Metabolomes and Lipidomes of the Infective Stages of the Gastrointestinal nematodes, Nippostrongylus brasiliensis and Trichuris muris

A genome-scale metabolic model of parasitic whipworm

Genome-scale metabolic models are widely used to enhance our understanding of metabolic features of organisms, host-pathogen interactions and to identify therapeutics for diseases. Here we present iTMU798, the genome-scale metabolic model of the mouse whipworm Trichuris muris. The model demonstrates the metabolic features of T. muris and allows the prediction of metabolic steps essential for its survival. Specifically, that Thioredoxin Reductase (TrxR) enzyme is essential, a prediction we validate in vitro with the drug auranofin. Furthermore, our observation that the T. muris genome lacks gsr-1 encoding Glutathione Reductase (GR) but has GR activity that can be inhibited by auranofin indicates a mechanism for the reduction of glutathione by the TrxR enzyme in T. muris. In addition, iTMU798 predicts seven essential amino acids that cannot be synthesised by T. muris, a prediction we validate for the amino acid tryptophan. Overall, iTMU798 is as a powerful tool to study not only the T. muris metabolism but also other Trichuris spp. in understanding host parasite interactions and the rationale design of new intervention strategies.

Metabolomic analysis reveals a differential adaptation process of the larval stages of Anisakis simplex to the host environment

Introduction: Anisakis simplex are parasitic nematodes that cause anisakiasis. The possibility of infection with this parasite is through consumption of raw or undercooked fish products. A. simplex infections are often misdiagnosed, especially in subclinical cases that do not present with typical symptoms such as urticaria, angioedema, and gastrointestinal allergy. The resulting allergic reactions range from rapid-onset and potentially fatal anaphylactic reactions to chronic, debilitating conditions. While there have been numerous published studies on the genomes and proteomes of A. simplex, less attention has been paid to the metabolomes. Metabolomics is concerned with the composition of metabolites in biological systems. Dynamic responses to endogenous and exogenous stimuli are particularly well suited for the study of holistic metabolic responses. In addition, metabolomics can be used to determine metabolic activity at different stages of development or during growth. Materials and methods: In this study, we reveal for the first time the metabolomes of infectious stages (L3 and L4) of A. simplex using untargeted metabolomics by ultra-performance liquid chromatography-mass spectrometry. Results: In the negative ionization mode (ESI-), we identified 172 different compounds, whereas in the positive ionization mode (ESI+), 186 metabolites were found. Statistical analysis showed that 60 metabolites were found in the ESI- mode with different concentration in each group, of which 21 were more enriched in the L3 larvae and 39 in the L4 stage of A. simplex. Comparison of the individual developmental stages in the ESI + mode also revealed a total of 60 differential metabolites, but 32 metabolites were more enriched in the L3 stage larvae, and 28 metabolites were more concentrated in the L4 stage. Discussion: The metabolomics study revealed that the developmental stages of A. simplex differed in a number of metabolic pathways, including nicotinate and nicotinamide metabolism. In addition, molecules responsible for successful migration within their host, such as pyridoxine and prostaglandins (E1, E2, F1a) were present in the L4 stage. In contrast, metabolic pathways for amino acids, starch, and sucrose were mainly activated in the L3 stage. Our results provide new insights into the comparative metabolome profiles of two different developmental stages of A. simplex.

Metabolomics and lipidomics studies of parasitic helminths: molecular diversity and identification levels achieved by using different characterisation tools

INTRODUCTION

Helminths are parasitic worms that infect millions of people worldwide and secrete a variety of excretory-secretory products (ESPs), including proteins, peptides, and small molecules. Despite this, there is currently no comprehensive review article on cataloging small molecules from helminths, particularly focusing on the different classes of metabolites (polar and lipid molecules) identified from the ESP and somatic tissue extracts of helminths that were studied in isolation from their hosts.

OBJECTIVE

This review aims to provide a comprehensive assessment of the metabolomics and lipidomics studies of parasitic helminths using all available analytical platforms.

METHOD

To achieve this objective, we conducted a meta-analysis of the identification and characterization tools, metabolomics approaches, metabolomics standard initiative (MSI) levels, software, and databases commonly applied in helminth metabolomics studies published until November 2021.

RESULT

This review analyzed 29 studies reporting the metabolomic assessment of ESPs and somatic tissue extracts of 17 helminth species grown under ex vivo/in vitro culture conditions. Of these 29 studies, 19 achieved the highest level of metabolite identification (MSI level-1), while the remaining studies reported MSI level-2 identification. Only 155 small molecule metabolites, including polar and lipids, were identified using MSI level-1 characterization protocols from various helminth species. Despite the significant advances made possible by the 'omics' technology, standardized software and helminth-specific metabolomics databases remain significant challenges in this field. Overall, this review highlights the potential for future studies to better understand the diverse range of small molecules that helminths produce and leverage their unique metabolomic features to develop novel treatment options.

How to train your myeloid cells: a way forward for helminth vaccines?

Soil-transmitted helminths affect approximately 1.5 billion people worldwide. However, as no vaccine is currently available for humans, the current strategy for elimination as a public health problem relies on preventive chemotherapy. Despite more than 20 years of intense research effort, the development of human helminth vaccines (HHVs) has not yet come to fruition. Current vaccine development focuses on peptide antigens that trigger strong humoral immunity, with the goal of generating neutralizing antibodies against key parasite molecules. Notably, this approach aims to reduce the pathology of infection, not worm burden, with only partial protection observed in laboratory models. In addition to the typical translational hurdles that vaccines struggle to overcome, HHVs face several challenges (1): helminth infections have been associated with poor vaccine responses in endemic countries, probably due to the strong immunomodulation caused by these parasites, and (2) the target population displays pre-existing type 2 immune responses to helminth products, increasing the likelihood of adverse events such as allergy or anaphylaxis. We argue that such traditional vaccines are unlikely to be successful on their own and that, based on laboratory models, mucosal and cellular-based vaccines could be a way to move forward in the fight against helminth infection. Here, we review the evidence for the role of innate immune cells, specifically the myeloid compartment, in controlling helminth infections. We explore how the parasite may reprogram myeloid cells to avoid killing, notably using excretory/secretory (ES) proteins and extracellular vesicles (EVs). Finally, learning from the field of tuberculosis, we will discuss how anti-helminth innate memory could be harnessed in a mucosal-trained immunity-based vaccine.

Untargeted Multimodal Metabolomics Investigation of the Haemonchus contortus Exsheathment Secretome

In nematodes that invade the gastro-intestinal tract of the ruminant, the process of larval exsheathment marks the transition from the free-living to the parasitic stages of these parasites. To investigate the secretome associated with larval exsheathment, a closed in vitro system that effectively reproduces the two basic components of an anaerobic rumen environment (CO2 and 39 °C) was developed to trigger exsheathment in one of the most pathogenic and model gastrointestinal parasitic nematodes, Haemonchus contortus (barber‘s pole worm). This study reports the use of multimodal untargeted metabolomics and lipidomics methodologies to identify the metabolic signatures and compounds secreted during in vitro larval exsheathment in the H. contortus infective third-stage larva (iL3). A combination of statistical and chemoinformatic analyses using three analytical platforms revealed a panel of metabolites detected post exsheathment and associated with amino acids, purines, as well as select organic compounds. The major lipid classes identified by the non-targeted lipidomics method applied were lysophosphatidylglycerols, diglycerides, fatty acyls, glycerophospholipids, and a triglyceride. The identified metabolites may serve as metabolic signatures to improve tractability of parasitic nematodes for characterizing small molecule host–parasite interactions related to pathogenesis, vaccine and drug design, as well as the discovery of metabolic biomarkers.

A multi-omics analysis for the prediction of neurocognitive disorders risk among the elderly in Macao

BACKGROUND

Due to the increasing ageing population, neurocognitive disorders (NCDs) have been a global public health issue, and its prevention and early diagnosis are crucial. Our previous study demonstrated that there is a significant correlation between specific populations and NCDs, but the biological characteristics of the vulnerable group predispose to NCDs are unclear. The purpose of this study is to investigate the predictors for the vulnerable group by a multi-omics analysis.

METHODS

Multi-omics approaches, including metagenomics, metabolomic and proteomic, were used to detect gut microbiota, faecal metabolites and urine exosome of 8 normal controls and 13 vulnerable elders after a rigorous screening of 400 elders in Macao. The multi-omics data were analysed using R and Bioconductor. The two-sided Wilcoxon's rank-sum test, Kruskal-Wallis rank sum test and the linear discriminant analysis effective size were applied to investigate characterized features. Moreover, a 2-year follow-up was conducted to evaluate cognitive function change of the elderly.

RESULTS

Compared with the control elders, the metagenomics of gut microbiota showed that Ruminococcus gnavus, Lachnospira eligens, Escherichia coli and Desulfovibrio piger were increased significantly in the vulnerable group. Carboxylates, like alpha-ketoglutaric acid and d-saccharic acid, and levels of vitamins had obvious differences in the faecal metabolites. There was a distinct decrease in the expression of eukaryotic translation initiation factor 2 subunit 1 (eIF2α) and amine oxidase A (MAO-A) according to the proteomic results of the urine exosomes. Moreover, the compound annual growth rate of neurocognitive scores was notably decreased in vulnerable elders.

CONCLUSIONS

The multi-omics characteristics of disturbed glyoxylate and dicarboxylate metabolism (bacteria), vitamin digestion and absorption and tricarboxylic acid cycle in vulnerable elders can serve as predictors of NCDs risk among the elderly of Macao. Intervention with them may be effective therapeutic approaches for NCDs, and the underlying mechanisms merit further exploration.

Metabolic alterations in Strongyloidiasis stool samples unveil potential biomarkers of infection

Strongyloidiasis, a parasitosis caused by Strongyloides stercoralis in humans, is a very prevalent infection in tropical or subtropical areas. Gaps on public health strategies corroborates to the high global incidence of strongyloidiasis especially due to challenges involved on its diagnosis. Based on the lack of a gold-standard diagnostic tool, we aimed to present a metabolomic study for the assessment of stool metabolic alterations. Stool samples were collected from 25 patients segregated into positive for strongyloidiasis (n = 10) and negative control (n = 15) and prepared for direct injection high-resolution mass spectrometry analysis. Using metabolomics workflow, 18 metabolites were annotated increased or decreased in strongyloidiasis condition, from which a group of 5 biomarkers comprising caprylic acid, mannitol, glucose, lysophosphatidylinositol and hydroxy-dodecanoic acid demonstrated accuracy over 89% to be explored as potential markers. The observed metabolic alteration in stool samples indicates involvement of microbiota remodeling, parasite constitution, and host response during S. stercoralis infection.

Hookworm infections: Reappraising the evidence for a role of Neutrophils in light of NETosis

In Hookworm infection, neutrophils have long had the image of the villain, being recruited to the site of larval migration because of damage but participating themselves in tissue injury. With recent developments in neutrophil biology, there is an increasing body of evidence for the role of neutrophils as effector cells in hookworm immunity. In particular, their ability to release extracellular traps, or neutrophil extracellular traps (NETs), confer neutrophils a larvicidal activity. Here, we review recent evidence in this nascent field and discuss the avenue for future research on NETs/hookworm interactions.

Identification of Small Molecules of the Infective Stage of Human Hookworm Using LCMS-Based Metabolomics and Lipidomics Protocols

Hookworm infections affect millions of people worldwide and are responsible for impaired mental and physical growth in children, and anemias. There is no vaccine, and increasing anthelmintic drug resistance in nematodes of domestic animals, and reduced drug cure rates in nematode infections of humans is alarming. Despite this looming health problem, there is a significant knowledge gap in terms of nonproteinaceous "excretory/secretory products" (ESPs) and how they orchestrate a parasitic existence. In the current study, we have conducted the first metabolomic and lipidomic analysis of the infective third-stage filariform larvae (L3) of the predominant human hookworm Necator americanus using liquid chromatography-mass spectrometry. Altogether, we have identified a total of 645 small molecules that were mainly produced through amino acid and glycerophospholipid metabolism. Putatively, 495 metabolites were unique to the somatic tissue extract, and 34 metabolites were present only in the ESP component. More than 21 novel mass features with nitrogen and sulfur functional groups were detected in the ESP component for the first time from helminths. While this study could not establish the biological functions of the metabolites identified, literature searches revealed that these metabolites possess various biological properties, including anti-inflammatory activities. These metabolites are likely used by the parasite upon exposure to a host to facilitate skin penetration, passage through different tissues, and immune regulation in the small bowel. Overall, the results presented herein offer significant insight into the metabolome of N. americanus L3 and have the potential to instigate future work to establish biomarkers of infection. This area urgently needs attention, given the lack of sensitive point-of-care diagnostic tools.

Mining Anti-Inflammation Molecules From Nippostrongylus brasiliensis-Derived Products Through the Metabolomics Approach

Hookworm is one type of soil-transmitted helminth, which could exert an anti-inflammatory effect in human or animal host, which provides a beneficial possibility for the discovery of inflammatory-related disease interventions. The identification of hookworm-derived anti-inflammatory molecules is urgently needed for future translational research. The emergence of metabolomics has become a powerful approach to comprehensively characterize metabolic alterations in recent times. Herein, excretory and secretory products (ESPs) were collected from cultured adult worm, while small intestinal contents were obtained from Nippostrongylus brasiliensis (N. brasiliensis, Nb)-infected mice. Through ultra-high-performance liquid chromatography coupled with mass spectrometry (UHPLC-MS) platform, metabolomics analysis was used to explore the identification of anti-inflammatory molecules. Out of 45 differential metabolites that were discovered from ESPs, 10 of them showed potential anti-inflammatory properties, which could be subclassed into amino acids, furanocoumarins, linear diarylheptanoids, gamma butyrolactones, and alpha-keto acids. In terms of intestinal contents that were derived from N. brasiliensis-infected mice, 14 out of 301 differential metabolites were discovered to demonstrate anti-inflammatory effects, with possible subclassification into amino acids, benzylisoquinolines, quaternary ammonium salts, pyrimidines, pregnane steroids, purines, biphenyls, and glycerophosphocholines. Furthermore, nine of the differential metabolites appeared both in ESPs and infected intestinal contents, wherein four were proven to show anti-inflammation properties, namely, L-glutamine, glutamine (Gln), pyruvate, and alanine-Gln (Ala-Gln). In summary, we have provided a method for the identification and analysis of parasite-derived molecules with potential anti-inflammatory properties in the present study. This array of anti-inflammatory metabolites could provide clues for future evaluation and translational study of these anti-inflammatory molecules.

The yin and yang of human soil-transmitted helminth infections

The major soil-transmitted helminths that infect humans are the roundworms, whipworms and hookworms. Soil-transmitted helminth infections rank among the most important neglected tropical diseases in terms of morbidity, and almost one billion people are still infected with at least one species. While anthelmintic drugs are available, they do not offer long term protection against reinfection, precipitating the need for vaccines that provide long-term immunologic defense. Vaccine discovery and development is in advanced clinical development for hookworm infection, with a bivalent human hookworm vaccine in clinical trials in Brazil and Africa, but is in its infancy for both roundworm (ascariasis) and whipworm (trichuriasis) infections. One of the greatest hurdles to developing soil-transmitted helminth vaccines is the potent immunoregulatory properties of these helminths, creating a barrier to the induction of meaningful long-term protective immunity. While challenging for vaccinologists, this phenomenon presents unique opportunities to develop an entirely new class of anti-inflammatory drugs that capitalise on these immunomodulatory strategies. Epidemiologic studies and clinical trials employing experimental soil-transmitted helminth challenge models, when coupled with findings from animal models, show that at least some soil-transmitted helminth-derived molecules can protect against the onset of autoimmune, allergic and metabolic disorders, and several natural products with the desired bioactivity have been isolated and tested in pre-clinical settings. The yin and yang of soil-transmitted helminth infections reflect both the urgency for effective vaccines and the potential for new immunoregulatory molecules from parasite products.

Enteric Tuft Cells in Host-Parasite Interactions

Enteric tuft cells are chemosensory epithelial cells gaining attention in the field of host-parasite interactions. Expressing a repertoire of chemosensing receptors and mediators, these cells have the potential to detect lumen-dwelling helminth and protozoan parasites and coordinate epithelial, immune, and neuronal cell defenses against them. This review highlights the versatility of enteric tuft cells and sub-types thereof, showcasing nuances of tuft cell responses to different parasites, with a focus on helminths reflecting the current state of the field. The role of enteric tuft cells in irritable bowel syndrome, inflammatory bowel disease and intestinal viral infection is assessed in the context of concomitant infection with parasites. Finally, the review presents pertinent questions germane to understanding the enteric tuft cell and its role in enteric parasitic infections. There is much to be done to fully elucidate the response of this intriguing cell type to parasitic-infection and there is negligible data on the biology of the human enteric tuft cell—a glaring gap in knowledge that must be filled.

The interplay between Trichuris and the microbiota

Parasitic worms are amongst the most common pathogens to infect humans and have a long-established history of inflicting disease in their hosts. There is a large body of evidence that states intestine-dwelling helminths ensure their survival by influencing the host immune response against them. In recent years, it has become apparent that the large and diverse microbial communities that exist in the gastrointestinal (GI) tract of the host and within the parasite itself have a pivotal role in worm survival and persistence. Using a variety of mouse models (including laboratory, germ-free and rewilded mice), there have been new insights into how bacteria and worms interact with each other; this includes the discovery that Trichuris is unable to hatch and/or infect their host in the absence of bacteria, and that these worms contain a Trichuris-specific gut microbiota. These interactions are determined in part by the capacity of the host, gut microbiota and worms to communicate via metabolites such as butyrate, which are microbially derived and have known immunoregulatory properties. By exploring the contribution of gut bacteria to worm infections and the intricate relationship that exists between them, an exciting and emerging field in whipworm parasitology is established.

Immunoregulatory molecules secreted by Trichuris muris

Trichuris, whipworm nematode infections are prevalent in humans, domestic livestock and mammals. All share an epithelial dwelling niche and similar life cycle with the chronic infections that follow implying that immune evasion mechanisms are operating. Nematode excretory secretory (ES) products have been shown to be a rich source of immunomodulatory molecules for many species. The Trichuris muris model is a natural parasite of mice and has been used extensively to study host–parasite interactions and provides a tractable platform for investigation of the immunoregulatory capacity of whipworm ES. The present review details progress in identification of the composition of T. muris ES, immunomodulatory components and their potential mechanisms of action. The adult T. muris secretome is dominated by one protein with modulatory capacity although remains to be completely characterized. In addition, the secretome contains multiple other proteins and small molecules that have immunomodulatory potential, certainly by comparison to other Trichuris species. Moreover, T. muris-derived exosomes/exosome-like vesicles contain both protein and multiple miRNAs providing an alternate delivery process for molecules with the potential to modulate host immunity.