Summary
The intestinal epithelium forms a barrier between the microbiota and the rest of the body. In addition, beyond acting as a physical barrier, the function of intestinal epithelial cells (IECs) ...in sensing and responding to microbial signals is increasingly appreciated and likely has numerous implications for the vast network of immune cells within and below the intestinal epithelium. IECs also respond to factors produced by immune cells, and these can regulate IEC barrier function, proliferation and differentiation, as well as influence the composition of the microbiota. The mechanisms involved in IEC–microbe–immune interactions, however, are not fully characterized. In this review, we explore the ability of IECs to direct intestinal homeostasis by orchestrating communication between intestinal microbes and mucosal innate and adaptive immune cells during physiological and inflammatory conditions. We focus primarily on the most recent findings and call attention to the numerous remaining unknowns regarding the complex crosstalk between IECs, the microbiota and intestinal immune cells.
Beyond acting as a physical barrier, the function of intestinal epithelial cells (IECs) in sensing and responding to microbial signals is increasingly appreciated and likely has numerous implications for the vast network of immune cells within and below the intestinal epithelium. In this review, we explore the ability of IECs to direct intestinal homeostasis by orchestrating communication between intestinal microbes and mucosal innate and adaptive immune cells during physiological and inflammatory conditions. We focus primarily on the most recent findings and call attention to the numerous remaining unknowns regarding the complex crosstalk between IECs, the microbiota and intestinal immune cells.
Streptococcus pyogenes, the Group A Streptococcus (GAS), is the most common cause of bacterial pharyngitis in children and adults. Innate and adaptive host immune responses are fundamental for ...defense against streptococcal pharyngitis and are central to the clinical manifestation of disease. Host immune responses also contribute to the severe poststreptococcal immune diseases that constitute the major disease burden for this organism. However, until recently, little was known about the host responses elicited during infection. Cellular mediators of innate immunity used during host defense against GAS include epithelial cells, neutrophils, macrophages, and dendritic cells (DCs), which are reported to secrete a number of soluble inflammatory mediators, such as antimicrobial peptides (AMPs); eicosanoids, including PGE2 and leukotriene B4 (LTB4); chemokines; and proinflammatory cytokines. Th1 and Th17 responses play significant roles in adaptive immunity in both murine models of GAS pharyngitis and in human tonsil tissue. A number of inflammatory complications are associated with GAS pharyngitis, which can lead to chronic disease in patients. These include scarlet fever, tonsillar hypertrophy, and sleep apnea, as well as postinfectious sequelae, such as acute rheumatic fever (ARF), poststreptococcal glomerulonephritis, and guttate psoriasis (GP). This review aims to present the current state of knowledge on innate and adaptive immune responses elicited during GAS pharyngitis, mechanisms by which GAS evades these responses, the emerging role of the pharyngeal microbiota, and how the interplay among these factors can influence the outcome of infection and inflammation‐related complications.
Human health and disease have increasingly been shown to be impacted by the gut microbiota, and mouse models are essential for investigating these effects. However, the compositions of human and ...mouse gut microbiotas are distinct, limiting translation of microbiota research between these hosts. To address this, we constructed the Mouse Gastrointestinal Bacteria Catalogue (MGBC), a repository of 26,640 high-quality mouse microbiota-derived bacterial genomes. This catalog enables species-level analyses for mapping functions of interest and identifying functionally equivalent taxa between the microbiotas of humans and mice. We have complemented this with a publicly deposited collection of 223 bacterial isolates, including 62 previously uncultured species, to facilitate experimental investigation of individual commensal bacteria functions in vitro and in vivo. Together, these resources provide the ability to identify and test functionally equivalent members of the host-specific gut microbiotas of humans and mice and support the informed use of mouse models in human microbiota research.
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•MGBC allows functional translation between human and mouse microbiotas•Previously uncultured isolates expand culture collection of mouse gut microbes•Bioinformatic toolkit maps taxonomic locations of microbial functions of interest
Beresford-Jones et al. find that while less than 3% of bacterial species are shared between human and mouse gut microbiotas, they can identify the closest functionally related species between these host-specific microbiotas using the bacterial genome catalog they developed. This will facilitate translation of microbiota-related research between humans and mice.
The World Health Organization reports that antibiotic-resistant pathogens represent an imminent global health disaster for the 21st century. Gram-positive superbugs threaten to breach last-line ...antibiotic treatment, and the pharmaceutical industry antibiotic development pipeline is waning. Here we report the synergy between ionophore-induced physiological stress in Gram-positive bacteria and antibiotic treatment. PBT2 is a safe-for-human-use zinc ionophore that has progressed to phase 2 clinical trials for Alzheimer's and Huntington's disease treatment. In combination with zinc, PBT2 exhibits antibacterial activity and disrupts cellular homeostasis in erythromycin-resistant group A
(GAS), methicillin-resistant
(MRSA), and vancomycin-resistant
(VRE). We were unable to select for mutants resistant to PBT2-zinc treatment. While ineffective alone against resistant bacteria, several clinically relevant antibiotics act synergistically with PBT2-zinc to enhance killing of these Gram-positive pathogens. These data represent a new paradigm whereby disruption of bacterial metal homeostasis reverses antibiotic-resistant phenotypes in a number of priority human bacterial pathogens.
The rise of bacterial antibiotic resistance coupled with a reduction in new antibiotic development has placed significant burdens on global health care. Resistant bacterial pathogens such as methicillin-resistant
and vancomycin-resistant
are leading causes of community- and hospital-acquired infection and present a significant clinical challenge. These pathogens have acquired resistance to broad classes of antimicrobials. Furthermore,
, a significant disease agent among Indigenous Australians, has now acquired resistance to several antibiotic classes. With a rise in antibiotic resistance and reduction in new antibiotic discovery, it is imperative to investigate alternative therapeutic regimens that complement the use of current antibiotic treatment strategies. As stated by the WHO Director-General, "On current trends, common diseases may become untreatable. Doctors facing patients will have to say, Sorry, there is nothing I can do for you."
Experimental mouse models are central to basic biomedical research; however, variability exists across genetically identical mice and mouse facilities making comparisons difficult. Whether specific ...indigenous gut bacteria drive immunophenotypic variability in mouse models of human disease remains poorly understood. We performed a large-scale experiment using 579 genetically identical laboratory mice from a single animal facility, designed to identify the causes of disease variability in the widely used dextran sulphate sodium mouse model of inflammatory bowel disease. Commonly used treatment endpoint measures-weight loss and intestinal pathology-showed limited correlation and varied across mouse lineages. Analysis of the gut microbiome, coupled with machine learning and targeted anaerobic culturing, identified and isolated two previously undescribed species, Duncaniella muricolitica and Alistipes okayasuensis, and demonstrated that they exert dominant effects in the dextran sulphate sodium model leading to variable treatment endpoint measures. We show that the identified gut microbial species are common, but not ubiquitous, in mouse facilities around the world, and suggest that researchers monitor for these species to provide experimental design opportunities for improved mouse models of human intestinal diseases.
(Group A
; GAS) commonly causes pharyngitis in children and adults, with severe invasive disease and immune sequelae being an infrequent consequence. The ability of GAS to invade the host and ...establish infection likely involves subversion of host immune defenses. However, the signaling pathways and innate immune responses of epithelial cells to GAS are not well-understood. In this study, we utilized RNAseq to characterize the inflammatory responses of primary human tonsil epithelial (TEpi) cells to infection with the laboratory-adapted M6 strain JRS4 and the M1T1 clinical isolate 5448. Both strains induced the expression of genes encoding a wide range of inflammatory mediators, including IL-8. Pathway analysis revealed differentially expressed genes between mock and JRS4- or 5448-infected TEpi cells were enriched in transcription factor networks that regulate IL-8 expression, such as AP-1, ATF-2, and NFAT. While JRS4 infection resulted in high levels of secreted IL-8, 5448 infection did not, suggesting that 5448 may post-transcriptionally dampen IL-8 production. Infection with 5448Δ
, an isogenic mutant lacking the IL-8 protease SpyCEP, resulted in IL-8 secretion levels comparable to JRS4 infection. Complementation of 5448Δ
and JRS4 with a plasmid encoding 5448-derived SpyCEP significantly reduced IL-8 secretion by TEpi cells. Our results suggest that intracellular infection with the pathogenic GAS M1T1 clone induces a strong pro-inflammatory response in primary tonsil epithelial cells, but modulates this host response by selectively degrading the neutrophil-recruiting chemokine IL-8 to benefit infection.
Highlights • Vaccines protect against several important human bacterial pathogens. • Bacterial vaccine escape mutants limit coverage and effectiveness. • Improvements in design may improve future ...vaccines.
Multiplex quantitative proteomics analysis of mice infected with Group A Streptococcus reveals organ-specific biomarkers of infection.
Multiplex quantitative proteomics analysis of mice infected with ...Group A Streptococcus reveals organ-specific biomarkers of infection.
Abstract
Peripheral CD4+CD8αα+TCRαβ+ intraepithelial lymphocytes (pIELs) are a specialised T cell population that require the presence of intestinal microbes for their development, however the ...microbes and factors involved are not well characterised. pIELs are closely associated with intestinal epithelial cells (IECs) that line the gastrointestinal tract, but the contribution of IECs in shaping pIEL development is also not well defined. We investigated a number of microbial metabolites for their ability to influence pIEL development, and whether this is mediated by microbe-IEC-pIEL interactions.
In this study we utilised flow cytometry to characterise pIEL frequencies in GF mice administered with different microbial metabolites, in SPF mice from different colonies and animal facilities, and in GF mice monocolonised with potential pIEL-inducing commensal species. qPCR of IEC RNA isolated from these mice was performed to identify candidate genes expressed by IECs that may influence pIEL development.
We identified a common bacterial metabolite that partially restores pIEL development in GF mice, and a novel pIEL-inducing bacterial species. pIEL frequency of SPF mice varied between different sources, and qPCR identified IECs expressed several T-cell-influencing cytokines that correlated with pIEL frequency in vivo.
Our results identify a common microbial metabolite that contributes to pIEL development that may mediate IEC expression of T-cell-influencing cytokines. Our work further elucidates the mechanisms of host tolerance triggered by commensal microbes, which will facilitate the development of better strategies to prevent and treat intestinal infections and inflammatory diseases.
Abstract
Peripheral CD4+CD8αα+TCRαβ+ intraepithelial lymphocytes (pIELs) are a specialised T cell population that are reduced in germ-free (GF) C57BL/6 mice and vary in frequency between SPF mice ...from different sources, indicating their development is dependent on the presence of intestinal microbes. The microbes and factors required for pIEL development, however, are not fully characterised. pIELs are closely associated with intestinal epithelial cells (IECs) that line the gastrointestinal tract, however the contribution of IECs in shaping pIEL development is not well defined. We investigated if microbial metabolites influence pIEL development, and whether this is mediated by microbe-IEC-pIEL interactions.
In this study we used flow cytometry to characterise pIEL frequencies in GF mice administered different microbial metabolites, and in SPF mice from different colonies and animal facilities. qPCR of IEC RNA isolated from these mice and of metabolite-treated enteroids and MODE-K cells was performed to identify candidate genes expressed by IECs that may influence pIEL development.
We identified a common bacterial metabolite that partially restores pIEL development in GF mice. pIEL frequency of SPF mice varied between different sources, and qPCR identified IEC expression of several T-cell-influencing cytokines that correlated with pIEL frequency in vivo.
Our results indicate that a common microbial metabolite contributes to pIEL development, corresponding to metabolite-induced IEC expression of T-cell-influencing cytokines. Our work further elucidates the mechanisms of commensal microbe modulation of host tolerance, which may enable better strategies to prevent and treat intestinal infections and inflammation.
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