Dysregulation of T cell receptor N-glycosylation: a molecular mechanism involved in ulcerative colitis.

The incidence of inflammatory bowel disease is increasing worldwide and the underlying molecular mechanisms are far from being fully elucidated. Herein, we evaluated the role of N-glycosylation dysregulation in T cells as a key mechanism in the ulcerative colitis (UC) pathogenesis. The evaluation of the branched N-glycosylation levels and profile of intestinal T cell receptor (TCR) were assessed in colonic biopsies from UC patients and healthy controls. Expression alterations of the glycosyltransferase gene MGAT5 were also evaluated. We demonstrated that UC patients exhibit a dysregulation of TCR branched N-glycosylation on lamina propria T lymphocytes. Patients with severe UC showed the most pronounced defect on N-glycan branching in T cells. Moreover, UC patients showed a significant reduction of MGAT5 gene transcription in T lymphocytes. In this study, we disclose for the first time that a deficiency in branched N-glycosylation on TCR due to a reduced MGAT5 gene expression is a new molecular mechanism underlying UC pathogenesis, being a potential novel biomarker with promising clinical and therapeutic applications.

Stereological assessment of sexual dimorphism in the rat liver reveals differences in hepatocytes and Kupffer cells but not hepatic stellate cells.

There is long-standing evidence that male and female rat livers differ in enzyme activity. More recently, differences in gene expression profiling have also been found to exist; however, it is still unclear whether there is morphological expression of male/female differences in the normal liver. Such differences could help to explain features seen at the pathological level, such as the greater regenerative potential generally attributed to the female liver. In this paper, hepatocytes (HEP), Kupffer cells (KC) and hepatic stellate cells (HSC) of male and female rats were examined to investigate hypothesised differences in number, volume and spatial co-localisation of these cell types. Immunohistochemistry and design-based stereology were used to estimate total numbers, numbers per gram and mean cell volumes. The position of HSC within lobules (periportal vs. centrilobular) and their spatial proximity to KC was also assessed. In addition, flow cytometry was used to investigate the liver ploidy. In the case of HEP and KC, differences in the measured cell parameters were observed between male and female specimens; however, no such differences were detected for HSC. Female samples contained a higher number of HEP per gram, with more binucleate cells. The HEP nuclei were smaller in females, which was coincident with more abundant diploid particles in these animals. The female liver also had a greater number of KC per gram, with a lower percentage of KC in the vicinity of HSC compared with males. In this study, we document hitherto unknown morphological sexual dimorphism in the rat liver, namely in HEP and KC. These differences may account for the higher regenerative potential of the female liver and lend weight to the argument for considering the rat liver as a sexually dimorphic organ.

Effect of commercial starter cultures on volatile compound profile and sensory characteristics of dry-cured foal sausage.

BACKGROUND: The present work deals with the evaluation of the effect of three different commercial starter cultures (Chr. Hansen, Hørsholm, Denmark) on the volatile compound profile and sensory properties, as well as some important physicochemical parameters, of dry-fermented foal sausages at the end of ripening in order to select the most suitable starter culture for this elaboration. The sausage batches were named as follows: CO (non-inoculated control), FS (Lactobacillus sakei + Staphylococcus carnosus), SM (L. sakei + S. carnosus + Staphylococcus xylosus + Pediococcus pentosaceus + Debaryomyces hansenii) and TR (L. sakei + S. carnosus +S. xylosus). RESULTS: The pH values differed significantly among batches, with the highest values corresponding to CO followed by TR, SM and FS. The highest amounts of volatile compounds were found in FS batch. Hexanal was the most abundant compound, especially in FS and SM batches. These batches also showed higher levels of compounds derived from carbohydrate fermentation and amino acid catabolism. Sensory results showed that acid taste was significantly lower in CO batch than in inoculated batches. CONCLUSION: According to most parameters, batches inoculated with FS and SM starters showed marked acidity compared with TR and CO batches, as expected from the manufacturer's indications. Therefore the most suitable starter culture for use in the manufacture of foal sausages in Mediterranean countries such as Spain with a preference for low-acidity products was found to be TR culture.

Volatile compounds of Celta dry-cured 'lacón' as affected by cross-breeding with Duroc and Landrace genotypes.

BACKGROUND: Dry-cured 'lacón' is a traditional cured meat product made in the north-west of Spain from the pigs' foreleg, with similar manufacturing process to that used in dry-cured ham. The aim of this study was to assess the influence of cross-breeding of Celta pig with Landrace or Duroc breeds on the formation of volatile compounds through the manufacture of 'lacón'. RESULTS: 'Lacón' from the crosses with Duroc presented lower final moisture (534 g kg(-1) ) and higher intra-muscular fat content [144 g kg(-1) dry matter (DM)] than 'lacón' from Celta pure breed (587 g kg(-1) and 36 g kg(-1) DM, respectively). Volatile compounds were extracted by solid-phase microextraction and analysed by gas chromatography-mass spectrometry. Volatile compounds from 'lacón' were affected by cross-breeding. The total amount of volatile compounds significantly (P < 0.001) increased during the manufacturing process, this increase being more marked in samples from the Landrace cross-breed. The most abundant group of flavour compounds at the end of the manufacturing process was esters in the three batches, followed by aldehydes, hydrocarbons and alcohols. The most abundant ester at the end of the process was hexanoic acid methyl ester, while the aldehyde found in a higher amount was hexanal. CONCLUSIONS: The profile of volatile compounds was affected by cross-breed, especially at the end of the 'lacón' dry-curing process.

Implications of literacy for health for body mass index.

INTRODUCTION: Literacy for health (LH) may be considered a set of skills that people appropriate, understand, evaluate and use information and knowledge of health to make informed choices, reduce risks to their health, maintain a healthy nutritional status and enhance quality of life. OBJECTIVES: To assess the level of literacy for health; analyse the relationship of socio-demographic variables with LH; to classify the Body Mass Index (BMI) and to determine the effect of LH on BMI. DESIGN: a quantitative study with a descriptive and cross-sectional approach conducted in the centre and north of Portugal. Particnipants: a non-probabilistic sample of 508 Portuguese participants with a mean age 44.48 years (SD = 21 years). MEASURING INSTRUMENTS: LH was assessed by the European Questionnaire on Literacy for Health (LHS-EU-PT) validated in Portuguese by Saboga-Nunes and Sorensen (2013) and BMI classification followed the WHO reference accepted by Portugal, DGS (2013). RESULTS: It was found that overall, 73.62% of the participants have an inappropriate and problematic level of literacy for health; this was significantly lower in women (P=.000). Participants with inadequate LH, are those with higher BMI (χ(2)=78.09; P=.000), so are at risk of a sub-optimal state of health. CONCLUSIONS: The results suggest a significant relationship between the LH and BMI. It is found that, the better the LH, the more appropriate is the BMI. This evidence reinforces the importance of promoting literacy for health to the Portuguese population.

Technological and safety characteristics of Staphylococcaceae isolated from Spanish traditional dry-cured sausages.

The aim of this study was to determine the technological properties (nitrate reductase, proteolytic and lipolytic activities; and the ability to grow at the temperature and pH values of fermenting sausage, and at high NaCl concentrations) and safety characteristics (amino acid decarboxylase and enterotoxigenic activities) of 38 strains of Staphylococcaceae (11 of Staphylococcus epidermidis, 15 of Staphylococcus equorum, 5 of Staphylococcus pasteuri and 7 of Staphylococcus saprophyticus) isolated from Androlla and Botillo, two Spanish traditional sausages, in order to evaluate their suitability as potential starter cultures in the manufacture of these sausages. Most strains were able to grow at 10 °C, in the presence of 10% and 15% NaCl and at pH values of 5.5 and 5.0, except for S. equorum strains, growth of which was reduced at these pH values. The proteolytic activity assessed by the agar plate method showed that 89.5% and 52.6% of the strains were able to hydrolyze sarcoplasmic and myofibrillar proteins, respectively. These results were not confirmed by electrophoretic assays as only 47.2% of the strains changed the SDS-PAGE profile of actin, myosin and/or sarcoplasmic protein extracts. The assessment of the lipolytic activity by titration showed that only 21.0% of the strains can hydrolyze pork fat to any extent; whereas the profiles of the freed fatty acids were different in the different strains. Most of the strains showed decarboxylase activity against histidine, lysine, ornithine and tyrosine, but the quantities of biogenic amines produced were in most cases <25 ppm and <5 ppm for putrescine and cadaverine, respectively. Only four strains (10.5%), of S. epidermidis, produced enterotoxin C.

Use of molecular methods to characterize the bacterial community and to monitor different native starter cultures throughout the ripening of Galician chorizo.

The development of Lactobacillus and Staphylococcus strains used as starter cultures throughout the ripening of Galician chorizo, a traditional dry fermented sausage from the north-west of Spain, was monitored combining different molecular-based techniques. The bacterial diversity occurring in the inoculated sausages at the beginning and the end of the ripening was also studied and compared to the indigenous population in an uninoculated control batch. Real-time PCR was used to monitor the Lactobacillus and Staphylococcus community using genus and species-specific primer to quantify the occurring microbiota. The identification of isolates at genus or species level was achieved by specific PCR and 16S rRNA gene sequencing. rep-PCR using (GTG)5-PCR primer was used to characterize this bacterial community at strain level. According to the data obtained, the strains Lactobacillus sakei LS131, Staphylococcus equorum SA25 and Staphylococcus saprophyticus SB12 were dominant during the ripening process, whereas the strain Staphylococcus epidermidis SA49, that was added in order to study its behaviour with a merely scientific purpose, did not succeed in dominating ripening, since it seemed to be outcompeted by autochthonous microbiota. In conclusion, the combination of a quantitative method such as real-time PCR with the identification and typing techniques used in this study (genus and species-specific PCR, 16S rRNA gene sequencing and (GTG)5-PCR) provided accurate and complete information about the starter cultures development, assessing their growth and survival over the ripening process.

Monitoring the bacterial population dynamics during the ripening of Galician chorizo, a traditional dry fermented Spanish sausage.

The dynamics of the bacterial population throughout the ripening of Galician chorizo, a traditional dry fermented sausage produced in the north-west of Spain, were investigated by using classical and molecular approaches. Fermented sausages are certainly complex matrices with PCR inhibitors and background microbiota. Therefore, two different DNA preparation methods were performed to elaborate each standard curve and no significant differences were found, showing a very good correlation between both methods (R(2)>0.994). The combination of the results obtained from microbial counts, species and genus-specific PCR as well as real-time quantitative PCR (qPCR) allowed the identification for the dominant bacterial species and the study of the variation in the community composition over the ripening period. According to the data obtained both by identification of plate isolates and by real-time PCR, the dominant species among staphylococci and lactobacilli were Staphylococcus equorum and Lactobacillus sakei, respectively. However, only real-time PCR assay showed enough sensitivity to detect and quantify staphylococci in meat batter before stuffing, showing values of 5.28logCFU/g when quantifying Staphylococcus spp. and 2.87logCFU/g when quantifying S. equorum. In conclusion, real-time PCR was shown to be an efficient tool for the study of the complex associations developed in meat fermentations and for the characterization of dominant populations.

Corrigendum: Extracellular vesicles produced by the human gut commensal bacterium Bacteroides thetaiotaomicron elicit anti-inflammatory responses from innate immune cells.

[This corrects the article DOI: 10.3389/fmicb.2022.1050271.].

[Clinical research X. Usefulness of an organic mesh in the repair of abdominal defects]. / Reparación del defecto herniario. Empleo de malla de material orgánico.

OBJECTIVE: to measure the compliance, security and usefulness of organic mesh (bovine pericardium) in the repair of abdominal defect in an animal model. METHODS: Wistar rats (weight 300 to 500 g), were anesthetized and an abdominal defect of 1 cm in each animal was performed. Animals were divided according to the repair material used: bovine pericardium mesh (n = 6) and polipropilene mesh (n = 6). Animals were sacrificed on day 28 after the surgery. Presence of infection, necrosis and adherences (macroscopic and microscopic) were compared. Tensile force was also measured in both groups. RESULTS: inflammation, necrosis and adherences were similar in both groups. The prolene mesh (mean rupture force 66.5 joules) was stronger than bovine pericardium (mean rupture force 47.4 joules) p = 0.002, however, had also more adherences. CONCLUSIONS: there is no difference between inflammation, necrosis and adherences. But the polipropilene mesh was stronger than the bovine pericardium mesh. This finding could have relevance in the clinical practice (hernia recurrence).

Extracellular vesicles produced by the human commensal gut bacterium Bacteroides thetaiotaomicron affect host immune pathways in a cell-type specific manner that are altered in inflammatory bowel disease.

The gastrointestinal (GI) tract harbours a complex microbial community, which contributes to its homeostasis. A disrupted microbiome can cause GI-related diseases, including inflammatory bowel disease (IBD), therefore identifying host-microbe interactions is crucial for better understanding gut health. Bacterial extracellular vesicles (BEVs), released into the gut lumen, can cross the mucus layer and access underlying immune cells. To study BEV-host interactions, we examined the influence of BEVs generated by the gut commensal bacterium, Bacteroides thetaiotaomicron, on host immune cells. Single-cell RNA sequencing data and host-microbe protein-protein interaction networks were used to predict the effect of BEVs on dendritic cells, macrophages and monocytes focusing on the Toll-like receptor (TLR) pathway. We identified biological processes affected in each immune cell type and cell-type specific processes including myeloid cell differentiation. TLR pathway analysis highlighted that BEV targets differ among cells and between the same cells in healthy versus disease (ulcerative colitis) conditions. The in silico findings were validated in BEV-monocyte co-cultures demonstrating the requirement for TLR4 and Toll-interleukin-1 receptor domain-containing adaptor protein (TIRAP) in BEV-elicited NF-kB activation. This study demonstrates that both cell-type and health status influence BEV-host communication. The results and the pipeline could facilitate BEV-based therapies for the treatment of IBD.

Extracellular vesicles produced by the human gut commensal bacterium Bacteroides thetaiotaomicron elicit anti-inflammatory responses from innate immune cells.

Bacterial extracellular vesicles (BEVs) produced by gut commensal bacteria have been proposed to play an important role in maintaining host homeostasis via interactions with the immune system. Details of the mediators and pathways of BEV-immune cell interactions are however incomplete. In this study, we provide evidence for the anti-inflammatory and immunomodulatory properties of extracellular vesicles produced by the prominent human gut commensal bacterium Bacteroides thetaiotaomicron (Bt BEVs) and identify the molecular mechanisms underlying their interaction with innate immune cells. Administration of Bt BEVs to mice treated with colitis-inducing dextran sodium sulfate (DSS) ameliorates the symptoms of intestinal inflammation, improving survival rate and reducing weight loss and disease activity index scores, in association with upregulation of IL-10 production in colonic tissue and in splenocytes. Pre-treatment (conditioning) of murine bone marrow derived monocytes (BMDM) with Bt BEVs resulted in higher ratio of IL-10/TNFα production after an LPS challenge when compared to LPS pre-conditioned or non-conditioned BMDM. Using the THP-1 monocytic cell line the interactions between Bt BEVs and monocytes/macrophages were shown to be mediated primarily by TLR2. Histone (H3K4me1) methylation analysis showed that Bt BEVs induced epigenetic reprogramming which persisted after infectious challenge, as revealed by increased levels of H3K4me1 in Bt BEV-conditioned LPS-challenged BMDM. Collectively, our findings highlight the important role of Bt BEVs in maintaining host immune homeostasis and raise the promising possibility of considering their use in immune therapies.

IL-31 and IL-8 in Cutaneous T-Cell Lymphoma: Looking for Their Role in Itch.

The itch associated with cutaneous T-cell lymphoma (CTCL), including Mycosis Fungoides (MF) and Sézary syndrome (SS), is often severe and poorly responsive to treatment with antihistamines. Recent studies have highlighted the possible role of interleukins in nonhistaminergic itch. We investigated the role of IL-31 and IL-8 in CTCL, concerning disease severity and associated itch. Serum samples of 27 patients with CTCL (17 MF and 10 SS) and 29 controls (blood donors) were analyzed for interleukin- (IL-) 31 and IL-8; correlations with disease and itch severity were evaluated. IL-31 serum levels were higher in CTCL patients than in controls and higher in SS than in MF. Also, serum IL-31 levels were higher in patients with advanced disease compared to those with early disease, and they correlated positively with lactate dehydrogenase and beta 2-microglobulin levels, as well as with the Sézary cell count. Itch affected 67% of CTCL patients (MF: 47%; SS: 100%). Serum IL-31 levels were higher in itching patients than in controls and in patients without itching. There was no association between serum IL-8 and disease severity, nor with itching. Serum IL-8 levels correlated positively with peripheral blood leukocyte and neutrophil counts in CTCL patients. Our study suggests a role for IL-31 in CTCL-associated itch, especially in advanced disease and SS, offering a rational target for new therapeutic approaches. Increased serum IL-8 observed in some patients may be related to concomitant infections, and its role in exacerbating itch by recruiting neutrophils and promoting the release of neutrophil proteases deserves further investigation.

Regulation of blood-brain barrier integrity by microbiome-associated methylamines and cognition by trimethylamine N-oxide.

BACKGROUND: Communication between the gut microbiota and the brain is primarily mediated via soluble microbe-derived metabolites, but the details of this pathway remain poorly defined. Methylamines produced by microbial metabolism of dietary choline and L-carnitine have received attention due to their proposed association with vascular disease, but their effects upon the cerebrovascular circulation have hitherto not been studied. RESULTS: Here, we use an integrated in vitro/in vivo approach to show that physiologically relevant concentrations of the dietary methylamine trimethylamine N-oxide (TMAO) enhanced blood-brain barrier (BBB) integrity and protected it from inflammatory insult, acting through the tight junction regulator annexin A1. In contrast, the TMAO precursor trimethylamine (TMA) impaired BBB function and disrupted tight junction integrity. Moreover, we show that long-term exposure to TMAO protects murine cognitive function from inflammatory challenge, acting to limit astrocyte and microglial reactivity in a brain region-specific manner. CONCLUSION: Our findings demonstrate the mechanisms through which microbiome-associated methylamines directly interact with the mammalian BBB, with consequences for cerebrovascular and cognitive function. Video abstract.

Gut microbes and metabolites as modulators of blood-brain barrier integrity and brain health.

The human gastrointestinal (gut) microbiota comprises diverse and dynamic populations of bacteria, archaea, viruses, fungi, and protozoa, coexisting in a mutualistic relationship with the host. When intestinal homeostasis is perturbed, the function of the gastrointestinal tract and other organ systems, including the brain, can be compromised. The gut microbiota is proposed to contribute to blood-brain barrier disruption and the pathogenesis of neurodegenerative diseases. While progress is being made, a better understanding of interactions between gut microbes and host cells, and the impact these have on signaling from gut to brain is now required. In this review, we summarise current evidence of the impact gut microbes and their metabolites have on blood-brain barrier integrity and brain function, and the communication networks between the gastrointestinal tract and brain, which they may modulate. We also discuss the potential of microbiota modulation strategies as therapeutic tools for promoting and restoring brain health.

Biochemical Changes during the Manufacture of Galician Chorizo Sausage as Affected by the Addition of Autochthonous Starter Cultures.

In this work, the effect of the use of two autochthonous starter cultures (Lactobacillus sakei LS131 + Staphylococcus equorum SA25 (EQU), or L. sakei LS131 + Staphylococcus saprophyticus SB12 (SAP)) on the physicochemical, microbiological, proteolytic and lipolytic changes taking place during the manufacture of Galician chorizo, a traditional Spanish sausage, was studied. Three different batches (control (CNT), EQU and SAP) were manufactured in triplicate and analysed during the manufacturing process (samples were taken and analysed at 0, 2, 5, 9, 14, 21 and 30 days of ripening) for proximate composition, pH, aw, colour parameters, nitrogen fractions, free amino acids, biogenic amines, fat parameters and free fatty acids. The use of either of these two starter cultures slightly but significantly reduced the pH values during the fermentation and increased the percentage of transformation to nitrosyl-heme pigments as well as the a* and b* values in the final products. The two starters significantly decreased the Enterobacteriaceae counts in the final product, but without this microbial group completely disappearing. Both starter cultures significantly increased the α-amino acidic nitrogen and the total basic volatile nitrogen fractions during manufacturing, also increasing the free amino acid content and reducing the total biogenic amine content by approximately 20%. The SAP starter enhanced the lipolytic processes, increasing the free fatty acid content. Due to their performances, these two starter cultures seem to be suitable for increasing the quality and safety of the Galician chorizo sausage.

Human Peripheral Blood Gamma Delta T Cells: Report on a Series of Healthy Caucasian Portuguese Adults and Comprehensive Review of the Literature.

Gamma delta T cells (Tc) are divided according to the type of Vδ and Vγ chains they express, with two major γδ Tc subsets being recognized in humans: Vδ2Vγ9 and Vδ1. Despite many studies in pathological conditions, only a few have quantified the γδ Tc subsets in healthy adults, and a comprehensive review of the factors influencing its representation in the blood is missing. Here we quantified the total γδ Tc and the Vδ2/Vγ9 and Vδ1 Tc subsets in the blood from 30 healthy, Caucasian, Portuguese adults, we characterized their immunophenotype by 8-color flow cytometry, focusing in a few relevant Tc markers (CD3/TCR-γδ, CD5, CD8), and costimulatory (CD28), cytotoxic (CD16) and adhesion (CD56) molecules, and we examined the impacts of age and gender. Additionally, we reviewed the literature on the influences of race/ethnicity, age, gender, special periods of life, past infections, diet, medications and concomitant diseases on γδ Tc and their subsets. Given the multitude of factors influencing the γδ Tc repertoire and immunophenotype and the high variation observed, caution should be taken in interpreting "abnormal" γδ Tc values and repertoire deviations, and the clinical significance of small populations of "phenotypically abnormal" γδ Tc in the blood.

The Uptake, Trafficking, and Biodistribution of Bacteroides thetaiotaomicron Generated Outer Membrane Vesicles.

Gram-negative bacteria ubiquitously produce and release nano-size, non-replicative outer membrane vesicles (OMVs). In the gastrointestinal (GI-) tract, OMVs generated by members of the intestinal microbiota are believed to contribute to maintaining the intestinal microbial ecosystem and mediating bacteria-host interactions, including the delivery of bacterial effector molecules to host cells to modulate their physiology. Bacterial OMVs have also been found in the bloodstream although their origin and fate are unclear. Here we have investigated the interactions between OMVs produced by the major human gut commensal bacterium, Bacteroides thetaiotaomicron (Bt), with cells of the GI-tract. Using a combination of in vitro culture systems including intestinal epithelial organoids and in vivo imaging we show that intestinal epithelial cells principally acquire Bt OMVs via dynamin-dependent endocytosis followed by intracellular trafficking to LAMP-1 expressing endo-lysosomal vesicles and co-localization with the perinuclear membrane. We observed that Bt OMVs can also transmigrate through epithelial cells via a paracellular route with in vivo imaging demonstrating that within hours of oral administration Bt OMVs can be detected in systemic tissues and in particular, the liver. Our findings raise the intriguing possibility that OMVs may act as a long-distance microbiota-host communication system.

Chemokine receptor repertoire reflects mature T-cell lymphoproliferative disorder clinical presentation.

The World Health Organization classification of mature T-cell lymphoproliferative disorders, combines clinical, morphological and immunophenotypic data. The latter is a major contributor to the classification, as well as to the understanding of the malignant T-cell behavior. The fact that T-cell migration is regulated by chemokines should, in theory, enable us to identify tissue tropism and organ involvement by neoplastic T-cells by monitoring chemokine receptor surface expression. To address this issue we compared the expression of several early and late inflammatory, homeostatic, and organ specific chemokine receptors on blood T-cells from normal individuals and patients with T-cell large granular lymphocytic leukemia and peripheral T-cell lymphoma. T-cell large granular lymphocytic leukemia cells mainly express late inflammatory chemokine receptors (CXCR1 and CXCR2), whereas peripheral T-cell lymphoma cells usually express one or more organ homing receptors (CCR4, CCR6 and CCR7). Nevertheless, no clear correlation was found between CCR4 and CCR7 expression and skin and lymph node involvement, respectively. Compared to their normal counterparts, lymphoma T-cells displayed an exaggerated CCR4 expression, whereas leukemic T-cells had abnormally high CXCR1 and CXCR2 expression. Further analysis revealed that, in leukemia patients, the percentage of neoplastic cells expressing CCR5 correlates directly with lymphocytosis. In addition, in the case of CD8 T-cell leukemia patients, an inverse correlation with neutropenia was found. In lymphoma patients, higher CCR4 and CCR7 expression is accompanied by lower to absent CCR5 expression.

Bioengineering commensal bacteria-derived outer membrane vesicles for delivery of biologics to the gastrointestinal and respiratory tract.

Gram-negative bacteria naturally produce and secrete nanosized outer membrane vesicles (OMVs). In the human gastrointestinal tract, OMVs produced by commensal Gram-negative bacteria can mediate interactions amongst host cells (including between epithelial cells and immune cells) and maintain microbial homeostasis. This OMV-mediated pathway for host-microbe interactions could be exploited to deliver biologically active proteins to the body. To test this we engineered the Gram-negative bacterium Bacteroides thetaiotaomicron (Bt), a prominent member of the intestinal microbiota of all animals, to incorporate bacteria-, virus- and human-derived proteins into its OMVs. We then used the engineered Bt OMVs to deliver these proteins to the respiratory and gastrointestinal (GI)-tract to protect against infection, tissue inflammation and injury. Our findings demonstrate the ability to express and package both Salmonella enterica ser. Typhimurium-derived vaccine antigens and influenza A virus (IAV)-derived vaccine antigens within or on the outer membrane of Bt OMVs. These antigens were in a form capable of eliciting antigen-specific immune and antibody responses in both mucosal tissues and systemically. Furthermore, immunisation with OMVs containing the core stalk region of the IAV H5 hemagglutinin from an H5N1 strain induced heterotypic protection in mice to a 10-fold lethal dose of an unrelated subtype (H1N1) of IAV. We also showed that OMVs could express the human therapeutic protein, keratinocyte growth factor-2 (KGF-2), in a stable form that, when delivered orally, reduced disease severity and promoted intestinal epithelial repair and recovery in animals administered colitis-inducing dextran sodium sulfate. Collectively, our data demonstrates the utility and effectiveness of using Bt OMVs as a mucosal biologics and drug delivery platform technology.