Helminth extracellular vesicles: Interactions with the host immune system

Protein profile of extracellular vesicles derived from adult Parascaris spp

BACKGROUND

Parascaris spp. represent a significant threat to equine health worldwide, particularly in foals. The long-term survival of parasites in the host necessitates persistent modulation of the host immune response. Intercellular communication achieved through the exchange of molecules via extracellular vesicles (EVs) released from the parasite could be a crucial factor in this regard. This study aimed to isolate and characterize EVs released by adult male and female Parascaris worms and conduct a proteomic analysis to identify sex-specific proteins and potential immunomodulatory factors.

METHODS

Live adult Parascaris worms were collected, and EVs were isolated from spent culture media using differential ultracentrifugation. Nanoparticle tracking analysis and transmission electron microscopy confirmed the size, concentration, and morphology of the isolated EVs. Proteins within the isolated EVs were analyzed using mass spectrometry-based proteomics (LC-MS/MS).

RESULTS

Proteomic analysis revealed a total of 113 proteins in Parascaris EVs, with several proteins showing homology to known helminth exosome proteins and exhibiting immunomodulatory functions. Sex-specific differences in EV protein composition were observed, with a distinct abundance of C-type lectins in female EVs, suggesting potential sex-specific roles or regulation. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses revealed metabolic pathways shared between male and female Parascaris EVs, as well as differences in signal transduction, and cell growth and death pathways, indicating sex-specific variations.

CONCLUSIONS

These findings imply that Parascaris EVs and their protein cargo are complex. This data potentially opens avenues for discovering innovative approaches to managing and understanding helminth infection.

Brugia malayi filarial helminth-derived extracellular vesicles suppress antigen presenting cell function and antigen-specific CD4+ T cell responses

Introduction

Live microfilariae (mf) and mf-derived extracellular vesicles (EVs) have been shown to modulate human antigen presenting cell (APC) function, most notably by suppressing the induction of IL-12 (and other pro-inflammatory cytokines) following activation with LPS and interferon-y.

Methods

To explore further how EVs alter human APC function, we studied the effect of mf and EVs on human elutriated monocyte-derived dendritic cells (DC) following exposure to Mf, mf-derived excretory/secretory (E/S) products, E/S depleted of EVs through ultracentrifugation and purified EVs.  After demonstrating that the measurable responses induced by live mf could be recapitulated by EVs and EV-containing E/S, we next performed RNAseq analysis of human DC following exposure to live mf, EVs, E/S, or EV-depleted E/S.

Results

In our analyses of the data for the DC, using a false discovery rate (FDR)<0.05, EV-exposed DC had induced the expression of 212 differentially expressed genes (DEGs) when compared to unexposed DC and 157 when compared to E/S-depleted EVs.  These genes were enriched in GO biological processes associated with neutrophil degranulation and 15 DEGs associated with KEGG Lysosome pathways. IPA analysis point to immune dysregulation. We next aimed to understand the intracellular processes altered by EVs and the effect these have on effector T cells. When SARS CoV-2 Membrane-specific CD4+ TCLs were assessed following EV conditioning of autologous DC and activation with the SARS CoV-2-Membrane peptide pool, we found conditioning reduced the frequency of SARS CoV-2 Membrane-specific CD3+ CD4+ CD154+ cells (p=.015). Similarly, EV-conditioning of SARS CoV-2 Membrane-specific CD3+ CD4+ cells induced fewer cell capable of producing IFN-γ (p=.045).

Discussion

Taken together, our data suggest a modulatory role of EVs on APC function that likely leads to defects in T cell effector function.

Unraveling new players in helminth pathology: extracellular vesicles from Fasciola hepatica and Dicrocoelium dendriticum exert different effects on hepatic stellate cells and hepatocytes

Fasciola hepatica and Dicrocoelium dendriticum are parasitic trematodes residing in the bile ducts of mammalian hosts, causing, in some cases, impairment of liver function and hepatic fibrosis. Previous studies have shown that extracellular vesicles released by F. hepatica (FhEVs) and D. dendriticum (DdEVs) induce a distinct phenotype in human macrophages, but there is limited information on the effect of parasitic EVs on liver cells, which interact directly with the worms in natural infections. In this study, we isolated FhEVs and DdEVs by size exclusion chromatography and labeled them with a lipophilic fluorescent dye to analyze their uptake by human hepatic stellate cells (HSC) and hepatocytes, important cell types in liver pathology, using synthetic liposomes as internal labeling and uptake control. We analyzed EV uptake and the proteome profiles after the treatment with EVs for both cell types. Our results reveal that EVs establish unique and specific interactions with stellate cells and hepatocytes, suggesting a different role of EVs derived from each parasite, depending on the migration route to reach their final niche. FhEVs have a cytostatic effect on HSCs, but induce the extracellular matrix secretion and elicit anti-inflammatory responses in hepatocytes. DdEVs have a more potent anti-proliferative effect than FhEVs and trigger a global inflammatory response, increasing the levels of NF-κB and other inflammatory mediators in both cell types. These interactions may have a major influence on the progression of the disease, serving to generate conditions that may favor the establishment of the helminths in the host.

An in-depth exploration of the multifaceted roles of EVs in the context of pathogenic single-cell microorganisms

SUMMARYExtracellular vesicles (EVs) have been recognized throughout scientific communities as potential vehicles of intercellular communication in both eukaryotes and prokaryotes, thereby influencing various physiological and pathological functions of both parent and recipient cells. This review provides an in-depth exploration of the multifaceted roles of EVs in the context of bacteria and protozoan parasite EVs, shedding light on their contributions to physiological processes and disease pathogenesis. These studies highlight EVs as a conserved mechanism of cellular communication, which may lead us to important breakthroughs in our understanding of infection, mechanisms of pathogenesis, and as indicators of disease. Furthermore, EVs are involved in host-microbe interactions, offering insights into the strategies employed by bacteria and protozoan parasites to modulate host responses, evade the immune system, and establish infections.

Overview of extracellular vesicles in pathogens with special focus on human extracellular protozoan parasites

Extracellular vesicles (EVs) are lipid-bilayered membrane-delimited particles secreted by almost any cell type, involved in different functions according to the cell of origin and its state. From these, cell to cell communication, pathogen-host interactions and modulation of the immune response have been widely studied. Moreover, these vesicles could be employed for diagnostic and therapeutic purposes, including infections produced by pathogens of diverse types; regarding parasites, the secretion, characterisation, and roles of EVs have been studied in particular cases. Moreover, the heterogeneity of EVs presents challenges at every stage of studies, which motivates research in this area. In this review, we summarise some aspects related to the secretion and roles of EVs from several groups of pathogens, with special focus on the most recent research regarding EVs secreted by extracellular protozoan parasites.

Characterization of antigenic proteins of the Taenia solium postoncospheral form

Neurocysticercosis is the leading cause for acquired epilepsy worldwide, and it is caused by the larval stage of the parasite Taenia solium. Several proteins of this stage have been characterized and studied to understand the parasite-host interaction, however, the proteins from the early cysticercus stages (the postoncospheral form) have not yet been characterized. The study of the postoncospheral form proteins is important to understand the host-parasite relationship in the early stages of infection. The aim of this work was to identify postoncospheral form antigenic proteins using sera from neurocysticercosis patients. T. solium activated oncospheres were cultured in HCT-8 cells to obtain the postoncospheral form. Soluble total and excretory/secretory proteins were obtained from the postoncospheral form and were incubated with both pool sera and individual serum of neurocysticercosis positive human patients. Immunoblotting showed target antigenic proteins with apparent molecular weights of 23 kDa and 46-48 kDa. The 46-48 kDa antigen bands present in soluble total and excretory/secretory postoncospheral form proteins were analyzed by LC-MS/MS; proteins identified were: nuclear elongation factor 1 alpha, enolase, unnamed protein product/antigen diagnostic GP50, calcium binding protein calreticulin precursor and annexin. The postoncospheral form expresses proteins related to interaction with the host, some of these proteins are predicted to be exosomal proteins. In conclusion, postoncospheral proteins are consistent targets of the humoral immune response in human and may serve as targets for diagnosis and vaccines.

Schistosoma excretory/secretory products: an untapped library of tolerogenic immunotherapeutics against food allergy

Food allergy (FA) is considered the 'second wave' of the allergy epidemic in developed countries after asthma and allergic rhinitis with a steadily growing burden of 40%. The absence of early childhood pathogen stimulation embodied by the hygiene hypothesis is one explanation, and in particular, the eradication of parasitic helminths could be at play. Infections with parasites Schistosoma spp. have been found to have a negative correlation with allergic diseases. Schistosomes induce regulatory responses to evade immune detection and ensure their long-term survival. This is achieved via excretory/secretory (E/S) products, consisting of proteins, lipids, metabolites, nucleic acids and extracellular vesicles, representing an untapped therapeutic avenue for the treatment of FA without the unpleasant side-effects and risks associated with live infection. Schistosome-derived immunotherapeutic development is in its infancy and novel discoveries are heavily technology dependent; thus, it is essential to better understand how newly identified molecules interact with host immune systems to ensure safety and successful translation. This review will outline the identified Schistosoma-derived E/S products at all life cycle stages and discuss known mechanisms of action and their ability to suppress FA.

Extracellular vesicles

Extracellular vesicles (EVs) encompass a diverse array of membrane-bound organelles released outside cells in response to developmental and physiological cell needs. EVs play important roles in remodeling the shape and content of differentiating cells and can rescue damaged cells from toxic or dysfunctional content. EVs can send signals and transfer metabolites between tissues and organisms to regulate development, respond to stress or tissue damage, or alter mating behaviors. While many EV functions have been uncovered by characterizing ex vivo EVs isolated from body fluids and cultured cells, research using the nematode Caenorhabditis elegans has provided insights into the in vivo functions, biogenesis, and uptake pathways. The C. elegans EV field has also developed methods to analyze endogenous EVs within the organismal context of development and adult physiology in free-living, behaving animals. In this review, we summarize major themes that have emerged for C. elegans EVs and their relevance to human health and disease. We also highlight the diversity of biogenesis mechanisms, locations, and functions of worm EVs and discuss open questions and unexplored topics tenable in C. elegans, given the nematode model is ideal for light and electron microscopy, genetic screens, genome engineering, and high-throughput omics.

Micro RNA profiles of host extracellular vesicles are modulated by Ascaris suum infection but parasite extracellular vesicle miRNAs are systemically undetectable using in-depth miRNA sequencing

The intestinal helminth Ascaris lumbricoides infects over 800 million people. Infections are often chronic and immunity is not sterilizing due to host-immune modulation, therefore reinfection is common after antihelmintic treatment. We have previously demonstrated a role for Ascaris spp. extracellular vesicles (EVs) in host immune modulation but whether EVs are recognized by the adaptive immune system and are present systemically in the host remains unknown. Therefore, we employed a well-established trickle infection model in pigs to mimic natural Ascaris infection in humans. EVs were isolated from adult Ascaris suum followed by immunoblotting of EV and EV-depleted secretory fractions using plasma from infected and uninfected pigs. Next, EVs were isolated from pig plasma at day 56 post first infection and subjected to deep small RNAseq analysis. RNAs were aligned to A. suum and Sus scrofa miRNA complements to detect A. suum EVs and elucidate the host EV micro RNA (miRNA) response to infection, respectively. Infection generates robust antibody responses against A. suum EVs that is distinct from EV-depleted fractions. However, A. suum miRNAs were not detectable in EVs from the peripheral blood. Notably, host plasma-derived EV miRNA profiles showed significant changes between infected and uninfected pigs, indicating that Ascaris infection drives systemic changes in host EV composition.

Exploring extracellular vesicles in zoonotic helminth biology: implications for diagnosis, therapeutic and delivery

Extracellular vesicles (EVs) have emerged as key intercellular communication and pathogenesis mediators. Parasitic organisms' helminths, cause widespread infections with significant health impacts worldwide. Recent research has shed light on the role of EVs in the lifecycle, immune evasion, and disease progression of these parasitic organisms. These tiny membrane-bound organelles including microvesicles and exosomes, facilitate the transfer of proteins, lipids, mRNAs, and microRNAs between cells. EVs have been isolated from various bodily fluids, offering a potential diagnostic and therapeutic avenue for combating infectious agents. According to recent research, EVs from helminths hold great promise in the diagnosis of parasitic infections due to their specificity, early detection capabilities, accessibility, and the potential for staging and monitoring infections, promote intercellular communication, and are a viable therapeutic tool for the treatment of infectious agents. Exploring host-parasite interactions has identified promising new targets for diagnostic, therapy, and vaccine development against helminths. This literature review delves into EVS's origin, nature, biogenesis, and composition in these parasitic organisms. It also highlights the proteins and miRNAs involved in EV release, providing a comprehensive summary of the latest findings on the significance of EVs in the biology of helminths, promising targets for therapeutic and diagnostic biomarkers.

RNA-seq analysis of parasitism by Intoshia linei (Orthonectida) reveals protein effectors of defence, communication, feeding and growth

Orthonectida is a group of multicellular endoparasites of a wide range of marine invertebrates. Their parasitic stage is a multinuclear shapeless plasmodium infiltrating host tissues. The development of the following worm-like sexual generation takes place within the cytoplasm of the plasmodium. The existence of the plasmodial stage and the development of a sexual stage within the plasmodium are unique features to Bilateria. However, the molecular mechanisms that maintain this peculiar organism, and hence enable parasitism in orthonectids, are unknown. Here, we present the first-ever RNA-seq analysis of the plasmodium, aimed at the identification and characterization of the plasmodium-specific protein-coding genes and corresponding hypothetical proteins that distinguish the parasitic plasmodium stage from the sexual stage of the orthonectid Intoshia linei Giard, 1877, parasite of nemertean Lineus ruber Müller, 1774. We discovered 119 plasmodium-specific proteins, 82 of which have inferred functions based on known domains. Thirty-five of the detected proteins are orphans, at least part of which may reflect the unique evolutionary adaptations of orthonectids to parasitism. Some of the identified proteins are known effector molecules of other endoparasites suggesting convergence. Our data indicate that the plasmodium-specific proteins might be involved in the plasmodium defense against the host, host-parasite communication, feeding and nutrient uptake, growth within the host, and support of the sexual stage development. These molecular processes in orthonectids have not been described before, and the particular protein effectors remained unknown until now.

Taenia solium cysticerci's extracellular vesicles Attenuate the AKT/mTORC1 pathway for Alleviating DSS-induced colitis in a murine model

The excretory-secretory proteome plays a pivotal role in both intercellular communication during disease progression and immune escape mechanisms of various pathogens including cestode parasites like Taenia solium. The cysticerci of T. solium causes infection in the central nervous system known as neurocysticercosis (NCC), which affects a significant population in developing countries. Extracellular vesicles (EVs) are 30-150-nm-sized particles and constitute a significant part of the secretome. However, the role of EV in NCC pathogenesis remains undetermined. Here, for the first time, we report that EV from T. solium larvae is abundant in metabolites that can negatively regulate PI3K/AKT pathway, efficiently internalized by macrophages to induce AKT and mTOR degradation through auto-lysosomal route with a prominent increase in the ubiquitination of both proteins. This results in less ROS production and diminished bacterial killing capability among EV-treated macrophages. Due to this, both macro-autophagy and caspase-linked apoptosis are upregulated, with a reduction of the autophagy substrate sequestome 1. In summary, we report that T. solium EV from viable cysts attenuates the AKT-mTOR pathway thereby promoting apoptosis in macrophages, and this may exert immunosuppression during an early viable stage of the parasite in NCC, which is primarily asymptomatic. Further investigation on EV-mediated immune suppression revealed that the EV can protect the mice from DSS-induced colitis and improve colon architecture. These findings shed light on the previously unknown role of T. solium EV and the therapeutic role of their immune suppression potential.

The knowns and unknowns of helminth-host miRNA cross-kingdom communication

MicroRNAs (miRNAs) are small noncoding RNAs that oversee gene modulation. They are integral to cellular functions and can migrate between species, leading to cross-kingdom gene suppression. Recent breakthroughs in helminth genome studies have sparked curiosity about helminth RNA regulators and their ability to regulate genes across species. Growing data indicate that helminth miRNAs have a significant impact on the host's immune system. Specific miRNAs from helminth parasites can merge with the host's miRNA system, implying that parasites could exploit their host's regulatory machinery and function. This review highlights the role of cross-kingdom helminth-derived miRNAs in the interplay between host and parasite, exploring potential routes for their uptake, processing, and consequences in host interaction.

Advancing Strongyloides omics data: bridging the gap with Caenorhabditis elegans

Among nematodes, the free-living model organism Caenorhabditis elegans boasts the most advanced portfolio of high-quality omics data. The resources available for parasitic nematodes, including Strongyloides spp., however, are lagging behind. While C. elegans remains the most tractable nematode and has significantly advanced our understanding of many facets of nematode biology, C. elegans is not suitable as a surrogate system for the study of parasitism and it is important that we improve the omics resources available for parasitic nematode species. Here, we review the omics data available for Strongyloides spp. and compare the available resources to those for C. elegans and other parasitic nematodes. The advancements in C. elegans omics offer a blueprint for improving omics-led research in Strongyloides. We suggest areas of priority for future research that will pave the way for expansions in omics resources and technologies. This article is part of the Theo Murphy meeting issue 'Strongyloides: omics to worm-free populations'.

Progresses and challenges in Strongyloides spp. proteomics

The availability of high-quality data of helminth genomes provided over the past two decades has supported and accelerated large-scale 'omics studies and, consequently, the achievement of a more in-depth molecular characterization of a number of pathogens. This has also involved Strongyloides spp. and since their genome was made available transcriptomics has been rather frequently applied to investigate gene expression regulation across their life cycle. Strongyloides proteomics characterization has instead been somehow neglected, with only a few reports performing high-throughput or targeted analyses associated with protein identification by tandem mass spectrometry. Such investigations are however necessary in order to discern important aspects associated with human strongyloidiasis, including understanding parasite biology and the mechanisms of host-parasite interaction, but also to identify novel diagnostic and therapeutic targets. In this review article, we will give an overview of the published proteomics studies investigating strongyloidiasis at different levels, spanning from the characterization of the somatic proteome and excretory/secretory products of different parasite stages to the investigation of potentially immunogenic proteins. Moreover, in the effort to try to start filling the current gap in host-proteomics, we will also present the first serum proteomics analysis in patients suffering from human strongyloidiasis. This article is part of the Theo Murphy meeting issue 'Strongyloides: omics to worm-free populations'.

Proteomic differences between extracellular vesicles and extracellular vesicle-depleted excretory/secretory products of barber's pole worm

BACKGROUND

Components of excretory/secretory products (ESPs) of helminths have been proposed as vaccine targets and shown to play a role in modulating host immune responses for decades. Such research interest is further increased by the discovery of extracellular vesicles (EVs) in the ESPs of parasitic worms. Although efforts have been made to reveal the cargos of EVs, little is known about the proteomic differences between EVs and canonical ESPs released by parasitic worms from animals.

METHODS

The total ESPs of Haemonchus contortus (barber's pole worm) were obtained by short-term in vitro culturing of young adult worms, and small EVs were isolated from ESPs using an ultracentrifugation method. Data-dependent acquisition (DDA) label-free Nano-LC-MS/MS was used to quantify the proteomic difference between small EVs and EV-depleted ESPs of H. contortus. Functional annotation and enrichment of the differential proteins were performed regarding cellular components, molecular functions, pathways, and/or biological processes.

RESULTS

A total of 1697 proteins were identified in small EVs and EV-depleted ESPs of H. contortus adult worms, with 706 unique proteins detected in the former and 597 unique proteins in the latter. It was revealed that proteins in small EVs are dominantly cytoplasmic, whereas proteins in EV-depleted ESPs are mainly extracellular; canonical ESPs such as proteases and small GTPases were abundantly detected in small EVs, and SCP/TAP-, DUF-, and GLOBIN domain-containing proteins were mainly found in EV-depleted ESPs. Compared with well-characterised proteins in small EVs, about 50% of the proteins detected in EV-depleted ESPs were poorly characterised.

CONCLUSIONS

There are remarkable differences between small EVs and EV-depleted ESPs of H. contortus in terms of protein composition. Immune modulatory effects caused by nematode ESPs are possibly contributed mainly by the proteins in small EVs.

Fish and Food-Fatale: Food-borne Trematode Opisthorchis viverrini and Cholangiocarcinoma

Neglected Tropical Diseases (NTDs) are a group of communicable diseases with a long history with human beings. NTDs are the proxy of poverty since they affect those in low-income and extreme-poverty populations, as those populations lack access to proper health care, clean water, sanitary conditions, and hygiene. NTDs create losses for a nation that come from the health and the economic sectors as well since the costs of diagnosis, prevention, and treatment strain the national purse strings. One of the 20 different forms of NTDs on the list is food-borne trematodes, comprises of Fasciola, Paragonimus, Clonorchis, and Opisthorchis. Currently, it is estimated that food-borne trematodes can cause a devastating effect on mortality and morbidity. All of them are zoonotic, as humans become infected by ingestion of a second intermediate host, such as freshwater snails, fish, or water vegetables. Opisthorchis viverrini, one of the food-borne trematodes that can be found mostly in South East Asia regions, especially in the Mekong basin, is regarded as a group 1 carcinogen leading to cholangiocarcinoma (CCA). This study aims to present the updated review of Opisthorchis viverrini and CCA.

Extracellular Vesicles Secreted by Acanthamoeba culbertsoni Have COX and Proteolytic Activity and Induce Hemolysis

Several species of Acanthamoeba genus are potential pathogens and etiological agents of several diseases. The pathogenic mechanisms carried out by these amoebae in different target tissues have been documented, evidencing the relevant role of contact-dependent mechanisms. With the purpose of describing the pathogenic processes carried out by these protozoans more precisely, we considered it important to determine the emission of extracellular vesicles (EVs) as part of the contact-independent pathogenicity mechanisms of A. culbertsoni, a highly pathogenic strain. Through transmission electronic microscopy (TEM) and nanoparticle tracking analysis (NTA), EVs were characterized. EVs showed lipid membrane and a size between 60 and 855 nm. The secretion of large vesicles was corroborated by confocal and TEM microscopy. The SDS-PAGE of EVs showed proteins of 45 to 200 kDa. Antigenic recognition was determined by Western Blot, and the internalization of EVs by trophozoites was observed through Dil-labeled EVs. In addition, some EVs biological characteristics were determined, such as proteolytic, hemolytic and COX activity. Furthermore, we highlighted the presence of leishmanolysin in trophozites and EVs. These results suggest that EVs are part of a contact-independent mechanism, which, together with contact-dependent ones, allow for a better understanding of the pathogenicity carried out by Acanthamoeba culbertsoni.

Impact of Ivermectin on the Gut Microbial Ecosystem

Ivermectin is a an anti-helminthic that is critical globally for both human and veterinary care. To the best of our knowledge, information available regarding the influence of ivermectin (IVM) on the gut microbiota has only been collected from diseased donors, who were treated with IVM alone or in combination with other medicines. Results thus obtained were influenced by multiple elements beyond IVM, such as disease, and other medical treatments. The research presented here investigated the impact of IVM on the gut microbial structure established in a Triple-SHIME® (simulator of the human intestinal microbial ecosystem), using fecal material from three healthy adults. The microbial communities were grown using three different culture media: standard SHIME media and SHIME media with either soluble or insoluble fiber added (control, SF, ISF). IVM introduced minor and temporary changes to the gut microbial community in terms of composition and metabolite production, as revealed by 16S rRNA amplicon sequencing analysis, flow cytometry, and GC-MS. Thus, it was concluded that IVM is not expected to induce dysbiosis or yield adverse effects if administered to healthy adults. In addition, the donor's starting community influences the relationship between IVM and the gut microbiome, and the soluble fiber component in feed could protect the gut microbiota from IVM; an increase in short-chain fatty acid production was predicted by PICRUSt2 and detected with IVM treatment.

Fasciola hepatica antioxidant and protease-inhibitor cocktail recombinant vaccines administered five times elicit potent and sustained immune responses in sheep but do not confer protection

Our laboratory's vaccine development strategy against the livestock parasite Fasciola hepatica centres around disrupting key biological processes by combining groups of antigens with similar/complementary functional actions into a single vaccine cocktail. In this study the focus was on antioxidant protein vaccines and a protease inhibitor vaccine aimed at disrupting the parasite's ability to defend against oxidative stress and protease-inhibitor balance, respectively. Two combinations of recombinantly expressed antioxidants were assessed, namely peroxiredoxin (rFhPrx), thioredoxin (rFhTrx) and thioredoxin-glutathione reductase (rFhTGR) (Group 1) and rFhPrx, rFhTrx, and two superoxide dismutases (rFhSOD1 and rFhSOD3) (Group 2). The protease inhibitor vaccine cocktail included representatives of each of the key secreted protease inhibitor families, namely a Kunitz-type inhibitor (rFhKT1), a serpin (rFhSrp1) and a stefin, (rFhStf1) (Group 3). The vaccine combinations were formulated in adjuvant Montanide 61VG administered at five timepoints; two before experimental challenge with 60 F. hepatica metacercariae and three after infection. The vaccine combinations did not reduce the liver fluke burden, and only Group 2 displayed a marginal reduction in egg viability (8.2%). Despite previous results showing an effect of liver fluke vaccines on overall weight gain in infected animals, no significant (P value >0.05) impact on weight gain was observed in this study. Antibodies were elicited against all the vaccine antigens within the cocktails and were maintained at high levels to the end of the trial, due to our strategy of continuing vaccine administration after infection. However, these responses were not boosted by the challenge F. hepatica infection. A comparative analysis with previous vaccine data using a protease inhibitor vaccine found no repeat of the promising outcomes associated with this vaccine, indicating that the addition of rFhSrp1 to the vaccine cocktail did not improve vaccine efficacy. Assessment of liver pathology across the two trials using a modified liver enzyme score (glutamate dehydrogenase to platelet ratio) at eight weeks post infection suggests an association with liver fluke burden above 45 flukes, which could be used to predict liver pathology in future trials. The results reported in this study highlight the ambiguousness in liver fluke vaccine development and the difficulty in obtaining consistent and repeatable protection. This work stresses the need for repetition of trials and the use of sufficiently sized groups to assess vaccine efficacy with adequate statistical power.

Long live the host! Proteomic analysis reveals possible strategies for parasitic manipulation of its social host

Parasites with complex life cycles often manipulate the phenotype of their intermediate hosts to increase the probability of transmission to their definitive hosts. Infection with Anomotaenia brevis, a cestode that uses Temnothorax nylanderi ants as intermediate hosts, leads to a multiple-fold extension of host lifespan and to changes in behaviour, morphology and colouration. The mechanisms behind these changes are unknown, as is whether the increased longevity is achieved through parasite manipulation. Here, we demonstrate that the parasite releases proteins into its host with functions that might explain the observed changes. These parasitic proteins make up a substantial portion of the proteome of the hosts' haemolymph, and thioredoxin peroxidase and superoxide dismutase, two antioxidants, exhibited the highest abundances among them. The largest part of the secreted proteins could not be annotated, indicating they are either novel or severely altered during recent coevolution to function in host manipulation. We also detected shifts in the hosts' proteome with infection, in particular an overabundance of vitellogenin-like A in infected ants, a protein that regulates division of labour in Temnothorax ants, which could explain the observed behavioural changes. Our results thus suggest two different strategies that might be employed by this parasite to manipulate its host: secreting proteins with immediate influence on the host's phenotype and altering the host's translational activity. Our findings highlight the intricate molecular interplay required to influence the phenotype of a host and point to potential signalling pathways and genes involved in parasite-host communication.

Teleost innate immunity, an intricate game between immune cells and parasites of fish organs: who wins, who loses

Fish, comprising over 27,000 species, represent the oldest vertebrate group and possess both innate and adaptive immune systems. The susceptibility of most wild fish to parasitic infections and related diseases is well-established. Among all vertebrates, the digestive tract creates a remarkably favorable and nutrient-rich environment, which, in turn, renders it susceptible to microparasites and macroparasites. Consequently, metazoan parasites emerge as important disease agents, impacting both wild and farmed fish and resulting in substantial economic losses. Given their status as pathogenic organisms, these parasites warrant considerable attention. Helminths, a general term encompassing worms, constitute one of the most important groups of metazoan parasites in fish. This group includes various species of platyhelminthes (digeneans, cestodes), nematodes, and acanthocephalans. In addition, myxozoans, microscopic metazoan endoparasites, are found in water-dwelling invertebrates and vertebrate hosts. It is worth noting that several innate immune cells within the fish alimentary canal and certain visceral organs (e.g., liver, spleen, and gonads) play active roles in the immune response against parasites. These immune cells include macrophages, neutrophils, rodlet cells, and mast cells also known as eosinophilic granular cells. At the site of intestinal infection, helminths often impact mucous cells number and alter mucus composition. This paper presents an overview of the state of the art on the occurrence and characteristics of innate immune cells in the digestive tract and other visceral organs in different fish-parasite systems. The data, coming especially from studies employed immunohistochemical, histopathological, and ultrastructural analyses, provide evidence supporting the involvement of teleost innate immune cells in modulating inflammatory responses to metazoan and protozoan parasitic infections.

Guidelines for the purification and characterization of extracellular vesicles of parasites

Parasites are responsible for the most neglected tropical diseases, affecting over a billion people worldwide (WHO, 2015) and accounting for billions of cases a year and responsible for several millions of deaths. Research on extracellular vesicles (EVs) has increased in recent years and demonstrated that EVs shed by pathogenic parasites interact with host cells playing an important role in the parasite's survival, such as facilitation of infection, immunomodulation, parasite adaptation to the host environment and the transfer of drug resistance factors. Thus, EVs released by parasites mediate parasite-parasite and parasite-host intercellular communication. In addition, they are being explored as biomarkers of asymptomatic infections and disease prognosis after drug treatment. However, most current protocols used for the isolation, size determination, quantification and characterization of molecular cargo of EVs lack greater rigor, standardization, and adequate quality controls to certify the enrichment or purity of the ensuing bioproducts. We are now initiating major guidelines based on the evolution of collective knowledge in recent years. The main points covered in this position paper are methods for the isolation and molecular characterization of EVs obtained from parasite-infected cell cultures, experimental animals, and patients. The guideline also includes a discussion of suggested protocols and functional assays in host cells.

Characterization of the extracellular vesicles, ultrastructural morphology, and intercellular interactions of multiple clinical isolates of the brain-eating amoeba, Naegleria fowleri

Introduction

As global temperatures rise to unprecedented historic levels, so too do the latitudes of habitable niches for the pathogenic free-living amoeba, Naegleria fowleri. This opportunistic parasite causes a rare, but >97% fatal, neurological infection called primary amoebic meningoencephalitis. Despite its lethality, this parasite remains one of the most neglected and understudied parasitic protozoans.

Methods

To better understand amoeboid intercellular communication, we elucidate the structure, proteome, and potential secretion mechanisms of amoeba-derived extracellular vesicles (EVs), which are membrane-bound communication apparatuses that relay messages and can be used as biomarkers for diagnostics in various diseases.

Results and Discussion

Herein we propose that N. fowleri secretes EVs in clusters from the plasma membrane, from multivesicular bodies, and via beading of thin filaments extruding from the membrane. Uptake assays demonstrate that EVs are taken up by other amoebae and mammalian cells, and we observed a real-time increase in metabolic activity for mammalian cells exposed to EVs from amoebae. Proteomic analysis revealed >2,000 proteins within the N. fowleri-secreted EVs, providing targets for the development of diagnostics or therapeutics. Our work expands the knowledge of intercellular interactions among these amoebae and subsequently deepens the understanding of the mechanistic basis of PAM.

Tegument Ultrastructure and Morphology of the Capsule Surrounding the Tetrathyridia of the Genus Mesocestoides Vaillant, 1863 in the Liver of the Root Vole

The ultrastructure of the tegument of encapsulated tetrathyridia of the genus Mesocestoides Vaillant, 1863 (Cestoda, Cyclophyllidea, Mesocestoididae) from the liver of root voles Microtus oeconomus (Pallas, 1776) and the structure of the three-layered capsule surrounding them were studied for the first time. Several types of extracellular structures were noted on the surface of the tetrathyridia tegument: vesicles, fine granular material, and vacuoles. In addition, the phenomenon of shedding microtriches, which have expanded parts, was found. Host cells in contact with extracellular material show signs of destruction. A characteristic feature of the capsules surrounding the tetrathyridia is the reticular structure of the fibrous layer containing both native and degenerating inflammatory cells.

Characterization of protein cargo of Echinococcus granulosus extracellular vesicles in drug response and its influence on immune response

BACKGROUND

The Echinococcus granulosus sensu lato species complex causes cystic echinococcosis, a zoonotic disease of medical importance. Parasite-derived small extracellular vesicles (sEVs) are involved in the interaction with hosts intervening in signal transduction related to parasite proliferation and disease pathogenesis. Although the characteristics of sEVs from E. granulosus protoscoleces and their interaction with host dendritic cells (DCs) have been described, the effect of sEVs recovered during parasite pharmacological treatment on the immune response remains unexplored.

METHODS

Here, we isolated and characterized sEVs from control and drug-treated protoscoleces by ultracentrifugation, transmission electron microscopy, dynamic light scattering, and proteomic analysis. In addition, we evaluated the cytokine response profile induced in murine bone marrow-derived dendritic cells (BMDCs) by qPCR.

RESULTS

The isolated sEVs, with conventional size between 50 and 200 nm, regardless of drug treatment, showed more than 500 cargo proteins and, importantly, 20 known antigens and 70 potential antigenic proteins, and several integral-transmembrane and soluble proteins mainly associated with signal transduction, immunomodulation, scaffolding factors, extracellular matrix-anchoring, and lipid transport. The identity and abundance of proteins in the sEV-cargo from metformin- and albendazole sulfoxide (ABZSO)-treated parasites were determined by proteomic analysis, detecting 107 and eight exclusive proteins, respectively, which include proteins related to the mechanisms of drug action. We also determined that the interaction of murine BMDCs with sEVs derived from control parasites and those treated with ABZSO and metformin increased the expression of pro-inflammatory cytokines such as IL-12 compared to control cells. Additionally, protoscolex-derived vesicles from metformin treatments induced the production of IL-6, TNF-α, and IL-10. However, the expression of IL-23 and TGF-β was downregulated.

CONCLUSIONS

We demonstrated that sEV-cargo derived from drug-treated E. granulosus protoscoleces have immunomodulatory functions, as they enhance DC activation towards a type 1 pro-inflammatory profile against the parasite, and therefore support the proposal of a new approach for the prevention and treatment of secondary echinococcosis.

New paradigms in research on Dirofilaria immitis

BACKGROUND

Since the advent of ivermectin (along with melarsomine and doxycycline), heartworm has come to be viewed as a solved problem in veterinary medicine, diminishing investment into non-clinical research on Dirofilaria immitis. However, heartworm infections continue to pose problems for practitioners and their patients and seem to be increasing in frequency and geographic distribution. Resistance to preventative therapies (macrocyclic lactones) complicates the picture. The use of chemotherapy for other kinds of pathogens has benefitted enormously from research into the basic biology of the pathogen and on the host-pathogen interface. A lack of basic information on heartworms as parasites and how they interact with permissive and non-permissive hosts greatly limits the ability to discover new ways to prevent and treat heartworm disease. Recent advances in technical platforms will help overcome the intrinsic barriers that hamper research on D. immitis, most notably, the need for experimentally infected dogs to maintain the life cycle and provide material for experiments. Impressive achievements in the development of laboratory animal models for D. immitis will enhance efforts to discover new drugs for prevention or treatment, to characterize new diagnostic biomarkers and to identify key parasite-derived molecules that are essential for survival in permissive hosts, providing a rational basis for vaccine discovery. A 'genomics toolbox' for D. immitis could enable unprecedented insight into the negotiations between host and parasite that enable survival in a permissive host. The more we know about the pathogen and how it manipulates its host, the better able we will be to protect companion animals far into the future.

The Proteome and Lipidome of Extracellular Vesicles from Haemonchus contortus to Underpin Explorations of Host-Parasite Cross-Talk

Many parasitic worms have a major adverse impact on human and animal populations worldwide due to the chronicity of their infections. There is a growing body of evidence indicating that extracellular vesicles (EVs) are intimately involved in modulating (suppressing) inflammatory/immune host responses and parasitism. As one of the most pathogenic nematodes of livestock animals, Haemonchus contortus is an ideal model system for EV exploration. Here, employing a multi-step enrichment process (in vitro culture, followed by ultracentrifugation, size exclusion and filtration), we enriched EVs from H. contortus and undertook the first comprehensive (qualitative and quantitative) multi-omic investigation of EV proteins and lipids using advanced liquid chromatography-mass spectrometry and informatics methods. We identified and quantified 561 proteins and 446 lipids in EVs and compared these molecules with those of adult worms. We identified unique molecules in EVs, such as proteins linked to lipid transportation and lipid species (i.e., sphingolipids) associated with signalling, indicating the involvement of these molecules in parasite-host cross-talk. This work provides a solid starting point to explore the functional roles of EV-specific proteins and lipids in modulating parasite-host cross-talk, and the prospect of finding ways of disrupting or interrupting this relationship to suppress or eliminate parasite infection.

The Potential Nexus between Helminths and SARS-CoV-2 Infection: A Literature Review

Chronic helminth infections (CHIs) can induce immunological tolerance through the upregulation of regulatory T cells. In coronavirus disease 2019 (COVID-19), abnormal adaptive immune response and exaggerated immune response may cause immune-mediated tissue damage. Severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) and CHIs establish complicated immune interactions due to SARS-CoV-2-induced immunological stimulation and CHIs-induced immunological tolerance. However, COVID-19 severity in patients with CHIs is mild, as immune-suppressive anti-inflammatory cytokines counterbalance the risk of cytokine storm. Since CHIs have immunomodulatory effects, therefore, this narrative review aimed to clarify how CHIs modulate the immunoinflammatory response in SARS-CoV-2 infection. CHIs, through helminth-derived molecules, may suppress SARS-CoV-2 entry and associated hyperinflammation through attenuation of the inflammatory signaling pathway. In addition, CHIs may reduce the COVID-19 severity by reducing the SARS-CoV-2 entry points in the initial phase and immunomodulation in the late phase of the disease by suppressing the release of pro-inflammatory cytokines. In conclusion, CHIs may reduce the severity of SARS-CoV-2 infection by reducing hyperinflammation and exaggerated immune response. Thus, retrospective and prospective studies are recommended in this regard.

Helminth-derived biomacromolecules as therapeutic agents for treating inflammatory and infectious diseases: What lessons do we get from recent findings?

Despite the tremendous progress in healthcare sectors, a number of life-threatening infectious, inflammatory, and autoimmune diseases are continuously challenging mankind throughout the globe. In this context, recent successes in utilizing helminth parasite-derived bioactive macromolecules viz. glycoproteins, enzymes, polysaccharides, lipids/lipoproteins, nucleic acids/nucleotides, and small organic molecules for treating various disorders primarily resulted from inflammation. Among the several parasites that infect humans, helminths (cestodes, nematodes, and trematodes) are known as efficient immune manipulators owing to their explicit ability to modulate and modify the innate and adaptive immune responses of humans. These molecules selectively bind to immune receptors on innate and adaptive immune cells and trigger multiple signaling pathways to elicit anti-inflammatory cytokines, expansion of alternatively activated macrophages, T-helper 2, and immunoregulatory T regulatory cell types to induce an anti-inflammatory milieu. Reduction of pro-inflammatory responses and repair of tissue damage by these anti-inflammatory mediators have been exploited for treating a number of autoimmune, allergic, and metabolic diseases. Herein, the potential and promises of different helminths/helminth-derived products as therapeutic agents in ameliorating immunopathology of different human diseases and their mechanistic insights of function at cell and molecular level alongside the molecular signaling cross-talks have been reviewed by incorporating up-to-date findings achieved in the field.

Proteomic characterization of extracellular vesicles released by third stage larvae of the zoonotic parasite Anisakis pegreffii (Nematoda: Anisakidae)

Introduction

Anisakis pegreffii is a sibling species within the A. simplex (s.l.) complex requiring marine homeothermic (mainly cetaceans) and heterothermic (crustaceans, fish, and cephalopods) organisms to complete its life cycle. It is also a zoonotic species, able to accidentally infect humans (anisakiasis). To investigate the molecular signals involved in this host-parasite interaction and pathogenesis, the proteomic composition of the extracellular vesicles (EVs) released by the third-stage larvae (L3) of A. pegreffii, was characterized.

Methods

Genetically identified L3 of A. pegreffii were maintained for 24 h at 37°C and EVs were isolated by serial centrifugation and ultracentrifugation of culture media. Proteomic analysis was performed by Shotgun Analysis.

Results and discussion

EVs showed spherical shaped structure (size 65-295 nm). Proteomic results were blasted against the A. pegreffii specific transcriptomic database, and 153 unique proteins were identified. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis predicted several proteins belonging to distinct metabolic pathways. The similarity search employing selected parasitic nematodes database revealed that proteins associated with A. pegreffii EVs might be involved in parasite survival and adaptation, as well as in pathogenic processes. Further, a possible link between the A. pegreffii EVs proteins versus those of human and cetaceans’ hosts, were predicted by using HPIDB database. The results, herein described, expand knowledge concerning the proteins possibly implied in the host-parasite interactions between this parasite and its natural and accidental hosts.

The many faces of parasite calreticulin

Calreticulin from parasites and its vertebrate hosts share ~50% identity and many of its functions are equally conserved. However, the existing amino acid differences can affect its biological performance. Calreticulin plays an important role in Ca2+ homeostasis and as a chaperone involved in the correct folding of proteins within the endoplasmic reticulum. Outside the endoplasmic reticulum, calreticulin is involved in several immunological functions such as complement inhibition, enhancement of efferocytosis, and immune upregulation or inhibition. Several parasite calreticulins have been shown to limit immune responses and promote infectivity, while others are strong immunogens and have been used for the development of potential vaccines that limit parasite growth. Furthermore, calreticulin is essential in the dialogue between parasites and hosts, inducing Th1, Th2 or regulatory responses in a species-specific manner. In addition, calreticulin participates as initiator of endoplasmic reticulum stress in tumor cells and promotion of immunogenic cell death and removal by macrophages. Direct anti-tumoral activity has also been reported. The highly immunogenic and pleiotropic nature of parasite calreticulins, either as positive or negative regulators of the immune response, render these proteins as valuable tools to modulate immunopathologies and autoimmune disorders, as well as a potential treatment of neoplasms. Moreover, the disparities in the amino acid composition of parasite calreticulins might provide subtle variations in the mechanisms of action that could provide advantages as therapeutic tools. Here, we review the immunological roles of parasite calreticulins and discuss possible beneficial applications.

Extracellular vesicles derived from Spirometra erinaceieuropaei plerocercoids inhibit activation of murine macrophage RAW264.7 cells

Parasitic helminths modify host immune reactions to promote long-term parasitism. We previously purified a glycoprotein, plerocercoid-immunosuppressive factor (P-ISF), from the excretory/secretory products of Spirometra erinaceieuropaei plerocercoids and reported its cDNA and genomic DNA sequences. In this study, we isolated extracellular vesicles (EVs) from the excretory/secretory products of S. erinaceieuropaei plerocercoids and found that they suppressed the production of nitric oxide and the gene expression of tumor necrosis factor-α, interleukin-1β, and interleukin-6 in lipopolysaccharide-stimulated macrophages. EVs are membrane-bound vesicles 50-250 nm in diameter and are localized in the whole bodies of plerocercoids. EVs from plerocercoids encapsulate a variety of unidentified proteins and microRNAs (miRNAs), which are non-coding RNAs that play essential roles in post-transcriptional gene regulation. The miRNAs of the EVs were analyzed, and 334,137 sequencing reads were mapped to the genomes of other organisms. A total of 26 different miRNA families were identified, including miR-71, miR-10-5p, miR-223, and let-7-5p, which have been reported to have immunosuppressive effects. We confirmed that P-ISF was present in the supernatant but not in the EVs by western blotting with an anti-P-ISF antibody. These results suggest that S. erinaceieuropaei plerocercoids suppress host immunity by releasing P-ISF and EVs.

The Immune Response to Nematode Infection

Nematode infection is a major threat to the health of humans, domestic animals and wildlife. Nematodes vary in their effect on the host and in the mechanisms underlying immunity but the general features are becoming clear. There is considerable variation among individuals in resistance to infection and much of this variation is due to genetic variation in the immune response. The major histocompatibility complex has a strong influence on resistance to infection but other genes are collectively more important. Resistant individuals produce more IgA, eosinophils, IgE and mast cells than susceptible individuals and this is a consequence of stronger type 2 (Th2) immune responses. A variety of factors promote Th2 responses including genetic background, diet, molecules produced by the parasite and the location of the infection. A variety of cells and molecules including proteins, glycolipids and RNA act in concert to promote responses and to regulate the response. Nematodes themselves also modulate the host response and over 20 parasite-derived immunomodulatory molecules have been identified. Different species of nematodes modulate the immune response in different ways and probably use multiple molecules. The reasons for this are unclear and the interactions among immunomodulators have still to be investigated.

Secretion of extracellular vesicles during ontogeny of the tapeworm Schistocephalus solidus

We provide the first ultrastructural evidence of the secretion of extracellular vesicles (EVs) across all parasitic stages of the tapeworm Schistocephalus solidus (Müller, 1776) (Cestoda: Diphyllobothriidea) using a laboratory life cycle model. We confirmed the presence of EV-like bodies in all stages examined, including the hexacanth, procercoids in the copepod, Macrocyclops albidus (Jurine, 1820), plerocercoids from the body cavity of the three-spined stickleback, Gasterosteus aculeatus Linnaeus, and adults cultivated in artificial medium. In addition, we provide description of novel tegumental structures potentially involved in EV biogenesis and the presence of unique elongated EVs similar to those previously described only in Fasciola hepatica Linnaeus, 1758 (Trematoda), Hymenolepis diminuta (Rudolphi, 1819) (Cestoda), and Trypanosoma brucei Plimmer et Bradford, 1899 (Kinetoplastida).

Special considerations for studies of extracellular vesicles from parasitic helminths: A community-led roadmap to increase rigour and reproducibility

Over the last decade, research interest in defining how extracellular vesicles (EVs) shape cross-species communication has grown rapidly. Parasitic helminths, worm species found in the phyla Nematoda and Platyhelminthes, are well-recognised manipulators of host immune function and physiology. Emerging evidence supports a role for helminth-derived EVs in these processes and highlights EVs as an important participant in cross-phylum communication. While the mammalian EV field is guided by a community-agreed framework for studying EVs derived from model organisms or cell systems [e.g., Minimal Information for Studies of Extracellular Vesicles (MISEV)], the helminth community requires a supplementary set of principles due to the additional challenges that accompany working with such divergent organisms. These challenges include, but are not limited to, generating sufficient quantities of EVs for descriptive or functional studies, defining pan-helminth EV markers, genetically modifying these organisms, and identifying rigorous methodologies for in vitro and in vivo studies. Here, we outline best practices for those investigating the biology of helminth-derived EVs to complement the MISEV guidelines. We summarise community-agreed standards for studying EVs derived from this broad set of non-model organisms, raise awareness of issues associated with helminth EVs and provide future perspectives for how progress in the field will be achieved.

microRNAs: Critical Players during Helminth Infections

microRNAs (miRNAs) are a group of small non-coding RNAs that regulate gene expression post-transcriptionally through their interaction with the 3' untranslated regions (3' UTR) of target mRNAs, affecting their stability and/or translation. Therefore, miRNAs regulate biological processes such as signal transduction, cell death, autophagy, metabolism, development, cellular proliferation, and differentiation. Dysregulated expression of microRNAs is associated with infectious diseases, where miRNAs modulate important aspects of the parasite-host interaction. Helminths are parasitic worms that cause various neglected tropical diseases affecting millions worldwide. These parasites have sophisticated mechanisms that give them a surprising immunomodulatory capacity favoring parasite persistence and establishment of infection. In this review, we analyze miRNAs in infections caused by helminths, emphasizing their role in immune regulation and its implication in diagnosis, prognosis, and the development of therapeutic strategies.

Identification and characterization of extracellular vesicles from red cells infected with Babesia divergens and Babesia microti

Babesiosis is a zoonosis and an important blood-borne human parasitic infection that has gained attention because of its growing infection rate in humans by transfer from animal reservoirs. Babesia represents a potential threat to the blood supply because asymptomatic infections in man are common, and blood from such donors can cause severe disease in certain recipients. Extracellular vesicles (EVs) are vesicles released by cells that contain a complex mixture of proteins, lipids, glycans, and genetic information that have been shown to play important roles in disease pathogenesis and susceptibility, as well as cell–cell communication and immune responses. In this article, we report on the identification and characterization of EVs released from red blood cells (RBCs) infected by two major human Babesia species—Babesia divergens from in vitro culture and those from an in vivo B. microti mouse infection. Using nanoparticle tracking analysis, we show that there is a range of vesicle sizes from 30 to 1,000 nm, emanating from the Babesia-infected RBC. The study of these EVs in the context of hemoparasite infection is complicated by the fact that both the parasite and the host RBC make and release vesicles into the extracellular environment. However, the EV frequency is 2- to 10-fold higher in Babesia-infected RBCs than uninfected RBCs, depending on levels of parasitemia. Using parasite-specific markers, we were able to show that ~50%–60% of all EVs contained parasite-specific markers on their surface and thus may represent the specific proportion of EVs released by infected RBCs within the EV population. Western blot analysis on purified EVs from both in vivo and in vitro infections revealed several parasite proteins that were targets of the host immune response. In addition, microRNA analysis showed that infected RBC EVs have different microRNA signature from uninfected RBC EVs, indicating a potential role as disease biomarkers. Finally, EVs were internalized by other RBCs in culture, implicating a potential role for these vesicles in cellular communication. Overall, our study points to the multiple functional implications of EVs in Babesia–host interactions and support the potential that EVs have as agents in disease pathogenesis.

Helminth infection and helminth-derived products: A novel therapeutic option for non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is closely related to obesity, diabetes, and metabolic syndrome (MetS), and it has become the most common chronic liver disease. Helminths have co-evolved with humans, inducing multiple immunomodulatory mechanisms to modulate the host's immune system. By using their immunomodulatory ability, helminths and their products exhibit protection against various autoimmune and inflammatory diseases, including obesity, diabetes, and MetS, which are closely associated with NAFLD. Here, we review the pathogenesis of NAFLD from abnormal glycolipid metabolism, inflammation, and gut dysbiosis. Correspondingly, helminths and their products can treat or relieve these NAFLD-related diseases, including obesity, diabetes, and MetS, by promoting glycolipid metabolism homeostasis, regulating inflammation, and restoring the balance of gut microbiota. Considering that a large number of clinical trials have been carried out on helminths and their products for the treatment of inflammatory diseases with promising results, the treatment of NAFLD and obesity-related diseases by helminths is also a novel direction and strategy.

Knockout of liver fluke granulin, Ov-grn-1, impedes malignant transformation during chronic infection with Opisthorchis viverrini

Infection with the food-borne liver fluke Opisthorchis viverrini is the principal risk factor for cholangiocarcinoma (CCA) in the Mekong Basin countries of Thailand, Lao PDR, Vietnam, Myanmar and Cambodia. Using a novel model of CCA, involving infection with gene-edited liver flukes in the hamster during concurrent exposure to dietary nitrosamine, we explored the role of the fluke granulin-like growth factor Ov-GRN-1 in malignancy. We derived RNA-guided gene knockout flukes (ΔOv-grn-1) using CRISPR/Cas9/gRNA materials delivered by electroporation. Genome sequencing confirmed programmed Cas9-catalyzed mutations of the targeted genes, which was accompanied by rapid depletion of transcripts and the proteins they encode. Gene-edited parasites colonized the biliary tract of hamsters and developed into adult flukes. However, less hepatobiliary tract disease manifested during chronic infection with ΔOv-grn-1 worms in comparison to hamsters infected with control gene-edited and mock-edited parasites. Specifically, immuno- and colorimetric-histochemical analysis of livers revealed markedly less periductal fibrosis surrounding the flukes and less fibrosis globally within the hepatobiliary tract during infection with ΔOv-grn-1 genotype worms, minimal biliary epithelial cell proliferation, and significantly fewer mutations of TP53 in biliary epithelial cells. Moreover, fewer hamsters developed high-grade CCA compared to controls. The clinically relevant, pathophysiological phenotype of the hepatobiliary tract confirmed a role for this secreted growth factor in malignancy and morbidity during opisthorchiasis.

Proteomic analysis of the excretory-secretory products from Strongyloides venezuelensis infective larvae: new insights for the immunodiagnosis of human strongyloidiasis

Serodiagnosis of human strongyloidiasis is a practical alternative to parasitological methods due to its high sensitivity. However, cross-reactivity with other helminth infections limits its utility, and this problem is due to the use of homologous or heterologous somatic extracts of the parasite as an antigen source. Excretory-secretory (E/S) products from Strongyloides infective larvae can be used to improve the serodiagnosis. The combined use of western blot and proteomics became an interesting strategy to identify immunological markers for the serodiagnosis of strongyloidiasis. The present study describes the proteomic analysis of the antigenic components from E/S products of S. venezuelensis infective larvae that were recognized by IgG antibodies from patients with strongyloidiasis. Our results showed that IgG antibodies from patients with strongyloidiasis recognized between 15 and 16 antigenic bands in the E/S products from S. venezuelensis that were incubated in PBS or in RPMI culture medium, respectively. Overall, antigenic bands of low and high molecular weight were more specific than those of intermediate molecular weight, which were cross-reactive. A 36-kDa antigenic band was 93% sensitive and 100% specific (a probably arginine kinase of 37 kDa), while other antigenic bands were highly sensitive but low specific. Proteomic analysis revealed differences between the protein profiles from E/S-RPMI and E/S-PBS since only one-third of all proteins identified were common in both types of E/S products. Bioinformatic analysis showed that more than 50% of the proteins from E/S products are secreted within extracellular vesicles and only a small percentage of them are actually released by the classical secretory pathway. Several components from the E/S products were identified as plasminogen-binding proteins, probably used as an immune evasion mechanism. The data provided here provide valuable information to increase understanding of E/S products from S. venezuelensis infective larvae. This may help us to find new targets for the immunodiagnosis of human strongyloidiasis.

miRNAs in the regulation of mTOR signaling and host immune responses: The case of Leishmania infections

Micro RNAs (miRNAs), as regulators of gene expression at the post-transcriptional level, can respond to/or interact with cell signaling and affect the pathogenesis of different diseases/infections. The interaction/crosstalk of miRNAs with various cellular signaling networks including mTOR (as a master regulator of signaling relevant to different cellular mechanisms) might lead to the initiation, progression or restriction of certain disease processes. There are numerous studies that have identified the crosstalk between regulatory miRNA expression and the mTOR pathway (or mTOR signaling regulated by miRNAs) in different diseases which has a dual function in pathogenesis. However, the corresponding information in parasitic infections remains scarce. miRNAs have been suggested as specific targets for therapeutic strategies in several disorders such as parasitic infections. Thus, the targeting of miRNAs (as the modulators/regulators of mTOR) by small molecules and RNA-based therapeutics and consequently managing and modulating mTOR signaling and the downstream/related cell signaling/pathways might shed some light on the design of new therapeutic strategies against parasitic diseases, including Leishmaniasis. Accordingly, the present study attempts to highlight the importance of the crosstalk between regulatory miRNAs and mTOR signaling, and to review the relevant insights into parasitic infections by focusing specifically on Leishmania.

Isolation, profiling, and tracking of extracellular vesicle cargo in Caenorhabditis elegans

Extracellular vesicles (EVs) may mediate intercellular communication by carrying protein and RNA cargo. The composition, biology, and roles of EVs in physiology and pathology have been primarily studied in the context of biofluids and in cultured mammalian cells. The experimental tractability of C. elegans makes for a powerful in vivo animal system to identify and study EV cargo from its cellular source. We developed an innovative method to label, track, and profile EVs using genetically encoded, fluorescent-tagged EV cargo and conducted a large-scale isolation and proteomic profiling. Nucleic acid binding proteins (∼200) are overrepresented in our dataset. By integrating our EV proteomic dataset with single-cell transcriptomic data, we identified and validated ciliary EV cargo: CD9-like tetraspanin (TSP-6), ectonucleotide pyrophosphatase/phosphodiesterase (ENPP-1), minichromosome maintenance protein (MCM-3), and double-stranded RNA transporter SID-2. C. elegans EVs also harbor RNA, suggesting that EVs may play a role in extracellular RNA-based communication.

Comparison of separation methods for immunomodulatory extracellular vesicles from helminths

Helminths survive within their host by secreting immunomodulatory compounds, which hold therapeutic potential for inflammatory conditions. Helminth-derived extracellular vesicles (EVs) are one such component proposed to possess immunomodulatory activities. Due to the recent discovery of helminth EVs, standardised protocols for EV separation are lacking. Excretory/secretory products of the porcine helminth, Ascaris suum, were used to compare three EV separation methods: Size exclusion chromatography (SEC), ultracentrifugation (UC) and a combination of the two. Their performance was evaluated by EV yield, sample purity and the ability of EVs to suppress lipopolysaccharide (LPS)-induced inflammation in vitro. We found that all three separation methods successfully separated helminth EVs with a similar EV yield. Functional studies showed that EVs from all three methods reduced LPS-induced levels of tumour necrosis factor (TNF-α) in a dose-dependent manner. Overall, the three separation methods showed similar performance, however, the combination of UC+SEC presented with slightly higher purity than either method alone.

Sugar Coating: Utilisation of Host Serum Sialoglycoproteins by Schistosoma mansoni as a Potential Immune Evasion Mechanism

Parasitic helminths resort to various mechanisms to evade and modulate their host’s immune response, several of which have been described for Schistosoma mansoni. We recently reported the presence of sialic acid residues on the surface of adult S. mansoni extracellular vesicles (EVs). We now report that these sialylated molecules are mammalian serum proteins. In addition, our data suggest that most sialylated EV-associated proteins do not elicit a humoral response upon injection into mice, or in sera obtained from infected animals. Sialic acids frequently terminate glycans on the surface of vertebrate cells, where they serve important functions in physiological processes such as cell adhesion and signalling. Interestingly, several pathogens have evolved ways to mimic or utilise host sialic acid beneficially by coating their own proteins, thereby facilitating cell invasion and providing protection from host immune effectors. Together, our results indicate that S. mansoni EVs are coated with host glycoproteins, which may contribute to immune evasion by masking antigenic sites, protecting EVs from removal from serum and aiding in cell adhesion and entry to exert their functions.

The Role of Nuclear Factor Kappa B (NF-κB) in the Immune Response against Parasites

The immune system consists of various cells, organs, and processes that interact in a sophisticated manner to defend against pathogens. Upon initial exposure to an invader, nonspecific mechanisms are raised through the activation of macrophages, monocytes, basophils, mast cells, eosinophils, innate lymphoid cells, or natural killer cells. During the course of an infection, more specific responses develop (adaptive immune responses) whose hallmarks include the expansion of B and T cells that specifically recognize foreign antigens. Cell to cell communication takes place through physical interactions as well as through the release of mediators (cytokines, chemokines) that modify cell activity and control and regulate the immune response. One regulator of cell states is the transcription factor Nuclear Factor kappa B (NF-κB) which mediates responses to various stimuli and is involved in a variety of processes (cell cycle, development, apoptosis, carcinogenesis, innate and adaptive immune responses). It consists of two protein classes with NF-κB1 (p105/50) and NF-κB2 (p100/52) belonging to class I, and RelA (p65), RelB and c-Rel belonging to class II. The active transcription factor consists of a dimer, usually comprised of both class I and class II proteins conjugated to Inhibitor of κB (IκB). Through various stimuli, IκB is phosphorylated and detached, allowing dimer migration to the nucleus and binding of DNA. NF-κB is crucial in regulating the immune response and maintaining a balance between suppression, effective response, and immunopathologies. Parasites are a diverse group of organisms comprised of three major groups: protozoa, helminths, and ectoparasites. Each group induces distinct effector immune mechanisms and is susceptible to different types of immune responses (Th₁, Th₂, Th₁₇). This review describes the role of NF-κB and its activity during parasite infections and its contribution to inducing protective responses or immunopathologies.

Echinococcus granulosus Protoscolex DM9 Protein Shows High Potential for Serodiagnosis of Alveolar Echinococcosis

Alveolar echinococcosis (AE) caused by infection with E. multilocularis metacestode, represents one of the most fatal helminthic diseases. AE is principally manifested with infiltrative, proliferating hepatic mass, resembling primary hepatocellular carcinoma. Sometimes metastatic lesions are found in nearby or remote tissue. AE diagnosis largely depends on imaging studies, but atypical findings of imaging features frequently require differential diagnosis from other hepatic lesions. Serological tests may provide further evidence, while obtaining reliable AE materials is not easy. In this study, alternative antigens, specific to AE were identified by analyzing E. granulosus protoscolex proteins. An immunoblot analysis of E. granulosus protoscolex showed that a group of low-molecular-weight proteins in the range from 14 kDa to 16 kDa exhibited a sensitive and specific immune response to AE patient sera. Partial purification and proteomic analysis indicated that this protein group contained myosin, tubulin polymerization promoting protein, fatty-acid binding protein, uncharacterized DM9, heat shock protein 90 cochaperone tebp P-23, and antigen S. When the serological applicability of recombinant forms of these proteins was assessed using enzyme-linked immunosorbent assay, DM9 protein (rEgDM9) showed 90.1% sensitivity (73/81 sera tested) and 94.5% specificity (172/181 sera tested), respectively. rEgDM9 showed weak cross-reactions with patient sera from the transitional and chronic stages of cystic echinococcosis (3 to 5 stages). rEgDM9 would serve as a useful alternative antigen for serodiagnosis of both early- and advanced-stage AE cases.

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.

IL-33: A central cytokine in helminth infections

IL-33 is an alarmin cytokine which has been implicated in allergy, fibrosis, inflammation, tumorigenesis, metabolism, and homeostasis. However, amongst its strongest roles are in helminth infections, where IL-33 usually (but not always) is central to induction of an effective anti-parasitic immune response. In this review, we will summarise the literature around this fascinating cytokine, its activity on immune and non-immune cells, the unique (and sometimes counterintuitive) responses it induces, and how it can coordinate the immune response during infections by parasitic helminths. Finally, we will summarise some of the ways that parasites have developed to modulate the IL-33 pathway for their own benefit.

Pathogens and extracellular vesicles: New paths and challenges to understanding and treating diseases. Editorial opinion

Extracellular vesicles (EVs) have been described in all eukaryotic and prokaryotic cells as released membranous structures loaded with biomolecules including nucleic acids, glycoconjugates, lipids and proteins. Two main groups of vesicles with different biogenesis and size are considered to be the most predominant, Exosomes (30-100 nm) originating from multivesicular bodies, and microvesículas (100-1000 nm) originating from plasma membrane. EVs participate in cellular communication between different organisms and can alter neighbour cells, participating in physiological and pathophysiological processes. In this issue, eleven reviews summarize the current knowledge in the characterization of EVs participating in the pathogenic-host interaction including protozoa, helminths, bacteria, fungi and viruses (Montaño et al., 2021; Palacios et al., 2021; Rossi et al., 2021; Sabatke et al., 2021; Cucher et al., 2021; Gilmore W et al., 2021; Sánchez-López et al., 2021; Dong et al., 2021; Drurey C and Mayzels R.M., 2021; Macedo-Da Silva J et al., 2021; Piffer, A. C et al., 2021).