Characterization of initial CLABSI culture results to support antimicrobial de-escalation in pediatric GI inpatients.

OBJECTIVES: Central Line-associated Bloodstream Infections (CLABSIs) pose a serious mortality and morbidity risk. An institutional protocol was developed for the evaluation and empirical antibiotic treatment of possible CLABSIs. The potential impact of de-escalating antimicrobial therapy based on initial Gram stain and molecular identification was assessed. METHODS: All positive blood cultures from patients admitted to the gastroenterology service at a large pediatric medical center were collected from 1/1/14 to 12/31/20. Cultures that were negative, repeated, or causative organisms that were unable to be identified with susceptibility data were excluded. Timepoints and organism(s) from each culture were recorded. Polymicrobial cultures were classified as containing only gram-positive organisms (polymicrobial GP), only gram-negative organisms (polymicrobial GN), or mixed spectrum. RESULTS: During the 6-year period, 361 positive blood cultures were included in the study. Single isolates were identified in 79.5% (287/361) of cultures. Polymicrobial cultures from confirmed central line source accounted for 15.0% (54/361), with 6.4% (23/361) Polymicrobial GP, 4.4% (16/361) Polymicrobial GN, and 4.2% (15/361) being mixed-spectrum cultures. Both organism types were detected on initial gram-stain in 40% (6/15) of the mixed-spectrum cultures, another 26.7% (4/15) had the opposite-spectrum organism identified within an average of <3 h and the remaining 33.3% (5/15) had the opposite-spectrum organism identified by culture growth. CONCLUSIONS: Polymicrobial mixed-spectrum cultures accounted for <5% of positive blood cultures and most isolates were identified within 3 h of first positivity. This may allow for further investigation of early de-escalation of therapy for this population and limit antimicrobial exposure.

Farm animal exposure, respiratory illnesses, and nasal cell gene expression.

BACKGROUND: Farm exposures in early life reduce the risks for childhood allergic diseases and asthma. There is less information about how farm exposures relate to respiratory illnesses and mucosal immune development. OBJECTIVE: We hypothesized that children raised in farm environments have a lower incidence of respiratory illnesses over the first 2 years of life than nonfarm children. We also analyzed whether farm exposures or respiratory illnesses were related to patterns of nasal cell gene expression. METHODS: The Wisconsin Infant Study Cohort included farm (n = 156) and nonfarm (n = 155) families with children followed to age 2 years. Parents reported prenatal farm and other environmental exposures. Illness frequency and severity were assessed using illness diaries and periodic surveys. Nasopharyngeal cell gene expression in a subset of 64 children at age 2 years was compared to farm exposure and respiratory illness history. RESULTS: Farm versus nonfarm children had nominally lower rates of respiratory illnesses (rate ratio 0.82 [95% CI, 0.69, 0.97]) with a stepwise reduction in illness rates in children exposed to 0, 1, or ≥2 animal species, but these trends were nonsignificant in a multivariable model. Farm exposures and preceding respiratory illnesses were positively related to nasal cell gene signatures for mononuclear cells and innate and antimicrobial responses. CONCLUSIONS: Maternal and infant exposure to farms and farm animals was associated with nonsignificant trends for reduced respiratory illnesses. Nasal cell gene expression in a subset of children suggests that farm exposures and respiratory illnesses in early life are associated with distinct patterns of mucosal immune expression.

A randomized phase 2 trial of oral vitamin A for graft-versus-host disease in children and young adults.

ABSTRACT: Vitamin A plays a key role in the maintenance of gastrointestinal homeostasis and promotes a tolerogenic phenotype in tissue resident macrophages. We conducted a prospective randomized double-blinded placebo-controlled clinical trial in which 80 recipients of hematopoietic stem cell transplantation (HSCT) were randomized 1:1 to receive pretransplant high-dose vitamin A or placebo. A single oral dose of vitamin A of 4000 IU/kg, maximum 250 000 IU was given before conditioning. The primary end point was incidence of acute graft-versus-host disease (GVHD) at day +100. In an intent-to-treat analysis, incidence of acute GVHD was 12.5% in the vitamin A arm and 20% in the placebo arm (P = .5). Incidence of acute gastrointestinal (GI) GVHD was 2.5% in the vitamin A arm (P = .09) and 12.5% in the placebo arm at day +180. Incidence of chronic GVHD was 5% in the vitamin A arm and 15% in the placebo arm (P = .02) at 1 year. In an "as treated" analysis, cumulative incidence of acute GI GVHD at day +180 was 0% and 12.5% in recipients of vitamin A and placebo, respectively (P = .02), and cumulative incidence of chronic GVHD was 2.7% and 15% in recipients of vitamin A and placebo, respectively (P = .01). The only possibly attributable toxicity was asymptomatic grade 3 hyperbilirubinemia in 1 recipient of vitamin A at day +30, which self-resolved. Absolute CCR9+ CD8+ effector memory T cells, reflecting gut T-cell trafficking, were lower in the vitamin A arm at day +30 after HSCT (P = .01). Levels of serum amyloid A-1, a vitamin A transport protein with proinflammatory effects, were lower in the vitamin A arm. The vitamin A arm had lower interleukin-6 (IL-6), IL-8, and suppressor of tumorigenicity 2 levels and likely a more favorable gut microbiome and short chain fatty acids. Pre-HSCT oral vitamin A is inexpensive, has low toxicity, and reduces GVHD. This trial was registered at www.ClinicalTrials.gov as NCT03202849.

Acute pancreatitis is associated with gut dysbiosis in children.

BACKGROUND: Pediatric acute pancreatitis (AP) is associated with significant morbidity. Therefore, improved understanding of children who will develop severe AP is critical. Adult studies have reported AP associated gut dysbiosis, but pediatric studies are lacking. AIMS: Assess stool microbial taxonomic and functional profiles of children with first attack of AP compared to those of healthy controls (HC), and between mild and severe AP METHODS: Children under 21 years hospitalized at a tertiary center (n = 30) with first AP attack were recruited including HC (n = 34) from same region. Shotgun metagenomic sequencing was performed on extracted DNA. RESULTS: Demographics were similar between AP and HC. Alpha diversity (-0.68 ± 0.13, p-value < 0.001), and beta-diversity (R2=0.13, p-value < 0.001) differed, in children with AP compared to HC. Species including R.gnavus, V.parvula, E.faecalis, C.innocuum were enriched in AP. MetaCyc pathways involved in amino acid metabolism and fatty acid beta-oxidation were enriched in AP. Beta-diversity (R2=0.06, p-value = 0.02) differed for severe AP compared to mild AP with enrichment in E.faecalis and C.citroniae. CONCLUSIONS: Gut dysbiosis occurs in pediatric AP and is associated with AP severity. A multicenter study confirming these findings could pave way for interventional trials manipulating the gut microbiome to mitigate AP severity.

Thermoneutral Housing Enables Studies of Vertical Transmission of Obesogenic Diet-Driven Metabolic Diseases.

Vertical transmission of obesity is a critical contributor to the unabated obesity pandemic and the associated surge in metabolic diseases. Existing experimental models insufficiently recapitulate "human-like" obesity phenotypes, limiting the discovery of how severe obesity in pregnancy instructs vertical transmission of obesity. Here, via utility of thermoneutral housing and obesogenic diet feeding coupled to syngeneic mating of WT obese female and lean male mice on a C57BL/6 background, we present a tractable, more "human-like" approach to specifically investigate how maternal obesity contributes to offspring health. Using this model, we found that maternal obesity decreased neonatal survival, increased offspring adiposity, and accelerated offspring predisposition to obesity and metabolic disease. We also show that severe maternal obesity was sufficient to skew offspring microbiome and create a proinflammatory gestational environment that correlated with inflammatory changes in the offspring in utero and adulthood. Analysis of a human birth cohort study of mothers with and without obesity and their infants was consistent with mouse study findings of maternal inflammation and offspring weight gain propensity. Together, our results show that dietary induction of obesity in female mice coupled to thermoneutral housing can be used for future mechanistic interrogations of obesity and metabolic disease in pregnancy and vertical transmission of pathogenic traits.

MGS2AMR: a gene-centric mining of metagenomic sequencing data for pathogens and their antimicrobial resistance profile.

BACKGROUND: Identification of pathogenic bacteria from clinical specimens and evaluating their antimicrobial resistance (AMR) are laborious tasks that involve in vitro cultivation, isolation, and susceptibility testing. Recently, a number of methods have been developed that use machine learning algorithms applied to the whole-genome sequencing data of isolates to approach this problem. However, making AMR assessments from more easily available metagenomic sequencing data remains a big challenge. RESULTS: We present the Metagenomic Sequencing to Antimicrobial Resistance (MGS2AMR) pipeline, which detects antibiotic resistance genes (ARG) and their possible organism of origin within a sequenced metagenomics sample. This in silico method allows for the evaluation of bacterial AMR directly from clinical specimens, such as stool samples. We have developed two new algorithms to optimize and annotate the genomic assembly paths within the raw Graphical Fragment Assembly (GFA): the GFA Linear Optimal Path through seed segments (GLOPS) algorithm and the Adapted Dijkstra Algorithm for GFA (ADAG). These novel algorithms improve the sensitivity of ARG detection and aid in species annotation. Tests based on 1200 microbiome samples show a high ARG recall rate and correct assignment of the ARG origin. The MGS2AMR output can further be used in many downstream applications, such as evaluating AMR to specific antibiotics in samples from emerging intestinal infections. We demonstrate that the MGS2AMR-derived data is as informative for the entailing prediction models as the whole-genome sequencing (WGS) data. The performance of these models is on par with our previously published method (WGS2AMR), which is based on the sequencing data of bacterial isolates. CONCLUSIONS: MGS2AMR can provide researchers with valuable insights into the AMR content of microbiome environments and may potentially improve patient care by providing faster quantification of resistance against specific antibiotics, thereby reducing the use of broad-spectrum antibiotics. The presented pipeline also has potential applications in other metagenome analyses focused on the defined sets of genes. Video Abstract.

Obesity Alters cytokine signaling and gut microbiome in septic mice.

Sepsis is a leading cause of mortality. Plasma cytokine levels may identify those at increased risk of mortality from sepsis. Our aim was to understand how obesity alters cytokine levels during early sepsis and its correlation with survival. Six-week-old C57BL/6 male mice were randomized to control (non-obese) or high fat diet (obese) for 5-7 weeks. Sepsis was induced by cecal ligation and perforation (CLP). Cytokine levels were measured from cheek bleeds 8 h after CLP, and mice were monitored for survival. Other cohorts were sacrificed 1 h after CLP for plasma and tissue. Septic obese mice had higher survival. At 8 h after sepsis, obese mice had higher adiponectin, leptin, and resistin but lower TNFα and IL-6 compared to non-obese mice. When stratified by 24-h survival, adipokines were not significantly different in obese and non-obese mice. TNFα and IL-6 were higher in non-obese, compared to obese, mice that died within 24 h of sepsis. Diet and to sepsis significantly impacted the cecal microbiome. IL-6 is a prognostic biomarker during early sepsis in non-obese and obese mice. A plausible mechanism for the survival difference in non-obese and obese mice may be the difference in gut microbiome and its evolution during sepsis.

Kruppel-like factor 2+ CD4 T cells avert microbiota-induced intestinal inflammation.

Intestinal colonization by antigenically foreign microbes necessitates expanded peripheral immune tolerance. Here we show commensal microbiota prime expansion of CD4 T cells unified by the Kruppel-like factor 2 (KLF2) transcriptional regulator and an essential role for KLF2+ CD4 cells in averting microbiota-driven intestinal inflammation. CD4 cells with commensal specificity in secondary lymphoid organs and intestinal tissues are enriched for KLF2 expression, and distinct from FOXP3+ regulatory T cells or other differentiation lineages. Mice with conditional KLF2 deficiency in T cells develop spontaneous rectal prolapse and intestinal inflammation, phenotypes overturned by eliminating microbiota or reconstituting with donor KLF2+ cells. Activated KLF2+ cells selectively produce IL-10, and eliminating IL-10 overrides their suppressive function in vitro and protection against intestinal inflammation in vivo. Together with reduced KLF2+ CD4 cell accumulation in Crohn's disease, a necessity for the KLF2+ subpopulation of T regulatory type 1 (Tr1) cells in sustaining commensal tolerance is demonstrated.

Multi-omics analysis of mucosal and systemic immunity to SARS-CoV-2 after birth.

The dynamics of immunity to infection in infants remain obscure. Here, we used a multi-omics approach to perform a longitudinal analysis of immunity to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in infants and young children by analyzing blood samples and weekly nasal swabs collected before, during, and after infection with Omicron and non-Omicron variants. Infection stimulated robust antibody titers that, unlike in adults, showed no sign of decay for up to 300 days. Infants mounted a robust mucosal immune response characterized by inflammatory cytokines, interferon (IFN) α, and T helper (Th) 17 and neutrophil markers (interleukin [IL]-17, IL-8, and CXCL1). The immune response in blood was characterized by upregulation of activation markers on innate cells, no inflammatory cytokines, but several chemokines and IFNα. The latter correlated with viral load and expression of interferon-stimulated genes (ISGs) in myeloid cells measured by single-cell multi-omics. Together, these data provide a snapshot of immunity to infection during the initial weeks and months of life.

Intestinal permeability in patients undergoing stem cell transplantation correlates with systemic acute phase responses and dysbiosis.

Intestinal permeability may correlate with adverse outcomes during hematopoietic stem cell transplantation (HSCT), but longitudinal quantification with traditional oral mannitol and lactulose is not feasible in HSCT recipients because of mucositis and diarrhea. A modified lactulose:rhamnose (LR) assay is validated in children with environmental enteritis. Our study objective was to quantify peri-HSCT intestinal permeability changes using the modified LR assay. The LR assay was administered before transplant, at day +7 and +30 to 80 pediatric and young adult patients who received allogeneic HSCT. Lactulose and rhamnose were detected using urine mass spectrometry and expressed as an L:R ratio. Metagenomic shotgun sequencing of stool for microbiome analyses and enzyme-linked immunosorbent assay analyses of plasma lipopolysaccharide binding protein (LBP), ST2, REG3α, claudin1, occludin, and intestinal alkaline phosphatase were performed at the same timepoints. L:R ratios were increased at day +7 but returned to baseline at day +30 in most patients (P = .014). Conditioning regimen intensity did not affect the trajectory of L:R (P = .39). Baseline L:R ratios did not vary with diagnosis. L:R correlated with LBP levels (r2 = 0.208; P = .0014). High L:R ratios were associated with lower microbiome diversity (P = .035), loss of anaerobic organisms (P = .020), and higher plasma LBP (P = .0014). No adverse gastrointestinal effects occurred because of LR. Intestinal permeability as measured through L:R ratios after allogeneic HSCT correlates with intestinal dysbiosis and elevated plasma LBP. The LR assay is well-tolerated and may identify transplant recipients who are more likely to experience adverse outcomes.

The microbiome in adolescents with irritable bowel syndrome and changes with percutaneous electrical nerve field stimulation.

BACKGROUND: Irritable bowel syndrome (IBS), a disorder of the gut-brain axis, is affected by the microbiome. Microbial studies in pediatric IBS, especially for centrally mediated treatments, are lacking. We compared the microbiome between pediatric IBS patients and healthy controls (HC), in relation to symptom severity, and with percutaneous electrical nerve field stimulation (PENFS), a non-invasive treatment targeting central pain pathways. METHODS: We collected a stool sample, questionnaires and a 1-2 week stool and pain diary from 11 to 18 years patients with IBS. A patient subset completed 4 weeks of PENFS and repeated data collection immediately after and/or 3 months after treatment. Stool samples were collected from HC. Samples underwent metagenomic sequencing to evaluate diversity, composition, and abundance of species and MetaCyc pathways. KEY RESULTS: We included 27 cases (15.4 ± 2.5 year) and 34 HC (14.2 ± 2.9 year). Twelve species including Firmicutes spp., and carbohydrate degradation/long-chain fatty acid (LCFA) synthesis pathways, were increased in IBS but not statistically significantly associated with symptom severity. Seventeen participants (female) who completed PENFS showed improvements in pain (p = 0.012), disability (p = 0.007), and catastrophizing (p = 0.003). Carbohydrate degradation and LCFA synthesis pathways decreased post-treatment and at follow-up (FDR p-value <0.1). CONCLUSIONS AND INFERENCES: Firmicutes, including Clostridiaceae spp., and LCFA synthesis pathways were increased in IBS patients suggesting pain-potentiating effects. PENFS led to marked improvements in abdominal pain, functioning, and catastrophizing, while Clostridial species and LCFA microbial pathways decreased with treatment, suggesting these as potential targets for IBS centrally mediated treatments.

IEC-intrinsic IL-1R signaling holds dual roles in regulating intestinal homeostasis and inflammation.

Intestinal epithelial cells (IECs) constitute a critical first line of defense against microbes. While IECs are known to respond to various microbial signals, the precise upstream cues regulating diverse IEC responses are not clear. Here, we discover a dual role for IEC-intrinsic interleukin-1 receptor (IL-1R) signaling in regulating intestinal homeostasis and inflammation. Absence of IL-1R in epithelial cells abrogates a homeostatic antimicrobial program including production of antimicrobial peptides (AMPs). Mice deficient for IEC-intrinsic IL-1R are unable to clear Citrobacter rodentium (C. rodentium) but are protected from DSS-induced colitis. Mechanistically, IL-1R signaling enhances IL-22R-induced signal transducer and activator of transcription 3 (STAT3) phosphorylation in IECs leading to elevated production of AMPs. IL-1R signaling in IECs also directly induces expression of chemokines as well as genes involved in the production of reactive oxygen species. Our findings establish a protective role for IEC-intrinsic IL-1R signaling in combating infections but a detrimental role during colitis induced by epithelial damage.

Airway transcriptome networks identify susceptibility to frequent asthma exacerbations in children.

BACKGROUND: Frequent asthma exacerbators, defined as those experiencing more than 1 hospitalization in a year for an asthma exacerbation, represent an important subgroup of individuals with asthma. However, this group remains poorly defined and understudied in children. OBJECTIVE: Our aim was to determine the molecular mechanisms underlying asthma pathogenesis and exacerbation frequency. METHODS: We performed RNA sequencing of upper airway cells from both frequent and nonfrequent exacerbators enrolled in the Ohio Pediatric Asthma Repository. RESULTS: Through molecular network analysis, we found that nonfrequent exacerbators display an increase in modules enriched for immune system processes, including type 2 inflammation and response to infection. In contrast, frequent exacerbators showed expression of modules enriched for nervous system processes, such as synaptic formation and axonal outgrowth. CONCLUSION: These data suggest that the upper airway of frequent exacerbators undergoes peripheral nervous system remodeling, representing a novel mechanism underlying pediatric asthma exacerbation.

Systems biological assessment of the temporal dynamics of immunity to a viral infection in the first weeks and months of life.

The dynamics of innate and adaptive immunity to infection in infants remain obscure. Here, we used a multi-omics approach to perform a longitudinal analysis of immunity to SARS-CoV-2 infection in infants and young children in the first weeks and months of life by analyzing blood samples collected before, during, and after infection with Omicron and Non-Omicron variants. Infection stimulated robust antibody titers that, unlike in adults, were stably maintained for >300 days. Antigen-specific memory B cell (MCB) responses were durable for 150 days but waned thereafter. Somatic hypermutation of V-genes in MCB accumulated progressively over 9 months. The innate response was characterized by upregulation of activation markers on blood innate cells, and a plasma cytokine profile distinct from that seen in adults, with no inflammatory cytokines, but an early and transient accumulation of chemokines (CXCL10, IL8, IL-18R1, CSF-1, CX3CL1), and type I IFN. The latter was strongly correlated with viral load, and expression of interferon-stimulated genes (ISGs) in myeloid cells measured by single-cell transcriptomics. Consistent with this, single-cell ATAC-seq revealed enhanced accessibility of chromatic loci targeted by interferon regulatory factors (IRFs) and reduced accessibility of AP-1 targeted loci, as well as traces of epigenetic imprinting in monocytes, during convalescence. Together, these data provide the first snapshot of immunity to infection during the initial weeks and months of life.

Intestinal epithelial HDAC3 and MHC class II coordinate microbiota-specific immunity.

Aberrant immune responses to resident microbes promote inflammatory bowel disease and other chronic inflammatory conditions. However, how microbiota-specific immunity is controlled in mucosal tissues remains poorly understood. Here, we found that mice lacking epithelial expression of microbiota-sensitive histone deacetylase 3 (HDAC3) exhibited increased accumulation of commensal-specific CD4+ T cells in the intestine, provoking the hypothesis that epithelial HDAC3 may instruct local microbiota-specific immunity. Consistent with this, microbiota-specific CD4+ T cells and epithelial HDAC3 expression were concurrently induced following early-life microbiota colonization. Further, epithelium-intrinsic ablation of HDAC3 decreased commensal-specific Tregs, increased commensal-specific Th17 cells, and promoted T cell-driven colitis. Mechanistically, HDAC3 was essential for NF-κB-dependent regulation of epithelial MHC class II (MHCII). Epithelium-intrinsic MHCII dampened local accumulation of commensal-specific Th17 cells in adult mice and protected against microbiota-triggered inflammation. Remarkably, HDAC3 enabled the microbiota to induce MHCII expression on epithelial cells and limit the number of commensal-specific T cells in the intestine. Collectively, these data reveal a central role for an epithelial histone deacetylase in directing the dynamic balance of tissue-intrinsic CD4+ T cell subsets that recognize commensal microbes and control inflammation.

Delayed Microbial Maturation Durably Exacerbates Th17-driven Asthma in Mice.

Microbial maturation disrupted by early-life dysbiosis has been linked with increased asthma risk and severity; however, the immunological mechanisms underpinning this connection are poorly understood. We sought to understand how delaying microbial maturation drives worsened asthma outcomes later in life and its long-term durability. Drinking water was supplemented with antibiotics on Postnatal Days 10-20. To assess the immediate and long-term effects of delaying microbial maturation on experimental asthma, we initiated house dust mite exposure when bacterial diversity was either at a minimum or had recovered. Airway hyperresponsiveness, histology, pulmonary leukocyte recruitment, flow cytometric analysis of cytokine-producing lymphocytes, and assessment of serum IgG1 (Immunoglobulin G1) and IgE (Immunoglobulin E) concentrations were performed. RT-PCR was used to measure IL-13 (Interleukin 13)-induced gene expression in sequentially sorted mesenchymal, epithelial, endothelial, and leukocyte cell populations from the lung. Delayed microbial maturation increased allergen-driven airway hyperresponsiveness and Th17 frequency compared with allergen-exposed control mice, even when allergen exposure began after bacterial diversity recovered. Blockade of IL-17A (Interleukin 17A) reversed the airway hyperresponsiveness phenotype. In addition, allergen exposure in animals that experienced delayed microbial maturation showed signs of synergistic signaling between IL-13 and IL-17A in the pulmonary mesenchymal compartment. Delaying microbial maturation in neonates promotes the development of more severe asthma by increasing Th17 frequency, even if allergen exposure is initiated weeks after microbial diversity is normalized. In addition, IL-17A-aggravated asthma is associated with increased expression of IL-13-induced genes in mesenchymal, but not epithelial cells.

Patient-Reported Outcomes Correlate With Microbial Community Composition Independent of Mucosal Inflammation in Pediatric Inflammatory Bowel Disease.

BACKGROUND: Inflammatory bowel diseases (IBDs) involve an aberrant host response to intestinal microbiota causing mucosal inflammation and gastrointestinal symptoms. Patient-reported outcomes (PROs) are increasingly important in clinical care and research. Our aim was to examine associations between PROs and fecal microbiota in patients 0 to 22 years of age with IBD. METHODS: A longitudinal, prospective, single-center study tested for associations between microbial community composition via shotgun metagenomics and PROs including stool frequency and rectal bleeding in ulcerative colitis (UC) and abdominal pain and stool frequency in Crohn's disease (CD). Mucosal inflammation was assessed with fecal calprotectin. A negative binomial mixed-effects model including clinical characteristics and fecal calprotectin tested for differentially abundant species and metabolic pathways by PROs. RESULTS: In 70 CD patients with 244 stool samples, abdominal pain correlated with increased relative abundance of Haemophilus and reduced Clostridium spp. There were no differences relative to calprotectin level. In 23 UC patients with 76 samples, both rectal bleeding and increased stool frequency correlated with increased Klebsiella and reduced Bacteroides spp. Conversely, UC patients with lower calprotectin had reduced Klebsiella. Both UC and CD patients with active symptoms exhibited less longitudinal microbial community stability. No differences in metabolic pathways were observed in CD. Increased sulfoglycolysis and ornithine biosynthesis correlated with symptomatic UC. CONCLUSIONS: Microbial community composition correlated with PROs in both CD and UC. Metabolic pathways differed relative to PROs in UC, but not CD. Data suggest that microbiota may contribute to patient symptoms in IBD, in addition to effects of mucosal inflammation.

Real world population pharmacokinetic study in children and young adults with inflammatory bowel disease discovers novel blood and stool microbial predictors of vedolizumab clearance.

BACKGROUND: Vedolizumab for inflammatory bowel disease (IBD) is often intensified based on distinct pharmacokinetics in children. Prior adult-specific population pharmacokinetic models have identified limited covariates of drug clearance. AIMS: To establish a population pharmacokinetic model for children and young adults to identify novel covariates of drug clearance to better account for paediatric-specific inter-patient variability in vedolizumab pharmacokinetics; a key secondary exploratory aim was to identify microbial signatures of pharmacokinetic outcomes in a subset of patients. METHODS: The study included data from 463 observed vedolizumab concentrations (59 peaks and 404 troughs) from 74 patients with IBD (52 with Crohn's disease and 22 with ulcerative colitis or unclassified IBD, median age 16 years). Pharmacokinetic analysis was conducted with non-linear mixed effects modelling. For the evaluation of the exposure-response relationship, clinical outcomes were evaluated by trough levels, clearance and vedolizumab exposure. Whole-genome metagenomic sequencing was conducted at baseline and week 2. RESULTS: A two-compartment population pharmacokinetic model was identified with a clear correlation between CL and weight, erythrocyte sedimentation rate, and hypoalbuminemia. Trough concentrations before infusion 3 (37 µg/ml) and before infusion 4 (20 µg/ml) best predicted steroid-free clinical remission at infusion 4. Using faecal metagenomics, we identified an early (baseline and week 2) abundance of butyrate-producing species and pathways that were associated with an infusion 4 trough concentration >20 µg/ml. CONCLUSIONS: This novel paediatric vedolizumab pharmacokinetic model could inform precision dosing. While additional studies are needed, an abundance of faecal butyrate producers is associated with early response to vedolizumab, suggesting that microbial analysis may be beneficial to biological selection.

Single Site Experience of the use of Monoclonal Antibodies for the Treatment of COVID-19 in High-risk Pediatric and Young Adult Patients.

BACKGROUND: Effective therapeutic agents for the treatment of COVID-19 have been investigated since the onset of the pandemic. Monoclonal antibodies targeting the spike protein of SARS-CoV-2 have been developed for the treatment of mild or moderate COVID disease in high-risk populations. Despite widespread use in the adult population, data are limited on the safety and efficacy of monoclonal antibody infusions in the adolescent and young adult population. METHODS: Patients who received bamlanivimab, bamlanivimab-etesevimab, casirivimab-imdevimab, or sotrovimab for treatment of mild-to-moderate COVID-19 disease at Cincinnati Children's Hospital Medical Center from 5/1/2020 to 3/1/2022 were identified retrospectively. Patient data including demographics, adverse events, and outcomes were extracted from patients' charts and summarized by standard descriptive summaries. RESULTS: Ninety-four patients received monoclonal antibody therapy, of which 14 (14.9%) received either bamlanivimab or bamlanivimab-etesevimab, 54 (57.4%) received casirivimab-imdevimab, and 26 (27.6%) received sotrovimab. Ten patients (10.6%) experienced one or more infusion-related adverse event. Of the patients who experienced adverse events, all resolved with cessation of infusion. No life-threatening events or deaths occurred. Within 90 days of receiving a monoclonal antibody, 12 patients (12.7%) required additional medical care for ongoing COVID symptoms. Five of these were either hospitalized or received escalation of care while already in the hospital. All subsequently fully recovered. Neither infusion-related adverse events nor progression to hospitalization for ongoing COVID-19 symptoms following monoclonal antibody administration were associated with any particular underlying condition. CONCLUSIONS: Overall, monoclonal antibodies are reasonably well-tolerated COVID-19 therapies in high-risk adolescent and young adult populations.

Friendly fungi: symbiosis with commensal Candida albicans.

Mucosal tissues are constitutively colonized by a wide assortment of host-adapted microbes. This includes the polymorphic fungus Candida albicans which is a primary target of human adaptive responses. Immunogenicity is replicated after intestinal colonization in preclinical models with a surprising array of protective benefits for most hosts, but harmful consequences for a few. The interaction between fungus and host is complex, and traditionally, the masking of antigenic fungal ligands has been viewed as a tactic for fungal immune evasion during invasive infection. However, we propose that dynamic expression of cell wall moieties, host cell lysins, and other antigenic C. albicans determinants is necessary during the more ubiquitous context of intestinal colonization to prime immunogenicity and optimize mammalian host symbiosis.