Pregnancy is an immunological marvel allowing intimate approximation between genetically discordant tissues of maternal and fetal origin. Shared immunity across the maternal-fetal dyad including intact cells of maternal and fetal origin establishing microchimerism in both individuals after parturition and protection by vertically transferred maternal IgG antibodies are increasingly recognized. Nonetheless, basic questions regarding why mothers do not reject allogeneic fetal tissues and why developing fetal immune cells do not reject allogenic maternal tissue remain unresolved. Establishing how this essential process works holds exciting promise for new therapeutic strategies for common disorders linked with fetal intolerance such as stillbirth, preeclampsia and preterm birth. Besides translational application for improving the health of children through improved pregnancy outcomes, pregnancy also represents an incredibly instructive platform for investigating how immunology works, which can be applied to other physiological contexts where expanded immune tolerance is desired. This perspective highlights several emerging immunological considerations from a pregnancy-focused viewpoint, including maternal immune cell memory, microchimerism and vertically transferred protective antibodies, with particular attention to unresolved questions and application to immunity in non-reproductive contexts.

BACKGROUND:Bloodstream infections (BSI) remain a major cause of morbidity and mortality in preterm infants. Although BSI pathogens vary geographically, the role of local microbial colonization patterns and clinical practices in driving these differences is not well understood. METHODS:We conducted a prospective cohort study on 127 preterm infants from two geographically distinct NICUs: University of Cincinnati Medical Center (UCMC, USA) and Children's Hospital, Zhejiang University School of Medicine (ZCH, China). Six hundred and sixty-nine longitudinal stool and skin samples collected during the first three weeks of life underwent metagenomic sequencing. Associations between microbiome composition, clinical factors, and BSI epidemiology were evaluated using Generalized Linear Mixed Models and Random Forest. RESULTS:Distinct gut and skin microbiome profiles were observed between NICUs and corresponded closely with local BSI patterns. Staphylococcus aureus predominated at UCMC, while Klebsiella pneumoniae and Enterococcus species were more common at ZCH. Skin microbiota showed strong association with BSI isolates, implicating the skin as an underrecognized potential reservoir for pathogen translocation. Linear mixed models and Random Forest machine learning approaches revealed that clinical practices, including intravenous catheter placement and antibiotic exposure had greater influence on microbiome composition than geographic location alone. CONCLUSIONS:Our findings demonstrate that modifiable clinical care practices shape the developing microbiome of preterm infants and contribute to geographic differences in BSI epidemiology. The skin microbiome represents a potentially significant risk factor for invasive infection. Further work to clarify how specific clinical practices influence pathogen colonization may inform strategies to reduce BSI incidence in preterm infants.

Background Pediatric oncology and hematopoietic stem cell transplant (HSCT) patients have elevated risk for Clostridioides difficile infection (CDI), which can prolong hospitalization and delay chemotherapy. Colonization is an important prelude to symptomatic CDI. We sought to characterize colonization status in these patients. Methods We retrospectively studied 276 stools longitudinally collected over 34 months from 32 HSCT and 12 oncology patients treated at a single tertiary center. Specimens were cultured for C difficile and compared by whole genome sequencing. The fecal microbiome was characterized by 16S rRNA gene sequencing. Results Baseline cultures were positive in 16 (50%) HSCT patients and 2 (12%) oncology. On subsequent samples, 64% of patients who were initially negative acquired colonization: 8 of 15 (53%) HSCT and 8 of 10 (80%) oncology. Nine clonal strains and 25 multilocus sequence types were identified by whole genome sequencing, with 4 clones found in both cohorts. Nine patients had different strains at different time points. Seven clonal strains were found in multiple patients. Seven (15.9%) patients had symptomatic CDI. C difficile-positive stools had greater microbial diversity than negative stools in both the oncology cohort (Simpson diversity index, 0.07; 95% CI, .01-.14; P = .03) and the HSCT cohort (0.15; 95% CI, .07-.24; P < .001). Conclusions C difficile acquisition and colonization are common in pediatric oncology and HSCT patients. The high prevalence of clonally related strains in multiple patients suggests that asymptomatic patients may be important reservoirs of this pathogen and lead to symptomatic CDI in some patients. Gut microbial composition may influence the risk of colonization.

OBJECTIVES:Pediatric acute pancreatitis (AP), Crohn's disease (CD), and irritable bowel syndrome (IBS) are associated with gut dysbiosis, but differences and similarities between conditions are unknown. We hypothesized that gut microbial ecology would differ across these disorders. METHODS:Stool was collected from 120 subjects (AP [n = 30], CD [n = 29], IBS Rome IV [n = 27], and healthy controls [HC, n = 34]). Shotgun metagenomic sequencing was performed on extracted DNA and taxonomic and functional profiles obtained using sylph and HUMAnN3 with default parameters. RESULTS:Age interquartile range for all participants was 8.1-17.7 years. Shannon diversity was decreased in AP compared to IBS or HC (p < 0.0001) and similar to CD (p = 0.97). CD differed from IBS (p = 0.001) and HC (p < 0.0001) while IBS and HC were similar (p = 0.61). Ordination of the first two principal coordinate analyses axes showed sample clustering by condition (R2 = 0.12, p < 0.001), and differences between all conditions in pairwise comparisons (p < 0.001). Escherichia coli, Ruminococcus gnavus, Staphylococcus aureus, and Thomasciavelia ramosa remained enriched when all conditions (AP, CD, and IBS) were compared as a single group to HC. Using a random forest machine learning algorithm for species relative abundance, the ability to classify a sample to each condition versus all others was highest for CD (area under the receiver operative characteristic curve, AUC = 0.97), followed by AP (AUC = 0.92), HC (AUC = 0.88), and IBS (AUC = 0.83). CONCLUSION:Organic disorders (AP and CD) are associated with significant gut dysbiosis than IBS which appears more like HC. Interventions targeting shifts in commensals in AP and CD may be helpful in improving outcomes in both disorders.

Commensal microbes can cause invasive infection but can also stimulate protective immune responses as exemplified by the gut pathobiont Candida albicans. This species primes systemic Th17 immunogenicity which protects against disseminated infection, and yet the fungal determinants driving protection remain uncertain. Here we show an essential role for the cytolytic toxin candidalysin for C. albicans colonization-induced systemic Th17 immunogenicity and protection against invasive infection. Mice intestinally colonized with candidalysin-deficient cells show reduced accumulation of CD4 T cells with defined fungal specificity, despite similar intestinal colonization levels to wildtype C. albicans cells. Fungal-specific RORγt+ CD4 T cells are particularly reduced together with their production of IL17A and IL17F cytokines, whereas expression of transcription factors and production of cytokines representative of other helper T cell lineages are unaffected. Protection against fungemia conferred by colonization with wildtype C. albicans is overturned in mice colonized with candidalysin-deficient cells as shown by increased fungal pathogen burden and reduced survival after intravenous infection. These results establish the necessity for candidalysin for priming Th17 fungal-specific adaptive immune cells and highlight paradoxical protective roles for this fungal virulence factor for promoting host defense against invasive systemic disease.

Dysbiosis after allogeneic hematopoietic stem cell transplant (allo-HSCT) predisposes to acute gastrointestinal (GI) graft-versus-host disease (GVHD). Human milk oligosaccharides (HMOs) are prebiotics that establish a favorable intestinal microbiome. We hypothesized that peri-transplant HMOs would reduce dysbiosis, and conducted a prospective phase I/II study (NCT04263597 Clinicaltrials.gov) in which 70 patients received oral, daily 2'-fucosyllactose (2'-FL), the most abundant HMO, from start of conditioning through day +30. Primary phase I and phase II endpoints were safety and tolerability of 2'-FL and longitudinal preservation of microbiome diversity, respectively. Phase I and phase II patients with ³60% adherence were evaluated by correlative analyses. Twenty-nine age-matched patients with available samples in our institutional biorepository served as contemporary controls. 2'-FL was safe and well-tolerated on the phase I study, which established dosing for the phase II study. Shannon diversity was preserved in 2'-FL recipients and declined from baseline to day +30 in controls (p=0.04). Generalized linear mixed model analysis revealed higher association of Bifidobacteria and Blautia with 2'-FL (adjusted p<0.05). Higher fecal isoleucine (p=0.005), tyrosine (p=0.05), and taurine (p=0.04) were observed in 2'-FL recipients, all associated with protection and regeneration of intestinal epithelium. Lower plasma reg3a (p=0.053) and ST2 levels (p=0.038) were observed in 2'-FL recipients compared to controls. Incidence of grade II-IV acute GI GVHD was 0% in 2'-FL recipients compared to 17% in controls (p=0.009). Adenovirus reactivation was 0% in 2'-FL recipients compared to 17% in controls (p=0.009). 2'-FL is safe and modifies the gut microbiome in children following allo-HSCT.

Age-associated dysregulation of the gut microbiota is a hallmark of aging and has been linked to multiple age-related diseases, yet upstream host factors driving these changes remain incompletely defined. Extensive bidirectional crosstalk between gut microbiota and mucosal immunity has been described. Aging is accompanied by a progressive decline in immune function, collectively termed aging-associated immune remodeling (AAIR). AAIR encompasses widespread compositional and functional changes that impair an effective response to pathogens, vaccines, and tissue damage. We examined whether AAIR is an upstream host factor influencing the composition of the microbiome upon aging. Hallmarks of AAIR were also present in the ileal lamina propria, including reduced naïve CD4+ and CD8+ T cell populations and expansion of memory and regulatory T cell subsets. To test whether mucosal AAIR reflects intrinsic aging of the hematopoietic system, we used an HSC transplantation model where young RAG1−/− recipients develop an adaptive immune system derived exclusively from either young or aged donor HSC in an otherwise young host environment. Recipients of aged HSCs recapitulated key features of mucosal AAIR, particularly loss of naïve T cells, demonstrating that AAIR in the ileal LP is driven at least in part by aged HSCs. Shotgun metagenomic sequencing of fecal samples revealed that ileal AAIR is associated with alterations in gut microbiota. In detail, there was a reduced abundance of taxa associated with the vitamin B6 (VB6) biosynthesis and salvage pathways. Accordingly, VB6 levels in serum were reduced in mice with aged immune systems. Our findings link AAIR to reduced microbial VB6 pathway abundance and lower systemic VB6 availability, suggesting that immune aging shapes the functional output of the microbiome in ways that diminish its VB6 biosynthetic capacity. This postulates an immune-microbiome-VB6 association that warrants further investigations for therapeutic strategies to increase VB6 levels upon aging.

Escherichia coli is a leading cause of neonatal sepsis, with infection occurring in approximately one in every 1,000 live births1,2. However, with E. coli colonization beginning soon after birth3-5 and defects in neonatal host defence maturation6-9, an alternative consideration is why infection does not occur even more frequently. Here we show that newborn babies with E. coli sepsis have selectively reduced vertically transferred natural antibodies that recognize E. coli, mechanistically explaining their susceptibility to infection. Complementary preclinical studies show that preconceptual intestinal colonization with probiotic E. coli Nissle 1917 (EcN)10 primes anti-E. coli immunoglobulin G (IgG) antibodies with broad cross-reactivity to clinical isolates responsible for neonatal sepsis that override the inherent susceptibility of neonatal mice. Outer membrane protein A (OmpA) is a target of maternal IgG and is also essential for EcN colonization-induced serological immunogenicity. Upon vertical transfer to neonates, colonization-primed anti-E. coli IgG uniquely protects against infection via opsonization, requiring both complement and IgG Fc receptors. Compared with specimens from sex and gestational age-matched healthy control babies without infection, dried blood spot specimens collected one day after birth from 100 babies with E. coli sepsis show consistently reduced IgG titres to pooled E. coli clinical isolates and OmpA, along with impaired IgG-dependent antibacterial opsonization. Together, these results demonstrate that natural infection susceptibility of neonates is efficiently rescued by anti-E. coli IgG and identify defects in pathogen-targeted vertically transferred immunity as a primary risk factor for severe invasive infection in newborn babies.

Background Bloodstream infections (BSIs) remain a major cause of disease and death in preterm infants. Although BSI pathogens vary geographically, the role of local microbial colonization patterns and clinical practices in driving these differences is not well understood.Methods We conducted a prospective cohort study on 127 preterm infants from 2 geographically distinct neonatal intensive care units: the University of Cincinnati Medical Center (UCMC) in Cincinnati, Ohio, and Children's Hospital, Zhejiang University School of Medicine (ZCH) in Hangzhou, China. Metagenomic sequencing was performed in 669 longitudinal stool and skin samples collected during the first 3 weeks of life. Associations between microbiome composition, clinical factors, and BSI epidemiology were evaluated using generalized linear mixed and random forest models.Results Distinct gut and skin microbiome profiles were observed in the comparison between neonatal intensive care units, and these corresponded closely with local BSI patterns. Staphylococcus aureus predominated at UCMC, while Klebsiella pneumoniae and Enterococcus species were more common at ZCH. Skin microbiota showed strong association with BSI isolates, implicating the skin as an underrecognized potential reservoir for pathogen translocation. Linear mixed models and random forest analysis revealed that clinical practices, including intravenous catheter placement and antibiotic exposure, had greater influence on microbiome composition than geographic location alone.Conclusions Our findings demonstrate that modifiable clinical care practices shape the developing microbiome of preterm infants and contribute to geographic differences in BSI epidemiology. The skin microbiome represents a potentially significant risk factor for invasive infection. Further work to clarify how specific clinical practices influence pathogen colonization may inform strategies to reduce the incidence of BSIs in preterm infants. This study demonstrates that variations in microbiome composition between preterm infants in US and Chinese neonatal intensive care units are associated with distinct bloodstream infection patterns, revealing modifiable clinical factors that contribute importantly to geographic differences in bloodstream infection epidemiology.

Homeostasis in the intestinal epithelium depends on intestinal stem cells (ISCs). A reduction in the function of ISCs, caused by a decline of canonical Wnt signaling in ISCs, contributes to a reduced regenerative potential of the aged intestine. The composition of the intestinal microbiota changes upon aging. We report here that aging-associated changes in the composition of the microbiota result in reduced canonical Wnt signaling through Ascl2 in ISCs, which causes a decline in the regenerative potential of aged ISCs in vivo. We demonstrate, using microbiota transfer experiments, that interestingly, elevated levels of Akkermansia muciniphila in the intestine cause a reduction of Ascl2-mediated canonical Wnt signaling in ISCs and thus reduced regeneration of the aged epithelium. The composition of the intestinal microbiota thus plays a critical role in regulating the function of ISCs. Our data imply potential therapeutic approaches via modulation of the composition of microbiota for aging-associated changes in the function of ISCs.

ABSTRACT The immune response to viral infection is shaped by past exposures to related virus strains, a phenomenon known as imprinting. For severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), much of the population has been imprinted by a viral spike from an early strain, either through vaccination or infection during the early stages of the COVID-19 pandemic. As a consequence of this imprinting, infection with more recent SARS-CoV-2 strains primarily boosts cross-reactive antibodies elicited by the imprinting strain. Here we compare the neutralizing antibody specificities of imprinted individuals versus infants infected with a recent strain. Specifically, we use pseudovirus-based deep mutational scanning to measure how spike mutations affect neutralization by the serum antibodies of adults and children imprinted by the original vaccine versus infants with a primary infection by an XBB* variant. While the serum neutralizing activity of the imprinted individuals primarily targets the spike receptor-binding domain (RBD), the serum neutralizing activity of infants infected with only XBB* mostly targets the spike N-terminal domain. In these infants, secondary exposure to the XBB* spike via vaccination shifts more of the neutralizing activity toward the RBD, although the specific RBD sites targeted are different from imprinted adults. The dramatic differences in neutralization specificities among individuals with different exposure histories likely impact SARS-CoV-2 evolution. IMPORTANCE We show that a person’s exposure history to different SARS-CoV-2 strains strongly affects which regions on the viral spike that their neutralizing antibodies target. In particular, infants who have just been infected once with a recent viral strain make neutralizing antibodies that target different regions of the viral spike than adults or children who have been exposed to both older and more recent strains. This person-to-person heterogeneity means that the same viral mutation can have different impacts on the antibody immunity of different people.

BACKGROUND:Early childhood wheeze is characterized by heterogeneous trajectories having differential associations with later-life asthma development. OBJECTIVE:We sought to determine how early-life wheeze trajectories impact later life asthma gene expression. METHODS:The Children's Respiratory Environmental Workgroup is a collective of 12 birth cohorts, 7 of which conducted an additional visit with a nasal lavage collected and subjected to bulk RNA-sequencing. Early-life wheeze trajectories were defined using latent class analysis of longitudinal early-life wheezing data. Weighted gene correlation network analysis was used to associate gene expression patterns and current asthma with early-life wheeze trajectories. RESULTS:We investigated 743 children (mean age, 17 ± 5.1 years; 360 [48.5%] male). Four patterns of early-life wheeze were identified: infrequent, transient, late-onset, and persistent. Early-life transient wheeze was associated with gene expression patterns related to increased antiviral response, and late-onset wheeze was associated with decreased insulin signaling and glucose metabolism. Early-life persistent wheeze was associated with gene expression modules of type 2 inflammation and epithelial development, but these modules did not distinguish those with current asthma. Children who had persistent wheeze in early life and current asthma displayed a unique increase in expression of genes enriched for neuronal processes and ciliated epithelial function compared with those without asthma. CONCLUSIONS:Early-life longitudinal wheeze trajectories are associated with specific asthma transcriptomes later in life. These data suggest that early-life asthma prevention strategies may be most beneficial when tailored to the specific wheeze pattern.

Clonal haematopoiesis of indeterminate potential (CHIP) involves the gradual expansion of mutant pre-leukaemic haematopoietic cells, which increases with age and confers a risk for multiple diseases, including leukaemia and immune-related conditions1. Although the absolute risk of leukaemic transformation in individuals with CHIP is very low, the strongest predictor of progression is the accumulation of mutant haematopoietic cells2. Despite the known associations between CHIP and increased all-cause mortality, our understanding of environmental and regulatory factors that underlie this process during ageing remains rudimentary. Here we show that intestinal alterations, which can occur with age, lead to systemic dissemination of a microbial metabolite that promotes pre-leukaemic cell expansion. Specifically, ADP-D-glycero-β-D-manno-heptose (ADP-heptose), a biosynthetic bi-product specific to Gram-negative bacteria3-5, is uniquely found in the circulation of older individuals and favours the expansion of pre-leukaemic cells. ADP-heptose is also associated with increased inflammation and cardiovascular risk in CHIP. Mechanistically, ADP-heptose binds to its receptor, ALPK1, triggering transcriptional reprogramming and NF-κB activation that endows pre-leukaemic cells with a competitive advantage due to excessive clonal proliferation. Collectively, we identify that the accumulation of ADP-heptose represents a direct link between ageing and expansion of rare pre-leukaemic cells, suggesting that the ADP-heptose-ALPK1 axis is a promising therapeutic target to prevent progression of CHIP to overt leukaemia and immune-related conditions.

IntroductionEarly-life dysbiosis is associated with increased risk of asthma development but the underlying mechanisms remain unclear. Although eosinophils have been reported in the developing lung, their contributions to alveolar morphogenesis and lung mechanics have not been functionally interrogated.MethodsMaternal exposure to antibiotics (ABX) was used to induce early-life offspring dysbiosis, and the effects on lung function and development was assessed. Similar measurements were made in mice lacking eosinophils due to genetic modification, or administration of IL-5 blocking agents.ResultsABX exposure between Embryonic Day 15 (E15) and post-natal day 28 (PN28), increased allergen-induced, and baseline airway hyperreactivity (AHR). Similar observations were made when maternal ABX exposure was limited to PN10 to PN20. Complete characterization of baseline lung mechanics demonstrated downward-shifted pulmonary PV loops, increased small airway resistance, decreased compliance, and reduced inspiratory capacity at weaning and 14 months of age. Consistent with observation of small airway dysfunction, offspring of ABX-exposed dams demonstrated significantly smaller alveoli at multiple stages of lung development. Examination of recruitment to developing lungs demonstrated an exaggerated recruitment of eosinophils at key developmental periods (PN14) in offspring of ABX-exposed dams. Mice with fewer eosinophils (through genetic knockout, or treatment with anti-IL-5) display altered patterns of lung mechanics opposite to that seen in offspring of ABX-exposed dams.DiscussionThese data underscore an underappreciated role of eosinophils in homeostatic lung development and suggest that early life modulation of pulmonary eosinophil activity has long-term effects on susceptibility to the development of chronic lung diseases such as asthma.

Introduction:Optimizing vancomycin dosing in neonates is a critical yet complex goal. Traditional trough concentration-based dosing strategies correlate poorly with therapeutic efficacy and often fail to account for the significant renal function variability and drug clearance in neonates. The 24-hour area under the concentration-time curve to minimum inhibitory concentration (AUC24/MIC) ≥ 400 mg h/L has emerged as a superior pharmacodynamic target. Population pharmacokinetics (PopPK) models allow optimized dosing by incorporating neonatal-specific factors such as postmenstrual age (PMA), gestational age (GA), serum creatinine (SCr), and weight. Objective:To develop optimized vancomycin dosing regimens for neonates that achieve an 80% probability of target attainment (PTA) for an AUC24/MIC ≥ 400 mg h/L across diverse clinical cohorts and simulated neonatal populations. Methods:Real-world data from three international centers (Belgium, New Zealand, USA), including 610 individuals and 2399 vancomycin concentrations, were used to externally evaluate a previously published PopPK model (NONMEM®). Missing data, including body weight, were imputed using Amelia II version 1.7.3 for R, while Zelig for R integrated multiple imputed datasets. A virtual population of 10,000 neonates was independently generated using MATLAB to simulate clinical scenarios considering covariates such as PMA, GA, SCr, body weight, and imputed body length. Results:Simulations showed that PMA and SCr were key covariates that significantly improved PTA, particularly in preterm neonates. Preterm neonates achieved PTAs of 80% with daily doses of 30 or 40 mg/kg/day, while term neonates required 15 mg/kg every 8 hours or 20 mg/kg every 12 hours. The simulations demonstrated that these optimized dosing strategies achieved an 80% PTA for AUC24/MIC ≥ 400 mg h/L in the virtual neonatal population. For neonates with PMA < 29 weeks and SCr > 0.6 mg/dL, including SCr as a covariate increased the likelihood of achieving the target from 65% to 87%. Conclusion:Incorporating developmental factors like PMA and SCr into vancomycin dosing strategies achieved robust and clinically relevant outcomes. The optimized regimens achieved an 80% PTA for the AUC24/MIC target for preterm and term neonates. These findings offer a scalable framework for improving neonatal vancomycin pharmacotherapy across diverse populations and clinical settings.

Staphylococcus aureus (SA) skin colonization in pediatric atopic dermatitis (AD) increases risk for severe AD and development of other allergic diseases. Despite this, there is no consensus regarding the optimal method to detect SA. Studies comparing metagenomic shotgun sequencing (MSS) and culture-based methods in SA detection and relationships to AD outcomes are lacking. In the Mechanisms of Progression of Atopic Dermatitis to Asthma in Children (MPAACH) cohort, we defined SA colonization categories by contact agar plate sampling/culture and skin tape sampling/MSS: double negative, sequencing only positive, contact plate only positive, and double positive (n = 759). We assessed AD severity, sensitization, total IgE, and atopic outcomes across categories. Culture missed 69% of samples detected by MSS and MSS missed 54% of samples detected by culture. The double positive group exhibited higher AD severity, sensitization load, and total serum IgE, and was more likely to develop allergic rhinitis (AR) compared to other groups. Detection of SA by MSS or culture missed over half of the SA detected by the other method. Importantly, detection via both methods correlated with increased AD severity, sensitization, total IgE, and AR. Thus, these methods are complementary and both may be necessary for comprehensive evaluation of SA and its clinical and biologic impact.

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.

Topic Significance & Study Purpose/Background/RationalePatients undergoing hematopoietic stem cell transplant require a central venous catheter (CVC). Central line associated bloodstream infections (CLABSI) are associated with increase morbidity, mortality, and healthcare costs. Maintenance and disinfection of needleless connectors (NC) require significant efforts to prevent CLABSI and current guidelines are based on limited evidence. This study evaluates factors involved in NC care including disinfectant, scrubbing material, scrubbing time and human factors.Methods, Intervention, & AnalysisOne hundred NC were used for each study phase. A negative NC control group (10/100) were flushed with saline. A positive NC control group (10/100) and study groups were contaminated for 30 minutes with Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus mitis, Escherichia coli, and Pseudomonas aeruginosa. Positive control group had no scrubbing prior to flushing with saline. Two milliliters of saline were used to flush each group's NC into a sterile tube and 10 microliter loops inoculated the blood agar. For the study groups, 40/80 NC (group 1) was disinfected with 2% chlorhexidine gluconate (CHG) plus 70% isopropyl alcohol frepp; and 40/80 NC (group 2) was disinfected with 3.1% CHG plus 70% isopropyl alcohol swab. For both groups, NC were subdivided into four different scrubbing times: 15, 30, 45, and 60 seconds. After 24hrs cultures were analyzed. Three experienced nurses scrubbed NC for both groups and during the different scrubbing times. The same nurses repeated the study at a different date.Findings & InterpretationIn phase 1, group 1 had 8/40 (20%) positive cultures, while group 2 had 3/40 (7.5 %). Nurse pink had two positive cultures 2/14 (14%), nurse blue had two positive cultures 2/34 (5%) and nurse green had 7/32 (22%) positive cultures. In phase 2, group 1 had 4/40 (10%) positive cultures, while group 2 had 2/40 (5%). Nurse pink had one 1/24 (4%), nurse blue had 2/24 (8%) and nurse green had 3/32 (9%) positive cultures. No difference was observed for the different scrubbing times.Discussion & ImplicationsScrubbing time does not appear to impact disinfection. Scrubbing with 3.1% CHG plus 70% isopropyl alcohol swab appears to have better disinfection. In our study, human factors showed to affect disinfection results. A third study phase is currently undergoing.