| 1. |
- Kennedy, K. M., et al.
(author)
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Questioning the fetal microbiome illustrates pitfalls of low-biomass microbial studies
- 2023
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 613:7945, s. 639-649
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Journal article (peer-reviewed)abstract
- Whether the human fetus and the prenatal intrauterine environment (amniotic fluid and placenta) are stably colonized by microbial communities in a healthy pregnancy remains a subject of debate. Here we evaluate recent studies that characterized microbial populations in human fetuses from the perspectives of reproductive biology, microbial ecology, bioinformatics, immunology, clinical microbiology and gnotobiology, and assess possible mechanisms by which the fetus might interact with microorganisms. Our analysis indicates that the detected microbial signals are likely the result of contamination during the clinical procedures to obtain fetal samples or during DNA extraction and DNA sequencing. Furthermore, the existence of live and replicating microbial populations in healthy fetal tissues is not compatible with fundamental concepts of immunology, clinical microbiology and the derivation of germ-free mammals. These conclusions are important to our understanding of human immune development and illustrate common pitfalls in the microbial analyses of many other low-biomass environments. The pursuit of a fetal microbiome serves as a cautionary example of the challenges of sequence-based microbiome studies when biomass is low or absent, and emphasizes the need for a trans-disciplinary approach that goes beyond contamination controls by also incorporating biological, ecological and mechanistic concepts.
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| 2. |
- Dupont, A., et al.
(author)
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Age-Dependent Susceptibility to Enteropathogenic Escherichia coli (EPEC) Infection in Mice
- 2016
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In: Plos Pathogens. - : Public Library of Science (PLoS). - 1553-7366 .- 1553-7374. ; 12:5
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Journal article (peer-reviewed)abstract
- Enteropathogenic Escherichia coli (EPEC) represents a major causative agent of infant diarrhea associated with significant morbidity and mortality in developing countries. Although studied extensively in vitro, the investigation of the host-pathogen interaction in vivo has been hampered by the lack of a suitable small animal model. Using RT-PCR and global transcriptome analysis, high throughput 16S rDNA sequencing as well as immunofluorescence and electron microscopy, we characterize the EPEC-host interaction following oral challenge of newborn mice. Spontaneous colonization of the small intestine and colon of neonate mice that lasted until weaning was observed. Intimate attachment to the epithelial plasma membrane and microcolony formation were visualized only in the presence of a functional bundle forming pili (BFP) and type III secretion system (T3SS). Similarly, a T3SS-dependent EPEC-induced innate immune response, mediated via MyD88, TLR5 and TLR9 led to the induction of a distinct set of genes in infected intestinal epithelial cells. Infection-induced alterations of the microbiota composition remained restricted to the postnatal period. Although EPEC colonized the adult intestine in the absence of a competing microbiota, no microcolonies were observed at the small intestinal epithelium. Here, we introduce the first suitable mouse infection model and describe an age-dependent, virulence factor-dependent attachment of EPEC to enterocytes in vivo.
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| 3. |
- Fulde, M., et al.
(author)
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Neonatal selection by Toll-like receptor 5 influences long-term gut microbiota composition
- 2018
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 560:7719
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Journal article (peer-reviewed)abstract
- Alterations in enteric microbiota are associated with several highly prevalent immune-mediated and metabolic diseases(1-3), and experiments involving faecal transplants have indicated that such alterations have a causal role in at least some such conditions(4-6). The postnatal period is particularly critical for the development of microbiota composition, host-microbe interactions and immune homeostasis(7-9). However, the underlying molecular mechanisms of this neonatal priming period have not been defined. Here we report the identification of a host-mediated regulatory circuit of bacterial colonization that acts solely during the early neonatal period but influences life-long microbiota composition. We demonstrate age-dependent expression of the flagellin receptor Toll-like receptor 5 (TLR5) in the gut epithelium of neonate mice. Using competitive colonization experiments, we demonstrate that epithelial TLR5-mediated REG3 gamma production is critical for the counter-selection of colonizing flagellated bacteria. Comparative microbiota transfer experiments in neonate and adult wild-type and Tlr5-deficient germ-free mice reveal that neonatal TLR5 expression strongly influences the composition of the microbiota throughout life. Thus, the beneficial microbiota in the adult host is shaped during early infancy. This might explain why environmental factors that disturb the establishment of the microbiota during early life can affect immune homeostasis and health in adulthood.
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| 4. |
- Stockinger, S., et al.
(author)
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TRIF Signaling Drives Homeostatic Intestinal Epithelial Antimicrobial Peptide Expression
- 2014
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In: Journal of Immunology. - : The American Association of Immunologists. - 0022-1767 .- 1550-6606. ; 193:8, s. 4223-4234
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Journal article (peer-reviewed)abstract
- Recent results indicate a significant contribution of innate immune signaling to maintain mucosal homeostasis, but the precise underlying signal transduction pathways are ill-defined. By comparative analysis of intestinal epithelial cells isolated from conventionally raised and germ-free mice, as well as animals deficient in the adaptor molecules MyD88 and TRIF, the TLR3 and TLR4, as well as the type I and III IFN receptors, we demonstrate significant TLR-mediated signaling under homeostatic conditions. Surprisingly, homeostatic expression of Reg3 gamma and Paneth cell enteric antimicrobial peptides critically relied on TRIF and, in part, TLR3 but was independent of IFN receptor signaling. Reduced antimicrobial peptide expression was associated with significantly lower numbers of Paneth cells and a reduced Paneth cell maturation and differentiation factor expression in TRIF mutant compared with wild-type epithelium. This phenotype was not transferred to TRIF-sufficient germ-free animals during cohousing. Low antimicrobial peptide expression in TRIF-deficient mice caused reduced immediate killing of orally administered bacteria but was not associated with significant alterations in the overall composition of the enteric microbiota. The phenotype was rapidly restored in a TRIF-independent fashion after transient epithelial damage. Our results identify TRIF signaling as a truly homeostatic pathway to maintain intestinal epithelial barrier function revealing fundamental differences in the innate immune signaling between mucosal homeostasis and tissue repair.
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