Exercise-Induced Pulmonary Hypertension in Long-Term Survivors of Congenital Diaphragmatic Hernia.

OBJECTIVE: To determine the prevalence of exercise-induced pulmonary hypertension (PH) among long-survivors of congenital diaphragmatic hernia repair. STUDY DESIGN: This is a single-center, retrospective cohort study of CDH survivors who underwent exercise stress echocardiography (ESE) at Boston Children's Hospital from January 2006 to June 2020. PH severity was assessed by echocardiogram at baseline and after exercise. Patients were categorized by right ventricular systolic pressure (RVSP) after exercise: Group 1 - no or mild PH; and Group 2 - moderate or severe PH (RVSP ≥ 60 mmHg or ≥ ½ systemic blood pressure). RESULTS: Eighty-four patients with CDH underwent 173 ESE with median age 8.1 (4.8 - 19.1) years at first ESE. Sixty-four patients were classified as Group 1, 11 as Group 2, and 9 had indeterminate RVSP with ESE. Moderate to severe PH after exercise was found in 8 (10%) patients with no or mild PH at rest. Exercise-induced PH was associated with larger CDH defect size, patch repair, use of ECMO, supplemental oxygen at discharge, and higher WHO functional class. Higher VE/VCO2 slope, lower peak oxygen saturation, and lower percent predicted FEV1, and FEV1/FVC ratio were associated with Group 2 classification. ESE changed management in 9/11 Group 2 patients. PH was confirmed in all 5 Group 2 patients undergoing cardiac catheterization after ESE. CONCLUSIONS: Among long-term CDH survivors, 10% had moderate-severe exercise-induced PH on ESE, indicating ongoing pulmonary vascular abnormalities. Further studies are needed to optimally define PH screening and treatment for patients with repaired CDH.

Gastrointestinal complications in pediatric lung transplant recipients: Incidence, risk factors, and effects on patient outcomes.

BACKGROUND: Gastrointestinal (GI) complications in lung transplant recipients can occur any time during the post-operative period, leading to prolonged morbidity and mortality. Despite the negative association between GI complications and patient outcomes, little is known about their incidence and risk factors for their development in pediatric lung transplant recipients. METHODS: We performed a retrospective chart review at one pediatric tertiary center to describe the frequency of GI complications in lung transplant recipients. We identified potential risk factors for the diagnosis of gastroparesis, gastroesophageal reflux disease (GERD) and aspiration in the post-transplant period. Lastly, we investigated the association of these complications with mortality and graft survival. RESULTS: 84.3% of lung transplant recipients experienced at least one GI complication in the post-transplant period. Gastroparesis (52.9%), GERD (41.2%), and oropharyngeal dysphagia/laryngeal penetration (33.3%) were the most common complications diagnosed. Post-operative opioid exposure was a risk factor for gastroparesis, with the odds increasing 3.0% each day a patient was prescribed opioids (p = .021). The risk of death or retransplant in individuals who experienced gastroparesis was 2.7 times higher than those not diagnosed with gastroparesis (p = .027). CONCLUSION: Exposure to opioids in the post-operative period is a risk factor for gastroparesis and a prolonged hospitalization placed patients at risk for aspiration. Gastroparesis was associated with increased patient mortality and graft failure, while aspiration and GERD had no effect on long term outcomes. Future prospective studies investigating the relationship between opioid use and the development of a gastroparesis are necessary to improve patient outcomes.

The IPTA Nashville Consensus Conference on Post-Transplant lymphoproliferative disorders after solid organ transplantation in children: III - Consensus guidelines for Epstein-Barr virus load and other biomarker monitoring.

The International Pediatric Transplant Association convened an expert consensus conference to assess current evidence and develop recommendations for various aspects of care relating to post-transplant lymphoproliferative disorders after solid organ transplantation in children. In this report from the Viral Load and Biomarker Monitoring Working Group, we reviewed the existing literature regarding the role of Epstein-Barr viral load and other biomarkers in peripheral blood for predicting the development of PTLD, for PTLD diagnosis, and for monitoring of response to treatment. Key recommendations from the group highlighted the strong recommendation for use of the term EBV DNAemia instead of "viremia" to describe EBV DNA levels in peripheral blood as well as concerns with comparison of EBV DNAemia measurement results performed at different institutions even when tests are calibrated using the WHO international standard. The working group concluded that either whole blood or plasma could be used as matrices for EBV DNA measurement; optimal specimen type may be clinical context dependent. Whole blood testing has some advantages for surveillance to inform pre-emptive interventions while plasma testing may be preferred in the setting of clinical symptoms and treatment monitoring. However, EBV DNAemia testing alone was not recommended for PTLD diagnosis. Quantitative EBV DNAemia surveillance to identify patients at risk for PTLD and to inform pre-emptive interventions in patients who are EBV seronegative pre-transplant was recommended. In contrast, with the exception of intestinal transplant recipients or those with recent primary EBV infection prior to SOT, surveillance was not recommended in pediatric SOT recipients EBV seropositive pre-transplant. Implications of viral load kinetic parameters including peak load and viral set point on pre-emptive PTLD prevention monitoring algorithms were discussed. Use of additional markers, including measurements of EBV specific cell mediated immunity was discussed but not recommended though the importance of obtaining additional data from prospective multicenter studies was highlighted as a key research priority.

The IPTA Nashville consensus conference on post-transplant lymphoproliferative disorders after solid organ transplantation in children: IV-consensus guidelines for the management of post-transplant lymphoproliferative disorders in children and adolescents.

The International Pediatric Transplant Association convened an expert consensus conference to assess current evidence and develop recommendations for various aspects of care relating to post-transplant lymphoproliferative disorders (PTLD) after pediatric solid organ transplantation. This report addresses the outcomes of deliberations by the PTLD Management Working Group. A strong recommendation was made for reduction in immunosuppression as the first step in management. Similarly, strong recommendations were made for the use of the anti-CD20 monoclonal antibody (rituximab) as was the case for chemotherapy in selected scenarios. In some scenarios, there is uncoupling of the strength of the recommendations from the available evidence in situations where such evidence is lacking but collective clinical experiences drive decision-making. Of note, there are no large, randomized phase III trials of any treatment for PTLD in the pediatric age group. Current gaps and future research priorities are highlighted.

Long-Term Functional Outcomes at 1-Year After Hospital Discharge in Critically Ill Neonates With Congenital Diaphragmatic Hernia.

OBJECTIVES: Congenital diaphragmatic hernia (CDH) is a birth defect associated with long-term morbidity. Our objective was to examine longitudinal change in Functional Status Scale (FSS) after hospital discharge in CDH survivors. DESIGN: Single-center retrospective cohort study. SETTING: Center for comprehensive CDH management at a quaternary, free-standing children's hospital. PATIENTS: Infants with Bochdalek CDH were admitted to the ICU between January 2009 and December 2019 and survived until hospital discharge. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: One hundred forty-two infants (58% male, mean birth weight 3.08 kg, 80% left-sided defects) met inclusion criteria. Relevant clinical data were extracted from the medical record to calculate FSS (primary outcome) at hospital discharge and three subsequent outpatient follow-up time points. The median (interquartile range [IQR]) FSS score at hospital discharge was 8.0 (7.0-9.0); 39 patients (27.5%) had at least moderate impairment (FSS ≥ 9). Median (IQR) FSS at 0- to 6-month ( n = 141), 6- to 12-month ( n = 141), and over 12-month ( n = 140) follow-up visits were 7.0 (7.0-8.0), 7.0 (6.0-8.0), and 6.0 (6.0-7.0), respectively. Twenty-one patients (15%) had at least moderate impairment at over 12-month follow-up; median composite FSS scores in the over 12-month time point decreased by 2.0 points from hospital discharge. Median feeding domain scores improved by 1.0 (1.0-2.0), whereas other domain scores remained without impairment. Multivariable analysis demonstrated right-sided, C- or D-size defects, extracorporeal membrane oxygenation use, cardiopulmonary resuscitation, and chromosomal anomalies were associated with impairment. CONCLUSIONS: The majority of CDH survivors at our center had mild functional status impairment (FSS ≤ 8) at discharge and 1-year follow-up; however, nearly 15% of patients had moderate impairment during this time period. The feeding domain had the highest level of functional impairment. We observed unchanged or improving functional status longitudinally over 1-year follow-up after hospital discharge. Longitudinal outcomes will guide interdisciplinary management strategies in CDH survivors.

CTOTC-08: A multicenter randomized controlled trial of rituximab induction to reduce antibody development and improve outcomes in pediatric lung transplant recipients.

We conducted a randomized, placebo-controlled, double-blind study of pediatric lung transplant recipients, hypothesizing that rituximab plus rabbit anti-thymocyte globulin induction would reduce de novo donor-specific human leukocyte antigen antibodies (DSA) development and improve outcomes. We serially obtained clinical data, blood, and respiratory samples for at least one year posttransplant. We analyzed peripheral blood lymphocytes by flow cytometry, serum for antibody development, and respiratory samples for viral infections using multiplex PCR. Of 45 subjects enrolled, 34 were transplanted and 27 randomized to rituximab (n = 15) or placebo (n = 12). No rituximab-treated subjects versus five placebo-treated subjects developed de novo DSA with mean fluorescence intensity >2000. There was no difference between treatment groups in time to the primary composite outcome endpoint (death, bronchiolitis obliterans syndrome [BOS] grade 0-p, obliterative bronchiolitis or listing for retransplant). A post-hoc analysis substituting more stringent chronic lung allograft dysfunction criteria for BOS 0-p showed no difference in outcome (p = .118). The incidence of adverse events including infection and rejection episodes was no different between treatment groups. Although the study was underpowered, we conclude that rituximab induction may have prevented early DSA development in pediatric lung transplant recipients without adverse effects and may improve outcomes (Clinical Trials: NCT02266888).

Pneumatosis intestinalis after thoracic organ transplantation in children: A case series and review of the literature.

Pneumatosis intestinalis (PI) is a rare complication after thoracic organ transplantation. There are several theories for explaining the pathophysiology of this disease. In this paper, we highlight three cases of PI in a single pediatric center, one after lung transplantation and two after heart transplantation. Although the presentations differed, all cases improved with non-surgical therapies. There are not many articles in the pediatric literature about post-transplantation PI, and there are still many questions regarding the incidence, etiology, and treatment for this disease.

Recovery of right ventricular function after bilateral lung transplantation for pediatric pulmonary hypertension.

BACKGROUND: Lung transplantation is a therapeutic option for end-stage pediatric pulmonary hypertension (PH). Right ventricular (RV) recovery post-lung transplant in children with PH has not been well-described, and questions persist about the peri-operative course and post-transplant cardiac function after lung transplantation in medically refractory PH patients with baseline RV dysfunction. METHODS: A single-center chart review identified patients with childhood PH who subsequently underwent bilateral orthotopic lung transplantation between 2000 and 2020. Twenty-six patients met criteria; three were excluded due to echocardiograms not available for digital review. RV fractional area change (FAC) and left ventricular eccentricity index (LVEI) were determined prior to transplantation, and at 1, 3, 6, and 12-month post-transplantation. RESULTS: Fourteen of 23 patients had baseline RV dysfunction. The median age at transplantation was 16.5 years and 13.9 years for those with and without baseline RV dysfunction, respectively. Of the 14 with baseline RV dysfunction, 12 (86%) were alive 1-year post-transplantation. All patients with baseline RV dysfunction had increased RV-FAC post-transplantation with normalization of RV-FAC in 70% at 3 months and 100% of patients by 12-month post-transplantation. Duration of ventilation (p = .4), intensive care unit (p = .5), or hospital stay (p = .9) was not associated with pre-transplant RV function. CONCLUSIONS: Among pediatric patients with PH and RV dysfunction, pre-transplantation RV function was not associated with short-term outcomes. All patients with baseline RV dysfunction had improvement in RV function, justifying consideration of lung transplantation among pediatric patients with end-stage PH and RV dysfunction.

Auto-inflammation and auto-immunity pathways are associated with emergence of BOS in pediatric lung transplantation.

BACKGROUND: Long-term survival after lung transplantation (LTx) is limited by chronic lung allograft dysfunction (CLAD). METHODS: We report an analysis of cytokine profiles in bronchoalveolar lavage samples collected during a prospective multicenter non-interventional trial primarily designed to determine the impact of community-acquired respiratory viral infections (CARV) in outcomes after pediatric LTx. In this analysis, we identify potential biomarkers of auto-inflammation and auto-immunity associated with survival and risk of bronchiolitis obliterans (BOS) after LTx with cytokine analysis of bronchoalveolar lavage fluid (BALF) from 61 pediatric recipients. RESULTS: Higher IL-23 (p = .048) and IL-31 (p = .035) levels were associated with the risk of BOS, and lower levels of epithelial growth factor (EGF) (p = .041) and eotaxin (EOX) (p = .017) were associated with BOS. Analysis using conditional inference trees to evaluate cytokines at each visit associated with survival identified soluble CD30 (p < .001), pro-inflammatory cytokine IL-23 (p = .02), and sTNFRI (p = .01) below cutoff levels as associated with BOS-free survival. CONCLUSIONS: Our results indicate that post-LTx survival in children may be linked to activation of alternate pathways of the immune system that affect airway remodeling in addition to activation of "classical" pathways that have been described in adult LTx recipients. These may indicate pathways to target for intervention.

The IPTA Nashville consensus conference on Post-Transplant lymphoproliferative disorders after solid organ transplantation in children: II-consensus guidelines for prevention.

The International Pediatric Transplant Association (IPTA) convened an expert consensus conference to assess current evidence and develop recommendations for various aspects of care relating to post-transplant lymphoproliferative disorder after solid organ transplantation in children. In this report from the Prevention Working Group, we reviewed the existing literature regarding immunoprophylaxis and chemoprophylaxis, and pre-emptive strategies. While the group made a strong recommendation for pre-emptive reduction of immunosuppression at the time of EBV DNAemia (low to moderate evidence), no recommendations for use could be made for any prophylactic strategy or alternate pre-emptive strategy, largely due to insufficient or conflicting evidence. Current gaps and future research priorities are highlighted.

Remote intervention engagement and outcomes in the Clinical Trials in Organ Transplantation in Children consortium multisite trial.

Remote interventions are increasingly used in transplant medicine but have rarely been rigorously evaluated. We investigated a remote intervention targeting immunosuppressant management in pediatric lung transplant recipients. Patients were recruited from a larger multisite trial if they had a Medication Level Variability Index (MLVI) ≥2.0, indicating worrisome tacrolimus level fluctuation. The manualized intervention included three weekly phone calls and regular follow-up calls. A comparison group included patients who met enrollment criteria after the subprotocol ended. Outcomes were defined before the intent-to-treat analysis. Feasibility was defined as ≥50% of participants completing the weekly calls. MLVI was compared pre- and 180 days postenrollment and between intervention and comparison groups. Of 18 eligible patients, 15 enrolled. Seven additional patients served as the comparison. Seventy-five percent of participants completed ≥3 weekly calls; average time on protocol was 257.7 days. Average intervention group MLVI was significantly lower (indicating improved blood level stability) at 180 days postenrollment (2.9 ± 1.29) compared with pre-enrollment (4.6 ± 2.10), p = .02. At 180 days, MLVI decreased by 1.6 points in the intervention group but increased by 0.6 in the comparison group (p = .054). Participants successfully engaged in a long-term remote intervention, and their medication blood levels stabilized. NCT02266888.

miR-21 antagonism reprograms macrophage metabolism and abrogates chronic allograft vasculopathy.

Despite much progress in improving graft outcome during cardiac transplantation, chronic allograft vasculopathy (CAV) remains an impediment to long-term graft survival. MicroRNAs (miRNAs) emerged as regulators of the immune response. Here, we aimed to examine the miRNA network involved in CAV. miRNA profiling of heart samples obtained from a murine model of CAV and from cardiac-transplanted patients with CAV demonstrated that miR-21 was most significantly expressed and was primarily localized to macrophages. Interestingly, macrophage depletion with clodronate did not significantly prolong allograft survival in mice, while conditional deletion of miR-21 in macrophages or the use of a specific miR-21 antagomir resulted in indefinite cardiac allograft survival and abrogated CAV. The immunophenotype, secretome, ability to phagocytose, migration, and antigen presentation of macrophages were unaffected by miR-21 targeting, while macrophage metabolism was reprogrammed, with a shift toward oxidative phosphorylation in naïve macrophages and with an inhibition of glycolysis in pro-inflammatory macrophages. The aforementioned effects resulted in an increase in M2-like macrophages, which could be reverted by the addition of L-arginine. RNA-seq analysis confirmed alterations in arginase-associated pathways associated with miR-21 antagonism. In conclusion, miR-21 is overexpressed in murine and human CAV, and its targeting delays CAV onset by reprogramming macrophages metabolism.

Pediatric lung transplant: Correlation of pretransplant condition with post-transplant outcomes.

BACKGROUND: It is generally accepted that patients who have greater functional capacity are better candidates for lung transplantation. Accurate assessment of physical condition is important in identifying appropriate candidates for transplant. The focus of this study was to determine which measures of pretransplant physical condition correlate with positive post-transplant outcomes in children undergoing lung transplant. METHODS: A retrospective chart review was done on 44 patients, ages 5 to 21 years. The pretransplant data collected included functional status, 6MWT, ambulatory status, and mechanical support. Post-transplant outcome data included time on the ventilator, days in the ICU, length of hospitalization, and 12-month survival. RESULTS: Results were analyzed using Fisher exact and Kruskal-Wallis tests. Patients with limited ambulation had more days in the ICU compared to the most ambulatory group (P = .043). Patients independent or needing some help with ADL had less time on the ventilator compared to patients needing total help. (P = .014). Patients with 6MWT result greater than 500' had fewer ICU days (P = .044) and marginally better 12-month survival (P = .057). The 12-month survival of children needing invasive ventilatory support pretransplant was not significantly worse than those who did not; however, they required significantly more time on the ventilator (P = .004), days in ICU (P = .013), and longer hospitalization. DISCUSSION: This study demonstrated that pretransplant physical condition affects post-transplant outcomes in children. Measures associated with positive post-transplant outcomes were identified and could be beneficial in determining which patients are optimal candidates for lung transplant.

Notch-1 Inhibition Promotes Immune Regulation in Transplantation Via Regulatory T Cell-Dependent Mechanisms.

BACKGROUND: Transplantation is the treatment of choice for many patients with end-stage organ disease. Despite advances in immunosuppression, long-term outcomes remain suboptimal, hampered by drug toxicity and immune-mediated injury, the leading cause of late graft loss. The development of therapies that promote regulation while suppressing effector immunity is imperative to improve graft survival and minimize conventional immunosuppression. Notch signaling is a highly conserved pathway pivotal to T-cell differentiation and function, rendering it a target of interest in efforts to manipulate T cell-mediated immunity. METHODS: We investigated the pattern of Notch-1 expression in effector and regulatory T cells (Tregs) in both murine and human recipients of a solid-organ transplant. Using a selective human anti-Notch-1 antibody (aNotch-1), we examined the effect of Notch-1 receptor inhibition in full major histocompatibility complex-mismatch murine cardiac and lung transplant models, and in a humanized skin transplant model. On the basis of our findings, we further used a genetic approach to investigate the effect of selective Notch-1 inhibition in Tregs. RESULTS: We observed an increased proportion of Tregs expressing surface and intracellular (activated) Notch-1 in comparison with conventional T cells, both in mice with transplants and in the peripheral blood of patients with transplants. In the murine cardiac transplant model, peritransplant administration of aNotch-1 (days 0, 2, 4, 6, 8, and 10) significantly prolonged allograft survival in comparison with immunoglobulin G-treated controls. Similarly, aNotch-1 treatment improved both histological and functional outcomes in the murine lung transplant model. The use of aNotch-1 resulted in a reduced proportion of both splenic and intragraft conventional T cells, while increasing the proportion of Tregs. Furthermore, Tregs isolated from aNotch-1-treated mice showed enhanced suppressive function on a per-cell basis, confirmed with selective Notch-1 deletion in Tregs (Foxp3EGFPCreNotch1fl/fl). Notch-1 blockade inhibited the mammalian target of rapamycin pathway and increased the phosphorylation of STAT5 (signal transducer and activator of transcription 5) in murine Tregs. Notch-1low Tregs isolated from human peripheral blood exhibited more potent suppressive capacity than Notch-1high Tregs. Last, the combination of aNotch-1 with costimulation blockade induced long-term tolerance in a cardiac transplant model, and this tolerance was dependent on CTLA-4 (cytotoxic T-lymphocyte-associated antigen-4) signaling. CONCLUSIONS: Our data reveal a promising, clinically relevant approach for immune modulation in transplantation by selectively targeting Notch-1.

Mitochondrial transplantation enhances murine lung viability and recovery after ischemia-reperfusion injury.

The most common cause of acute lung injury is ischemia-reperfusion injury (IRI), during which mitochondrial damage occurs. We have previously demonstrated that mitochondrial transplantation is an efficacious therapy to replace or augment mitochondria damaged by IRI, allowing for enhanced muscle viability and function in cardiac tissue. Here, we investigate the efficacy of mitochondrial transplantation in a murine lung IRI model using male C57BL/6J mice. Transient ischemia was induced by applying a microvascular clamp on the left hilum for 2 h. Upon reperfusion mice received either vehicle or vehicle-containing mitochondria either by vascular delivery (Mito V) through the pulmonary artery or by aerosol delivery (Mito Neb) via the trachea (nebulization). Sham control mice underwent thoracotomy without hilar clamping and were ventilated for 2 h before returning to the cage. After 24 h recovery, lung mechanics were assessed and lungs were collected for analysis. Our results demonstrated that at 24 h of reperfusion, dynamic compliance and inspiratory capacity were significantly increased and resistance, tissue damping, elastance, and peak inspiratory pressure (Mito V only) were significantly decreased (P < 0.05) in Mito groups as compared with their respective vehicle groups. Neutrophil infiltration, interstitial edema, and apoptosis were significantly decreased (P < 0.05) in Mito groups as compared with vehicles. No significant differences in cytokines and chemokines between groups were shown. All lung mechanics results in Mito groups except peak inspiratory pressure in Mito Neb showed no significant differences (P > 0.05) as compared with Sham. These results conclude that mitochondrial transplantation by vascular delivery or nebulization improves lung mechanics and decreases lung tissue injury.

FK506 induces lung lymphatic endothelial cell senescence and downregulates LYVE-1 expression, with associated decreased hyaluronan uptake.

BACKGROUND: Therapeutic lymphangiogenesis in an orthotopic lung transplant model has been shown to improve acute allograft rejection that is mediated at least in part through hyaluronan drainage. Lymphatic vessel endothelial hyaluronan receptor (LYVE-1) expressed on the surface of lymphatic endothelial cells plays important roles in hyaluronan uptake. The impact of current immunosuppressive therapies on lung lymphatic endothelial cells is largely unknown. We tested the hypothesis that FK506, the most commonly used immunosuppressant after lung transplantation, induces lung lymphatic endothelial cell dysfunction. METHODS: Lung lymphatic endothelial cells were cultured in vitro and treated with FK506. Telomerase activity was measured using the TRAP assay. Protein expression of LYVE-1 and senescence markers p21 and ß-galactosidase was assessed with western blotting. Matrigel tubulation assay were used to investigate the effects of FK506 on TNF-α-induced lymphangiogenesis. Dual luciferase reporter assay was used to confirm NFAT-dependent transcriptional regulation of LYVE-1. Flow cytometry was used to examine the effects of FK506 on LYVE-1 in precision-cut-lung-slices ex vivo and on hyaluronan uptake in vitro. RESULTS: In vitro, FK506 downregulated telomerase reverse transcriptase expression, resulting in decreased telomerase activity and subsequent induction of p21 expression and cell senescence. Treatment with FK506 decreased LYVE-1 mRNA and protein levels and resulted in decreased LEC HA uptake. Similar result showing reduction of LYVE-1 expression when treated with FK506 was observed ex vivo. We identified a putative NFAT binding site on the LYVE-1 promoter and cloned this region of the promoter in a luciferase-based reporter construct. We showed that this NFAT binding site regulates LYVE-1 transcription, and mutation of this binding site blunted FK506-dependent downregulation of LYVE-1 promoter-dependent transcription. Finally, FK506-treated lymphatic endothelial cells show a blunted response to TNF-α-mediated lymphangiogenesis. CONCLUSION: FK506 alters lymphatic endothelial cell molecular characteristics and causes lymphatic endothelial cell dysfunction in vitro and ex vivo. These effects of FK506 on lymphatic endothelial cell may impair the ability of the transplanted lung to drain hyaluronan macromolecules in vivo. The implications of our findings on the long-term health of lung allografts merit more investigation.

Epidemiology and persistence of rhinovirus in pediatric lung transplantation.

BACKGROUND: Infection with rhinovirus (HRV) occurs following pediatric lung transplantation. Prospective studies documenting frequencies, persistence, and progression of HRV in this at-risk population are lacking. METHODS: In the Clinical Trials in Organ Transplant in Children prospective observational study, we followed 61 lung transplant recipients for 2 years. We quantified molecular subtypes of HRV in serially collected nasopharyngeal (NP) and bronchoalveolar lavage (BAL) samples and correlated them with clinical characteristics. RESULTS: We identified 135 community-acquired respiratory infections (CARV) from 397 BAL and 480 NP samples. We detected 93 HRV events in 42 (68.8%) patients, 22 of which (23.4%) were symptomatic. HRV events were contiguous with different genotypes identified in 23 cases, but symptoms were not preferentially associated with any particular species. Nine (9.7%) HRV events persisted over multiple successive samples for a median of 36 days (range 18-408 days). Three persistent HRV were symptomatic. When we serially measured forced expiratory volume in one second (FEV1) in 23 subjects with events, we did not observe significant decreases in lung function over 12 months post-HRV. CONCLUSION: In conjunction with our previous reports, our prospectively collected data indicate that molecularly heterogeneous HRV infections occur commonly following pediatric lung transplantation, but these infections do not negatively impact clinical outcomes.

Absence of evidence that respiratory viral infections influence pediatric lung transplantation outcomes: Results of the CTOTC-03 study.

Based on reports in adult lung transplant recipients, we hypothesized that community-acquired respiratory viral infections (CARVs) would be a risk factor for poor outcome after pediatric lung transplant. We followed 61 pediatric lung transplant recipients for 2+ years or until they met a composite primary endpoint including bronchiolitis obliterans syndrome/obliterative bronchiolitis, retransplant, or death. Blood, bronchoalveolar lavage, and nasopharyngeal specimens were obtained with standard of care visits. Nasopharyngeal specimens were obtained from recipients with respiratory viral symptoms. Respiratory specimens were interrogated for respiratory viruses by using multiplex polymerase chain reaction. Donor-specific HLA antibodies, self-antigens, and ELISPOT reactivity were also evaluated. Survival was 84% (1 year) and 68% (3 years). Bronchiolitis obliterans syndrome incidence was 20% (1 year) and 38% (3 years). The primary endpoint was met in 46% of patients. CARV was detected in 156 patient visits (74% enterovirus/rhinovirus). We did not find a relationship between CARV recovery from respiratory specimens and the primary endpoint (hazard ratio 0.64 [95% confidence interval: 0.25-1.59], P = .335) or between CARV and the development of alloimmune or autoimmune humoral or cellular responses. These findings raise the possibility that the immunologic impact of CARV following pediatric lung transplant is different than that observed in adults.

RNAi-mediated reduction of hepatic Tmprss6 diminishes anemia and secondary iron overload in a splenectomized mouse model of ß-thalassemia intermedia.

Diminished ß-globin synthesis in ß-thalassemia is associated with ineffective erythropoiesis, leading to secondary iron overload caused by inappropriately low levels of hepcidin and to splenomegaly in the symptomatic thalassemias. Splenectomy is often employed in patients with ß-thalassemia to reduce hemolysis. Expression of the iron regulatory peptide hormone hepcidin is repressed by the serine protease TMPRSS6. Hepcidin induction by RNAi-mediated inhibition of TMPRSS6 expression reduces iron overload and mitigates anemia in murine models of ß-thalassemia intermedia. To interrogate the efficacy of RNAi-mediated reduction of Tmprss6 in splenectomized ß-thalassemia, splenectomized ß-thalassemic Hbbth3/+ animals were treated with a GalNAc-conjugated siRNA targeting Tmprss6 (GalNAc-Tmprss6) and their hematological and iron parameters monitored. We demonstrate that treatment with GalNAc-Tmprss6 significantly diminishes Tmprss6 expression and appropriately elevates hepcidin expression in splenectomized Hbbth3/+ animals. Similar to unsplenectomized animals, treated animals have markedly improved anemia due to diminished ineffective erythropoiesis and reduced iron loading in both serum and tissue. These results suggest that RNAi-mediated reduction of Tmprss6 may have positive outcomes even in splenectomized ß-thalassemia patients.