lower MPA exposure, higher dosing of mycophenolate mofetil in such patients may improve outcome. However, the already increased incidence of opportunistic infections in patients with DGF is a concern.

A Combined microRNA and Chemokine Profile in Urine to Identify Rejection After Kidney Transplantation.

There is an unmet need for noninvasive tools for diagnosis of rejection after kidney transplantation. The aim of this study was to determine the discriminative value of a combined cellular and molecular biomarker platform in urine for the detection of rejection. METHODS: First, microRNA (miR) molecules were screened in transplant biopsies and urine sediments of patients with acute rejection and patients without rejection and stable graft function. Second, the expression of 15 selected miRs was quantified in an independent set of 115 urine sediments of patients with rejection and 55 urine sediments of patients without histological signs of rejection on protocol biopsy. Additionally, CXCL-9 and CXCL-10 protein levels were quantified in the urine supernatant. RESULTS: Levels of miR-155-5p (5.7-fold), miR-126-3p (4.2-fold), miR-21-5p (3.7-fold), miR-25-3p (2.5-fold), and miR-615-3p (0.4-fold) were significantly different between rejection and no-rejection urine sediments. CXCL-9 and CXCL-10 levels were significantly elevated in urine from recipients with rejection. In a multivariable model (sensitivity: 89.1%, specificity: 75.6%, area under the curve: 0.94, P < 0.001), miR-155-5p, miR-615-3p, and CXCL-9 levels were independent predictors of rejection. Stratified 10-fold cross validation of the model resulted in an area under the curve of 0.92. CONCLUSIONS: A combined urinary microRNA and chemokine profile discriminates kidney transplant rejection from stable graft conditions.

Explaining variability in ciclosporin exposure in adult kidney transplant recipients.

PURPOSE: Optimal ciclosporin A (CsA) exposure in kidney transplant recipients is difficult to attain because of variability in CsA pharmacokinetics. A better understanding of the variability in CsA exposure could be a good means of individualizing therapy. Specifically, genetic variability in genes involved in CsA metabolism could explain exposure differences. Therefore, this study is aimed at identifying a relationship between genetic polymorphisms and the variability in CsA exposure, while accounting for non-genetic sources of variability. METHODS: De novo kidney transplant patients (n = 33) were treated with CsA for 1 year and extensive blood sampling was performed on multiple occasions throughout the year. The effects of the non-genetic covariates hematocrit, serum albumin concentration, cholesterol, demographics (i.e., body weight), CsA dose interval, prednisolone dose and genetic polymorphisms in genes encoding ABCB1, CYP3A4, CYP3A5, and PXR on CsA pharmacokinetics were studied using non-linear mixed effect modeling. RESULTS: The pharmacokinetics of CsA were described by a two-compartment disposition model with delayed absorption. Body weight was identified as the most important covariate and explained 35% of the random inter-individual variability in CsA clearance. Moreover, concurrent prednisolone use at a dosage of 20 mg/day or higher was associated with a 22% higher clearance of CsA, hence lower CsA exposure. In contrast, no considerable genotype effects (i.e., greater than 30-50%) on CsA clearance were found for the selected genes. CONCLUSIONS: It appears that the selected genetic markers explain variability in CsA exposure insufficiently to be of clinical relevance. Therefore, therapeutic drug monitoring is still required to optimize CsA exposure after administration of individualized doses based on body weight and, as this study suggests, co-administration of prednisolone.

Psychological Symptoms and Quality of Life After Simultaneous Kidney and Pancreas Transplantation.

Patients that have undergone successful simultaneous pancreas/kidney (SPK) transplantation attain normoglycemia and are free from dialysis. However, only a minor improvement in quality of life (QOL) has been demonstrated. Here, we evaluated the role of psychological symptoms in QOL after SPK transplantation. METHODS: We assessed patients with type 1 diabetes and end-stage renal disease waitlisted for SPK transplantation (pre-SPK, n = 47), and recipients of an SPK transplant (post-SPK, n = 72). Matched patients with type 1 diabetes without end-stage renal disease were included as reference group (type 1 diabetes [T1D] reference group, n = 42). The brief symptom inventory (BSI) was used to measure psychological symptoms. The Short Form-36 (SF-36) was used to determine QOL. RESULTS: Post-SPK patients scored slightly better on the SF-36 than pre-SPK patients ("General health" 47.2 ± 23.1 versus 37.5 ± 18.1 [P = 0.017]). In the T1D reference group, this score was 60.6 ± 22.3. Post- and pre-SPK patients had similar BSI scores (0.54 ± 0.55 and 0.45 ± 0.42, respectively [P = 0.34]). This score was better in the T1D reference group (BSI score 0.32 ± 0.33). The BSI score inversely correlated with the SF-36 (r = -0.61, P < 0.001). CONCLUSIONS: Psychological symptoms are prevalent in both pre-SPK and post-SPK patients and could play an important role in the reduced QOL observed in these groups.

Clinical utility of a new enzymatic assay for determination of mycophenolic acid in comparison with an optimized LC-MS/MS method.

The goal of this study was to investigate the clinical utility of a new enzymatic assay for use on COBAS INTEGRA systems (Roche Total MPA assay). From 134 patients, plasma mycophenolic acid (MPA) concentrations were measured with both the enzymatic method and a validated liquid chromatography with tandem mass spectrometry (LC-MS/MS) procedure, to compare these assays. The test principle of the enzymatic assay is inhibition of inosine monophosphate dehydrogenase. Method comparison studies revealed good agreement of results (r > 0.99), overall and in patients with delayed graft function or hypoalbuminemia. MPA area under the concentration-time curve (AUCs) obtained with LC-MS/MS (x) and the enzymatic method (y) compared excellent in patients on cyclosporine (y = 1.04x - 1.05, r = 0.992) or tacrolimus (y = 1.02x - 0.63, r = 0.987). MPA exposure determined with either method at different time points after transplantation agreed well (eg, 25th/50th/75th percentile of day 10 AUCs-LC-MS/MS: 25.8/33.8/45.2 versus enzymatic assay: 26.2/34.4/45.3 mg.h/L). AUCs calculated for both methods were lower at the first 3 time points in patients on cyclosporine compared with tacrolimus (week 4 median cyclosporine/tacrolimus: LC-MS/MS 39.6/56.4 versus enzymatic assay 40.5/56.0 mg.h/L). Both LC-MS/MS and the enzymatic methods revealed a tendency toward lower AUCs and predose levels in patients with biopsy-proven acute rejection (BPAR) (day 10 median: 0.9 mg/L with BPAR and 1.7 mg/L without BPAR). The Roche Total MPA assay is a reliable alternative to LC-MS/MS. It can be applied in the clinical setting allowing for easy, fast, and optimized patient management.

Preemptive versus Non-preemptive simultaneous pancreas-kidney transplantation: a single-center, long-term, follow-up study.

BACKGROUND: Data regarding the timing-before or after initiation of dialysis-of simultaneous pancreas-kidney transplantation (SPKT) in type 1 diabetes mellitus patients with end-stage renal failure are sparse. We studied the effect of preemptive transplantation on patient survival, cardiovascular endpoints, and graft survival, as compared with non-preemptive transplantation. METHODS: All 180 SPKT recipients (aged 23-58 years) who received a SPKT in Leiden between December 1986 and May 2004 were included in the analysis. Sixty-five patients (36.1%) were transplanted preemptively. Mean follow-up time was 6.3 years. RESULTS: Up to 8.2 years after transplantation, we found no differences in patient survival. Later on, divergence occurred: 10-year patient survival was 71.3% in the preemptive group versus 63.8% in the dialysis group and 15-year patient survival was 64.8% versus 45.1% in the dialysis group, leading to an adjusted hazard ratio for mortality of 0.50 (95% CI 0.23-1.06, P=0.070). Cause of death was less often of cardiac origin in the preemptive group (adjusted HR 0.16; 95% CI 0.026-0.95, P=0.044). Graft survival did not follow the same trend. No significant differences were found between the two groups considering allograft survival, cerebrovascular accident, or myocardial infarction. The percentage of patients with minor or major amputation(s) after transplantation was slightly lower in the preemptive group (24.6 vs. 32.1%; adjusted HR 0.87; 95% CI 0.42-1.82, P=0.72). CONCLUSION: Preemptive SPKT offered a patient survival benefit as compared with transplantation performed while already on dialysis and was associated with a lower rate of cardiac deaths.

The presence of betapapillomavirus antibodies around transplantation predicts the development of keratinocyte carcinoma in organ transplant recipients: a cohort study.

Organ transplant recipients (OTRs) have an increased risk of developing keratinocyte carcinomas (KCs). The aim of this study was to correlate infection with human papillomaviruses (HPVs) belonging to the beta genus (Beta-papillomavirus (Beta-PV)) at transplantation with later development of KCs. In a cohort study, sera collected between 1 year before and 1 year after transplantation of OTRs transplanted between 1990 and 2006 were tested for antibody responses against the L1 capsid antigen of Beta-PV and other HPV genera (Gamma-, Mu-, Nu-, and Alpha-PV) using multiplex serology. The OTRs were followed for a maximum of 22 years. Cox regression models with KC, squamous cell carcinoma (SCC), and basal cell carcinoma (BCC) as outcome variables were used. Out of 445 OTRs, 60 had developed KC: 14 developed only SCC, 24 only BCC, and 22 both types of KC. The time-dependent hazard ratio (HR) to develop either or both types of KC, adjusted for age, sex, and transplanted organ, in tested Beta-PV-seropositive OTR around the time of transplantation compared with Beta-PV-seronegative OTR was 2.9 (95% confidence interval (CI) 1.3-6.4). The HR for SCC was 2.9 (95% CI 0.99-8.5) and for BCC it was 3.1 (95% CI 1.2-8.0). There was also an association between Mu-PV seropositivity and KC, but there were no significant associations between other HPV genera tested and KC. A positive seroresponse for Beta-PV around transplantation significantly predicted the development of KC in OTRs up to 22 years later, providing additional evidence that infection with Beta-PV has a role in KC carcinogenesis.

Human Bone Marrow- and Adipose Tissue-derived Mesenchymal Stromal Cells are Immunosuppressive In vitro and in a Humanized Allograft Rejection Model.

BACKGROUND: Recent studies with bone marrow (BM)-derived Mesenchymal Stromal Cells (MSC) in transplant recipients demonstrate that treatment with MSC is safe and clinically feasible. While BM is currently the preferred source of MSC, adipose tissue is emerging as an alternative. To develop efficient therapies, there is a need for preclinical efficacy studies in transplantation. We used a unique humanized transplantation model to study the in vivo immunosuppressive effect of human BM-MSC and adipose tissue-derived MSC (ASC). METHODS: Gene expression of BM-MSC and ASC and their capacity to inhibit activated PBMC proliferation was evaluated. The in vivo immunosuppressive effect of BM-MSC and ASC was studied in a humanized mouse model. SCID mice were transplanted with human skin grafts and injected with human allogeneic PBMC with or without administration of BM-MSC or ASC. The effect of MSC on skin graft rejection was studied by immunohistochemistry and PCR. RESULTS: BM-MSC and ASC expressed TGFß, CXCL-10 and IDO. IDO expression and acitivity increased significantly in BM-MSC and ASC upon IFN-γ stimulation. IFN-γ stimulated BM-MSC and ASC inhibited the proliferation of activated PBMC in a significant and dose dependent manner. In our humanized mouse model, alloreactivity was marked by pronounced CD45+ T-cell infiltrates consisting of CD4+ and CD8+ T cells and increased IFN-γ expression in the skin grafts which were all significantly inhibited by both BM-MSC and ASC. CONCLUSION: BM-MSC and ASC are immunosuppressive in vitro and suppress alloreactivity in a preclinical humanized transplantation model.

Differential effect of pretransplant blood transfusions on immune effector and regulatory compartments in HLA-sensitized and nonsensitized recipients.

BACKGROUND: Blood transfusion (BT) may elicit both harmful and beneficial immune responses against a subsequent organ graft. Immune parameters of a single, non leukocyte-depleted BT were investigated in two groups: non-human leukocyte antigen (HLA)-sensitized recipients with a one-HLA-DR matched donor (protocolled BT [PBT]) and females with previous exposure to HLA alloantigens through pregnancy (donor-specific transfusion [DST]). METHODS: Thirty-five percent of DST recipients and 9.5% of PBT recipients developed HLA antibodies after BT.Phenotypic and functional analyses were performed in pre-BT, 2 weeks post-BT, and more than 10 weeks post-BT samples (PBT: n=10; DST: n=14). RESULT: The number of donor-reactive interferon-γ-producing memory T cells increased 2 weeks post-BT, but only in the DST group, increased frequencies persisted beyond 10 weeks (P0.004). In the DST recipients, the proportion of natural killer cells (CD3(-)CD56(+)) significantly increased after BT (P=0.01), whereas in PBT recipients, the proportion of regulatoryT cells (CD4(+)CD25(+)Foxp3(+)CD127 low) significantly increased at 2 weeks post-BT (P=0.039). Microarray analysis confirmed increased activity of genes involved in function of natural killer cells,Tcells, and Bcells in DSTrecipients and increased expression of immune regulatory genes (galectin-1, Foxo3a, and follistatin-like 3) in PBT recipients. Galectin-1 expression by quantitative polymerase chain reaction was significantly enhanced in peripheral blood cells after PBT (P0.05). CONCLUSION: Decreased immune effector mechanisms combined with an increased immune regulatory cell signature after HLA-DR-matched BT in nonsensitized patients is in line with clinical observations of improved outcome of a subsequent graft. Previous sensitization, however, may lead to HLA antibody formation and prolonged donor-specific memory T-cell reactivity after BT.

Minimization of maintenance immunosuppression early after renal transplantation: an interim analysis.

INTRODUCTION: Chronic allograft nephropathy is the main cause of long-term renal transplant failure. Chronic use of calcineurin inhibitors contributes to its pathogenesis. Here, we report on a multicenter randomized trial to study the effects of withdrawal of cyclosporine A (CsA) from a triple immunosuppressive regimen containing CsA, prednisolone (P), and mycophenolate sodium (MPS) early after transplantation. METHODS: Patients continued on P/CsA, P/MPS, or P and everolimus (EVL). Before withdrawal, a transplant biopsy was performed ensuring no subclinical rejection was present. Drug levels were closely monitored. The primary outcome was interstitial graft fibrosis and hyalinosis. Secondary outcome was among others graft rejection. RESULTS: According to trial regulations, an interim analysis was performed after enrollment of half of the intended number of patients (n=113). Mean follow-up was 14+/-5 months from transplantation and 8+/-5 months from conversion. After conversion, acute rejection percentages were 3% in the P/CsA group, 22% in the P/MPS group, and 0% in the P/EVL group (P<0.009). CONCLUSIONS: We conclude that switching immunosuppressive therapy from P/CsA/MPS to therapy with P/CsA or P/EVL at 6 months after renal transplantation is effective in preventing rejection. Double therapy with P/MPS after withdrawal of P/CsA resulted in an increase in severe acute rejection episodes. These results were the immediate reason to halt the P/MPS arm. Serum creatinine values at the latest follow-up (8+/-5 months after conversion and 14+/-5 months after transplantation) in the P/EVL group were lower than in the P/CsA group.

AcylMPAG plasma concentrations and mycophenolic acid-related side effects in patients undergoing renal transplantation are not related to the UGT2B7-840G>A gene polymorphism.

Mycophenolic acid (MPA) is metabolized primarily by glucuronidation to form the biologically inactive 7-O-glucuronide conjugate (MPAG), which is the major urinary excretion product. MPA is also converted to acyl-glucuronide metabolite (AcylMPAG), which has been suggested to be involved in the generation of MPA-related adverse events such as diarrhea or leucopenia. This conversion of MPA to AcylMPAG is catalyzed by UDP-glucuronosyltransferase 2B7 (UGT2B7). We studied the impact of the -840G>A polymorphisms in the UGT2B7 gene on the pharmacokinetics of AcylMPAG. We also investigated whether the plasma concentrations of AcylMPAG are correlated with MPA-related toxicity to further evaluate its potential clinical significance. In a randomized, controlled trial, comparing fixed-dose mycophenolate mofetil (MMF) with concentration-controlled MMF therapy, patients undergoing renal transplantation were treated with a calcineurin inhibitor, MMF, and corticosteroids. Informed consent was obtained from 332 patients for genotyping. In all patients, blood samples were drawn (three samples within the first 2 hours after administration) on Day 3, Day 10, Week 4, and Months 3, 6, and 12 to measure MPA and AcylMPAG plasma concentrations. The pharmacokinetics of AcylMPAG were correlated with the -840G>A single nucleotide polymorphism (SNP) in the UGT2B7 gene. Heterozygosity for the -840G>A SNP in the UGT2B7 gene was found in 145 patients (145 of 332 [44%]) and 93 (93 of 332 [28%]) patients were homozygous for the -840G>A allele. No difference was found in the dose-normalized AcylMPAG trough (C0) levels and dose-normalized AcylMPAG areas under the concentration-time curve (AUCs) at each visit between carriers and noncarriers of the -840G>A SNP. Also, metabolic ratios, expressed as AcylMPAG/MPA and AcylMPAG/MPAG, were not related to UGT2B7 genotype. The dose-normalized AcylMPAG-C0 and AcylMPAG AUC were higher in the cyclosporine-treated group compared with the tacrolimus-treated patients at each visit. There was no difference in AcylMPAG concentrations (trough or AUC) or AcylMPAG/MPAG ratio between patients with compared with patients without diarrhea. None of the -840G>A UGT2B7 SNPs was disproportionately present among the patients with diarrhea. There was a higher incidence of diarrhea in tacrolimus-treated patients [26 of 163 (16.0%)] compared with cyclosporine-treated individuals [five of 51 (9.8%)], although AcylMPAG concentrations were lower in tacrolimus-treated patients. In this study, we have found no influence of the -840G>A UGT2B7 SNP on AcylMPAG exposure in patients undergoing renal transplantation. There also was no association between this variant genotype and the incidence of diarrhea or leucopenia, two adverse events for which a role for AcylMPAG has been suggested.

Gallstone formation after pancreas and/or kidney transplantation: an analysis of risk factors.

Pancreas and kidney transplantation (SPK) is the treatment of choice for patients with type 1 diabetes mellitus and end-stage renal failure. Gallstones are common after SPK transplantation but little is known about the true incidence and etiology of gallstones in this group. We therefore evaluated the incidence of gallstones and the presence of transplant-related risk factors in patients after SPK and kidney transplantation alone (KTA). Data were evaluated of 56 consecutive patients who underwent SPK transplantation and compared the results with those of 91 consecutive nondiabetic patients who underwent KTA transplantation at the Leiden University Medical Center between 1987 and 1994. Of the 58 evaluable KTA patients, 20.7% developed gallstones during 7.7 yr of follow-up and in the SPK group 43.9% of the 41 evaluable patients developed gallstones during 7.1 yr of follow-up. Postoperative weight loss and cyclosporin A-related hepatotoxicity correlated with gallstone formation both in SPK and KTA patients. In addition, the duration of postoperative fasting and autonomic neuropathy correlated with gallstones in SPK patients. It is concluded that both in patients after SPK transplantation and in patients after KTA transplantation, the risk to develop gallstones is significantly increased. Physicians should be aware of the high incidence of gallstones in SPK recipients.

The influence of obesity on short- and long-term graft and patient survival after renal transplantation.

To determine short- and long-term patient and graft survival in obese [body mass index (BMI) >or= 30 kg/m(2)] and nonobese (BMI < 30 kg/m(2)) renal transplant patients we retrospectively analyzed our national-database. Patients 18 years or older receiving a primary transplant after 1993 were included. A total of 1,871 patients were included in the nonobese group and 196 in the obese group. In the obese group there were significantly more females (52% vs. 38.6%, P < 0.01) and patients were significantly older [52 years (43-59) vs. 48 years (37-58); P < 0.05]. Patient survival and graft survival were significantly decreased in obese renal transplant recipients (1 and 5 year patient survival were respectively 94% vs. 97% and 81% vs. 89%, P < 0.01; 1 and 5 year graft survival were respectively 86% vs. 92% and 71% vs. 80%, P < 0.01). Initial BMI was an independent predictor for patient death and graft failure. This large retrospective study shows that both graft and patient survival are significantly lower in obese renal transplant recipients.

HLAMatchmaker-based strategy to identify acceptable HLA class I mismatches for highly sensitized kidney transplant candidates.

HLAMatchmaker determines HLA compatibility at the level of polymorphic amino acid triplets in antibody-accessible sequence positions. Recent studies have shown that among HLA-DR-matched kidney transplants, the HLA-A,B antigen mismatches which are compatible at the triplet level have almost identical graft survival rates as the zero-HLA-A,B antigen mismatches. This finding provides the basis of a new strategy to identify HLA-mismatched organs that have similar success rates as the zero-HLA-antigen mismatches. This report describes how in conjunction with the Acceptable Mismatch program in Eurotransplant, HLAMatchmaker can expand the pool of potential donors for highly sensitized patients, for whom it is very difficult to find a compatible transplant. Sera from 35 highly sensitized kidney transplant candidates with an average PRA of 96% were screened by lymphocytotoxicity with HLA-typed panels that included cells that were selectively mismatched for one or two HLA antigens for each patient. Acceptable and unacceptable HLA-A,B antigen mismatches were determined from the serum reactivity with the cell panel. HLAMatchmaker analysis was applied to identify additional HLA class I antigens that were matched at the triplet level. For each patient, we calculated the probability of finding a donor (PFD) in the different match categories from HLA gene frequencies in the kidney donor population. The median PFD for a zero-antigen mismatch was 0.025%. Matching at the triplet level increased the median PFD to 0.037% ( P = 0.008). The median PFD was 0.058% for a 0-1-triplet mismatch and 0.226% for a 0-2-triplet mismatch. Serum screening identified acceptable antigen mismatches for 28 of 35 highly sensitized patients, and the median PFD increased to 0.307% for a zero/acceptable antigen mismatch. The application of HLAMatchmaker permitted for 33 patients (or 92%) the identification of additional antigens that were acceptable at the triplet level, and the median PFD for a zero/acceptable triplet mismatch went up to 0.425%. Inclusion of one-triplet mismatches increased the median PFD to 1.112%. Validation studies have shown that patient sera reacted with none of the zero-triplet-mismatched antigens, 8-13% of the one-triplet mismatches, and 12-19% of the two-triplet mismatches. Although most antigens with one or two mismatched triplets appear acceptable to highly sensitized patients, a serum analysis must ascertain that the patient's antibodies do not recognize such mismatched triplets. HLAMatchmaker offers a useful strategy of identifying more donors with acceptable HLA mismatches and could alleviate the problem of accumulation of highly sensitized patients on the transplant waiting list.