Impact of Experimental Hookworm Infection on the Human Gut Microbiota

The interactions between gastrointestinal parasitic helminths and commensal bacteria are likely to play a pivotal role in the establishment of host-parasite cross-talk, ultimately shaping the development of the intestinal immune system. However, little information is available on the impact of infections by gastrointestinal helminths on the bacterial communities inhabiting the human gut. We used 16S rRNA gene amplification and pyrosequencing to characterize, for the first time to our knowledge, the differences in composition and relative abundance of fecal microbial communities in human subjects prior to and following experimental infection with the blood-feeding intestinal hookworm, Necator americanus. Our data show that, although hookworm infection leads to a minor increase in microbial species richness, no detectable effect is observed on community structure, diversity or relative abundance of individual bacterial species

Suppression of inflammation by helminths: a role for the gut microbiota?

Multiple recent investigations have highlighted the promise of helminth-based therapies for the treatment of inflammatory disorders of the intestinal tract of humans, including inflammatory bowel disease and coeliac disease. However, the mechanisms by which helminths regulate immune responses, leading to the amelioration of symptoms of chronic inflammation are unknown. Given the pivotal roles of the intestinal microbiota in the pathogenesis of these disorders, it has been hypothesized that helminth-induced modifications of the gut commensal flora may be responsible for the therapeutic properties of gastrointestinal parasites. In this article, we review recent progress in the elucidation of host-parasite-microbiota interactions in both animal models of chronic inflammation and humans, and provide a working hypothesis of the role of the gut microbiota in helminth-induced suppression of inflammation.Funding from the Isaac Newton Trust / Wellcome Trust ISSF / University of Cambridge Joint Research Grants Scheme (C.C.) and the Australian National Health and Medical Research Council (NHMRC) grants 1037304, 1020114 (A.L.), 1052938 (C.C.) and 613718 (P.G.) is gratefully acknowledged.This is the final version of the article. It first appeared from Royal Society Publishing via http://dx.doi.org/10.1098/rstb.2014.029

Not All Worms Were Created Equal

[Extract] Whilst we support the need to report safety outcomes from experimental therapy of any kind, including the use of helminths as therapy, we believe that it is important to critically examine the causal relationship of the reported event to the proposed etiology so that a balanced view of the cause and effect be arrived at. This is particularly the case in an uncontrolled setting where formal processes for documenting and reporting experimental therapy may not be in place. Recent reviews of studies with one of the most widely used helminths, the anthropophilic hookworm, Necator americanus, have shown this helminth to be safe and well tolerated in hundreds of individuals by numerous research groups across Australia, the US and Europe (1–3). In BMC Pulmonary Medicine (4), Zeynalyan and colleagues report rapidly progressive respiratory failure in a patient with significant comorbidities, including systemic sclerosis, interstitial lung disease and pulmonary hypertension after self-administration of N. americanus larvae that were purchased over the internet. Here we raise some concerns about this report

Suppression of inflammation and tissue damage by a hookworm recombinant protein in experimental colitis

Gastrointestinal parasites, hookworms in particular, have evolved to cause minimal harm to their hosts when present in small numbers, allowing them to establish chronic infections for decades. They do so by creating an immunoregulatory environment that promotes their own survival, but paradoxically also benefits the host by protecting against the onset of many inflammatory diseases. To harness the therapeutic value of hookworms without using live parasites, we have examined the protective properties of the recombinant protein anti-inflammatory protein (AIP)-1, secreted in abundance by hookworms within the intestinal mucosa, in experimental colitis. Colitic inflammation assessed by weight loss, colon atrophy, oedema, ulceration and necrosis, as well as abdominal adhesion was significantly suppressed in mice treated with a single intraperitoneal dose of AIP-1 at 1 mg kg(-1). Local infiltration of inflammatory cells was also significantly reduced, with minimal goblet cell loss and preserved mucosal architecture. Treatment with AIP-1 promoted the production of colon interleukin (IL)-10, transforming growth factor (TGF)-beta and thymic stromal lymphopoietin (TSLP), resulting in the suppression of tumour necrosis factor (TNF)-alpha, IL-13 and IL-17 A cytokines and granulocyte macrophage colony-stimulating factor (GM-CSF), CX motif chemokine ( CXCL)-11 and cyclooxygenase synthase (COX)-2 mRNA transcripts. AIP-1 promoted the accumulation of regulatory T cells in the colon likely allowing rapid healing of the colon mucosa. Hookworm recombinant AIP-1 is a novel therapeutic candidate for the treatment of inflammatory bowel diseases that can be explored for the prevention of acute inflammatory relapses, an important cause of colorectal cancer

Safety and tolerability of experimental hookworm infection in humans with metabolic disease: study protocol for a phase 1b randomised controlled clinical trial

Background: Abdominal obesity and presence of the metabolic syndrome (MetS) significantly increase the risk of developing diseases such as Type 2 diabetes mellitus (T2DM) with escalating emergence of MetS and T2DM constituting a significant public health crisis worldwide. Lower prevalence of inflammatory and metabolic diseases such as T2DM in countries with higher incidences of helminth infections suggested a potential role for these parasites in the prevention and management of certain diseases. Recent studies confirmed the potential protective nature of helminth infection against MetS and T2DM via immunomodulation or, potentially, alteration of the intestinal microbiota. This Phase 1b safety and tolerability trial aims to assess the effect of inoculation with helminths on physical and metabolic parameters, immune responses, and the microbiome in otherwise healthy women and men. Methods: Participants eligible for inclusion are adults aged 18–50 with central obesity and a minimum of one additional feature of MetS recruited from the local community with a recruitment target of 54. In a randomised, double-blind, placebo-controlled design, three groups will receive either 20 or 40 stage three larvae of the human hookworm Necator americanus or a placebo. Eligible participants will provide blood and faecal samples at their baseline and 6-monthly assessment visits for a total of 24 months with an optional extension to 36 months. During each scheduled visit, participants will also undergo a full physical examination and complete diet (PREDIMED), physical activity, and patient health (PHQ-9) questionnaires. Outcome measurements include tolerability and safety of infection with Necator americanus, changes in metabolic and immunological parameters, and changes in the composition of the faecal microbiome. Discussion: Rising cost of healthcare associated with obesity-induced metabolic diseases urgently calls for new approaches in disease prevention. Findings from this trial will provide valuable information regarding the potential mechanisms by which hookworms, potentially via alterations in the microbiota, may positively influence metabolic health

Experimental hookworm infection and escalating gluten challenges are associated with increased microbial richness in celiac subjects.

The intestinal microbiota plays a critical role in the development of the immune system. Recent investigations have highlighted the potential of helminth therapy for treating a range of inflammatory disorders, including celiac disease (CeD); however, the mechanisms by which helminths modulate the immune response of the human host and ameliorate CeD pathology are unknown. In this study, we investigated the potential role of alterations in the human gut microbiota in helminth-mediated suppression of an inflammatory disease. We assessed the qualitative and quantitative changes in the microbiota of human volunteers with CeD prior to and following infection with human hookworms, and following challenge with escalating doses of dietary gluten. Experimental hookworm infection of the trial subjects resulted in maintenance of the composition of the intestinal flora, even after a moderate gluten challenge. Notably, we observed a significant increase in microbial species richness over the course of the trial, which could represent a potential mechanism by which hookworms can regulate gluten-induced inflammation and maintain intestinal immune homeostasis.This work was supported by grants 1052938 to C.C., 613718 to P.G., and 1037304 and 1020114 to A.L. from the National Health and Medical Research Council of Australia (NHMRC), and from James Cook University (FMHMS 2013 grants round) and the Isaac Newton Trust / Wellcome Trust ISSF / University of Cambridge Joint Research Grants Scheme to C.C.This is the final version of the article. It first appeared from NPG via http://dx.doi.org/10.1038/srep1379

The Intestinal Microbiota Contributes to the Ability of Helminths to Modulate Allergic Inflammation

We thank Manuel Kulagin for technical help, Pierre Bonnaventure for portal vein blood sampling, Francisco Sepulveda for technical assistance in GS-MS acquisition, and Dorothee Hahne (Metabolomics Australia, University of Western Australia) for human samples SCFA isolation, acquisition, and analysis. We also thank Cristina Cartoni (Phenotyping Unit, EPFL) for Milliplex analysis, Jessica Dessimoz and her team from the Histology Core Facility (EPFL), Miguel Garcia and his team from the Flow Cytometry Core Facility (EPFL), and staff from the EPFL CPG animal house for excellent animal care. The computations were partially performed at the Vital-IT Center for high-performance computing of the SIB Swiss Institute of Bioinformatics (http://www.vital-it.ch). The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement n. 310948. Funding for A.W.W. and a subset of the 16S rRNA gene sequencing was provided by the Wellcome Trust (grant number WT 098051). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD

Changes in duodenal tissue-associated microbiota following hookworm infection and consecutive gluten challenges in humans with coeliac disease

A reduced diversity of the gastrointestinal commensal microbiota is associated with the development of several inflammatory diseases. Recent reports in humans and animal models have demonstrated the beneficial therapeutic effects of infections by parasitic worms (helminths) in some inflammatory disorders, such as inflammatory bowel disease (IBD) and coeliac disease (CeD). Interestingly, these studies have described how helminths may alter the intestinal microbiota, potentially representing a mechanism by which they regulate inflammation. However, for practical reasons, these reports have primarily analysed the faecal microbiota. In the present investigation, we have assessed, for the first time, the changes in the microbiota at the site of infection by a parasitic helminth (hookworm) and gluten-dependent inflammation in humans with CeD using biopsy tissue from the duodenum. Hookworm infection and gluten exposure were associated with an increased abundance of species within the Bacteroides phylum, as well as increases in the richness and diversity of the tissue-resident microbiota within the intestine, results that are consistent with previous reports using other helminth species in humans and animal models. Hence, this may represent a mechanism by which parasitic helminths may restore intestinal immune homeostasis and exert a therapeutic benefit in CeD, and potentially other inflammatory disorders

Symptoms after Ingestion of Pig Whipworm Trichuris suis Eggs in a Randomized Placebo-Controlled Double-Blind Clinical Trial

Symptoms after human infection with the helminth Trichuris suis have not previously been described. Exposure to helminths has been suggested as immune therapy against allergy and autoimmune diseases. We randomized adults with allergic rhinitis to ingest a dose of 2500 T. suis eggs or placebo every 21 days for 168 days (total 8 doses) in a double-blind clinical trial. In a previous publication, we reported a lack of efficacy and a high prevalence of adverse gastrointestinal reactions. The aim of the present study was to present a detailed description of the adverse event data and post-hoc analyses of gastrointestinal reactions. Adverse events and severity (mild, moderate, severe) were recorded daily by subjects, classified by organ using MedDRA 10.0, and event rates compared between subjects on T. suis treatment vs. subjects on placebo. T. suis-specific serum IgG antibodies were measured by a fluoroenzymeimmunoassay (Phadia ApS). During 163 days complete follow-up, subjects ingesting T. suis eggs (N = 49) had a three to 19-fold higher rate of events (median duration, 2 days) with gastrointestinal reactions (moderate to severe flatulence, diarrhea, and upper abdominal pain) compared with placebo subjects (N = 47). The highest incidence of affected subjects was seen from the first few days and until day 42 (3rd dose): 63% vs. 29% for placebo; day 163: 76% vs. 49% for placebo. Seroprevalences increased concurrently in the T. suis group: Day 59, 50%; day 90, 91%; day 170, 93%. The combined duration of episodes with onset before day 42 was ≤14 days in 80% of affected subjects. Age, gender, total IgE, and recent intestinal symptoms at baseline did not predict gastrointestinal side effects. In conclusion, during the first 2 months, repeated ingestions of 2500 T. suis eggs caused frequent gastrointestinal reactions lasting up to 14 days, whereas 4 months further treatment mainly provoked a subclinical stimulation

Effect of Hookworm Infection on Wheat Challenge in Celiac Disease – A Randomised Double-Blinded Placebo Controlled Trial

Background and Aims: The association between hygiene and prevalence of autoimmune disease has been attributed in part to enteric helminth infection. A pilot study of experimental infection with the hookworm Necator americanus was undertaken among a group of otherwise healthy people with celiac disease to test the potential of the helminth to suppress the immunopathology induced by gluten