Regulatory T-cells in helminth infection: induction, function and therapeutic potential

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.

Fecal microbiota transplantation from protozoa-exposed donors downregulates immune response in a germ-free mouse model, its role in immune response and physiology of the intestine

Intestinal parasites are part of the intestinal ecosystem and have been shown to establish close interactions with the intestinal microbiota. However, little is known about the influence of intestinal protozoa on the regulation of the immune response. In this study, we analyzed the regulation of the immune response of germ-free mice transplanted with fecal microbiota (FMT) from individuals with multiple parasitic protozoans (P) and non-parasitized individuals (NP). We determined the production of intestinal cytokines, the lymphocyte populations in both the colon and the spleen, and the genetic expression of markers of intestinal epithelial integrity. We observed a general downregulation of the intestinal immune response in mice receiving FMT-P. We found significantly lower intestinal production of the cytokines IL-6, TNF, IFN-γ, MCP-1, IL-10, and IL-12 in the FMT-P. Furthermore, a significant decrease in the proportion of CD3+, CD4+, and Foxp3+ T regulatory cells (Treg) was observed in both, the colon and spleen with FMT-P in contrast to FMT-NP. We also found that in FMT-P mice there was a significant decrease in tjp1 expression in all three regions of the small intestine; ocln in the ileum; reg3γ in the duodenum and relmβ in both the duodenum and ileum. We also found an increase in colonic mucus layer thickness in mice colonized with FMT-P in contrast with FMT-NP. Finally, our results suggest that gut protozoa, such as Blastocystis hominis, Entamoeba coli, Endolimax nana, Entamoeba histolytica/E. dispar, Iodamoeba bütschlii, and Chilomastix mesnili consortia affect the immunoinflammatory state and induce functional changes in the intestine via the gut microbiota. Likewise, it allows us to establish an FMT model in germ-free mice as a viable alternative to explore the effects that exposure to intestinal parasites could have on the immune response in humans.

The rebalancing of the immune system at the maternal-fetal interface ameliorates autism-like behavior in adult offspring

Maternal immune activation (MIA) is critical for imparting neuropathology and altered behaviors in offspring; however, maternal-fetal immune cell populations have not been thoroughly investigated in MIA-induced autism spectrum disorders (ASDs). Here, we report the single-cell transcriptional landscape of placental cells in both PBS- and poly(I:C)-induced MIA dams. We observed a decrease in regulatory T (Treg) cells but an increase in the M1 macrophage population at the maternal-fetal interface in MIA dams. Based on the Treg-targeting approach, we investigate an immunoregulatory protein, the helminth-derived heat shock protein 90α (Sjp90α), that induces maternal Treg cells and subsequently rescues the autism-like behaviors in adult offspring. Furthermore, in vivo depletion of maternal macrophages attenuates placental inflammatory reaction and reverses behavioral abnormalities in adult offspring. Notably, Sjp90α induces CD4+ T cell differentiation via scavenger receptor A (SR-A) on the macrophage in vitro. Our findings suggest a maternal Treg-targeted approach to alleviate MIA-induced autism-like behavior in adult offspring.

Diversity of aquatic parasites in pristine spring waters in Tehsil Babuzai, Swat, Pakistan

Global access to clean and safe drinking water remains a formidable challenge, contributing to a myriad of health issues. This research exposes the existence of waterborne parasites in seemingly pristine spring waters, indicating potential contamination. Daily extensive sampling of Seventeen water sources was conducted in the untarnished freshwater streams of Tehsil Babuzai, District Swat, Khyber Pakhtunkhwa, Pakistan, from February to September 2021. Employing a stringent filtration process, the collected samples were effectively concentrated to detect any waterborne parasites. Subsequent application of the wet mount technique, combined with the capabilities of a compound microscope, revealed a disconcerting reality: all examined samples tested positive for various parasites. Identified parasites included Schistosoma species, Ascaris lumbricoides, Trichiuria trichiuria, Taenia saginata, Entamoeba histolytica, Amoeba, Lacrymana olor, Tintinnids, Paramecium, Dileptus, Euglena, Loxodes striatus, Acanthocyclops lynceus, Spondylosium, Oscillatoria, Cyanobacteria, Cilindros, Cilindros cerro, Commensal amoeba mature cysts,, Filliform larva of Strongyloides, Cercaria larva, Larva of Taenia solium, Egg of Enterobius vermiculais, Egg of Isospora belli, Egg of Tapeworm, Egg of Schistosoma species, Egg of Toxocara, and Egg of Diphyllobothrium latum. These findings clearly demonstrate the presence of a diverse array of parasites in the freshwater springs of Tehsil Babuzai, Swat, Pakistan. Implementing robust water treatment protocols, conducting regular monitoring and testing, and raising awareness about the risks of waterborne parasites are crucial steps to safeguard public health in the region.

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.

Gene: environment interactions in immune and inflammatory responses to severe acute respiratory syndrome coronavirus 2 infection

Despite its devastating human cost, the rapid spread and global establishment of the severe acute respiratory syndrome coronavirus (SARS-CoV-2) pandemic had the benefit of providing unique insights into the intricate interplay between genetic, environmental, and socioeconomic factors, which collectively impact susceptibility to infection with SARS-CoV-2. Preceding the implementation of broad vaccination programs and assuming the absence of significant acquired immunity, examining the innate vulnerability to the virus becomes essential. There is indeed considerable heterogeneity observed at both the population and individual levels for various SARS-CoV-2 infection phenotypes, including emergence, progression, and survival from the coronavirus disease 2019 (COVID-19) syndrome. Particularly intriguing is the seemingly milder course of COVID-19 disease reported for the African continent early during the pandemic. This was characterized by significantly lower mortality rates in SARS-CoV-2 patients compared with the European and American continents and globally. We will discuss some of the demographic and socioeconomic factors that may have contributed to these observations. We review the mapped COVID-19 genetic architecture, including the remarkable association of type I interferon as a single protective mechanism and a major determinant of susceptibility. Furthermore, we speculate on potential 'environmental' modulators of penetrance and expressivity of intrinsic vulnerability factors, with a focus on the microbiome and associated metabolomes. Additionally, this review explores the potential immunomodulatory contribution of helminth parasites to the human host immune and inflammatory responses to respiratory viral infections.

Concurrent Ascaris infection modulates host immunity resulting in impaired control of Salmonella infection in pigs

Ascaris is one of the most widespread helminth infections, leading to chronic morbidity in humans and considerable economic losses in pig farming. In addition, pigs are an important reservoir for the zoonotic salmonellosis, where pigs can serve as asymptomatic carriers. Here, we investigated the impact of an ongoing Ascaris infection on the immune response to Salmonella in pigs. We observed higher bacterial burdens in experimentally coinfected pigs compared to pigs infected with Salmonella alone. The impaired control of Salmonella in the coinfected pigs was associated with repressed interferon gamma responses in the small intestine and with the alternative activation of gut macrophages evident in elevated CD206 expression. Ascaris single and coinfection were associated with a rise of CD4-CD8α+FoxP3+ Treg in the lymph nodes draining the small intestine and liver. In addition, macrophages from coinfected pigs showed enhanced susceptibility to Salmonella infection in vitro and the Salmonella-induced monocytosis and tumor necrosis factor alpha production by myeloid cells was repressed in pigs coinfected with Ascaris. Hence, our data indicate that acute Ascaris infection modulates different immune effector functions with important consequences for the control of tissue-invasive coinfecting pathogens.IMPORTANCEIn experimentally infected pigs, we show that an ongoing infection with the parasitic worm Ascaris suum modulates host immunity, and coinfected pigs have higher Salmonella burdens compared to pigs infected with Salmonella alone. Both infections are widespread in pig production and the prevalence of Salmonella is high in endemic regions of human Ascariasis, indicating that this is a clinically meaningful coinfection. We observed the type 2/regulatory immune response to be induced during an Ascaris infection correlates with increased susceptibility of pigs to the concurrent bacterial infection.

Immunohistochemistry analyses of the abomasal mucosa show differences in cellular-mediated immune responses to Haemonchus contortus infection in resistant and susceptible young lambs

Haemonchus contortus is known for its high pathogenicity in sheep, and the uncontrolled use of anthelmintics resulted in the emergence of multiple drug-resistant populations. Breeding sheep for gastrointestinal nematode resistance is a sustainable alternative to reduce dependence of anthelmintic drugs, and differences in the degree of resistance between breeds have been reported. Here we compare two sheep breeds (Santa Ines and Ile de France), concerning the differences in innate and adaptive immune response involved in the resistance against H. contortus infection. Immunohistochemical analyses of the abomasum were conducted in naïve Santa Ines (n = 14) and Ile de France (n = 12) lambs randomized into four groups: infected Santa Ines (n = 8), non-infected control Santa Ines (n = 6), infected Ile de France (n = 8), and non-infected control Ile de France (n = 4). The infected lambs were initially infected with H. contortus infective larvae at 14 days of age, and multiple infections were conducted every second day until they reached 66 days of age. There was a significant effect (P < 0.001) of the infection with increase in numbers of CD3+ T; CD79α+ B; GATA3+ Th2/ILC2; POU2F3+ tuft cells; FOXP3+ T reg; and IgE + cells in the fundus of the abomasal mucosa in both Santa Ines and Ile de France lambs. Nevertheless, the infected Santa Ines lambs presented the highest averages for CD79α+ B; GATA3+ Th2/ILC; IgE + cells; and POU2F3+ tuft cells and there was a significant association of the breed and infection status with regards to POU2F3+ tuft cells, with the highest mean in the infected Santa Ines group. The infected Santa Ines group had three lambs with high degree of resistance and five lambs that showed a moderate infection. Our results suggest a mechanism of synergistic coordination between different immune-cell types in promoting resistance of suckling lambs under H. contortus infection.

Cutaneous Leishmaniasis Hampers COVID-19: A Controlled Cross-Sectional Study in High-Burden Endemic Areas of Iran

INTRODUCTION

Emerging infectious diseases such as SARS-CoV-2 can cause pandemics and create a critical risk for humans. In a previous pilot study, we reported that the immunological responses induced by cutaneous leishmaniasis (CL) could decrease the incidence and severity of COVID-19. In this large-scale case-control study, we assessed the possible relationship between mortality and morbidity of COVID-19 in healed CL persons suffering scars compared to cases without CL history.

METHODS

This controlled cross-sectional study was conducted between July 2020 and December 2022 in the endemic and high-burden areas of CL in southeastern Iran. In the study, 1400 previous CL cases with scars and 1,521,329 subjects who had no previous CL were analyzed. We used R 4.0.2 to analyze the data. Firth's bias reduction approach corresponding to the penalization of likelihood logistic regression by Jeffreys was also employed to influence the variables in the dataset. Also, a Bayesian ordinal logistic regression model was performed to explore the COVID-19 severity in both case and referent groups.

RESULTS

The occurrence and severity rate of COVID-19 in CL scar cases are significantly less than in the non-CL control group, while in the CL scar subjects, patients with critical conditions and mortality were not observed. The morbidity (OR = 0.11, CI 0.06-0.20 and P < 0.001) and severity of COVID-19 in previous cases with CL scars were significantly diminished than that in the control group (credible interval - 2.57, - 1.62).

CONCLUSIONS

The results represented a durable negative relationship between cured CL and COVID-19 incidence and severity. Additional studies seem necessary and should be designed to further validate the true impact and underlying mechanistic action of CL on COVID-19.

Serine protease inhibitor from the muscle larval Trichinella spiralis ameliorates non-alcoholic fatty liver disease in mice via anti-inflammatory properties and gut-liver crosstalk

Trichinella spiralis is recognized for its ability to regulate host immune responses. The serine protease inhibitor of T. spiralis (Ts-SPI) participates in T. spiralis-mediated immunoregulatory effects. Studies have shown that helminth therapy exhibits therapeutic effects on metabolic diseases. In addition, we previously found that T. spiralis-derived crude antigens could alleviate diet-induced obesity. Thus, Ts-SPI was hypothesized to alleviate non-alcoholic fatty liver disease (NAFLD). Herein, recombinant Ts-SPI (rTs-SPI) was prepared from the muscle larvae T. spiralis. The relative molecular mass of rTs-SPI was approximately 35,000 Da, and western blot analysis indicated good immunoreactivity. rTs-SPI ameliorated hepatic steatosis, inflammation, and pyroptosis in NAFLD mice, which validated the hypothesis. rTs-SPI also reduced macrophage infiltration, significantly expanded Foxp3+ Treg population, and inactivated TLR4/NF-κB/NLRP3 signaling in the liver. Furthermore, rTs-SPI treatment significantly shifted the gut microbiome structure, with a remarkable increase in beneficial bacteria and reduction in harmful bacteria to improve gut barrier integrity. Finally, Abx-treated mice and FMT confirmed that gut-liver crosstalk contributed to NAFLD improvement after rTs-SPI treatment. Taken together, Taken together, these findings suggest that rTs-SPI exerts therapeutic effects in NAFLD via anti-inflammatory activity and gut-liver crosstalk.

An Update on the Pathogenesis of Fascioliasis: What Do We Know?

Fasciola hepatica is a trematode parasite distributed worldwide. It is known to cause disease in mammals, producing significant economic loses to livestock industry and burden to human health. After ingestion, the parasites migrate through the liver and mature in the bile ducts. A better understanding of the parasite's immunopathogenesis would help to develop efficacious therapeutics and vaccines. Currently, much of our knowledge comes from in vitro and in vivo studies in animal models. Relatively little is known about the host-parasite interactions in humans. Here, we provide a narrative review of what is currently know about the pathogenesis and host immune responses to F. hepatica summarizing the evidence available from the multiple hosts that this parasite infects.

Recognition of Highly Branched N-Glycans of the Porcine Whipworm by the Immune System

Glycans are key to host-pathogen interactions, whereby recognition by the host and immunomodulation by the pathogen can be mediated by carbohydrate binding proteins, such as lectins of the innate immune system, and their glycoconjugate ligands. Previous studies have shown that excretory-secretory products of the porcine nematode parasite Trichuris suis exert immunomodulatory effects in a glycan-dependent manner. To better understand the mechanisms of these interactions, we prepared N-glycans from T. suis and both analyzed their structures and used them to generate a natural glycan microarray. With this array, we explored the interactions of glycans with C-type lectins, C-reactive protein, and sera from T. suis-infected pigs. Glycans containing LacdiNAc and phosphorylcholine-modified glycans were associated with the highest binding by most of these proteins. In-depth analysis revealed not only fucosylated LacdiNAc motifs with and without phosphorylcholine moieties but phosphorylcholine-modified mannose and N-acetylhexosamine-substituted fucose residues, in the context of maximally tetraantennary N-glycan scaffolds. Furthermore, O-glycans also contained fucosylated motifs. In summary, the glycans of T. suis are recognized by both the innate and adaptive immune systems and also exhibit species-specific features distinguishing its glycome from those of other nematodes.

The COVID-19 Severity and Its Association with Intestinal Parasite Coinfection and Urine Biochemical Parameters among COVID-19-Confirmed Patients Admitted to Debre Markos University COVID-19 Center, Northwest Ethiopia

Background

Though most people with COVID-19 disease show asymptomatic to mild illness, a substantial number of patients are at high risk of developing severe disease and adverse outcomes with long COVID-19 and death. Even though some studies showed that previously existing infections with parasites amend the host's body defenses to increase resistance to infection with SARS-CoV-2, there is limited data in Ethiopia.

Objectives

This study is aimed at determining the COVID-19 disease severity and its association with intestinal parasite coinfection and urine biochemical parameters among COVID-19-confirmed patients admitted at Debre Markos University COVID-19 Center, 2021.

Methods

A prospective cohort study was conducted on 136 RT-qPCR-confirmed COVID-19 patients admitted at Debre Markos University COVID-19 Center from January 1 to March 30, 2021. Sociodemographic and clinical data were collected by using standardized data collection forms. A urine biochemical test was performed using a dry urine dipstick kit and stool examination using direct wet mount microscopic examination and formalin-ether concentration method. The chi-square test, Fisher exact test, and ordinal logistic regression analysis were computed to assess association with outcome variables using Statistical Package for Social Science software (version 24).

Result

A total of 136 COVID-19-confirmed patients participated in this study. The median age of the participants was 48 years. The majority (86 (62.5%)) of them were male in sex. Of the 136 cases, 39 (28.7%) had died. Among the 136 patients, 22 (16.2%) were coinfected with intestinal parasites. COVID-19 patients who have intestinal parasite coinfection had lower odds of developing clinically severe COVID-19 compared to noninfected (AOR = 0.37; 95% CI = 0.147-0.944; P = 0.037). The majority (104 (76.5%)) of them have abnormal urine biochemical results. From the abnormal urine biochemical tests observed, the urine blood, glucose, and ketone tests were positive for 54 (39.7%), 36 (26.5%), and 30 (21.1%) patients, respectively. Among the 31 critical COVID-19 patients, 25 (80.6%) showed abnormal urine biochemical parameters. Age and comorbidity were significantly associated with COVID-19 severity (P < 0.05).

Conclusion

Patients with old age and comorbidity had an increased risk of developing severe COVID-19 disease. Patients having SARS-CoV-2 and intestinal parasitic coinfections demonstrated mild COVID-19 disease severity. Abnormal urine biochemical results were common among critical COVID-19 patients. Thus, advanced study on the effect of the interaction among intestinal parasites on COVID-19 clinical severity and its mechanisms is essential.

The Roles of Various Immune Cell Populations in Immune Response against Helminths

Helminths are multicellular parasites that are a substantial problem for both human and veterinary medicine. According to estimates, 1.5 billion people suffer from their infection, resulting in decreased life quality and burdens for healthcare systems. On the other hand, these infections may alleviate autoimmune diseases and allergy symptoms. The immune system is programmed to combat infections; nevertheless, its effector mechanisms may result in immunopathologies and exacerbate clinical symptoms. This review summarizes the role of the immune response against worms, with an emphasis on the Th2 response, which is a hallmark of helminth infections. We characterize non-immune cells (enteric tuft cells-ETCs) responsible for detecting parasites, as well as the role of hematopoietic-derived cells (macrophages, basophils, eosinophils, neutrophils, innate lymphoid cells group 2-ILC2s, mast cells, T cells, and B cells) in initiating and sustaining the immune response, as well as the functions they play in granulomas. The aim of this paper is to review the existing knowledge regarding the immune response against helminths, to attempt to decipher the interactions between cells engaged in the response, and to indicate the gaps in the current knowledge.

Prevalence of pharmaceuticals and personal care products, microplastics and co-infecting microbes in the post-COVID-19 era and its implications on antimicrobial resistance and potential endocrine disruptive effects

The COVID-19 (coronavirus disease 2019) pandemic's steady condition coupled with predominance of emerging contaminants in the environment and its synergistic implications in recent times has stoked interest in combating medical emergencies in this dynamic environment. In this context, high concentrations of pharmaceutical and personal care products (PPCPs), microplastics (MPs), antimicrobial resistance (AMR), and soaring coinfecting microbes, tied with potential endocrine disruptive (ED) are critical environmental concerns that requires a detailed documentation and analysis. During the pandemic, the identification, enumeration, and assessment of potential hazards of PPCPs and MPs and (used as anti-COVID-19 agents/applications) in aquatic habitats have been attempted globally. Albeit receding threats in the magnitude of COVID-19 infections, both these pollutants have still posed serious consequences to aquatic ecosystems and the very health and hygiene of the population in the vicinity. The surge in the contaminants post-COVID also renders them to be potent vectors to harbor and amplify AMR. Pertinently, the present work attempts to critically review such instances to understand the underlying mechanism, interactions swaying the current health of our environment during this post-COVID-19 era. During this juncture, although prevention of diseases, patient care, and self-hygiene have taken precedence, nevertheless antimicrobial stewardship (AMS) efforts have been overlooked. Unnecessary usage of PPCPs and plastics during the pandemic has resulted in increased emerging contaminants (i.e., active pharmaceutical ingredients and MPs) in various environmental matrices. It was also noticed that among COVID-19 patients, while the bacterial co-infection prevalence was 0.2-51%, the fungi, viral, protozoan and helminth were 0.3-49, 1-22, 2-15, 0.4-15% respectively, rendering them resistant to residual PPCPs. There are inevitable chances of ED effects from PPCPs and MPs applied previously, that could pose far-reaching health concerns. Furthermore, clinical and other experimental evidence for many newer compounds is very scarce and demands further research. Pro-active measures targeting effective waste management, evolved environmental policies aiding strict regulatory measures, and scientific research would be crucial in minimizing the impact and creating better preparedness towards such events among the masses fostering sustainability.

The helminth TGF-β mimic TGM4 is a modular ligand that binds CD44, CD49d and TGF-β receptors to preferentially target myeloid cells

The murine helminth parasite Heligmosomoides polygyrus expresses a family of modular proteins which, replicating the functional activity of the immunomodulatory cytokine TGF-β, have been named TGM (TGF-β Μimic). Multiple domains bind to different receptors, including TGF-β receptors TβRI (ALK5) and TβRII through domains 1-3, and prototypic family member TGM1 binds the cell surface co-receptor CD44 through domains 4-5. This allows TGM1 to induce T lymphocyte Foxp3 expression, characteristic of regulatory (Treg) cells, and to activate a range of TGF-β-responsive cell types. In contrast, a related protein, TGM4, targets a much more restricted cell repertoire, primarily acting on myeloid cells, with less potent effects on T cells and lacking activity on other TGF-β-responsive cell types. TGM4 binds avidly to myeloid cells by flow cytometry, and can outcompete TGM1 for cell binding. Analysis of receptor binding in comparison to TGM1 reveals a 10-fold higher affinity than TGM1 for TGFβR-I (TβRI), but a 100-fold lower affinity for TβRII through Domain 3. Consequently, TGM4 is more dependent on co-receptor binding; in addition to CD44, TGM4 also engages CD49d (Itga4) through Domains 1-3, as well as CD206 and Neuropilin-1 through Domains 4 and 5. TGM4 was found to effectively modulate macrophage populations, inhibiting lipopolysaccharide-driven inflammatory cytokine production and boosting interleukin (IL)-4-stimulated responses such as Arginase-1 in vitro and in vivo. These results reveal that the modular nature of TGMs has allowed the fine tuning of the binding affinities of the TβR- and co-receptor binding domains to establish cell specificity for TGF-β signalling in a manner that cannot be attained by the mammalian cytokine.

A prospective study of the association between living in a rural environment during childhood and risk of psoriasis

Psoriasis is one of the most common immune-mediated inflammatory diseases (IMIDs). Living in a rural environment during childhood is associated with a decreased risk of certain IMIDs, like asthma, in adulthood. However, its role in other IMIDs, such as psoriasis is still unclear. To evaluate the relationships between different factors related to the environment during childhood and the risk of psoriasis in adulthood we conducted a study in E3N, a French prospective cohort composed of 98 995 women. During the 1990-2018 follow-up of 72 154 study participants, we identified 1 967 incident cases of psoriasis from self-reports in self-administered structured questionnaires. During the 2004-2018 follow-up of 67 917 study participants, 188 moderate-to-severe cases of psoriasis were identified through self-reports and from data from a drug reimbursement database. We fitted Cox proportional hazards regression models with age as the time scale from which we estimated hazard ratios adjusted for putative confounders (aHRs). We found inverse associations with risk of psoriasis for rural birthplace [aHR: 0.89 (95%CI: 0.79-0.96)] and for having farming parents [aHR: 0.84 (95%CI: 0.72-0.97)]. For moderate-to-severe psoriasis we found a nominally similar inverse association with rural birthplace but not with having farming parents. Our results suggest that an exposure to a rural environment during childhood may be associated with a reduced risk of psoriasis. These findings may help to improve our understanding of the pathogenesis of psoriasis.

Helminths' therapeutic potential to treat intestinal barrier dysfunction

The intestinal barrier is a dynamic multi-layered structure which can adapt to environmental changes within the intestinal lumen. It has the complex task of allowing nutrient absorption while limiting entry of harmful microbes and microbial antigens present in the intestinal lumen. Excessive entry of microbial antigens via microbial translocation due to 'intestinal barrier dysfunction' is hypothesised to contribute to the increasing incidence of allergic, autoimmune and metabolic diseases, a concept referred to as the 'epithelial barrier theory'. Helminths reside in the intestinal tract are in intimate contact with the mucosal surfaces and induce a range of local immunological changes which affect the layers of the intestinal barrier. Helminths are proposed to prevent, or even treat, many of the diseases implicated in the epithelial barrier theory. This review will focus on the effect of helminths on intestinal barrier function and explore whether this could explain the proposed health benefits delivered by helminths.

Wuchereria bancrofti infection is associated with progression to clinical visceral leishmaniasis in VL- endemic areas in Muzaffarpur, Bihar, India

BACKGROUND

Co-endemicity of neglected tropical diseases (NTDs) necessitates that these diseases should be considered concomitantly to understand the relationship between pathology and to support disease management and control programs. The aims of the study were to assess the prevalence of filarial infection in asymptomatic Leishmania donovani infected individuals and the correlation of Wuchereria bancrofti infection with progression to clinical visceral leishmaniasis (VL) in Bihar, India.

METHODOLOGY/PRINCIPAL FINDINGS

Within the Muzaffarpur-TMRC Health and Demographic Surveillance System (HDSS) area, a cohort of Leishmania seropositive (n = 476) or seronegative individuals (n = 1130) were sampled annually for three years for filarial infection and followed for progression to clinical VL. To corroborate the results from the cohort study, we also used a retrospective case-control study of 36 VL cases and 71 controls selected from a subset of the HDSS population to investigate the relationship between progression to clinical VL and the prevalence of filarial infection at baseline. Our findings suggest a higher probability of progression to clinical VL in individuals with a history of filarial infection: in both the cohort and case-control studies, progression to clinical VL was higher among filaria infected individuals (RR = 2.57, p = 0.056, and OR = 2.52, p = 0.046 respectively).

CONCLUSION

This study describes that progression to clinical VL disease is associated with serological evidence of prior infection with W. bancrofti. The integration of disease programs for Leishmania and lymphatic filariasis extend beyond the relationship of sequential or co-infection with disease burden. To ensure elimination targets can be reached and sustained, we suggest areas of co-endemicity would benefit from overlapping vector control activities, health system networks and surveillance infrastructure.

Recognition of highly branched N-glycans of the porcine whipworm by the immune system

Glycans are key to host-pathogen interactions, whereby recognition by the host and immunomodulation by the pathogen can be mediated by carbohydrate binding proteins, such as lectins of the innate immune system, and their glycoconjugate ligands. Previous studies have shown that excretory-secretory products of the porcine nematode parasite Trichuris suis exert immunomodulatory effects in a glycan-dependent manner. To better understand the mechanisms of these interactions, we prepared N-glycans from T. suis and both analyzed their structures and used them to generate a natural glycan microarray. With this array we explored the interactions of glycans with C-type lectins, C-reactive protein and sera from T. suis infected pigs. Glycans containing LacdiNAc and phosphorylcholine-modified glycans were associated with the highest binding by most of these proteins. In-depth analysis revealed not only fucosylated LacdiNAc motifs with and without phosphorylcholine moieties, but phosphorylcholine-modified mannose and N-acetylhexosamine-substituted fucose residues, in the context of maximally tetraantennary N-glycan scaffolds. Furthermore, O-glycans also contained fucosylated motifs. In summary, the glycans of T. suis are recognized by both the innate and adaptive immune systems, and also exhibit species-specific features distinguishing its glycome from those of other nematodes.

Another decade of Trichuris muris research: An update and application of key discoveries

The mouse whipworm, Trichuris muris, has been used for over 60 years as a tractable model for human trichuriasis, caused by the related whipworm species, T. trichiura. The history of T. muris research, from the discovery of the parasite in 1761 to understanding the lifecycle and outcome of infection with different doses (high versus low dose infection), as well as the immune mechanisms associated with parasite expulsion and chronic infection have been detailed in an earlier review published in 2013. Here, we review recent advances in our understanding of whipworm biology, host-parasite interactions and basic immunology brought about using the T. muris mouse model, focussing on developments from the last decade. In addition to the traditional high/low dose infection models that have formed the mainstay of T. muris research to date, novel models involving trickle (repeated low dose) infection in laboratory mice or infection in wild or semi-wild mice have led to important insights into how immunity develops in situ in a multivariate environment, while the use of novel techniques such as the development of caecal organoids (enabling the study of larval development ex vivo) promise to deliver important insights into host-parasite interactions. In addition, the genome and transcriptome analyses of T. muris and T. trichiura have proven to be invaluable tools, particularly in the context of vaccine development and identification of secreted products including proteins, extracellular vesicles and micro-RNAs, shedding further light on how these parasites communicate with their host and modulate the immune response to promote their own survival.

Regulatory T cells in parasite infections: susceptibility, specificity and specialisation

Regulatory T cells (Tregs) are essential to control immune system responses to innocuous self-specificities, intestinal and environmental antigens. However, they may also interfere with immunity to parasites, particularly in chronic infection. Susceptibility to many parasite infections is, to a greater or lesser extent, controlled by Tregs, but often they play a more prominent role in moderating the immunopathological consequences of parasitism, and dampening bystander reactions in an antigen-nonspecific manner. More recently, Treg subtypes have been defined which may preferentially act in different contexts; we also discuss the degree to which this specialisation is now being mapped onto how Tregs maintain the delicate balance between tolerance, immunity, and pathology in infection.

Interaction between tissue-dwelling helminth and the gut microbiota drives mucosal immunoregulation

Tissue-dwelling helminths affect billions of people around the world. They are potent manipulators of the host immune system, prominently by promoting regulatory T cells (Tregs) and are generally associated with a modified host gut microbiome. However, the role of the gut microbiota in the immunomodulatory processes for these non-intestinal parasites is still unclear. In the present study, we used an extra-intestinal cestode helminth model-larval Echinococcus multilocularis to explore the tripartite partnership (host-helminth-bacteria) in the context of regulating colonic Tregs in Balb/c mice. We showed that larval E. multilocularis infection in the peritoneal cavity attenuated colitis in Balb/c mice and induced a significant expansion of colonic Foxp3⁺ Treg populations. Fecal microbiota depletion and transplantation experiments showed that the gut microbiota contributed to increasing Tregs after the helminth infection. Shotgun metagenomic and metabolic analyses revealed that the gut microbiome structure after infection was significantly shifted with a remarkable increase of Lactobacillus reuteri and that the microbial metabolic capability was reprogrammed to produce more Treg cell regulator-short-chain fatty acids in feces. Furthermore, we also prove that the L. reuteri strain elevated in infected mice was sufficient to promote the colonic Treg frequency and its growth was potentially associated with T cell-dependent immunity in larval E. multilocularis infection. Collectively, these findings indicate that the extraintestinal helminth drives expansions of host colonic Tregs through the gut microbes. This study suggests that the gut microbiome serves as a critical component of anti-inflammation effects even for a therapy based on an extraintestinal helminth.

T cells in health and disease

T cells are crucial for immune functions to maintain health and prevent disease. T cell development occurs in a stepwise process in the thymus and mainly generates CD4+ and CD8+ T cell subsets. Upon antigen stimulation, naïve T cells differentiate into CD4+ helper and CD8+ cytotoxic effector and memory cells, mediating direct killing, diverse immune regulatory function, and long-term protection. In response to acute and chronic infections and tumors, T cells adopt distinct differentiation trajectories and develop into a range of heterogeneous populations with various phenotype, differentiation potential, and functionality under precise and elaborate regulations of transcriptional and epigenetic programs. Abnormal T-cell immunity can initiate and promote the pathogenesis of autoimmune diseases. In this review, we summarize the current understanding of T cell development, CD4+ and CD8+ T cell classification, and differentiation in physiological settings. We further elaborate the heterogeneity, differentiation, functionality, and regulation network of CD4+ and CD8+ T cells in infectious disease, chronic infection and tumor, and autoimmune disease, highlighting the exhausted CD8+ T cell differentiation trajectory, CD4+ T cell helper function, T cell contributions to immunotherapy and autoimmune pathogenesis. We also discuss the development and function of γδ T cells in tissue surveillance, infection, and tumor immunity. Finally, we summarized current T-cell-based immunotherapies in both cancer and autoimmune diseases, with an emphasis on their clinical applications. A better understanding of T cell immunity provides insight into developing novel prophylactic and therapeutic strategies in human diseases.

Evaluation of IL-35, as a Possible Biomarker for Follow-Up after Therapy, in Chronic Human Schistosoma Infection

The host response to helminth infections is characterized by systemic and tissue-related immune responses that play a crucial role in pathological diseases. Recently, experimental studies have highlighted the role of regulatory T (Tregs) and B (Bregs) cells with secreted cytokines as important markers in anti-schistosomiasis immunity. We investigated the serical levels of five cytokines (TNFα, IFN-γ, IL-4, IL-10 and IL-35) in pre- and post-treatment samples from chronic Schistosoma infected patients to identify potential serological markers during follow-up therapy. Interestingly, we highlighted an increased serum level of IL-35 in the pre-therapy samples (median 439 pg/mL for Schistosoma haematobium and 100.5 pg/mL for Schistsoma mansoni infected patients) compared to a control group (median 62 pg/mL and 58 pg/mL, respectively, p ≤ 0.05), and a significantly lower concentration in post-therapy samples (181 pg/mL for S. haematobium and 49.5 pg/mL for S. mansoni infected patients, p ≤ 0.05). The present study suggests the possible role of IL-35 as a novel serological biomarker in the evaluation of Schistosoma therapy follow-up.

Characterization of excretory/secretory products of the Taenia crassiceps cysticercus involved in the induction of regulatory T cells in vivo

The ability to modulate the host immune response has allowed some parasites to establish themselves in the tissues of an immunocompetent organism. While some parasite excretion/secretion products (ESPs) were recently reported to induce differentiation of regulatory T cells (Tregs), their identity is not known. This work is aimed to identify and characterize ESPs of Taenia crassiceps cysticerci linked with Treg induction in vivo. ESPs were obtained from cultures of T. crassiceps cysticerci and inoculated in mice, measuring Treg levels by flow cytometry. Proteins in ESPs were analyzed by electrophoresis; then, ESPs were classified as either differential or conserved. Differentially included proteins were MS-sequenced and functionally characterized. Only 4 of 10 ESPs induced Tregs. Proteins with catalytic activity and those involved in immunological processes predominated, supporting the idea that these molecules could play an important role in the induction of Tregs.

Helminth Lessons in Inflammatory Bowel Diseases (IBD)

Helminths are multicellular invertebrates that colonize the gut of many vertebrate animals including humans. This colonization can result in pathology, which requires treatment. It can also lead to a commensal and possibly even a symbiotic relationship where the helminth and the host benefit from each other's presence. Epidemiological data have linked helminth exposure to protection from immune disorders that include a wide range of diseases, such as allergies, autoimmune illnesses, and idiopathic inflammatory disorders of the gut, which are grouped as inflammatory bowel diseases (IBD). Treatment of moderate to severe IBD involves the use of immune modulators and biologics, which can cause life-threatening complications. In this setting, their safety profile makes helminths or helminth products attractive as novel therapeutic approaches to treat IBD or other immune disorders. Helminths stimulate T helper-2 (Th2) and immune regulatory pathways, which are targeted in IBD treatment. Epidemiological explorations, basic science studies, and clinical research on helminths can lead to the development of safe, potent, and novel therapeutic approaches to prevent or treat IBD in addition to other immune disorders.

Filarial infections compromise influenza vaccination efficacy: Lessons from the mouse

Helminth parasites infect more than a quarter of the human population and inflict significant changes to the immunological status of their hosts. Several human studies report impaired responses to vaccinations in helminth-infected individuals. Analysing the impact of helminth infections on the efficacy of influenza vaccinations in the mouse system helps to elucidate the underlying immunological processes. Concurrent infection with the parasitic nematode Litomosoides sigmodontis reduced the quantity and quality of antibody responses to vaccination against seasonal influenza in BALB/c and C57BL/6 mice. This led to impaired vaccination-induced protection against challenge infections with the human pathogenic 2009 pandemic H1N1 influenza A virus in helminth-infected mice. Impaired responses were also observed if vaccinations were performed after immune-driven or drug-induced clearance of a previous helminth infection. Mechanistically, the suppression was associated with a systemic and sustained expansion of IL-10-producing CD4⁺CD49b⁺LAG-3⁺ type 1 regulatory T cells and partially abrogated by in vivo blockade of the IL-10 receptor. In summary, these findings raise the concern that individuals in helminth-endemic areas may not always benefit from vaccinations, even in the absence of an acute and diagnosable helminth infection.

Eliminating Potential Effects of Other Infections During Selection of Nonhuman Primates for COVID-19 Research

The study of nonhuman primates (NHP) can provide significant insights into our understanding numerous infectious agents. The etiological agent of COVID-19, SARS-CoV-2 virus, first emerged in 2019 and has so far been responsible for the deaths of over 4 million people globally. In the frenzied search to understand its pathogenesis and immunology and to find measures for prevention and control of this pandemic disease, NHP, particularly macaques, are the preferred model because they manifest similar clinical signs and immunologic features as humans. However, possible latent, subclinical, and opportunistic infections not previously detected in animals participating in a study may obscure experimental results and confound data interpretations in testing treatments and vaccine studies for COVID-19. Certain pathophysiologic changes that occur with SARS-CoV-2 virus infection are similar to those of simian pathogens. The current review discusses numerous coinfections of COVID-19 with other diseases and describes possible outcomes and mechanisms in COVID-19 studies of NHP that have coinfections. Due to the urgency triggered by the pandemic, screening that is more rigorous than usual is necessary to limit background noise and maximize the reliability of data from NHP COVID-19 studies. Screening for influenza virus, selected respiratory bacteria, and regional endemic pathogens such as vector-borne agents, together with the animal's individual exposure history, should be the main considerations in selecting a NHP for a COVID-19 study. In addition, because NHP are susceptible to the SARS-CoV-2 virus, management and surveillance measures should be established to prevent transmission to healthy animals from infected colony animals and husbandry staff. This review presents compiled data on the use of NHP in COVID-19 studies, emphasizing the need to create the most reliable NHP model for those studies by extensive screening for other pathogens.

The helminth holobiont: a multidimensional host-parasite-microbiota interaction

Gastrointestinal helminths have developed multiple mechanisms by which they manipulate the host microbiome to make a favorable environment for their long-term survival. While the impact of helminth infections on vertebrate host immunity and its gut microbiota is relatively well studied, little is known about the structure and functioning of microbial populations supported by metazoan parasites. Here we argue that an integrated understanding of the helminth-associated microbiome and its role in the host disease pathogenesis may facilitate the discovery of specific microbial and/or genetic patterns critical for parasite biology and subsequently pave the way for the development of alternative control strategies against parasites and parasitic disease.

The helminth derived peptide FhHDM-1 redirects macrophage metabolism towards glutaminolysis to regulate the pro-inflammatory response

We have previously identified an immune modulating peptide, termed FhHDM-1, within the secretions of the liver fluke, Fasciola hepatica, which is sufficiently potent to prevent the progression of type 1 diabetes and multiple sclerosis in murine models of disease. Here, we have determined that the FhHDM-1 peptide regulates inflammation by reprogramming macrophage metabolism. Specifically, FhHDM-1 switched macrophage metabolism to a dependence on oxidative phosphorylation fuelled by fatty acids and supported by the induction of glutaminolysis. The catabolism of glutamine also resulted in an accumulation of alpha ketoglutarate (α-KG). These changes in metabolic activity were associated with a concomitant reduction in glycolytic flux, and the subsequent decrease in TNF and IL-6 production at the protein level. Interestingly, FhHDM-1 treated macrophages did not express the characteristic genes of an M2 phenotype, thereby indicating the specific regulation of inflammation, as opposed to the induction of an anti-inflammatory phenotype per se. Use of an inactive derivative of FhHDM-1, which did not modulate macrophage responses, revealed that the regulation of immune responses was dependent on the ability of FhHDM-1 to modulate lysosomal pH. These results identify a novel functional association between the lysosome and mitochondrial metabolism in macrophages, and further highlight the significant therapeutic potential of FhHDM-1 to prevent inflammation.

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.

Fasciola hepatica primoinfections and reinfections in sheep drive distinct Th1/Th2/Treg immune responses in liver and hepatic lymph node at early and late stages

The expression of proinflammatory (IL-1β, IFN-γ, TNF-α) and regulatory (IL-10, TGF-β, IL-4) cytokines, as well as the transcription factor FoxP3, was quantified in the liver and hepatic lymph node (HLN) of sheep primoinfected and reinfected with Fasciola hepatica at early (4, 8 and 16 days post-infection [dpi]) and late (100 dpi) stages. The liver exerted a Th2 immune response at very early stages after the primoinfection with F. hepatica that induced the downregulation of IFN-γ, followed by a Th1/Th2/Treg response although the late stages were characterised by the expression of Th1/Th2 immune mediators. Contrarily, in reinfected sheep a robust mixed Th1/Th2/Treg immune response was found at very early stages meanwhile at late stages we observed a Th2/Treg immune response overcoming the expression of Th1 immune mediators. However, the HLN displayed a completely different Th1/Th2/Treg expression profile compared to the liver. Primoinfections with F. hepatica in HLN induced a mixed Th1/Th2/Treg environment from early stages, establishing a Th2 immune response at a late stage. However, the reinfected sheep exerted a Th2 immune response at early stages led by the IL-4 expression in opposition to the Th1/Th2/Treg found in the liver, meanwhile at late stages the HLN of reinfected sheep exerted a mixed Th1/Th2/Treg immune response. This is the first work publishing the expression of immune mediators in the liver and HLN from reinfected sheep with F. hepatica. The study of the immune responses exerted by the natural host in the target organs directly implied in the development of F. hepatica are crucial to better understand the immunopathogenesis of the fasciolosis being a key factor to develop effective vaccines.

Urinary neopterin reflects immunological variation associated with age, helminth parasitism, and the microbiome in a wild primate

Neopterin, a product of activated white blood cells, is a marker of nonspecific inflammation that can capture variation in immune investment or disease-related immune activity and can be collected noninvasively in urine. Mounting studies in wildlife point to lifetime patterns in neopterin related to immune development, aging, and certain diseases, but rarely are studies able to assess whether neopterin can capture multiple concurrent dimensions of health and disease in a single system. We assessed the relationship between urinary neopterin stored on filter paper and multiple metrics of health and disease in wild geladas (Theropithecus gelada), primates endemic to the Ethiopian highlands. We tested whether neopterin captures age-related variation in inflammation arising from developing immunity in infancy and chronic inflammation in old age, inflammation related to intramuscular tapeworm infection, helminth-induced anti-inflammatory immunomodulation, and perturbations in the gastrointestinal microbiome. We found that neopterin had a U-shaped relationship with age, no association with larval tapeworm infection, a negative relationship with metrics related to gastrointestinal helminth infection, and a negative relationship with microbial diversity. Together with growing research on neopterin and specific diseases, our results demonstrate that urinary neopterin can be a powerful tool for assessing multiple dimensions of health and disease in wildlife.

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

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

Impact of the mucosal milieu on antibody responses to allergens

Respiratory and digestive mucosal surfaces are continually exposed to common environmental antigens, which include potential allergens. Although innocuous in healthy individuals, allergens cause allergy in predisposed subjects and do so by triggering a pathologic T_H2 cell response that induces IgE class switching and somatic hypermutation in allergen-specific B cells. The ensuing affinity maturation and plasma cell differentiation lead to the abnormal release of high-affinity IgE that binds to powerful FcεRI receptors on basophils and mast cells. When cross-linked by allergen, FcεRI-bound IgE instigates the release of prestored and de novo-induced proinflammatory mediators. Aside from causing type I hypersensitivity reactions underlying allergy, IgE affords protection against nematodes or venoms from insects and snakes, which raises questions as to the fundamental differences between protective and pathogenic IgE responses. In this review, we discuss the impact of the mucosal environment, including the epithelial and mucus barriers, on the induction of protective IgE responses against environmental antigens. We further discuss how perturbations of these barriers may contribute to the induction of pathogenic IgE production.

Investigating the Potential Effects of COVID-19 Pandemic on Intestinal Coccidian Infections

New infectious agents pose a global threat to the healthcare system, and studies are conducted to estimate their health and epidemiological outcomes in the long run. The SARS-CoV-2 virus, which has caused the COVID-19 disease, was formerly assumed to be a respiratory virus; however, it can have serious systemic effects, affecting organs such as the gastrointestinal tract (GIT). Viral RNA was reported in the stool in a subset of patients, indicating another mode of transmission and diagnosis. In COVID-19, prolonged GIT symptoms, especially diarrhea, were associated with reduced diversity and richness of gut microbiota, immunological dysregulation, and delayed viral clearance. Intestinal coccidian parasites are intracellular protozoa that are most typically transmitted to humans by oocysts found in fecally contaminated food and water. Their epidemiological relevance is coupled to opportunistic infections, which cause high morbidity and mortality among immunocompromised individuals. Among immunocompetent people, intestinal coccidia is also involved in acute diarrhea, which is usually self-limiting. Evaluating the available evidence provided an opportunity to carefully consider that; the COVID-19 virus and coccidian protozoan parasites: namely, Cryptosporidium spp., Cyclospora cayetanensis, and Isospora belli, could mutually influence each other from the microbiological, clinical, diagnostic, and elimination aspects. We further systemically highlighted the possible shared pathogenesis mechanisms, transmission routes, clinical manifestations, parasite-driven immune regulation, and intestinal microbiota alteration. Finally, we showed how this might impact developing and developed countries prevention and vaccination strategies. To the best of our knowledge, there is no review that has discussed the reciprocal effect between coccidian parasites and COVID-19 coinfection.

Fasciola hepatica Fatty Acid Binding Protein 1 Modulates T cell Polarization by Promoting Dendritic Cell Thrombospondin-1 Secretion Without Affecting Metabolic Homeostasis in Obese Mice

Background

The parasitic trematode Fasciola hepatica evades host immune defenses through secretion of various immunomodulatory molecules. Fatty Acid Binding Proteins (fhFABPs) are among the main excreted/secreted proteins and have been shown to display anti-inflammatory properties. However, little is currently known regarding their impact on dendritic cells (DCs) and their subsequent capacity to prime specific CD4+ T cell subsets.

Methodology/Principal Findings

The immunomodulatory effects of both native F. hepatica extracts and recombinant fhFABPs were assessed on monocyte-derived human DCs (moDCs) and the underlying mechanism was next investigated using various approaches, including DC-allogenic T cell co-culture and DC phenotyping through transcriptomic, proteomic and FACS analyses. We mainly showed that fhFABP1 induced a tolerogenic-like phenotype in LPS-stimulated moDCs characterized by a dose-dependent increase in the cell-surface tolerogenic marker CD103 and IL-10 secretion, while DC co-stimulatory markers were not affected. A significant decrease in secretion of the pro-inflammatory cytokines IL-12p70 and IL-6 was also observed. In addition, these effects were associated with an increase in both Th2-on-Th1 ratio and IL-10 secretion by CD4+ T cells following DC-T cell co-culture. RNA sequencing and targeted proteomic analyses identified thrombospondin-1 (TSP-1) as a non-canonical factor highly expressed and secreted by fhFABP1-primed moDCs. The effect of fhFABP1 on T cell skewing was abolished when using a TSP-1 blocking antibody during DC-T cell co-culture. Immunomodulation by helminth molecules has been linked to improved metabolic homeostasis during obesity. Although fhFABP1 injection in high-fat diet-fed obese mice induced a potent Th2 immune response in adipose tissue, it did not improved insulin sensitivity or glucose homeostasis.

Conclusions/Significance

We show that fhFABP1 modulates T cell polarization, notably by promoting DC TSP-1 secretion in vitro, without affecting metabolic homeostasis in a mouse model of type 2 diabetes.

Detangling the Crosstalk Between Ascaris, Trichuris and Gut Microbiota: What´s Next?

Helminth infections remain a global public health issue, particularly in low- and middle-income countries, where roundworms from theTrichuris and Ascaris genera are most prevalent. These geohelminths not only impact human health but most importantly also affect animal well-being, in particular the swine industry. Host-helminth parasite interactions are complex and at the same time essential to understand the biology, dynamics and pathophysiology of these infections. Within these interactions, the immunomodulatory capacity of these helminths in the host has been extensively studied. Moreover, in recent years a growing interest on how helminths interact with the intestinal microbiota of the host has sparked, highlighting how this relationship plays an essential role in the establishment of initial infection, survival and persistence of the parasite, as well as in the development of chronic infections. Identifying the changes generated by these helminths on the composition and structure of the host intestinal microbiota constitutes a field of great scientific interest, since this can provide essential and actionable information for designing effective control and therapeutic strategies. Helminths like Trichuris and Ascaris are a focus of special importance due to their high prevalence, higher reinfection rates, resistance to anthelmintic therapy and unavailability of vaccines. Therefore, characterizing interactions between these helminths and the host intestinal microbiota represents an important approach to better understand the nature of this dynamic interface and explore novel therapeutic alternatives based on management of host microbiota. Given the extraordinary impact this may have from a biological, clinical, and epidemiological public health standpoint, this review aims to provide a comprehensive overview of current knowledge and future perspectives examining the parasite-microbiota interplay and its impact on host immunity.

The relevance of studying insect-nematode interactions for human disease

Vertebrate-parasitic nematodes cause debilitating, chronic infections in millions of people worldwide. The burden of these so-called 'neglected tropical diseases' is often carried by poorer socioeconomic communities in part because research on parasitic nematodes and their vertebrate hosts is challenging and costly. However, complex biological and pathological processes can be modeled in simpler organisms. Here, we consider how insight into the interactions between entomopathogenic nematodes (EPN), their insect hosts and bacterial symbionts may reveal novel treatment targets for parasitic nematode infections. We argue that a combination of approaches that target nematodes, as well as the interaction of pathogens with insect vectors and bacterial symbionts, offer potentially effective, but underexplored opportunities.

Convergent evolution of a parasite-encoded complement control protein-scaffold to mimic binding of mammalian TGF-β to its receptors, TβRI and TβRII

The mouse intestinal helminth Heligmosomoides polygyrus modulates host immune responses by secreting a transforming growth factor (TGF)-β mimic (TGM), to expand the population of Foxp3⁺ T_regs. TGM comprises five complement control protein (CCP)-like domains, designated D1-D5. Though lacking homology to TGF-β, TGM binds directly to the TGF-β receptors TβRI and TβRII and stimulates the differentiation of naïve T-cells into T_regs. However, the molecular determinants of binding are unclear. Here, we used surface plasmon resonance, isothermal calorimetry, NMR spectroscopy, and mutagenesis to investigate how TGM binds the TGF-β receptors. We demonstrate that binding is modular, with D1-D2 binding to TβRI and D3 binding to TβRII. D1-D2 and D3 were further shown to compete with TGF-β(TβRII)₂ and TGF-β for binding to TβRI and TβRII, respectively. The solution structure of TGM-D3 revealed that TGM adopts a CCP-like fold but is also modified to allow the C-terminal strand to diverge, leading to an expansion of the domain and opening potential interaction surfaces. TGM-D3 also incorporates a long structurally ordered hypervariable loop, adding further potential interaction sites. Through NMR shift perturbations and binding studies of TGM-D3 and TβRII variants, TGM-D3 was shown to occupy the same site of TβRII as bound by TGF-β using both a novel interaction surface and the hypervariable loop. These results, together with the identification of other secreted CCP-like proteins with immunomodulatory activity in H. polygyrus, suggest that TGM is part of a larger family of evolutionarily plastic parasite effector molecules that mediate novel interactions with their host.

Localization and RNA Interference-Driven Inhibition of a Brugia malayi-Encoded Interleukin-5 Receptor Binding Protein

A molecule we termed Brugia malayi IL-5 receptor (IL-5R) binding protein (BmIL5Rbp; also known as Bm8757) was identified from B. malayi filarial worms and found to inhibit human interleukin-5 (IL-5) binding to its human receptor competitively. After the expression and purification of a recombinant BmIL5Rbp and generation of BmIL5Rbp-specific rabbit antibody, we localized the molecule on B. malayi worms through immunohistochemistry and immunoelectron microscopy. RNA interference (RNAi) was used to inhibit BmIL5Rbp mRNA and protein production. BmIL5Rbp was shown to localize to the cuticle of Brugia malayi and to be released in its excretory/secretory products. RNAi inhibited BmIL5Rbp mRNA production by 33%, reduced the surface protein expression by ~50%, and suppressed the release of BmIL5Rbp in the excretory/secretory products. RNAi has been used successfully to knock down the mRNA and protein expression of BmIL5Rbp in the early larval stages of B. malayi and provided a proof of principle for the local inhibition of the human IL-5R. These findings provide evidence that a parasite-encoded IL-5R antagonist may locally inhibit a vital host innate immune activation of IL-5 on eosinophils.

The interplay of helminthic neuropeptides and proteases in parasite survival and host immunomodulation

Neuropeptides comprise a diverse and broad group of neurotransmitters in vertebrates and invertebrates, with critical roles in neuronal signal transduction. While their role in controlling learning and memory in the brains of mammals is known, their extra-synaptic function in infection and inflammation with effects on distinct tissues and immune cells is increasingly recognized. Helminth infections especially of the central nervous system (CNS), such as neurocysticercosis, induce neuropeptide production by both host and helminth, but their role in host-parasite interplay or host inflammatory response is unclear. Here, we review the neurobiology of helminths, and discuss recent studies on neuropeptide synthesis and function in the helminth as well as the host CNS and immune system. Neuropeptides are summarized according to structure and function, and we discuss the complex enzyme processing for mature neuropeptides, focusing on helminth enzymes as potential targets for novel anthelminthics. We next describe known immunomodulatory effects of mammalian neuropeptides discovered from mouse infection models and draw functional parallels with helminth neuropeptides. Last, we discuss the anti-microbial properties of neuropeptides, and how they may be involved in host-microbiota changes in helminth infection. Overall, a better understanding of the biology of helminth neuropeptides, and whether they affect infection outcomes could provide diagnostic and therapeutic opportunities for helminth infections.

Helminth and Host Crosstalk: New Insight Into Treatment of Obesity and Its Associated Metabolic Syndromes

Obesity and its associated Metabolic Syndromes (Mets) represent a global epidemic health problem. Metabolic inflammation, lipid accumulation and insulin resistance contribute to the progression of these diseases, thereby becoming targets for drug development. Epidemiological data have showed that the rate of helminth infection negatively correlates with the incidence of obesity and Mets. Correspondingly, numerous animal experiments and a few of clinic trials in human demonstrate that helminth infection or its derived molecules can mitigate obesity and Mets via induction of macrophage M2 polarization, inhibition of adipogenesis, promotion of fat browning, and improvement of glucose tolerance, insulin resistance and metabolic inflammation. Interestingly, sporadic studies also uncover that several helminth infections can reshape gut microbiota of hosts, which is intimately implicated in the pathogenesis of obesity and Mets. Overall, these findings indicate that the crosstalk between helminth and hosts may be a novel direction for obesity and Mets therapy. The present article reviews the molecular mechanism of how helminth masters immunity and metabolism in obesity.

Helminth-virus interactions: determinants of coinfection outcomes

Viral infections are often studied in model mammalian organisms under specific pathogen-free conditions. However, in nature, coinfections are common, and infection with one organism can alter host susceptibility to infection with another. Helminth parasites share a long coevolutionary history with mammalian hosts and have shaped host physiology, metabolism, immunity, and the composition of the microbiome. Published studies suggest that helminth infection can either be beneficial or detrimental during viral infection. Here, we discuss coinfection studies in mouse models and use them to define key determinants that impact outcomes, including the type of antiviral immunity, the tissue tropism of both the helminth and the virus, and the timing of viral infection in relation to the helminth lifecycle. We also explore the current mechanistic understanding of how helminth-virus coinfection impacts host immunity and viral pathogenesis. While much attention has been placed on the impact of the gut bacterial microbiome on immunity to infection, we suggest that enteric helminths, as a part of the eukaryotic macrobiome, also represent an important modulator of disease pathogenesis and severity following virus infection.

Helminth infection is associated with dampened cytokine responses to viral and bacterial stimulations in Tsimane forager-horticulturalists

Background

Soil-transmitted helminths (STHs) and humans share long co-evolutionary histories over which STHs have evolved strategies to permit their persistence by downregulating host immunity. Understanding the interactions between STHs and other pathogens can inform our understanding of human evolution and contemporary disease patterns.

Methodology

We worked with Tsimane forager-horticulturalists in the Bolivian Amazon, where STHs are prevalent. We tested whether STHs and eosinophil levels—likely indicative of infection in this population—are associated with dampened immune responses to in vitro stimulation with H1N1 and lipopolysaccharide (LPS) antigens. Whole blood samples (n = 179) were treated with H1N1 vaccine and LPS and assayed for 13 cytokines (INF-γ, IL-1β, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12p70, IL-13, GM-CSF and TNF-ɑ). We evaluated how STHs and eosinophil levels affected cytokine responses and T helper (Th) 1 and Th2-cytokine suite responses to stimulation.

Results

Infection with Ascaris lumbricoides was significantly (P ≤ 0.05) associated with lower response of some cytokines to H1N1 and LPS in women. Eosinophils were significantly negatively associated with some cytokine responses to H1N1 and LPS, with the strongest effects in women, and associated with a reduced Th1- and Th2-cytokine response to H1N1 and LPS in women and men.

Conclusions and implications

Consistent with the ‘old friends’ and hygiene hypotheses, we find that STHs were associated with dampened cytokine responses to certain viral and bacterial antigens. This suggests that STH infections may play an essential role in immune response regulation and that the lack of STH immune priming in industrialized populations may increase the risk of over-reactive immunity.

Lay Summary: Indicators of helminth infection were associated with dampened cytokine immune responses to in vitro stimulation with viral and bacterial antigens in Tsimane forager-horticulturalists in the Bolivian Amazon, consistent with the ‘old friends’ and hygiene hypotheses.

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.

The effect of regulatory T cells in Schistosoma-mediated protection against type 2 diabetes

In western societies, the prevalence of type 2 diabetes (T2D) is related to the hygiene hypothesis, which implies that reduced exposure to infectious factors results in a loss of the immune stimulation necessary to form the immune system during development. In fact, it has been reported that parasites, such as Schistosoma, can improve or prevent the development of T2D, which may be related to the activity of immune cells, including regulatory T cells (Tregs). Hence, Schistosoma, Tregs, and T2D share a close relationship. Schistosoma infection and the molecules released can lead to an increase in Tregs, which play an important role in the suppression of T2D. In this review, we provide an overview of the role of Tregs in the response to Schistosoma infection and the protective mechanism of Schistosoma-related molecular products against T2D.

Helminth extracellular vesicles: Interactions with the host immune system

As long-lived parasites, helminths depend upon immunomodulation of their hosts for survival. The release of excretory-secretory (ES) products, including proteins, lipids and RNAs is how successful host manipulation is achieved. It has recently been discovered that the ES products of helminths contain extracellular vesicles (EVs), with every species investigated found to secrete these lipid-bound structures. EVs are perfect for packaging and delivering immune modulators to target cell types. This review outlines the research carried out on helminth EVs and their constituents thus far, as well as their interaction with components of the mammalian immune system. We discuss how targeting EVs will aid treatment of helminth infection and consider how EVs and their immunomodulatory cargo could be used as therapeutics as we progress through this exciting era.