The Differentiation of CD4(+) T-Helper Cell Subsets in the Context of Helminth Parasite Infection

Hepatic transcriptomic analysis reveals differential regulation of metabolic and immune pathways in three strains of chickens with distinct growth rates exposed to mixed parasite infections

During parasite infections, the liver may prioritise immune-related pathways over its metabolic functions. Intestinal infections caused by Ascaridia galli and Heterakis gallinarum impair feed intake, nutrient absorption, and weight gain. Histomonas meleagridis, vectored by H. gallinarum, can also damage liver tissues, potentially impairing liver functions. This study examined the hepatic gene expression in three strains of chickens: Ross-308 (R), Lohmann Brown Plus (LB), and Lohmann Dual (LD), 2 weeks after an experimental infection (n = 18) with both A. galli and H. gallinarum or kept as uninfected control (n = 12). Furthermore, H. gallinarum infection led to a co-infection with H. meleagridis. The mixed infections reduced feed intake and the average daily weight gain (P < 0.001). The infections also increased the plasma concentrations of alpha (1)-acid glycoprotein and the antibody titre against H. meleagridis (P = 0.049), with no strain differences (P > 0.05). For host molecular response, 1887 genes were differentially expressed in LD, while 275 and 25 genes were differentially expressed in R and LB, respectively. The up-regulated genes in R and LD were mostly related to inflammatory and adaptive immune responses, while down-regulated genes in LD were involved in metabolic pathways, including gluconeogenesis. Despite performance differences among the strains, worm burdens were similar, but hepatic molecular responses differed significantly. Moreover, there was an indication of a shift in hepatic functions towards immune-related pathways. We, therefore, conclude that the liver shifts its functions from metabolic to immune-related activities in chickens when challenged with mixed parasite species.

Inflammatory and immunopathological differences in brains of permissive and non-permissive hosts with Angiostrongylus cantonensis infection can be identified using 18F/FDG/PET-imaging

BACKGROUND

Angiostrongylus cantonensis is a parasite that mainly infects the heart and pulmonary arteries of rats and causes human eosinophilic meningitis or meningoencephalitis in certain geographical areas. Current diagnostic methods include detection of the parasite in cerebrospinal fluid (CSF) and eosinophilic immune examination after lumbar puncture, which may be risky and produce false-positive results. 18F- Fluorodeoxyglucose (FDG), a Positron emission tomography (PET) tracer, has been used to assess different pathological or inflammatory changes in the brains of patients. In this study, we hypothesized that A. cantonensis infection-induced inflammatory and immunomodulatory factors of eosinophils result in localized pathological changes in the brains of non-permissive hosts, which could be analyzed using in vivo 18F-FDG PET imaging.

METHODOLOGY/FINDINGS

Non-permissive host ICR mice and permissive host SD rats were infected with A. cantonensis, and the effects of the resulting inflammation on 18F-FDG uptake were characterized using PET imaging. We also quantitatively measured the distributed uptake values of different brain regions to build an evaluated imaging model of localized neuropathological damage caused by eosinophilic inflammation. Our results showed that the uptake of 18F-FDG increased in the cerebellum, brainstem, and limbic system of mice at three weeks post-infection, whereas the uptake in the rat brain was not significant. Immunohistochemical staining and western blotting revealed that Iba-1, a microglia-specific marker, significantly increased in the hippocampus and its surrounding area in mice after three weeks of infection, and then became pronounced after four weeks of infection; while YM-1, an eosinophilic chemotactic factor, in the hippocampus and midbrain, increased significantly from two weeks post-infection, sharply escalated after three weeks of infection, and peaked after four weeks of infection. Cytometric bead array (CBA) analysis revealed that the expression of TNF in the serum of mice increased concomitantly with the prolongation of infection duration. Furthermore, IFN-γ and IL-4 in rat serum were significantly higher than in mouse serum at two weeks post-infection, indicating significantly different immune responses in the brains of rats and mice. We suggest that 18F-FDG uptake in the host brain may be attributed to the accumulation of large numbers of immune cells, especially the metabolic burst of activated eosinophils, which are attracted to and induced by activated microglia in the brain.

CONCLUSIONS

An in vivo 18F-FDG/PET imaging model can be used to evaluate live neuroinflammatory pathological changes in the brains of A. cantonensis-infected mice and rats.

Differentiation and Regulation of Bovine Th2 Cells In Vitro

Bovine Th2 cells have usually been characterized by IL4 mRNA expression, but it is unclear whether their IL4 protein expression corresponds to transcription. We found that grass-fed healthy beef cattle, which had been regularly exposed to parasites on the grass, had a low frequency of IL4+ Th2 cells during flow cytometry, similar to animals grown in feedlots. To assess the distribution of IL4+ CD4+ T cells across tissues, samples from the blood, spleen, abomasal (draining), and inguinal lymph nodes were examined, which revealed limited IL4 protein detection in the CD4+ T cells across the examined tissues. To determine if bovine CD4+ T cells may develop into Th2 cells, naïve cells were stimulated with anti-bovine CD3 under a Th2 differentiation kit in vitro. The cells produced primarily IFNγ proteins, with only a small fraction (<10%) co-expressing IL4 proteins. Quantitative PCR confirmed elevated IFNγ transcription but no significant change in IL4 transcription. Surprisingly, GATA3, the master regulator of IL4, was highest in naïve CD4+ T cells but was considerably reduced following differentiation. To determine if the differentiated cells were true Th2 cells, an unbiased proteomic assay was carried out. The assay identified 4212 proteins, 422 of which were differently expressed compared to those in naïve cells. Based on these differential proteins, Th2-related upstream components were predicted, including CD3, CD28, IL4, and IL33, demonstrating typical Th2 differentiation. To boost IL4 expression, T cell receptor (TCR) stimulation strength was reduced by lowering anti-CD3 concentrations. Consequently, weak TCR stimulation essentially abolished Th2 expansion and survival. In addition, extra recombinant bovine IL4 (rbIL4) was added during Th2 differentiation, but, despite enhanced expansion, the IL4 level remained unaltered. These findings suggest that, while bovine CD4+ T cells can respond to Th2 differentiation stimuli, the bovine IL4 pathway is not regulated in the same way as in mice and humans. Furthermore, Ostertagia ostertagi (OO) extract, a gastrointestinal nematode in cattle, inhibited signaling via CD3, CD28, IL4, and TLRs/MYD88, indicating that external pathogens can influence bovine Th2 differentiation. In conclusion, though bovine CD4+ T cells can respond to IL4-driven differentiation, IL4 expression is not a defining feature of differentiated bovine Th2 cells.

A Comparative Analysis of the Protein Cargo of Extracellular Vesicles from Helminth Parasites

Helminth parasites cause debilitating-sometimes fatal-diseases in humans and animals. Despite their impact on global health, mechanisms underlying host-parasite interactions are still poorly understood. One such mechanism involves the exchange of extracellular vesicles (EVs), which are membrane-enclosed subcellular nanoparticles. To date, EV secretion has been studied in helminth parasites, including EV protein content. However, information is highly heterogeneous, since it was generated in multiple species, using varied protocols for EV isolation and data analysis. Here, we compared the protein cargo of helminth EVs to identify common markers for each taxon. For this, we integrated published proteomic data and performed a comparative analysis through an orthology approach. Overall, only three proteins were common in the EVs of the seven analyzed species. Additionally, varied repertoires of proteins with moonlighting activity, vaccine antigens, canonical and non-canonical proteins related to EV biogenesis, taxon-specific proteins of unknown function and RNA-binding proteins were observed in platyhelminth and nematode EVs. Despite the lack of consensus on EV isolation protocols and protein annotation, several proteins were shown to be consistently detected in EV preparations from organisms at different taxa levels, providing a starting point for a selective biochemical characterization.

Colonization with ubiquitous protist Blastocystis ST1 ameliorates DSS-induced colitis and promotes beneficial microbiota and immune outcomes

Blastocystis is a species complex that exhibits extensive genetic diversity, evidenced by its classification into several genetically distinct subtypes (ST). Although several studies have shown the relationships between a specific subtype and gut microbiota, there is no study to show the effect of the ubiquitous Blastocystis ST1 on the gut microbiota and host health. Here, we show that Blastocystis ST1 colonization increased the proportion of beneficial bacteria Alloprevotella and Akkermansia, and induced Th2 and Treg cell responses in normal healthy mice. ST1-colonized mice showed decreases in the severity of DSS-induced colitis when compared to non-colonized mice. Furthermore, mice transplanted with ST1-altered gut microbiota were refractory to dextran sulfate sodium (DSS)-induced colitis via induction of Treg cells and elevated short-chain fat acid (SCFA) production. Our results suggest that colonization with Blastocystis ST1, one of the most common subtypes in humans, exerts beneficial effects on host health through modulating the gut microbiota and adaptive immune responses.

IL-10 regulates Th17 response to inhibit hepatobiliary injury caused by Clonorchis sinensis infection in C57BL/6J mice

Clonorchiasis caused by Clonorchis sinensis is a mainly foodborne parasitic disease. It can lead to hepatobiliary duct inflammation, fibrosis, obstructive jaundice, liver cirrhosis, and even cholangiocarcinoma. Interleukin (IL)-10 is an immune-regulatory cytokine which plays an immunosuppressive role during infection. Our previous study found that IL-10 was increased in mice with C. sinensis infection. However, the role and mechanism of IL-10 playing in hepatobiliary injury induced by C. sinensis infection remain unknown. Herein, Il10^+/+ mice and Il10^+/- C57BL/6J mice were infected with C. sinensis. It was found that IL-10 deficiency aggravated biliary hyperplasia and exacerbated periductal fibrosis induced by C. sinensis infection. Moreover, IL-10 deficiency increased CD4⁺T cells and CD8⁺T cells but not macrophages in the liver of mice with infection. There were no apparent differences in Th1 and Treg cells between Il10^+/+ and Il10^+/- mice infected with C. sinensis. However, the proportion of Th17 cells in CD4⁺T cells in Il10^+/- infected mice was significantly higher than that in Il10^+/+ infected mice. IL-10 deficiency also enhanced the increase of Th17 cells induced by ESPs stimulation in vitro. Taken together, our results suggest that IL-10 plays a protective role in hepatobiliary injury in C57BL/6J mice induced by C. sinensis infection via inhibiting Th17 cells, which could deepen our understanding of the immunopathology of clonorchiasis.

Schnurri 3 promotes Th2 cytokine production during the late phase of T-cell antigen stimulation

Th1 and Th2 polarization is determined by the coordination of numerous factors including the affinity and strength of the antigen-receptor interaction, predominant cytokine environment, and costimulatory molecules present. Here, we show that Schnurri (SHN) proteins have distinct roles in Th1 and Th2 polarization. SHN2 was previously found to block the induction of GATA3 and Th2 differentiation. We found that, in contrast to SHN2, SHN3 is critical for IL-4 production and Th2 polarization. Strength of stimulation controls SHN2 and SHN3 expression patterns, where higher doses of antigen receptor stimulation promoted SHN3 expression and IL-4 production, along with repression of SHN2 expression. SHN3-deficient T cells showed a substantial defect in IL-4 production and expression of AP-1 components, particularly c-Jun and Jun B. This loss of early IL-4 production led to reduced GATA3 expression and impaired Th2 differentiation. Together, these findings uncover SHN3 as a novel, critical regulator of Th2 development.

Nitric oxide contributes to liver inflammation and parasitic burden control in Ascaris suum infection

BACKGROUND

Human ascariasis is one of the most prevalent neglected tropical diseases worldwide. The immune response during human ascariasis is characterized by Th2 polarization and a mixed Th2/Th17 response during the pathogenesis of experimental larval ascariasis. Cytokines and other pro-inflammatory mediators, such as nitric oxide (NO), are involved in helminthic infections. However, the role of NO in ascariasis remains unclear.

OBJECTIVES

Given the importance of NO in inflammation, we aimed to determine the immunological and histopathological alterations in the livers of C57BL/6 iNOS^-/- mice during A. suum infection.

METHODS

In this study, parasitic load was evaluated in the livers of wild type C57BL/6 and C57BL/6 iNOS^-/- mice infected with A. suum. Histopathological and morphometric analyses and analysis of serum cytokines via Cytometric Bead Array were performed, and the activity of eosinophil peroxidase and myeloperoxidase of neutrophils in the tissues were determined.

RESULTS

The results showed that NO is important for controlling parasitic load during infection by A. suum. C57BL/6iNOS^-/- mice showed reduced inflammatory processes and less tissue damage during liver larval migration of A. suum, which is associated with a reduction in serum levels of pro-inflammatory cytokines.

CONCLUSIONS

We demonstrated that NO is a crucial inflammatory molecule during Ascaris sp. infection and controls the establishment of the parasite and the development of the host immune response in the liver.

Use of Clinical Isolates to Establish Criteria for a Mouse Model of Latent Cryptococcus neoformans Infection

The mechanisms of latency in the context of C. neoformans infection remain poorly understood. Two reasons for this gap in knowledge are: 1) the lack of standardized criteria for defining latent cryptococcosis in animal models and 2) limited genetic and immunological tools available for studying host parameters against C. neoformans in non-murine models of persistent infection. In this study, we defined criteria required for latency in C. neoformans infection models and used these criteria to develop a murine model of persistent C. neoformans infection using clinical isolates. We analyzed infections with two clinical C. neoformans strains, UgCl223 and UgCl552, isolated from advanced HIV patients with cryptococcal meningitis. Our data show that the majority of C57BL/6 mice infected with the clinical C. neoformans isolates had persistent, stable infections with low fungal burden, survived beyond 90 days-post infection, exhibited weight gain, had no clinical signs of disease, and had yeast cells contained within pulmonary granulomas with no generalized alveolar inflammation. Infected mice exhibited stable relative frequencies of pulmonary immune cells during the course of the infection. Upon CD4+ T-cell depletion, the CD4DTR mice had significantly increased lung and brain fungal burden that resulted in lethal infection, indicating that CD4+ T-cells are important for control of the pulmonary infection and to prevent dissemination. Cells expressing the Tbet transcription factor were the predominant activated CD4 T-cell subset in the lungs during the latent infection. These Tbet-expressing T-cells had decreased IFNγ production, which may have implications in the capacity of the cells to orchestrate the pulmonary immune response. Altogether, these results indicate that clinical C. neoformans isolates can establish a persistent controlled infection that meets most criteria for latency; highlighting the utility of this new mouse model system for studies of host immune responses that control C. neoformans infections.

T helper type (Th1/Th2) responses to SARS-CoV-2 and influenza A (H1N1) virus: From cytokines produced to immune responses

Cytokines produced by T helper cells (Th cells) have essential roles in the body's defense against viruses. Type 1 T helper (Th1) cells are essential for the host defense toward intracellular pathogens while T helper type 2 (Th2) cells are considered to be critical for the helminthic parasites' elimination swine-origin influenza A (H1N1) virus, a disease led to an epidemic in 2009 and rapidly spread globally via human-to-human transmission. Coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has caused a global pandemic in 2020 and is a serious threat to the public health. Pulmonary immunopathology is the leading cause of death during influenza and SARS-CoV-2 epidemics and pandemics. Influenza and SARS-CoV-2 cause high levels of cytokines in the lung. Both inadequate levels and high levels of specific cytokines can have side effects. In this literature review article, we want to compare the Th1 and Th2 cells responses in SARS-CoV-2 and H1N1.

Remote regulation of type 2 immunity by intestinal parasites

The intestinal tract is the target organ of most parasitic infections, including those by helminths and protozoa. These parasites elicit prototypical type 2 immune activation in the host's immune system with striking impact on the local tissue microenvironment. Despite local containment of these parasites within the intestinal tract, parasitic infections also mediate immune adaptation in peripheral organs. In this review, we summarize the current knowledge on how such gut-tissue axes influence important immune-mediated resistance and disease tolerance in the context of coinfections, and elaborate on the implications of parasite-regulated gut-lung and gut-brain axes on the development and severity of airway inflammation and central nervous system diseases.

Transgenic expression of a T cell epitope in Strongyloides ratti reveals that helminth-specific CD4+ T cells constitute both Th2 and Treg populations

Helminths are distinct from microbial pathogens in both size and complexity, and are the likely evolutionary driving force for type 2 immunity. CD4+ helper T cells can both coordinate worm clearance and prevent immunopathology, but issues of T cell antigen specificity in the context of helminth-induced Th2 and T regulatory cell (Treg) responses have not been addressed. Herein, we generated a novel transgenic line of the gastrointestinal nematode Strongyloides ratti expressing the immunodominant CD4+ T cell epitope 2W1S as a fusion protein with green fluorescent protein (GFP) and FLAG peptide in order to track and study helminth-specific CD4+ T cells. C57BL/6 mice infected with this stable transgenic line (termed Hulk) underwent a dose-dependent expansion of activated CD44hiCD11ahi 2W1S-specific CD4+ T cells, preferentially in the lung parenchyma. Transcriptional profiling of 2W1S-specific CD4+ T cells isolated from mice infected with either Hulk or the enteric bacterial pathogen Salmonella expressing 2W1S revealed that pathogen context exerted a dominant influence over CD4+ T cell phenotype. Interestingly, Hulk-elicited 2W1S-specific CD4+ T cells exhibited both Th2 and Treg phenotypes and expressed high levels of the EGFR ligand amphiregulin, which differed greatly from the phenotype of 2W1S-specific CD4+ T cells elicited by 2W1S-expressing Salmonella. While immunization with 2W1S peptide did not enhance clearance of Hulk infection, immunization did increase total amphiregulin production as well as the number of amphiregulin-expressing CD3+ cells in the lung following Hulk infection. Altogether, this new model system elucidates effector as well as immunosuppressive and wound reparative roles of helminth-specific CD4+ T cells. This report establishes a new resource for studying the nature and function of helminth-specific T cells.

Single cell analysis of host response to helminth infection reveals the clonal breadth, heterogeneity, and tissue-specific programming of the responding CD4+ T cell repertoire

The CD4⁺ T cell response is critical to host protection against helminth infection. How this response varies across different hosts and tissues remains an important gap in our understanding. Using IL-4-reporter mice to identify responding CD4⁺ T cells to Nippostrongylus brasiliensis infection, T cell receptor sequencing paired with novel clustering algorithms revealed a broadly reactive and clonally diverse CD4⁺ T cell response. While the most prevalent clones and clonotypes exhibited some tissue selectivity, most were observed to reside in both the lung and lung-draining lymph nodes. Antigen-reactivity of the broader repertoires was predicted to be shared across both tissues and individual mice. Transcriptome, trajectory, and chromatin accessibility analysis of lung and lymph-node repertoires revealed three unique but related populations of responding IL-4⁺ CD4⁺ T cells consistent with T follicular helper, T helper 2, and a transitional population sharing similarity with both populations. The shared antigen reactivity of lymph node and lung repertoires combined with the adoption of tissue-specific gene programs allows for the pairing of cellular and humoral responses critical to the orchestration of anti-helminth immunity.

Using various “omic” approaches, the CD4⁺ T cell receptor (TCR) repertoire was explored after primary helminth infection. Infection generated a broadly reactive and clonally diverse CD4⁺ T cell response with the most prevalent clonotypes and predicted antigen specificities residing in both the lung and lung-draining lymph nodes. Tissue-specific programming of responding CD4⁺ T cells directed the establishment of committed Tfh and Th2 cells, both critical for driving distinct hallmarks of type-2 inflammation. These datasets help to explore the diverse yet tissue-specific nature of anti-helminth immunity.

The dynamics of select cellular responses and cytokine expression profiles in mice infected with juvenile Clonorchis sinensis

Clonorchiasis is a zoonotic disease that can result in chronic infection in humans. The causative agent, Clonorchis sinensis (C. sinensis), is believed to primarily induce a Th2 immune response in infected mice. However, few studies have profiled host immune responses to C. sinensis infection during the juvenile phase. In the present study, the dynamics of select cellular responses and cytokine expression profiles during juvenile C. sinensis infection were investigated. The flow cytometry results showed that the CD4+ T cells percentage was significantly decreased between 12 days post-infection (dpi) and 24 dpi in the peripheral blood, and the CD8+ T cells percentage was significantly elevated after 3 dpi. The ratio of CD4+/CD8+ T cells was also significantly decreased after 3 dpi. Furthermore, we observed that the proportion of CD14+ monocyte-macrophages in the peripheral blood was significantly increased between 1 dpi and 12 dpi and peaked at 6 dpi. The percentage of classically activated macrophages (M1) and alternatively activated macrophages (M2) in the liver was significantly increased between 18 dpi and 30 dpi. qRT-PCR results showed that the expression levels of iNOS in the liver were significantly elevated after 3 dpi, and Arg-1 expression was significantly increased beginning at 12 dpi. ELISA results showed that the serum levels of the Th1 cytokines IFN-γ and IL-2 peaked at 6 dpi and decreased thereafter. Furthermore, the Th2 cytokines IL-4 and IL-13 began to be expressed and peaked at 24 dpi and 30 dpi, respectively. In addition, the levels of the Treg cytokines IL-10 and TGF-β₁ were significantly increased beginning at 6 dpi until 30 dpi. In the liver homogenate, the expression of IFN-γ, IL-2, and IL-4 mainly occurred before 6 dpi. IL-13 expression was significantly increased at 30 dpi. IL-10 and TGF-β₁ levels were significantly increased at 12 dpi and 24 dpi, and expression peaked at 24 dpi and 30 dpi, respectively. This study provides a fundamental characterization for the future analysis of host-parasite interactions and immune responses in hosts infected with juvenile C. sinensis.

Schistosome infection promotes osteoclast-mediated bone loss

Infection with schistosome results in immunological changes that might influence the skeletal system by inducing immunological states affecting bone metabolism. We investigated the relationships between chronic schistosome infection and bone metabolism by using a mouse model of chronic schistosomiasis, affecting millions of humans worldwide. Results showed that schistosome infection resulted in aberrant osteoclast-mediated bone loss, which was accompanied with an increased level of receptor activator of nuclear factor-κB (NF-κB) Ligand (RANKL) and decreased level of osteoprotegerin (OPG). The blockade of RANKL by the anti-RANKL antibody could prevent bone loss in the context of schistosome infection. Meanwhile, both B cells and CD4⁺ T cells, particularly follicular helper T (Tfh) cell subset, were the important cellular sources of RANKL during schistosome infection. These results highlight the risk of bone loss in schistosome-infected patients and the potential benefit of coupling bone therapy with anti-schistosome treatment.

Schistosomiasis remains an important public health problem in many countries in tropical and subtropical regions, which affects about 200 million people worldwide, with another 700 million considered at risk of infection. Although the primary cause of pathogenesis of schistosomiasis is the granulomatous inflammatory responses, schistosomiasis patients experience long-term hidden pathologies that remain poorly investigated. Here, we found that schistosome infection resulted in RANKL-associated bone loss. Furthermore, our results indicated that both B cells and CD4⁺ T cells, particularly Tfh cell subset, in the peripheral lymphoid tissues are likely to be the important contributors to bone loss through releasing soluble RANKL. In addition, Tfh cells played a sufficient but not necessary role in schistosome infection-induced bone loss. Our findings highlight the risk of bone loss in schistosome-infected patients and the potential benefit of coupling bone therapy with anti-schistosome treatment.

Low dose gamma irradiation attenuates cyclophosphamide-induced cardiotoxicity in rats: role of NF-κB signaling pathway

PURPOSE

Cyclophosphamide (Cyp) is one of the most commonly used, wide spectrum chemotherapeutic agents. Cyp has multi-organ toxicities that are dose limiting, thus it's mostly used in chemotherapeutic combinations. Radiation is well known as a hazardous sort of energy, recent studies are interested in studying the beneficial therapeutic effects of low-dose gamma radiation. This study examined the protective effect of two different doses/dose-rates of irradiation either alone or combined with telmisartan against Cyp-induced cardiotoxicity.

MATERIALS AND METHODS

Rats were divided into seven groups; (1): Control, (2): Cyp, (3-4): 0.05 Gy low dose rate (LDR) irradiation, 0.25 Gy high dose rate (HDR) irradiation, respectively, prior to Cyp dose, (5-7): telmisartan either alone or with 0.05 Gy LDR-irradiation or 0.25 Gy HDR-irradiation, respectively, prior to Cyp dose. The current investigation studied the effect of Cyp alone or combined with different treatment regimens on serum cTn-I and LDH, nuclear factor-κB (NF-κB) pathway (p65/IκB/IKK-α/IKK-ß) in the myocardium. Pro-inflammatory cytokines IL-1ß, IL-6 and TNF-α were assessed in addition to histopathological examination of the heart.

RESULTS

Low-dose irradiation attenuated cardiac enzymes, pro-inflammatory cytokines, NF-κB content, and histology, in both low and HDRs. Furthermore, the combination of low-dose irradiation with telmisartan (an angiotensin-II receptor type-1 blocker and a known cardio-protective drug) offered the best histological results.

CONCLUSIONS

Low-dose irradiation-induced amelioration is partially but not completely through canonical activation of NF-κB, and may have another atypical pathway. While telmisartan probably ameliorates NF-κB totally through canonical pathway.

Embracing nature's complexity: Immunoparasitology in the wild

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

A review on the interactions between dendritic cells, filarial parasite and parasite-derived molecules in regulating the host immune responses

Lymphatic filariasis (LF) is the second leading cause of parasitic disabilities that affects millions of people in India and several other tropical countries. The complexity of this disease is endorsed by various immunopathological consequences such as lymphangitis, lymphadenitis and elephantiasis. The immune evasion strategies that a filarial parasite usually follows are chiefly initiated with the communication between the invaded parasites and parasite-derived molecules, with the Toll-like receptors (TLRs) present on the surface of the antigen-presenting cells (APCs). Classically, the filarial parasites interact with the DCs resulting in lowering of CD4⁺ T-cell responses. These CD4⁺ T-cell responses are the key players behind the immune-mediated pathologies associated with LF. In chronic stage, the canonical pro-inflammatory immune responses are shifted towards an anti-inflammatory subtype, which is favouring the parasite survivability within the host. The central theme of this review article is to present the overall immune response elicited when an APC, particularly a DC, encounters a filarial parasite.

Host Immunity and Inflammation to Pulmonary Helminth Infections

Helminths, including nematodes, cestodes and trematodes, are complex parasitic organisms that infect at least one billion people globally living in extreme poverty. Helminthic infections are associated with severe morbidity particularly in young children who often harbor the highest burden of disease. While each helminth species completes a distinct life cycle within the host, several helminths incite significant lung disease. This impact on the lungs occurs either directly from larval migration and host immune activation or indirectly from a systemic inflammatory immune response. The impact of helminths on the pulmonary immune response involves a sophisticated orchestration and activation of the host innate and adaptive immune cells. The consequences of activating pulmonary host immune responses are variable with several helminthic infections leading to severe, pulmonary compromise while others providing immune tolerance and protection against the development of pulmonary diseases. Further delineation of the convoluted interface between helminth infection and the pulmonary host immune responses is critical to the development of novel therapeutics that are critically needed to prevent the significant global morbidity caused by these parasites.

Cytokine responses to various larval stages of equine strongyles and modulatory effects of the adjuvant G3 in vitro

AIMS

To generate different larval stages of Strongylus vulgaris and to study cytokine responses in cultures of eqPBMC exposed to defined larval stages of S. vulgaris and cyathostomins with the aim to understand the early immune reaction to these parasites.

METHODS AND RESULTS

EqPBMC were exposed to S. vulgaris larvae (L3, exsheated L3 and L4) and cyathostomin L3 and analysed for cytokine gene expression. Procedures for decontamination, culturing and attenuation of larvae were established. Transcription of IL-4, IL-5 and IL-13 was induced by both S. vulgaris and cyathostomin L3. Moulting of S. vulgaris from L3 to L4 stage was accompanied by a shift to high expression of IL-5 and IL-9 (exsheated L3 and L4) and IFN-γ (L4 only). In parallel, the adjuvant G3 modified the cytokine profile induced by both parasites by reducing the expression of IL-4, IL-5 and IL-10 while concomitantly enhancing the expression of IFN-γ.

CONCLUSION

The L4 stage of S. vulgaris generated a cytokine profile different from that induced by the earlier L3 stage of S. vulgaris and cyathostomins. This diversity depending on the life cycle stage will have implications for the choice of antigen and adjuvant in future vaccine design.

Development, phenotypes of immune cells in BTBR T+Itpr3tf/J mice

Autism spectrum disorder (ASD) is a complex neurodevelopmental condition that is characterized by a lack of social interaction, decreased verbal and non-verbal communication skills, and stereotyped repetitive behavior. There is strong evidence that a dysregulated immune response may influence neurodevelopment and thus may have a role in the development of ASD. This study focuses on the characterization of immune cell phenotypes in the BTBR T⁺Itpr3^tf/J (BTBR) mouse strain, a widely used animal model for autism research. Our study demonstrated that BTBR mice have a different immune profile compared to C57BL/6J (B6) mice, which do not display ASD-like characteristics. Thymic cells of BTBR mice have more single positive (SP) CD4⁺ and CD8⁺ T cells and fewer double positive (DP) T cells than B6 mice. The development of T cells is increased in BTBR mice with regard to the double negative (DN4) population being much higher in BTBR mice. The spleens and blood of BTBR mice also have more T helper type 1 (Th1), T helper type 2 (Th2) and T regulatory (Treg) cells compared to B6 mice. Aire expression in the thymus and spleen of BTBR mice compared to B6 mice was equivalent and lower, respectively. The mature natural killer (NK) innate immune cell population in blood and spleen is lower in BTBR than B6 mice; NK cell development is blocked prior to the double positive (DN) CD11b⁺CD27⁺ stage in BTBR mice. Since BTBR mice have more CD4⁺ T cells and elevated numbers of Th1 (T-bet⁺) and Th2 (GATA3⁺) cells, their low defense against pathogen may be explained by the lower number of NK cells and the significantly lower Th1 to Th2 ratio. The elevated number of plasma cells and autoantibodies of BTBR mice may be due to less presence and function of splenic AIRE.

In silico design of a T-cell epitope vaccine candidate for parasitic helminth infection

Trichuris trichiura is a parasite that infects 500 million people worldwide, leading to colitis, growth retardation and Trichuris dysentery syndrome. There are no licensed vaccines available to prevent Trichuris infection and current treatments are of limited efficacy. Trichuris infections are linked to poverty, reducing children's educational performance and the economic productivity of adults. We employed a systematic, multi-stage process to identify a candidate vaccine against trichuriasis based on the incorporation of selected T-cell epitopes into virus-like particles. We conducted a systematic review to identify the most appropriate in silico prediction tools to predict histocompatibility complex class II (MHC-II) molecule T-cell epitopes. These tools were used to identify candidate MHC-II epitopes from predicted ORFs in the Trichuris genome, selected using inclusion and exclusion criteria. Selected epitopes were incorporated into Hepatitis B core antigen virus-like particles (VLPs). Bone marrow-derived dendritic cells and bone marrow-derived macrophages responded in vitro to VLPs irrespective of whether the VLP also included T-cell epitopes. The VLPs were internalized and co-localized in the antigen presenting cell lysosomes. Upon challenge infection, mice vaccinated with the VLPs+T-cell epitopes showed a significantly reduced worm burden, and mounted Trichuris-specific IgM and IgG2c antibody responses. The protection of mice by VLPs+T-cell epitopes was characterised by the production of mesenteric lymph node (MLN)-derived Th2 cytokines and goblet cell hyperplasia. Collectively our data establishes that a combination of in silico genome-based CD4+ T-cell epitope prediction, combined with VLP delivery, offers a promising pipeline for the development of an effective, safe and affordable helminth vaccine.

The impact of Clonorchis sinensis infection on immune response in mice with type II collagen-induced arthritis

BACKGROUND

Clonorchis sinensis infection could trigger strong immune responses in mice and humans. However, whether the C.sinensis infection has an impact on arthritis is unknown. Here we investigated the effect of C.sinensis infection on type II collagen-induced arthritis in BALB/c mice.

RESULTS

The mice were firstly infected with 45 C.sinensis metacercariae by oral gavage. Four weeks later, arthritis in mice was induced by type II collagen. Joint inflammation with severe redness and swelling in hind paws was observed in type II collagen-induced arthritis (CIA) mice. Besides, the physical activity was significantly reduced, but the respiratory exchange ratio was increased in CIA mice. Compared with CIA mice, C.sinensis infection could increase the severity of arthritis in CIA mice, based on the results of disease score and pathological changes. Compared to CIA mice, increased neutrophils and Ly6C^hi monocytes, decreased B cells and CD4⁺T cells, were found in C.sinensis infected CIA mice. Besides these, C.sinensis infected mice also displayed significantly higher levels of serum IL-4 and IL-17 than those in CIA mice.

CONCLUSIONS

Taken together, our data suggest that C.sinensis infection have a bad effect on arthritis, and could induce the abnormality of the immune response in mice with CIA.

Adjuvant-free immunization with infective filarial larvae as lymphatic homing antigen carriers

Controlled infection with intestinal nematodes has therapeutic potential for preventing the symptoms of allergic and autoimmune diseases. Here, we engineered larvae of the filarial nematode Litomosoides sigmodontis as a vaccine strategy to induce adaptive immunity against a foreign, crosslinked protein, chicken egg ovalbumin (OVA), in the absence of an external adjuvant. The acylation of filarial proteins with fluorescent probes or biotin was not immediately detrimental to larval movement and survival, which died 3 to 5 days later. At least some of the labeled and skin-inoculated filariae migrated through lymphatic vessels to draining lymph nodes. The immunization potential of OVA-biotin-filariae was compared to that of an OVA-bound nanoparticulate carrier co-delivered with a CpG adjuvant in a typical vaccination scheme. Production of IFNγ and TNFα by restimulated CD4+ cells but not CD8+ confirmed the specific ability of filariae to stimulate CD4+ T cells. This alternative method of immunization exploits the intrinsic adjuvancy of the attenuated nematode carrier and has the potential to shift the vaccination immune response towards cellular immunity.

Preventive CTLA-4-Ig Treatment Reduces Hepatic Egg Load and Hepatic Fibrosis in Schistosoma mansoni-Infected Mice

Background

Hepatic fibrosis and granuloma formation as a consequence of tissue entrapped eggs produced by female schistosomes characterize the pathology of Schistosoma mansoni infection. We have previously shown that single-sex infection with female schistosomes mitigates hepatic fibrosis after secondary infection. This was associated with an increased expression of cytotoxic T-lymphocyte-associated protein-4 (CTLA-4), known as a negative regulator of T cell activation. Based on these findings, we hypothesized that administration of agonistic CTLA-4-Ig (Belatacept) is capable to prevent and/or treat hepatic fibrosis during schistosomiasis.

Methods

Mice were infected with 50 S. mansoni cercariae and CTLA-4-Ig, or appropriated control-Ig was administered for 4 weeks. Preventive treatment started 4 weeks after infection, before onset of egg production, and therapeutic treatment started 8 weeks after infection when hepatic fibrosis was already established.

Results

When given early after infection, livers of CTLA-4-Ig-treated mice showed significantly reduced collagen deposition and decreased expression of profibrotic genes in comparison to controls. In addition, administration of CTLA-4-Ig suppressed the inflammatory T cell response in infected mice. If therapy was started at a later time point when fibrogenesis was initiated, CTLA-4-Ig had no impact on hepatic fibrosis.

Conclusion

We could demonstrate that an early preventive administration of CTLA-4-Ig suppresses effector T cell function and therefore ameliorates liver fibrosis. CTLA-4-Ig administration after onset of egg production fails to treat hepatic fibrosis.

Notch Signaling Orchestrates Helminth-Induced Type 2 Inflammation

Infection with helminth parasites poses a significant challenge to the mammalian immune system. The type 2 immune response to helminth infection is critical in limiting worm-induced tissue damage and expelling parasites. Conversely, aberrant type 2 inflammation can cause debilitating allergic disease. Recent studies have revealed that key type 2 inflammation-associated immune and epithelial cell types respond to Notch signaling, broadly regulating gene expression programs in cell development and function. Here, we discuss new advances demonstrating that Notch is active in the development, recruitment, localization, and cytokine production of immune and epithelial effector cells during type 2 inflammation. Understanding how Notch signaling controls type 2 inflammatory processes could inform the development of Notch pathway modulators to treat helminth infections and allergies.

Host responses to intestinal nematodes

Helminth infection remains common in developing countries, where residents who suffer from the consequences of such infections can develop serious physical and mental disorders and often persist in the face of serious economic problems. Intestinal nematode infection induces the development of Th2-type immune responses including the B-cell IgE response; additionally, this infection induces an increase in the numbers and activation of various types of effector cells, such as mast cells, eosinophils and basophils, as well as the induction of goblet cell hyperplasia, anti-microbial peptide production and smooth-muscle contraction, all of which contribute to expel nematodes. Innate immunity is important in efforts to eliminate helminth infection; cytokines, including IL-25, IL-33 and thymic stromal lymphopoietin, which are products of epithelial cells and mast cells, induce Th2 cells and group 2 innate lymphoid cells to proliferate and produce Th2 cytokines. Nematodes also facilitate chronic infection by suppression of immune reactions through an increased number of Treg cells. Immunosuppression by parasite infection may ultimately be beneficial for the host animals; indeed, a negative correlation has been found between parasite infection and the prevalence of inflammatory disease in humans.

First Responders: Innate Immunity to Helminths

Helminth infections represent a significant public health concern resulting in devastating morbidity and economic consequences across the globe. Helminths migrate through mucosal sites causing tissue damage and the induction of type 2 immune responses. Antihelminth protection relies on the mobilization and activation of multiple immune cells, including type 2 innate lymphocytes (ILC2s), basophils, mast cells, macrophages, and hematopoietic stem/progenitor cells. Further, epithelial cells and neurons have been recognized as important regulators of type 2 immunity. Collectively, these pathways stimulate host-protective responses necessary for worm expulsion and the healing of affected tissues. In this review we focus on the innate immune pathways that regulate immunity to helminth parasites and describe how better understanding of these pathways may lead to the development of new therapeutic strategies.

The opposite roles of PAS-5 and Galectin-1 in immune response during the early infection of Angiostrongylus cantonensis

BACKGROUND

Angiostrongylus cantonensis is a human zoonotic nematode parasite. Our previous studies found that PAS-5 and Galectin-1 (Gal-1) proteins of A. cantonensis could be strongly recognized by sera from mice infected with A. cantonensis. In this study, we further evaluated the potential roles of these two proteins in the induction of immune response in mice.

METHODS

Mice were immunized with recombinant PAS-5 or Gal-1 and then challenged with 30 infective A. cantonensis larvae following the last immunization. We then examined the infected mice for changes in serum antibodies and cytokines by ELISA, CD4+ T cells and CD4+CD25+FoxP3+ regulatory T cells (Tregs) by flow cytometry, and tissue damage severity by hematoxylin-eosin (H&E) staining.

RESULTS

Compared with control mice, the PAS-5-immunized mice exhibited increased levels of serum antibodies and cytokines (except for IL-10) at different time points post-infection. PAS-5 immunization promoted significant proliferation of CD4+ T cells, and caused more damage in the brain tissue. Vaccination with Gal-1 inhibited the production of antibodies (except for IgG1) and IFN-γ, but promoted the expression of IL-4 and IL-10. Gal-1 immunization results in significant increases in the levels of CD4+CD25+FoxP3+ Tregs, and mild inflammatory changes.

CONCLUSIONS

Taken together, our findings show that PAS-5 enhances, but Gal-1 inhibits the immune response in the early stage of A. cantonensis infections.

Altered levels of memory T cell subsets and common γc cytokines in Strongyloides stercoralis infection and partial reversal following anthelmintic treatment

BACKGROUND

CD4+ and CD8+ T cells are central players in immunity to helminth infections. However, the role of T cell subsets in human helminth infections is not well understood. In addition, the common γc cytokines, IL-2, IL-4, IL-7, IL-9 and IL-15 play an important role in the maintenance of these CD4+ and CD8+ T cell subsets.

METHODS

To examine the major T cell subsets and their association with the common γc cytokines, the absolute numbers of CD4+ and CD8+ naïve, central memory, effector memory and effector cells and the plasma levels of IL-2, IL-4, IL-7, IL-9 and IL-15 were measured in Strongyloides stercoralis (Ss) infected (INF, n = 60), helminth-uninfected (UN, n = 58) and in post treatment INF individuals.

RESULTS

Ss infection is characterized by significantly increased absolute numbers of naïve and decreased absolute numbers of central and effector memory CD4+ T cells in comparison to UN individuals. No significant difference in the numbers of CD8+ T cell subsets was observed between the groups. The numbers of naïve cells and central memory CD4+ T cells were significantly reversed after anthelmintic treatment. Circulating levels of IL-2, IL-7 and IL-15 were significantly diminished, whereas the levels of IL-4 and IL-9 were significantly increased in INF compared to UN individuals. Following anthelminthic treatment, IL-2, IL-7 and IL-15 levels were significantly increased, while IL-4 and IL-9 levels were significantly decreased. Our data also showed a significant positive correlation between the levels of IL-7 and the numbers of central and effector memory CD4+ T cells.

CONCLUSION

Ss infection is characterized by alterations in the absolute numbers of CD4+ T cell subsets and altered levels of common γc cytokines IL-2, IL-4, IL-7, IL-9 and IL-15; alterations which are partially reversed after anthelmintic treatment.

NF-kappaB: Two Sides of the Same Coin

Nuclear Factor-kappa B (NF-κB) is a transcription factor family that regulates a large number of genes that are involved in important physiological processes, including survival, inflammation, and immune responses. More recently, constitutive expression of NF-κB has been associated with several types of cancer. In addition, microorganisms, such as viruses and bacteria, cooperate in the activation of NF-κB in tumors, confirming the multifactorial role of this transcription factor as a cancer driver. Recent reports have shown that the NF-κB signaling pathway should receive attention for the development of therapies. In addition to the direct effects of NF-κB in cancer cells, it might also impact immune cells that can both promote or prevent tumor development. Currently, with the rise of cancer immunotherapy, the link among immune cells, inflammation, and cancer is a major focus, and NF-κB could be an important regulator for the success of these therapies. This review discusses the contrasting roles of NF-κB as a regulator of pro- and antitumor processes and its potential as a therapeutic target.

Type 2 cytokine responses: regulating immunity to helminth parasites and allergic inflammation

Purpose of Review

It is well established that T helper type 2 (T_H2) immune responses are necessary to provide protection against helminth parasites but also to promote the detrimental inflammation associated with allergies and asthma. Given the importance of type 2 immunity and inflammation, many studies have focused on better understanding the factors that regulate T_H2 cell development and activation. As a result, significant progress has been made in understanding the signaling pathways and molecular events necessary to promote T_H2 cell polarization. In addition to the adaptive compartment, emerging studies are better defining the innate immune pathways needed to promote T_H2 cell responses. Given the recent and substantial growth of this field, the purpose of this review is to highlight recent studies defining the innate immune events that promote immunity to helminth parasites and allergic inflammation.

Recent Findings

Emerging studies have begun to elucidate the importance of cytokine alarmins such as thymic stromal lymphopoietin (TSLP), IL-25 (IL-17E) and IL-33 in promoting type 2 immunity and inflammation following helminth challenge or exposure to allergens. Specifically, recent reports have begun to define the complex cellular networks these alarmins activate and their contribution to type 2 immunity and inflammation.

Summary

Our increased understanding of the pathways that regulate type 2 cytokine-mediated immunity and inflammation have revealed novel therapeutic targets to treat both helminth infections and allergic disease states.

T-cell tolerance and exhaustion in the clearance of Echinococcus multilocularis: role of inoculum size in a quantitative hepatic experimental model

The local immune mechanisms responsible for either self-healing or sustained chronic infection are not clear, in the development of E. multilocularis larvae. Here, we developed a suitable experimental model that mimics naturally infected livers, according to the parasite load. We demonstrated that local cellular immunity and fibrogenesis are actually protective and fully able to limit metacestode growth in the liver of low or medium dose-infected mice (LDG or MDG), or even to clear it, while impairment of cellular immunity is followed by a more rapid and severe course of the disease in high dose-infected mice (HDG). And recruitment and/ or proliferation of memory T cells (including CD4 Tem, CD8 Tcm and CD8 Tem) and imbalance of T1/T2/T17/Treg-type T cells in liver were not only associated with clearance of the parasite infection in LDG, but also with increased hepatic injury in HDG; in particular the dual role of CD8 T cells depending on the parasite load and the various stages of metacestode growth. Besides, we first demonstrate the association between LAG3- or 2B4-expressing T cells exhaustion and HD inocula in late stages. Our quantitative experimental model appears fully appropriate to study immunomodulation as a therapeutic strategy for patients with Alveolar Echinococcosis.

Type I interferon is required for T helper (Th) 2 induction by dendritic cells

Type 2 inflammation is a defining feature of infection with parasitic worms (helminths), as well as being responsible for widespread suffering in allergies. However, the precise mechanisms involved in T helper (Th) 2 polarization by dendritic cells (DCs) are currently unclear. We have identified a previously unrecognized role for type I IFN (IFN‐I) in enabling this process. An IFN‐I signature was evident in DCs responding to the helminth Schistosoma mansoni or the allergen house dust mite (HDM). Further, IFN‐I signaling was required for optimal DC phenotypic activation in response to helminth antigen (Ag), and efficient migration to, and localization with, T cells in the draining lymph node (dLN). Importantly, DCs generated from Ifnar1^−/− mice were incapable of initiating Th2 responses in vivo. These data demonstrate for the first time that the influence of IFN‐I is not limited to antiviral or bacterial settings but also has a central role to play in DC initiation of Th2 responses.

The role of rare innate immune cells in Type 2 immune activation against parasitic helminths

The complexity of helminth macroparasites is reflected in the intricate network of host cell types that participate in the Type 2 immune response needed to battle these organisms. In this context, adaptive T helper 2 cells and the Type 2 cytokines interleukin (IL)-4, IL-5, IL-9 and IL-13 have been the focus of research for years, but recent work has demonstrated that the innate immune system plays an essential role. Some innate immune cells that promote Type 2 immunity are relatively abundant, such as macrophages and eosinophils. However, we now appreciate that more rare cell types including group 2 innate lymphoid cells, basophils, mast cells and dendritic cells make significant contributions to these responses. These cells are found at low frequency but they are specialized to their roles - located at sites such as the skin, lung and gut, where the host combats helminth parasites. These cells respond rapidly and robustly to worm antigens and worm-induced damage to produce essential cytokines, chemokines, eicosanoids and histamine to activate damaged epithelium and to recruit other effectors. Thus, a greater understanding of how these cells operate is essential to understand how the host protects itself during helminth infection.

Negative Regulation of Type 2 Immunity

Type 2 immunity encompasses the mechanisms through which the immune system responds to helminths and an array of environmental substances such as allergens. In the developing world, billions of individuals are chronically infected with endemic parasitic helminths. In comparison, in the industrialized world, millions of individuals suffer from dysregulated type 2 immunity, referred to clinically as atopic diseases including asthma, allergic rhinitis, and atopic dermatitis. Thus, type 2 immunity must be carefully regulated to mount protective host responses yet avoid inappropriate activation and immunopathology. In this review, we describe the key players and connections at play in type 2 responses and focus on the emerging mechanisms involved in the negative regulation of type 2 immunity.

Increased hepatic Th2 and Treg subsets are associated with biliary fibrosis in different strains of mice caused by Clonorchis sinensis

Previous studies showed that CD4⁺T cells responses might be involved in the process of biliary fibrosis. However, the underlying mechanism resulting in biliary fibrosis caused by Clonorchis sinensis remains not yet fully elucidated. The objectives of the present study were to investigate the different profiles of hepatic CD4⁺T cell subsets (Th1, Th2, Th17 and Treg cells) and their possible roles in the biliary fibrosis of different strains of mice (C57BL/6, BALB/c and FVB mice) induced by C. sinensis infection. C57BL/6, BALB/c and FVB mice were orally gavaged with 45 metacercariae. All mice were sacrificed on 28 days post infection in deep anesthesia conditions. The leukocytes in the liver were separated to examine CD4⁺T cell subsets by flow cytometry and the left lobe of liver was used to observe pathological changes, collagen depositions and the concentrations of hydroxyproline. The most serious cystic and fibrotic changes appeared in FVB infected mice indicated by gross observation, Masson’s trichrome staining and hydroxyproline content detection. In contrast to C57BL/6 infected mice, diffuse nodules and more intensive fibrosis were observed in the BALB/c infected mice. No differences of the hepatic Th1 subset and Th17 subset were found among the three strains, but the hepatic Th2 and Treg cells and their relative cytokines were dramatically increased in the BALB/c and FVB infected groups compared with the C57BL/6 infected group (P<0.01). Importantly, increased Th2 subset and Treg subset all positively correlated with hydroxyproline contents (P<0.01). This result for the first time implied that the increased hepatic Th2 and Treg cell subsets were likely to play potential roles in the formation of biliary fibrosis in C. sinensis-infected mice.

Th2 responses are primed by skin dendritic cells with distinct transcriptional profiles

Connor et al. show that transcriptomic profiling of DCs exposed to two different Th2 stimuli in vivo reveals large numbers of differentially expressed genes but few similarities between conditions.

The dendritic cell signals required for the in vivo priming of IL-4–producing T cells are unknown. We used RNA sequencing to characterize DCs from skin LN of mice exposed to two different Th2 stimuli: the helminth parasite Nippostrongylus brasiliensis (Nb) and the contact sensitizer dibutyl phthalate (DBP)-FITC. Both Nb and DBP-FITC induced extensive transcriptional changes that involved multiple DC subsets. Surprisingly, these transcriptional changes were highly distinct in the two models, with only a small number of genes being similarly regulated in both conditions. Pathway analysis of expressed genes identified no shared pathways between Nb and DBP-FITC, but revealed a type-I IFN (IFN-I) signature unique to DCs from Nb-primed mice. Blocking the IFN-I receptor at the time of Nb treatment had little effect on DC migration and antigen transport to the LN, but inhibited the up-regulation of IFN-I–induced markers on DCs and effectively blunted Th2 development. In contrast, the response to DBP-FITC was not affected by IFN-I receptor blockade, a finding consistent with the known dependence of this response on the innate cytokine TSLP. Thus, the priming of Th2 responses is associated with distinct transcriptional signatures in DCs in vivo, reflecting the diverse environments in which Th2 immune responses are initiated.

Transcriptomic Study on Ovine Immune Responses to Fasciola hepatica Infection

BACKGROUND

Fasciola hepatica is not only responsible for major economic losses in livestock farming, but is also a major food-borne zoonotic agent, with 180 million people being at risk of infection worldwide. This parasite is sophisticated in manipulating the hosts' immune system to benefit its own survival. A better understanding of the mechanisms underpinning this immunomodulation is crucial for the development of control strategies such as vaccines.

METHODOLOGY/PRINCIPAL FINDINGS

This in vivo study investigated the global gene expression changes of ovine peripheral blood mononuclear cells (PBMC) response to both acute & chronic infection of F. hepatica, and revealed 6490 and 2364 differential expressed genes (DEGS), respectively. Several transcriptional regulators were predicted to be significantly inhibited (e.g. IL12 and IL18) or activated (e.g. miR155-5p) in PBMC during infection. Ingenuity Pathway Analysis highlighted a series of immune-associated pathways involved in the response to infection, including 'Transforming Growth Factor Beta (TGFβ) signaling', 'Production of Nitric Oxide in Macrophages', 'Toll-like Receptor (TLRs) Signaling', 'Death Receptor Signaling' and 'IL17 Signaling'. We hypothesize that activation of pathways relevant to fibrosis in ovine chronic infection, may differ from those seen in cattle. Potential mechanisms behind immunomodulation in F. hepatica infection are a discussed.

SIGNIFICANCE

In conclusion, the present study performed global transcriptomic analysis of ovine PBMC, the primary innate/adaptive immune cells, in response to infection with F. hepatica, using deep-sequencing (RNAseq). This dataset provides novel information pertinent to understanding of the pathological processes in fasciolosis, as well as a base from which to further refine development of vaccines.

Parasitic infection as a potential therapeutic tool against rheumatoid arthritis

Parasites, which are a recently discovered yet ancient dweller in human hosts, remain a great public health burden in underdeveloped countries, despite preventative efforts. Rheumatoid arthritis is a predominantly cosmopolitan health problem with drastic morbidity rates, although encouraging progress has been achieved regarding treatment. However, although various types of methods and agents have been applied clinically, their broad usage has been limited by their adverse effects and/or high costs. Sustained efforts have been exerted on the 'hygiene hypothesis' since the 1870s. The immunosuppressive nature of parasitic infections may offer potential insight into therapeutic strategies for rheumatoid arthritis, in which the immune system is overactivated. An increasing number of published papers are focusing on the preventive and/or curative effect of various parasitic infection on rheumatoid arthritis from experimental studies to large-scale epidemiological studies and clinical trials. Therefore, the present review aimed to provide a general literature review on the possible beneficial role of parasitic infection on rheumatoid arthritis.

Dysregulation of Th1, Th2, Th17, and T regulatory cell-related transcription factor signaling in children with autism

Autism is a neurodevelopmental disorder characterized by stereotypic repetitive behaviors, impaired social interactions, and communication deficits. Numerous immune system abnormalities have been described in individuals with autism including abnormalities in the ratio of Th1/Th2/Th17 cells; however, the expression of the transcription factors responsible for the regulation and differentiation of Th1/Th2/Th17/Treg cells has not previously been evaluated. Peripheral blood mononuclear cells (PBMCs) from children with autism (AU) or typically developing (TD) control children were stimulated with phorbol-12-myristate 13-acetate (PMA) and ionomycin in the presence of brefeldin A. The expressions of Foxp3, RORγt, STAT-3, T-bet, and GATA-3 mRNAs and proteins were then assessed. Our study shows that children with AU displayed altered immune profiles and function, characterized by a systemic deficit of Foxp3⁺ T regulatory (Treg) cells and increased RORγt⁺, T-bet⁺, GATA-3⁺, and production by CD4⁺ T cells as compared to TD. This was confirmed by real-time PCR (RT-PCR) and western blot analyses. Our results suggest that autism impacts transcription factor signaling, which results in an immunological imbalance. Therefore, the restoration of transcription factor signaling may have a great therapeutic potential in the treatment of autistic disorders.

TCR Signal Strength Alters T-DC Activation and Interaction Times and Directs the Outcome of Differentiation

The ability of CD4+ T cells to differentiate into effector subsets underpins their ability to shape the immune response and mediate host protection. During T cell receptor-induced activation of CD4+ T cells, both the quality and quantity of specific activatory peptide/MHC ligands have been shown to control the polarization of naive CD4+ T cells in addition to co-stimulatory and cytokine-based signals. Recently, advances in two--photon microscopy and tetramer-based cell tracking methods have allowed investigators to greatly extend the study of the role of TCR signaling in effector differentiation under in vivo conditions. In this review, we consider data from recent in vivo studies analyzing the role of TCR signal strength in controlling the outcome of CD4+ T cell differentiation and discuss the role of TCR in controlling the critical nature of CD4+ T cell interactions with dendritic cells during activation. We further propose a model whereby TCR signal strength controls the temporal aspects of T-DC interactions and the implications for this in mediating the downstream signaling events, which influence the transcriptional and epigenetic regulation of effector differentiation.

Multiple Exposures to Ascaris suum Induce Tissue Injury and Mixed Th2/Th17 Immune Response in Mice

Ascaris spp. infection affects 800 million people worldwide, and half of the world population is currently at risk of infection. Recurrent reinfection in humans is mostly due to the simplicity of the parasite life cycle, but the impact of multiple exposures to the biology of the infection and the consequences to the host's homeostasis are poorly understood. In this context, single and multiple exposures in mice were performed in order to characterize the parasitological, histopathological, tissue functional and immunological aspects of experimental larval ascariasis. The most important findings revealed that reinfected mice presented a significant reduction of parasite burden in the lung and an increase in the cellularity in the bronchoalveolar lavage (BAL) associated with a robust granulocytic pulmonary inflammation, leading to a severe impairment of respiratory function. Moreover, the multiple exposures to Ascaris elicited an increased number of circulating inflammatory cells as well as production of higher levels of systemic cytokines, mainly IL-4, IL-5, IL-6, IL-10, IL-17A and TNF-α when compared to single-infected animals. Taken together, our results suggest the intense pulmonary inflammation associated with a polarized systemic Th2/Th17 immune response are crucial to control larval migration after multiple exposures to Ascaris.

F4+ ETEC infection and oral immunization with F4 fimbriae elicits an IL-17-dominated immune response

Enterotoxigenic Escherichia coli (ETEC) are an important cause of post-weaning diarrhea (PWD) in piglets. Porcine-specific ETEC strains possess different fimbrial subtypes of which F4 fimbriae are the most frequently associated with ETEC-induced diarrhea in piglets. These F4 fimbriae are potent oral immunogens that induce protective F4-specific IgA antibody secreting cells at intestinal tissues. Recently, T-helper 17 (Th17) cells have been implicated in the protection of the host against extracellular pathogens. However, it remains unknown if Th17 effector responses are needed to clear ETEC infections. In the present study, we aimed to elucidate if ETEC elicits a Th17 response in piglets and if F4 fimbriae trigger a similar response. F4⁺ ETEC infection upregulated IL-17A, IL-17F, IL-21 and IL-23p19, but not IL-12 and IFN-γ mRNA expression in the systemic and mucosal immune system. Similarly, oral immunization with F4 fimbriae triggered a Th17 signature evidenced by an upregulated mRNA expression of IL-17F, RORγt, IL-23p19 and IL-21 in the peripheral blood mononuclear cells (PBMCs). Intriguingly, IL-17A mRNA levels were unaltered. To further evaluate this difference between systemic and mucosal immune responses, we assayed the cytokine mRNA profile of F4 fimbriae stimulated PBMCs. F4 fimbriae induced IL-17A, IL-17F, IL-22 and IL-23p19, but downregulated IL-17B mRNA expression. Altogether, these data indicate a Th17 dominated response upon oral immunization with F4 fimbriae and F4⁺ ETEC infection. Our work also highlights that IL-17B and IL-17F participate in the immune response to protect the host against F4⁺ ETEC infection and could aid in the design of future ETEC vaccines.

Comparative transcriptome profiling approach to glean virulence and immunomodulation-related genes of Fasciola hepatica

BACKGROUND

Fasciola hepatica causes chronic liver disease, fasciolosis, leading to significant losses in the livestock economy and concerns for human health in many countries. The identification of F. hepatica genes involved in the parasite's virulence through modulation of host immune system is utmost important to comprehend evasion mechanisms of the parasite and develop more effective strategies against fasciolosis. In this study, to identify the parasite's putative virulence genes which are associated with host immunomodulation, we explored whole transcriptome of an adult F. hepatica using current transcriptome profiling approaches integrated with detailed in silico analyses. In brief, the comparison of the parasite transcripts with the specialised public databases containing sequence data of non-parasitic organisms (Dugesiidae species and Caenorhabditis elegans) or of numerous pathogens and investigation of the sequences in terms of nucleotide evolution (directional selection) and cytokine signaling relation were conducted.

RESULTS

NGS of the whole transcriptome resulted in 19,534,766 sequence reads, yielding a total of 40,260 transcripts (N₅₀ = 522 bp). A number of the parasite transcripts (n = 1,671) were predicted to be virulence-related on the basis of the exclusive homology with the pathogen-associated data, positive selection or relationship with cytokine signaling. Of these, a group of the virulence-related genes (n = 62), not previously described, were found likely to be associated with immunomodulation based on in silico functional categorisation, showing significant sequence similarities with various immune receptors (i.e. MHC I class, TGF-β receptor, toll/interleukin-1 receptor, T-cell receptor, TNF receptor, and IL-18 receptor accessory protein), cytokines (i.e. TGF-β, interleukin-4/interleukin-13 and TNF-α), cluster of differentiations (e.g. CD48 and CD147) or molecules associated with other immunomodulatory mechanisms (such as regulation of macrophage activation). Some of the genes (n = 5) appeared to be under positive selection (Ka/Ks > 1), imitating proteins associated with cytokine signaling (through sequence homologies with thrombospondin type 1, toll/interleukin-1 receptor, TGF-β receptor and CD147).

CONCLUSIONS

With a comparative transcriptome profiling approach, we have identified a number of potential immunomodulator genes of F. hepatica (n = 62), which are firstly described here, could be employed for the development of better strategies (including RNAi) in the battle against both zoonotically and economically important disease, fasciolosis.