Dissecting the Interplay Between Intestinal Microbiota and Host Immunity in Health and Disease: Lessons Learned from Germfree and Gnotobiotic Animal Models

Recent advancements in targeting the immune system to treat hypertension

Hypertension is the key leading risk factor for death globally, affecting ∼1.3 billion adults, particularly in low- and middle-income countries. Most people living with hypertension have uncontrolled high blood pressure, increasing their likelihood of cardiovascular events. Significant issues preventing blood pressure control include lack of diagnosis, treatment, and response to existing therapy. For example, monotherapy and combination therapy are often unable to lower blood pressure to target levels. New therapies are urgently required to tackle this issue, particularly those that target the mechanisms behind hypertension instead of treating its symptoms. Acting via an increase in systemic and tissue-specific inflammation, the immune system is a critical contributor to blood pressure regulation and is considered an early mechanism leading to hypertension development. Here, we review the immune system's role in hypertension, evaluate clinical trials that target inflammation, and discuss knowledge gaps in pre-clinical and clinical data. We examine the effects of anti-inflammatory drugs colchicine and methotrexate on hypertension and evaluate the blockade of pro-inflammatory cytokines IL-1β and TNF-α on blood pressure in clinical trials. Lastly, we highlight how we can move forward to target specific components of the immune system to lower blood pressure. This includes targeting isolevuglandins, which accumulate in dendritic cells to promote T cell activation and cytokine production in salt-induced hypertension. We discuss the potential of the dietary fibre-derived metabolites short-chain fatty acids, which have anti-inflammatory and blood pressure-lowering effects via the gut microbiome. This would limit adverse events, leading to improved medication adherence and better blood pressure control.

A systematic framework for understanding the microbiome in human health and disease: from basic principles to clinical translation

The human microbiome is a complex and dynamic system that plays important roles in human health and disease. However, there remain limitations and theoretical gaps in our current understanding of the intricate relationship between microbes and humans. In this narrative review, we integrate the knowledge and insights from various fields, including anatomy, physiology, immunology, histology, genetics, and evolution, to propose a systematic framework. It introduces key concepts such as the 'innate and adaptive genomes', which enhance genetic and evolutionary comprehension of the human genome. The 'germ-free syndrome' challenges the traditional 'microbes as pathogens' view, advocating for the necessity of microbes for health. The 'slave tissue' concept underscores the symbiotic intricacies between human tissues and their microbial counterparts, highlighting the dynamic health implications of microbial interactions. 'Acquired microbial immunity' positions the microbiome as an adjunct to human immune systems, providing a rationale for probiotic therapies and prudent antibiotic use. The 'homeostatic reprogramming hypothesis' integrates the microbiome into the internal environment theory, potentially explaining the change in homeostatic indicators post-industrialization. The 'cell-microbe co-ecology model' elucidates the symbiotic regulation affecting cellular balance, while the 'meta-host model' broadens the host definition to include symbiotic microbes. The 'health-illness conversion model' encapsulates the innate and adaptive genomes' interplay and dysbiosis patterns. The aim here is to provide a more focused and coherent understanding of microbiome and highlight future research avenues that could lead to a more effective and efficient healthcare system.

Antimicrobial use in laboratory rodent facilities in Australia and New Zealand- a cross-sectional survey of veterinarians and facility managers

This cross-sectional study surveyed veterinarians and facility managers to characterise the use of antimicrobials in laboratory rodent facilities within Australia and New Zealand. Most facilities (71%) reported routine administration of antimicrobials. The indications for antibiotic use reflected those described in publications and differed significantly to reasons for use in non-laboratory animals. Antimicrobials used include those of critical importance to human health, and access to these drugs is unregulated, as prescription-only classes are ordered through research catalogues, without human or veterinary physician prescriptions. The ways in which antimicrobials are used in Australian and New Zealand rodent facilities are likely contributing to antimicrobial resistance within rodent populations, particularly as they are largely administered in drinking water, risking subtherapeutic dosing. Much antimicrobial use reported is unnecessary and could be replaced with changes to husbandry and handling. The generation of resistance in both pathogenic and commensal microbes may also represent a work health and safety issue for humans working with these animals. Reported disposal of antimicrobials included discharge into wastewater, without inactivation, and some respondents reported disposal of substrate, or soiled bedding, nesting material, and disposable enrichment items, from treated animals and medicated feed into landfill, without prior inactivation. Environmental contamination with resistant microbes and antimicrobials is a significant driver of antimicrobial resistance. As such, significant opportunities exist to implement judicious and responsible use of antimicrobials within research rodent facilities in Australia and New Zealand, with a particular focus on instituting aseptic surgery, optimising dosing regimens, and inactivation of medicated water and substrate before disposal.

Microbial influences on severity and sex bias of systemic autoimmunity

Commensal microbes have the capacity to affect development and severity of autoimmune diseases. Germ-free (GF) animals have proven to be a fine tool to obtain definitive answers to the queries about the microbial role in these diseases. Moreover, GF and gnotobiotic animals can be used to dissect the complex symptoms and determine which are regulated (enhanced or attenuated) by microbes. These include disease manifestations that are sex biased. Here, we review comparative analyses conducted between GF and Specific-Pathogen Free (SPF) mouse models of autoimmunity. We present data from the B6;NZM-Sle1NZM2410/AegSle2NZM2410/AegSle3NZM2410/Aeg-/LmoJ (B6.NZM) mouse model of systemic lupus erythematosus (SLE) characterized by multiple measurable features. We compared the severity and sex bias of SPF, GF, and ex-GF mice and found variability in the severity and sex bias of some manifestations. Colonization of GF mice with the microbiotas taken from B6.NZM mice housed in two independent institutions variably affected severity and sexual dimorphism of different parameters. Thus, microbes regulate both the severity and sexual dimorphism of select SLE traits. The sensitivity of particular trait to microbial influence can be used to further dissect the mechanisms driving the disease. Our results demonstrate the complexity of the problem and open avenues for further investigations.

The gut-lung axis: the impact of the gut mycobiome on pulmonary diseases and infections

The gastrointestinal tract contains a diverse microbiome consisting of bacteria, fungi, viruses and archaea. Although these microbes usually reside as commensal organisms, it is now well established that higher abundance of specific bacterial or fungal species, or loss of diversity in the microbiome can significantly affect development, progression and outcomes in disease. Studies have mainly focused on the effects of bacteria, however, the impact of other microbes, such as fungi, has received increased attention in the last few years. Fungi only represent around 0.1% of the total gut microbial population. However, key fungal taxa such as Candida, Aspergillus and Wallemia have been shown to significantly impact health and disease. The composition of the gut mycobiome has been shown to affect immunity at distal sites, such as the heart, lung, brain, pancreas, and liver. In the case of the lung this phenomenon is referred to as the 'gut-lung axis'. Recent studies have begun to explore and unveil the relationship between gut fungi and lung immunity in diseases such as asthma and lung cancer, and lung infections caused by viruses, bacteria and fungi. In this review we will summarize the current, rapidly growing, literature describing the impact of the gut mycobiome on respiratory disease and infection.

Oral curcumin ameliorates acute murine campylobacteriosis

Introduction

Human infections with the food-borne enteropathogen Campylobacter jejuni are responsible for increasing incidences of acute campylobacteriosis cases worldwide. Since antibiotic treatment is usually not indicated and the severity of the enteritis directly correlates with the risk of developing serious autoimmune disease later-on, novel antibiotics-independent intervention strategies with non-toxic compounds to ameliorate and even prevent campylobacteriosis are utmost wanted. Given its known pleiotropic health-promoting properties, curcumin constitutes such a promising candidate molecule. In our actual preclinical placebo-controlled intervention trial, we tested the anti-microbial and anti-inflammatory effects of oral curcumin pretreatment during acute experimental campylobacteriosis.

Methods

Therefore, secondary abiotic IL-10-/- mice were challenged with synthetic curcumin via the drinking water starting a week prior oral C. jejuni infection. To assess anti-pathogenic, clinical, immune-modulatory, and functional effects of curcumin prophylaxis, gastrointestinal C. jejuni bacteria were cultured, clinical signs and colonic histopathological changes quantitated, pro-inflammatory immune cell responses determined by in situ immunohistochemistry and intestinal, extra-intestinal and systemic pro-inflammatory mediator measurements, and finally, intestinal epithelial barrier function tested by electrophysiological resistance analysis of colonic ex vivo biopsies in the Ussing chamber.

Results and discussion

Whereas placebo counterparts were suffering from severe enterocolitis characterized by wasting symptoms and bloody diarrhea on day 6 post-infection, curcumin pretreated mice, however, were clinically far less compromised and displayed less severe microscopic inflammatory sequelae such as histopathological changes and epithelial cell apoptosis in the colon. In addition, curcumin pretreatment could mitigate pro-inflammatory innate and adaptive immune responses in the intestinal tract and importantly, rescue colonic epithelial barrier integrity upon C. jejuni infection. Remarkably, the disease-mitigating effects of exogenous curcumin was also observed in organs beyond the infected intestines and strikingly, even systemically given basal hepatic, renal, and serum concentrations of pro-inflammatory mediators measured in curcumin pretreated mice on day 6 post-infection. In conclusion, the anti-Campylobacter and disease-mitigating including anti-inflammatory effects upon oral curcumin application observed here highlight the polyphenolic compound as a promising antibiotics-independent option for the prevention from severe acute campylobacteriosis and its potential post-infectious complications.

Interwoven processes in fish development: microbial community succession and immune maturation

Fishes are hosts for many microorganisms that provide them with beneficial effects on growth, immune system development, nutrition and protection against pathogens. In order to avoid spreading of infectious diseases in aquaculture, prevention includes vaccinations and routine disinfection of eggs and equipment, while curative treatments consist in the administration of antibiotics. Vaccination processes can stress the fish and require substantial farmer's investment. Additionally, disinfection and antibiotics are not specific, and while they may be effective in the short term, they have major drawbacks in the long term. Indeed, they eliminate beneficial bacteria which are useful for the host and promote the raising of antibiotic resistance in beneficial, commensal but also in pathogenic bacterial strains. Numerous publications highlight the importance that plays the diversified microbial community colonizing fish (i.e., microbiota) in the development, health and ultimately survival of their host. This review targets the current knowledge on the bidirectional communication between the microbiota and the fish immune system during fish development. It explores the extent of this mutualistic relationship: on one hand, the effect that microbes exert on the immune system ontogeny of fishes, and on the other hand, the impact of critical steps in immune system development on the microbial recruitment and succession throughout their life. We will first describe the immune system and its ontogeny and gene expression steps in the immune system development of fishes. Secondly, the plurality of the microbiotas (depending on host organism, organ, and development stage) will be reviewed. Then, a description of the constant interactions between microbiota and immune system throughout the fish's life stages will be discussed. Healthy microbiotas allow immune system maturation and modulation of inflammation, both of which contribute to immune homeostasis. Thus, immune equilibrium is closely linked to microbiota stability and to the stages of microbial community succession during the host development. We will provide examples from several fish species and describe more extensively the mechanisms occurring in zebrafish model because immune system ontogeny is much more finely described for this species, thanks to the many existing zebrafish mutants which allow more precise investigations. We will conclude on how the conceptual framework associated to the research on the immune system will benefit from considering the relations between microbiota and immune system maturation. More precisely, the development of active tolerance of the microbiota from the earliest stages of life enables the sustainable establishment of a complex healthy microbial community in the adult host. Establishing a balanced host-microbiota interaction avoids triggering deleterious inflammation, and maintains immunological and microbiological homeostasis.

A guide to germ-free and gnotobiotic mouse technology to study health and disease

The intestinal microbiota has major influence on human physiology and modulates health and disease. Complex host-microbe interactions regulate various homeostatic processes, including metabolism and immune function, while disturbances in microbiota composition (dysbiosis) are associated with a plethora of human diseases and are believed to modulate disease initiation, progression and therapy response. The vast complexity of the human microbiota and its metabolic output represents a great challenge in unraveling the molecular basis of host-microbe interactions in specific physiological contexts. To increase our understanding of these interactions, functional microbiota research using animal models in a reductionistic setting are essential. In the dynamic landscape of gut microbiota research, the use of germ-free and gnotobiotic mouse technology, in which causal disease-driving mechanisms can be dissected, represents a pivotal investigative tool for functional microbiota research in health and disease, in which causal disease-driving mechanisms can be dissected. A better understanding of the health-modulating functions of the microbiota opens perspectives for improved therapies in many diseases. In this review, we discuss practical considerations for the design and execution of germ-free and gnotobiotic experiments, including considerations around germ-free rederivation and housing conditions, route and timing of microbial administration, and dosing protocols. This comprehensive overview aims to provide researchers with valuable insights for improved experimental design in the field of functional microbiota research.

Association of antibiotic treatment with survival outcomes in treatment-naïve melanoma patients receiving immune checkpoint blockade

PURPOSE

The interaction of gut microbiome and immune system is being studied with increasing interest. Disturbing factors, such as antibiotics may impact the immune system via gut and interfere with tumor response to immune checkpoint blockade (ICB).

METHODS

In this multicenter retrospective cohort study exclusively treatment-naïve patients with cutaneous or mucosal melanoma treated with first-line anti-PD-1 based ICB for advanced, non-resectable disease between 06/2013 and 09/2018 were included. Progression-free (PFS), and overall survival (OS) according to antibiotic exposure (within 60 days prior to ICB and after the start of ICB vs. no antibiotic exposure) were analyzed. To account for immortal time bias, data from patients with antibiotics during ICB were analyzed separately in the time periods before and after start of antibiotics.

RESULTS

Among 578 patients with first-line anti-PD1 based ICB, 7% of patients received antibiotics within 60 days prior to ICB and 19% after starting ICB. Antibiotic exposure prior to ICB was associated with worse PFS (adjusted HR 1.75 [95% CI 1.22-2.52]) and OS (adjusted HR 1.64 [95% CI 1.04-2.58]) by multivariate analysis adjusting for potential confounders. The use of antibiotics after the start of ICB had no effect on either PFS (adjusted HR 1.19; 95% CI 0.89-1.60) or OS (adjusted HR 1.08; 95% CI 0.75-1.57).

CONCLUSIONS

Antibiotic exposure within 60 days prior to ICB seems to be associated with worse PFS and OS in melanoma patients receiving first-line anti-PD1 based therapy, whereas antibiotics after the start of ICB do not appear to affect PFS or OS.

Understanding gut microbiome-based machine learning platforms: A review on therapeutic approaches using deep learning

Human beings possess trillions of microbial cells in a symbiotic relationship. This relationship benefits both partners for a long time. The gut microbiota helps in many bodily functions from harvesting energy from digested food to strengthening biochemical barriers of the gut and intestine. But the changes in microbiota composition and bacteria that can enter the gastrointestinal tract can cause infection. Several approaches like culture-independent techniques such as high-throughput and meta-omics projects targeting 16S ribosomal RNA (rRNA) sequencing are popular methods to investigate the composition of the human gastrointestinal tract microbiota and taxonomically characterizing microbial communities. The microbiota conformation and diversity should be provided by whole-genome shotgun metagenomic sequencing of site-specific community DNA associating genome mapping, gene inventory, and metabolic remodelling and reformation, to ease the functional study of human microbiota. Preliminary examination of the therapeutic potency for dysbiosis-associated diseases permits investigation of pharmacokinetic-pharmacodynamic changes in microbial communities for escalation of treatment and dosage plan. Gut microbiome study is an integration of metagenomics which has influenced the field in the last two decades. And the incorporation of artificial intelligence and deep learning through "omics-based" methods and microfluidic evaluation enhanced the capability of identification of thousands of microbes.

What we need to know about the germ-free animal models

The gut microbiota (GM), as a forgotten organ, refers to the microbial community that resides in the gastrointestinal tract and plays a critical role in a variety of physiological activities in different body organs. The GM affects its targets through neurological, metabolic, immune, and endocrine pathways. The GM is a dynamic system for which exogenous and endogenous factors have negative or positive effects on its density and composition. Since the mid-twentieth century, laboratory animals are known as the major tools for preclinical research; however, each model has its own limitations. So far, two main models have been used to explore the effects of the GM under normal and abnormal conditions: the isolated germ-free and antibiotic-treated models. Both methods have strengths and weaknesses. In many fields of host-microbe interactions, research on these animal models are known as appropriate experimental subjects that enable investigators to directly assess the role of the microbiota on all features of physiology. These animal models present biological model systems to either study outcomes of the absence of microbes, or to verify the effects of colonization with specific and known microbial species. This paper reviews these current approaches and gives advantages and disadvantages of both models.

Association of the Infant Gut Microbiome with Temperament at Nine Months of Age: A Michigan Cohort Study

Though studies in animals and humans link the gut microbiota to brain development and control of behavior, little research has examined this connection in healthy infants. This prospective study could determine associations between infant gut microbiota at 3 months, and infant temperament at 9 months, in a prospective pregnancy cohort (Michigan Archive for Research on Child Health; n = 159). Microbiota profiling with 16S rRNA gene sequencing was conducted on fecal samples obtained at 3 months of age. Based on the relative abundance of gut microbiotas, three groups were identified, and each group was characterized by different microbes. Infant temperament outcomes were reported by mothers using the Infant Behavior Questionnaire-Revised Very Short Form at a mean age of 9.4 months. Fully adjusted multivariate linear regression models showed that certain clusters were associated with higher negative emotionality scores, prominently among infants who had poor vitamin D intake. However, no associations were evident between gut microbiota clusters and temperament scales after FDR correction. After using three differential abundance tools, Firmicutes was associated with higher positive affect/surgency scores, whereas Clostridioides was associated with lower scores. An association between the gut microbiota and early infancy temperament was observed; thus, this study warrants replication, with a particular focus on vitamin D moderation.

Lactobacillus from the Altered Schaedler Flora maintain IFNγ homeostasis to promote behavioral stress resilience

The gut microbiome consists of trillions of bacteria, fungi, and viruses that inhabit the digestive tract. These communities are sensitive to disruption from environmental exposures ranging from diet changes to illness. Disruption of the community of lactic acid producing bacteria, Lactobaccillacea, has been well documented in mood disorders and stress exposure. In fact, oral supplement with many Lactobacillus species can ameliorate these effects, preventing depression- and anxiety-like behavior. Here, we utilize a gnotobiotic mouse colonized with the Altered Schaedler Flora to remove the two native species of Lactobaccillacea: L. intestinalis and L. murinus. Using this microbial community, we found that the Lactobacillus species themselves, and not the disrupted microbial communities are protective from environmental stressors. Further, we determine that Lactobaccillacea are maintaining homeostatic IFNγ levels which are mediating these behavioral and circuit level responses. By utilizing the Altered Schaedler Flora, we have gained new insight into how probiotics influence behavior and provide novel methods to study potential therapies to treat mood disorders.

Engraftment of aging-related human gut microbiota and the effect of a seven-species consortium in a pre-clinical model

Human aging is characterized by gut microbiome alteration and differential loss of gut commensal species associated with the onset of frailty. The administration of cultured commensal strains to replenish lost taxa could potentially promote healthy aging. To investigate the interaction of whole microbiomes and administered strains, we transplanted gut microbiota from a frail or healthy elderly subject into germ-free mice. We supplemented the frail-donor recipient group with a defined consortium of taxa (the "S7") that we identified by analyzing healthy aging subjects in our previous studies and whose abundance correlated with health-promoting dietary intervention. Inoculation with a frail or a healthy donor microbiome resulted in differential microbiota compositions in murine recipients 5 weeks post-transplantation. Fecal acetate levels were significantly higher in healthy donor recipient mice than in frail donor recipient mice after 4 weeks. However, the frailty-related phenotype was not replicated in recipient mice with single-dose microbiota transplantation from a healthy and a frail donor. Five S7 species colonized successfully in germ-free mice, with a relatively high abundance of Barnesiella intestinihominis and Eubacterium rectale. The engraftment of five S7 species in germ-free mice increased fecal acetate levels and reduced colon permeability and plasma TNF-ɑ concentration. Supplementation with the S7 in frail-microbiota recipient mice did not increase alpha-diversity but significantly increased the abundance of Barnesiella intestinihominis. S7 supplementation showed the potential for improving spatial reference memory in frail-microbiota recipient mice. Collectively, these data highlight the challenge of elderly microbiota engraftment in the germ-free mouse model but show promise for modulating the gut microbiome of frail elderly subjects by administering an artificial gut microbe consortium associated with healthy aging.

Vaccination with an HIV T-Cell Immunogen (HTI) Using DNA Primes Followed by a ChAdOx1-MVA Boost Is Immunogenic in Gut Microbiota-Depleted Mice despite Low IL-22 Serum Levels

Despite the important role of gut microbiota in the maturation of the immune system, little is known about its impact on the development of T-cell responses to vaccination. Here, we immunized C57BL/6 mice with a prime-boost regimen using DNA plasmid, the Chimpanzee Adenovirus, and the modified Vaccinia Ankara virus expressing a candidate HIV T-cell immunogen and compared the T-cell responses between individuals with an intact or antibiotic-depleted microbiota. Overall, the depletion of the gut microbiota did not result in significant differences in the magnitude or breadth of the immunogen-specific IFNγ T-cell response after vaccination. However, we observed marked changes in the serum levels of four cytokines after vaccinating microbiota-depleted animals, particularly a significant reduction in IL-22 levels. Interestingly, the level of IL-22 in serum correlated with the abundance of Roseburia in the large intestine of mice in the mock and vaccinated groups with intact microbiota. This short-chain fatty acid (SCFA)-producing bacterium was significantly reduced in the vaccinated, microbiota-depleted group. Therefore, our results indicate that, although microbiota depletion reduces serum levels of IL-22, the powerful vaccine regime used could have overcome the impact of microbiota depletion on IFNγ-producing T-cell responses.

Reducing gut microbiome-driven adipose tissue inflammation alleviates metabolic syndrome

BACKGROUND

The gut microbiota contributes to macrophage-mediated inflammation in adipose tissue with consumption of an obesogenic diet, thus driving the development of metabolic syndrome. There is a need to identify and develop interventions that abrogate this condition. The hops-derived prenylated flavonoid xanthohumol (XN) and its semi-synthetic derivative tetrahydroxanthohumol (TXN) attenuate high-fat diet-induced obesity, hepatosteatosis, and metabolic syndrome in C57Bl/6J mice. This coincides with a decrease in pro-inflammatory gene expression in the gut and adipose tissue, together with alterations in the gut microbiota and bile acid composition.

RESULTS

In this study, we integrated and interrogated multi-omics data from different organs with fecal 16S rRNA sequences and systemic metabolic phenotypic data using a Transkingdom Network Analysis. By incorporating cell type information from single-cell RNA-seq data, we discovered TXN attenuates macrophage inflammatory processes in adipose tissue. TXN treatment also reduced levels of inflammation-inducing microbes, such as Oscillibacter valericigenes, that lead to adverse metabolic phenotypes. Furthermore, in vitro validation in macrophage cell lines and in vivo mouse supplementation showed addition of O. valericigenes supernatant induced the expression of metabolic macrophage signature genes that are downregulated by TXN in vivo.

CONCLUSIONS

Our findings establish an important mechanism by which TXN mitigates adverse phenotypic outcomes of diet-induced obesity and metabolic syndrome. TXN primarily reduces the abundance of pro-inflammatory gut microbes that can otherwise promote macrophage-associated inflammation in white adipose tissue. Video Abstract.

Lactobacillus maintains IFNγ homeostasis to promote behavioral stress resilience

The gut microbiome consists of the trillions of bacteria, fungi, and viruses that inhabit the digestive tract. These communities are sensitive to disruption from environmental exposures ranging from diet changes to illness. Disruption of the community of lactic acid producing bacteria, Lactobaccillacea , has been well documented in mood disorders and stress exposure. In fact, oral supplement with many Lactobacillus species can ameliorate these effects, preventing depression- and anxiety-like behavior. Here, for the first time, we utilize a gnotobiotic mouse colonized with the Altered Schaedler Flora to remove the two native species of Lactobaccillacea . Using this novel microbial community, we found that the Lactobacillus species themselves, and not the disrupted microbial communities are protective from environmental stressors. Further, we determine that Lactobaccillacea are maintaining homeostatic IFNγ levels which are mediating these behavioral and circuit level responses. By utilizing the Altered Schaedler Flora, we have gained new insight into how probiotics influence behavior and give novel methods to study potential therapies developed to treat mood disorders.

The role of probiotics as wound healers: an overall view

A wound is an injury to the skin or damage to the body tissue. The healing process differs between various kinds of wounds. Treatment of hard-to-heal (chronic) wounds becomes challenging for healthcare practitioners, especially if patients have underlying health complications such as diabetes. Infection of wounds is another factor that interferes with the healing process and extends its duration. Active research is being conducted into the development of advanced wound dressing technologies. These wound dressings are intended to manage the exudate, reduce bacterial infection and speed up the healing process. Probiotics have been receiving much attention because of their potential application in the clinical field, especially in diagnostics and treatment strategies of various infectious and non-infectious diseases. The host immune-modulatory response and antimicrobial activity of probiotics are expanding their role in the development of improved wound dressing technology.

The microbiome of the marine flatworm Macrostomum lignano provides fitness advantages and exhibits circadian rhythmicity

The close association between animals and their associated microbiota is usually beneficial for both partners. Here, we used a simple marine model invertebrate, the flatworm Macrostomum lignano, to characterize the host-microbiota interaction in detail. This analysis revealed that the different developmental stages each harbor a specific microbiota. Studies with gnotobiotic animals clarified the physiological significance of the microbiota. While no fitness benefits were mediated by the microbiota when food was freely available, animals with microbiota showed significantly increased fitness with a reduced food supply. The microbiota of M. lignano shows circadian rhythmicity, affecting both the total bacterial load and the behavior of specific taxa. Moreover, the presence of the worm influences the composition of the bacterial consortia in the environment. In summary, the Macrostomum-microbiota system described here can serve as a general model for host-microbe interactions in marine invertebrates.

Basal Diet Fed to Recipient Mice Was the Driving Factor for Colitis and Colon Tumorigenesis, despite Fecal Microbiota Transfer from Mice with Severe or Mild Disease

Consumption of the total Western diet (TWD) in mice has been shown to increase gut inflammation, promote colon tumorigenesis, and alter fecal microbiome composition when compared to mice fed a healthy diet, i.e., AIN93G (AIN). However, it is unclear whether the gut microbiome contributes directly to colitis-associated CRC in this model. The objective of this study was to determine whether dynamic fecal microbiota transfer (FMT) from donor mice fed either the AIN basal diet or the TWD would alter colitis symptoms or colitis-associated CRC in recipient mice, which were fed either the AIN diet or the TWD, using a 2 × 2 factorial experiment design. Time-matched FMT from the donor mice fed the TWD did not significantly enhance symptoms of colitis, colon epithelial inflammation, mucosal injury, or colon tumor burden in the recipient mice fed the AIN diet. Conversely, FMT from the AIN-fed donors did not impart a protective effect on the recipient mice fed the TWD. Likewise, the composition of fecal microbiomes of the recipient mice was also affected to a much greater extent by the diet they consumed than by the source of FMT. In summary, FMT from the donor mice fed either basal diet with differing colitis or tumor outcomes did not shift colitis symptoms or colon tumorigenesis in the recipient mice, regardless of the basal diet they consumed. These observations suggest that the gut microbiome may not contribute directly to the development of disease in this animal model.

The Role of Microbiota-Derived Vitamins in Immune Homeostasis and Enhancing Cancer Immunotherapy

Not all cancer patients who receive immunotherapy respond positively and emerging evidence suggests that the gut microbiota may be linked to treatment efficacy. Though mechanisms of microbial contributions to the immune response have been postulated, one likely function is the supply of basic co-factors to the host including selected vitamins. Bacteria, fungi, and plants can produce their own vitamins, whereas humans primarily obtain vitamins from exogenous sources, yet despite the significance of microbial-derived vitamins as crucial immune system modulators, the microbiota is an overlooked source of these nutrients in humans. Microbial-derived vitamins are often shared by gut bacteria, stabilizing bioenergetic pathways amongst microbial communities. Compositional changes in gut microbiota can affect metabolic pathways that alter immune function. Similarly, the immune system plays a pivotal role in maintaining the gut microbiota, which parenthetically affects vitamin biosynthesis. Here we elucidate the immune-interactive mechanisms underlying the effects of these microbially derived vitamins and how they can potentially enhance the activity of immunotherapies in cancer.

Therapeutic Oral Application of Carvacrol Alleviates Acute Campylobacteriosis in Mice Harboring a Human Gut Microbiota

Human Campylobacter jejuni infections are rising globally. Since antibiotics are usually not indicated in acute campylobacteriosis, antibiotic-independent intervention measures are desirable. The phenolic compound carvacrol constitutes a promising candidate molecule given its antimicrobial and immune-modulatory features. To test the disease-alleviating effects of oral carvacrol treatment in acute murine campylobacteriosis, IL-10-/- mice harboring a human gut microbiota were perorally infected with C. jejuni and treated with carvacrol via the drinking water. Whereas C. jejuni stably established in the gastrointestinal tract of mice from the placebo cohort, carvacrol treatment resulted in lower pathogen loads in the small intestines on day 6 post infection. When compared to placebo, carvacrol ameliorated pathogen-induced symptoms including bloody diarrhea that was accompanied by less distinct histopathological and apoptotic cell responses in the colon. Furthermore, innate and adaptive immune cell numbers were lower in the colon of carvacrol- versus placebo-treated mice. Notably, carvacrol application dampened C. jejuni-induced secretion of pro-inflammatory mediators in intestinal, extra-intestinal and systemic organs to naive levels and furthermore, resulted in distinct shifts in the fecal microbiota composition. In conclusion, our preclinical placebo-controlled intervention study provides evidence that therapeutic carvacrol application constitutes a promising option to alleviate campylobacteriosis in the infected vertebrate host.

Fasting intervention and its clinical effects on the human host and microbiome

Experimental trials in organisms ranging from yeast to humans have shown that various forms of reducing food intake (caloric restriction) appear to increase both overall and healthy lifespan, delaying the onset of disease and slowing the progression of biomarkers of aging. The gut microbiota is considered one of the key environmental factors strongly contributing to the regulation of host health. Perturbations in the composition and activity of the gut microbiome are thought to be involved in the emergence of multiple diseases. Indeed, many studies investigating gut microbiota have been performed and have shown strong associations between specific microorganisms and metabolic diseases including overweight, obesity, and type 2 diabetes mellitus as well as specific gastrointestinal disorders, neurodegenerative diseases, and even cancer. Dietary interventions known to reduce inflammation and improve metabolic health are potentiated by prior fasting. Inversely, birth weight differential host oxidative phosphorylation response to fasting implies epigenetic control of some of its effector pathways. There is substantial evidence for the efficacy of fasting in improving insulin signaling and blood glucose control, and in reducing inflammation, conditions for which, additionally, the gut microbiota has been identified as a site of both risk and protective factors. Accordingly, human gut microbiota, both in symbiont and pathobiont roles, have been proposed to impact and mediate some health benefits of fasting and could potentially affect many of these diseases. While results from small-N studies diverge, fasting consistently enriches widely recognized anti-inflammatory gut commensals such as Faecalibacterium and other short-chain fatty acid producers, which likely mediates some of its health effects through immune system and barrier function impact.

Impact of the Host Microbiome on Vaccine Responsiveness: Lessons Learned and Future Perspective

Vaccination shows high variability in the elicited immune responses among individuals and populations for reasons still poorly understood. An increasing number of studies is supporting the evidence that gut microbiota, along with other interplaying variables, is able to modulate both humoral and cellular responses to infection and vaccination. Importantly, vaccine immunogenicity is often suboptimal at the extremes of age and also in low- and middle-income countries (LMICs), where the microbiota is believed to have an important role on immune responses. Still, contrasting findings and lack of causal evidence are calling for sophisticated methodologies to be able to overcome scientific and technical challenges to better decipher the immunomodulatory role of microbiota. In this perspective, we briefly review the status of the vaccine field in relation to the microbiome and offer possible scientific approaches to better understand the impact of the host microbiome on vaccine responsiveness.

Gut microbial response to host metabolic phenotypes

A large number of studies have proved that biological metabolic phenotypes exist objectively and are gradually recognized by humans. Gut microbes affect the host's metabolic phenotype. They directly or indirectly participate in host metabolism, physiology and immunity through changes in population structure, metabolite differences, signal transduction and gene expression. Obtaining comprehensive information and specific identification factors associated with gut microbiota and host metabolic phenotypes has become the focus of research in the field of gut microbes, and it has become possible to find new and effective ways to prevent or treat host metabolic diseases. In the future, precise treatment of gut microbes will become one of the new therapeutic strategies. This article reviews the content of gut microbes and carbohydrate, amino acid, lipid and nucleic acid metabolic phenotypes, including metabolic intermediates, mechanisms of action, latest research findings and treatment strategies, which will help to understand the relationship between gut microbes and host metabolic phenotypes and the current research status.

Sex hormones, intestinal inflammation, and the gut microbiome: Major influencers of the sexual dimorphisms in obesity

Obesity is defined as the excessive accumulation of body fat and is associated with an increased risk of developing major health problems such as cardiovascular disease, diabetes and stroke. There are clear sexual dimorphisms in the epidemiology, pathophysiology and sequelae of obesity and its accompanying metabolic disorders, with females often better protected compared to males. This protection has predominantly been attributed to the female sex hormone estrogen and differences in fat distribution. More recently, the sexual dimorphisms of obesity have also been attributed to the differences in the composition and function of the gut microbiota, and the intestinal immune system. This review will comprehensively summarize the pre-clinical and clinical evidence for these sexual dimorphisms and discuss the interplay between sex hormones, intestinal inflammation and the gut microbiome in obesity. Major gaps and limitations of this rapidly growing area of research will also be highlighted in this review.

Campylobacter jejuni infection induces acute enterocolitis in IL-10-/- mice pretreated with ampicillin plus sulbactam

Gut microbiota depletion is a pivotal prerequisite to warrant Campylobacter jejuni infection and induced inflammation in IL-10-/- mice used as acute campylobacteriosis model. We here assessed the impact of an 8-week antibiotic regimen of ampicillin, ciprofloxacin, imipenem, metronidazole, and vancomycin (ABx) as compared to ampicillin plus sulbactam (A/S) on gut microbiota depletion and immunopathological responses upon oral C. jejuni infection. Our obtained results revealed that both antibiotic regimens were comparably effective in depleting the murine gut microbiota facilitating similar pathogenic colonization alongside the gastrointestinal tract following oral infection. Irrespective of the preceding microbiota depletion regimen, mice were similarly compromised by acute C. jejuni induced enterocolitis as indicated by comparable clinical scores and macroscopic as well as microscopic sequelae such as colonic histopathology and apoptosis on day 6 post-infection. Furthermore, innate and adaptive immune cell responses in the large intestines were similar in both infected cohorts, which also held true for intestinal, extra-intestinal and even systemic secretion of pro-inflammatory cytokines such as TNF-α, IFN-γ, and IL-6. In conclusion, gut microbiota depletion in IL-10-/- mice by ampicillin plus sulbactam is sufficient to investigate both, C. jejuni infection and the immunopathological features of acute campylobacteriosis.

Effects of Sublethally Injured Campylobacter jejuni in Mice

Globally, Campylobacter spp. are the most common food-associated bacterial cause of human gastrointestinal disease. Campylobacteriosis is primarily associated with the consumption of contaminated chicken meat. Chemical decontamination of chicken carcasses during processing is one of the most effective interventions to mitigate Campylobacter contamination. Following exposure to sanitizers, however, sublethally injured populations of bacteria may persist. The risk that sublethally injured Campylobacter pose for public health is unknown. Furthermore, the virulence potential of sublethally injured Campylobacter jejuni during prolonged storage in relation to host pathogenesis and the host immune response has not been well established. Therefore, we evaluated the effects of sublethally injured C. jejuni on the host, after storage in chicken meat juice. C57BL/6 mice were infected with two C. jejuni chicken meat isolates or the ATCC 33291 strain that had been stored in the chicken meat juice, after exposure to chlorine or acidified sodium chlorite (ASC). Although chlorine exposure was unable to reduce intestinal colonization by C. jejuni, exposure to ASC significantly reduced the intestinal colonization and tissue translocation in mice. The expression of pro- and anti-inflammatory cytokine genes for interleukin-6 (IL-6), IL23a, and IL-10, Toll-like receptor 2 (TLR2) and TLR4 genes, and host stress response genes (CRP, MBL1, and NF-κB1) were significantly reduced following the exposure to ASC. Our results demonstrated that sublethally injured C. jejuni has reduced virulence potential and colonization in mice. The data contribute toward clarification of the importance of chemical decontamination during processing to minimize human campylobacteriosis.

IMPORTANCECampylobacter is the most common cause of bacterial gastrointestinal disease, and consumption of contaminated poultry is frequently identified as the source of bacteria. The survivability and virulence potential of sublethally injured Campylobacter following exposure to chemicals which are commonly used to eliminate Campylobacter during the poultry meat processing are of concern to the food industry, government health officials, and consumers. Here, we demonstrate that sublethally injured Campylobacter jejuni has reduced bacterial virulence and colonization potential in mice.

The gut microbiome and the immune system

The human body contains trillions of microbes which generally live in symbiosis with the host. The interaction of the gut microbiome with elements of the host immune system has far-reaching effects in the development of normal gut and systemic immune responses. Disturbances to this intricate relationship may be responsible for a multitude of gastrointestinal and systemic immune mediated diseases. This review describes the development of the gut microbiome and its interaction with host immune cells in both health and disease states.

Cancer-Associated Microbiota: From Mechanisms of Disease Causation to Microbiota-Centric Anti-Cancer Approaches

Helicobacter pylori infection is the only well-established bacterial cause of cancer. However, due to the integral role of tissue-resident commensals in maintaining tissue-specific immunometabolic homeostasis, accumulated evidence suggests that an imbalance of tissue-resident microbiota that are otherwise considered as commensals, can also promote various types of cancers. Therefore, the present review discusses compelling evidence linking tissue-resident microbiota (especially gut bacteria) with cancer initiation and progression. Experimental evidence supporting the cancer-causing role of gut commensal through the modulation of host-specific processes (e.g., bile acid metabolism, hormonal effects) or by direct DNA damage and toxicity has been discussed. The opportunistic role of commensal through pathoadaptive mutation and overcoming colonization resistance is discussed, and how chronic inflammation triggered by microbiota could be an intermediate in cancer-causing infections has been discussed. Finally, we discuss microbiota-centric strategies, including fecal microbiota transplantation, proven to be beneficial in preventing and treating cancers. Collectively, this review provides a comprehensive understanding of the role of tissue-resident microbiota, their cancer-promoting potentials, and how beneficial bacteria can be used against cancers.

Hyperimmune yolk extract with Immunoglobulin Y basic active principle as a possible adjuvant treatment in patients who need/benefit from neurorehabilitation, with Clostridium difficile (Clostridioides difficile) enterocolitis as intercurrent comorbidity - a systematic literature review

The study aims to add a new and beneficial perspective using Immunoinstant G food supplement as an adjuvant treatment. It is essential to study the bibliographic resources in the field to identify the current stage of knowledge on this topic. For this purpose, we have prepared a systematic literature review, focusing on the possibilities of improving the treatment of Clostridium difficile (Clostridioides difficile) enterocolitis in patients who need/benefit from neurorehabilitation. The systematic literature review was prepared using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). We obtained a number of 6 articles that were considered in the elaboration of our systematic literature review. We identified that this field is insufficiently studied and needs additional clinical trials. Our study contributes to increasing this understanding based on the thorough theoretical and practical approach of this topic.

Microbiota-derived extracellular vesicles in interkingdom communication in the gut

The intestine is fundamental in controlling human health. Intestinal epithelial and immune cells are continuously exposed to millions of microbes that greatly impact on intestinal epithelial barrier and immune function. This microbial community, known as gut microbiota, is now recognized as an important partner of the human being that actively contribute to essential functions of the intestine but also of distal organs. In the gut ecosystem, bidirectional microbiota-host communication does not involve direct cell contacts. Both microbiota and host-derived extracellular vesicles (EVs) are key players of such interkingdom crosstalk. There is now accumulating body of evidence that bacterial secreted vesicles mediate microbiota functions by transporting and delivering into host cells effector molecules that modulate host signalling pathways and cell processes. Consequently, vesicles released by the gut microbiota may have great influence on health and disease. Here we review current knowledge on microbiota EVs and specifically highlight their role in controlling host metabolism, intestinal barrier integrity and immune training.

The genetic impact of an Ebola outbreak on a wild gorilla population

Background

Numerous Ebola virus outbreaks have occurred in Equatorial Africa over the past decades. Besides human fatalities, gorillas and chimpanzees have also succumbed to the fatal virus. The 2004 outbreak at the Odzala-Kokoua National Park (Republic of Congo) alone caused a severe decline in the resident western lowland gorilla (Gorilla gorilla gorilla) population, with a 95% mortality rate. Here, we explore the immediate genetic impact of the Ebola outbreak in the western lowland gorilla population.

Results

Associations with survivorship were evaluated by utilizing DNA obtained from fecal samples from 16 gorilla individuals declared missing after the outbreak (non-survivors) and 15 individuals observed before and after the epidemic (survivors). We used a target enrichment approach to capture the sequences of 123 genes previously associated with immunology and Ebola virus resistance and additionally analyzed the gut microbiome which could influence the survival after an infection. Our results indicate no changes in the population genetic diversity before and after the Ebola outbreak, and no significant differences in microbial community composition between survivors and non-survivors. However, and despite the low power for an association analysis, we do detect six nominally significant missense mutations in four genes that might be candidate variants associated with an increased chance of survival.

Conclusion

This study offers the first insight to the genetics of a wild great ape population before and after an Ebola outbreak using target capture experiments from fecal samples, and presents a list of candidate loci that may have facilitated their survival.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-08025-y.

Contribution of the Commensal Microflora to the Immunological Homeostasis and the Importance of Immune-Related Drug Development for Clinical Applications

Not long ago, self-reactive immune activity was considered as pathological trait. A paradigm shift has now led to the recognition of autoimmune processes as part of natural maintenance of molecular homeostasis. The immune system is assigned further roles beneath the defense against pathogenic organisms. Regarding the humoral immune system, the investigation of natural autoantibodies that are frequently found in healthy individuals has led to further hypotheses involving natural autoimmunity in other processes as the clearing of cellular debris or decrease in inflammatory processes. However, their role and origin have not been entirely clarified, but accumulating evidence links their formation to immune reactions against the gut microbiome. Antibodies targeting highly conserved proteins of the commensal microflora are suggested to show self-reactive properties, following the paradigm of the molecular mimicry. Here, we discuss recent findings, which demonstrate potential links of the commensal microflora to the immunological homeostasis and highlight the possible implications for various diseases. Furthermore, specific components of the immune system, especially antibodies, have become a focus of attention for the medical management of various diseases and provide attractive treatment options in the future. Nevertheless, the development and optimization of such macromolecules still represents a very time-consuming task, shifting the need to more medical agents with simple structural properties and low manufacturing costs. Synthesizing only the biologically active sites of antibodies has become of great interest for the pharmaceutical industry and offers a wide range of therapeutic application areas as it will be discussed in the present review article.

The associations of gut microbiota and fecal short-chain fatty acids with bone mass were largely mediated by weight status: a cross-sectional study

PURPOSE

We aimed to investigate whether the gut microbiota and fecal short-chain fatty acids (SCFAs) are associated with bone mass in healthy children aged 6-9 years.

METHODS

In this study, 236 healthy children including 145 boys and 91 girls were enrolled. 16S rRNA gene sequencing was used to characterize the composition of their gut microbiota. Total and 10 subtypes of SCFAs in the fecal samples were determined by high-performance liquid chromatography. Dual X-ray absorptiometry was used to measure the bone mineral density (BMD) and bone mineral content (BMC) for total body (TB) and total body less head (TBLH). Z score of TBLH BMD was calculated based on the recommended reference.

RESULTS

Four gut microbiota principal components (PCs) were identified by the compositional principal component analysis at the genus level. After adjustment of covariates and controlling for the false discovery rate, multiple linear regression analysis showed that PC3 score (positive loadings on genera Lachnoclostridium and Blautia) was significantly negatively associated with TBLH BMD/BMC/Z score, TB BMC and pelvic BMD (β: - 0.207 to - 0.108, p: 0.002-0.048), whereas fecal total and several subtypes of SCFAs were correlated positively with TBLH BMD/Z score and pelvic BMD (β: 0.118-0.174, p: 0.038-0.048). However, these associations disappeared after additional adjustment for body weight. Mediation analysis suggested that body weight significantly mediated 60.4% and 78.0% of the estimated association of PC3 score and SCFAs with TBLH BMD Z score, respectively.

CONCLUSIONS

The associations of gut microbiota composition and fecal SCFA concentrations with bone mass in children were largely mediated by body weight.

Exploring the Gut-Brain Axis for the Control of CNS Inflammatory Demyelination: Immunomodulation by Bacteroides fragilis' Polysaccharide A

The symbiotic relationship between animals and their resident microorganisms has profound effects on host immunity. The human microbiota comprises bacteria that reside in the gastrointestinal tract and are involved in a range of inflammatory and autoimmune diseases. The gut microbiota's immunomodulatory effects extend to extraintestinal tissues, including the central nervous system (CNS). Specific symbiotic antigens responsible for inducing immunoregulation have been isolated from different bacterial species. Polysaccharide A (PSA) of Bacteroides fragilis is an archetypical molecule for host-microbiota interactions. Studies have shown that PSA has beneficial effects in experimental disease models, including experimental autoimmune encephalomyelitis (EAE), the most widely used animal model for multiple sclerosis (MS). Furthermore, in vitro stimulation with PSA promotes an immunomodulatory phenotype in human T cells isolated from healthy and MS donors. In this review, we discuss the current understanding of the interactions between gut microbiota and the host in the context of CNS inflammatory demyelination, the immunomodulatory roles of gut symbionts. More specifically, we also discuss the immunomodulatory effects of B. fragilis PSA in the gut-brain axis and its therapeutic potential in MS. Elucidation of the molecular mechanisms responsible for the microbiota's impact on host physiology offers tremendous promise for discovering new therapies.

Peroral Clove Essential Oil Treatment Ameliorates Acute Campylobacteriosis-Results from a Preclinical Murine Intervention Study

Campylobacter (C.) jejuni infections pose progressively emerging threats to human health worldwide. Given the rise in antibiotic resistance, antibiotics-independent options are required to fight campylobacteriosis. Since the health-beneficial effects of clove have been known for long, we here analyzed the antimicrobial and immune-modulatory effects of clove essential oil (EO) during acute experimental campylobacteriosis. Therefore, microbiota-depleted interleukin-10 deficient (IL-10^-/-) mice were perorally infected with C. jejuni and treated with clove EO via drinking water starting on day 2 post-infection. On day 6 post-infection, lower small- and large-intestinal pathogen loads could be assessed in clove EO as compared to placebo treated mice. Although placebo mice suffered from severe campylobacteriosis as indicated by wasting and bloody diarrhea, clove EO treatment resulted in a better clinical outcome and in less severe colonic histopathological and apoptotic cell responses in C. jejuni infected mice. Furthermore, lower colonic numbers of macrophages, monocytes, and T lymphocytes were detected in mice from the verum versus the placebo cohort that were accompanied by lower intestinal, extra-intestinal, and even systemic proinflammatory cytokine concentrations. In conclusion, our preclinical intervention study provides first evidence that the natural compound clove EO constitutes a promising antibiotics-independent treatment option of acute campylobacteriosis in humans.

Spontaneous and Induced Tumors in Germ-Free Animals: A General Review

Cancer, bacteria, and immunity relationships are much-debated topics in the last decade. Microbiome’s importance for metabolic and immunologic modulation of the organism adaptation and responses has become progressively evident, and models to study these relationships, especially about carcinogenesis, have acquired primary importance. The availability of germ-free (GF) animals, i.e., animals born and maintained under completely sterile conditions avoiding the microbiome development offers a unique tool to investigate the role that bacteria can have in carcinogenesis and tumor development. The comparison between GF animals with the conventional (CV) counterpart with microbiome can help to evidence conditions and mechanisms directly involving bacterial activities in the modulation of carcinogenesis processes. Here, we review the literature about spontaneous cancer and cancer modeling in GF animals since the early studies, trying to offer a practical overview on the argument.

The Interplay between the Gut Microbiome and the Immune System in the Context of Infectious Diseases throughout Life and the Role of Nutrition in Optimizing Treatment Strategies

Infectious diseases and infections remain a leading cause of death in low-income countries and a major risk to vulnerable groups, such as infants and the elderly. The immune system plays a crucial role in the susceptibility, persistence, and clearance of these infections. With 70–80% of immune cells being present in the gut, there is an intricate interplay between the intestinal microbiota, the intestinal epithelial layer, and the local mucosal immune system. In addition to the local mucosal immune responses in the gut, it is increasingly recognized that the gut microbiome also affects systemic immunity. Clinicians are more and more using the increased knowledge about these complex interactions between the immune system, the gut microbiome, and human pathogens. The now well-recognized impact of nutrition on the composition of the gut microbiota and the immune system elucidates the role nutrition can play in improving health. This review describes the mechanisms involved in maintaining the intricate balance between the microbiota, gut health, the local immune response, and systemic immunity, linking this to infectious diseases throughout life, and highlights the impact of nutrition in infectious disease prevention and treatment.

Gut-derived Shewanella induces the differentially expressed proteins in leukocytes of Lampetra japonica

Lampreys, one of the most basal jawless vertebrates, are an excellent animal model for investigating vertebrate evolution, embryonic development, and the origin of adaptive immunity. Gut-derived Shewanella strain was isolated and then proved to induce adaptive immunity response in lampreys. Using Shewanella as the antigen, the effect of gut-derived Shewanella on lamprey leukocyte proteome was investigated via label-free liquid chromatography-tandem mass spectrometry for quantitative proteomics analysis. Twenty-five differentially expressed proteins in lamprey leukocytes were identified with significant differences. The differentially expressed proteins were associated with several biological processes. Among these proteins, the signal transducer and activator of transcription 3 (STAT3) was significantly upregulated in leukocytes after Shewanella immunization, indicating that lamprey STAT3 (L-STAT3) was involved in Shewanella-lamprey interactions. Expression pattern analysis revealed that L-STAT3 was mainly distributed in the cytoplasm and upregulated in other tissues after Shewanella immunization. Moreover, L-STAT3 overexpression could promote HEK-293 T and HeLa cell proliferation. However, the functions of L-STAT3 in the adaptive immune response of lamprey induced by gut-derived Shewanella remain to be explored. Overall, the identification of leukocyte proteins involved in Shewanella-lamprey interactions provides important information for understanding the variable lymphocyte receptor-based adaptive immune signal pathways in lampreys. SIGNIFICANCE: Lampreys are considered to be an excellent animal model for studying the origin and development of adaptive immune systems in vertebrates. Lampreys use variable lymphocyte receptors (VLRs) in recognizing antigens. However, the understanding of the VLR-based adaptive immune signal pathways in lampreys remains unclear. Intestinal bacteria could regulate the development of host immune systems. The attempts of inducing lamprey leukocyte differentially expressed proteins using the gut bacterial as the antigen will supply an promising avenue to explore the molecular mechanism of the intestinal bacteria interaction with it's host. Also, the identification of differentially expressed proteins involved in interactions between gut-derived Shewanella and lamprey will supply clues for understanding the variable lymphocyte receptor-based adaptive immune signal pathways in lampreys.

Gnotobiotic rainbow trout (Oncorhynchus mykiss) model reveals endogenous bacteria that protect against Flavobacterium columnare infection

The health and environmental risks associated with antibiotic use in aquaculture have promoted bacterial probiotics as an alternative approach to control fish infections in vulnerable larval and juvenile stages. However, evidence-based identification of probiotics is often hindered by the complexity of bacteria-host interactions and host variability in microbiologically uncontrolled conditions. While these difficulties can be partially resolved using gnotobiotic models harboring no or reduced microbiota, most host-microbe interaction studies are carried out in animal models with little relevance for fish farming. Here we studied host-microbiota-pathogen interactions in a germ-free and gnotobiotic model of rainbow trout (Oncorhynchus mykiss), one of the most widely cultured salmonids. We demonstrated that germ-free larvae raised in sterile conditions displayed no significant difference in growth after 35 days compared to conventionally-raised larvae, but were extremely sensitive to infection by Flavobacterium columnare, a common freshwater fish pathogen causing major economic losses worldwide. Furthermore, re-conventionalization with 11 culturable species from the conventional trout microbiota conferred resistance to F. columnare infection. Using mono-re-conventionalized germ-free trout, we identified that this protection is determined by a commensal Flavobacterium strain displaying antibacterial activity against F. columnare. Finally, we demonstrated that use of gnotobiotic trout is a suitable approach for the identification of both endogenous and exogenous probiotic bacterial strains protecting teleostean hosts against F. columnare. This study therefore establishes an ecologically-relevant gnotobiotic model for the study of host-pathogen interactions and colonization resistance in farmed fish.

Murine Models for the Investigation of Colonization Resistance and Innate Immune Responses in Campylobacter Jejuni Infections

Human infections with the food-borne pathogen Campylobacter jejuni are progressively increasing worldwide and constitute a significant socioeconomic burden to mankind. Intestinal campylobacteriosis in humans is characterized by bloody diarrhea, fever, abdominal pain, and severe malaise. Some individuals develop chronic post-infectious sequelae including neurological and autoimmune diseases such as reactive arthritis and Guillain-Barré syndrome. Studies unraveling the molecular mechanisms underlying campylobacteriosis and post-infectious sequelae have been hampered by the scarcity of appropriate experimental in vivo models. Particularly, conventional laboratory mice are protected from C. jejuni infection due to the physiological colonization resistance exerted by the murine gut microbiota composition. Additionally, as compared to humans, mice are up to 10,000 times more resistant to C. jejuni lipooligosaccharide (LOS) constituting a major pathogenicity factor responsible for the immunopathological host responses during campylobacteriosis. In this chapter, we summarize the recent progress that has been made in overcoming these fundamental obstacles in Campylobacter research in mice. Modification of the murine host-specific gut microbiota composition and sensitization of the mice to C. jejuni LOS by deletion of genes encoding interleukin-10 or a single IL-1 receptor-related molecule as well as by dietary zinc depletion have yielded reliable murine infection models resembling key features of human campylobacteriosis. These substantial improvements pave the way for a better understanding of the molecular mechanisms underlying pathogen-host interactions. The ongoing validation and standardization of these novel murine infection models will provide the basis for the development of innovative treatment and prevention strategies to combat human campylobacteriosis and collateral damages of C. jejuni infections.

The Host-Specific Intestinal Microbiota Composition Impacts Campylobacter coli Infection in a Clinical Mouse Model of Campylobacteriosis

Human Campylobacter-infections are progressively rising globally. However, the molecular mechanisms underlying C. coli–host interactions are incompletely understood. In this study, we surveyed the impact of the host-specific intestinal microbiota composition during peroral C. coli infection applying an established murine campylobacteriosis model. Therefore, microbiota-depleted IL-10^−/− mice were subjected to peroral fecal microbiota transplantation from murine versus human donors and infected with C. coli one week later by gavage. Irrespective of the microbiota, C. coli stably colonized the murine gastrointestinal tract until day 21 post-infection. Throughout the survey, C. coli-infected mice with a human intestinal microbiota displayed more frequently fecal blood as their murine counterparts. Intestinal inflammatory sequelae of C. coli-infection could exclusively be observed in mice with a human intestinal microbiota, as indicated by increased colonic numbers of apoptotic epithelial cells and innate as well as adaptive immune cell subsets, which were accompanied by more pronounced pro-inflammatory cytokine secretion in the colon and mesenteric lymph nodes versus mock controls. However, in extra-intestinal, including systemic compartments, pro-inflammatory responses upon pathogen challenge could be assessed in mice with either microbiota. In conclusion, the host-specific intestinal microbiota composition has a profound effect on intestinal and systemic pro-inflammatory immune responses during C. coli infection.

Microbiota composition and inflammatory immune responses upon peroral application of the commercial competitive exclusion product Aviguard® to microbiota-depleted wildtype mice

Non-antibiotic feed additives including competitive exclusion products have been shown effective in reducing pathogen loads including multi-drug resistant strains from the vertebrate gut. In the present study we surveyed the intestinal bacterial colonization properties, potential macroscopic and microscopic inflammatory sequelae and immune responses upon peroral application of the commercial competitive exclusion product Aviguard^® to wildtype mice in which the gut microbiota had been depleted by antibiotic pre-treatment. Until four weeks following Aviguard® challenge, bacterial strains abundant in the probiotic suspension stably established within the murine intestines. Aviguard® application did neither induce any clinical signs nor gross macroscopic intestinal inflammatory sequelae, which also held true when assessing apoptotic and proliferative cell responses in colonic epithelia until day 28 post-challenge. Whereas numbers of colonic innate immune cell subsets such as macrophages and monocytes remained unaffected, peroral Aviguard^® application to microbiota depleted mice was accompanied by decreases in colonic mucosal counts of adaptive immune cells such as T and B lymphocytes. In conclusion, peroral Aviguard® application results i.) in effective intestinal colonization within microbiota depleted mice, ii.) neither in macroscopic nor in microscopic inflammatory sequelae and iii.) in lower colonic mucosal T and B cell responses.

Inflammatory Immune Responses and Gut Microbiota Changes Following Campylobacter coli Infection of IL-10-/- Mice with Chronic Colitis

Human infections with the food-borne enteropathogens Campylobacter are progressively rising. Recent evidence revealed that pre-existing intestinal inflammation facilitates enteropathogenic infection subsequently exacerbating the underlying disease. Given that only little is known about C. coli-host interactions and particularly during intestinal inflammation, the aim of the present study was to survey gastrointestinal colonization properties, gut microbiota changes and pro-inflammatory sequelae upon peroral C. coli-infection of IL-10^-/- mice with chronic colitis. C. coli colonized the gastrointestinal tract of mice with varying efficiencies until day 28 post-infection and induced macroscopic and microscopic inflammatory changes as indicated by shorter colonic lengths, more distinct histopathological changes in the colonic mucosa and higher numbers of apoptotic colonic epithelial cells when compared to mock-infected controls. Furthermore, not only colonic innate and adaptive immune cell responses, but also enhanced systemic TNF-α secretion could be observed following C. coli as opposed to mock challenge. Notably, C. coli induced intestinal inflammatory sequelae were accompanied with gut microbiota shifts towards higher commensal enterobacterial loads in the infected gut lumen. Moreover, the pathogen translocated from the intestinal tract to extra-intestinal tissue sites in some cases, but never to systemic compartments. Hence, C. coli accelerates inflammatory immune responses in IL-10^-/- mice with chronic colitis.

Methods for Establishment and Maintenance of Germ-Free Rat Models

Numerous studies have demonstrated that the gut microbiota plays a vital role in human health and disease development. Although the number of studies on host–microbiota interactions have increased in recent years, the underlying pathogenesis of dysbiosis-related diseases are still largely unknown. Germ-free (GF) rodent models, with the animals housed in sterile isolators and completely free of microbiota, are useful tools to advance our understanding of host–microbiota relationship in vivo. Although protocols concerning the establishment and maintenance of GF mouse models have previously been reported, the establishment, maintenance and monitoring of GF rodents are labor-intensive, tedious and take experience and skills. The aim of our study was to establish a GF rat model for the following microbiota-related researches and provide an easy-to-use protocol for the establishment and maintenance of GF rat model in detail, including steps to set up the isolator, sterilize the flexible isolator bubble, import food, water and other supplies, and methods to acquire newborn GF rats, hand rearing of suckling GF rats and reproduction of GF offspring. During the hand feeding period, the body weight of suckling GF rats was weighed once a day to ascertain the amount of artificial milk was given. Based on our results, the body weight of suckling GF rats decreased 1 week after birth and then began to increase. Methods for verifying the quality of the model like assessing the sterile status of the rat colony are also described. Moreover, possible difficulties and challenges, especially during gavage, and suggestions to avoid contamination will be discussed. The protocol presented will facilitate the establishment of GF rat models and downstream microbiota-related researches.

Immune-modulatory Properties of the Octapeptide NAP in Campylobacter jejuni Infected Mice Suffering from Acute Enterocolitis

Human infections with the food-borne zoonotic pathogen Campylobacter jejuni are progressively rising and constitute serious global public health and socioeconomic burdens. Hence, application of compounds with disease-alleviating properties are required to combat campylobacteriosis and post-infectious sequelae. In our preclinical intervention study applying an acute C. jejuni induced enterocolitis model, we surveyed the anti-pathogenic and immune-modulatory effects of the octapeptide NAP which is well-known for its neuroprotective and anti-inflammatory properties. Therefore, secondary abiotic IL-10^−/− mice were perorally infected with C. jejuni and intraperitoneally treated with synthetic NAP from day 2 until day 5 post-infection. NAP-treatment did not affect gastrointestinal C. jejuni colonization but could alleviate clinical signs of infection that was accompanied by less pronounced apoptosis of colonic epithelial cells and enhancement of cell regenerative measures on day 6 post-infection. Moreover, NAP-treatment resulted in less distinct innate and adaptive pro-inflammatory immune responses that were not restricted to the intestinal tract but could also be observed in extra-intestinal and even systemic compartments. NAP-treatment further resulted in less frequent translocation of viable pathogens from the intestinal tract to extra-intestinal including systemic tissue sites. For the first time, we here provide evidence that NAP application constitutes a promising option to combat acute campylobacteriosis.

Early Effect of Supplemented Infant Formulae on Intestinal Biomarkers and Microbiota: A Randomized Clinical Trial

Background: Post-natal gut maturation in infants interrelates maturation of the morphology, digestive, and immunological functions and gut microbiota development. Here, we explored both microbiota development and markers of gut barrier and maturation in healthy term infants during their early life to assess the interconnection of gut functions during different infant formulae regimes. Methods: A total of 203 infants were enrolled in this randomized double-blind controlled trial including a breastfed reference group. Infants were fed starter formulae for the first four weeks of life, supplemented with different combination of nutrients (lactoferrin, probiotics (Bifidobacterium animal subsp. Lactis) and prebiotics (Bovine Milk-derived Oligosaccharides—BMOS)) and subsequently fed the control formula up to eight weeks of life. Stool microbiota profiles and biomarkers of early gut maturation, calprotectin (primary outcome), elastase, α-1 antitrypsin (AAT) and neopterin were measured in feces at one, two, four, and eight weeks. Results: Infants fed formula containing BMOS had lower mean calprotectin levels over the first two to four weeks compared to the other formula groups. Elastase and AAT levels were closer to levels observed in breastfed infants. No differences were observed for neopterin. Global differences between the bacterial communities of all groups were assessed by constrained multivariate analysis with hypothesis testing. The canonical correspondence analysis (CCA) at genus level showed overlap between microbiota profiles at one and four weeks of age in the BMOS supplemented formula group with the breastfed reference, dominated by bifidobacteria. Microbiota profiles of all groups at four weeks were significantly associated with the calprotectin levels at 4 (CCA, p = 0.018) and eight weeks of age (CCA, p = 0.026). Conclusion: A meaningful correlation was observed between changes in microbiota composition and gut maturation marker calprotectin. The supplementation with BMOS seems to favor gut maturation closer to that of breastfed infants.