Torque teno viral load reflects immunosuppression in paediatric kidney-transplanted patients-a pilot study.

BACKGROUND: Chronic deterioration of kidney graft function is related to inadequate immunosuppression (IS). A novel tool to assess the individual net state of IS in transplanted patients might be the monitoring of Torque teno virus (TTV) viral load. TTV is a non-pathogen virus detectable in almost all individuals. TTV level in the peripheral blood has been linked to the immune-competence of its host and should thus reflect IS after solid organ transplantation. METHODS: TTV plasma load was quantified monthly by RT-PCR for a period of 1 year in 45 kidney-transplanted children. Post-transplant time was at least 3 months. The relation of the virus DNA levels to IS and transplant-specific clinical and laboratory parameters was analysed longitudinally. RESULTS: TTV DNA was detectable in 94.5% of the plasma samples. There was a significant association with the post-transplant follow-up time as well as with the type of IS regimen, with lower virus loads in patients after longer post-transplant time and mTOR inhibitor-based IS. Furthermore, a significant positive correlation with the dose of prednisolone and mycophenolate mofetil was found. CONCLUSIONS: TTV levels show an association/correlation with the strength of IS. Further studies are needed in order to evaluate TTV measurement as a tool for IS monitoring for hard clinical outcomes such as presence of donor-specific antibodies, rejections or infections-common consequences of insufficient or too intense IS.

Donor-specific HLA antibodies and graft function in kidney-transplanted children - the Vienna cohort.

In the pediatric population, little is known on de novo DSA development, its impact on graft function, and association with suboptimal IS. We assessed the prevalence of de novo DSA in the Vienna cohort of 40 renal transplanted children and adolescents and prospectively followed its association with clinical parameters, graft function, and proteinuria for one yr. At the cross-sectional analysis (median post-transplant time of five yr), 17% of the patients had developed de novo DSA. All HLA-Ab were anti-HLA class II antibodies and persisted in 85% of the cases until the follow-up screening performed within one yr. Basic clinical and laboratory parameters did not differ between DSA-negative and DSA-positive patients at the time of HLA-Ab screening. Suboptimal IS due to reduced medication or non-adherence could not be proven in DSA-positive patients. The changes in eGFR did not differ during the prospective study period, but there was a significantly higher proteinuria in the DSA-positive patients during the follow-up. Our data demonstrate an overall prevalence of 17% of de novo DSA in a pediatric renal transplant cohort. During 12 months of prospective follow-up time, we could demonstrate a significant impact of de novo DSA presence on proteinuria.

Intracranial hypertension in siblings with infantile hypercalcemia.

BACKGROUND: Idiopathic intracranial hypertension is a clinical condition with elevated intracranial pressure of uncertain etiology. Although various underlying causes are suspected and familial occurrence has also been reported, however, it still remains an unexplained phenomenon. CASE REPORT: We report the case of dizygotic siblings with a known CYP24A1 mutation resulting in chronic hypercalcemia and impairment of kidney function. At the same point in time both of them developed intracranial hypertension resistant to conservative therapy necessitating therefore ventriculoperitoneal shunt implantation. In both children magnetic resonance imaging showed slightly hypoplastic sinus transversus as the potential underlying cause. CONCLUSION: The simultaneous clinical presentation could be due to a genetic factor or might be a component of the underlying disease or the consequence of its treatment. Further cases and clinical experience are needed to clarify this issue.

Characteristics, management, and outcome of pediatric patients with post-transplant lymphoproliferative disease-A 20 years' experience from Austria.

BACKGROUND: Management of pediatric post-transplantation lymphoproliferative disorder (PTLD) after hematopoietic stem cell (HSCT) and solid organ transplantation (SOT) is challenging. AIM: This study of 34 PTLD patients up to 19-years old diagnosed in Austria from 2000 to 2018 aimed at assessing initial characteristics, therapy, response, and outcome as well as prognostic markers of this rare pediatric disease. METHODS AND RESULTS: A retrospective data analysis was performed. Types of allografts were kidney (n = 12), liver (n = 7), heart (n = 5), hematopoietic stem cells (n = 4), lungs (n = 2), multi-visceral (n = 2), small intestine (n = 1), and vessels (n = 1). Eighteen/34 were classified as monomorphic PTLD, with DLBCL accounting for 15 cases. Polymorphic disease occurred in nine, and non-destructive lesions in six cases. One patient had a non-classifiable PTLD. Thirteen/34 patients are surviving event-free in first remission (non-destructive, n = 4/6; polymorphic, n = 4/9; monomorphic, n = 6/18). Fourteen/34 patients lacked complete response to first-line therapy, of whom seven died. Four/34 patients relapsed, of whom two died. In 3/34 patients, death occurred as a first event. The 5-year overall and event-free survival rates were 64% ± 9% and 35% ± 9% for the whole cohort. Among all parameters analyzed, only malignant disease as the indication for transplantation had a significantly poor influence on survival. CONCLUSIONS: This study shows PTLD still to be a major cause of mortality following SOT or HSCT in children. A continued understanding of the molecular biology of the disease shall allow to decrease treatment intensity for lower risk patients and to identify patients who may benefit from newer therapy approaches to improve outcome and decrease morbidity.

Preemptive plasma therapy prevents atypical hemolytic uremic syndrome relapse in kidney transplant recipients.

BACKGROUND: Atypical hemolytic uremic syndrome (aHUS) frequently leads to renal failure, and kidney transplantation bears a high risk of disease recurrence and graft loss. METHODS: Patients who received a kidney graft in our center were retrospectively identified using our Vienna Thrombotic Microangiopathy Cohort. Since 2005, the majority of aHUS patients received perioperative plasma exchange (PE) followed by plasma infusions (PI). Patients were switched to eculizumab in case of plasma intolerance or failure. Those with no preemptive therapy served as controls. We used proportional Cox regression and logistic regression to examine predictors of graft survival. RESULTS: 19 aHUS patients received 32 grafts and had a follow-up > 1 year. Eight patients received preventive plasma therapy for eight transplants and 13 patients (including 2 patients who received plasma therapy for their last transplant) had no preventive therapy for 24 grafts. The median graft survival was 2.372 days in patients, that received preemptive therapy and 411 days in patients, that did not receive preemptive treatment (hazard ratio: 0.11; p= 0.03). Four patients were switched to eculizumab because of plasma intolerance or failure. Additionally, one patient, that was not transplanted according to the above-mentioned protocol, received eculizumab for aHUS relapse. Additionally, relapse of aHUS (p = 0.01) and year of transplantation (p<0.01) had an effect on graft failure. CONCLUSIONS: This study shows that preemptive plasma therapy and eculizumab rescue in selected cases improve graft survival among kidney transplant recipients with aHUS.

PD-L1 and PD1 expression in post-transplantation lymphoproliferative disease (PTLD) of childhood and adolescence: An inter- and intra-individual descriptive study covering the whole spectrum of PTLD categories.

Therapy of children with post-transplantation lymphoproliferative disorder (PTLD) after hematopoietic stem cell (HSCT) and solid organ transplantation (SOT) can be challenging. In this retrospective study, we investigated PD-L1 and PD1 expression in all PTLD categories of childhood and adolescence to see whether checkpoint inhibition with PD-L1/PD1 inhibitors may serve as a therapy option. We included 21 patients aged 19 years or younger (at date of transplant) with PTLD following SOT or HSCT having adequate tumor samples available (n = 29). Using immunohistochemistry, we evaluated PD-L1/PD1 expression on both tumor cells and cells of the microenvironment in all samples. Availability of consecutively matched tumor samples during 6 of 21 patients' disease courses also allowed an intra-individual assessment of PD-L1/PD1 expression. We observed lower PD-L1 and higher PD1 expression in non-destructive lesions, and higher PD-L1 and lower PD1 expression in polymorphic and, in particular, in monomorphic PTLD, mostly diffuse large B-cell lymphomas (DLBCL, n = 10/21). The amount of PD-L1- and PD1-positive cells changed in the opposite way in sequential biopsies of the same individual correlating well with the PTLD category. This is the first comprehensive pediatric study assessing PD-L1 and PD1 expression on tumor cells and in the microenvironment of PTLD including not only monomorphic, but also non-destructive early lesions. PD-L1 expression of the tumor cells inversely correlated with PD1 expression in surrounding tissues, with the highest expression in DLBCL. Since PTLD can be therapeutically challenging, our results indicate a potential efficacy of checkpoint inhibitors if standard immune- and/or chemotherapy fail or are impossible. We therefore recommend routine staining of PD-L1 and PD1 in all PTLD categories.

Long-term outcome of pediatric renal transplantation in boys with posterior urethral valves.

PURPOSE: To determine whether there is a difference in the outcome of renal transplantation (RT) in patients with posterior urethral valves (PUV) and children with non-uropathy related end stage renal disease. METHODS: Data were acquired retrospectively. We analyzed possible factors that influence the function of renal allografts and graft survival. Between 1995 and 2016 there were 149 RT. Out of them, there were 27 boys with PUV, who received 29 kidneys. Thirty patients, who received a total of 31 renal grafts due to a non-uropathic (NU) diagnosis, served as control group. Mean follow-up was 7.4 to 10.2 years. RESULTS: There was no difference in estimated graft survival between patients with PUV and NU patients. Graft failure occurred in 23.1% of PUV patients and 34.5% patients of the NU group. There was no statistically significant disparity in graft function between the two groups. Age at transplantation and donor age were the only factors that had a significant impact on renal function. There was a higher incidence of UTI in the PUV group (96%) than in the NU group (67%). Vesicostomy was the favourable intervention in regards of graft function. CONCLUSIONS: RT in PUV patients is successful with the same outcome as in NU patients. Bladder dysfunction may not have a major impact on graft function and graft survival. It seems that the type of pre-transplant surgical procedures may influence outcome. Therefore, these interventions -if necessary- should be limited to a minimum. TYPE OF STUDY: Retrospective Comparative Study LEVEL OF EVIDENCE: Level III.

Functional characterization of two novel non-synonymous alterations in CD46 and a Q950H change in factor H found in atypical hemolytic uremic syndrome patients.

Atypical hemolytic uremic syndrome (aHUS) is a disease of complement dysregulation, characterized by hemolytic anemia, thrombocytopenia and acute renal failure. Mutations in complement inhibitors are major risk factors for development of aHUS. The three aHUS patients reported in this study had several previously identified alterations in complement inhibitors; e.g. risk haplotypes in CD46 and factor H but we also identified two novel heterozygous non-synonymous CD46 alterations (p.E142Q and p.G259V). Presence of G259V caused decreased expression of the recombinant mutant CD46 compared to wild type (WT). Western blot analysis showed that the majority of the expressed G259V protein was in the precursor form, suggesting that it is processed less efficiently than WT. Low CD46 expression on the surface of the patient's neutrophils confirmed the in vitro results. Further, G259V had a substantially impaired ability to act as a cofactor to factor I, in the degradation of both C3b and C4b. The E142Q mutant showed neither decreased expression nor impaired function. Two of the patients also had a heterozygous non-synonymous alteration in factor H (p.Q950H), reported previously in aHUS but not functionally tested. This variant showed moderately impaired function in hemolytic assays, both using patient sera and recombinant proteins. The recombinant Q950H also showed a somewhat decreased expression compared to WT but the complement inhibitory function in fluid phase was normal. Taken together, we report a novel CD46 alteration showing both a decreased protein expression and substantially impaired cofactor function (G259V) and another without an effect on expression or cofactor function (E142Q). Moreover, mild consequences of a previously reported aHUS associated rare variant in factor H (Q950H) was also revealed, underlining the clear need for functional characterization of each new aHUS associated mutation.

A Case of "Late-Onset" Idiopathic Infantile Hypercalcemia Secondary to Mutations in the CYP24A1 Gene.

OBJECTIVE: Mutations in the 24-hydroxylase gene, CYP24A1, have recently been reported to cause idiopathic infantile hypercalcemia (IIH), a rare disease presenting in the first year of life that is characterized by increased sensitivity to vitamin D, leading to severe symptomatic hypercalcemia. METHODS: We present a case report and review the relevant literature. RESULTS: A 24-year-old Caucasian man presented with repetitive signs of nephrolithiasis since the age of 18 years, hypercalciuria (17.1 mmol/24 h), slightly elevated serum calcium concentration (2.64 mmol/L), and inappropriately high levels of 1,25-dihydroxyvitamin D (101 pg/mL) in combination with suppressed levels of circulating parathormone (7.9 pg/mL). Exogenous vitamin D intoxication as well as granulomatous disease or malignancy were excluded. Genetic analysis revealed a loss-of-function mutation in CYP24A1. Of note, our patient denied any prior clinical signs of impaired calcium homeostasis during childhood. CONCLUSION: Here, we describe the exceptional case of a patient with hypercalciuria and recurrent nephrolithiasis secondary to mutations in CYP24A1, without any signs of IIH in childhood, indicating that the phenotypic spectrum includes mild "late-onset" disease that becomes symptomatic in adolescence. Therefore, reduced CYP24A1 activity should be considered as a possible reason for recurrent nephrolithiasis in adults.