Single-cell sequencing of a novel model of neonatal bile duct ligation in mice identifies macrophage heterogeneity in obstructive cholestasis.

Macrophages (MΦ) play a role in neonatal etiologies of obstructive cholestasis, however, the role for precise MΦ subsets remains poorly defined. We developed a neonatal murine model of bile duct ligation (BDL) to characterize etiology-specific differences in neonatal cholestatic MΦ polarization. Neonatal BDL surgery was performed on female BALB/c mice at 10 days of life (DOL) with sham laparotomy as controls. Comparison was made to the Rhesus Rotavirus (RRV)-induced murine model of biliary atresia (BA). Evaluation of changes at day 7 after surgery (BDL and sham groups) and murine BA (DOL14) included laboratory data, histology (H&E, anti-CD45 and anti-CK19 staining), flow cytometry of MΦ subsets by MHCII and Ly6c expression, and single cell RNA-sequencing (scRNA-seq) analysis. Neonatal BDL achieved a 90% survival rate; mice had elevated bile acids, bilirubin, and alanine aminotransferase (ALT) versus controls (p < 0.05 for all). Histology demonstrated hepatocellular injury, CD45+ portal infiltrate, and CK19+ bile duct proliferation in neonatal BDL. Comparison to murine BA showed increased ALT in neonatal BDL despite no difference in histology Ishak score. Neonatal BDL had significantly lower MHCII-Ly6c+ MΦ versus murine BA, however, scRNA-seq identified greater etiology-specific MΦ heterogeneity with increased endocytosis in neonatal BDL MΦ versus cellular killing in murine BA MΦ. We generated an innovative murine model of neonatal obstructive cholestasis with low mortality. This model enabled comparison to murine BA to define etiology-specific cholestatic MΦ function. Further comparisons to human data may enable development of immune modulatory therapies to improve patient outcomes.

Balancing immunosuppression in pediatric liver transplantation: Playing the long game.

The overarching goal in the care of pediatric liver transplant recipients is to optimize allograft and patient health. Balancing immunosuppression to maintain allograft health while avoiding medication side effects is essential for long-term survival and optimal quality of life in pediatric liver transplant recipients. Utilizing precision medicine to personalize immunosuppression, which includes minimization and withdrawal, is core to this effort. The unique anatomy and physiology of the liver make it more tolerant to immune-mediated injury and a more favorable organ for immunosuppression minimization and withdrawal. However, several challenges exist. Standard biochemical values and histologic features may not reliably predict allograft health after a reduction in immunosuppression. Additionally, biochemical values alone do not reliably identify which patients can successfully develop operational tolerance, as there may be occult allograft injury despite normal liver enzymes. Finally, the durability of tolerance after successful reduction in immunosuppression remains uncertain over time. Innovative tools show promise in circumventing these challenges, but more research is needed to determine actual clinical utility. While immunosuppression-free transplant may not be a current reality for most pediatric liver transplant recipients, strategies to safely minimize immunosuppression without compromising allograft health are within reach. Each liver allograft and recipient pair requires a different degree of immune modulation, and through a structured process of minimization and withdrawal, immunosuppression can indeed be tailored in a precise, personalized way to optimize outcomes. This review focuses on the progress that has been made to individualize immunosuppression in pediatric liver transplantation to ensure optimal allograft and recipient health.

Neonates with acute liver failure have higher overall mortality but similar posttransplant outcomes as older infants.

Neonatal acute liver failure (ALF) carries a high mortality rate; however, little data exist on its peritransplant hospital course. This project aimed to identify factors associated with outcomes in neonates with ALF using large multicenter databases. Patients with International Classification of Diseases, Ninth Revision/International Classification of Diseases, Tenth Revision codes for liver failure (2004-2018) from linked Pediatric Health Information System and Scientific Registry of Transplant Recipients databases were assigned to two groups: neonates aged ≤30 days or older infants aged 31-120 days at admission. Billing data were used to assign diagnoses and assess patient comorbidities (sepsis, extracorporeal membrane oxygenation, total parenteral nutrition, intensive care unit, and cardiac/renal/respiratory failure). Statistical analysis included Kaplan-Meier survival curve analysis and univariate and multivariate analyses with the Cox proportional hazards model. We identified 1807 neonates and 890 older infants. Neonates had significantly lower survival to 90 days ( p = 0.04) and a lower rate of liver transplantation (2.0% vs. 6.4%; p < 0.001). Common risk factors associated with death or transplant were present between groups: diagnosis, respiratory failure, cardiac failure, and renal failure. Among neonates versus older infants who received a transplant, there was no significant differences in posttransplant lengths of stay (median 38 vs. 32 days; p = 0.53), posttransplant mortality (15% vs. 11%; p = 0.66), or graft loss (9.7% vs. 8.1%; p = 0.82). We present the largest multicenter study on peritransplant outcomes in neonatal ALF and show similar risk factors for death or transplant in neonates compared with older infants. Despite lower transplantation rates, neonates demonstrate similar posttransplant outcomes as older infants. Further studies are needed to better risk stratify neonates eligible for transplant and improve outcomes.

Biliary Atresia in Children: Update on Disease Mechanism, Therapies, and Patient Outcomes.

Biliary atresia is a rare disease but remains the most common indication for pediatric liver transplantation as there are no effective medical therapies to slow progression after diagnosis. Variable contribution of genetic, immune, and environmental factors contributes to disease heterogeneity among patients with biliary atresia. Developing a deeper understanding of the disease mechanism will help to develop targeted medical therapies and improve patient outcomes.

Severe Hepatitis in Pediatric Coronavirus Disease 2019.

ABSTRACT: Hepatic involvement in coronavirus disease 2019 (COVID-19) is typically characterized as mild hepatitis with preserved synthetic function in children. Severe hepatitis is a rare complication of COVID-19 infection that has not been extensively described in the pediatric population. We report a case series of four previously healthy children who presented with significant hepatitis as the primary manifestation of COVID-19 infection. Two of these patients met criteria for acute liver failure. None of the patients had respiratory symptoms. One patient was found to have complement dysfunction resulting in microangiopathic features and was treated successfully with eculizumab. This case is in line with adult post-mortem data showing that more severe cases of hepatic dysfunction secondary to COVID-19 infection may be associated with complement activation and microangiopathic features. Liver function should be evaluated in cases of severe COVID-19, and severe acute respiratory syndrome coronavirus 2 infection should be considered as a cause of acute severe hepatitis even in patients without significant respiratory or other systemic symptoms.

Responsible Inclusion of Pregnant Individuals in Eradicating HCV.

HCV infections have increased in recent years due to injection drug use and the opioid epidemic. Simultaneously, HCV cure has become a reality, with the advent of direct-acting antivirals (DAAs) and expansion of treatment programs. As a result, HCV screening recommendations now include all adults, including pregnant individuals; and many countries have endorsed widespread DAA access as a strategy to achieve HCV eradication. However, almost universally, pregnant individuals have been systematically excluded from HCV clinical research and treatment programs. This omission runs counter to public health strategies focused on elimination of HCV but is consistent with a historical pattern of exclusion of pregnant individuals from research. Our systematic review of publications on HCV treatment with DAAs in pregnancy revealed only one interventional study, which evaluated sofosbuvir/ledipasvir in 8 pregnant individuals. Given the paucity of research on this issue of great public health importance, we aimed to appraise the current landscape of HCV research/treatment and analyze the ethical considerations for responsibly including pregnant individuals. We propose that pregnancy may be an opportune time to offer HCV treatment given improved access, motivation, and other health care monitoring occurring in the antenatal period. Moreover, treatment of pregnant individuals may support the goal of eliminating perinatal HCV transmission and overcome the established challenges with transitioning care after delivery. The exclusion of pregnant individuals without justification denies them and their offspring access to potential health benefits, raising justice concerns considering growing data on DAA safety and global efforts to promote equitable and comprehensive HCV eradication. Finally, we propose a path forward for research and treatment programs during pregnancy to help advance the goal of HCV elimination.

ARPC1B Mutation Manifesting as Recurrent Hematemesis With Metaplasia.

ARPC1B is important in the maintenance and assembly of the ARP2/3 complex. Loss of this complex due to ARPC1B mutation results in impairment of actin polymerization and subsequent defects in chemotaxis, cell migration, and DNA repair. Individuals with this rare mutation present in infancy and have abnormal innate and adaptive immune responses. They develop immune-mediated inflammatory disease with associated platelet defects, eosinophilia, rashes, and bowel disease. Recurrent gastrointestinal hemorrhage has been described in known cases. Here, we report a case with endoscopic and histologic findings in a patient with this rare mutation.

HLA, Non-HLA Antibodies, and Eplet Mismatches in Pediatric Liver Transplantation: Observations From a Small, Single-Center Cohort.

OBJECTIVES: To identify the risk of developing acute rejection, allograft fibrosis, and antibody-mediated rejection, a retrospective review of pediatric patients who underwent liver transplant between July 31, 1998 and February 29, 2016 and had donor-specific antibodies measured at time of liver biopsy was undertaken. MATERIALS AND METHODS: HLAMatchmaker Software (http://www.hlamatchmaker.net) was used to define epitope mismatches between donors and recipients and to predict de novo donor-specific antibody risk. Epitope mismatches were evaluated for their immunogenicity. RESULTS: In our group of 42 recipients, 20 (48%) had donor-specific antibodies. Having an antibody against HLA-DQB1*02 was associated with acute rejection (66.6% vs 36%; P = .024). We found that DQ epitope mismatch load was greater in recipients with class II donor-specific antibodies (9.7 vs 3.6; P = .001). HLA-DQ (7.4 vs 3.6; P = .04) and HLA-DR (8.8 vs 3.8; P = .04) epitope mismatch loads were higher in recipients with DQ + DR donor-specific antibodies. A high portal fibrosis score was associated with higher mismatch load at the DQ locus (P = .005) and DQ + DR loci (P = .03). Having > 5 or > 6 epitope mismatch loads at the DQ locus identified a threshold above which development of DQ donor-specific antibodies would occur (area under the curve = 0.878). Mismatches for eplet 4Q, 45GE, 52PQ, and 52PL, thought to be immunodominant epitopes, were observed for several recipients. CONCLUSIONS: Knowledge of epitope mismatches between recipients and donors may aid transplant physicians in devising immunosuppression strategies.

ß-Hemolysin/cytolysin of Group B Streptococcus enhances host inflammation but is dispensable for establishment of urinary tract infection.

Group B Streptococcus (GBS; Streptococcus agalactiae) is a major human pathogen that disproportionately affects neonates and women in the peripartum period and is an emerging cause of infection in older adults. The primary toxin of GBS, ß-hemolysin/cytolysin (ßH/C), has a well-defined role in the pathogenesis of invasive disease, but its role in urinary tract infection (UTI) is unknown. Using both in vitro and in vivo models, we analyzed the importance of ßH/C in GBS uropathogenesis. There were no significant differences in bacterial density from the bladders or kidneys from mice infected with wild-type or isogenic ßH/C-deficient GBS, and competitive indices from co-infection experiments were near 1. Thus, ßH/C is dispensable for the establishment of GBS-UTI. However, ßH/C-sufficient GBS induced a more robust proinflammatory cytokine response in cultured bladder epithelial cells and in the urinary tracts of infected mice. Given the near ubiquity of ßH/C-expressing strains in epidemiologic studies and the importance of local inflammation in dictating outcomes and sequelae of UTI, we hypothesize that ßH/C-driven inflammatory signaling may be important in the clinical course of GBS-UTI.

Cigarette smoke increases Staphylococcus aureus biofilm formation via oxidative stress.

The strong epidemiological association between cigarette smoke (CS) exposure and respiratory tract infections is conventionally attributed to immunosuppressive and irritant effects of CS on human cells. Since pathogenic bacteria such as Staphylococcus aureus are members of the normal microbiota and reside in close proximity to human nasopharyngeal cells, we hypothesized that bioactive components of CS might affect these organisms and potentiate their virulence. Using Staphylococcus aureus as a model organism, we observed that the presence of CS increased both biofilm formation and host cell adherence. Analysis of putative molecular pathways revealed that CS exposure decreased expression of the quorum-sensing agr system, which is involved in biofilm dispersal, and increased transcription of biofilm inducers such as sarA and rbf. CS contains bioactive compounds, including free radicals and reactive oxygen species, and we observed transcriptional induction of bacterial oxidoreductases, including superoxide dismutase, following exposure. Moreover, pretreatment of CS with an antioxidant abrogated CS-mediated enhancement of biofilms. Exposure of bacteria to hydrogen peroxide alone increased biofilm formation. These observations are consistent with the hypothesis that CS induces staphylococcal biofilm formation in an oxidant-dependent manner. CS treatment induced transcription of fnbA (encoding fibronectin binding protein A), leading to increased binding of CS-treated staphylococci to immobilized fibronectin and increased adherence to human cells. These observations indicate that the bioactive effects of CS may extend to the resident microbiota of the nasopharynx, with implications for the pathogenesis of respiratory infection in CS-exposed humans.