Role of eosinophils and neutrophils in innate and adaptive protective immunity to larval strongyloides stercoralis in mice

Dose-response effects of multiple Ascaris suum exposures and their impact on lung protection during larval ascariasis

BACKGROUND

Human ascariasis is the most prevalent geohelminthiasis worldwide, affecting approximately 446 million individuals. In regions with endemic prevalence, the majority of infected adults are frequently exposed to the parasite and tend to have a low parasite load. Further studies are necessary to provide more evidence on the dynamics of infection and to elucidate the possible mechanisms involved in regulating protection, especially during the acute phase, also known as larval ascariasis. The aim of this study is to compare the impact of lung function between single and multiple infections in a murine model.

METHODS

We infected BALB/c mice considering the frequency of exposures: single-exposure-SI; twice-exposures-RE 2x and thrice-exposures-RE 3x, and considering the doses of infection: 25 eggs-RE 25; 250 eggs-RE 250 and 2,500 eggs-RE 2500, followed by infection challenge with 2,500 eggs. From this, we evaluated: parasite burden in lungs, cellular and humoral response, histopathological and physiological alterations in lungs.

RESULTS

The main results showed a reduction of parasite burden in the reinfected groups compared to the single-infected group, with protection increasing with higher exposure and dose. Furthermore, the RE 250 group exhibited a decrease of parasite burden close to RE 2500, but with less tissue damage, displaying the most favorable prognosis among the reinfected groups.

CONCLUSION

Our research indicates a dose-dependent relationship between antibody production and the intensity of the immune response required to regulate the parasite burden.

ECRG4 mediates host response to cutaneous infection by regulating neutrophil recruitment and adhesion receptor expression

Rapid neutrophil recruitment is critical for controlling infection, with dysfunctional neutrophil responses in diseases like diabetes associated with greater morbidity and mortality. We have shown that the leukocyte protein ECRG4 enhances early neutrophil recruitment to cutaneous wounds and hypothesized that ECRG4 regulates the early host response to infection. Using a cutaneous infection model, we found that ECRG4 KO mice had decreased early neutrophil recruitment with persistent larger lesions, increased bacterial proliferation and systemic dissemination. Although previous work identified ECRG4 as a negative regulator of CD44 on neutrophils, the mechanism regulating neutrophil recruitment remained unknown. We demonstrated that pro-inflammatory responses were intact in ECRG4 KO mice, but found decreased neutrophil mobilization from bone marrow and decreased migration to chemokines. ECRG4 KO mouse neutrophils demonstrated an increase in adhesion molecules that regulate recruitment, including enhanced induction of integrin CD11b and increased L-selectin and CD44 on bone marrow neutrophils. Analysis of gene expression in leukocytes from diabetic patients found decreased ECRG4 expression with similar increased L-selectin and CD44. We propose a previously unrecognized mechanism governing neutrophil recruitment, whereby ECRG4 mediates neutrophil surface adhesion molecules that determine both recruitment and outside-in signaling that modulates neutrophil response to pro-inflammatory stimuli.

Eosinophils as drivers of bacterial immunomodulation and persistence

Traditionally, eosinophils have been linked to parasitic infections and pathological disease states. However, emerging literature has unveiled a more nuanced and intricate role for these cells, demonstrating their key functions in maintaining mucosal homeostasis. Eosinophils exhibit diverse phenotypes and exert multifaceted effects during infections, ranging from promoting pathogen persistence to triggering allergic reactions. Our investigations primarily focus on Bordetella spp., with particular emphasis on Bordetella bronchiseptica, a natural murine pathogen that induces diseases in mice akin to pertussis in humans. Recent findings from our published work have unveiled a striking interaction between B. bronchiseptica and eosinophils, facilitated by the btrS-mediated mechanism. This interaction serves to enhance pathogen persistence while concurrently delaying adaptive immune responses. Notably, this role of eosinophils is only noted in the absence of a functional btrS signaling pathway, indicating that wild-type B. bronchiseptica, and possibly other Bordetella spp., possess such adeptness in manipulating eosinophils that the true function of these cells remains obscured during infection. In this review, we present the mounting evidence pointing toward eosinophils as targets of bacterial exploitation, facilitating pathogen persistence and fostering chronic infections in diverse mucosal sites, including the lungs, gut, and skin. We underscore the pivotal role of the master regulator of Bordetella pathogenesis, the sigma factor BtrS, in orchestrating eosinophil-dependent immunomodulation within the context of pulmonary infection. These putative convergent strategies of targeting eosinophils offer promising avenues for the development of novel therapeutics targeting respiratory and other mucosal pathogens.

Neutrophils form extracellular traps in response to Opisthorchis viverrini crude antigens, which are elevated in neutrophils from opisthorchiasis patients with hepatobiliary abnormalities

Opisthorchis viverrini (Ov) infection can cause several disease conditions of the bile duct including hepatobiliary abnormalities (HBAs) and the most severe, cholangiocarcinoma (CCA). Fibrosis occurs when tissues are damaged and normal wound-healing responses are dysregulated. Neutrophils are the first cells to migrate to an infection site to protect the host from intruding extracellular pathogens through a wide range of effector mechanisms such as phagocytosis, production of reactive oxygen species, proteases, or release of neutrophil extracellular traps (NETs). In this work, we used confocal microscopy to assess whether Ov crude antigens can cause release of NETs from neutrophils from Ov-free individuals. We demonstrated for the first time that these antigens could induce release of NETs ex vivo in a dose-dependent manner from neutrophils isolated from Ov-free individuals. Intriguingly, when we measured NETs from neutrophils isolated from Ov-infected patients, we found increased spontaneous production of NETs in patients with HBAs. Interestingly, exposure to Ov crude antigens lowered the level of NETs released by neutrophils from patients with active Ov infection regardless of HBA status. We propose that in the case of acute Ov infection, even when concentration of Ov antigens is relatively low, neutrophils can form NETs. However, when this infection becomes chronic, manifesting as a definite HBA, the levels of NET production are reduced when treated with Ov crude antigens. Excessive production of proinflammatory mediators from these NETs might have effects on the parasites, but may also lead to excessive injury of surrounding tissues resulting in HBAs and may lead eventually to the most severe complications such as CCA.

Coinfection with Strongyloides and SARS-CoV-2: A Systematic Review

BACKGROUND

Treatments for COVID-19, including steroids, might exacerbate Strongyloides disease in patients with coinfection. We aimed to systematically review clinical and laboratory features of SARS-CoV-2 and Strongyloides coinfection, investigate possible interventions, assess outcomes, and identify research gaps requiring further attention.

METHODS

We searched two electronic databases, LitCOVID and WHO, up to August 2022, including SARS-CoV-2 and Strongyloides coinfection studies. We adapted the World Health Organization-Uppsala Monitoring Centre (WHO-UMC) system for standardized case causality assessment to evaluate if using corticosteroids or other immunosuppressive drugs in COVID-19 patients determined acute manifestations of strongyloidiasis.

RESULTS

We included 16 studies reporting 25 cases of Strongyloides and SARS-CoV-2 coinfection: 4 with hyperinfection syndrome; 2 with disseminated strongyloidiasis; 3 with cutaneous reactivation of strongyloidiasis; 3 with isolated digestive symptoms; and 2 with solely eosinophilia, without clinical manifestations. Eleven patients were asymptomatic regarding strongyloidiasis. Eosinopenia or normal eosinophil count was reported in 58.3% of patients with Strongyloides reactivation. Steroids were given to 18/21 (85.7%) cases. A total of 4 patients (19.1%) received tocilizumab and/or Anakirna in addition to steroids. Moreover, 2 patients (9.5%) did not receive any COVID-19 treatment. The causal relationship between Strongyloides reactivation and COVID-19 treatments was considered certain (4% of cases), probable (20% of patients), and possible (20% of patients). For 8% of cases, it was considered unlikely that COVID-19 treatment was associated with strongyloidiasis reactivations; the relationship between the Strongyloides infection and administration of COVID-19 treatment was unassessable/unclassifiable in 48% of cases. Of 13 assessable cases, 11 (84.6%) were considered to be causally associated with Strongyloides, ranging from certain to possible.

CONCLUSIONS

Further research is needed to assess the frequency and risk of Strongyloides reactivation in SARS-CoV-2 infection. Our limited data using causality assessment supports recommendations that clinicians should screen and treat for Strongyloides infection in patients with coinfection who receive immunosuppressive COVID-19 therapies. In addition, the male gender and older age (over 50 years) may be predisposing factors for Strongyloides reactivation. Standardized guidelines should be developed for reporting future research.

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.

Strongyloides stercoralis

Strongyloidiasis has been estimated to affect over 600 million people worldwide. It is caused by Strongyloides stercoralis, a roundworm endemic to the tropics and subtropics, especially areas where sanitation is suboptimal Autochthonous transmission has been documented in rural areas of the USA and Europe. Humans are infected when larvae penetrate the skin or are ingested. Autoinfection, in which larvae generated in the host go on to re-infect the host, leads to a state of chronic asymptomatic infection often with eosinophilia. Hyperinfection syndrome may develop when patients develop immune suppression, due to medications such as corticosteroids or following solid-organ transplantation. Hyperinfection is characterized by exponential increase in parasitic burden, leading to tissue invasion and life-threatening disease and associated bloodstream infections due to enteric organisms. Cases following use of corticosteroids for COVID-19 pneumonia have been described. Strongyloidiasis can be diagnosed by direct visualization of larvae in stool or other body fluids, or by serology. Ivermectin is highly effective in treating the disease. Patients with exposure to endemic areas and those expected to become immune suppressed should be screened and treated before starting immune suppressive agents. Empiric treatment should be considered when timely testing is not readily available.

ASCVac-1, a Multi-Peptide Chimeric Vaccine, Protects Mice Against Ascaris suum Infection

Control of human ascariasis, the most prevalent neglected tropical disease globally affecting 450 million people, mostly relies on mass drug administration of anthelmintics. However, chemotherapy alone is not efficient due to the high re-infection rate for people who live in the endemic area. The development of a vaccine that reduces the intensity of infection and maintains lower morbidity should be the primary target for infection control. Previously, our group demonstrated that immunization with crude Ascaris antigens in mice induced an IgG-mediated protective response with significant worm reduction. Here, we aimed to develop a multipeptide chimera vaccine based on conserved B-cell epitopes predicted from 17 common helminth proteomes using a bioinformatics algorithm. More than 480 B-cell epitopes were identified that are conserved in all 17 helminths. The Ascaris-specific epitopes were selected based on their reactivity to the pooled sera of mice immunized with Ascaris crude antigens or infected three times with A. suum infective eggs. The top 35 peptides with the strongest reactivity to Ascaris immune serum were selected to construct a chimeric antigen connected in sequence based on conformation. This chimera, called ASCVac-1, was produced as a soluble recombinant protein in an Escherichia coli expression system and, formulated with MPLA, was used to immunize mice. Mice immunized with ASCVac-1/MPLA showed around 50% reduced larvae production in the lungs after being challenged with A. suum infective eggs, along with significantly reduced inflammation and lung tissue/function damage. The reduced parasite count and pathology in infected lungs were associated with strong Th2 immune responses characterized by the high titers of antigen-specific IgG and its subclasses (IgG1, IgG2a, and IgG3) in the sera and significantly increased IL-4, IL-5, IL-13 levels in lung tissues. The reduced IL-33 titers and stimulated eosinophils were also observed in lung tissues and may also contribute to the ASCVac-1-induced protection. Taken together, the preclinical trial with ASCVac-1 chimera in a mouse model demonstrated its significant vaccine efficacy associated with strong IgG-based Th2 responses, without IgE induction, thus reducing the risk of an allergic response. All results suggest that the multiepitope-based ASCVac-1 chimera is a promising vaccine candidate against Ascaris sp. infections.

Lessons in type 2 immunity: Neutrophils in Helminth infections

Neutrophils constitute the body's first line of defense against invading pathogens. Equipped with a large array of tools, these immune cells are highly efficient in eliminating bacterial and viral infections, yet their activity can at the same time be detrimental to the host itself - this is the broad consensus on these granulocytes. However, the last decade has proven that neutrophils are a much more sophisticated cell type with unexpected and underappreciated functions in health and disease. In this review, we look at the latest discoveries in neutrophil biology with a focus on their role during the hallmark setting of type 2 immunity - helminth infection. We discuss the involvement of neutrophils in various helminth infection models and summarize the latest findings regarding neutrophil regulation and effector function. We will show that neutrophils have much more to offer than previously thought and while studies of neutrophils in helminth infections are still in its infancy, recent discoveries highlight more than ever that these cells are a key cog of the immune system, even during type 2 responses.

Eosinophils and Neutrophils Eliminate Migrating Strongyloides ratti Larvae at the Site of Infection in the Context of Extracellular DNA Trap Formation

Parasitic nematodes such as hookworms actively penetrate the skin of their hosts, encountering skin-resident innate immune cells that represent the host´s first line of defense. Here we use Strongyloides ratti as a model for an intestinal helminth parasite with tissue migrating stages. We show that interception and killing of migrating larvae in mice during a 1^st infection occurred predominantly in skin and muscle tissue before larvae migrated via lung and head tissue to the intestine. Inhibition of larval migration was even more efficient in immune mice during a 2^nd infection where larvae barely left the site of entry i.e. the foot. Using cell-deficient mice we show that interception in the tissue was predominantly mediated by neutrophils and eosinophils while basophils and mast cells were dispensable in vivo. Likewise, neutrophils and eosinophils inhibited S. ratti L3 motility in vitro in the context of ETosis. Thereby eosinophils were strictly dependent on the presence of anti-S. ratti antibodies while neutrophils inhibited L3 motility as such. Also, MPO and MMP-9 were released by neutrophils in response to L3 alone, but immune plasma further stimulated MPO release in an antibody-dependent manner. In summary, our findings highlight the central role of the skin as first line of defense against helminth parasites in both, innate and adaptive immunity.

Toxocara canis Infection Alters lncRNA and mRNA Expression Profiles of Dog Bone Marrow

Bone marrow is the main hematopoietic organ that produces red blood cells, granulocytes, monocyte/macrophages, megakaryocytes, lymphocytes, and myeloid dendritic cells. Many of these cells play roles in the pathogenesis of Toxocara canis infection, and understanding how infection alters the dynamics of transcription regulation in bone marrow is therefore critical for deciphering the global changes in the dog transcriptional signatures during T. canis infection. In this study, long non-coding RNA (lncRNA) and messenger RNA (mRNA) expression profiles in the bone marrow of Beagle dogs infected with T. canis were determined at 12 h post-infection (hpi), 24 hpi, 96 hpi, and 36 days post-infection (dpi). RNA-sequencing and bioinformatics analysis identified 1,098, 984, 1,120, and 1,305 differentially expressed lncRNAs (DElncRNAs), and 196, 253, 223, and 328 differentially expressed mRNAs (DEmRNAs) at 12 h, 24 h, 96 h, and 36 days after infection, respectively. We also identified 29, 36, 38, and 68 DEmRNAs potentially cis-regulated by 44, 44, 51, and 80 DElncRNAs at 12 hpi, 24 hpi, 96 hpi, and 36 dpi, respectively. To validate the sequencing findings, qRT-PCR was performed on 10 randomly selected transcripts. Many altered genes were involved in the differentiation of bone marrow cells. GO of DElncRNAs and GO and KEGG pathway analyses of DEmRNAs revealed alterations in several signaling pathways, including pathways involved in energy metabolism, amino acid biosynthesis and metabolism, Wnt signaling pathway, Huntington's disease, HIF-1 signaling pathway, cGMP–PKG signaling pathway, dilated cardiomyopathy, and adrenergic signaling in cardiomyocytes. These findings revealed that bone marrow of T. canis-infected dogs exhibits distinct lncRNA and mRNA expression patterns compared to healthy control dogs. Our data provide novel insights into T. canis interaction with the definitive host and shed light on the significance of the non-coding portion of the dog genome in the pathogenesis of toxocariasis.

Il4ra-independent vaginal eosinophil accumulation following helminth infection exacerbates epithelial ulcerative pathology of HSV-2 infection

How helminths influence the pathogenesis of sexually transmitted viral infections is not comprehensively understood. Here, we show that an acute helminth infection (Nippostrongylus brasiliensis [Nb]) induced a type 2 immune profile in the female genital tract (FGT). This leads to heightened epithelial ulceration and pathology in subsequent herpes simplex virus (HSV)-2 infection. This was IL-5-dependent but IL-4 receptor alpha (Il4ra) independent, associated with increased FGT eosinophils, raised vaginal IL-33, and enhanced epithelial necrosis. Vaginal eosinophil accumulation was promoted by IL-33 induction following targeted vaginal epithelium damage from a papain challenge. Inhibition of IL-33 protected against Nb-exacerbated HSV-2 pathology. Eosinophil depletion reduced IL-33 release and HSV-2 ulceration in Nb-infected mice. These findings demonstrate that Nb-initiated FGT eosinophil recruitment promotes an eosinophil, IL-33, and IL-5 inflammatory circuit that enhances vaginal epithelial necrosis and pathology following HSV-2 infection. These findings identify a mechanistic framework as to how helminth infections can exacerbate viral-induced vaginal pathology.

House dust mite sensitization drives cross-reactive immune responses to homologous helminth proteins

The establishment of type 2 responses driven by allergic sensitization prior to exposure to helminth parasites has demonstrated how tissue-specific responses can protect against migrating larval stages, but, as a consequence, allow for immune-mediated, parasite/allergy-associated morbidity. In this way, whether helminth cross-reacting allergen-specific antibodies are produced and play a role during the helminth infection, or exacerbate the allergic outcome awaits elucidation. Thus, the main objective of the study was to investigate whether house dust mite (HDM) sensitization triggers allergen-specific antibodies that interact with Ascaris antigens and mediate antibody-dependent deleterious effects on these parasites as well as, to assess the capacity of cross-reactive helminth proteins to trigger allergic inflammation in house dust mite presensitized mice. Here, we show that the sensitization with HDM-extract drives marked IgE and IgG1 antibody responses that cross-react with Ascaris larval antigens. Proteomic analysis of Ascaris larval antigens recognized by these HDM-specific antibodies identified Ascaris tropomyosin and enolase as the 2 major HDM homologues based on high sequence and structural similarity. Moreover, the helminth tropomyosin could drive Type-2 associated pulmonary inflammation similar to HDM following HDM tropomyosin sensitization. The HDM-triggered IgE cross-reactive antibodies were found to be functional as they mediated immediate hypersensitivity responses in skin testing. Finally, we demonstrated that HDM sensitization in either B cells or FcγRIII alpha-chain deficient mice indicated that the allergen driven cell-mediated larval killing is not antibody-dependent. Taken together, our data suggest that aeroallergen sensitization drives helminth reactive antibodies through molecular and structural similarity between HDM and Ascaris antigens suggesting that cross-reactive immune responses help drive allergic inflammation.

Epidemiological studies related to the interaction between allergies and helminth infection led to the observations that helped shape the so-called hygiene hypothesis, which generally states that chronic exposure to helminths diminishes the risk of the development of allergic disease. However, there are conflicting studies that have called this particular hypothesis into question, such as, the studies that suggest that infection with the helminth Ascaris lumbricoides is a risk factor for wheezing and atopy or can aggravate the clinical symptoms of asthma. A hypothetical explanation for such phenomenon is the fact that there is a high degree of molecular and structural similarities among helminth antigens with many common allergens, including the house dust mite (HDM). This high degree of homology of certain epitopes shared between helminths and allergens generate cross-react antibodies which may play a role in the pathogenesis or regulation of both conditions. Thus, this study aimed to understand the structural basis for cross-reactive antibodies induced by HDM sensitization. Here, we demonstrate that HDM sensitization drives helminth cross-reactive antibodies through molecular and structural homology between tropomyosins and enolases. This study highlights the pro-allergenic properties of HDM and helminth proteins that share homologous epitopes.

Clinical effectiveness of autohemotherapy as an adjuvant in the control of gastrointestinal nematodes in naturally infected sheep

Abstract This study aimed to evaluate the effects of autohemotherapy as an adjuvant in the control of gastrointestinal nematodes in sheep. Four experimental groups were formed: G1, 10 animals receiving autologous venous blood; G2, 10 animals receiving autologous venous blood and vermifuge containing levamisole; G3, 10 animals receiving only vermifuge containing levamisole; and G4, 10 animals as the control group receiving no treatment. We performed fecal egg count (eggs per gram, EPG) of strongyles, larval culture, hemogram, leukogram, and serum protein dosage prior to the start of treatment (D0), and on days 14 (D14) and 42 (D42). There was a significant decrease in the EPG of the groups receiving levamisole (G2 and G3) from D14 to the end of the experimental period. At the end of the evaluations, the mean EPG of G2 and G3 was significantly lower than that of G1 and G4. The most common nematode genus was Haemonchus (88%), and the least common was Trichostrongylus (1%). The Fecal Egg Count Reduction Test (FECRT) of G2 and G3 on D14 were 98.1% and 97.9%, respectively, however, in G1, the FECRT was zero on the two days when evaluation took place. G1 and G2 showed a significant increase in monocyte counts on D14 and D42. There was a significant increase in hematocrit and hemoglobin values in G2 and G3, however, a significant increase in the absolute value of red blood cells was observed only in G2. Two doses of autohemotherapy at 21-day intervals, administered alone or as an adjuvant to levamisole, is ineffective in controlling gastrointestinal nematodes in naturally infected sheep.

Systemic profile of immune factors in an elderly Italian population affected by chronic strongyloidiasis

Background

Strongyloidiasis caused by Strongyloides stercoralis is a soil-transmitted helminthiasis affecting an estimated 370 million people and considered one of the most neglected tropical diseases. Although mostly distributed in tropical and subtropical areas, autochthonous infections have also been documented in north-eastern Italy, even though the transmission presumably stopped decades ago. Because of its peculiar auto-infective cycle, strongyloidiasis can persist lifelong, but the pathophysiological mechanisms associated with the maintenance of such a chronic infection are yet to be fully deciphered.

Methods

Serum levels of 23 immune factors were retrospectively assessed in a subgroup of participants in a randomised clinical trial for the treatment of strongyloidiasis (Strong Treat). Here we included Italian subjects born between 1931 and 1964 and diagnosed with strongyloidiasis between 2013 and 2017 (Ss⁺, n = 32). Serum samples obtained before (BT) and 6 months (6M AT) after ivermectin treatment, as well as from age- and gender-matched uninfected controls (CTRL, n = 34) were analysed.

Results

The assessed immune factors showed a general reduced concertation in Ss⁺ patients and a lack of association with eosinophilia. In our cohort, we did not observe the classical shift towards a type 2 immune response, since Th1 and Th2 cytokines were mostly unaltered. Instead, we observed chemokines as particularly affected by the presence of the parasite, since IL-8, CCL3, CCL4 and CCL5 were significantly reduced in concentration in Ss⁺ subjects compared to CTRL, suggesting that immune cell recruitment to the infection site might be dampened in these patients. This observation was further sustained by a significant increase of CCL4, CCL5 and CCL11 concentrations 6M AT. A significant raised systemic concentration of three growth factors, bFGF, PDGF-BB and IL-7 (haematopoietic growth factor) was also observed post-treatment, indicating a potential involvement in restoring tissue integrity and homeostasis following parasite elimination.

Conclusions

These preliminary data suggest that, in order to survive for such a long period, S. stercoralis might suppress host responses that could otherwise result in its ejection. Our results offer novel insights in the potential mechanisms of disease tolerance that might take place during this chronic infection, including a potential T-cell hypo-responsiveness and a role for chemokines.

The effect of maternal Strongyloides venezuelensis infection on mice offspring susceptibility and immune response

Species of Strongyloides infect a wide range of hosts worldwide. Due to their complex life cycle, it is hard to control the transmission of these parasites. Several species show evidence of vertical transmission; however, the impact of this transmission route on the susceptibility of the offspring has been poorly investigated. Herein, we used Strongyloides venezuelensis infected mice to evaluate transplacental and transmammary parasite transmission and their effect on the susceptibility of offspring. Swiss female mice were infected at the end of the gestation or during the breastfeeding period, and their offspring were examined for the presence of the parasite one week after infection of the mother. Our data showed that female mice infected with S. venezuelensis during gestation did not transmit the parasite to their offspring. On the other hand, all newborn mice breastfeeding in S. venezuelensis infected females got infected. To evaluate the effect of early exposure to the parasite on susceptibility and immune response of the hosts, the offspring of each experimental group (non-infected, gestation-infected, and breastfeeding-infected mothers) received anti-helminth treatment after parasite evaluation and were subcutaneously infected with S. venezuelensis upon reaching adulthood. Mice from the group of breastfeeding-infected mothers showed lower susceptibility to S. venezuelensis in adulthood in comparison with mice from non-infected mothers. The low parasite burden was accompanied by earlier eosinophil and neutrophil activation in the gut and higher serum levels of IgE. In contrast, S. venezuelensis infection in adult mice born from gestation-infected mothers presented with more worms in the intestine and lower levels of parasite-reactive IgM in serum in comparison with mice born from non-infected mothers, thus suggesting that early exposure to parasite antigens may modulate the protective immune response. Altogether, our data confirmed transmammary, but not transplacental, transmission of S. venezuelensis in mice and demonstrated that early exposure to the parasite and/or their antigens has an important effect on host susceptibility to a later infection.

Characterization of IL-10-producing neutrophils in cattle infected with Ostertagia ostertagi

IL-10 is a master regulator of immune responses, but its cellular source and function in cattle during the initial phase of immune priming have not been well established. Despite a massive B cell response in the abomasal draining lymph nodes in Ostertagia ostertagi (OO)-infected cattle, protective immunity is slow to develop, and partial protection requires years of repeated exposure. In addressing this problem, our initial hypothesis was that B cells produce IL-10 that downregulates the host protective immune response. However, our results showed that neutrophils made up the majority of IL-10-producing cells in circulation and in secondary lymphoid tissues, particularly the spleen (80%). Conversely, IL-10-producing B cells were rare. In addition, approximately 10% to 20% of the neutrophils in the blood and spleen expressed MHC II and were IL-10 negative, suggesting that neutrophils could also participate in antigen presentation. In vitro investigation of bovine neutrophils revealed that exposure thereof to OO extract increased IL-10 and MHC II expression in these cells in a dose-dependent manner, consistent with IL-10+/MHC II+ neutrophils detected in cattle shortly after experimental OO infection. Co-culture of untreated neutrophils with anti-CD3 antibody (Ab)-stimulated CD4+ T cells led to enhanced T cell activation; also, IL-10 depletion with neutralizing Ab enhanced the stimulatory function of neutrophils. OO extract depressed neutrophil stimulation of CD4+ T cells in the presence of IL-10-neutralizing Ab, suggesting that OO utilizes both IL-10-dependent and independent mechanisms to manipulate the bovine immune response. Finally, contact and viability were required for T cell-stimulatory neutrophil function. This report, to the best of our knowledge, is the first to demonstrate that neutrophil-derived IL-10 is directly involved in T cell regulation in cattle. Our data suggest that neutrophils and neutrophil-derived IL-10 are co-opted by nematode parasites and other pathogens to attenuate host immune responses and facilitate pathogen survival.

A Dual Role for Macrophages in Modulating Lung Tissue Damage/Repair during L2 Toxocara canis Infection

Macrophages that are classically activated (M1) through the IFN-γ/STAT1 signaling pathway have a major role in mediating inflammation during microbial and parasitic infections. In some cases, unregulated inflammation induces tissue damage. In helminth infections, alternatively activated macrophages (M2), whose activation occurs mainly via the IL-4/STAT6 pathway, have a major role in mediating protection against excessive inflammation, and has been associated with both tissue repair and parasite clearance. During the lung migratory stage of Toxocara canis, the roles of M1 and M2 macrophages in tissue repair remain unknown. To assess this, we orally infected wild-type (WT) and STAT1 and STAT6-deficient mice (STAT1^-/- and STAT6^-/-) with L2 T. canis, and evaluated the role of M1 or M2 macrophages in lung pathology. The absence of STAT1 favored an M2 activation pattern with Arg1, FIZZ1, and Ym1 expression, which resulted in parasite resistance and lung tissue repair. In contrast, the absence of STAT6 induced M1 activation and iNOS expression, which helped control parasitic infection but generated increased inflammation and lung pathology. Next, macrophages were depleted by intratracheally inoculating mice with clodronate-loaded liposomes. We found a significant reduction in alveolar macrophages that was associated with higher lung pathology in both WT and STAT1^-/- mice; in contrast, STAT6^-/- mice receiving clodronate-liposomes displayed less tissue damage, indicating critical roles of both macrophage phenotypes in lung pathology and tissue repair. Therefore, a proper balance between inflammatory and anti-inflammatory responses during T. canis infection is necessary to limit lung pathology and favor lung healing.

Host-directed therapies for parasitic diseases

Parasitic infections are responsible for significant morbidity and mortality throughout the world. Management strategies rely primarily on antiparasitic drugs that have side effects and risk of drug resistance. Therefore, novel strategies are needed for treatment of parasitic infections. Host-directed therapy (HDT) is a viable alternative, which targets host pathways responsible for parasite invasion/survival/pathogenicity. Recent innovative combinations of genomics, proteomics and computational biology approaches have led to discovery of several host pathways that could be promising targets for HDT for treating parasitic infections. Herein, we review major advances in HDT for parasitic disease with regard to core regulatory pathways and their interactions.

Allergen presensitization drives an eosinophil-dependent arrest in lung-specific helminth development

This study investigates the relationship between helminth infection and allergic sensitization by assessing the influence of preexisting allergy on the outcome of helminth infections, rather than the more traditional approach in which the helminth infection precedes the onset of allergy. Here we used a murine model of house dust mite-induced (HDM-induced) allergic inflammation followed by Ascaris infection to demonstrate that allergic sensitization drives an eosinophil-rich pulmonary type 2 immune response (Th2 cells, M2 macrophages, type 2 innate lymphoid cells, IL-33, IL-4, IL-13, and mucus) that directly hinders larval development and reduces markedly the parasite burden in the lungs. This effect is dependent on the presence of eosinophils, as eosinophil-deficient mice were unable to limit parasite development or numbers. In vivo administration of neutralizing antibodies against CD4 prior to HDM sensitization significantly reduced eosinophils in the lungs, resulting in the reversal of the HDM-induced Ascaris larval killing. Our data suggest that HDM allergic sensitization drives a response that mimics a primary Ascaris infection, such that CD4+ Th2-mediated eosinophil-dependent helminth larval killing in the lung tissue occurs. This study provides insight into the mechanisms underlying tissue-specific responses that drive a protective response against the early stages of the helminths prior to their establishing long-lasting infections in the host.

Regulatory T cells and IgE expression in duodenal mucosa of Strongyloides stercoralis and human T lymphotropic virus type 1 co-infected patients

Background

Strongyloides stercoralis is an intestinal nematode unique in its ability to replicate in the human host, allowing ongoing cycles of autoinfection, persisting for decades within the same host. Although usually asymptomatic, overwhelming infections can occur in Strongyloides and HTLV-1 co-infected individuals (SS/HTLV-1). Regulatory T cells (Tregs) are able to blunt specific Th2 responses necessary to control the parasite. We previously reported that peripheral blood Tregs are increased in SS/HTLV-1 and correlate with low Th2 responses. We hypothesized that Tregs are also increased at the site of infection in duodenal mucosa.

Methods

Paraffin embedded duodenal biopsies were obtained from 10 SS/HTLV-1 patients, 3 controls with non-parasitic chronic duodenitis, and 2 healthy controls. Immunohistochemistry was performed using monoclonal antibodies against human CD3, CD8, IgE and FoxP3. The number of cells were counted using a conventional light microscope. The number of CD3+, CD8+, FoxP3+ and IgE positive cells per 0.35 mm² was measured using ImagePro Plus software comparing areas adjacent or distant from parasite material.

Results

In patients with SS/HTLV-1, T lymphocyte counts and CD8+ cells were lower in areas adjacent to the parasite compared to non-adjacent areas (CD3+: adjacent: 6.5 [Interquartile range (IQR: 2.8–12.3)]; non-adjacent: 24.5 [IQR: 20.9–34.4]; Mann-Whitney p = 0.0003; CD8+: adjacent: 4.5 [IQR: 2.3–11.8]; non-adjacent: 21 [IQR: 15.3–42.9]; Mann-Whitney p = 0.0011). Tregs cells in the intestines (FoxP3+ expressing cells) were increased in patients with SS/HTLV-1 compared with patients with chronic duodenitis (SS/HTLV-1: 1.5 [IQR: 0.7–2.3]; duodenitis controls: 0 [range 0–0.7]; healthy controls: 0; Mann-Whitney p = 0.034). There was also a trend towards fewer eosinophils adjacent to the parasites. Among SS/HTLV-1 patients the number of IgE expressing cells was increased for in areas not adjacent to the parasite compared to non-adjacent areas (ANOVA, p = 0.001).

Conclusions

Our data shows increased Treg cell numbers localized adjacent to the parasites in the duodenum SS/HTLV-1 patients. In addition, other T lymphocytes and IgE expressing cells were decreased adjacent to the parasites, suggesting an important role for Tregs in down-regulating local parasite effector responses.

Strongyloidiasis is a parasitic infection found worldwide in warm, moist climates. In most people, Strongyloides causes a mild and chronic infection with few symptoms. However, some patients, including those infected with the Human T Lymphotrophic Virus 1 (HTLV-1), can get uncontrolled disease called hyperinfection, which can be fatal. To help determine why this infection is so serious in co-infected patients, we studied biopsies obtained from the small intestine from patients with both infections and compared them to control biopsies. The biopsies from patients with both Strongyloides and HTLV-1 had increased numbers of white blood cells in their biopsies. In particular they displayed a type of lymphocyte that downregulates immune responses. Some of them had increased numbers of cells called eosinophils in the intestines. These cells can help eliminate Strongyloides. However, they were not found near the parasite, suggesting that something near the parasite was suppressing the host response that would control infection. These studies provide more evidence that HTLV-1 suppresses the host response that controls Strongyloides and that the suppression occurs at the site of infection in the small intestines.

Strongyloides stercoralis hyperinfection syndrome: a deeper understanding of a neglected disease

Strongyloides stercoralis hyperinfection syndrome (SHS) is a life-threatening condition that warrants early detection and management. We describe the pathogenesis, organ-specific clinical manifestations, and risk factors associated to this condition. A comprehensive review of the literature was conducted in PubMed, LILACS, EBSCO and SciELO by using the keywords: "hyperinfection syndrome"; "Strongyloides stercoralis"; "disseminated strongyloidiasis"; "systemic strongyloidiasis", "pathogenesis" and "pathophysiology". Relevant articles on this topic were evaluated and included by consensus. Also, a secondary search of the literature was performed. Articles in English and Spanish language were included. SHS has been described in tropical and sub-tropical regions. However, there is growing evidence of cases detected in developed countries favored by increasing migration and the advance in immunosuppressive therapies for oncologic and inflammatory diseases. SHS is characterized by massive multiplication of larvae, typically in immunocompromised hosts. Clinical manifestations vary according to the organ involved and include diarrhea, intestinal bleeding, alveolar hemorrhages, heart failure, jaundice, bacteremia among others. Despite advances in the understanding of this condition, fatality rates are near 90%. Clinicians should consider SHS in the differential diagnosis of acutely ill patients with multiple organ damage and epidemiological risk factors. Adverse outcomes are common, especially with delayed anti-parasitic treatment.

The state of art of neutrophil extracellular traps in protozoan and helminthic infections

Neutrophil extracellular traps (NETs) are DNA fibers associated with histones, enzymes from neutrophil granules and anti-microbial peptides. NETs are released in a process denominated NETosis, which involves sequential steps that culminate with the DNA extrusion. NETosis has been described as a new mechanism of innate immunity related to defense against different pathogens. The initial studies of NETs were carried out with bacteria and fungi, but currently a large variety of microorganisms capable of inducing NETs have been described including protozoan and helminth parasites. Nevertheless, we have little knowledge about how NETosis process is carried out in response to the parasites, and about its implication in the resolution of this kind of disease. In the best case, the NETs entrap and kill parasites in vitro, but in others, immobilize the parasites without affecting their viability. Moreover, insufficient studies on the NETs in animal models of infections that would help to define their role, and the association of NETs with chronic inflammatory pathologies such as those occurring in several parasitic infections have left open the possibility of NETs contributing to pathology instead of protection. In this review, we focus on the reported mechanisms that lead to NET release by protozoan and helminth parasites and the evidence that support the role of NETosis in the resolution or pathogenesis of parasitic diseases.

Development of Onchocerca volvulus in humanized NSG mice and detection of parasite biomarkers in urine and serum

BACKGROUND

The study of Onchocerca volvulus has been limited by its host range, with only humans and non-human primates shown to be susceptible to the full life cycle infection. Small animal models that support the development of adult parasites have not been identified.

METHODOLOGY/PRINCIPAL FINDINGS

We hypothesized that highly immunodeficient NSG mice would support the survival and maturation of O. volvulus and alteration of the host microenvironment through the addition of various human cells and tissues would further enhance the level of parasite maturation. NSG mice were humanized with: (1) umbilical cord derived CD34+ stem cells, (2) fetal derived liver, thymus and CD34+ stem cells or (3) primary human skeletal muscle cells. NSG and humanized NSG mice were infected with 100 O. volvulus infective larvae (L3) for 4 to 12 weeks. When necropsies of infected animals were performed, it was observed that parasites survived and developed throughout the infection time course. In each of the different humanized mouse models, worms matured from L3 to advanced fourth stage larvae, with both male and female organ development. In addition, worms increased in length by up to 4-fold. Serum and urine, collected from humanized mice for identification of potential biomarkers of infection, allowed for the identification of 10 O. volvulus-derived proteins found specifically in either the urine or the serum of the humanized O. volvulus-infected NSG mice.

CONCLUSIONS/SIGNIFICANCE

The newly identified mouse models for onchocerciasis will enable the development of O. volvulus specific biomarkers, screening for new therapeutic approaches and potentially studying the human immune response to infection with O. volvulus.

Bovine neutrophils form extracellular traps in response to the gastrointestinal parasite Ostertagia ostertagi

Ostertagia ostertagi (OO) is a widespread parasite that causes chronic infection in cattle and leads to annual losses of billions of dollars in the cattle industry. It remains unclear why cattle are unable to mount an effective immune response despite a large influx of immune cells to the infected abomasal mucosa and draining lymph nodes. Neutrophils, the immune system’s first responders, have the capacity to release neutrophil extracellular traps (NETs) to contain various pathogens, including some parasites. In the present study, the mechanisms by which O. ostertagi influences bovine NET formation were investigated. O. ostertagi larval soluble extract (OO extract) was able to induce typical NETs by purified neutrophils in vitro, confirmed by co-localization of extracellular DNA with typical NET-associated proteins histone and neutrophil elastase (NE). Consistent with existing literature, inhibition assays demonstrated that these OO extract-induced NETs were dependent upon the enzymes NADPH oxidase and myeloperoxidase (MPO). Live OO stage 4 larvae (L4) stimulated neutrophils to form NETs similar to those induced by OO extract. Bovine neutrophils also released NETs in response to Caenorhabditis elegans, a free-living soil nematode, suggesting that bovine NET production may be a conserved mechanism against a broad range of nematodes. This is the first report demonstrating O. ostertagi-induced NET formation by bovine neutrophils, a potentially underappreciated mechanism in the early immune response against nematode infections.

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.

Ovine vital neutrophil extracellular traps bind and impair Haemonchus contortus L3 in a breed-dependent manner

This study aimed to characterize neutrophil response to Haemonchus contortus (Hc) in vitro using cells from parasite-resistant St. Croix (STC) and parasite-susceptible Suffolk (SUF) sheep. Neutrophils from Hc-primed and naive STC and SUF sheep were incubated with Hc larval antigen (HcLA), Hc worm antigen (HcWA) or complete media (CM). After HcLA exposure, neutrophils from STC and SUF formed extracellular traps composed of DNA. Stimulation with HcLA induced a 35-fold increase in extracellular DNA compared to CM controls. However, extracellular DNA was not found when neutrophils were cultured with HcWA. The formation of neutrophil extracellular traps (NET) in response to HcLA yields a low percentage of necrotic cells indicating a form of vital NETosis. Neutrophils from primed and naïve STC bound Hc L3 greater (93% and 68%) than SUF (78% and 45%; P < 0.001). Furthermore, STC neutrophils significantly reduced larval ATP levels compared to SUF neutrophils (0.05 μmol/L vs 0.1 μmol/L ATP, P < 0.001). These data indicate that ovine neutrophils bind, form vital NET and reduce ATP to Hc L3 in a breed and infection status-dependent manner.

Elevated Systemic Levels of Eosinophil, Neutrophil, and Mast Cell Granular Proteins in Strongyloides Stercoralis Infection that Diminish following Treatment

Infection with the helminth parasite Strongyloides stercoralis (Ss) is commonly clinically asymptomatic that is often accompanied by peripheral eosinophilia. Granulocytes are activated during helminth infection and can act as immune effector cells. Plasma levels of eosinophil and neutrophil granular proteins convey an indirect measure of granulocyte degranulation and are prominently augmented in numerous helminth-infected patients. In this study, we sought to examine the levels of eosinophil, neutrophil, and mast cell activation-associated granule proteins in asymptomatic Ss infection and to understand their kinetics following anthelmintic therapy. To this end, we measured the plasma levels of eosinophil cationic protein, eosinophil-derived neurotoxin, eosinophil peroxidase, eosinophil major basic protein, neutrophil elastase, myeloperoxidase, neutrophil proteinase-3, mast cell tryptase, leukotriene C4, and mast cell carboxypeptidase-A3 in individuals with asymptomatic Ss infection or without Ss infection [uninfected (UN)]. We also estimated the levels of all of these analytes in infected individuals following definitive treatment of Ss infection. We demonstrated that those infected individuals have significantly enhanced plasma levels of eosinophil cationic protein, eosinophil-derived neurotoxin, eosinophil peroxidase, eosinophil major basic protein, elastase, myeloperoxidase, mast cell tryptase, leukotriene C4, and carboxypeptidase-A3 compared to UN individuals. Following the treatment of Ss infection, each of these granulocyte-associated proteins drops significantly. Our data suggest that eosinophil, neutrophil, and mast cell activation may play a role in the response to Ss infection.

Eosinophils from Physiology to Disease: A Comprehensive Review

Despite being the second least represented granulocyte subpopulation in the circulating blood, eosinophils are receiving a growing interest from the scientific community, due to their complex pathophysiological role in a broad range of local and systemic inflammatory diseases as well as in cancer and thrombosis. Eosinophils are crucial for the control of parasitic infections, but increasing evidence suggests that they are also involved in vital defensive tasks against bacterial and viral pathogens including HIV. On the other side of the coin, eosinophil potential to provide a strong defensive response against invading microbes through the release of a large array of compounds can prove toxic to the host tissues and dysregulate haemostasis. Increasing knowledge of eosinophil biological behaviour is leading to major changes in established paradigms for the classification and diagnosis of several allergic and autoimmune diseases and has paved the way to a "golden age" of eosinophil-targeted agents. In this review, we provide a comprehensive update on the pathophysiological role of eosinophils in host defence, inflammation, and cancer and discuss potential clinical implications in light of recent therapeutic advances.

Methylprednisolone acetate induces, and Δ7-dafachronic acid suppresses, Strongyloides stercoralis hyperinfection in NSG mice

Strongyloides stercoralis hyperinfection causes high mortality rates in humans, and, while hyperinfection can be induced by immunosuppressive glucocorticoids, the pathogenesis remains unknown. Since immunocompetent mice are resistant to infection with S. stercoralis, we hypothesized that NSG mice, which have a reduced innate immune response and lack adaptive immunity, would be susceptible to the infection and develop hyperinfection. Interestingly, despite the presence of large numbers of adult and first-stage larvae in S. stercoralis-infected NSG mice, no hyperinfection was observed even when the mice were treated with a monoclonal antibody to eliminate residual granulocyte activity. NSG mice were then infected with third-stage larvae and treated for 6 wk with methylprednisolone acetate (MPA), a synthetic glucocorticoid. MPA treatment of infected mice resulted in 50% mortality and caused a significant >10-fold increase in the number of parasitic female worms compared with infected untreated mice. In addition, autoinfective third-stage larvae, which initiate hyperinfection, were found in high numbers in MPA-treated, but not untreated, mice. Remarkably, treatment with Δ7-dafachronic acid, an agonist of the parasite nuclear receptor Ss-DAF-12, significantly reduced the worm burden in MPA-treated mice undergoing hyperinfection with S. stercoralis Overall, this study provides a useful mouse model for S. stercoralis autoinfection and suggests a therapeutic strategy for treating lethal hyperinfection.

Mycoleptodonoides aitchisonii suppresses asthma via Th2 and Th1 cell regulation in an ovalbumin‑induced asthma mouse model

Asthma is a chronic respiratory disease related to hyper‑responsiveness. The majority of patients suffer mild symptoms, however, some cases, especially in the young and the elderly, can lead to death by apnea. Mycoleptodonoides atichisonii (M. atichisonii) is an edible mushroom that has previously been reported to possess several bioactive properties, such as the synthesis of nerve growth factors, anti‑obesity effects and the ability to prevent cell death. In the current study, the authors evaluated the anti‑asthmatic effects of M. atichisonii using an ovalbumin‑induced asthma mouse model. M. atichisonii dose‑dependently suppressed the levels of white blood cells, eosinophils and immunoglobulin (Ig)E in BALB/c mice, resulting from ovalbumin‑induced asthma. M. atichisonii recovered the typical asthmatic morphological changes in lungs, such as mucous hyper‑secretion, epithelial layer hyperplasia, eosinophil infiltration and various cell surface molecules, such as CD3, CD4, CD8, CD19 and major histocompatibility complex class II. With the exception of CD19+ cells and IL‑12p40, M. atichisonii affected almost all factors related to asthma induction including the T helper (Th)1/Th2 transcription factors, T‑bet and GATA‑3, Th1‑related cytokines, Th2‑related cytokines and proinflammatory cytokines. In addition, M. atichisonii significantly inhibited the expression of IL‑5, IL‑13 and IL‑6. The authors concluded that M. atichisonii may be a promising drug candidate against asthma.

Anisakis - immunology of a foodborne parasitosis

Anisakis species are marine nematodes which can cause zoonotic infection in humans if consumed in raw, pickled or undercooked fish and seafood. Infection with Anisakis is associated with abdominal pain, nausea and diarrhoea and can lead to massive infiltration of eosinophils and formation of granulomas in the gastrointestinal tract if the larvae are not removed. Re-infection leads to systemic allergic reactions such as urticarial or anaphylaxis in some individuals, making Anisakis an important source of hidden allergens in seafood. This review summarizes the immunopathology associated with Anisakis infection. Anisakiasis and gastroallergic reactions can be prevented by consuming only fish that has been frozen to -20°C to the core for at least 24 hours before preparation. Sensitization to Anisakis proteins can also occur, primarily due to occupational exposure to infested fish, and can lead to dermatitis, rhinoconjunctivitis or asthma. In this case, exposure to fish should be avoided.

Oral contraceptive pills: Risky or protective in case of Trichinella spiralis infection?

The aim of this study was to investigate how Trichinella spiralis infection can be affected by contraceptive pills in vivo. Methods included six groups of female Wistar rats; healthy, Trichinella infected, receiving combined contraceptive pills (COCPs), receiving progestin only pills (POPs), infected receiving COCPs and infected receiving POPs. Parasite burden was measured; adult worm counts, gravidity, larvae and reproductive capacity index). Histopathological examination, immunohistochemical detection of C-kit+ mast cells and Foxp3+ T-reg. cells in intestinal sections, eosinophils muscle infiltration and CPK level were performed. Rats infected and receiving COCPs showed a significant increase in parasitic burden, and infected receiving POPs showed a significant reduction compared to infected only, with a significant increase in nongravid females (Mean total worms=964.40±55.9, 742±52.63, 686±31.68, larvae/g=5030±198.75, 2490±143.18 and 4126±152,91, respectively). Intestinal sections from infected receiving COCPs showed intact mucosa (though the high inflammatory cells infiltrate), and significant increase in C-kit+ mast cells number and intensity (30.20±4.15 and 60.40±8.29), and Foxp3+ T-reg. cells (10±1.58). Infected receiving POPs showed a significantly less CPK (5886±574.40) and eosinophilic muscle infiltration (58±13.51). Oestrogen-containing pills established a favourable intestinal environment for Trichinella by enhancing Foxp+T-reg. cells and stabilizing C-kit+mast cells, while POPs gave a potential protection with less gravidity, larval burden and eosinophilic infiltrate.

Different Lymphocyte Populations Direct Dichotomous Eosinophil or Neutrophil Responses to Pulmonary Cryptococcus Infection

Many pulmonary infections elicit lymphocyte responses that lead to an accumulation of granulocytes in the lungs. A variety of lymphocytes are capable of directing eosinophils or neutrophils to the lungs, but the contribution of each subset remains enigmatic. In this study, we used a murine model to examine lymphocyte subsets that ultimately drive the eosinophil or neutrophil response to infection with the fungal pathogen Cryptococcus neoformans. We show that granulocytes are produced in the bone marrow, released into the blood stream, and accumulate in the lungs under the instruction of lung parenchymal lymphocytes. The eosinophils that populated the lungs of wild-type animals were highly dependent on Th cells or IL-5. Surprisingly, infected mice with Th cell impairment experienced a compensatory neutrophil response that required IL-17A. This unexpected swing in the response prompted us to investigate the ability of different lymphocyte subsets to produce this dichotomous eosinophilia or neutrophilia. We used mice with lymphocyte deficiencies to determine which of the remaining IL-5- or IL-17A-producing lymphocyte subsets dominated the neutrophil or eosinophil response. Finally, skewing the response toward neutrophil-inducing lymphocytes correlated with accelerated disease. Our data collectively demonstrate that the predominance of a lymphocyte subset determines the functional consequences of an immune response to pulmonary fungal infection that can ultimately affect disease.

Strongyloides hyperinfection following hematopoietic stem cell transplant in a patient with HTLV-1-associated T-cell leukemia

Strongyloides stercoralis has the potential to cause accelerated autoinfection in immunocompromised hosts. Screening tests for strongyloidiasis may be falsely negative in the setting of immunosuppression. We report a case of Strongyloides hyperinfection syndrome in a patient with human T-lymphotropic virus type 1-associated T-cell leukemia early after hematopoietic stem cell transplant. The diagnosis was made by stool ova and parasite examination, despite a negative screening enzyme-linked immunosorbent assay. Because of anticipated prolonged neutropenia, an extended course of treatment was utilized.

Allergic Sensitization Underlies Hyperreactive Antigen-Specific CD4+ T Cell Responses in Coincident Filarial Infection

Among the various hypotheses put forward to explain the modulatory influence of helminth infection on allergic effector responses in humans, the IL-10-induced suppression of Th2-associated responses has been the leading candidate. To explore this helminth/allergy interaction more fully, parasite- and allergen-specific CD4(+) T cell responses in 12 subjects with filarial infections, and coincident allergic sensitization (filarial [Fil](+)allergy [A](+)) were compared with the responses to three appropriate control groups (Fil(-)A(-) [n = 13], Fil(-)A(+) [n = 12], Fil(+)A(-) [n = 11]). The most important findings revealed that Fil(+)A(+) had marked (p < 0.0001 for all cytokines) increases in parasite Ag-driven Th2 (IL-4, IL-5, IL-13), Th9 (IL-9), and the regulatory (IL-10) cytokines when compared with Fil(+)A(-) Moreover, using multiparameter flow cytometry, filarial parasite Ag induced a marked increase in not only the frequency of CD4(+) T cells producing IL-4, IL-5, IL-2, and TNF-α in Fil(+)A(+) when compared with Fil(+)A(-) patients, but also in the frequencies of polyfunctional Th2-like (CD4(+)IL-4(+)IL-5(+) and CD4(+)IL-2(+)IL-4(+)IL-5(+)TNF-α(+)) cells. The Th2-associated responses seen in the Fil(+)A(+) group were correlated with serum IgE levels (p < 0.01, r = 0.5165 for IL-4; p < 0.001, r = 0.5544 for IL-5; and p < 0.001, r = 0.4901 for IL-13) and levels of circulating eosinophils (p < 0.0116, r = 0.5656) and their degranulation/activation products (major basic protein [p < 0.001, r = 0.7353] and eosinophil-derived neurotoxin [p < 0.01, r = 0.7059]). CD4(+) responses to allergen were not different (to a large extent) among the groups. Taken together, our data suggest that allergic sensitization coincident with filarial infection drives parasite Ag-specific T cell hyperresponsiveness, which is characterized largely by an augmented Th2-dominated immune response.

Role of Macrophages in the Repair Process during the Tissue Migrating and Resident Helminth Infections

The Th1/Th2/Th17 balance is a fundamental feature in the regulation of the inflammatory microenvironment during helminth infections, and an imbalance in this paradigm greatly contributes to inflammatory disorders. In some cases of helminthiasis, an initial Th1 response could occur during the early phases of infection (acute), followed by a Th2 response that prevails in chronic infections. During the late phase of infection, alternatively activated macrophages (AAMs) are important to counteract the inflammation caused by the Th1/Th17 response and larval migration, limiting damage and repairing the tissue affected. Macrophages are the archetype of phagocytic cells, with the primary role of pathogen destruction and antigen presentation. Nevertheless, other subtypes of macrophages have been described with important roles in tissue repair and immune regulation. These types of macrophages challenge the classical view of macrophages activated by an inflammatory response. The role of these subtypes of macrophages during helminthiasis is a controversial topic in immunoparasitology. Here, we analyze some of the studies regarding the role of AAMs in tissue repair during the tissue migration of helminths.

A Fatal Strongyloides Stercoralis Hyperinfection Syndrome in a Patient With Chronic kidney Disease: A Case Report and Literature Review

Strongyloides stercoralis hyperinfection syndrome is a rare but fatal disease, which occurs commonly in immunocompromised patients. Strongyloidiasis among patients with chronic kidney disease is rarely reported.A 55-year-old Chinese male presented to hospital with diarrhea and abdominal pain. He developed acute respiratory failure and progressed to diffuse alveolar hemorrhage owing to disseminated strongyloidiasis immediately. The bronchoalveolar lavage revealed filariform larvae of Strongyloides stercoralis.This patient was diagnosed with Strongyloides hyperinfection syndrome. Although albendazole, mechanical ventilator support, fluid resuscitation, vasopressor support, extracorporeal membrane oxygenation, hydrocortisone, and broadspectrum antimicrobials were actively used, the patient eventually died.Similar cases in patients with chronic kidney disease in the literature are also reviewed. Through literature review, we recommend that strongyloidiasis should be routinely investigated in patients with chronic kidney disease who will undergo immunosuppressive therapy.

Neutropenic Mice Provide Insight into the Role of Skin-Infiltrating Neutrophils in the Host Protective Immunity against Filarial Infective Larvae

Our knowledge and control of the pathogenesis induced by the filariae remain limited due to experimental obstacles presented by parasitic nematode biology and the lack of selective prophylactic or curative drugs. Here we thought to investigate the role of neutrophils in the host innate immune response to the infection caused by the Litomosoides sigmodontis murine model of human filariasis using mice harboring a gain-of-function mutation of the chemokine receptor CXCR4 and characterized by a profound blood neutropenia (Cxcr4^+/1013). We provided manifold evidence emphasizing the major role of neutrophils in the control of the early stages of infection occurring in the skin. Firstly, we uncovered that the filarial parasitic success was dramatically decreased in Cxcr4^+/1013 mice upon subcutaneous delivery of the infective stages of filariae (infective larvae, L3). This protection was linked to a larger number of neutrophils constitutively present in the skin of the mutant mice herein characterized as compared to wild type (wt) mice. Indeed, the parasitic success in Cxcr4^+/1013 mice was normalized either upon depleting neutrophils, including the pool in the skin, or bypassing the skin via the intravenous infection of L3. Second, extending these observations to wt mice we found that subcutaneous delivery of L3 elicited an increase of neutrophils in the skin. Finally, living L3 larvae were able to promote in both wt and mutant mice, an oxidative burst response and the release of neutrophil extracellular traps (NET). This response of neutrophils, which is adapted to the large size of the L3 infective stages, likely directly contributes to the anti-parasitic strategies implemented by the host. Collectively, our results are demonstrating the contribution of neutrophils in early anti-filarial host responses through their capacity to undertake different anti-filarial strategies such as oxidative burst, degranulation and NETosis.

Filariases are chronic debilitating diseases caused by parasitic nematodes affecting more than 150 million people worldwide. None of the current drugs are selective, neither able to eliminate the parasites nor to prevent new infections once the drug pressure has waned. Therefore, blocking the entry and the migration of the infective larvae (L3) could be an efficient way to control the infection. In the present study we investigated the early interaction between the host and the L. sigmodontis murine filariasis with a focus on the neutrophils in the innate host responses. We uncovered a key role of neutrophils in the control of infection provided by the CXCR4-gain-of-function mice (Cxcr4^+/1013) that display a blood neutropenia as well as an accumulation of skin-infiltrating neutrophils. Overall, we reveal that in the early phase of filariasis, i.e. after L3 are delivered into the skin and before they reach their site for reproduction, neutrophils are critical elements of the host innate protective response arsenal. A better understanding of their indirect and/or effector role(s) may provide mechanistic clues to host factors implicated in parasitic nematode entry and potentially lead to the identification of new drug targets.

Strongyloides infection in rodents: immune response and immune regulation

The human pathogenic nematode Strongyloides stercoralis infects approximately 30-100 million people worldwide. Analysis of the adaptive immune response to S. stercoralis beyond descriptive studies is challenging, as no murine model for the complete infection cycle is available. However, the combined employment of different models each capable of modelling some features of S. stercoralis life cycle and pathology has advanced our understanding of the immunological mechanisms involved in host defence. Here we review: (i) studies using S. stercoralis third stage larvae implanted in diffusion chambers in the subcutaneous tissue of mice that allow analysis of the immune response to the human pathogenic Strongyloides species; (ii) studies using Strongyloides ratti and Strongyloides venezuelensis that infect mice and rats to extend the analysis to the parasites intestinal life stage and (iii) studies using S. stercoralis infected gerbils to analyse the hyperinfection syndrome, a severe complication of human strongyloidiasis that is not induced by rodent specific Strongyloides spp. We provide an overview of the information accumulated so far showing that Strongyloides spp. elicits a classical Th2 response that culminates in different, site specific, effector functions leading to either entrapment and killing of larvae in the tissues or expulsion of parasitic adults from the intestine.

Association between Strongyloides stercoralis infection and cortisol secretion in alcoholic patients

A higher prevalence of Strongyloides stercoralis infections has been reported in alcoholic patients compared to nonalcoholic patients living in the same area. Excessive alcohol consumption increases the levels of endogenous corticosteroids that subsequently enhance the fecundity of S. stercoralis parthenogenetic females. These corticosteroids also enhance the transformation of rhabditiform larvae into infective filariform larvae by mimicking the effect of the ecdysteroid hormones produced by the parasite, thus leading to autoinfection. In addition, alterations in the intestinal barrier and host immune response contribute to the development of hyperinfection and severe strongyloidiasis in alcoholic patients. The aim of this study was to evaluate the frequency of S. stercoralis infections in alcoholic patients and to determine the association between S. stercoralis infection and endogenous cortisol levels. The frequency of infection was evaluated in 332 alcoholic and 92 nonalcoholic patients. The parasitological diagnosis was carried out by agar plate culture, the modified Baermann-Moraes method and spontaneous sedimentation. The immunological diagnosis was performed using an ELISA with anti-S. stercoralis IgG. The cortisol levels were measured in serum samples by ELISA. The frequency of S. stercoralis infection in alcoholic patients was 23.5% (78/332), while in nonalcoholic patients, it was 5.4% (5/92) (p<0.05). The cortisol levels were higher in alcoholic than in nonalcoholic patients (p<0.05). However, among the alcoholic patients, the cortisol levels did not differ between S. stercoralis-infected and uninfected patients (p>0.05). As demonstrated in this work, 81.3% (26/32) of patients with a high parasite load, considered as more than 11 larvae per gram of feces, presented serum cortisol levels above the normal reference value (24 mg/dL). High endogenous cortisol levels in alcoholic patients were not associated to susceptibility to S. stercoralis infection, however once infected, this may lead to a high parasite load.

Strongyloides stercoralis Infection in Alcoholic Patients

The course of Strongyloides stercoralis infection is usually asymptomatic with a low discharge of rhabditoid larva in feces. However, the deleterious effects of alcohol consumption seem to enhance the susceptibility to infection, as shown by a fivefold higher strongyloidiasis frequency in alcoholics than in nonalcoholics. Moreover, the association between S. stercoralis infection and alcoholism presents a risk for hyperinfection and severe strongyloidiasis. There are several possible mechanisms for the disruption of the host-parasite equilibrium in ethanol-addicted patients with chronic strongyloidiasis. One explanation is that chronic ethanol intake stimulates the hypothalamic-pituitary-adrenal (HPA) axis to produce excessive levels of endogenous cortisol, which in turn can lead to a deficiency in type 2 T helper cells (Th2) protective response, and also to mimic the parasite hormone ecdysone, which promotes the transformation of rhabditiform larvae to filariform larvae, leading to autoinfection. Therefore, when untreated, alcoholic patients are continuously infected by this autoinfection mechanism. Thus, the early diagnosis of strongyloidiasis and treatment can prevent serious forms of hyperinfection in ethanol abusers.

Systemic Cytokine Profiles in Strongyloides stercoralis Infection and Alterations following Treatment

Strongyloides stercoralis is a soil-transmitted helminth organism that infects ~50 to 100 million people worldwide. Despite its widespread prevalence, very little is known about the immune response that characterizes human S. stercoralis infection. To study the systemic cytokine profile characteristic of Strongyloides infection, we measured the circulating levels of a large panel of pro- and anti-inflammatory cytokines in asymptomatic, infected individuals (n = 32) and compared them to those in uninfected, controls (n = 24). Infected individuals exhibited significantly lower circulating levels of proinflammatory cytokines (gamma interferon [IFN-γ], tumor necrosis factor alpha [TNF-α], and interleukin-1β [IL-1β]) and significantly higher levels of anti-inflammatory cytokines (IL-4, IL-5, IL-9, IL-10, IL-13, IL-27, IL-37, and transforming growth factor β [TGF-β]). Moreover, treatment of Strongyloides infection resulted in a significant reversal of the cytokine profile, with increased levels of proinflammatory (IFN-γ, TNF-α, IL-2, IL-17A, IL-17F, IL-22, IL-23, and IL-1β) and decreased levels of anti-inflammatory (IL-4, IL-5, IL-9, IL-10, IL-13, IL-27, IL-37, and TGF-β) cytokines following treatment. Thus, S. stercoralis infection is characterized by alterations in the levels of systemic cytokines, reflecting major alterations in the underlying immune response to this chronic helminth infection.

Immunogenicity and Protective Efficacy of Brugia malayi Heavy Chain Myosin as Homologous DNA, Protein and Heterologous DNA/Protein Prime Boost Vaccine in Rodent Model

We earlier demonstrated the immunoprophylactic efficacy of recombinant heavy chain myosin (Bm-Myo) of Brugia malayi (B. malayi) in rodent models. In the current study, further attempts have been made to improve this efficacy by employing alternate approaches such as homologous DNA (pcD-Myo) and heterologous DNA/protein prime boost (pcD-Myo+Bm-Myo) in BALB/c mouse model. The gene bm-myo was cloned in a mammalian expression vector pcDNA 3.1(+) and protein expression was confirmed in mammalian Vero cell line. A significant degree of protection (79.2%±2.32) against L3 challenge in pcD-Myo+Bm-Myo immunized group was observed which was much higher than that exerted by Bm-Myo (66.6%±2.23) and pcD-Myo (41.6%±2.45). In the heterologous immunized group, the percentage of peritoneal leukocytes such as macrophages, neutrophils, B cells and T cells marginally increased and their population augmented further significantly following L3 challenge. pcD-Myo+Bm-Myo immunization elicited robust cellular and humoral immune responses as compared to pcD-Myo and Bm-Myo groups as evidenced by an increased accumulation of CD4+, CD8+ T cells and CD19+ B cells in the mouse spleen and activation of peritoneal macrophages. Though immunized animals produced antigen-specific IgG antibodies and isotypes, sera of mice receiving pcD-Myo+Bm-Myo or Bm-Myo developed much higher antibody levels than other groups and there was profound antibody-dependent cellular adhesion and cytotoxicity (ADCC) to B. malayi infective larvae (L3). pcD-Myo+Bm-Myo as well as Bm-Myo mice generated a mixed T helper cell phenotype as evidenced by the production of both pro-inflammatory (IL-2, IFN-γ) and anti-inflammatory (IL-4, IL-10) cytokines. Mice receiving pcD-Myo on contrary displayed a polarized pro-inflammatory immune response. The findings suggest that the priming of animals with DNA followed by protein booster generates heightened and mixed pro- and anti-inflammatory immune responses that are capable of providing high degree of protection against filarial larval invasion.

Immunoblotting using Strongyloides venezuelensis larvae, parthenogenetic females or eggs extracts for the diagnosis of experimentally infected immunosuppressed rats

The nematode Strongyloides stercoralis is responsible for strongyloidiasis in humans. Diagnosis of infection occurs through detection of larvae in feces, but low elimination of larvae often hampers the detection of disease, particularly in cases of patient immunosuppression. Immunodiagnostic tests have been developed; however obtaining S. stercoralis larvae for the production of homologous antigen extract is technically difficult. Thus, the use different developmental forms of Strongyloides venezuelensis has become an alternative method for the production of antigen extracts. The aim of this study was to evaluate immunoblotting using alkaline extracts from S. venezuelensis L3 larvae, parthenogenetic females or eggs to test detection of experimental strongyloidiasis associated with immunosuppression. Immunocompetent and immunosuppressed male rats were experimentally infected, and serum sample from all animals were obtained at 0, 5, 8 13, and 21 days post infection (d.p.i.). Immunoblotting was evaluated for use in detection of anti-S. venezuelensis IgG in both experimental rat groups. The larval extract immunoblotting profile had the most immunoreactive fractions in the immunosuppressed group beginning at 5 d.p.i., while the immunocompetent group reactivity began on 8 d.p.i. Immunoreactive protein fractions of 17 kDa present in larval alkaline extract presented as possible markers of infection in immunosuppressed rats. It is concluded that all extracts using immunoblotting have diagnostic potential in experimental strongyloidiasis, particularly larval extract in immunosuppressed individuals.

Strongyloides stercoralis hyperinfection syndrome: a case series and a review of the literature

BACKGROUND

Strongyloides stercoralis may lead to overwhelming infestation [Strongyloides hyperinfection syndrome (SHS)]. We aimed at describing a case series of patients admitted in intensive care unit (ICU) with SHS and report a literature review of such cases.

PATIENTS AND METHODS

Retrospective multicenter study of 11 patients admitted to the ICU of tertiary hospitals with SHS between 2000 and 2013. Literature review with Pubmed retrieved 122 cases. Logistic regression analysis was performed to identify predictive factors of ICU mortality and shock occurrence.

RESULTS

133 patients [median age 53 (39, 64), 72.2 % males] were included. Underlying immunosuppression was present in 127 patients, mostly long-term corticosteroid treatment in 111 (83.5 %) patients. Fever (80.8 %), respiratory (88.6 %), and gastrointestinal (71.2 %) symptoms were common clinical manifestations. Shock occurred in 75 (57.3 %) patients and mechanical ventilation was required in 89 (67.9 %) patients. Hypereosinophilia and a concomitant bacterial infection were observed in 34 (34.3 %) and 51 (38.4 %) patients, respectively. The in-ICU mortality rate was 60.3 %. Predictive factors of ICU mortality were shock occurrence [Odds ratio (OR) 18.1, 95 % confidence interval (95 % CI) 3.03-107.6, p < 0.01] and mechanical ventilation (OR 28.1, 95 % CI 3.6-217, p < 0.01). Hypereosinophilia (OR 0.21, 95 % CI 0.06-0.7, p = 0.01) and a concomitant bacterial infection (OR 4.68, 95 % CI 1.3-16.8, p = 0.02) were independent predictors of shock occurrence.

CONCLUSION

SHS remains associated with a poor outcome, especially when associated with shock and mechanical ventilation. Deterioration to shock is often related to concomitant bacterial infection. The poor outcome of established SHS pleads for a large application of antiparasitic primary prophylaxis in at-risk patients.

The Role of Reactive Oxygen Species (ROS) in the Formation of Extracellular Traps (ETs) in Humans

Extracellular traps (ETs) are reticulate structures of extracellular DNA associated with antimicrobial molecules. Their formation by phagocytes (mainly by neutrophils: NETs) has been identified as an essential element of vertebrate innate immune defense. However, as ETs are also toxic to host cells and potent triggers of autoimmunity, their role between pathogen defense and human pathogenesis is ambiguous, and they contribute to a variety of acute and chronic inflammatory diseases. Since the discovery of ET formation (ETosis) a decade ago, evidence has accumulated that most reaction cascades leading to ET release involve ROS. An important new facet was added when it became apparent that ETosis might be directly linked to, or be a variant of, the autophagy cell death pathway. The present review analyzes the evidence to date on the interplay between ROS, autophagy and ETosis, and highlights and discusses several further aspects of the ROS-ET relationship that are incompletely understood. These aspects include the role of NADPH oxidase-derived ROS, the molecular requirements of NADPH oxidase-dependent ETosis, the roles of NADPH oxidase subtypes, extracellular ROS and of ROS from sources other than NADPH oxidase, and the present evidence for ROS-independent ETosis. We conclude that ROS interact with ETosis in a multidimensional manner, with influence on whether ETosis shows beneficial or detrimental effects.

Strongyloidiasis with emphasis on human infections and its different clinical forms

Strongyloidiasis (caused by Strongyloides stercoralis, and to a lesser extent by Strongyloides fuelleborni) is one of the most neglected tropical diseases with endemic areas and affecting more than 100 million people worldwide. Chronic infections in endemic areas can be maintained for decades through the autoinfective cycle with the L3 filariform larvae. In these endemic areas, misdiagnosis, inadequate treatment and the facilitation of the hyperinfection syndrome by immunosuppression are frequent and contribute to a high mortality rate. Despite the serious health impact of strongyloidiasis, it is a neglected disease and very little is known about this parasite and the disease when compared to other helminth infections. Control of the disease is difficult because of the many gaps in our knowledge of strongyloidiasis. We examine the recent literature on different aspects of strongyloidiasis with emphasis in those aspects that need further research.