Optimizing COVID-19 Vaccination Strategy in Pediatric Kidney Transplant Recipients: Humoral and Cellular Response to SARS-CoV-2 mRNA Vaccination

In this retrospective cohort study, we analyze the early humoral and cellular response in 64 adolescents KTx recipients, after two or three doses of mRNA vaccine BNT162b2 against different variants of COVID-19. After 2 doses, 77.8% % of children with no history of infection had a positive humoral response with a median anti-S IgG level of 1107 (IQR, 593-2,658) BAU/mL. All the patients with a history of infection responded with a higher median IgG level (3,265 (IQR, 1,492-8,178) BAU/mL). In non-responders after 2 doses, 75% responded after a third dose with a median Ab titer at 355 (IQR, 140-3,865 BAU/mL). Neutralizing activity was significantly lower against the delta and the omicron variants compared to the wild-type strain and did not improve after a 3rd dose, while infection did provide higher levels of neutralizations against the variants. T cell specific response correlated with humoral response and no patient displayed a cellular response without a humoral response. Adolescent KTx recipients exhibit a high seroconversion rate after only two doses. A third injection, induces a response in the majority of the non-responders patients but did not counterbalance the strong decrease in neutralizing antibody activities against variants highlighting the need for boosters with specific vaccines.

Induction therapy for pediatric onset class IV lupus nephritis: Mycophenolate Mofetil versus Cyclophosphamide

OBJECTIVES

Class IV lupus nephritis (LN) is one of the most frequent and severe types of involvement in pediatric systemic lupus erythematosus. Gold standard treatment consists of intravenous (i.v.) Cyclophosphamide (CYC) associated with corticosteroids. Recent studies in adults have shown similar efficacy of oral Mycophenolate Mofetil (MMF) with fewer adverse events. Our aim was to compare the efficacy and tolerance of CYC and MMF as induction therapy in children with class IV LN.

METHODS

We conducted a retrospective study of children diagnosed with class IV LN who started oral MMF or i.v. CYC treatment at Necker Enfants Malades Hospital (Paris, France).

RESULTS

The study included 33 patients, 17 treated with oral MMF (51%) and 16 with i.v. CYC (48%). The characteristics at treatment induction did not significantly differ between the two groups except for the neurological involvement, that was only present in the CYC group. Complete remission was obtained in 9/17 (53%) children treated with MMF versus 10/16 (71%) treated with CYC (p = 0.46). Relapse was observed in 59% of patients receiving MMF versus 50% receiving CYC (p = 0.87), after a median of 3.4 years and 4.7 years after the beginning of treatment, respectively (p = 0.41). During the 6.5 years of follow-up, we observed no significant difference regarding the number of treatment-related adverse events between the two groups (p = 0.48).

CONCLUSION

We report similar efficacy and tolerance of MMF or CYC as induction therapy of class IV LN in children. However, the long-term adverse events such as infertility could not be systematically evaluated in this retrospective pediatric study. Overall, however, considering the long-term safety profile reported in the literature, we suggest that MMF may be used as first-line induction therapy in LN.

Diagnostic and therapeutic management of vesico-ureteral reflux in pediatric kidney transplantation-Results of an online survey on behalf of the European Society for Paediatric Nephrology

BACKGROUND

Vesico-ureteral reflux (VUR) is considered to be a risk factor for recurrent febrile urinary tract infections and impaired renal transplant survival.

METHODS

An online survey supported by the European Society for Paediatric Nephrology was designed to evaluate current management strategies of VUR in native and transplanted kidneys of recipients aged <18 years.

RESULTS

Seventy-three pediatric transplant centers from 32 countries contributed to the survey. All centers performed urological evaluation prior to pediatric kidney transplantation (KTx) with subsequent interdisciplinary discussion. Screening for VUR in native kidneys (30% in all, 70% in selected patients) led to surgical intervention in 78% (11% in all, 89% in selected patients) with a decided preference of endoscopic intervention over ureterocystoneostomy. Following KTx, continuous antibiotic prophylaxis was applied in 65% of the patients and screening for allograft VUR performed in 93% of selected patients. The main management strategies of symptomatic allograft VUR were continuous antibiotic prophylaxis (83%) and surgical treatment (74%) (endoscopic intervention 55%, redo ureterocystoneostomy 26%).

CONCLUSIONS

This survey demonstrates the high variability in the management of VUR in pediatric KTx recipients, points to knowledge gaps, and might serve as a starting point for improving the care for patients with VUR in native and transplanted kidneys.

Human kidney-derived hematopoietic stem cells can support long-term multilineage hematopoiesis

Long-term multilineage hematopoietic donor chimerism occurs sporadically in patients who receive a transplanted solid organ enriched in lymphoid tissues such as the intestine or liver. There is currently no evidence for the presence of kidney-resident hematopoietic stem cells in any mammal species. Graft-versus-host-reactive donor T cells promote engraftment of graft-derived hematopoietic stem cells by making space in the bone marrow. Here, we report full (over 99%) multilineage, donor-derived hematopoietic chimerism in a pediatric kidney transplant recipient with syndromic combined immune deficiency that leads to transplant tolerance. Interestingly, we found that the human kidney-derived hematopoietic stem cells took up long-term residence in the recipient's bone marrow and gradually replaced their host counterparts, leading to blood type conversion and full donor chimerism of both lymphoid and myeloid lineages. Thus, our findings highlight the existence of human kidney-derived hematopoietic stem cells with a self-renewal ability able to support multilineage hematopoiesis.

Prednisolone pharmacokinetics after oral prednisone administration in paediatric patients with kidney transplant

AIMS

Glucocorticoids are 1 of the primary treatments in paediatric kidney transplantation. The aims of this study were: (i) to build a population pharmacokinetics (PPK) model of free prednisolone, which is the active form of prednisone, in paediatric kidney transplant recipients; (ii) to identify covariates accounting for interindividual variability (IIV) of pharmacokinetics (PK) parameters; and (iii) to investigate drug exposure-safety relationships.

METHODS

Ninety-seven samples were obtained from 39 paediatric kidney transplant recipients (aged 3.4-17.2 years) in order to investigate prednisone PPK. We selected children receiving oral prednisone as part of their immunosuppressive regimen. A PPK analysis was performed using Monolix.

RESULTS

A 1-compartment model best described prednisolone concentrations. Large IIV was observed as prednisolone was undetectable at H12 in some patients but could still be detected at H24 in others. Both bodyweight and ciclosporin cotreatment influenced the PK. The clearance (CL_U ) and volume of distribution of free prednisolone allometrically scaled to 70 kg were 27.6 L/h and 101 L. Ciclosporin cotreatment decreased CL_U by 67%. High blood pressure and new onset diabetes after transplantation were associated with daily free prednisolone exposure.

CONCLUSION

This study is the first analysis of prednisolone PPK in kidney-transplanted children. Some of the IIV in the PK parameters was explained by bodyweight and ciclosporin cotreatment. These data suggest that dose adjustment is required after identifying variability factors to optimize efficacy and limit side effects. The use of therapeutic drug monitoring in kidney-transplanted children may be useful, especially with respect to safety issues.

MO1039: 1-Year Follow-Up Data of Arterial Abnormalities Identified in Kidneys Transplanted into Children During the First Covid-19 Pandemic Wave

BACKGROUND AND AIMS

Graft artery stenosis can have a significant short- and long-term negative impact on kidney graft function. We previously reported an unusual number of graft-arterial anomalies following kidney transplantation (KTx) in children during the first coronavirus disease (COVID-19) pandemic wave (Berteloot et al.) [1]. We report herein the 1-year follow-up of these patients.

METHOD

In this retrospective study, we included all children who received a KTx at our centre from February to July 2020. We compared their outcome to that of paediatric recipients who were transplanted at our centre from 2015 to 2019 and presented an allograft vascular complication (‘Historic’ group) by querying our local data warehouse.

RESULTS

Among the 9 children who received a KTx at our centre between February and July 2020 [8 boys, median age 10 years (3–17)], 8 presented Doppler features suggesting arterial stenosis, with an unusual extensive pattern (Figure 1) after a median delay of 13 days (8–113). For comparison, persistent spectral Doppler arterial anomalies were observed in only 5% of children following KTx at our centre over the previous 5-year period and were all focal anastomotic stenoses. In addition, five children had lymphoceles, which required surgical management as compared to only one patient in the 5 previous years (1%).  We retrospectively diagnosed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-20 infection in 6/8 children with arterial stenosis on serologies performed at D0, including one boy with a history of positive real time reverse transcription-polymerase chain reaction (RT-PCR) 120 days before KTx. None of the patients had reported any symptom suggestive of COVID-19. The remaining two patients had received a graft from an asymptomatic deceased adolescent donor with a positive serology at D0. These data led us to suspect immune post-viral graft vasculitis, triggered by SARS-CoV-2.

At 1-year post-transplantation, the outcome was favourable in the 8 isolated KTx recipients. A total of 4/8 children had normal blood pressure and 4 had controlled high blood pressure on mono or bi-therapy. Doppler anomalies had resolved in 5/8 and persisted in 3/8 with a trend for improvement of peak systolic velocities and no severe consequences on kidney function and histology. Indeed, the median glomerular filtration rate (GFR) was 91 mL/min/1.73 m² (65–129), with unspecific and mild lesions on 4/8 protocol kidney biopsies (IFTA 1 or Cpt 1). One liver-kidney graft recipient had persistent hypertension and diffuse irregular inflammatory parietal thickening of the whole vascular graft associated with a parietal thrombus upstream of the birth of the two hepatic arteries (Figure 2); treated with anti-aggregation and prednisone 10 mg/d.

CONCLUSION

Our case series suggests a risk of post-viral kidney graft vasculitis in children with recent SARS-CoV-2 infection in the recipient or donor. Pre-transplant vaccination against COVID-19 is mandatory in children > 5 years and their kidney donor candidates at our centre. We also strongly recommend vaccination of all people aged > 5 years in the household.

Arterial abnormalities identified in kidneys transplanted into children during the COVID-19 pandemic

Graft artery stenosis can have a significant short- and long-term negative impact on renal graft function. From the beginning of the COVID-19 pandemic, we noticed an unusual number of graft arterial anomalies following kidney transplant (KTx) in children. Nine children received a KTx at our center between February and July 2020, eight boys and one girl, of median age of 10 years. Seven presented Doppler features suggesting arterial stenosis, with an unusual extensive pattern. For comparison, over the previous 5-year period, persistent spectral Doppler arterial anomalies (focal anastomotic stenoses) following KTx were seen in 5% of children at our center. We retrospectively evidenced severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in five of seven children with arterial stenosis. The remaining two patients had received a graft from a deceased adolescent donor with a positive serology at D0. These data led us to suspect immune postviral graft vasculitis, triggered by SARS-CoV-2. Because the diagnosis of COVID-19 is challenging in children, we recommend pretransplant monitoring of graft recipients and their parents by monthly RT-PCR and serology. We suggest balancing the risk of postviral graft vasculitis against the risk of prolonged dialysis when considering transplantation in a child during the pandemic.

Dynamic prediction models for graft failure in paediatric kidney transplantation

BACKGROUND

Several models have been proposed to predict kidney graft failure in adult recipients but none in younger recipients. Our objective was to propose a dynamic prediction model for graft failure in young kidney transplant recipients.

METHODS

We included 793 kidney transplant recipients waitlisted before the age of 18 years who received a first kidney transplantation before the age of 21 years in France in 2002-13 and survived >90 days with a functioning graft. We used a Cox model including baseline predictors only (sex, age at transplant, primary kidney disease, dialysis duration, donor type and age, human leucocyte antigen matching, cytomegalovirus serostatus, cold ischaemia time and delayed graft function) and two joint models also accounting for post-transplant estimated glomerular filtration rate (eGFR) trajectory. Predictive performances were evaluated using a cross-validated area under the curve (AUC) and R2 curves.

RESULTS

When predicting the risk of graft failure from any time within the first 7 years after paediatric kidney transplantation, the predictions for the following 3 or 5 years were accurate and much better with the joint models than with the Cox model (AUC ranged from 0.83 to 0.91 for the joint models versus 0.56 to 0.64 for the Cox model).

CONCLUSION

Accounting for post-transplant eGFR trajectory strongly increased the accuracy of graft failure prediction in young kidney transplant recipients.

Association between 25(OH) vitamin D and graft survival in renal transplanted children

BACKGROUND

In children, vitamin D deficiency is common after renal transplantation. Besides promoting bone and muscle development, vitamin D has immunomodulatory effects, which could protect kidney allografts. The purpose of this study was to assess the association between vitamin D status and the occurrence of renal rejection.

METHODS

We studied a retrospective cohort of 123 children, who were transplanted at a single institution between September 2008 and April 2019. Patients did not receive vitamin D supplementation systematically. In addition, factors influencing vitamin D status were analyzed using univariate and multivariate analyses.

RESULTS

Median 25-hydroxy-vitamin D (25-OH-D) concentration was close to reference values at the time of transplantation (30 ng/mL (min-max 5-100)), but rapidly decreased within the first 3 months to 19 ng/mL (min-max 3-91) (P < .001). The overall acute rejection rate was 7%. The clinical rejection rate (5% vs 9%), subclinical rejection (12% vs 36%), and borderline changes (21% vs 28%) were not statistically different during the follow-up between the 3-month 25-OH-D < 20 ng/mL and 3-month 25-OH-D > 20 ng/mL groups. There was a correlation between the 25-OH-D levels and PTH concentration at 3 months (r = -.2491, P = .01), but no correlation between the 3-month 25-OH-D and the season of the year (F = 0.19, P = .90; F = 1.34, P = .27, respectively). Multivariate analyses revealed that age and mGFR at 3 months, were independent predictors of mGFR at 12 months.

CONCLUSION

Our data show that vitamin D deficiency can develop rapidly after transplantation; vitamin D levels at 3 months are not associated with lower mGFR or a higher rejection rate at 1 year in children as opposed to adult recipients.

Remission of proteinuria in multidrug-resistant idiopathic nephrotic syndrome following immunoglobulin immunoadsorption

AIM

Complete or partial resistance to prednisone and calcineurin inhibitors in children with idiopathic nephrotic syndrome often leads to end-stage renal disease. The aim of the study was to report the outcome of patients with multidrug-resistant nephrotic syndrome treated with an association of immunoglobulin immunoadsorption, intravenous immunoglobulins and B-cell depletion.

METHODS

At treatment initiation, patients received ten sessions of immunoglobulin immunoadsorption and intravenous immunoglobulins in two weeks followed by one rituximab in case of remission.

RESULTS

A remission of proteinuria was obtained in nine out of 14 patients at the end of the initial phase and in two additional patients after an extended period. The remission was stable in three patients and after additional IgIA and heavy immunosuppression in six. Two patients that initially responded relapsed after IgIA withdrawal and remained with an uncontrolled disease at last follow-up. Three patients did not respond to the treatment including two who were found to have a genetic podocytopathy.

CONCLUSION

Patients with multidrug-resistant idiopathic nephrotic syndrome can be successfully led into remission by IgIA prior to reaching end-stage renal disease. However, IgIA does not suppress the need for heavy additional immunosuppression to control INS in most cases.

Autoantibodies against podocytic UCHL1 are associated with idiopathic nephrotic syndrome relapses and induce proteinuria in mice

Idiopathic steroid sensitive nephrotic syndrome (INS), the most frequent childhood nephropathy, is thought to be mediated by a circulating soluble factor that reversibly affects the renal protein sieving. The efficiency of rituximab therapy recently highlighted the involvement of B cells. Here we studied the involvement of a specific immunoglobulin G (IgG) in the disease. After plasma fractionation by size exclusion chromatography, a detachment of cultured podocyte was observed with one IgG-containing fraction from 47% patients in relapse, 9% of patients in remission and 0% of controls. Podocyte protein lysates were immunoprecipitated by IgG from those plasma fractions identifying a list of 41 podocyte proteins after proteomic analysis. Five podocyte targets were selected on statistical and biological criteria. Specific antibodies were tested and only anti-Ubiquitin Carboxyl-Terminal Hydrolase L1 (UCHL1) IgG led to podocyte detachment. UCHL1 was mainly found inside the podocyte but also weakly expressed on podocyte cell surface. Incubation of either anti-UCHL1 IgG or plasma fractions with recombinant UCHL1 prevented podocyte detachment. Plasma levels of anti-UCHL1 IgG were significantly increased in relapsing INS patients compared to patients in remission and controls. Proteinuria correlated with anti-UCHL1 IgG level at various stages of the disease. Purified patient anti-UCHL1 antibodies induced proteinuria and podocyte foot effacement in mice. Altogether, these results identified UCHL1 as a target podocyte protein of autoantibodies in a set of relapsing patients and support a causative role of anti-UCHL1 autoantibodies in the development of INS.

Fluid status evaluation by inferior vena cava diameter and bioimpedance spectroscopy in pediatric chronic hemodialysis

Background

Evaluation of patient’s dry weight remains challenging in chronic hemodialysis (HD) especially in children. Inferior Vena Cava (IVC) measurement was reported useful to assess fluid overload both in adults and children.

Methods

We performed a monocentric prospective study to evaluate the relation between predialytic IVC diameter measurements and hydration status evaluated by physicians and bioimpedance spectroscopy (BIS) and between IVC measurements and persistent hypertension.

Results

Forty-eight HD sessions in 16 patients were analyzed. According to physicians, patients were overhydrated in 84.5% of dialysis sessions, 20.8% according to BIS, and 0%, 4.1% and 20.8% according to IVC inspiratory, expiratory and collapsibility index reference curves respectively. There was no correlation between relative overhydration evaluated by BIS and IVC measurements z-scores (p = 0.20). Patients whose blood pressure normalized after HD had a more dilated maximal IVC diameter before dialysis session than patients with persistent hypertension (median − 0.07SD [−0.8; 0.88] versus −1.61SD [−2.18; −0.74] (p = 0.03)) with an optimal cut-off of −0.5 SD.

Conclusions

In our study, IVC measurement is not reliable to assess fluid overload in children on HD and was not correlated with extracellular fluid volume assessed by BIS measurements. However, IVC measurements might be of interest in differentiating volume-dependant hypertension from volume-independant hypertension.

Electronic supplementary material

The online version of this article (10.1186/s12882-017-0793-1) contains supplementary material, which is available to authorized users.

Mycophenolate mofetil in steroid-dependent idiopathic nephrotic syndrome

BACKGROUND

Prospective studies have established the mycophenolate mofetil (MMF) efficiency in childhood idiopathic nephrotic syndrome (INS) but reports on the long-term outcome are lacking. Moreover, the search for factors influencing its efficiency would be useful to define its place among the other treatments.

METHODS

We performed a monocentric retrospective study including 96 children with steroid-dependent INS followed for 4.7 years (median) (IQ 3-6) after the onset of MMF treatment. The characteristics of responder patients (n = 74), as defined by a 50 % decrease of relapse rate and/or a 60 % decrease of steroid dose, and of non-responder patients (n = 22) were compared by univariate analysis and multivariate logistic regression.

RESULTS

Withdrawal of prednisone was achieved in 48/96 patients after a median duration of 18.1 months (IQ 7.8-30.0) of MMF. Only 26/48 patients did not relapse under MMF alone. After MMF was stopped in these patients, only six remained in remission without any treatment at last follow-up. Responders had a shorter time to remission at the first flare (9.5 vs. 15 days, p = 0.02), a shorter disease duration prior to the onset of MMF (22.2 vs. 94.5 months, p = 0.001), and were younger at the MMF initiation (6.7 vs. 10.1 years, p = 0.02) than non-responder patients. The age of MMF initiation was an independent factor associated with efficiency (OR = 0.80, 95 % CI [0.69, 0.93], p < 0.01).

CONCLUSIONS

MMF is more efficient in young patients treated early in the disease course. Nevertheless, MMF has no remnant effect while nearly all patients relapsed after withdrawal of the drug.

Toll-like receptor 3 expression and function in childhood idiopathic nephrotic syndrome

The efficacy of steroids and immunosuppressive treatments in idiopathic nephrotic syndrome (INS) hints at the implication of immune cells in the pathophysiology of the disease. Toll-like receptor (TLR) dysfunctions are involved in many kidney diseases of immune origin, but remain little described in INS. We investigated the expression and function of TLRs in peripheral blood mononuclear cells (PBMC) of INS children, including 28 in relapse, 23 in remission and 40 controls. No child had any sign of infection, but a higher Epstein-Barr virus viral load was measured in the PBMC of relapsing patients. TLR-3 expression was increased in B cells only during INS remission. There was a negative correlation between proteinuria and TLR-3 expression in total and the main subsets of PBMC from INS patients. The expression of TLR-8 was also increased in both CD4(+) T cells and B cells in INS remission. There was a negative correlation between proteinuria and TLR-8 expression in total PBMC, CD4(+) T cells and B cells of INS patients. Nevertheless, TLR-3 and TLR-8 expression was normalized in all PBMC subsets in an additional group of 15 INS patients in remission with B cell repletion after rituximab therapy. Paradoxically, interferon (IFN) regulatory factor 3 transactivation was increased in PBMC of all INS patients. In-vitro secretion of IFN-α and interleukin 6 were increased spontaneously in PBMC of INS remission patients, whereas PBMC from all INS patients displayed an impaired IFN-α secretion after TLR-3 stimulation. Thus, TLR-3 pathway dysfunctions may be closely involved in INS pathogenesis.