Uncommon BK polyomaviruses detected in allogeneic hematopoietic cell transplant recipients.

The role of viral diversity in the pathogenesis of BK polyomavirus (BKPyV)-associated disease is poorly understood. Here, we report near full-length BKPyV genome sequences from two allogeneic hematopoietic cell transplant recipients infected with BKPyV genotype II, which is uncommon in the USA.

Immune urinary biomarkers predict infant cardiac surgery-associated acute kidney injury.

BACKGROUND: Acute kidney injury (AKI) occurs frequently after infant cardiac surgery and is associated with poor outcomes, including mortality and prolonged length of stay. AKI mechanisms are poorly understood, limiting therapeutic targets. Emerging data implicates dysregulated immune activation in post-cardiac surgery AKI development. We sought to identify immune-mediated AKI biomarkers after infant cardiopulmonary bypass (CPB)-assisted cardiac surgery. METHODS: A single-center prospective study of 126 infants less than 1 year old undergoing CPB-assisted surgery enrolled between 10/2017 and 6/2019. Urine samples were collected before CPB and at 6, 24, 48, and 72 h after surgery. Immune-mediated biomarkers were measured using commercial ELISA and Luminex™ multiplex kits. Based on subject age, neonatal KDIGO (< 1 month) or KDIGO criteria defined AKI. The Kruskal-Wallis rank test determined the relationship between urinary biomarker measurements and AKI. RESULTS: A total of 35 infants (27%) developed AKI. AKI subjects were younger, underwent more complex surgery, and had longer CPB time. Subjects with AKI vs. those without AKI had higher median urinary chemokine 10 (C-X-C motif) ligand levels at 24, 48, and 72 h, respectively: 14.3 pg/ml vs. 5.3 pg/ml, 3.4 pg/ml vs. 0.8 pg/ml, and 1.15 pg/ml vs. 0.22 pg/ml (p < 0.05) post-CPB. At 6 h post-CPB, median vascular cell adhesion protein 1 (VCAM) levels (pg/mL) were higher among AKI subjects (491 pg/ml vs. 0 pg/ml, p = 0.04). CONCLUSIONS: Urinary CXCL10 and VCAM are promising pro-inflammatory biomarkers for early AKI detection and may indicate eventual AKI therapeutic targets. A higher resolution version of the Graphical abstract is available as Supplementary information.

Diuretic Tolerance to Repeated-Dose Furosemide in Infants Born Very Preterm with Bronchopulmonary Dysplasia.

OBJECTIVES: To assess the presence and timing of furosemide diuretic tolerance in infants with bronchopulmonary dysplasia (BPD), and to determine if tolerance is modified by thiazide co-administration. STUDY DESIGN: We performed a retrospective cohort study among infants born very preterm with BPD exposed to repeated-dose furosemide for 72 hours, measuring net fluid balance (total intake minus total output) as a surrogate of diuresis in the 3 days before and after exposure. The primary comparison was the difference in fluid balance between the first and third 24 hours of furosemide exposure. We fit a general linear model for within-subject repeated measures of fluid balance over time, with thiazide co-administration as an interaction variable. Secondary analyses included an evaluation of weight trajectories over time. RESULTS: In 83 infants, median fluid balance ranged between + 43.6 and + 52.7 ml/kg/d in the 3 days prior to furosemide exposure. Fluid balance decreased to a median of + 29.1 ml/kg/d in the first 24 hours after furosemide, but then increased to +47.5 ml/kg/d by the third 24-hour interval, consistent with tolerance (P < .001). Thiazides did not modify the change in fluid balance during furosemide exposure for any time-period. Weight decreased significantly in the first 24 hours after furosemide and increased thereafter (P < .001). CONCLUSIONS: The net fluid balance response to furosemide decreases rapidly during repeated-dose exposures in infants with BPD, consistent with diuretic tolerance. Clinicians should consider this finding in the context of an infant's therapeutic goals. Further research efforts to identify safe and effective furosemide dosage strategies are needed.

A prospective multi-institutional study of eculizumab to treat high-risk stem cell transplantation-associated TMA.

ABSTRACT: High-risk, complement mediated, untreated transplant-associated thrombotic microangiopathy (hrTMA) has dismal outcomes due to multi-organ dysfunction syndrome (MODS). The complement C5 blocker eculizumab shows promising results in hrTMA, but has not been prospectively studied in hematopoietic stem cell transplant (HCT) recipients. We performed the first multi-institutional prospective study in children and young adults to evaluate eculizumab as an early targeted intervention for hrTMA/MODS. We hypothesized that eculizumab would more than double survival in HCT recipients with hrTMA, compared to our prior study of prospectively screened, untreated hrTMAs serving as historical controls. HrTMA features (elevated terminal complement (sC5b-9) and proteinuria measured by random urine protein/creatinine ratio (≥1mg/mg)) were required for inclusion. The primary endpoint was survival at 6 six-months from hrTMA diagnosis. Secondary endpoints were cumulative incidence of MODS 6 months after hrTMA diagnosis and 1-year posttransplant survival. Eculizumab dosing included intensive loading, induction, and maintenance phases for up to 24 weeks of therapy. All 21 evaluated study subjects had MODS. Primary and secondary study endpoints were met by demonstrating survival of 71% (P < .0001) 6 months after hrTMA diagnosis and 62% 1 year after transplant. Of fifteen survivors, 11 (73%) fully recovered organ function and are well. Our study demonstrates significant improvement in survival and recovery of organ function in hrTMA using an intensified eculizumab dosing and real time biomarker monitoring. This study serves as a benchmark for planning future studies that should focus on preventative measures or targeted therapy to be initiated prior to organ injury. This trial was registered at www.clinicaltrials.gov as #NCT03518203.

BK Polyomavirus Diversity After Hematopoietic Stem Cell Transplantation.

BK polyomavirus (BKPyV) infection is common after hematopoietic stem cell transplantation (HSCT) and is associated with the development of hemorrhagic cystitis (HC). The role that BKPyV plays in the pathogenesis of HC is not well characterized. We investigated the impact of BKPyV diversity on the development of HC using a previously established cohort of pediatric HSCT patients. There were 147 urine samples with quantifiable BKPyV at month 1 after HSCT; 137 (93.2%) were amplified using our in-house polymerase chain reaction approach and sent for next-generation sequencing. Subtype Ia was most frequent (61.3%), followed by subtype Ib1 (31.4%). The median viral load of subtype Ia samples was higher than for subtype Ib1 at month 1. Across the protein coding regions, APOBEC-induced mutations and signature patterns associated with HC were identified. This is the largest sequencing study of a single cohort of HSCT patients, providing a vast resource of sequence data for future analyses.

Long-Term Kidney and Cardiovascular Complications in Pediatric Cancer Survivors.

OBJECTIVE: The objective of this study was to describe the burden of adverse kidney and hypertension outcomes in patients evaluated by pediatric nephrology in a multidisciplinary survivorship clinic. STUDY DESIGN: Retrospective chart review of all patients followed up by nephrology in our multidisciplinary survivorship clinic from August 2013 to June 2021. Data included clinic blood pressure, longitudinal ambulatory blood pressure monitoring (ABPM), echocardiography, serum creatinine, and first-morning urine protein/creatinine ratios. For patients with multiple ABPMs, results of initial and most recent ABPMs were compared. RESULTS: Of 422 patients followed in the multidisciplinary cancer survivorship clinic, 130 were seen by nephrology. The median time after therapy completion to first nephrology visit was 8 years. The most common diagnoses were leukemia/myelodysplastic syndrome (27%), neuroblastoma (24%), and Wilms tumor (15%). At the last follow-up, 68% had impaired kidney function, 38% had a clinical diagnosis of hypertension, and 12% had proteinuria. There were 91 ABPMs performed in 55 (42%) patients. Patients with multiple ABPMs (n = 21) had statistically significant reductions in overall median blood pressure loads: systolic initial load 37% vs most recent 10% (P = .005) and diastolic load 36% vs 14% (P = .017). Patients with impaired kidney function were more likely to have received ifosfamide. Patients with hypertension were more likely to have received total body irradiation or allogeneic stem cell transplant. CONCLUSIONS: History of leukemia/myelodysplastic syndrome, neuroblastoma, and Wilms tumor was frequent among survivors seen by nephrology. There was significant improvement in cardiovascular measures with increased recognition of hypertension and subsequent treatment.

BK Polyomavirus Subtypes II and IV in Hematopoietic Cell Transplant Recipients.

Symptomatic BK polyomavirus (BKPyV) infections are common and relevant in immunocompromised patients. Here, we present full-length BKPyV genomes from samples from patients who received hematopoietic cell transplants in the United States. These individuals had non-subtype I BKPyV, as determined by amplification, next-generation sequencing, and phylogenetic analysis.

Optimized amplification of BK polyomavirus in urine.

BK polyomavirus (BKPyV) is a ubiquitous pathogen that typically results in asymptomatic infection. However, in immunocompromised individuals, BKPyV viral shedding in the urine can reach 109 copies per mL. These high viral levels within urine provide ideal samples for next-generation sequencing to accurately determine BKPyV genotype and identify mutations associated with pathogenesis. Sequencing data obtained can be further analyzed to better understand and characterize the genetic diversity present in BKPyV. Here, methods are described for the successful extraction of viral DNA from urine and the subsequent amplification methods to prepare a sample for next-generation sequencing.

Late effects in survivors of high-risk neuroblastoma following stem cell transplant with and without total body irradiation.

BACKGROUND: Neuroblastoma is the most common extracranial solid tumor in children. Those with high-risk disease are treated with multimodal therapy, including high-dose chemotherapy, stem cell transplant, radiation, and immunotherapy that have led to multiple long-term complications in survivors. In the late 1990s, consolidation therapy involved myeloablative conditioning including total body irradiation (TBI) with autologous stem cell rescue. Recognizing the significant long-term toxicities of exposure to TBI, more contemporary treatment protocols have removed this from conditioning regimens. This study examines an expanded cohort of 48 high-risk neuroblastoma patients to identify differences in the late effect profiles for those treated with TBI and those treated without TBI. PROCEDURE: Data on the study cohort were collected from clinic charts, provider documentation in the electronic medical record of visits to survivorship clinic, including all subspecialists, and ancillary reports of laboratory and diagnostic tests done as part of risk-based screening at each visit. RESULTS: All 48 survivors of BMT for high-risk neuroblastoma had numerous late effects of therapy, with 73% having between five and 10 late effects. TBI impacted some late effects significantly, including growth hormone deficiency (GHD), bone outcomes, and cataracts. CONCLUSION: Although high-risk neuroblastoma survivors treated with TBI have significant late effects, those treated without TBI also continue to have significant morbidity related to high-dose chemotherapy and local radiation. A multidisciplinary care team assists in providing comprehensive care to those survivors who are at highest risk for significant late effects.

BK Polyomavirus Genotypes in Two Patients after Hematopoietic Cell Transplant.

BK polyomavirus (BKPyV) infection can lead to nephropathy and hemorrhagic cystitis (HC). We evaluated BKPyV genotypes in two individuals after hematopoietic cell transplant (HCT). The first case developed HC and was infected with genotype Ib-2, while the second did not develop HC and was infected with genotype Ia.

BK polyomavirus diversity-Why viral variation matters.

BK polyomavirus (BKPyV or BKV) is a non-enveloped, circular double-stranded DNA virus that may exceed 80% seroprevalence in adults. BKV infection typically occurs during childhood, and the majority of adults are latently infected. While BKV infection is rarely associated with clinical disease in most individuals, in immunosuppressed individuals, reactivation may cause kidney (BK-associated nephropathy) or bladder (hemorrhagic cystitis and ureteral stenosis) injury. No antiviral therapies have been approved for the treatment of BKV infection. Reducing immunosuppression is the most effective therapy, although this is not feasible in many patients. Thus, a robust understanding of viral pathogenesis and viral diversity remains important for the development of future therapeutic strategies. Studies of BKV diversity are quite sparse compared to other common viral infections; thus, much of our understanding of BVK variability and evolution relies heavily analogous studies of other viruses such as HIV or viral hepatitis. We provide a comprehensive review of BKV diversity at the population and individual level with careful consideration of how viral variability may impact viral replication, pathogenesis, tropism, and protein function. We also discuss a number of outstanding questions related to BK virus diversity that should be explored rigorously in future studies.

Interferon-complement loop in transplant-associated thrombotic microangiopathy.

Transplant-associated thrombotic microangiopathy (TA-TMA) is an important cause of morbidity and mortality after hematopoietic stem cell transplantation (HSCT). The complement inhibitor eculizumab improves TA-TMA, but not all patients respond to therapy, prompting a search for additional targetable pathways of endothelial injury. TA-TMA is relatively common after HSCT and can serve as a model to study mechanisms of tissue injury in other thrombotic microangiopathies. In this work, we performed transcriptome analyses of peripheral blood mononuclear cells collected before HSCT, at onset of TA-TMA, and after resolution of TA-TMA in children with and without TA-TMA after HSCT. We observed significant upregulation of the classical, alternative, and lectin complement pathways during active TA-TMA. Essentially all upregulated genes and pathways returned to baseline expression levels at resolution of TA-TMA after eculizumab therapy, supporting the clinical practice of discontinuing complement blockade after resolution of TA-TMA. Further analysis of the global transcriptional regulatory network showed a notable interferon signature associated with TA-TMA with increased STAT1 and STAT2 signaling that resolved after complement blockade. In summary, we observed activation of multiple complement pathways in TA-TMA, in contrast to atypical hemolytic uremic syndrome (aHUS), where complement activation occurs largely via the alternative pathway. Our data also suggest a key relationship between increased interferon signaling, complement activation, and TA-TMA. We propose a model of an "interferon-complement loop" that can perpetuate endothelial injury and thrombotic microangiopathy. These findings open opportunities to study novel complement blockers and combined anti-complement and anti-interferon therapies in patients with TA-TMA and other microangiopathies like aHUS and lupus-associated TMAs.

Acute Kidney Injury in Children after Hematopoietic Cell Transplantation Is Associated with Elevated Urine CXCL10 and CXCL9.

Acute kidney injury (AKI) is nearly universally associated with worse outcomes, especially among children after hematopoietic stem cell transplant (HCT). Our objective was to examine urinary immune biomarkers of AKI after HCT to provide insights into novel mechanisms of kidney injury in this population. Studying patients undergoing allogeneic HCT provides a unique opportunity to examine immune markers of AKI because the risk of AKI is high and the immune system newly develops after transplant. Children (>2 years old) and young adults undergoing their first allogeneic HCT and enrolled in a prospective, observational cohort study at 2 large children's hospitals had urine collected pre-HCT and monthly for the first 4 months after HCT. Urine samples at each monthly time point were assayed for 8 immune-related biomarkers. AKI was defined as a 1.5-fold increase in the monthly serum creatinine value, which was recorded ±1 day from when the research urine sample was obtained, as compared with the pre-HCT baseline. Generalized estimating equation regression analysis evaluated the association between the monthly repeated measures (urinary biomarkers and AKI). A total of 176 patients were included from 2 pediatric centers. Thirty-six patients from 1 center were analyzed as a discovery cohort and the remaining 140 patients from the second center were analyzed as a validation cohort. AKI rates were 18% to 35% depending on the monthly time point after HCT. Urine CXCL10 and CXCL9 concentrations were significantly higher among children who developed AKI compared with children who did not (P < .01) in both cohorts. In order to gain a better understanding of the cellular source for these biomarkers in the urine, we also analyzed in vitro expression of CXCL10 and CXCL9 in kidney cell lines after stimulation with interferon-γ and interferon-α. HEK293-epithelial kidney cells demonstrated interferon-induced expression of CXCL10 and CXCL9, suggesting a potential mechanism driving the key finding. CXCL10 and CXCL9 are associated with AKI after HCT and are therefore promising biomarkers to guide improved diagnostic and treatment strategies for AKI in this high-risk population.

Complement blockade for TA-TMA: lessons learned from a large pediatric cohort treated with eculizumab.

Overactivated complement is a high-risk feature in hematopoietic stem cell transplant (HSCT) recipients with transplant-associated thrombotic microangiopathy (TA-TMA), and untreated patients have dismal outcomes. We present our experience with 64 pediatric HSCT recipients who had high-risk TA-TMA (hrTA-TMA) and multiorgan injury treated with the complement blocker eculizumab. We demonstrate significant improvement to 66% in 1-year post-HSCT survival in treated patients from our previously reported untreated cohort with same hrTA-TMA features that had 1-year post-HSCT survival of 16.7%. Responding patients benefited from a brief but intensive course of eculizumab using pharmacokinetic/pharmacodynamic-guided dosing, requiring a median of 11 doses of eculizumab (interquartile range [IQR] 7-20). Treatment was discontinued because TA-TMA resolved at a median of 66 days (IQR 41-110). Subjects with higher complement activation measured by elevated blood sC5b-9 at the start of treatment were less likely to respond (odds ratio, 0.15; P = .0014) and required more doses of eculizumab (r = 0.43; P = .0004). Patients with intestinal bleeding had the fastest eculizumab clearance, required the highest number of eculizumab doses (20 vs 9; P = .0015), and had lower 1-year survival (44% vs 78%; P = .01). Over 70% of survivors had proteinuria on long-term follow-up. The best glomerular filtration rate (GFR) recovery in survivors was a median 20% lower (IQR, 7.3%-40.3%) than their pre-HSCT GFR. In summary, complement blockade with eculizumab is an effective therapeutic strategy for hrTA-TMA, but some patients with severe disease lacked a complete response, prompting us to propose early intervention and search for additional targetable endothelial injury pathways.

The Natural History of BK Polyomavirus and the Host Immune Response After Stem Cell Transplantation.

BACKGROUND: BK polyomavirus (BKPyV) is associated with symptomatic hemorrhagic cystitis after hematopoietic cell transplantation (HCT). Little is known about the host immune response, effectiveness of antiviral treatment, or impact of asymptomatic replication on long-term kidney function. METHODS: In children and young adults undergoing allogeneic HCT, we quantified BKPyV viruria and viremia (pre-HCT and at Months 1-4, 8, 12, and 24 post-HCT) and tested associations of peak viremia ≥10 000 or viruria ≥109 copies/mL with estimated kidney function (glomerular filtration rate, eGFR) and overall survival at 2 years posttransplant. We examined the factors associated with viral clearance by Month 4, including BKPyV-specific T cells by enzyme-linked immune absorbent spot at Month 3 and cidofovir use. RESULTS: We prospectively enrolled 193 participants (median age 10 years) and found that 18% had viremia ≥10 000 copies/mL and 45% had viruria ≥109 copies/mL in the first 3 months post-HCT. Among the 147 participants without cystitis (asymptomatic), 58 (40%) had any viremia. In the entire cohort and asymptomatic subset, having viremia ≥10 000 copies/mL was associated with a lower creatinine/cystatin C eGFR at 2 years post-HCT. Viremia ≥10 000 copies/mL was associated with a higher risk of death (adjusted hazard ratio, 2.2; 95% confidence interval, 1.1-4.2). Clearing viremia was associated with detectable BKPyV-specific T cells and having viremia <10 000 copies/mL, but not cidofovir exposure. CONCLUSIONS: Screening for BKPyV viremia after HCT identifies asymptomatic patients at risk for kidney disease and reduced survival. These data suggest potential changes to clinical practice, including prospective monitoring for BKPyV viremia to test virus-specific T cells to prevent or treat BKPyV replication.

Mitochondrial single-stranded DNA binding protein novel de novo SSBP1 mutation in a child with single large-scale mtDNA deletion (SLSMD) clinically manifesting as Pearson, Kearns-Sayre, and Leigh syndromes.

Mitochondrial DNA (mtDNA) genome integrity is essential for proper mitochondrial respiratory chain function to generate cellular energy. Nuclear genes encode several proteins that function at the mtDNA replication fork, including mitochondrial single-stranded DNA-binding protein (SSBP1), which is a tetrameric protein that binds and protects single-stranded mtDNA (ssDNA). Recently, two studies have reported pathogenic variants in SSBP1 associated with hearing loss, optic atrophy, and retinal degeneration. Here, we report a 14-year-old Chinese boy with severe and progressive mitochondrial disease manifestations across the full Pearson, Kearns-Sayre, and Leigh syndromes spectrum, including infantile anemia and bone marrow failure, growth failure, ptosis, ophthalmoplegia, ataxia, severe retinal dystrophy of the rod-cone type, sensorineural hearing loss, chronic kidney disease, multiple endocrine deficiencies, and metabolic strokes. mtDNA genome sequencing identified a single large-scale 5 kilobase mtDNA deletion (m.8629_14068del5440), present at 68% and 16% heteroplasmy in the proband's fibroblast cell line and blood, respectively, suggestive of a mtDNA maintenance defect. On trio whole exome blood sequencing, the proband was found to harbor a novel de novo heterozygous mutation c.79G>A (p.E27K) in SSBP1. Size exclusion chromatography of p.E27K SSBP1 revealed it remains a stable tetramer. However, differential scanning fluorimetry demonstrated p.E27K SSBP1 relative to wild type had modestly decreased thermostability. Functional assays also revealed p.E27K SSBP1 had altered DNA binding. Molecular modeling of SSBP1 tetramers with varying combinations of mutant subunits predicted general changes in surface accessible charges, strength of inter-subunit interactions, and protein dynamics. Overall, the observed changes in protein dynamics and DNA binding behavior suggest that p.E27K SSBP1 can interfere with DNA replication and precipitate the introduction of large-scale mtDNA deletions. Thus, a single large-scale mtDNA deletion (SLSMD) with manifestations across the clinical spectrum of Pearson, Kearns-Sayre, and Leigh syndromes may result from a nuclear gene disorder disrupting mitochondrial DNA replication.

Native kidney BK virus nephropathy, a systematic review.

BACKGROUND: There is a growing base of literature describing BK nephropathy (BKVN) in patients outside of the setting of kidney transplant. Previous systematic reviews of the literature have been limited by methodology or by the scope of patients included. STUDY DESIGN AND METHODS: Systematic Review (Prospero # CRD42018088524). SETTING & POPULATION: Patients without kidney transplant who had biopsy-proven BKVN. SELECTION CRITERIA FOR STUDIES: Full-text articles that describe native BKVN patient cases. ANALYTICAL APPROACH: Descriptive synthesis. RESULTS: The search identified 630 unique articles of which 51 were included in the final review. Sixty-five cases (including two new cases presented in this review) were identified, all but one occurred in the setting of known immunosuppression. LIMITATIONS: The primary limitation was the exclusion of studies that did not fulfill the stringent review criteria. We excluded reports with only a clinical diagnosis of BKVN, such as those with viruria and/or viremia without biopsy. CONCLUSIONS: As of May 2018, there are 65 reported cases of BKVN in native kidneys. This represents the most comprehensive description of biopsy-proven BKVN in native kidneys to date. Evaluation for BK nephropathy should be considered in immunocompromised patients who exhibit unexplained renal failure.