Abanti Chaudhuri

Circulating urokinase receptor as a cause of focal segmental glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) is a cause of proteinuric kidney disease, compromising both native and transplanted kidneys. Treatment is limited because of a complex pathogenesis, including unknown serum factors. Here we report that serum soluble urokinase receptor (suPAR) is elevated in two-thirds of subjects with primary FSGS, but not in people with other glomerular diseases. We further find that a higher concentration of suPAR before transplantation underlies an increased risk for recurrence of FSGS after transplantation. Using three mouse models, we explore the effects of suPAR on kidney function and morphology. We show that circulating suPAR activates podocyte β3 integrin in both native and grafted kidneys, causing foot process effacement, proteinuria and FSGS-like glomerulopathy. Our findings suggest that the renal disease only develops when suPAR sufficiently activates podocyte β3 integrin. Thus, the disease can be abrogated by lowering serum suPAR concentrations through plasmapheresis, or by interfering with the suPAR–β3 integrin interaction through antibodies and small molecules targeting either uPAR or β3 integrin. Our study identifies serum suPAR as a circulating factor that may cause FSGS.

Subclinical cytomegalovirus and Epstein–Barr virus viremia are associated with adverse outcomes in pediatric renal transplantation

Abstract:  Post‐transplant clinical disease with cytomegalovirus (CMV) and Epstein–Barr virus (EBV) is a known risk factor for graft dysfunction and lymphoproliferation. We postulate that subclinical, asymptomatic viremia also adversely impacts outcomes, and may warrant re‐assessment of current monitoring and antiviral prophylaxis protocols. A single‐center study was conducted on 102 pediatric (51 steroid‐free and 51 matched steroid‐based historical controls). Quantitative viral loads were serially monitored and correlated with outcome measures. Overall, the incidence of CMV and EBV clinical disease was 5% (1% CMV and 4% EBV); however, the incidence of subclinical viremia was 44% (12.7% CMV, 38.2% EBV, 6.9% CMV + EBV). Risk factors for subclinical viremia were EBV naivety (p = 0.07), age less than five yr (p = 0.04), lack of prophylaxis (p = 0.01), and steroid usage (p = 0.0007). Subclinical viremia was associated with lower three‐yr graft function (p = 0.03), increased risk of acute rejection (odds ratio 2.07; p = 0.025), hypertension (p = 0.04), and graft loss (p = 0.03). Subclinical asymptomatic CMV and EBV viremia is a risk factor for graft injury and loss. These findings support the need for aggressive, serial viral monitoring to better determine the appropriate length of post‐transplant antiviral prophylaxis, and to determine the effect of immunosuppression protocols on the development of viremia.

The Clinical Impact of Humoral Immunity in Pediatric Renal Transplantation

The development of anti-donor humoral responses after transplantation associates with higher risks for acute rejection and 1-year graft survival in adults, but the influence of humoral immunity on transplant outcomes in children is not well understood. Here, we studied the evolution of humoral immunity in low-risk pediatric patients during the first 2 years after renal transplantation. Using data from 130 pediatric renal transplant patients randomized to steroid-free (SF) or steroid-based (SB) immunosuppression in the NIH-SNSO1 trial, we correlated the presence of serum anti-HLA antibodies to donor HLA antigens (donor-specific antibodies) and serum MHC class 1-related chain A (MICA) antibody with both clinical outcomes and histology identified on protocol biopsies at 0, 6, 12, and 24 months. We detected de novo antibodies after transplant in 24% (23% of SF group and 25% of SB group), most often after the first year. Overall, 22% developed anti-HLA antibodies, of which 6% were donor-specific antibodies, and 6% developed anti-MICA antibody. Presence of these antibodies de novo associated with significantly higher risks for acute rejection (P=0.02), chronic graft injury (P=0.02), and decline in graft function (P=0.02). In summary, antibodies to HLA and MICA antigens appear in approximately 25% of unsensitized pediatric patients, placing them at greater risk for acute and chronic rejection with accelerated loss of graft function. Avoiding steroids does not seem to modify this incidence. Whether serial assessments of these antibodies after transplant could guide individual tailoring of immunosuppression requires additional study.

Role of Twenty-Four-Hour Ambulatory Blood Pressure Monitoring in Children on Dialysis

BACKGROUND AND OBJECTIVES Pre- or postdialysis BP recordings are imprecise, can be biased, and have poor test-retest reliability in children on dialysis. We aimed to examine the possible differences between pre- and postdialysis BP levels and 24-hour ambulatory BP monitoring (ABPM) in diagnosis of hypertension (HTN). DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS Twenty-four children on dialysis had 24-hour ABPM in the interdialytic period, and values were compared with average pre- and postdialysis systolic BP (SBP) and diastolic BP (DBP) recordings that week. Each patient had an echocardiogram to determine presence of left ventricular hypertrophy (LVH). RESULTS By ABPM, 8% of patients had white coat HTN and 12% had masked HTN. There was no significant difference in diagnosis of systolic HTN based on ABPM daytime SBP mean or load and postdialysis SBP. However, only 15% of patients had diastolic HTN based on postdialysis measures, whereas 46% of patients had significantly elevated daytime DBP loads and 71% had high nighttime DBP loads on ABPM. Forty-eight percent of patients were SBP nondippers. Children with LVH had higher daytime and nighttime SBP loads, significantly higher daytime and nighttime DBP loads, and lesser degree of nocturnal dipping of SBP compared with those who did not. CONCLUSION ABPM is more informative than pre- and postdialysis BPs and improves the predictability of BP as a risk factor for target organ damage. Diagnosis and treatment monitoring of HTN among pediatric dialysis patients is enhanced with addition of ABPM.

Compartmental Localization and Clinical Relevance of MICA Antibodies after Renal Transplantation

Background. Antibodies (Ab) responses to major and minor human leukocyte antigen loci may impact graft survival after organ transplantation. Methods. A ProtoArray platform was used to study 37 serum samples from 15 renal transplant patients with (n=10) and without (n=5) acute rejection (AR) and seven normal controls, and the clinical relevance of major histocompatibility complex class I chain-related gene-A (MICA)-Ab measurements were investigated. Biopsy immunohistochemistry was conducted for localization of the MICA antigen. Results. De novo MICA-Ab were detected in 11 of the 15 transplant patients in this study, irrespective of interval acute graft rejection. Mean MICA-Ab signal intensity was higher in transplant patients with C4d+AR (121.4) versus C4d−AR (4.3), correlated with donor-specific Ab to human leukocyte antigens (r=0.66, P=0.0078), was not elevated in cellular rejections, and correlated with decline in graft function over the subsequent year (r=0.73, P=0.0022). Integrative genomics accurately predicted localization of the MICA antigen to the glomerulus in the normal kidney (Li et al. Proc Natl Acad Sci USA 2009; 106: 4148), because this was confirmed subsequently by immunohistochemistry. Conclusions. Integrative genomics analysis of ProtoArray data is a powerful tool to ascertain de novo antibody responses after renal transplantation and to accurately predict the anatomical location of the target renal antigens. This proof-of-concept study on MICA measurements by ProtoArray demonstrates that antibody responses modulated to MICA after transplantation in patients, irrespective of graft rejection, may be high at the time of humoral rejection and may not be elevated in cellular rejection. Understanding that MICA is preferentially localized to the glomerulus may explain both immunoregulatory and pathogenic roles for MICA after transplantation.

Efficacy and safety of thymoglobulin induction as an alternative approach for steroid-free maintenance immunosuppression in pediatric renal transplantation.

Background. Given the recent withdrawal of daclizumab (DAC), the safety and efficacy of thymoglobulin (TMG) was tested as an alternative induction agent for steroid-free (SF) immunosuppression in pediatric kidney transplant recipients. Methods. Thirteen pediatric renal transplant recipients meeting defined high-risk criteria at transplantation were offered TMG induction and SF immunosuppression with maintenance mycophenolate mofetil and tacrolimus between October 2008 and January 2010. Patients were closely monitored at baseline, 3, 6, 9, and 12 months posttransplant for protocol biopsy and clinical outcomes. Outcomes were compared with 13 consecutively transplanted low-risk patients receiving an established DAC-based SF protocol (Sarwal et al., WA, American Transplant Congress 2003). Results. There was a significant trend for overall decrease in the absolute lymphocyte counts in TMG group (F=5.86, mixed model group effect P=0.02), predominately at 3 months compared with DAC group (0.7±0.6 vs. 2.1±1.0, P=0.0004); however, lymphocyte count was recovered and was back to reference range by 6 months in TMG. There was trend toward more subclinical cytomegalovirus (15% vs. 0%) and BK viremia (17% vs. 0%) in the TMG group, with no differences in the incidence of subclinical Epstein Barr virus viremia (23% vs. 31%) or clinical viral disease. Mean graft function was excellent, and with a minimum follow-up of 6 months, there were no episodes of acute rejection. Conclusion. TMG seems to be a safe alternative induction strategy in patients for SF immunosuppression in pediatric renal transplantation. Extended follow-up and greater enrollment are necessary to fully explore the impact of TMG dosing on viral replication posttransplantation.

Use of eculizumab and plasma exchange in successful combined liver-kidney transplantation in a case of atypical HUS associated with complement factor H mutation

BackgroundAtypical hemolytic uremic syndrome (aHUS) evolves into end-stage renal failure in nearly half of affected patients and is associated with defective regulation of the alternative complement pathway. Patients with a complement factor H (CFH) mutation have a 30–100% risk of graft loss due to aHUS recurrence or graft thrombosis. Since CFH is produced predominantly by the liver, combined liver–kidney transplant is a curative treatment option. One major unexpected risk includes liver failure secondary to uncontrolled complement activation. We report a successful combined liver–kidney transplantation with perioperative plasma exchange and use of the humanized anti-C5 monoclonal antibody eculizumab.Case Diagnosis/TreatmentAn 11-month-old female presented with oliguric renal failure after 3 weeks of flu-like symptoms in the absence of diarrhea. Following the identification of Escherichia coli 0157:H7 in her stool, she was discharged home on peritoneal dialysis with a diagnosis of Shiga toxin-associated HUS. Three months later, she developed severe anemia, thrombocytopenia, and neurological involvement. aHUS was diagnosed and confirmed, and genetic testing revealed a mutation in CFH SCR20. Once donor organs became available, she received preoperative plasma exchange followed by eculizumab infusion with intra-operative fresh frozen plasma prior to combined liver–kidney transplant. At 19 months post-transplant, she continues to have excellent allograft and liver function without signs of disease recurrence.ConclusionPerioperative use of eculizumab in conjunction with plasma exchange during simultaneous liver–kidney transplant can be used to inhibit terminal complement activity, thereby optimizing successful transplantation by reducing the risk of graft thrombosis.

Option of pre-emptive nephrectomy and renal transplantation for Bartter's syndrome

Abstract:  Bartters syndrome (BS) is an incurable genetic disease, with variable response to supportive therapy relating to fluid and electrolyte management. Poor control or therapy non‐compliance may result in frequent life threatening episodes of dehydration, acidosis and hypokalemia, with resultant adverse effects on patient quality of life (QOL). We report, for the first time, pre‐emptive bilateral native nephrectomies and successful renal transplantation, prior to the onset of ESRD, for severe, clinically brittle, neonatal BS, resulting in correction of metabolic abnormalities and excellent graft function. We propose that fragile BS should be considered as a possible indication for early native nephrectomies and pre‐emptive renal transplantation, procedures that results in a ‘cure’ for the underlying disease and significant improvements in patient QOL.

Pediatric ambulatory blood pressure monitoring: diagnosis of hypertension

Pediatric hypertension (HTN) is a growing concern and should be diagnosed and treated aggressively to reduce the global disease burden. Ambulatory blood pressure monitoring (ABPM) is a useful clinical tool providing a more accurate description of the patient’s blood pressure (BP) than office BP measurements, and can be considered the “gold standard” in the evaluation of the pediatric patient with a concern for HTN. The American Heart Association have suggested criteria for diagnosing ambulatory HTN, and research continues into further clarification of how to best utilize the large volume of data obtained from an ABPM report. ABPM has some limitations; however, the advantages far outweigh these. Routine use of ABPM is recommended among clinicians to better evaluate and assess the severity of a child’s HTN, and for proper management in order to prevent target organ damage and the resulting sequelae, thereby reducing the burden of cardiovascular risk in hypertensive children and adolescents.

Immune cell function assay does not identify biopsy-proven pediatric renal allograft rejection or infection

Management of pediatric renal transplant patients involves multifactorial monitoring modalities to ensure allograft survival and prevent opportunistic infection secondary to immunosuppression. An ICFA, which utilizes CD4 T‐cell production of ATP to assess immune system status, has been used to monitor transplant recipients and predict susceptibility of patients to rejection or infection. However, the validity of this assay to reflect immune status remains unanswered. In a two‐yr retrospective study that included 31 pediatric renal transplant recipients, 42 patient blood samples were analyzed for immune cell function levels, creatinine, WBC (white blood cell) count, immunosuppressive drug levels, and viremia, concurrent with renal biopsy. T‐cell ATP production as assessed by ICFA levels did not correlate with allograft rejection or with the presence or absence of viremia. ICFA levels did not correlate with serum creatinine or immunosuppressive drug levels, but did correlate with WBC count. The ICFA is unreliable in its ability to reflect immune system status in pediatric renal transplantation. Further investigation is necessary to develop methods that will accurately predict susceptibility of pediatric renal transplant recipients to allograft rejection and infection.