Intestinal microbes affect phenotypes and functions of invariant natural killer T cells in mice

Invariant natural killer T (iNKT) cells undergo canonical, Vα14-Jα18 rearrangement of the T-cell receptor (TCR) in mice; this form of the TCR recognizes glycolipids presented by CD1d. iNKT cells mediate many different immune reactions. Their constitutive activated and memory phenotype and rapid initiation of effector functions after stimulation indicate previous antigen-specific stimulation. However, little is known about this process. We investigated whether symbiotic microbes can determine the activated phenotype and function of iNKT cells.

A survey on intestinal parasites of livestock guardian dogs and herding dogs in Switzerland

The present study describes the occurrence of intestinal parasite infections in livestock guardian dogs and herding dogs. A total of 71 guardian dogs (more than half of the total number of guardian dogs in Switzerland) and 21 herding dogs were coprologically examined, using a combined sedimentation-flotation method. In 21 (23 %) of the dogs intestinal parasites were detected, and 8 (8.7 %) of these dogs shed either sporocysts of Sarcocystis sp. (n = 6) or taeniid eggs (n = 2). The evaluation of questionnaires providing data on age, origin and deworming schemes of the dogs completed the study.

Defining new criteria for selection of cell-based intestinal models using publicly available databases

The criteria for choosing relevant cell lines among a vast panel of available intestinal-derived lines exhibiting a wide range of functional properties are still ill-defined. The objective of this study was, therefore, to establish objective criteria for choosing relevant cell lines to assess their appropriateness as tumor models as well as for drug absorption studies.

Metabolomic markers for intestinal ischemia in a mouse model

Diagnosis of intestinal ischemia remains a clinical challenge. The aim of the present study was to use a metabolomic protocol to identify upregulated and downregulated small molecules (M(r) < 500) in the serum of mice with intestinal ischemia. Such molecules could have clinical utility when evaluated as biomarkers in human studies.

Functional flexibility of intestinal IgA - broadening the fine line

Intestinal bacteria outnumber our own human cells in conditions of both health and disease. It has long been recognized that secretory antibody, particularly IgA, is produced in response to these microbes and hypothesized that this must play an important role in defining the relationship between a host and its intestinal microbes. However, the exact role of IgA and the mechanisms by which IgA can act are only beginning to be understood. In this review we attempt to unravel the complex interaction between so-called "natural," "primitive" (T-cell-independent), and "classical" IgA responses, the nature of the intestinal microbiota/intestinal pathogens and the highly flexible dynamic homeostasis of the mucosal immune system. Such an analysis reveals that low-affinity IgA is sufficient to protect the host from excess mucosal immune activation induced by harmless commensal microbes. However, affinity-maturation of "classical" IgA is essential to provide protection from more invasive commensal species such as segmented filamentous bacteria and from true pathogens such as Salmonellatyphimurium. Thus a correlation is revealed between "sophistication" of the IgA response and aggressiveness of the challenge. A second emerging theme is that more-invasive species take advantage of host inflammatory mechanisms to more successfully compete with the resident microbiota. In many cases, the function of IgA may be to limit such inflammatory responses, either directly by coagulating or inhibiting virulence of bacteria before they can interact with the host or by modulating immune signaling induced by host recognition. Therefore IgA appears to provide an added layer of robustness in the intestinal ecosystem, promoting "commensal-like" behavior of its residents.

Generation and analysis of a mouse intestinal metatranscriptome through Illumina based RNA-sequencing

With the advent of high through-put sequencing (HTS), the emerging science of metagenomics is transforming our understanding of the relationships of microbial communities with their environments. While metagenomics aims to catalogue the genes present in a sample through assessing which genes are actively expressed, metatranscriptomics can provide a mechanistic understanding of community inter-relationships. To achieve these goals, several challenges need to be addressed from sample preparation to sequence processing, statistical analysis and functional annotation. Here we use an inbred non-obese diabetic (NOD) mouse model in which germ-free animals were colonized with a defined mixture of eight commensal bacteria, to explore methods of RNA extraction and to develop a pipeline for the generation and analysis of metatranscriptomic data. Applying the Illumina HTS platform, we sequenced 12 NOD cecal samples prepared using multiple RNA-extraction protocols. The absence of a complete set of reference genomes necessitated a peptide-based search strategy. Up to 16% of sequence reads could be matched to a known bacterial gene. Phylogenetic analysis of the mapped ORFs revealed a distribution consistent with ribosomal RNA, the majority from Bacteroides or Clostridium species. To place these HTS data within a systems context, we mapped the relative abundance of corresponding Escherichia coli homologs onto metabolic and protein-protein interaction networks. These maps identified bacterial processes with components that were well-represented in the datasets. In summary this study highlights the potential of exploiting the economy of HTS platforms for metatranscriptomics.

Intestinal bacterial translocation in rats with cirrhosis is related to compromised Paneth cell antimicrobial host defense

Liver cirrhosis is associated with bacterial translocation (BT) and endotoxemia. Most translocating bacteria belong to the common intestinal microbiota, suggesting a breakdown of intestinal barrier function. We hypothesized that diminished mucosal antimicrobial host defense could predispose to BT. Two rodent models of portal hypertension with increased BT were used, CCl(4)-induced ascitic cirrhosis and 2-day portal vein-ligated (PVL) animals. BT was assessed by standard microbiological techniques on mesenteric lymph nodes. Total RNA was isolated systematically throughout the intestinal tract, and expression of Paneth cell α-cryptdins and β-defensins was determined by real-time quantitative polymerase chain reaction (qPCR). To determine functional consequences, mucosal antimicrobial activity was assessed with a fluorescence-activated cell sorting assay. BT was detectable in 40% of rats with cirrhosis. Compared with the group without BT, these animals exhibited diminished intestinal Paneth cell α-cryptdin 5 and 7 expression. In contrast, PVL was associated with BT in all animals but did not affect antimicrobial peptides. The decrease in Paneth cell antimicrobials was most pronounced in the ileum and the coecum. Other antimicrobials showed no changes or even an induction in the case of BT at different sites. Antimicrobial activity toward different commensal strains was reduced, especially in the distal ileum and the cecum in experimental cirrhosis with BT (excluding PVL). Conclusion: Compromised Paneth cell antimicrobial host defense seems to predispose to BT in experimental cirrhosis. Understanding this liver-gut axis including the underlying mechanisms could help us to find new treatment avenues.

Commensal and probiotic bacteria influence intestinal barrier function and susceptibility to colitis in Nod1-/-; Nod2-/- mice

The intestinal microbiota regulates key host functions. It is unknown whether modulation of the microbiota can affect a genetically determined host phenotype. Polymorphisms in the Nucleotide oligomerization domain (Nod)-like receptor family confer genetic risk for inflammatory bowel disease (IBD). We investigated whether the intestinal microbiota and the probiotic strain Bifidobacterium breve NCC2950 affect intestinal barrier function and responses to intestinal injury in Nod1(-/-); Nod2(-/-) mice.