Small intestinal nematode infection of mice is associated with increased enterobacterial loads alongside the intestinal tract

Worming into infancy: Exploring helminth-microbiome interactions in early life

There is rapidly growing awareness of microbiome assembly and function in early-life gut health. Although many factors, such as antibiotic use and highly processed diets, impinge on this process, most research has focused on people residing in high-income countries. However, much of the world's population lives in low- and middle-income countries (LMICs), where, in addition to erratic antibiotic use and suboptimal diets, these groups experience unique challenges. Indeed, many children in LMICs are infected with intestinal helminths. Although helminth infections are strongly associated with diverse developmental co-morbidities and induce profound microbiome changes, few studies have directly examined whether intersecting pathways between these components of the holobiont shape health outcomes in early life. Here, we summarize microbial colonization within the first years of human life, how helminth-mediated changes to the gut microbiome may affect postnatal growth, and why more research on this relationship may improve health across the lifespan.

Excretory-secretory products from adult helminth Nippostrongylus brasiliensis have in vitro bactericidal activity

Introduction. Intestinal helminths and microbiota share the same anatomical niche during infection and are likely to interact either directly or indirectly. Whether intestinal helminths employ bactericidal strategies that influence their microbial environment is not completely understood.Hypothesis. In the present study, the hypothesis that the adult hookworm Nippostrongylus brasiliensis produces molecules that impair bacterial growth in vitro, is tested.Aim. To investigate the in vitro bactericidal activity of Nippostrongylus brasiliensis against commensal and pathogenic bacteria.Methodology. The bactericidal effect of somatic extract and excretory-secretory products of adult Nippostrongylus brasiliensis on Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli, Salmonella enterica serovar Typhimurium, and Klebsiella pneumoniae) bacteria was assessed using growth assays. Minimum inhibitory concentration and minimum bactericidal concentration assays were performed using excretory-secretory products released from the pathogen.Results. Broad-spectrum in vitro bactericidal activity in excretory-secretory products, but not somatic extract of adult Nippostrongylus brasiliensis was detected. The bactericidal activity of excretory-secretory products was concentration-dependent, maintained after heat treatment, and preserved after repeated freezing and thawing.Conclusion. The results of this study demonstrate that helminths such as Nippostrongylus brasiliensis release molecules via their excretory-secretory pathway that have broad-spectrum bactericidal activity. The mechanisms responsible for this bactericidal activity remain to be determined and further studies aimed at isolating and identifying active bactericidal molecules are needed.

The Impact of Intestinal Inflammation on Nematode's Excretory-Secretory Proteome

Parasitic nematodes and their products are promising candidates for therapeutics against inflammatory bowel diseases (IBD). Two species of nematodes, the hookworm Necator americanus and the whipworm Trichuis suis, are being used in clinical treatment trials of IBD referred to as "helminth therapy". Heligmosomoides polygyrus is a well-known model for human hookworm infections. Excretory-secretory (ES) products of H. polygyrus L4 stage that developed during colitis show a different immunomodulatory effect compared to the ES of H. polgyrus from healthy mice. The aim of the study was to evaluate excretory-secretory proteins produced by H. polygyrus L4 stage males and females that developed in the colitic milieu. Mass spectrometry was used to identify proteins. Blast2GO was used to investigate the functions of the discovered proteins. A total of 387 proteins were identified in the ES of H. polygyrus L4 males (HpC males), and 330 proteins were identified in the ES of L4 females that developed in the colitic milieu (HpC females). In contrast, only 200 proteins were identified in the ES of L4 males (Hp males) and 218 in the ES of L4 females (Hp females) that developed in control conditions. Most of the proteins (123) were detected in all groups. Unique proteins identified in the ES of HpC females included annexin, lysozyme-2, apyrase, and galectin. Venom allergen/Ancylostoma-secreted protein-like, transthyretin-like family proteins, and galectins were found in the secretome of HpC males but not in the secretome of control males. These molecules may be responsible for the therapeutic effects of nematodes in DSS-induced colitis.

Triple Therapy with Metformin, Ketogenic Diet, and Metronomic Cyclophosphamide Reduced Tumor Growth in MYCN-Amplified Neuroblastoma Xenografts

Neuroblastoma (NB) is a childhood cancer in which amplification of the MYCN gene is the most acknowledged marker of poor prognosis. MYCN-amplified NB cells rely on both glycolysis and mitochondrial oxidative phosphorylation (OXPHOS) for energy production. Previously, we demonstrated that a ketogenic diet (KD) combined with metronomic cyclophosphamide (CP) delayed tumor growth in MYCN-amplified NB xenografts. The anti-diabetic drug metformin (MET) also targets complex I of the OXPHOS system. Therefore, MET-induced disruptions of mitochondrial respiration may enhance the anti-tumor effect of CP when combined with a KD. In this study, we found that MET decreased cell proliferation and mitochondrial respiration in MYCN-amplified NB cell lines, while the combination of KD, MET, and low-dose CP (triple therapy) also reduced tumor growth and improved survival in vivo in MYCN-amplified NB xenografts. Gene ontology enrichment analysis revealed that this triple therapy had the greatest effect on the transcription of genes involved in fatty acid ß-oxidation, which was supported by the increased protein expression of CPT1A, a key mitochondrial fatty acid transporter. We suspect that alterations to ß-oxidation alongside the inhibition of complex I may hamper mitochondrial energy production, thus explaining these augmented anti-tumor effects, suggesting that the combination of MET and KD is an effective adjuvant therapy to CP in MYCN-amplified NB xenografts.

The role of the host gut microbiome in the pathophysiology of schistosomiasis

The pathophysiology of schistosomiasis is linked to the formation of fibrous granulomas around eggs that become trapped in host tissues, particularly the intestines and liver, during their migration to reach the lumen of the vertebrate gut. While the development of Schistosoma egg-induced granulomas is the result of finely regulated crosstalk between egg-secreted antigens and host immunity, evidence has started to emerge of the likely contribution of an additional player-the host gut microbiota-to pathological processes that culminate with the formation of these tissue lesions. Uncovering the role(s) of schistosome-mediated changes in gut microbiome composition and function in granuloma formation and, more broadly, in the pathophysiology of schistosomiasis, will shed light on the mechanisms underlying this three-way parasite-host-microbiome interplay. Such knowledge may, in turn, pave the way towards the discovery of novel therapeutic targets and control strategies.

Metagenome reveals caprine abomasal microbiota diversity at early and late stages of Haemonchus contortus infection

Haemonchus contortus is one of the most detrimental gastrointestinal nematode parasites for small ruminants, especially in tropics and subtropics. Gastrointestinal nematode and microbiota share the same microhabitat; thus they interact with each other and their host. Metagenomics tools provide a promising way to examine the alterations in the gastric microbial composition induces by gastrointestinal parasites. In this study, we used metagenomics tools to characterize the impact of H. contortus infection on the caprine abomasal microbiota at early and late stage of infection and compared it with non-infected control. Our results showed that H. contortus infection caused a significant increase in abomasal pH at early (7 days post-infection) and late stage of infection (56 days post-infection). The analysis of alpha and beta diversity showed that the microbiota diversity both in number and in proportion was significantly affected at early and late stage of infection. All microbiota classes are impacted by H. contortus infection but Clostridia and Bacteroidia are more concerned. In infected animals, the genera Prevotella decreased at 7 and 56 days post-infection. Here we showed that the abomasal microbiota was significantly affected early after H. contortus infection, and these changes persist at late stage of the infection.

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.

Gut microbiota of endangered Australian sea lion pups is unchanged by topical ivermectin treatment for endemic hookworm infection

The gut microbiota is essential for the development and maintenance of the hosts' immune system. Disturbances to the gut microbiota in early life stages can result in long-lasting impacts on host health. This study aimed to determine if topical ivermectin treatment for endemic hookworm (Uncinaria sanguinis) infection in endangered Australian sea lion (Neophoca cinerea) pups resulted in gut microbial changes. The gut microbiota was characterised for untreated (control) (n = 23) and treated (n = 23) Australian sea lion pups sampled during the 2019 and 2020/21 breeding seasons at Seal Bay, Kangaroo Island. Samples were collected pre- and post-treatment on up to four occasions over a four-to-five-month period. The gut microbiota of untreated (control) and treated pups in both seasons was dominated by five bacterial phyla, Fusobacteria, Firmicutes, Proteobacteria, Actinobacteria and Bacteroidetes. A significant difference in alpha diversity between treatment groups was seen in pups sampled during the 2020/21 breeding season (p = 0.008), with higher richness and diversity in treated pups. Modelling the impact of individual pup identification (ID), capture, pup weight (kg), standard length (cm), age and sex on beta diversity revealed that pup ID accounted for most of the variation (35% in 2019 and 42% in 2020/21), with pup ID, capture, and age being the only significant contributors to microbial variation (p < 0.05). There were no statistically significant differences in the composition of the microbiota between treatment groups in both the 2019 and 2020/21 breeding seasons, indicating that topical ivermectin treatment did not alter the composition of the gut microbiota. To our knowledge, this is the first study to characterise the gut microbiota of free-ranging Australian pinniped pups, compare the composition across multiple time points, and to consider the impact of parasitic treatment on overall diversity and microbial composition of the gut microbiota. Importantly, the lack of compositional changes in the gut microbiota with treatment support the utility of topical ivermectin as a safe and minimally invasive management strategy to enhance pup survival in this endangered species.

Guts within guts: the microbiome of the intestinal helminth parasite Ascaris suum is derived but distinct from its host

BACKGROUND

Intestinal helminths are extremely prevalent among humans and animals. In particular, intestinal roundworms affect more than 1 billion people around the globe and are a major issue in animal husbandry. These pathogens live in intimate contact with the host gut microbiota and harbor bacteria within their own intestines. Knowledge of the bacterial host microbiome at the site of infection is limited, and data on the parasite microbiome is, to the best of our knowledge, non-existent.

RESULTS

The intestinal microbiome of the natural parasite and zoonotic macropathogen, Ascaris suum was analyzed in contrast to the diversity and composition of the infected host gut. 16S sequencing of the parasite intestine and host intestinal compartments showed that the parasite gut has a significantly less diverse microbiome than its host, and the host gut exhibits a reduced microbiome diversity at the site of parasite infection in the jejunum. While the host's microbiome composition at the site of infection significantly determines the microbiome composition of its parasite, microbial signatures differentiate the nematodes from their hosts as the Ascaris intestine supports the growth of microbes that are otherwise under-represented in the host gut.

CONCLUSION

Our data clearly indicate that a nematode infection reduces the microbiome diversity of the host gut, and that the nematode gut represents a selective bacterial niche harboring bacteria that are derived but distinct from the host gut. Video Abstract.

Hymenolepis diminuta Reduce Lactic Acid Bacterial Load and Induce Dysbiosis in the Early Infection of the Probiotic Colonization of Swiss Albino Rat

Tapeworm infection continues to be an important cause of morbidity worldwide. Recent metagenomics studies have established a link between gut microbiota and parasite infection. The identification of gut probiotics is of foremost importance to explore its relationship and function with the parasite in the host. In this study, the gut content of hosts infected with tapeworm Hymenolepis diminuta and non-infected host gut were disected out to determine their Lactic acid bacterial (LAB) population in MRS agar and microbial community was analysed by metagenomics. The bacterial count was calculated on a bacterial counting chamber and their morphology was determined microscopically and biochemically. Further, to determine the safety profile antibiotic resistance test, antimicrobial, hemolytic activity, and adhesion capability were calculated. We found six dominant probiotic strains and a decrease in LAB load from 1.7-2.3 × 10⁷ CFU/mL in the uninfected group to a range of 8.4 × 10⁵ CFU/mL to 3.2 × 10⁵ CFU/mL in the infected groups with respect to an increase in the parasite number from 10-18. In addition, we found a depletion in the probiotic relative abundance of Lactobacillus and an enrichment in potentially pathogenic Proteobacteria, Fusobacteria, and Streptococcus. Phylogenetic analysis of the six probiotics revealed a close similarity with different strains of L. brevis, L. johnsonii, L. taiwansis, L. reuteri, L. plantarum, and L. pentosus. Thus, this study suggests that the parasite inhibits probiotic colonization in the gut during its early establishment of infection inside the host.

Sex—the most underappreciated variable in research: insights from helminth-infected hosts

The sex of a host affects the intensity, prevalence, and severity of helminth infection. In many cases, one sex has been found to be more susceptible than the other, with the prevalence and intensity of helminth infections being generally higher among male than female hosts; however, many exceptions exist. This observed sex bias in parasitism results primarily from ecological, behavioural, and physiological differences between males and females. Complex interactions between these influences modulate the risk of infection. Indeed, an interplay among sex hormones, sex chromosomes, the microbiome and the immune system significantly contributes to the generation of sex bias among helminth-infected hosts. However, sex hormones not only can modulate the course of infection but also can be exploited by the parasites, and helminths appear to have developed molecules and pathways for this purpose. Furthermore, host sex may influence the efficacy of anti-helminth vaccines; however, although little data exist regarding this sex-dependent efficacy, host sex is known to influence the response to vaccines. Despite its importance, host sex is frequently overlooked in parasitological studies. This review focuses on the key contributors to sex bias in the case of helminth infection. The precise nature of the mechanisms/factors determining these sex-specific differences generally remains largely unknown, and this represents an obstacle in the development of control methods. There is an urgent need to identify any protective elements that could be targeted in future therapies to provide optimal disease management with regard to host sex. Hence, more research is needed into the impact of host sex on immunity and protection.

Changes in resident microbiota associated with mice susceptibility or resistance to the intestinal trematode Echinostoma caproni

Echinostoma caproni (Trematoda: Echinostomatidae) is an intestinal trematode with no tissue phases in the definitive host that has been extensively used as an experimental model to study the factors that determine resistance against intestinal helminths. In E. caproni infections in mice, interleukin-25 (IL-25) plays a critical role and it is required for the resistance to infection. However, little is known on the factors that determine its production. Primary E. caproni infection in mice is characterized by the development of chronic infections and elevated worm recovery, in relation to a local Th1 response with elevated production of interferon-γ. However, partial resistance against secondary E. caproni infections in ICR (Institute of Cancer Research) mice is developed after the chemotherapeutic cure of a primary infection and the innately produced IL-25 after pharmacological treatment. In this paper, we analyse the potential role of intestinal microbiota in the production of IL-25, and the subsequent resistance to infection. For this purpose, we analysed the production of IL-25 under conditions of experimental dysbiosis and also the changes in the resident microbiota in primary infections, pharmacological curation and secondary infections. The results obtained showed that resident microbiota play a major role in the production of IL-25 and the appearance of members of the phylum Verrucomicrobia as a consequence of the curation of the primary infection could be related to the partial resistance to secondary infection.

Antibiotic-induced gut dysbiosis leads to activation of microglia and impairment of cholinergic gamma oscillations in the hippocampus

Antibiotics are widely applied for the treatment of bacterial infections, but their long-term use may lead to gut flora dysbiosis and detrimental effects on brain physiology, behavior as well as cognitive performance. Still, a striking lack of knowledge exists concerning electrophysiological correlates of antibiotic-induced changes in gut microbiota and behavior. Here, we investigated changes in the synaptic transmission and plasticity together with behaviorally-relevant network activities from the hippocampus of antibiotic-treated mice. Prolonged antibiotic treatment led to a reduction of myeloid cell pools in bone marrow, circulation and those surveilling the brain. Circulating Ly6C^hi inflammatory monocytes adopted a proinflammatory phenotype with increased expression of CD40 and MHC II. In the central nervous system, microglia displayed a subtle activated phenotype with elevated CD40 and MHC II expression, increased IL-6 and TNF production as well as with an increased number of Iba1 + cells in the hippocampal CA3 and CA1 subregions. Concomitantly, we detected a substantial reduction in the synaptic transmission in the hippocampal CA1 after antibiotic treatment. In line, carbachol-induced cholinergic gamma oscillation were reduced upon antibiotic treatment while the incidence of hippocampal sharp waves was elevated. These alterations were associated with the global changes in the expression of neurotrophin nerve growth factor and inducible nitric oxide synthase, both of which have been shown to influence cholinergic system in the hippocampus. Overall, our study demonstrates that antibiotic-induced dysbiosis of the gut microbiome and subsequent alteration of the immune cell function are associated with reduced synaptic transmission and gamma oscillations in the hippocampus, a brain region that is critically involved in mediation of innate and cognitive behavior.

The phytonutrient cinnamaldehyde limits intestinal inflammation and enteric parasite infection

Phytonutrients such as cinnamaldehyde (CA) have been studied for their effects on metabolic diseases, but their influence on mucosal inflammation and immunity to enteric infection are not well documented. Here, we show that consumption of CA in mice significantly down-regulates transcriptional pathways connected to inflammation in the small intestine, and alters T-cell populations in mesenteric lymph nodes. During infection with the enteric helminth Heligomosomoides polygyrus, CA treatment attenuated infection-induced changes in biological pathways connected to cell cycle and mitotic activity, and tended to reduce worm burdens. Mechanistically, CA did not appear to exert activity through a prebiotic effect, as CA treatment did not significantly change the composition of the gut microbiota. Instead, in vitro experiments showed that CA directly induced xenobiotic metabolizing pathways in intestinal epithelial cells and suppressed endotoxin-induced inflammatory responses in macrophages. Collectively, our results show that CA down-regulates inflammatory pathways in the intestinal mucosa and can limit the pathological response to enteric infection. These properties appear to be largely independent of the gut microbiota, and instead connected to the ability of CA to induce antioxidant pathways in intestinal cells. Our results encourage further investigation into the use of CA and related phytonutrients as functional food components to promote intestinal health in humans and animals.

Helminth infections and cardiovascular diseases: A role for the microbiota and Mϕs?

Cardiovascular diseases are rising in developing countries with increasing urbanization and lifestyle changes and remains a major cause of death in the developed world. In this mini review, we discuss the possibility that the effect of helminth infections on the immune system and the microbiota may affect risk factors in cardiovascular diseases such as atherosclerosis, as part of the hygiene hypothesis. The effects of Type 2 immune responses induced by helminths and helminth derived molecules on regulating metabolism and Mϕ function could be a mechanistic link for further investigation. We emphasize the complexity and difficulties in determining indirect or direct and causal relationships between helminth infection status and cardiovascular diseases. New experimental models, such as rewilding laboratory mice, whereby different aspects of the environment and host genetics can be carefully dissected may provide further mechanistic insights and therapeutic strategies for treating cardiovascular diseases.

Treatment with the Probiotic Product Aviguard® Alleviates Inflammatory Responses during Campylobacter jejuni-Induced Acute Enterocolitis in Mice

Prevalences of Campylobacter (C.) jejuni infections are progressively rising globally. Given that probiotic feed additives, such as the commercial product Aviguard^®, have been shown to be effective in reducing enteropathogens, such as Salmonella, in vertebrates, including livestock, we assessed potential anti-pathogenic and immune-modulatory properties of Aviguard^® during acute C. jejuni-induced murine enterocolitis. Therefore, microbiota-depleted IL-10^−/− mice were infected with C. jejuni strain 81-176 by gavage and orally treated with Aviguard^® or placebo from day 2 to 4 post-infection. The applied probiotic bacteria could be rescued from the intestinal tract of treated mice, but with lower obligate anaerobic bacterial counts in C. jejuni-infected as compared to non-infected mice. Whereas comparable gastrointestinal pathogen loads could be detected in both groups until day 6 post-infection, Aviguard^® treatment resulted in improved clinical outcome and attenuated apoptotic cell responses in infected large intestines during acute campylobacteriosis. Furthermore, less distinct pro-inflammatory immune responses could be observed not only in the intestinal tract, but also in extra-intestinal compartments on day 6 post-infection. In conclusion, we show here for the first time that Aviguard^® exerts potent disease-alleviating effects in acute C. jejuni-induced murine enterocolitis and might be a promising probiotic treatment option for severe campylobacteriosis in humans.

Can microorganisms assist the survival and parasitism of plant-parasitic nematodes?

Plant-parasitic nematodes (PPNs) remain a hardly treatable problem in many crops worldwide. Low efficacy of many biocontrol agents may be due to negligence of the native microbiota that is naturally associated with nematodes in soil, and which may protect nematodes against microbial antagonists. This phenomenon is more extensively studied for other nematode parasites, so we compiled these studies and drew parallels to the existing knowledge on PPN. We describe how microbial-mediated modulation of host immune responses facilitate nematode parasitism and discuss the role of Caenorhabditis elegans-protective microbiota to get an insight into the microbial protection of PPNs in soil. Molecular mechanisms of PPN-microbial interactions are also discussed. An understanding of microbial-aided PPN performance is thus pivotal for efficient management of PPNs.

A gastrointestinal nematode in pregnant and lactating mice alters maternal and neonatal microbiomes

The maternal microbiome is understood to be the principal source of the neonatal microbiome but the consequences of intestinal nematodes on pregnant and lactating mothers and implications for the neonatal microbiome are unknown. Using pregnant CD1 mice infected with Heligmosomoides bakeri, we investigated the microbiomes in maternal tissues (intestine, vagina, and milk) and in the neonatal stomach using MiSeq sequencing of bacterial 16S rRNA genes. Our first hypothesis was that maternal nematode infection altered the maternal intestinal, vaginal, and milk microbiomes and associated metabolic pathways. Maternal nematode infection was associated with increased beta-diversity and abundance of fermenting bacteria as well as Lactobacillus in the maternal caecum 2 days after parturition, together with down-regulated carbohydrate, amino acid and vitamin biosynthesis pathways. Maternal nematode infection did not alter the vaginal or milk microbiomes. Our second hypothesis was that maternal infection would shape colonization of the neonatal microbiome. Although the pup stomach microbiome was similar to that of the maternal vaginal microbiome, pups of infected dams had higher beta-diversity at day 2, and a dramatic expansion in the abundance of Lactobacillus between days 2 and 7 compared with pups nursing uninfected dams. Our third hypothesis that maternal nematode infection altered the composition of neonatal microbiomes was confirmed as we observed up-regulation of several putatively beneficial microbial pathways associated with synthesis of essential and branched-chain amino acids, vitamins, and short-chain fatty acids. We believe this is the first study to show that a nematode living in the maternal intestine is associated with altered composition and function of the neonatal microbiome.

Survey of Pathogen-Lowering and Immuno-Modulatory Effects Upon Treatment of Campylobacter coli-Infected Secondary Abiotic IL-10-/- Mice with the Probiotic Formulation Aviguard®

The prevalence of infections with the zoonotic enteritis pathogen Campylobacter coli is increasing. Probiotic formulations constitute promising antibiotic-independent approaches to reduce intestinal pathogen loads and modulate pathogen-induced immune responses in the infected human host, resulting in acute campylobacteriosis and post-infectious sequelae. Here, we address potential antipathogenic and immuno-modulatory effects of the commercial product Aviguard^® during experimental campylobacteriosis. Secondary abiotic IL-10^-/- mice were infected with a C. coli patient isolate on days 0 and 1, followed by oral Aviguard^® treatment on days 2, 3 and 4. Until day 6 post-infection, Aviguard^® treatment could lower the pathogen burdens within the proximal but not the distal intestinal tract. In contrast, the probiotic bacteria had sufficiently established in the intestines with lower fecal loads of obligate anaerobic species in C. coli-infected as compared to uninfected mice following Aviguard^® treatment. Aviguard^® application did not result in alleviated clinical signs, histopathological or apoptotic changes in the colon of infected IL-10^-/- mice, whereas, however, Aviguard^® treatment could dampen pathogen-induced innate and adaptive immune responses in the colon, accompanied by less distinct intestinal proinflammatory cytokine secretion. In conclusion, Aviguard^® constitutes a promising probiotic compound to alleviate enteropathogen-induced proinflammatory immune responses during human campylobacteriosis.

Effect of Echinostoma caproni on Presumptive Lactic Acid Bacteria Abundance and Salmonella enterica Serovar Typhimurium Colonization in the Mouse Gut

Co-infections of mammalian hosts with intestinal helminths and bacterial pathogens are common, especially in areas with inadequate sanitation. Interactions between co-infecting species and host microbiota can cause significant changes in host immunity, disease severity, and pathogen transmission, requiring unique treatment for each case. A greater understanding of the influences of parasite-bacteria co-infections will improve diagnosis and therapeutic approaches to control infectious diseases. To study the influence of the trematode parasite Echinostoma caproni on commensal and pathogenic bacteria in the mouse gut, we examined the abundance of intestinal lactic acid bacteria and Salmonella enterica serovar Typhimurium in control mice not exposed to E. caproni (P-) or S. Typhimurium (S-), E. caproni-infected (P+S-), S. Typhimurium-infected (P-S+), and E. caproni-S. Typhimurium co-infected (P+S+) mice, and determined bacterial burdens in the livers and spleens of the P-S+ and P+S+ mice. We also examined a subset of P+S- and P+S+ mice for survival and the relative location of E. caproni in the small intestine. The numbers of presumptive lactic acid bacteria were significantly higher in the P+S+ and P-S+ mice compared to the uninfected mice, and S. Typhimurium colonization in the liver and spleen was significantly reduced in the P+S+ mice compared to the P-S+ mice. Echinostoma caproni were located anteriorly in the intestine of P+S- mice, while in the P+S+ mice, the parasites were distributed more posteriorly. Survival of E. caproni was unaffected in either group. The results of our study suggest that E. caproni facilitates a higher abundance of presumptive lactic acid bacteria in the mouse intestine and reduces colonization of S. Typhimurium in the liver and spleen of the co-infected host.

Whipworm-Associated Intestinal Microbiome Members Consistent Across Both Human and Mouse Hosts

The human whipworm Trichuris trichiura infects 289 million people worldwide, resulting in substantial morbidity. Whipworm infections are difficult to treat due to low cure rates and high reinfection rates. Interactions between whipworm and its host's intestinal microbiome present a potential novel target for infection control or prevention but are very complicated and are identified using inconsistent methodology and sample types across the literature, limiting their potential usefulness. Here, we used a combined 16S rRNA gene OTU analysis approach (QIIME2) for samples from humans and mice infected with whipworm (T. trichiura and T. muris, respectively) to identify for the first time, bacterial taxa that were consistently associated with whipworm infection spanning host species and infection status using four independent comparisons (baseline infected vs uninfected and before vs after deworming for both humans and mice). Using these four comparisons, we identified significant positive associations for seven taxa including Escherichia, which has been identified to induce whipworm egg hatching, and Bacteroides, which has previously been identified as a major component of the whipworm internal microbiome. We additionally identified significant negative associations for five taxa including four members of the order Clostridiales, two from the family Lachnospiraceae, including Blautia which was previously identified as positively associated with whipworm in independent human and mouse studies. Using this approach, bacterial taxa of interest for future association and mechanistic studies were identified, and several were validated by RT-qPCR. We demonstrate the applicability of a mouse animal model for comparison to human whipworm infections with respect to whipworm-induced intestinal microbiome disruption and subsequent restoration following deworming. Overall, the novel cross-species analysis approach utilized here provides a valuable research tool for studies of the interaction between whipworm infection and the host intestinal microbiome.

Strong effects of lab-to-field environmental transitions on the bacterial intestinal microbiota of Mus musculus are modulated by Trichuris murisinfection

Studies of controlled lab animals and natural populations represent two insightful extremes of microbiota research. We bridged these two approaches by transferring lab-bred female C57BL/6 mice from a conventional mouse facility to an acclimation room and then to an outdoor enclosure, to investigate how the gut microbiota changes with environment. Mice residing under constant conditions served as controls. Using 16S rRNA sequencing of fecal samples, we found that the shift in temperature and humidity, as well as exposure to a natural environment, increased microbiota diversity and altered community composition. Community composition in mice exposed to high temperatures and humidity diverged as much from the microbiota of mice housed outdoors as from the microbiota of control mice. Additionally, infection with the nematode Trichuris muris modulated how the microbiota responded to environmental transitions: The dynamics of several families were buffered by the nematodes, while invasion rates of two taxa acquired outdoors were magnified. These findings suggest that gut bacterial communities respond dynamically and simultaneously to changes within the host's body (e.g. the presence of nematodes) and to changes in the wider environment of the host.

Embracing nature's complexity: Immunoparasitology in the wild

A wealth of research is dedicated to understanding how resistance against parasites is conferred and how parasite-driven pathology is regulated. This research is in part driven by the hope to better treatments for parasitic diseases of humans and livestock, and in part by immunologists who use parasitic infections as biomedical tools to evoke physiological immune responses. Much of the current mechanistic knowledge has been discovered in laboratory studies using model organisms, especially the laboratory mouse. However, wildlife are also hosts to a range of parasites. Through the study of host-parasite interactions in these non-laboratory systems we can gain a deeper understanding of parasite immunology in a more natural, complex environment. With a focus on helminth parasites, we here explore the insights gained into parasite-induced immune responses through (for immunologists) non-conventional experimental systems, and how current core findings from laboratory studies are reflected in these more natural conditions. The quality of the immune response is undoubtedly a central player in susceptibility versus resistance, as many laboratory studies have shown. Yet, in the wild, parasite infections tend to be chronic diseases. Whilst reading our review, we encourage the reader to consider the following questions which may (only) be answered by studying naturally occurring parasites in the wild: a) what type of immune responses are mounted against parasites in different hosts in the wild, and how do they vary within an individual over time, between individuals of the same species and between species? b) can we use wild or semi-wild study systems to understand the evolutionary drivers for tolerance versus resistance towards a parasite? c) what determines the ability of the host to cope with an infection and is there a link with the type of immune response mounted? d) can we modulate environmental factors to manipulate a wild animal's immune response to parasitic infections, with translation potential for humans, wildlife, and livestock? and e) in context of this special issue, what lessons for Type 2 immunity can we glean from studying animals in their natural environments? Further, we aim to integrate some of the knowledge gained in semi-wild and wild settings with knowledge gained from traditional laboratory-based research, and to raise awareness for the opportunities (and challenges) that come with integrating a multitude of naturally-occurring variables into immunoparasitological research.

Helminth Interactions with Bacteria in the Host Gut Are Essential for Its Immunomodulatory Effect

Colonization by the benign tapeworm, Hymenolepis diminuta, has been associated with a reduction in intestinal inflammation and changes in bacterial microbiota. However, the role of microbiota in the tapeworm anti-inflammatory effect is not yet clear, and the aim of this study was to determine whether disruption of the microflora during worm colonization can affect the course of intestinal inflammation. We added a phase for disrupting the intestinal microbiota using antibiotics to the experimental design for which we previously demonstrated the protective effect of H. diminuta. We monitored the immunological markers, clinical parameters, bacterial microbiota, and histological changes in the colon of rats. After a combination of colonization, antibiotics, and colitis induction, we had four differently affected experimental groups. We observed a different course of the immune response in each group, but no protective effect was found. Rats treated with colonization and antibiotics showed a strong induction of the Th2 response as well as a significant change in microbial diversity. The microbial results also revealed differences in the richness and abundance of some bacterial taxa, influenced by various factors. Our data suggest that interactions between the tapeworm and bacteria may have a major impact on its protective effect.

Eukaryotic and Prokaryotic Microbiota Interactions

The nature of the relationship between the communities of microorganisms making up the microbiota in and on a host body has been increasingly explored in recent years. Microorganisms, including bacteria, archaea, viruses, parasites and fungi, have often long co-evolved with their hosts. In human, the structure and diversity of microbiota vary according to the host’s immunity, diet, environment, age, physiological and metabolic status, medical practices (e.g., antibiotic treatment), climate, season and host genetics. The recent advent of next generation sequencing (NGS) technologies enhanced observational capacities and allowed for a better understanding of the relationship between distinct microorganisms within microbiota. The interaction between the host and their microbiota has become a field of research into microorganisms with therapeutic and preventive interest for public health applications. This review aims at assessing the current knowledge on interactions between prokaryotic and eukaryotic communities. After a brief description of the metagenomic methods used in the studies were analysed, we summarise the findings of available publications describing the interaction between the bacterial communities and protozoa, helminths and fungi, either in vitro, in experimental models, or in humans. Overall, we observed the existence of a beneficial effect in situations where some microorganisms can improve the health status of the host, while the presence of other microorganisms has been associated with pathologies, resulting in an adverse effect on human health.

Effects of seasonality and previous logging on faecal helminth-microbiota associations in wild lemurs

Gastrointestinal helminth-microbiota associations are shaped by various ecological processes. The effect of the ecological context of the host on the bacterial microbiome and gastrointestinal helminth parasites has been tested in a number of ecosystems and experimentally. This study takes the important step to look at these two groups at the same time and to start to examine how these communities interact in a changing host environment. Fresh faecal samples (N = 335) from eight wild Eulemur populations were collected over 2 years across Madagascar. We used 16S ribosomal RNA gene sequencing to characterise the bacterial microbiota composition, and faecal flotation to isolate and morphologically identify nematode eggs. Infections with nematodes of the genera Callistoura and Lemuricola occurred in all lemur populations. Seasonality significantly contributed to the observed variation in microbiota composition, especially in the dry deciduous forest. Microbial richness and Lemuricola spp. infection prevalence were highest in a previously intensely logged site, whereas Callistoura spp. showed no such pattern. In addition, we observed significant correlations between gastrointestinal parasites and bacterial microbiota composition in these lemurs, with 0.4-0.7% of the variation in faecal bacterial microbiota composition being explained by helminth infections. With this study, we show effects of environmental conditions on gastrointestinal nematodes and bacterial interactions in wild lemurs and believe it is essential to consider the potential role of microbiome-parasite associations on the hosts' GI stability, health, and survival.

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.

Preconception helminth infection alters offspring microbiota and immune subsets in a mouse model

Both maternal microbiota and helminth infection may alter offspring immunity but the relationship between these is underexplored. We hypothesized that maternal helminth exposure prior to pregnancy has lasting consequences on offspring intestinal microbiota and consequent immunity. Female BALB/c adult mice were infected with 500L3 Nippostrongylus brasiliensis (N brasiliensis). Infection was cleared by ivermectin treatment, and mice were mated 3 weeks post-infection (NbM). Control mice were not infected but were exposed to ivermectin (NvM). We analysed maternal gut microbiota during pregnancy, breastmilk microbiota and offspring faecal microbiota and immunity 2 weeks after delivery. During pregnancy, NbM (Mothers previously infected with Nippostrongylus brasiliensis) displayed significantly altered stool bacterial communities (R2  = .242; P = .001), with increased abundance of Enterococcaceae versus NvM (Naive mothers). Similarly, we observed a profound impact on breastmilk microbiota in NbM vs NvM. Moreover, NbM pups showed significantly altered gut microbial communities at 14 days of age versus those born to NvM with increased relative abundance of Coriobacteriaceae and Micrococcaceae. These changes were associated with alterations in pup immunity including increased frequencies and numbers of activated CD4 T cells (CD4 + CD44hi) in NbM offspring spleens. Taken together, we show that preconception helminth infections impact offspring immunity possibly through alteration of maternal and offspring microbiota.

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.

Immunity to Soil-Transmitted Helminths: Evidence From the Field and Laboratory Models

Infection with soil-transmitted helminths (STH) remains a major burden on global health and agriculture. Our understanding of the immunological mechanisms that govern whether an individual is resistant or susceptible to infection is derived primarily from model infections in rodents. Typically, experimental infections employ an artificially high, single bolus of parasites that leads to rapid expulsion of the primary infection and robust immunity to subsequent challenges. However, immunity in natura is generated slowly, and is only partially effective, with individuals in endemic areas retaining low-level infections throughout their lives. Therefore, there is a gap between traditional model STH systems and observations in the field. Here, we review the immune response to traditional model STH infections in the laboratory. We compare these data to studies of natural infection in humans and rodents in endemic areas, highlighting crucial differences between experimental and natural infection. We then detail the literature to date on the use of "trickle" infections to experimentally model the kinetics of natural infection.

The conundrum of colonization resistance against Campylobacter reloaded: The gut microbota composition in conventional mice does not prevent from Campylobacter coli infection

The physiological colonization resistance exerted by the murine gut microbiota prevents conventional mice from Campylobacter jejuni infection. In the present study we addressed whether this also held true for Campylobacter coli. Following peroral application, C. coli as opposed to C.jejuni could stably establish within the gastrointestinal tract of conventionally colonized mice until 3 weeks post-challenge. Neither before nor after either Campylobacter application any changes in the gut microbiota composition could be observed. C. coli, but not C. jejuni challenge was associated with pronounced regenerative, but not apoptotic responses in colonic epithelia. At day 21 following C. coli versus C. jejuni application mice exhibited higher numbers of adaptive immune cells including T-lymphocytes and regulatory T-cells in the colonic mucosa and lamina propria that were accompanied by higher large intestinal interferon-γ (IFN-γ) concentrations in the former versus the latter but comparable to naive levels. Campylobacter application resulted in decreased splenic IFN-γ, tumor necrosis factor-α (TNF-α), and IL-6 concentrations, whereas IL-12p70 secretion was increased in the spleens at day 21 following C. coli application only. In either Campylobacter cohort decreased IL-10 concentrations could be measured in splenic and serum samples. In conclusion, the commensal gut microbiota prevents mice from C. jejuni, but not C. coli infection.

Murine fecal microbiota transplantation lowers gastrointestinal pathogen loads and dampens pro-inflammatory immune responses in Campylobacter jejuni infected secondary abiotic mice

Conventional mice are protected from Campylobacter jejuni infection by the murine host-specific gut microbiota composition. We here addressed whether peroral fecal microbiota transplantation (FMT) might be an antibiotics-independent option to lower even high gastrointestinal C. jejuni loads in the infected vertebrate host. To address this, secondary abiotic mice were generated by broad-spectrum antibiotic treatment and perorally infected with C. jejuni by gavage. One week later, mice were stably colonized with more than 109 C. jejuni and subjected to peroral FMT from murine donors on three consecutive days. Two weeks post-intervention, gastrointestinal C. jejuni loads were up to 7.5 orders of magnitude lower following murine FMT versus mock challenge. Remarkably, FMT reversed C. jejuni induced colonic epithelial apoptosis, but enhanced proliferative and regenerative responses in the colon thereby counteracting pathogenic cell damage. Furthermore, FMT dampened both, innate and adaptive immune cell responses in the large intestines upon C. jejuni infection that were accompanied by less C. jejuni-induced colonic nitric oxide secretion. Our study provides strong evidence that novel probiotic formulations developed as alternative option to FMT in severe intestinal inflammatory morbidities including Clostridoides difficile infection might be effective to treat campylobacteriosis and lower pathogen loads in colonized vertebrates including farm animals.

Infection with a small intestinal helminth, Heligmosomoides polygyrus bakeri, consistently alters microbial communities throughout the murine small and large intestine

Increasing evidence suggests that intestinal helminth infection can alter intestinal microbial communities with important impacts on the mammalian host. However, all of the studies to date utilize different techniques to study the microbiome and access different sites of the intestine with little consistency noted between studies. In the present study, we set out to perform a comprehensive analysis of the impact of intestinal helminth infection on the mammalian intestinal bacterial microbiome. For this purpose, we investigated the impact of experimental infection using the natural murine small intestinal helminth, Heligmosomoides polygyrus bakeri and examined possible alterations in both the mucous and luminal bacterial communities along the entire small and large intestine. We also explored the impact of common experimental variables including the parasite batch and pre-infection microbiome, on the outcome of helminth-bacterial interactions. This work provides evidence that helminth infection reproducibly alters intestinal microbial communities, with an impact of infection noted along the entire length of the intestine. Although the exact nature of helminth-induced alterations to the intestinal microbiome differed depending on the microbiome community structure present prior to infection, changes extended well beyond the introduction of new bacterial species by the infecting larvae. Moreover, striking similarities between different experiments were noted, including the consistent outgrowth of a bacterium belonging to the Peptostreptococcaceae family throughout the intestine.

Trichinella spiralis infection decreases the diversity of the intestinal flora in the infected mouse

BACKGROUND

Trichinella spiralis is a kind of intestinal nematode that can strongly modulate the host immune system. However, the effects of T. spiralis infection on the intestinal flora are poorly understood. This study aimed to explore the effect of T. spiralis infection on the intestinal flora.

METHODS

The intestinal contents of T. spiralis infected mice were examined through high-throughput sequencing (Illumina) of the V3-V4 hypervariable region in bacterial 16S rRNA gene. The sequences were analyzed using the QIIME software package and other bioinformatics methods.

RESULTS

Altogether 2,899,062 sequences were generated from the samples collected from different intestinal regions at various infection time points; the 44,843 Operational Taxonomic Unit (OTUs) analysis showed that T. spiralis infection would decrease the diversity of intestinal flora in the infected mice relative to that in the uninfected ones, especially in the large intestine and feces. Further analysis indicated that, the genera Oscillospira from the phylum Firmicutes showed a higher abundance in the helminth-infected small and larger intestines; the genera Bacteroides from the phyla Bacteroides, the genera Lactobacillus from the phyla Firmicutes, the genera Escherichia from the phyla Proteobacteria, and the genera Akkermansia from the phyla Verrucomicrobia displayed increased abundances in the T. spiralis positive fecal samples compared with those in the negative samples.

CONCLUSIONS

T. spiralis infection decreases the diversity of the intestinal flora in the infected mouse. However, it remains unclear about the association between the changes in intestinal flora caused by T. spiralis infection and the parasite pathogenesis, which should be further examined.

Gastrointestinal investigation of parasites and Enterobacteriaceae in loggerhead sea turtles from Italian coasts

Background

Caretta caretta is the most abundant sea turtle species in the Mediterranean, and studies on this species have vastly expanded during recent years, including those investigating gut bacterial and parasitic communities. Members of these communities have been reported with variable prevalence and pathogenicity, mainly depending on their host and environment (e.g. lifespan, distribution, habitat, diet, health status and stressors). Indeed, many species commonly inhabiting the sea turtle gastrointestinal tract exhibit an opportunistic behaviour.

This study aimed to provide baseline data on enterobacterial and parasitic composition, through bacteriological culture-based methods and the FLOTAC parasitological technique, in cloacal and faecal samples of 30 live Caretta caretta, examined upon their arrival at the Marine Turtle Research Centre (Portici, Italy).

Results

Enterobacteriaceae were isolated in 18/23 cloacal samples (78.3%), with Citrobacter and Morganella as the most common genera, followed by Proteus, Enterobacter, Providencia, and Hafnia. Parasitic elements were detected in 11/30 faecal samples (36.7%), with Enodiotrema, Rhytidodes, and Eimeria as most common genera, followed by Pachypsolus and Cymatocarpus. Additionally, Angiodyctium is reported for the first time in this host. The majority (47.8%) of sea turtles hosted exclusively Enterobacteriaceae, whereas 30.4% hosted both parasites and Enterobacteriaceae; the remaining 21.8% hosted neither of the agents.

Conclusions

Bacteria and parasites evaluated in the present study are common in Mediterranean loggerhead sea turtles, with slight differences between the western and eastern basin. Although naturally present in the gastrointestinal system of free-living sea turtles, their relationship with these hosts might range from mutualism to parasitism. Indeed, members of the gut community might express their pathogenic potential in immune-compromised animals, such as those in rehabilitation facilities. Therefore, it is advisable to include in the standard work-up of rescued sea turtles a screening procedure for such opportunistic agents, in order to better evaluate the animal’s health status and achieve timely intervention with appropriate treatment, thus improving rehabilitation. Furthermore, data collected from free-living sea turtles represent a starting point for investigating wild populations. However, further studies are needed to clarify the differences between sea turtle’s normal gut microbiome and pathobiome.

Murine Fecal Microbiota Transplantation Alleviates Intestinal and Systemic Immune Responses in Campylobacter jejuni Infected Mice Harboring a Human Gut Microbiota

Human campylobacteriosis constitutes a zoonotic food-borne disease and a progressively rising health burden of significant socioeconomic impact. We have recently shown that conventional mice are protected from Campylobacter jejuni infection, which was not the case for human microbiota associated (hma) mice indicating that the host-specific gut microbiota composition primarily determines susceptibility to or resistance against C. jejuni infection. In our present preclinical intervention study we addressed whether gut microbiota changes in stably C. jejuni infected hma mice following murine fecal microbiota transplantation (mFMT) could alleviate pathogen-induced immune responses. To accomplish this, secondary abiotic C57BL/6 mice were generated by broad-spectrum antibiotic treatment, perorally reassociated with a complex human gut microbiota and challenged with C. jejuni by gavage. Seven days later C. jejuni infected hma mice were subjected to peroral mFMT on 3 consecutive days. Within a week post-mFMT fecal pathogenic burdens had decreased by two orders of magnitude, whereas distinct changes in the gut microbiota composition with elevated numbers of lactobacilli and bifidobacteria could be assessed. In addition, mFMT resulted in less C. jejuni induced apoptotic responses in colonic epithelia, reduced numbers of macrophages and monocytes as well as of T lymphocytes in the large intestinal mucosa and lamina propria and in less distinct intestinal pro-inflammatory cytokine secretion as compared to mock challenge. Strikingly, inflammation dampening effects of mFMT were not restricted to the intestinal tract, but could also be observed systemically as indicated by elevated serum concentrations of pro-inflammatory cytokines such as TNF-α, IL-12p70, and IL-6 in C. jejuni infected hma mice of the mock, but not the mFMT cohort. In conclusion, our preclinical mFMT intervention study provides evidence that changes in the gut microbiota composition which might be achieved by pre- or probiotic formulations may effectively lower intestinal C. jejuni loads, dampen both, pathogen-induced intestinal and systemic inflammatory sequelae and may represent a useful tool to treat continuous shedding of C. jejuni by asymptomatic carriers which is critical in the context of food production, hospitalization and immunosuppression.

Helminth-microbiota cross-talk - A journey through the vertebrate digestive system

The gastrointestinal (GI) tract of vertebrates is inhabited by a vast array of organisms, i.e., the microbiota and macrobiota. The former is composed largely of commensal microorganisms, which play vital roles in host nutrition and maintenance of energy balance, in addition to supporting the development and function of the vertebrate immune system. By contrast, the macrobiota includes parasitic helminths, which are mostly considered detrimental to host health via a range of pathogenic effects that depend on parasite size, location in the GI tract, burden of infection, metabolic activity, and interactions with the host immune system. Sharing the same environment within the vertebrate host, the GI microbiota and parasitic helminths interact with each other, and the results of such interactions may impact, directly or indirectly, on host health and homeostasis. The complex relationships occurring between parasitic helminths and microbiota have long been neglected; however, recent studies point towards a role for these interactions in the overall pathophysiology of helminth disease, as well as in parasite-mediated suppression of inflammation. Whilst several discrepancies in qualitative and quantitative modifications in gut microbiota composition have been described based on host and helminth species under investigation, we argue that attention should be paid to the systems biology of the gut compartment under consideration, as variations in the abundances of the same population of bacteria inhabiting different niches of the GI tract may result in varying functional consequences for host physiology.

Helminths and microbes within the vertebrate gut - not all studies are created equal

The multifaceted interactions occurring between gastrointestinal (GI) parasitic helminths and the host gut microbiota are emerging as a key area of study within the broader research domain of host-pathogen relationships. Over the past few years, a wealth of investigations has demonstrated that GI helminths interact with the host gut flora, and that such interactions result in modifications of the host immune and metabolic statuses. Nevertheless, whilst selected changes in gut microbial composition are consistently observed in response to GI helminth infections across several host-parasite systems, research in this area to date is largely characterised by inconsistent findings. These discrepancies are particularly evident when data from studies of GI helminth-microbiota interactions conducted in humans from parasite-endemic regions are compared. In this review, we provide an overview of the main sources of variance that affect investigations on helminth-gut microbiota interactions in humans, and propose a series of methodological approaches that, whilst accounting for the inevitable constraints of fieldwork, are aimed at minimising confounding factors and draw biologically meaningful interpretations from highly variable datasets.

Sequential Changes in the Host Gut Microbiota During Infection With the Intestinal Parasitic Nematode Strongyloides venezuelensis

Soil-transmitted helminths (STHs) are medically important parasites that infect 1. 5 billion humans globally, causing a substantial disease burden. These parasites infect the gastrointestinal tract (GIT) of their host where they co-exist and interact with the host gut bacterial flora, leading to the coevolution of the parasites, microbiota, and host organisms. However, little is known about how these interactions change through time with the progression of infection. Strongyloidiasis is a human parasitic disease caused by the nematode Strongyloides stercoralis infecting 30-100 million people. In this study, we used a closely related rodent parasite Strongyloides venezuelensis and mice as a model of gastrointestinal parasite infection. We conducted a time-course experiment to examine changes in the fecal microbiota from the start of infection to parasite clearance. We found that bacterial taxa in the host intestinal microbiota changed significantly as the infection progressed, with an increase in the genera Bacteroides and Candidatus Arthromitus, and a decrease in Prevotella and Rikenellaceae. However, the microbiota recovered to the pre-infective state after parasite clearance from the host, suggesting that these perturbations are reversible. Microarray analysis revealed that this microbiota transition is likely to correspond with the host immune response. These findings give us an insight into the dynamics of parasite-microbiota interactions in the host gut during parasite infection.

Effect of intestinal tapeworms on the gut microbiota of the common carp, Cyprinus carpio

BACKGROUND

Parasitic protozoans, helminths, alter the gut microbiota in mammals, yet little is known about the influence of intestinal cestodes on gut microbiota in fish. In the present study, the composition and diversity of the hindgut microbiota were determined in the intestine of common carp (Cyprinus carpio) infected with two tapeworm species, Khawia japonensis and Atractolytocestus tenuicollis.

RESULTS

The intestine contained a core microbiota composed of Proteobacteria, Fusobacteria and Tenericutes. Infection with the two cestode species had no significant effect on the microbial diversity and richness, but it altered the microbial composition at the genus level. PCoA analysis indicated that microbial communities in the infected and uninfected common carp could not be distinguished from each other. However, a Mantel test indicated that the abundance of K. japonensis was significantly correlated with the microbial composition (P = 0.015), while the abundance of A. tenuicollis was not (P = 0.954). According to Pearson's correlation analysis, the abundance of K. japonensis exhibited an extremely significant (P < 0.001) positive correlation with the following gut microbiota taxa: Epulopiscium, U114, Bacteroides, Clostridium and Peptostreptococcaceae (0.8< r < 0.9); and a significant (P < 0.05) correlation with Enterobacteriaceae, Micrococcaceae, Rummeliibacillus, Lysinibacillus boronitolerans, Veillonellaceae, Oxalobacteraceae, Aeromonadaceae (negative), Marinibacillus and Chitinilyticum (0.4< r < 0.7).

CONCLUSIONS

These results suggest that the composition of gut microbiota was somewhat affected by the K. japonensis infection. Additionally, increased ratios of pathogenic bacteria (Lawsonia and Plesiomonas) were also associated with the K. japonensis infection, which may therefore increase the likelihood of disease.

The Impact of Anthelmintic Treatment on Human Gut Microbiota Based on Cross-Sectional and Pre- and Postdeworming Comparisons in Western Kenya

Murine studies suggest that the presence of some species of intestinal helminths is associated with changes in host microbiota composition and diversity. However, studies in humans have produced varied conclusions, and the impact appears to vary widely depending on the helminth species present. To demonstrate how molecular approaches to the human gut microbiome can provide insights into the complex interplay among disparate organisms, DNA was extracted from cryopreserved stools collected from residents of 5 rural Kenyan villages prior to and 3 weeks and 3 months following albendazole (ALB) therapy. Samples were analyzed by quantitative PCR (qPCR) for the presence of 8 species of intestinal parasites and by MiSeq 16S rRNA gene sequencing. Based on pretreatment results, the presence of neither Ascaris lumbricoides nor Necator americanus infection significantly altered the overall diversity of the microbiota in comparison with age-matched controls. Following ALB therapy and clearance of soil-transmitted helminths (STH), there were significant increases in the proportion of the microbiota made up by Clostridiales (P = 0.0002; average fold change, 0.57) and reductions in the proportion made up by Enterobacteriales (P = 0.0004; average fold change, -0.58). There was a significant posttreatment decrease in Chao1 richness, even among individuals who were uninfected pretreatment, suggesting that antimicrobial effects must be considered in any posttreatment setting. Nevertheless, the helminth-associated changes in Clostridiales and Enterobacteriales suggest that clearance of STH, and of N. americanus in particular, alters the gut microbiota.IMPORTANCE The gut microbiome is an important factor in human health. It is affected by what we eat, what medicines we take, and what infections we acquire. In turn, it affects the way we absorb nutrients and whether we have excessive intestinal inflammation. Intestinal worms may have an important impact on the composition of the gut microbiome. Without a complete understanding of the impact of mass deworming programs on the microbiome, it is impossible to accurately calculate the cost-effectiveness of such public health interventions and to guard against any possible deleterious side effects. Our research examines this question in a "real-world" setting, using a longitudinal cohort, in which individuals with and without worm infections are treated with deworming medication and followed up at both three weeks and three months posttreatment. We quantify the impact of roundworms and hookworms on gut microbial composition, suggesting that the impact is small, but that treatment of hookworm infection results in significant changes. This work points to the need for follow-up studies to further examine the impact of hookworm on the gut microbiota and determine the health consequences of the observed changes.

Comprehensive Kinetic Survey of Intestinal, Extra-Intestinal and Systemic Sequelae of Murine Ileitis Following Peroral Low-Dose Toxoplasma gondii Infection

We have recently shown that following peroral low-dose Toxoplasma gondii infection susceptible mice develop subacute ileitis within 10 days. Data regarding long-term intestinal and extra-intestinal sequelae of infection are scarce, however. We therefore challenged conventional C57BL/6 mice with one cyst of T. gondii ME49 strain by gavage and performed a comprehensive immunopathological survey 10, 36, and 57 days later. As early as 10 days post-infection, mice were suffering from subacute ileitis as indicated by mild-to-moderate histopathological changes of the ileal mucosa. Furthermore, numbers of apoptotic and proliferating/regenerating epithelial cells as well as of T and B lymphocytes in the mucosa and lamina propria of the ileum were highest at day 10 post-infection, but declined thereafter, and were accompanied by enhanced pro-inflammatory mediator secretion in ileum, colon and mesenteric lymph nodes that was most pronounced during the early phase of infection. In addition, subacute ileitis was accompanied by distinct shifts in the commensal gut microbiota composition in the small intestines. Remarkably, immunopathological sequelae of T. gondii infection were not restricted to the intestines, but could also be observed in extra-intestinal tissues including the liver, kidneys, lungs, heart and strikingly, in systemic compartments that were most prominent at day 10 post-infection. We conclude that the here provided long-term kinetic survey of immunopathological sequalae following peroral low-dose T. gondii infection provides valuable corner stones for a better understanding of the complex interactions within the triangle relationship of (parasitic) pathogens, the host immunity and the commensal gut microbiota during intestinal inflammation. The low-dose T. gondii infection model may be applied as valuable gut inflammation model in future pre-clinical studies in order to test potential treatment options for intestinal inflammatory conditions in humans.

Removal of adult cyathostomins alters faecal microbiota and promotes an inflammatory phenotype in horses

The interactions between parasitic helminths and gut microbiota are considered to be an important, although as yet incompletely understood, factor in the regulation of immunity, inflammation and a range of diseases. Infection with intestinal helminths is ubiquitous in grazing horses, with cyathostomins (about 50 species of which are recorded) predominating. Consequences of infection include both chronic effects, and an acute inflammatory syndrome, acute larval cyathostominosis, which sometimes follows removal of adult helminths by administration of anthelmintic drugs. The presence of cyathostomins as a resident helminth population of the equine gut (the "helminthome") provides an opportunity to investigate the effect helminth infection, and its perturbation, has on both the immune system and bacterial microbiome of the gut, as well as to determine the specific mechanisms of pathophysiology involved in equine acute larval cyathostominosis. We studied changes in the faecal microbiota of two groups of horses following treatment with anthelmintics (fenbendazole or moxidectin). We found decreases in both alpha diversity and beta diversity of the faecal microbiota at Day 7 post-treatment, which were reversed by Day 14. These changes were accompanied by increases in inflammatory biomarkers. The general pattern of faecal microbiota detected was similar to that seen in the relatively few equine gut microbiome studies reported to date. We conclude that interplay between resident cyathostomin populations and the bacterial microbiota of the equine large intestine is important in maintaining homeostasis and that disturbance of this ecology can lead to gut dysbiosis and play a role in the aetiology of inflammatory conditions in the horse, including acute larval cyathostominosis.

The therapeutic prospect of crosstalk between prokaryotic and eukaryotic organisms in the human gut

The peaceful phenomenon of the co-evolution between the prokaryotes (microbiota) and the eukaryotes (parasites including protozoa and helminths) in the animal gut has drawn the researchers' attention. Importantly, exploring the potential of helminths for therapeutic uses was one of the reasons behind understanding the physiological and immunological crosstalk existing between them. Here we discuss the interactive immunological associations of helminths and microbial responses individually and in combination with their hosts. Considering that there is probably crosstalk between eukaryotic organisms like helminths and protozoa with their host's gut microbiota, in this review we searched the literature identifying the privileged and favourable relationship generated between them in the host. Understanding the possibilities of the role of helminths along with gut microbiota as a black box would certainly help decode the therapeutic intrusion with helminths in experimental clinical trials, and a successful trial could be used to consider possible future and safe treatments for various immune-inflammatory diseases in humans.

Pituitary Adenylate Cyclase-Activating Polypeptide-A Neuropeptide as Novel Treatment Option for Subacute Ileitis in Mice Harboring a Human Gut Microbiota

The neuropeptide Pituitary adenylate cyclase-activating polypeptide (PACAP) is well-known for its important functions in immunity and inflammation. Data regarding anti-inflammatory properties of PACAP in the intestinal tract are limited, however. In our present preclinical intervention study we addressed whether PACAP treatment could alleviate experimental subacute ileitis mimicking human gut microbiota conditions. Therefore, secondary abioitic mice were subjected to human fecal microbiota transplantation (FMT) and perorally infected with low-dose Toxoplasma gondii to induce subacute ileitis on day 0. From day 3 until day 8 post-infection, mice were either treated with synthetic PACAP38 or placebo. At day 9 post-infection, placebo, but not PACAP treated mice exhibited overt macroscopic sequelae of intestinal immunopathology. PACAP treatment further resulted in less distinct apoptotic responses in ileal and colonic epithelia that were accompanied by lower T cell numbers in the mucosa and lamina propria and less secretion of pro-inflammatory cytokines in intestinal ex vivo biopsies. Notably, ileitis-associated gut microbiota shifts were less distinct in PACAP as compared to placebo treated mice. Inflammation-ameliorating effects of PACAP were not restricted to the intestines, but could also be observed in extra-intestinal including systemic compartments as indicated by lower apoptotic cell counts and less pro-inflammatory cytokine secretion in liver and lungs taken from PACAP treated as compared to placebo control mice, which also held true for markedly lower serum TNF and IL-6 concentrations in the former as compared to the latter. Our preclinical intervention study provides strong evidence that synthetic PACAP alleviates subacute ileitis and extra-intestinal including systemic sequelae of T cell-driven immunopathology. These findings further support PACAP as a novel treatment option for intestinal inflammation including inflammatory bowel diseases (IBD).

A Novel Non-invasive Method to Detect RELM Beta Transcript in Gut Barrier Related Changes During a Gastrointestinal Nematode Infection

Currently, methods for monitoring changes of gut barrier integrity and the associated immune response via non-invasive means are limited. Therefore, we aimed to develop a novel non-invasive technique to investigate immunological host responses representing gut barrier changes in response to infection. We identified the mucous layer on feces from mice to be mainly composed of exfoliated intestinal epithelial cells. Expression of RELM-β, a gene prominently expressed in intestinal nematode infections, was used as an indicator of intestinal cellular barrier changes to infection. RELM-β was detected as early as 6 days post-infection (dpi) in exfoliated epithelial cells. Interestingly, RELM-β expression also mirrored the quality of the immune response, with higher amounts being detectable in a secondary infection and in high dose nematode infection in laboratory mice. This technique was also applicable to captured worm-infected wild house mice. We have therefore developed a novel non-invasive method reflecting gut barrier changes associated with alterations in cellular responses to a gastrointestinal nematode infection.