Innate immunomodulation to trypanosomatid parasite infections

A Flow Cytometry Study of the Binding and Stimulation Potential of Inactivated Trypanosoma evansi toward Dromedary Camel Leukocytes

Surra, a wasting disease caused by Trypanosoma evansi, is one of the major animal health burdens in camel-rearing countries, imposing significant economic losses due to reduced fertility and high mortality rates. The present study used inactivated T. evansi (from the Card Agglutination Test for Trypanosomes/Trypanosoma evansi; CATT/T. evansi) and flow cytometry to investigate their binding and activation potential toward camel leukocyte subsets. Labeling T. evansi with propidium iodide (PI) enabled their flow cytometric enumeration and identification with forward scatter (FSC; indicative for cell size) and side scatter (SSC; indicative for cell internal complexity) characteristics that are comparable with values reported for Trypanosoma cruzi. The incubation of PI-labeled non-opsonized T. evansi with camel leukocyte populations revealed that camel monocytes have the highest potential to bind T. evansi, followed by granulocytes and lymphocytes. The identification of pattern recognition receptors (PRRs) on camel immune cells and the pathogen-associated molecular patterns (PAMPs) in T. evansi that are responsible for this different binding capacity requires further studies. Stimulation of camel neutrophils with Trypanosoma evansi induced shape change, reactive oxygen species (ROS) production, and neutrophil extracellular traps (NET)-formation. To ensure that T. evansi, in the parasite concentration used in this study, is not apoptotic or necrotic to camel leukocytes, we evaluated cell apoptosis and necrosis after stimulation with T. evansi. The results revealed no impact of T. evansi stimulation for 2 h on the cell viability of camel leukocytes. Subsequent work may focus on the diagnostic employment of labeled T. evansi and flow cytometry for the detection of anti-Trypanosoma antibodies in camel serum. In addition, more efforts should be deployed to investigate the host-pathogen interaction mechanisms and the escape mechanisms of T. evansi in camels. To complete these data, further studies using the living or freshly killed parasites could also be implemented in camels and/or horses.

Immunomodulatory proteins from hookworms reduce cardiac inflammation and modulate regulatory responses in a mouse model of chronic Trypanosoma cruzi infection

Introduction

Hookworms are parasitic helminths that secrete a variety of proteins that induce anti-inflammatory immune responses, stimulating increased CD4 + Foxp3+ regulatory T cells and IL-10 production. Hookworm-derived recombinant proteins AIP-1 and AIP-2 have been shown to reduce inflammation in mouse models of inflammatory bowel disease and inflammatory airway disease by inducing CD4+Foxp3+ cells and IL-10 production. In contrast, chronic infection with the protozoal parasite Trypanosoma cruzi, the causative agent of Chagas disease, leads to chronic inflammation in tissues. Persistence of the parasites in tissues drives chronic low-grade inflammation, with increased infiltration of inflammatory cells into the heart, accompanied by increased production of inflammatory cytokines. There are no current antiparasitic drugs that effectively reduce or prevent chronic myocarditis caused by the onset of Chagas disease, thus new therapies are urgently needed. Therefore, the impact of AIP-1 and AIP-2 on myocarditis was investigated in a mouse model of chronic T. cruzi infection.

Methods

Female BALB/c mice infected with bioluminescent T. cruzi H1 strain trypomastigotes for 70 days were treated once daily for 7 days with 1mg/kg AIP-1 or AIP-2 protein by intraperitoneal injection. Control mice were left untreated or treated once daily for 14 days with 25mg/kg aspirin in drinking water. At 84 days of infection, splenocytes, cardiac tissue and serum were collected for evaluation.

Results

Treatment with both AIP-1 and AIP-2 proteins significantly reduced cardiac cellular infiltration, and reduced cardiac levels of IFNγ, IL-6 and IL-2. AIP-2 treatment reduced cardiac expression of COX-2. Further, while incubation with AIP-1 and AIP-2 proteins did not induce a significant upregulation of an immunoregulatory phenotype in dendritic cells (DC), there was a modest upregulation of CD11c +CD11b+MHCII+SIRPα+ expression, suggesting a regulatory phenotype. Ex-vivo stimulation of splenocytes from the treatment groups with AIP-1 loaded DC induced reduced levels of cytotoxic and pro-inflammatory T cells, stimulation with AIP-2 loaded DC specifically induced enhanced levels of CD4+CD25+Foxp3+ regulatory T cells among treatment groups.

Discussion

All in vivo and in vitro results demonstrate that hookworm-derived AIP-1 and AIP-2 proteins reduce T. cruzi induced cardiac inflammation, possibly through multiple anti-inflammatory mechanisms.

Macrophage Mitochondrial Biogenesis and Metabolic Reprogramming Induced by Leishmania donovani Require Lipophosphoglycan and Type I Interferon Signaling

Pathogen-specific rewiring of host cell metabolism creates the metabolically adapted microenvironment required for pathogen replication. Here, we investigated the mechanisms governing the modulation of macrophage mitochondrial properties by the vacuolar pathogen Leishmania. We report that induction of oxidative phosphorylation and mitochondrial biogenesis by Leishmania donovani requires the virulence glycolipid lipophosphoglycan, which stimulates the expression of key transcriptional regulators and structural genes associated with the electron transport chain. Leishmania-induced mitochondriogenesis also requires a lipophosphoglycan-independent pathway involving type I interferon (IFN) receptor signaling. The observation that pharmacological induction of mitochondrial biogenesis enables an avirulent lipophosphoglycan-defective L. donovani mutant to survive in macrophages supports the notion that mitochondrial biogenesis contributes to the creation of a metabolically adapted environment propitious to the colonization of host cells by the parasite. This study provides novel insight into the complex mechanism by which Leishmania metacyclic promastigotes alter host cell mitochondrial biogenesis and metabolism during the colonization process. IMPORTANCE To colonize host phagocytes, Leishmania metacyclic promastigotes subvert host defense mechanisms and create a specialized intracellular niche adapted to their replication. This is accomplished through the action of virulence factors, including the surface coat glycoconjugate lipophosphoglycan. In addition, Leishmania induces proliferation of host cell mitochondria as well as metabolic reprogramming of macrophages. These metabolic alterations are crucial to the colonization process of macrophages, as they may provide metabolites required for parasite growth. In this study, we describe a new key role for lipophosphoglycan in the stimulation of oxidative phosphorylation and mitochondrial biogenesis. We also demonstrate that host cell pattern recognition receptors Toll-like receptor 4 (TLR4) and endosomal TLRs mediate these Leishmania-induced alterations of host cell mitochondrial biology, which also require type I IFN signaling. These findings provide new insight into how Leishmania creates a metabolically adapted environment favorable to their replication.

In vitro anti-gastrointestinal cancer activity of Toxocara canis-derived peptide: Analyzing the expression level of factors related to cell proliferation and tumor growth

Background: Recently, a hypothesis about the negative relationship between cancers and parasites has been proposed and investigated; some parasitic worms and their products can affect the cancer cell proliferation. Due to the potential anti-cancer effect of helminthic parasites, in the present study, the excretory–secretory protein of Toxocara canis (T. canis) parasite was used to evaluate the possible anti-cancer properties and their effect on gastrointestinal and liver cancer cell proliferation-related genes in laboratory conditions.

Methods and materials: The selected synthesized peptide fraction from the T. canis excretory–secretory Troponin protein peptide (ES TPP) was exposed at 32, 64, 128, and 256 μg/ml concentrations to three gastrointestinal cancer cell lines AGS, HT-29, and Caco 2, as well as HDF cells as normal cell lines. We used the MTT assay to evaluate cellular changes and cell viability (CV). Variations in gene (Bcl-2, APAF1, ZEB1, VEGF, cyclin-D1, and caspase-3) expression were analyzed by real-time RT-PCR.

Results: After 24 h of exposure to pept1ides and cell lines, a decrease in CV was observed at a concentration of 64 μg/ml and compared to the control group. Then, after 48 h, a significant decrease in the CV of Caco 2 cells was observed at a concentration of 32 μg/ml; in the other cancer cell lines, concentrations above 32 μg/ml were effective. The peptide was able to significantly alter the expression of the studied genes at a concentration of 100 μg/ml.

Conclusion: Although the studied peptide at high concentrations could have a statistically significant effect on cancer cells, it is still far from the standard drug and can be optimized and promising in future studies.

Cytokine array analysis of mediators produced by human macrophages stimulated with Trichomonastenax

The incidence of oral colonization by the protozoan Trichomonas tenax correlates with gingival inflammation and periodontitis in humans. To determine whether T. tenax might contribute to inflammation by eliciting cytokines from human cells, differentiated THP-1 (dTHP-1) macrophages were cultured with live or sonicated T. tenax trophozoites, and the conditioned media were assayed for 36 different mediators by a membrane-based cytokine array. Scanning densitometry of the membranes revealed that live T. tenax trophozoites stimulated secretion of interleukin-8 (IL-8), macrophage migration inhibitory factor (MIF), IL-1β, intercellular adhesion molecule-1 (ICAM-1), and IL-1 receptor antagonist (IL-1ra) from dTHP-1 macrophages. T. tenax lysates stimulated release of IL-8, MIF, and IL-1ra. Despite often being classified as a commensal organism, T. tenax elicited a wider variety of cytokines than the human urogenital pathogen, T. vaginalis, which elicited only IL-8 and MIF production from dTHP-1 cells.

Epigenetic paradigms/exemplars of the macrophage: inflammasome axis in Leishmaniasis

The infectious paradigms have recently led to the recognition interplay of complex phenomenon underpinning disease diagnosis and prognosis. Evidently, parasitic infection studies are depicting converging trends of the epigenetic, environmental, and microbiome contributions, assisting pathogen-directed modulations of host biological system. The molecular details of epigenetic variations and memory, along with the multi-omics data at the interface of the host-pathogen level becomes strong indicator of immune cell plasticity, differentiation, and pathogen survival. Despite being one of the most important aspects of the disease's etiopathology, the epigenetic regulation of host-pathogen interactions and evolutionary epigenetics have received little attention thus far. Recent evidence has focused on the growing need to link epigenetic and microbiome modulations on parasite phenotypic plasticity and pathogen-induced host phenotypic plasticity for designing futuristic therapeutic regimes. Leishmaniasis is a neglected tropical illness with varying degrees of disease severity that is linked to a trans-species and epigenetic heredity process, including the pathogen-induced host and strain-specific modulations. The review configures research findings aligning to the epigenetic epidemiology niche, involving co-evolutionary epigenetic inheritance and plasticity disease models. The epigenetic exemplars focus on the host-pathogen interactome expanse at the macrophage-inflammasome axis.

Benznidazole Anti-Inflammatory Effects in Murine Cardiomyocytes and Macrophages Are Mediated by Class I PI3Kδ

Benznidazole (Bzl), the drug of choice in many countries for the treatment of Chagas disease, leads to parasite clearance in the early stages of infection and contributes to immunomodulation. In addition to its parasiticidal effect, Bzl inhibits the NF-κB pathway. In this regard, we have previously described that this occurs through IL-10/STAT3/SOCS3 pathway. PI3K pathway is involved in the regulation of the immune system by inhibiting NF-κB pathway through STAT3. In this work, the participation of PI3K in the immunomodulatory effects of Bzl in cardiac and immune cells, the main targets of Chagas disease, was further studied. For that, we use a murine primary cardiomyocyte culture and a monocyte/macrophage cell line (RAW 264.7), stimulated with LPS in presence of LY294002, an inhibitor of PI3K. Under these conditions, Bzl could neither increase SOCS3 expression nor inhibit the NOS2 mRNA expression and the release of NOx, both in cardiomyocytes and macrophages. Macrophages are crucial in the development of Chronic Chagas Cardiomyopathy. Thus, to deepen our understanding of how Bzl acts, the expression profile of M1-M2 macrophage markers was evaluated. Bzl inhibited the release of NOx (M1 marker) and increased the expression of Arginase I (M2 marker) and a negative correlation was found between them. Besides, LPS increased the expression of pro-inflammatory cytokines. Bzl treatment not only inhibited this effect but also increased the expression of typical M2-macrophage markers like Mannose Receptor, TGF-β, and VEGF-A. Moreover, Bzl increased the expression of PPAR-γ and PPAR-α, known as key regulators of macrophage polarization. PI3K directly regulates M1-to-M2 macrophage polarization. Since p110δ, catalytic subunit of PI3Kδ, is highly expressed in immune cells, experiments were carried out in presence of CAL-101, a specific inhibitor of this subunit. Under this condition, Bzl could neither increase SOCS3 expression nor inhibit NF-κB pathway. Moreover, Bzl not only failed to inhibit the expression of pro-inflammatory cytokines (M1 markers) but also could not increase M2 markers. Taken together these results demonstrate, for the first time, that the anti-inflammatory effect of Bzl depends on PI3K activity in a cell line of murine macrophages and in primary culture of neonatal cardiomyocytes. Furthermore, Bzl-mediated increase expression of M2-macrophage markers involves the participation of the p110δ catalytic subunit of PI3Kδ.

Molecular insights of a novel fish Toll-like receptor 9 homologue in Nibea albiflora to reveal its function as PRRs

Toll-like receptors (TLRs) are an important class of molecules involved in non-specific immunity, and they are also the bridge connecting between non-specific immunity and specific immunity. As a vital member of TLR family TLR9 can be activated by bacterial DNA and induce the production of inflammatory cytokines. In this study, a full length of TLR9 homologue of 3677 bp in Nibea albiflora (named as NaTLR9, GenBank accession no: MN125017.1) was characterized, and its ORF was 3180 bp encoding 1059 amino acid residues with a calculated molecular weight of 121.334 kDa (pI = 6.29). Several leucine-rich repeated sequences (LRR domain) and conservative TIR domain were found in NaTLR9, which was mainly expressed in dendritic cells and macrophages. The phylogenetic and synteny analysis further revealed high sequence identity of NaTLR9 with its counterparts of other teleost, confirming their correct nomenclature and conservative during evolution as an important pattern recognition receptor. The NaTLR9-TIR-pEGFP-N1 fusion protein showed green fluorescence and mainly distributed in the cytoplasm. After co-transfection of NaTLR9-TIR-pEGFP-N1 and NaMyD88-pDsRED-Monomer-N1, green fluorescence obviously overlapped with red and changed into yellowish-green, which suggested that there might be the interaction between homologous NaTLR9-TIR and MyD88. Based on this result the pCDNA3.1-NaTLR9-TIR-flag and pcMV-NaMyD88-TIR-Myc plasmids were co-transfected into 293T cells for the immunoprecipitation test. According to Western blot, TLR9 and MyD88 protein could interact with each other. Furthermore, NaTLR9 was ubiquitously expressed in all the investigated tissues, most abundantly in head kidney, followed by stomach, spleen, liver and gill, but lower in muscle. The vitro immune stimulation experiments revealed that Pseudomonas plecoglossicida and polyinosinic-polycytidylic acid [Poly (I:C)] induced higher levels of NaTLR9 mRNA expression with the peaks of 9.52 times at 2 h and 39.91 times at 24 h compared with the control group respectively. The functional domains (LRRs and TIR, named NaTLR9-TIR and NaTLR9-LRR respectively) of NaTLR9 were expressed and purified, the recombinant proteins both could bind three kinds of typical aquatic pathogenic bacteria (Vibrio. parahaemolyticus, Vibrio alginolyticus, and Vibrio harveyi), which showed that NaTLR9 could couple to bacteria by its function domains. The aforementioned results indicated that NaTLR9 played a significant role in the defense against pathogenic bacteria infection in innate immune response of sciaenidae fish, which may provide some further understandings of the regulatory mechanisms in the teleostean innate immune system.

Chagas disease: Immunology of the disease at a glance

Chagas disease is an important neglected disease that affects 6-7 million people worldwide. The disease has two phases: acute and chronic, in which there are different clinical symptoms. Controlling the infection depends on innate and acquired immune responses, which are activated during the initial infection and are critical for host survival. Furthermore, the immune system plays an important role in the therapeutic success. Here we summarize the importance of the immune system cytokines in the pathology outcome, as well as in the treatment.

Trypanosoma evansi evades host innate immunity by releasing extracellular vesicles to activate TLR2-AKT signaling pathway

Surra, one of the most important animal diseases with economic consequences in Asia and South America, is caused by Trypanosoma evansi. However, the mechanism of immune evasion by T. evansi has not been extensively studied. In the present study, T. evansi extracellular vesicles (TeEVs) were characterized and the role of TeEVs in T. evansi infection were examined. The results showed that T. evansi and TeEVs could activate TLR2-AKT pathway to inhibit the secretions of IL-12p40, IL-6, and TNF-α in mouse BMDMs. TLR2^−/- mice and mice with a blocked AKT pathway were more resistant to T. evansi infection than wild type (WT) mice, with a significantly lower infection rate, longer survival time and less parasite load, as well as an increased secretion level of IL-12p40 and IFN-γ. Kinetoplastid membrane protein-11 (KMP-11) of TeEVs could activate AKT pathway and inhibit the productions of IL-12p40, TNF-α, and IL-6 in vitro. TeEVs and KMP-11 could inhibit the productions of IL-12p40 and IFN-γ, promote T. evansi proliferation and shorten the survival time of infected mice in vivo. In conclusion, T. evansi could escape host immune response through inhibiting the productions of inflammatory cytokines via secreting TeEVs to activate TLR2-AKT pathway. KMP-11 in TeEVs was involved in promoting T. evansi infection.

Extracellular vesicles (EVs) secreted by Trypanosoma evansi (T. evansi) activate the TLR2-AKT signaling pathway to inhibit the production of inflammatory cytokines, thereby escaping the host’s immune response. Kinetoplastid membrane protein-11 (KMP-11) in EVs is related to the promotion of T.evansi infection via AKT pathway.

Host immune response against leishmaniasis and parasite persistence strategies: A review and assessment of recent research

Leishmaniasis, a neglected parasitic disease caused by a unicellular protozoan of the genus Leishmania, is transmitted through the bite of a female sandfly. The disease remains a major public health problem and is linked to tropical and subtropical regions, with an endemic picture in several regions, including East Africa, the Mediterranean basin and South America. The different causative species display a diversity of clinical presentations; therefore, the immunological data on leishmaniasis are both scarce and controversial for the different forms and infecting species of the parasite. The present review highlights the main immune parameters associated with leishmaniasis that might contribute to a better understanding of the pathogenicity of the parasite and the clinical outcomes of the disease. Our aim was to provide a concise overview of the immunobiology of the disease and the factors that influence it, as this knowledge may be helpful in developing novel chemotherapeutic and vaccine strategies.

Mixed signals - how Trypanosoma cruzi exploits host-cell communication and signaling to establish infection

Chagas disease (American trypanosomiasis) is a 'neglected' pathology that affects millions of people worldwide, mainly in Latin America. Trypanosoma cruzi, the causative agent, is an obligate intracellular parasite with a complex and diverse biology that infects several mammalian species, including humans. Because of genetic variability among strains and the presence of four biochemically and morphologically distinct parasite forms, the outcome of T. cruzi infection varies considerably depending on host cell type and parasite strain. During the initial contact, cellular communication is established by host-recognition-mediated responses, followed by parasite adherence and penetration. For this purpose, T. cruzi expresses a variety of proteins that modify the host cell, enabling it to safely reach the cytoplasm. After entry into the host cell, T. cruzi forms a transitory structure termed 'parasitophorous vacuole' (PV), followed by its cytoplasmic replication and differentiation after PV rupture, and subsequent invasion of other cells. The success of infection, maintenance and survival inside host cells is facilitated by the ability of T. cruzi to subvert various host signaling mechanisms. We focus in this Review on the various mechanisms that induce host cytoskeletal rearrangements, activation of autophagy-related proteins and crosstalk among major immune response regulators, as well as recent studies on the JAK-STAT pathway.

Dual RNA-Seq transcriptome analysis of chicken macrophage-like cells (HD11) infected in vitro with Eimeria tenella

The study aimed to monitor parasite and host gene expression during the early stages of Eimeria tenella infection of chicken cells using dual RNA-Seq analysis. For this, we used chicken macrophage-like cell line HD11 cultures infected in vitro with purified E. tenella sporozoites. Cultures were harvested between 2 and 72 h post-infection and mRNA was extracted and sequenced. Dual RNA-Seq analysis showed clear patterns of altered expression for both parasite and host genes during infection. For example, genes in the chicken immune system showed upregulation early (2–4 h), a strong downregulation of genes across the immune system at 24 h and a repetition of early patterns at 72 h, indicating that invasion by a second generation of parasites was occurring. The observed downregulation may be due to immune self-regulation or to immune evasive mechanisms exerted by E. tenella. Results also suggested pathogen recognition receptors involved in E. tenella innate recognition, MRC2, TLR15 and NLRC5 and showed distinct chemokine and cytokine induction patterns. Moreover, the expression of several functional categories of Eimeria genes, such as rhoptry kinase genes and microneme genes, were also examined, showing distinctive differences which were expressed in sporozoites and merozoites.

Fasciola hepatica induces weak NETosis and low production of intra- and extracellular ROS in exposed bovine polymorphonuclear neutrophils

Fasciola hepatica is the causative agent of fasciolosis, a worldwide distributed zoonotic disease, leading to hepatitis in humans and livestock. Newly excysted juveniles (NEJ) of F. hepatica are the first invasive stages to encounter leukocytes of host innate immune system in vivo. Among leukocytes, polymorphonuclear neutrophils (PMN) are the most abundant granulocytes of blood system and first ones to migrate into infection sites. PMN are able to cast neutrophil extracellular traps (NETs), also known as NETosis, consisting of nuclear DNA, decorated with histones, enzymes and antimicrobial peptides, which can entrap and eventually kill invasive parasites. Given that only few large parasitic helminths have been identified as potent NETosis inducers, here we studied for first time whether different F. hepatica stages can also trigger NETosis. Therefore, isolated bovine PMN were co-cultured with viable F. hepatica-NEJ, -metacercariae, -eggs and soluble antigen (FhAg). Interestingly, all stages failed to induce considerable levels of NETosis as detected by immunofluorescence- and scanning electron microscopy (SEM) analyses. NEJ remained motile until the end of incubation period. In line, NETosis quantification via nuclear area expansion (NAE) analysis revealed NEJ as weak NETosis inducers. However, bovine PMN frequently displaced towards motile NEJ and were found attached to NEJ surfaces. Functional PMN chemotaxis assays using vital F. hepatica-NEJ revealed a slight increase of PMN migration when compared to non-exposed controls. Additional experiments on intra- and extracellular reactive oxygen species (ROS) production revealed that soluble FhAg failed to induce ROS production of exposed PMN. Finally, mitochondrial oxygen consumption rates (OCR), extracellular acidification rates (ERAC) and proton production rates (PPR) were not significantly increased in FhAg-stimulated PMN. In summary, data suggest that F. hepatica might effectively evade PMN activation and NETosis by secreting parasite-specific molecules to either resolve NETs or to impair NETosis signaling pathways. We call for future molecular analysis not only on F. hepatica-derived NETosis modulation but also on its possible role in fasciolosis-associated pathology in vivo.

Interaction of Signaling Lymphocytic Activation Molecule Family 1 (SLAMF1) receptor with Trypanosoma cruzi is strain-dependent and affects NADPH oxidase expression and activity

The receptor Signaling Lymphocyte-Activation Molecule Family 1 (SLAMF1) controls susceptibility to Infection by the lethal Trypanosoma cruzi Y strain. To elucidate whether genetic diversity of the parasite was related with disease susceptibility, we further analyzed the role of SLAMF1 using 6 different Trypanosoma cruzi strains including Y. The interaction of SLAMF1 receptor with T. cruzi was evidenced by fluorescence microscopy, flow cytometry and quantitative PCR. All the strains, except VFRA, showed a decrease in parasite load in infected macrophages in Slamf1^-/- compared to BALB/c. In macrophages gene expression NADPH oxidase (NOX2), and reactive oxygen species (ROS) production increased in Slamf1^-/- compared to BALB/c in 5 out of 6 strains. However, Slamf1^-/-macrophages infected with VFRA strain exhibited a divergent behavior, with higher parasite load, lower NOX2 expression and ROS production compared to BALB/c. Parasitological and immunological studies in vivo with Y strain showed that in the absence of SLAMF1 the immune response protected mice from the otherwise lethal Y infection favoring a proinflammatory response likely involving CD4, CD8, dendritic cells and classically activated macrophages. In the case of VFRA, no major changes were observed in the absence of SLAMF1. Thus, the results suggest that the T. cruzi affects SLAMF1-dependent ROS production, controlling parasite replication in macrophages and affecting survival in mice in a strain-dependent manner. Further studies will focus in the identification of parasite molecules involved in SLAMF1 interaction to explain the immunopathogenesis of the disease.

Chagas disease, caused by Trypanosoma cruzi, is characterized by an acute phase, with low mortality, and after many years without any sign of disease, patients develop a symptomatic chronic phase, characterized by cardiomyopathy and/or digestive mega syndromes. These differences have been attributed to the high genetic variability of this parasite. We have shown that the receptor Signaling Lymphocyte-Activation Molecule Family 1 (SLAMF1) controls susceptibility to Infection by the lethal T. cruzi Y strain. Here we studied in detail the immunopathogenic role of SLAMF1 using 6 genetically diverse strains of T. cruzi using in vitro and in vivo approaches. Our results indicate an important role of SLAMF1 in T. cruzi infection which is parasite strain-dependent. We found that parasites interact with SLAMF1 in macrophages affecting NADPH oxidase (NOX2) expression and reactive oxygen species (ROS) production 5 out of 6 strains tested. Y and VFRA strains showed a divergent behavior in vitro and the role of SLAMF1 in the in vivo infection was also strikingly different. The Y strain caused 70% mortality in BALB/c mice but not in Slamf1^-/- mice. The proinflammatory response was stronger in the last, suggesting that SLAMF1 was repressing protective immune responses of mice infected with the Y strain. In contrast, for VFRA, SLAMF1 deficiency resulted in 100% survival of BALB/c mice, without major changes in the immune response in the absence of SLAMF1. Thus, the results indicate that SLAMF1 receptor interacts with T. cruzi, affecting parasite replication and ROS production in macrophages as well as the adaptive immune response in mice in a parasite strain-dependent manner. Future studies will focus in understanding the immunopathogenic role of SLAMF1 during T. cruzi infection.

Effect of vegetable oils on the experimental infection of mice with Trypanosoma congolense

Vegetable oils are frequently used as solvents for lipophilic materials; accordingly, the effects of their components should be considered in animal experiments. In this study, the effects of various vegetable oils on the course of Trypanosoma congolense infection were examined in mice. C57BL/6J mice were orally administered four kinds of oils (i.e., coconut oil, olive oil, high oleic safflower oil, and high linoleic safflower oil) with different fatty acid compositions and infected with T. congolense IL-3000. Oil-treated mice infected with T. congolense showed significantly higher survival rates and lower parasitemia than those of control mice. Notably, coconut oil, which mainly consists of saturated fatty acids, delayed the development of parasitemia at the early stage of infection. These results indicated that vegetable oil intake could affect T. congolense infection in mice. These findings have important practical implications; for example, they suggest the potential effectiveness of vegetable oils as a part of the regular animal diet for controlling tropical diseases and indicate that vegetable oils are not suitable solvents for studies of the efficacy of lipophilic agents against T. congolense.

Methionine enkephalin inhibits influenza A virus infection through upregulating antiviral state in RAW264.7 cells

MENK, as an immune adjuvant, has potential immune-regulatory activity on innate and adaptive immune cells. The aim of this work was to investigate the antiviral effect of MENK on influenza virus-infected murine macrophage cells (RAW264.7) and its underlying mechanisms. The results showed that MENK markedly inhibited influenza A virus (H1N1) replication in pre- and post-MENK treatment, especially in pre-MENK treatment. The mechanisms exploration revealed that MENK (10 mg/mL) significantly inhibited the nucleoprotein (NP) of influenza virus and up-regulated levels of IL-6, TNF-α and IFN-β compared with those in H1N1 control group. Further experiments confirmed that antiviral effects of MENK was associated with promotion of opioid receptor (MOR) as well as activation of NF-κB p65 inducing cellular antiviral status. The data suggest that MENK should be potential candidate for prophylactic or therapeutic treatment against H1N1 influenza virus.

Tartrate-resistant phosphatase type 5 in Trypanosoma cruzi is important for resistance to oxidative stress promoted by hydrogen peroxide

Trypanosoma cruzi (the causative agent of Chagas disease) presents a complex life cycle that involves adaptations in vertebrate and invertebrate hosts. As a protozoan parasite of hematophagous insects and mammalian hosts, T. cruzi is exposed to reactive oxygen species (ROS). To investigate the functionality of T. cruzi tartrate-resistant acid phosphatase type 5 (TcACP5), we cloned, superexpressed and purified the enzyme. Purified TcACP5 exhibited a V_max and apparent K_m for pNPP hydrolysis of 7.7 ± 0.2 nmol pNP × μg^-1 × h^-1 and 169.3 ± 22.6 μM, respectively. The pH dependence was characterized by sharp maximal activity at pH 5.0, and inhibition assays demonstrated its sensitivity to acid phosphatase inhibitors. Similar activities were obtained with saturating concentrations of P-Ser and P-Thr as substrates. The enzyme metabolizes hydrogen peroxide (H₂O₂) in vitro, and parasites superexpressing this enzyme were more resistant to oxidative stress promoted by H₂O₂. Taken together, these results suggest that TcACP5 plays a central role in phosphoryl transfer and redox reactions.

Trypanosoma brucei gambiense excreted/secreted factors impair lipopolysaccharide-induced maturation and activation of human monocyte-derived dendritic cells

Trypanosoma brucei gambiense, an extracellular eukaryotic flagellate parasite, is the main etiological agent of human African trypanosomiasis (HAT) or sleeping sickness. Dendritic cells (DCs) play a pivotal role at the interface between innate and adaptive immune response and are implicated during HAT. In this study, we investigated the effects of T gambiense and its excreted/secreted factors (ESF) on the phenotype of human monocyte-derived DCs (Mo-DCs). Mo-DCs were cultured with trypanosomes, lipopolysaccharide (LPS), ESF derived from T gambiense bloodstream strain Biyamina (MHOM/SD/82), or both ESF and LPS. Importantly, ESF reduced the expression of the maturation markers HLA-DR and CD83, as well as the secretion of IL-12, TNF-alpha and IL-10, in LPS-stimulated Mo-DCs. During mixed-leucocyte reactions, LPS- plus ESF-exposed DCs induced a non-significant decrease in the IFN-gamma/IL-10 ratio of CD4 + T-cell cytokines. Based on the results presented here, we raise the hypothesis that T gambiense has developed an immune escape strategy through the secretion of paracrine mediators in order to limit maturation and activation of human DCs. The identification of the factor(s) in the T gambiense ESF and of the DCs signalling pathway(s) involved may be important in the development of new therapeutic targets.

IL-10/STAT3/SOCS3 Axis Is Involved in the Anti-inflammatory Effect of Benznidazole

Anti-parasitic treatment for Chagas disease mainly relies on benznidazole, which is virtually the only drug available in the market. Besides its anti-parasitic effects, benznidazole has anti-inflammatory properties. In this work we studied the mechanisms involved in the latter, demonstrating the participation of the IL-10/STAT3/SOCS3 pathway. To achieve this goal, the anti-inflammatory properties of benznidazole were studied using an in vitro model of cardiomyocyte primary culture stimulated with LPS. LPS increased both SOCS3 expression and STAT3 phosphorylation. The addition of benznidazole increased their expression even further. Specific inhibition of STAT3 precluded this effect, suggesting a role for STAT3 in the increase of SOCS3 expression induced by benznidazole. To assess the participation of SOCS3 in the anti-inflammatory effect of benznidazole, we accomplished specific knockdown of SOCS3 with siRNA. Silencing of SOCS3 in cardiomyocytes precluded the inhibitory effects of benznidazole on TNF-α, IL-6, iNOS expression and NO release. Moreover, in the absence of SOCS3, benznidazole could neither prevent IKK phosphorylation nor IκBα degradation, supporting the notion that SOCS3 is required for the benznidazole-mediated inhibition of the NF-κB pathway. Previously, we demonstrated that IL-10 increases the expression of SOCS3 in cultured cardiomyocytes. Here, we found that benznidazole shows a trend to increased IL-10 expression. To evaluate whether benznidazole increased SOCS3 in an IL-10-dependent manner, cardiomyocytes from IL-10 knockout mice were pre-treated with benznidazole and stimulated with LPS. Benznidazole neither inhibited NO release nor avoid IKK phosphorylation or IκBα degradation, showing that IL-10 is required for benznidazole-mediated inhibition of NF-κB. Moreover, exogenous addition of IL-10 to IL-10 knockout cardiomyocytes restored the inhibitory effect of benznidazole on NO release. The results reported herein show, for the first time, that the IL-10/STAT3/SOCS3 axis is involved in the anti-inflammatory effects of benznidazole. These findings may add up to new therapeutic strategies for chronic Chagas disease given its inflammatory nature.

Glycoconjugates of Gram-negative bacteria and parasitic protozoa - are they similar in orchestrating the innate immune response?

Innate immunity is an evolutionarily ancient form of host defense that serves to limit infection. The invading microorganisms are detected by the innate immune system through germline-encoded PRRs. Different classes of PRRs, including TLRs and cytoplasmic receptors, recognize distinct microbial components known collectively as PAMPs. Ligation of PAMPs with receptors triggers intracellular signaling cascades, activating defense mechanisms. Despite the fact that Gram-negative bacteria and parasitic protozoa are phylogenetically distant organisms, they express glycoconjugates, namely bacterial LPS and protozoan GPI-anchored glycolipids, which share many structural and functional similarities. By activating/deactivating MAPK signaling and NF-κB, these ligands trigger general pro-/anti-inflammatory responses depending on the related patterns. They also use conservative strategies to subvert cell-autonomous defense systems of specialized immune cells. Signals triggered by Gram-negative bacteria and parasitic protozoa can interfere with host homeostasis and, depending on the type of microorganism, lead to hypersensitivity or silencing of the immune response. Activation of professional immune cells, through a ligand which triggers the opposite effect (antagonist versus agonist) appears to be a promising solution to restoring the immune balance.

Camouflage and interception: how pathogens evade detection by intracellular nucleic acid sensors

Intracellular DNA and RNA sensors play a vital part in the innate immune response to viruses and other intracellular pathogens, causing the secretion of type I interferons, cytokines and chemokines from infected cells. Pathogen RNA can be detected by retinoic-acid inducible gene I-like receptors in the cytosol, whereas cytosolic DNA is recognized by DNA sensors such as cyclic GMP-AMP synthase (cGAS). The resulting local immune response, which is initiated within hours of infection, is able to eliminate many pathogens before they are able to establish an infection in the host. For this reason, all viruses, and some intracellular bacteria and protozoa, need to evade detection by nucleic acid sensors. Immune evasion strategies include the sequestration and modification of nucleic acids, and the inhibition or degradation of host factors involved in innate immune signalling. Large DNA viruses, such as herpesviruses, often use multiple viral proteins to inhibit signalling cascades at several different points; for instance herpes simplex virus 1 targets both DNA sensors cGAS and interferon-γ-inducible protein 16, as well as the adaptor protein STING (stimulator of interferon genes) and other signalling factors in the pathway. Viruses with a small genome encode only a few immunomodulatory proteins, but these are often multifunctional, such as the NS1 protein from influenza A virus, which inhibits RNA sensing in multiple ways. Intracellular bacteria and protozoa can also be detected by nucleic acid sensors. However, as the type I interferon response is not always beneficial for the host under these circumstances, some bacteria subvert, rather than evade, these signalling cascades for their own gain.

Vaccination with whole-cell killed or recombinant leishmanial protein and toll-like receptor agonists against Leishmania tropica in BALB/c mice

One strategy to control leishmaniasis is vaccination with potent antigens alongside suitable adjuvants. The use of toll-like receptor (TLR) agonists as adjuvants is a promising approach in Leishmania vaccine research. Leishmania (L.) tropica is among the less-investigated Leishmania species and a causative agent of cutaneous and sometimes visceral leishmaniasis with no approved vaccine against it. In the present study, we assessed the adjuvant effects of a TLR4 agonist, monophosphoryl lipid A (MPL) and a TLR7/8 agonist, R848 beside two different types of Leishmania vaccine candidates; namely, whole-cell soluble L. tropica antigen (SLA) and recombinant L. tropica stress-inducible protein-1 (LtSTI1). BALB/c mice were vaccinated three times by the antigens (SLA or LtSTI1) with MPL or R848 and then were challenged by L. tropica. Delayed-type hypersensitivity (DTH), parasite load, disease progression and cytokines (IL-10 and IFN-γ) responses were assessed. In general compared to SLA, application of LtSTI1 resulted in higher DTH, higher IFN-γ response and lower lymph node parasite load. Also compared to R848, MPL as an adjuvant resulted in higher DTH and lower lymph node parasite load. Although, no outstanding ability for SLA and R848 in evoking immune responses of BALB/c mice against L. tropica infection could be observed, our data suggest that LtSTI1 and MPL have a better potential to control L. tropica infection and could be pursued for the development of effective vaccination strategies.

Characterization of TLR5 and TLR9 from silver pomfret (Pampus argenteus) and expression profiling in response to bacterial components

Toll like receptor (TLR) 5 and 9 are important members of the TLR family that play key roles in innate immunity in all vertebrates. In this study, paTLR5 and paTLR9 were identified in silver pomfret (Pampus argenteus), a marine teleost of great economic value. Open reading frames (ORFs) of paTLR5 and paTLR9 are 2646 and 3225 bp, encoding polypeptides of 881 and 1074 amino acids, respectively. Sequence analysis revealed several conserved characteristic features, including signal peptides, leucine-rich repeat (LRR) motifs, and a Toll/interleukin-I receptor (TIR) domain. Sequence, phylogenetic and synteny analysis revealed high sequence identity with counterparts in other teleosts, confirming their correct nomenclature and conservation during evolution. Quantitative real-time PCR revealed that the that both TLRs were ubiquitously expressed in all investigated tissues, most abundantly in liver, kidney, spleen, intestine and gill, but lower in muscle and skin. In vitro immunostimulation experiments revealed that Aeromonas hydrophila lipopolysaccharide (LPS) and Vibrio anguillarum flagellin induced higher levels of paTLR9 and paTLR5 mRNA expression in isolated fish intestinal epithelial cells (FIECs) than Lactobacillus plantarum lipoteichoic acid (LTA), but all increased the secretion of IL-6 and TNF-α and induced cell apoptosis and necrosis. Together, these results indicate that paTLR5 and paTLR9 may function in the response to bacterial pathogens. Our findings enhance our understanding of the function of TLRs in the innate immune system of silver pomfret and other teleosts.

Phospho-proteomic analysis of primary human colon epithelial cells during the early Trypanosoma cruzi infection phase

The protozoan parasite Trypanosoma cruzi, the causative agent of Chagas disease, causes severe morbidity and mortality in afflicted individuals. About 30% of T. cruzi-infected individuals present with cardiac, gastrointestinal tract, and/or neurological disorders. Megacolon, one of the major pathologies of Chagas disease, is accompanied by gastrointestinal motility disorders. The molecular mechanism of T. cruzi-mediated megacolon in Chagas disease is currently unknown. To decipher the molecular mechanism of T. cruzi-induced alteration in the colon during the early infection phase, we exposed primary human colonic epithelial cells (HCoEpiC) to invasive T. cruzi trypomastigotes at multiple time points to determine changes in the phosphoprotein networks in the cells following infection using proteome profiler Human phospho-kinase arrays. We found significant changes in the phosphorylation pattern that can mediate cellular deregulations in colonic epithelial cells after infection. We detected a significant increase in the levels of phosphorylated heat shock protein (p-HSP) 27 and transcription factors that regulate various cellular functions, including c-Jun and CREB. Our study confirmed significant upregulation of phospho (p-) Akt S473, p-JNK, which may directly or indirectly modulate CREB and c-Jun phosphorylation, respectively. We also observed increased levels of phosphorylated CREB and c-Jun in the nucleus. Furthermore, we found that p-c-Jun and p-CREB co-localized in the nucleus at 180 minutes post infection, with a maximum Pearson correlation coefficient of 0.76±0.02. Increased p-c-Jun and p-CREB have been linked to inflammatory and profibrotic responses. T. cruzi infection of HCoEpiC induces an increased expression of thrombospondin-1 (TSP-1), which is fibrogenic at elevated levels. We also found that T. cruzi infection modulates the expression of NF-kB and JAK2-STAT1 signaling molecules which can increase pro-inflammatory flux. Bioinformatics analysis of the phosphoprotein networks derived using the phospho-protein data serves as a blueprint for T. cruzi-mediated cellular transformation of primary human colonic cells during the early phase of T. cruzi infection.

CD100/Sema4D Increases Macrophage Infection by Leishmania (Leishmania) amazonensis in a CD72 Dependent Manner

Leishmaniasis is caused by trypanosomatid protozoa of the genus Leishmania, which infect preferentially macrophages. The disease affects 12 million people worldwide, who may present cutaneous, mucocutaneous or visceral forms. Several factors influence the form and severity of the disease, and the main ones are the Leishmania species and the host immune response. CD100 is a membrane bound protein that can also be shed. It was first identified in T lymphocytes and latter shown to be induced in macrophages by inflammatory stimuli. The soluble CD100 (sCD100) reduces migration and expression of inflammatory cytokines in human monocytes and dendritic cells, as well as the intake of oxidized low-density lipoprotein (oxLDL) by human macrophages. Considering the importance of macrophages in Leishmania infection and the potential role of sCD100 in the modulation of macrophage phagocytosis and activation, we analyzed the expression and distribution of CD100 in murine macrophages and the effects of sCD100 on macrophage infection by Leishmania (Leishmania) amazonensis. Here we show that CD100 expression in murine macrophages increases after infection with Leishmania. sCD100 augments infection and phagocytosis of Leishmania (L.) amazonensis promastigotes by macrophages, an effect dependent on macrophage CD72 receptor. Besides, sCD100 enhances phagocytosis of zymosan particles and infection by Trypanosoma cruzi.

Human leishmaniasis in Brazil: A general review

Leishmaniasis is a disease with ample clinical spectrum and epidemiological diversity and is considered a major public health problem. This article presents an overview of the transmission cycles, host-parasite interactions, clinical, histological and immunological aspects, diagnosis and treatment of various forms of the human disease.

Pentose Phosphate Shunt Modulates Reactive Oxygen Species and Nitric Oxide Production Controlling Trypanosoma cruzi in Macrophages

Metabolism provides substrates for reactive oxygen species (ROS) and nitric oxide (NO) generation, which are a part of the macrophage (Mφ) anti-microbial response. Mφs infected with Trypanosoma cruzi (Tc) produce insufficient levels of oxidative species and lower levels of glycolysis compared to classical Mφs. How Mφs fail to elicit a potent ROS/NO response during infection and its link to glycolysis is unknown. Herein, we evaluated for ROS, NO, and cytokine production in the presence of metabolic modulators of glycolysis and the Krebs cycle. Metabolic status was analyzed by Seahorse Flux Analyzer and mass spectrometry and validated by RNAi. Tc infection of RAW264.7 or bone marrow-derived Mφs elicited a substantial increase in peroxisome proliferator-activated receptor (PPAR)-α expression and pro-inflammatory cytokine release, and moderate levels of ROS/NO by 18 h. Interferon (IFN)-γ addition enhanced the Tc-induced ROS/NO release and shut down mitochondrial respiration to the levels noted in classical Mφs. Inhibition of PPAR-α attenuated the ROS/NO response and was insufficient for complete metabolic shift. Deprivation of glucose and inhibition of pyruvate transport showed that Krebs cycle and glycolysis support ROS/NO generation in Tc + IFN-γ stimulated Mφs. Metabolic profiling and RNAi studies showed that glycolysis-pentose phosphate pathway (PPP) at 6-phosphogluconate dehydrogenase was essential for ROS/NO response and control of parasite replication in Mφ. We conclude that IFN-γ, but not inhibition of PPAR-α, supports metabolic upregulation of glycolytic-PPP for eliciting potent ROS/NO response in Tc-infected Mφs. Chemical analogs enhancing the glucose-PPP will be beneficial in controlling Tc replication and dissemination by Mφs.

Evaluation of the adjuvant effect of agonists of toll-like receptor 4 and 7/8 in a vaccine against leishmaniasis in BALB/c mice

There is no effective vaccine against human leishmaniasis. Achieving successful vaccines seems to need powerful adjuvants. Separate or combined use of toll like receptor (TLR) agonists as adjuvant is a promising approach in Leishmania vaccine research. In present study, we evaluated adjuvant effect of separate or combined use of a TLR7/8 agonist, R848 and a TLR4 agonist, monophosphoryl lipid A (MPL) beside soluble Leishmania antigen (SLA) in BALB/c mice. Mice were vaccinated three times by SLA with separate or combined TLR7/8 and TLR4 agonists and were then challenged by Leishmania major. Delay type hypersensitivity, lesion development, parasite load, and cytokines (interferon gamma, and interleukin-10) response were assessed. Results showed: 1) MPL can slightly assist SLA in parasite load reduction, but it is not able to increase SLA ability in evoking DTH and cytokine responses or decreasing lesion diameter. 2) R848 does not affect the DTH response and parasite load of mice vaccinated with SLA, but it decreases/inhibits cytokine responses induced by SLA, leading to increase lesion diameter. 3) MPL neutralized inhibitory effect of R848. In overall, these data emphasize that MPL slightly assists SLA to make a more potent vaccine, but R848 is not a good adjuvant to induce T cell-dependent immune response in BALB/c mice, and therefore combination of these TLR agonists in the current formulation, is not recommended for making a more powerful adjuvant.

Development of a bead-agglutination assay for rapid detection of Tritrichomonas foetus

Tritrichomonas foetus is a flagellated protozoan parasite that causes inflammation of the reproductive tract leading to early embryonic death and abortion in cattle, thereby resulting in significant economic losses. Testing and culling infected bulls is an important strategy for parasite control. Routine testing is mainly limited to bulls that are traveling across state lines or within states that have specific control programs. Both culture and PCR detection methods are available, but they are not typically conducted as part of a yearly breeding soundness program and are not easily conducted in the field. In the present study, we developed a bead agglutination assay for detection of T. foetus antigens. Our experiments revealed that latex beads conjugated to T. foetus lipophosphoglycan-binding antibodies visibly clump in the presence of T. foetus. The detection limit of the assay, determined using both field and laboratory isolates of the parasite, was 0.25μg/mL and 1.0μg/mL total T. foetus antigen, respectively. Our results indicate that an antigen detection test could offer a tool for screening bulls under field conditions.

Ex vivo infection of human placental chorionic villi explants with Trypanosoma cruzi and Toxoplasma gondii induces different Toll-like receptor expression and cytokine/chemokine profiles

PROBLEM

Trypanosoma cruzi and Toxoplasma gondii present, respectively, low and high congenital transmission rates. The placenta as an immune regulatory organ expresses TLRs, leading to the secretion of cytokines. Both parasites are recognized by TLR-2, TLR-4, and TLR-9. Here, we studied if the parasites induce differences in TLR protein expression, cytokine profiles, and whether receptor inhibition is related to parasite infection.

METHOD OF STUDY

Placental tissue explants were infected ex vivo with each parasite, TLRs protein expression, cytokine profile and parasite infection were determined by Western blotting, ELISA and qPCR.

RESULTS

Trypanosoma cruzi and Toxoplasma gondii infection is related to TLR-2 and TLR-4/TLR-9, respectively. Trypanosoma cruzi elicits an increase in TNF-α, IL-1β, IL-6, IL-8 and IL-10 cytokine secretion whereas T. gondii only increases the secretion of IL-8.

CONCLUSION

The susceptibility of the placenta to each parasite is mediated partially by the innate immune response.