Association of CYP3A variants with kidney transplant outcomes

Cyclosporine is used extensively in kidney transplantation and is a substrate for cytochrome P450 enzymes. The role of cytochrome p450 polymorphisms in kidney transplant outcome has not yet been fully elucidated. We investigate the clinical impact of single nucleotide polymorphisms in CYP3A4, CYP3A5, PPARα, and POR*28 in 255 kidney transplant recipients. We examine for any association with graft survival, time to first cancer, and delayed graft function, and also measure cyclosporine levels at days 3, 10, and months 1, 3, 6, and 12 after transplantation. The CYP3A4*22 allele is significant associated with the development of cancer post-kidney transplantation (HR 0.20, 95% CI 0.07-0.57, p = 0.003). It is not significantly associated with graft survival. No other SNP's were associated with graft survival time to first cancer, or delayed graft function. There was a non-significant trend of lower cyclosporine dose requirement in CYP3A4*22 carriers. Independent replication of our findings is now warranted to confirm or reject the role of CYP3A variants in cancer development following kidney transplantation.

Factors affecting eGFR 5-year post-deceased donor renal transplant: analysis and predictive model

AIM

Long-term survival of renal allografts has improved over the last 20 years. However, less is known about current expectations for long-term allograft function as determined by estimated glomerular filtration rate (eGFR). The aim of this study was to investigate factors which affect graft function at 5 years' post-renal transplantation. The statistically significant factors were then used to construct a predictive model for expected eGFR at five years' post-transplant.

METHODS

We retrospectively reviewed all adult patients who received a renal transplant in the Republic of Ireland between 1990 and 2004. Data collected included era of transplantation (1990-1994, 1995-1999, 2000-2004), donor and recipient age and gender, number of human leucocyte antigen mismatches, cold ischemia time (CIT), number of prior renal transplants, immunosuppressive regimen used and acute rejection episodes. Estimated GFR was calculated at 5 years after transplantation from patient data using the Modified Diet in Renal Disease (MDRD) equation. Consecutive sampling was used to divide the study population into two equal unbiased groups of 489 patients. The first group (derivation cohort) was used to construct a predictive model for eGFR five years' post-transplantation, the second (validation cohort) to test this model.

RESULTS

Nine hundred and seventy eight patients were analyzed. The median age at transplantation was 43 years (range 18-78) and 620 (63.4%) were male. One hundred and seventy five patients (17.9%) had received a prior renal transplant. Improved eGFR at five years' post-transplantation was associated with tacrolimus-based combination immunosuppression, younger donor age, male recipient, absence of cytomegalovirus disease and absence of acute rejection episodes as independently significant factors (p < 0.05). The predictive model developed using these factors showed good correlation between predicted and actual median eGFR at five years. The model explained 20% of eGFR variability. The validation model findings were consistent with the derivation model (21% variability of eGFR explained by model using same covariates on new data).

CONCLUSION

The predictive model we have developed shows good correlation between predicted and actual median eGFR at five years' post-transplant. Applications of this model include comparison of current and future therapy options such as new immunosuppressive regimens.

A novel missense mutation of Wilms' Tumor 1 causes autosomal dominant FSGS

FSGS is a clinical disorder characterized by focal scarring of the glomerular capillary tuft, podocyte injury, and nephrotic syndrome. Although idiopathic forms of FSGS predominate, recent insights into the molecular and genetic causes of FSGS have enhanced our understanding of disease pathogenesis. Here, we report a novel missense mutation of the transcriptional regulator Wilms' Tumor 1 (WT1) as the cause of nonsyndromic, autosomal dominant FSGS in two Northern European kindreds from the United States. We performed sequential genome-wide linkage analysis and whole-exome sequencing to evaluate participants from family DUK6524. Subsequently, whole-exome sequencing and direct sequencing were performed on proband DNA from family DUK6975. We identified multiple suggestive loci on chromosomes 6, 11, and 13 in family DUK6524 and identified a segregating missense mutation (R458Q) in WT1 isoform D as the cause of FSGS in this family. The identical mutation was found in family DUK6975. The R458Q mutation was not found in 1600 control chromosomes and was predicted as damaging by in silico simulation. We depleted wt1a in zebrafish embryos and observed glomerular injury and filtration defects, both of which were rescued with wild-type but not mutant human WT1D mRNA. Finally, we explored the subcellular mechanism of the mutation in vitro. WT1(R458Q) overexpression significantly downregulated nephrin and synaptopodin expression, promoted apoptosis in HEK293 cells and impaired focal contact formation in podocytes. Taken together, these data suggest that the WT1(R458Q) mutation alters the regulation of podocyte homeostasis and causes nonsyndromic FSGS.

Manifestations of Von Hippel Lindau syndrome: a retrospective national review

INTRODUCTION

Von Hippel Lindau (VHL) disease is a syndrome that is defined by variety of tumours such as cerebellar haemangioblastomas, renal cell carcinomas, phaeochromocytomas, pancreatic adenomas and ear, nose and throat (ENT) adenomas. This disease is often genetic and inherited in an autosomal dominant fashion, and can present in childhood, adolescence or adult life. This study describes the presentation, natural history and manifestations of patients attending our institutions with this condition. We aim to highlight the importance of screening in diagnosing the manifestations of VHL.

METHODS

A retrospective review was performed on all patients diagnosed with VHL and coded as such by the national Hospital Inpatient Enquiry Scheme at Beaumont Hospital Dublin and Cork University Hospital. This was performed over a 20 years period between 1989 and 2009. Age, sex, mode of presentation, presence or absence of end stage kidney disease and genotype were documented. Presence or absence of the characteristic tumours of VHL was also recorded, as were the initial presenting features of these tumours.

RESULTS

Thirty-six patients were diagnosed with VHL. These patients ranged from 18 to 78 years old. Three patients were members of the Irish travelling community. The most frequent mode of presentation was altered neurological signs (40%), with a significant proportion presenting with haematuria (23%). Patients diagnosed prior to 1995 were more likely to have presented with significant complications of VHL, while those diagnosed after this time were more likely to have been diagnosed via screening. Genetic testing was performed on 17 patients; those who did not have genetic testing performed were more likely to have been diagnosed prior to the era of genetic testing. Thirty-one patients had received screening for complications of VHL including renal cell carcinomas, central nervous system (CNS) haemangioblastomas and phaeochromocytomas. The patients who did not receive any screening presented with neurological symptoms.

CONCLUSION

Beaumont Hospital Dublin and Cork University Hospital are tertiary referral centres for nephrology, urology and neurosurgery and deals with a significant proportion of patients diagnosed with VHL in Ireland. This study highlights the significant burden of this illness and emphasizes the importance of screening for these renal/CNS and ENT complications. This study also highlights the importance of family screening in diagnosing this condition.

C3 glomerulopathy: clinicopathologic features and predictors of outcome

BACKGROUND AND OBJECTIVES

The term C3 glomerulopathy describes renal disorders characterized by the presence of glomerular deposits composed of C3 in the absence of significant amounts of Ig. On the basis of electron microscopy appearance, subsets of C3 glomerulopathy include dense deposit disease (DDD) and C3 glomerulonephritis (C3GN). The full spectrum of histologic change observed in C3 glomerulopathy has yet to be defined and pathologic predictors of renal outcome within this patient population remain largely unknown. This study thus characterized a large C3 glomerulopathy cohort and identified clinicopathologic predictors of renal outcome.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

All patients with kidney biopsies fulfilling criteria for C3 glomerulopathy from two quaternary renal centers within the United Kingdom and Ireland between 1992 and 2012 were retrospectively reviewed. We recorded histologic, demographic, and clinical data and determined predictors of ESRD using the Cox proportional hazards model.

RESULTS

Eighty patients with C3 glomerulopathy were identified: 21 with DDD and 59 with C3GN. Patients with DDD were younger, more likely to have low serum C3 levels, and more likely to have crescentic GN than patients with C3GN. Patients with C3GN were older and had more severe arteriolar sclerosis, glomerular sclerosis, and interstitial scarring than patients with DDD. Of 70 patients with available follow-up data, 20 (29%) progressed to ESRD after a median of 28 months. Age >16 years, DDD subtype, and crescentic GN were independent predictors of ESRD within the entire cohort. Renal impairment at presentation predicted ESRD only among patients with DDD.

CONCLUSIONS

Although detailed serologic and genetic data are lacking, this study nevertheless identifies important clinicopathologic distinctions between patients with DDD and C3GN. These include independent predictors of renal outcome. If replicated in other cohorts, these predictors could be used to stratify patients, enabling application of emerging mechanism-based therapies to patients at high risk for poor renal outcome.

Recurrence of anti-neutrophil cytoplasmic antibody-associated vasculitis in appropriately immunosuppressed renal transplant patients: a discussion of two cases

Background

Granulomatosis with polyangiitis (GPA) (formerly known as Wegener's granulomatosis) is a multisystem autoimmune disease of unknown aetiology. Renal disease manifests as a crescentic glomerulonephritis, with varying degrees of renal failure. Ten percent of patients progress to end-stage kidney disease. Relapse of GPA in renal transplant patients is rare, with a rate of 0.09 relapses per patient per year.

Patients and Methods

We describe two cases of GPA relapse in immunosuppressed renal transplant patients.

Results

These patients presented with new-onset graft disfunction, having previously had an uncomplicated posttransplant course. Both patients were on appropriate doses of immunosuppressive agents at the time of relapse, with therapeutic target levels of tacrolimus. We describe the background history and management of both patients.

Conclusion

The cases described inform us that although recurrence of anti-neutrophil cytoplasmic antibody vasculitis in transplant patients is rare, it should remain on our list of differential diagnoses in allograft disfunction.

Twenty-year survivors of kidney transplantation

There have been few studies of patients with renal allografts functioning for more than 20 years. We sought to identify clinical factors associated with ultra long-term (>20 year) renal allograft survival and to describe the clinical features of these patients. We performed a retrospective analysis of the Irish Renal Transplant Database and included 1174 transplants in 1002 patients. There were 255 (21.74%) patients with graft function for 20 years or more. Multivariate analysis identified recipient age (HR 1.01, CI 1.01-1.02), gender (male HR 1.25, CI 1.08-1.45), acute rejection (HR 1.26, CI 1.09-1.45) and transplant type (living related donor vs. deceased donor) (HR 0.52, CI 0.40-0.66) as significantly associated with long-term graft loss. Median serum creatinine was 115 μmol/L. The 5-year graft survival in 20-year survivors was 74.7%. The mean age at death was 62.7 years (±10.6). The most common causes of death were cardiovascular disease and malignancy. The two major causes of graft loss were death (with function) and interstitial fibrosis/tubular atrophy. Comorbidities included skin cancer (36.1%), coronary heart disease (17.3%) and other malignancies (14.5%). This study identifies factors associated with long-term allograft survival and a high rate of morbidity and early mortality in long-term transplant recipients.

Arterio-venous fistula buttonhole cannulation technique: a retrospective analysis of infectious complications

BACKGROUND

There are two main methods of accessing arterio-venous fistulas (AVFs); the 'buttonhole' and the 'rope-ladder' cannulation technique. Several small studies have hypothesized that the buttonhole technique is associated with increased rates of fistula-associated infection. This study addresses this hypothesis.

METHODS

A retrospective review of all patients attending a large outpatient haemodialysis clinic was performed. Data were collected on the method of cannulation, infection rates, implicated microorganisms, complications of infection and time on haemodialysis.

RESULTS

A total of 127 patients had received haemodialysis via an AVF: 53 via the rope-ladder technique and 74 via the buttonhole technique. Nine episodes of clinically significant bacteraemia were recorded in the buttonhole group. This equated to a rate of 0.073 bacteraemia events per 1000 AVF days. There were no episodes of bacteraemia in the rope-ladder group. Eight infections were due to methicillin-sensitive Staphylococcus aureus (MSSA); one was due to Staphylococcus epidermidis. Three patients with MSSA bacteraemia subsequently developed infective endocarditis. Five patients who developed bacteraemia events had been undergoing home haemodialysis.

CONCLUSIONS

This study highlights the infectious complications associated with buttonhole cannulation techniques. All organisms isolated in our cohort were known skin colonizers. The reason for the increased rates of infection is unclear. Given this high rate of often life-threatening infection, we recommend regular audit of infection rates. We currently do not recommend this technique to our patients receiving haemodialysis.

Concordance of outcomes of pairs of kidneys transplanted into different recipients

Kidney transplant outcomes are influenced by donor characteristics, including age and gender. Additional donor factors, both genetic and environmental, also influence graft outcome. We aim to assess the strength of donor factors in determining kidney transplant outcomes by comparing paired kidneys from a single donor transplanted into different recipients. We conducted a retrospective cohort study of outcomes of pairs of deceased donor kidneys transplanted in our centre between 1992 and 2008. We examined the relationship within pairs for eGFR at 1 year and at 5 years post-transplant using Spearman's Correlation and the concordance of pairs of transplant kidneys with respect to the occurrence of acute rejection and delayed graft function (DGF). A total of 652 recipient pairs were analysed. Spearman's correlation for eGFR was 0.36 at 1 year and 0.36 at 5 years post-transplant. The incidence of DGF was 11%. The odds ratio of DGF occurring if the contralateral kidney had DGF was 5.99 (95% CI, 3.19-11.25). There is a significant degree of relationship within pairs of kidneys transplanted from the same donor for serum creatinine at 1 year and 5 years post-transplant and also for the occurrence of delayed graft function.

Re-infection following sustained virological response with a different hepatitis C virus genotype: implications for infection control policy

We report the case of a 45-year-old haemodialysis patient who achieved a sustained virological response (SVR) following pegylated interferon therapy for hepatitis C virus (HCV) genotype 2 infection. He was subsequently cohorted with other HCV-infected dialysis patients and became re-infected with HCV genotype 3a. Epidemiological and molecular investigations identified a highly viraemic HCV genotype 3a-infected dialysis patient as the likely source of this infection. This critical incident informed a revision to local and national infection control policy regarding the dialysis management of patients who achieve an SVR following anti-viral treatment.

A hybrid CFHR3-1 gene causes familial C3 glomerulopathy

Controlled activation of the complement system, a key component of innate immunity, enables destruction of pathogens with minimal damage to host tissue. Complement factor H (CFH), which inhibits complement activation, and five CFH-related proteins (CFHR1-5) compose a family of structurally related molecules. Combined deletion of CFHR3 and CFHR1 is common and confers a protective effect in IgA nephropathy. Here, we report an autosomal dominant complement-mediated GN associated with abnormal increases in copy number across the CFHR3 and CFHR1 loci. In addition to normal copies of these genes, affected individuals carry a unique hybrid CFHR3-1 gene. In addition to identifying an association between these genetic observations and complement-mediated kidney disease, these results provide insight into the protective role of the combined deletion of CFHR3 and CFHR1 in IgA nephropathy.

A 12-year review of Staphylococcus aureus bloodstream infections in haemodialysis patients: more work to be done

Staphylococcus aureus bloodstream infections (BSI) are a significant cause of morbidity and mortality in haemodialysis patients. This study describes a 12-year retrospective review of S. aureus BSI in a large haemodialysis centre in a tertiary referral hospital. The overall rate of S. aureus BSI was 17.9 per 100 patient-years (range 9.7-36.8). The rate of meticillin-resistant S. aureus (MRSA) BSI was 5.6 per 100 patient-years (range 0.9-13.8). Infective complications occurred in 11% of episodes, the most common being infective endocarditis (7.6%). Ten percent of patients died within 30 days of S. aureus being isolated from blood. Most cases of S. aureus BSI (83%) were related to vascular catheters. The provision of lower-risk vascular access, such as arteriovenous fistulae, and reduced use of intravascular catheters should be priorities in all haemodialysis units. Where alternative vascular access cannot be established, interventions to reduce the risk of catheter-related infections should be implemented to reduce morbidity and mortality in this vulnerable patient group.

Pleuroperitoneal leak complicating peritoneal dialysis: a case series

Pressure related complications such as abdominal wall hernias occur with relative frequency in patients on peritoneal dialysis. Less frequently, a transudative pleural effusion containing dialysate can develop. This phenomenon appears to be due to increased intra-abdominal pressure in the setting of congenital or acquired diaphragmatic defects. We report three cases of pleuroperitoneal leak that occurred within a nine-month period at our institution. We review the literature on this topic, and discuss management options. The pleural effusion resolved in one patient following drainage of the peritoneum and a switch to haemodialysis. One patient required emergency thoracocentesis. The third patient developed a complex effusion requiring surgical intervention. The three cases highlight the variability of this condition in terms of timing, symptoms and management. The diagnosis of a pleuroperitoneal leak is an important one as it is managed very differently to most transudative pleural effusions seen in this patient population. Surgical repair may be necessary in those patients who wish to resume peritoneal dialysis, or in those patients with complex effusions. Pleuroperitoneal leak should be considered in the differential diagnosis of a pleural effusion, particularly a right-sided effusion, in a patient on peritoneal dialysis.

An assessment of the long-term health outcome of renal transplant recipients in Ireland

BACKGROUND

Renal transplantation remains the preferred method of renal replacement therapy in terms of patient survival, quality of life and cost. However, patients have a high risk of complications ranging from rejection episodes, infection and cancer, amongst others.

AIMS AND METHODS

In this study, we sought to determine the long-term health outcomes and preventive health measures undertaken for the 1,536 living renal transplant patients in Ireland using a self-reported questionnaire. Outcomes were divided into categories, namely, general health information, allograft-related information, immunosuppression-related complications and preventive health measures.

RESULTS

The results demonstrate a high rate of cardiovascular, neoplastic and infectious complications in our transplant patients. Moreover, preventive health measures are often not undertaken by patients and lifestyle choices can be poor.

CONCLUSIONS

This study highlights the work needed by the transplantation community to improve patient education, adjust immunosuppression where necessary and aggressively manage patient risk factors.

A prospective study of hepatitis B vaccination - a comparison of responders versus nonresponders

Herein we present one of the largest single-center reports of the response of hemodialysis patients to a two-vaccine hepatitis B virus vaccination protocol in a European dialysis population. A hepatitis B recombinant DNA vaccine, HBvaxPRO, was given at a dose of 40 µg intramuscularly using a four-dose schedule at 0, 1, 2, and 12 months. Responses were (1) a titer >100 mIU/mL = patient immune, (2) a titer level 10-99 mIU/mL = give a booster dose and recheck level 2 months later, and (3) 0 ≤ 10 mIU/mL = repeat vaccination course using a different vaccine, Engerix-B. We compared responder groups in terms of titer levels for each vaccine and variables including age, gender, serum albumin, parathyroid hormone (PTH), calcium, phosphate, hemoglobin, years on dialysis, and type of dialysis access. Of the 176 patients who received the first vaccine course, 71 patients achieved immunity, that is, 40% uptake for the first vaccine. Of the 105 who failed, 72 received the second vaccine with 46 responders, that is, 64% uptake for the second vaccine. Overall, 143 of the 176 patients who entered the vaccination program completed the protocol with 117 achieving immunity, representing an 82% success rate. The only variable overall to show significance in achieving seroconversion was serum albumin (p = 0.03). Using a two-vaccine protocol, hepatitis B vaccination response was high in our population of end-stage renal disease patients.

Identification of β2-microglobulin as a urinary biomarker for chronic allograft nephropathy using proteomic methods

PURPOSE

Chronic allograft nephropathy (CAN) remains the leading cause of renal graft loss after the first year following renal transplantation. This study aimed to identify novel urinary proteomic profiles, which could distinguish and predict CAN in susceptible individuals.

EXPERIMENTAL DESIGN

The study included 34 renal transplant patients with histologically proven CAN and 36 patients with normal renal transplant function. High-throughput proteomic profiles were generated from urine samples with three different ProteinChip arrays by surface-enhanced laser-desorption/ionization time-of-flight mass spectrometry (SELDI-TOF-MS). Following SELDI, a biomarker pattern software analysis was performed which led to the identification of a novel biomarker pattern that could distinguish patients with CAN from those with normal renal function.

RESULTS

An 11.7 kDa protein identified as β2 microglobulin was the primary protein of this biomarker pattern, distinguishing CAN from control patients (receiver operator characteristic [ROC]=0.996). SELDI-TOF-MS comparison of purified β2 microglobulin protein and CAN urine demonstrated identical 11.7 kDa protein peaks. Significantly, higher concentrations of 2 microglobulin were found in the urine of patients with CAN compared with the urine of normal renal function transplant recipients (p<0.001).

CONCLUSIONS AND CLINICAL RELEVANCE

Although further validation in a larger more diverse patient population is required to determine if this β2 microglobulin protein biomarker will provide a potential means of diagnosing CAN by noninvasive methods in a clinical setting, this study clearly shows a capability to stratify control and disease patients.

Mycophenolate mofetil in low-risk renal transplantation in patients receiving no cyclosporine: a single-centre experience

BACKGROUND

We assess our long-term experience with regards the safety and efficacy of Mycophenolate Mofetil (MMF) in our low risk renal transplant population and compared it retrospectively to Azathioprine (AZA) immunosuppressive regimen. Patients and methods. Between January 1999 and December 2005, 240 renal transplants received MMF as part of their immunosuppressive protocol (MMF group). AZA group of 135 renal transplants was included for comparative analysis (AZA group). Patients received Cyclosporine was excluded from this study.

RESULTS

The incidence of biopsy proven 3-month acute rejections was 30 (12.5%) in MMF group and 22 (16%) in AZA group respectively (P = 0.307). Patient survival rates at 1 and 5 years for the MMF group were 97 and 94%, respectively, compared to 100% and 91% at 1 and 5 years respectively for the AZA group (P = 0.61). Graft survival rates at 1 and 5 years for the MMF group were 95 and 83%, respectively, compared to 97 and 84% at 1 and 5 years, respectively for the AZA group (P = 0.62).

CONCLUSION

There was no difference in acute rejection episodes between MMF and AZA based immunotherapy. Additionally, we observed no significant difference concerning graft survival in the MMF group when compared to AZA group.