Knoop, Kathryn A

Key points Staphylococcus aureus showed a significant increase in relative abundance in CRSwNP patients following endoscopic sinus surgery compared to pre‐surgery samples. Other Staphylococcus species were found to correlate positively with S. aureus in patients with nasal polyps; among those, S. caprae correlated strongly while being the most represented in samples. Patients with recurrent nasal polyp growth exhibited a substantially greater postoperative increase in the relative abundance of S. aureus .

Interaction between breast milk antibodies and gut microbes shape immune responses during weaning

Summary Oral tolerance promotes the suppression of immune responses to innocuous antigen and is primarily mediated by regulatory T cell (Tregs). The development of oral tolerance begins in early life during a “window of tolerance,” which occurs around weaning and is mediated by components in breastmilk. Herein, we review the factors dictating this window and how Tregs are uniquely educated in early life. In early life, the translocation of luminal antigen for Treg induction is primarily dictated by goblet cell‐associated antigen passages (GAPs). GAPs in the colon are negatively regulated by maternally‐derived epidermal growth factor and the microbiota, restricting GAP formation to the “periweaning” period (postnatal day 11–21 in mice, 4–6 months in humans). The induction of solid food also promotes the diversification of the bacteria such that bacterially‐derived metabolites known to promote Tregs—short‐chain fatty acids, tryptophan metabolites, and bile acids—peak during the periweaning phase. Further, breastmilk immunoglobulins—IgA and IgG—regulate both microbial diversity and the interaction of microbes with the epithelium, further controlling which antigens are presented to T cells. Overall, these elements work in conjunction to induce a long‐lived population of Tregs, around weaning, that are crucial for maintaining homeostasis in adults.

The health of the intestinal microbiota impacts tolerance at homeostasis and the strength of the inflammation response during acute bloodstream infections. A complete understanding of the feedback loop between systemic inflammation and dysregulation of the gut microbiota is necessary for inflammation management. Here we will review the many ways in which the microbiota can influence the systemic pro-inflammatory response. Short-chain fatty acids, produced through the microbial metabolism of dietary fibers, can suppress inflammation systemically; in the absence of a balanced diet or disruption of the microbiota through antibiotics, there is disrupted metabolite production, leading to systemic inflammation. Dysbiosis or inflammation in the intestines can lead to a breakdown of the sturdy intestinal–epithelial barrier. When this barrier is perturbed, immunogenic lipopolysaccharides or extracellular vesicles enter the bloodstream and induce excessive inflammation. Necessary clinical treatments, such as antifungals or antibacterials, induce microbiota dysregulation and thus increased risk of endotoxemia; though probiotics may aid in improving the microbiota health and have been shown to deflate inflammation during sepsis. Within this complicated relationship: What is in control, the dysbiotic microbiota or the systemic inflammation?

Abstract Sepsis can result from a variety of pathogens, originating from a range of sources. A vast range of presenting symptoms is included in the catch-all term of “bacteremia,” making diagnosis and prognosis particularly troublesome. One underexplored factor contributing to disparate outcomes is the age of the patient. Neonatal sepsis in very-low-birth-weight infants can result in vastly different immunological outcomes unique from sepsis in adults. It is also becoming increasingly clear, both from preclinical experimental models and clinical observations, that the age and history of previous microbial exposures can significantly influence the course of infection from sepsis and cytokine storms to immunopathology. In this study, we will explore key differences between neonatal and adult sepsis, experimental models used to study sepsis, and how responses to the surrounding microbial universe shape development of the immune system and impact, positively or negatively, the course of disease.

AbstractThe increasing incidence of food allergy remains a significant public health concern. Food allergy is partially due to a lack, or loss of tolerance to food allergens. Clinical outcomes surrounding early life practices, such as breastfeeding, antibiotic use and food allergen exposure, indicate the first year of life in children represents a unique time for shaping the immune system to reduce allergic outcomes. Animal models have identified distinctive aspects of when and where dietary antigens are delivered within the intestinal tract to promote oral tolerance prior to weaning. Additionally, animal models have identified contributions from maternal proteins from breast milk and bacterial products from the gut microbiota in regulating dietary antigen exposure and promoting oral tolerance, thus connecting decades of clinical observations on the benefits of breastfeeding, early food allergen introduction and antibiotic avoidance in the first year of life in reducing allergic outcomes. Here, we discuss how exposure to gut luminal antigens, including food allergens, is regulated in early life to generate protective tolerance and the implications of this process for preventing and treating food allergies.

Late-onset sepsis (LOS) and other systemic bloodstream infections are notable causes of neonatal mortality, particularly in prematurely born very low birth weight infants. Breastfeeding in early life has numerous health benefits, impacting the health of the newborn in both the short-term and in the long-term. Though the known benefits of an exclusive mother’s own milk diet in early life have been well recognized and described, it is less understood how breastfed infants enjoy a potential reduction in risk of LOS and other systemic infections. Here we review how gut residing pathogens within the intestinal microbiota of infants can cause a subset of sepsis cases and the components of breastmilk that may prevent the dissemination of pathogens from the intestine.

Late-onset sepsis (LOS) is a highly consequential complication of preterm birth and is defined by a positive blood culture obtained after 72 h of age. The causative bacteria can be found in patients’ intestinal tracts days before dissemination, and cohort studies suggest reduced LOS risk in breastfed preterm infants through unknown mechanisms. Reduced concentrations of epidermal growth factor (EGF) of maternal origin within the intestinal tract of mice correlated to the translocation of a gut-resident human pathogen Escherichia coli , which spreads systemically and caused a rapid, fatal disease in pups. Translocation of Escherichia coli was associated with the formation of colonic goblet cell-associated antigen passages (GAPs), which translocate enteric bacteria across the intestinal epithelium. Thus, maternally derived EGF, and potentially other EGFR ligands, prevents dissemination of a gut-resident pathogen by inhibiting goblet cell-mediated bacterial translocation. Through manipulation of maternally derived EGF and alteration of the earliest gut defenses, we have developed an animal model of pathogen dissemination which recapitulates gut-origin neonatal LOS.