Eosinophils participate in modulation of liver immune response and tissue damage induced by Schistosoma mansoni infection in mice.

The severity of chronic schistosomiasis has been mainly associated with the intensity and extension of the inflammatory response induced by egg-secreted antigens in the host tissue, especially in the liver and intestine. During acute schistosomiasis, eosinophils account for approximately 50% of the cells that compose the liver granulomas; however, the role of this cell-type in the pathology of schistosomiasis remains controversial. In the current study, we compared the parasite burden and liver immunopathological changes during experimental schistosomiasis in wild-type (WT) BALB/c mice and BALB/c mice selectively deficient for the differentiation of eosinophils (ΔdblGATA). Our data demonstrated that the absence of eosinophil differentiation did not alter the S. mansoni load or the liver retention of parasite eggs; however, there were significant changes in the liver immune response profile and tissue damage. S. mansoni infection in ΔdblGATA mice resulted in significantly lower liver concentrations of IL-5, IL-13, IL-33, IL-17, IL-10, and TGF-ß and higher concentrations of IFN-γ and TNF-α, as compared to WT mice. The changes in liver immune response observed in infected ΔdblGATA mice were accompanied by lower collagen deposition, but higher liver damage and larger granulomas. Moreover, the absence of eosinophils resulted in a higher mortality rate in mice infected with a high parasite load. Therefore, the data indicated that eosinophils participate in the establishment and/or amplification of liver Th-2 and regulatory response induced by S. mansoni, which is necessary for the balance between liver damage and fibrosis, which in turn is essential for modulating disease severity.

Tumor suppressor p53 regulates intestinal type 2 immunity.

The role of p53 in tumor suppression has been extensively studied and well-established. However, the role of p53 in parasitic infections and the intestinal type 2 immunity is unclear. Here, we report that p53 is crucial for intestinal type 2 immunity in response to the infection of parasites, such as Tritrichomonas muris and Nippostrongylus brasiliensis. Mechanistically, p53 plays a critical role in the activation of the tuft cell-IL-25-type 2 innate lymphoid cell circuit, partly via transcriptional regulation of Lrmp in tuft cells. Lrmp modulates Ca2+ influx and IL-25 release, which are critical triggers of type 2 innate lymphoid cell response. Our results thus reveal a previously unrecognized function of p53 in regulating intestinal type 2 immunity to protect against parasitic infections, highlighting the role of p53 as a guardian of immune integrity.

Galectin-Receptor Interactions Regulates Cardiac Pathology Caused by Trichinella spiralis Infection.

The parasitic nematode Trichinella spiralis causes trichinellosis, a serious food-borne parasitic zoonosis worldwide. Infection with T. spiralis may also cause myocarditis. In the present study, we used mouse models to assess the impact of blockage of galectin-receptor interactions by α-lactose on cardiac immunopathology during acute T. spiralis experimental infection. Our data demonstrated that, after T. spiralis infection, blockage of galectin-receptor interactions resulted in cardiac dysfunction detected by transthoracic conventional echocardiography, and increased serum Gal-3 level, a biomarker of myocardial damage. In addition, there were increased eosinophil number in peripheral blood, and increased eosinophil infiltration in the heart and spleen tissues accompanied with increased mRNA levels of eosinophil granule proteins (including eosinophil cationic protein (ECP) and eosinophil peroxidase (EPO)) and IL-5 in these organs; increased cardiac fibrosis accompanied with increased Gal-3 and collagen 1 expressions in the hearts of mice with blockage of galectin-receptor interactions after T. spiralis infection. Correlation analysis showed that significant positive correlations existed between the mRNA levels of Gal-3 and ECP/EPO/eosinophil major basic protein/IL-5/CCL11/CCR3/α-SMA/collagen 1 in the hearts of both T. spiralis-infected mice and T. spiralis-infected mice with blockage of galectin-receptor interactions. Our data suggest that galectin-receptor interactions play a pivotal role during acute T. spiralis infection, and lack of galectin-receptor interactions upregulates Gal-3 which, in turn, leads to elevated heart eosinophil recruitment, exacerbated heart pathology and fibrosis, and heart functional damage.

Natural resistance to worms exacerbates bovine tuberculosis severity independently of worm coinfection.

Pathogen interactions arising during coinfection can exacerbate disease severity, for example when the immune response mounted against one pathogen negatively affects defense of another. It is also possible that host immune responses to a pathogen, shaped by historical evolutionary interactions between host and pathogen, may modify host immune defenses in ways that have repercussions for other pathogens. In this case, negative interactions between two pathogens could emerge even in the absence of concurrent infection. Parasitic worms and tuberculosis (TB) are involved in one of the most geographically extensive of pathogen interactions, and during coinfection worms can exacerbate TB disease outcomes. Here, we show that in a wild mammal natural resistance to worms affects bovine tuberculosis (BTB) severity independently of active worm infection. We found that worm-resistant individuals were more likely to die of BTB than were nonresistant individuals, and their disease progressed more quickly. Anthelmintic treatment moderated, but did not eliminate, the resistance effect, and the effects of resistance and treatment were opposite and additive, with untreated, resistant individuals experiencing the highest mortality. Furthermore, resistance and anthelmintic treatment had nonoverlapping effects on BTB pathology. The effects of resistance manifested in the lungs (the primary site of BTB infection), while the effects of treatment manifested almost entirely in the lymph nodes (the site of disseminated disease), suggesting that resistance and active worm infection affect BTB progression via distinct mechanisms. Our findings reveal that interactions between pathogens can occur as a consequence of processes arising on very different timescales.

Follicular helper T cells recruit eosinophils into host liver by producing CXCL12 during Schistosoma japonicum infection.

Schistosomiasis affects at least 200 million people in tropical and subtropical areas. The major pathology of schistosomiasis is egg-induced liver granuloma characterized by an eosinophil-rich inflammatory infiltration around the eggs, which subsequently leads to hepatic fibrosis and circulatory impairment in host. However, the mechanisms how eosinophils are recruited into the liver, which are crucial for the better understanding of the mechanisms underlying granuloma formation and control of schistosomiasis, remain unclear. In this study, we showed that follicular helper T (Tfh) cells participate in recruitment of eosinophils into liver partially by producing CXCL12 during schistosome infection. Our findings uncovered a previously unappreciated role of Tfh cells in promotion of the development of liver granuloma in schistosomiasis, making Tfh-CXCL12-eosinophil axis a potential target for intervention of schistosomiasis.

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.

IL-17A neutralizing antibody attenuates eosinophilic meningitis caused by Angiostrongylus cantonensis by involving IL-17RA/Traf6/NF-κB signaling.

BACKGROUND: Angiostrongylus cantonensis (A. cantonensis) is a foodborne parasite that can invade the central nervous system (CNS), resulting in eosinophilic meningitis (EM). However, the mechanism by which A. cantonensis causes eosinophilic infiltration into CNS is not well understood. METHODS: In this study eosinophilic infiltration into the CNS caused by A. cantonensis was assessed based on eosinophil counts and evaluation of interleukin (IL)-5 and -13 levels by real-time PCR in brain of Balb/c mice. The expression and activation of IL-17A, IL17 receptor (IL-17R A), and IL-17RC and the related signaling molecules nuclear factor (NF)-κB1, NF-κB2, NF-κB activator (Act)1, tumor necrosis factor receptor-associated factor (Traf)5, and Traf6 during A. cantonensis infection in brain tissue of Balb/c mice were examined by real-time, western blotting and immunofluroence. A. cantonensis-infected Balb/c mice were treated with IL-17A neutralizing antibody to evaluate the role of IL17A in eosinophil accumulation in the CNS. RESULTS: Our results showed A. cantonensis infection caused eosinophil accumulation and alterations in IL-5 and -13 levels. The expression of IL-17A and -17RA, Act1, and Traf6 but not of IL-17RC and Traf5 was upregulated during infection; this was accompanied by NF-κB1 and -κB2 activation. Importantly, application of IL-17A neutralizing antibody attenuated eosinophil accumulation in CNS and reversed the changes in IL-5 and -13 expression caused by A. cantonensis infection. Additionally, IL-17RA and Traf6 levels decreased, which was accompanied by NF-κB inactivation. CONCLUSION: IL-17A plays an important role in EM caused by A. cantonensis, possibly through activation of NF-κB via the IL-17RA/Traf6 signaling pathway. These findings highlight the potential for using IL-17A neutralizing antibody as a therapeutic strategy for the treatment of EM.

Eosinophils and Macrophages within the Th2-Induced Granuloma: Balancing Killing and Healing in a Tight Space.

Granuloma formation is a key host immune response generated to confine invading pathogens and limit extensive host damage. It consists of an accumulation of host immune cells around a pathogen. This host response has been extensively studied in the context of inflammatory diseases. However, there is much less known about Th2-type granulomas generated in response to parasitic worms. Based on in vitro data, innate immune cells within the granuloma are thought to immobilize and kill parasites but also act to repair damaged tissue. Understanding this dual function is key. The two billion people and many livestock/wild animals infected with helminths demonstrate that granulomas are not effective at clearing infection. However, the lack of high mortality highlights their importance in ensuring that parasite migration/tissue damage is restricted and wound healing is effective. In this review, we define two key cellular players (macrophages and eosinophils) and their associated molecular players involved in Th2 granuloma function. To date, the underlying mechanisms remain poorly understood, which is in part due to a lack of conclusive studies. Most have been performed in vitro rather than in vivo, using cells that have not been obtained from granulomas. Experiments using genetically modified mouse strains and/or antibody/chemical-mediated cell depletion have also generated conflicting results depending on the model. We discuss the caveats of previous studies and the new tools available that will help fill the gaps in our knowledge and allow a better understanding of the balance between immune killing and healing.

Eosinophilic cerebrospinal fluid pleocytosis associated with neural Angiostrongylus vasorum infection in a dog.

A 1-year-old, female intact Pug dog was presented to the Small Animal Teaching Hospital of the University of Liverpool with a 4-week history of progressive multifocal intracranial signs. Magnetic resonance imaging (MRI) detected multiple hemorrhagic lesions in the brain. The Baermann and zinc sulfate flotation tests with centrifugation, performed on fecal samples, were positive for lungworm larvae and an antigenic test confirmed Angiostrongylus vasorum infection. Anthelmintic treatment was started with a consequent marked clinical improvement. Seventy days later, the dog was clinically normal, and no larvae were detected on the Baermann test. Repeat MRI of the brain revealed marked improvement of the hemorrhagic lesions. Cerebrospinal fluid analysis (CSF) showed marked eosinophilic pleocytosis, and anthelmintic treatment was restarted. A follow-up CSF analysis 4 months after the first presentation revealed resolution of the eosinophilic pleocytosis. This is the first case report of marked eosinophilic pleocytosis associated with neural A vasorum infection in a dog. The CSF eosinophilic pleocytosis persisted for several weeks after treatment, even in the absence of concurrent clinical signs and with a negative A vasorum Baermann test.

CXCR6+ST2+ memory T helper 2 cells induced the expression of major basic protein in eosinophils to reduce the fecundity of helminth.

Memory T helper (mTh) cells play important roles in the reinfection of pathogens and drive the pathogenesis of diseases. While recent studies have characterized the pathogenic mTh2 cell subpopulations driving allergic inflammation, those that induce immune responses against helminth infection remain unknown. We found that IL-5-producing CXCR6+ST2+CD44+ mTh2 cells play a crucial role in the IL-33-dependent inhibition of the fecundity of helminth, whereas other ST2- mTh2 cells do not. Although both cell types induced the infiltration of granulocytes, especially eosinophils, into the lungs in response to helminth infection, the ST2+ mTh2 cell-induced eosinophils expressed higher levels of major basic protein (MBP), which is important for reducing the fecundity of Nippostrongylus brasiliensis (Nb), than ST2- mTh2 cell-induced ones. Notably, we also found that ST2+ Treg cells but not ST2- Treg cells suppressed CXCR6+ST2+ mTh2 cell-mediated immune responses. Taken together, these findings show that we identified a mechanism against helminth elicited by a subpopulation of IL-5-producing mTh2 cells through the accumulation of eosinophils strongly expressing MBP in the lungs.

Larva migrans cutánea. A propósito de un caso clínico / Cutaneous larva migrans. A case report

No disponible

Endomyocardial involvement in asymptomatic sub-Saharan immigrants with helminth-related eosinophilia.

BACKGROUND: Among immigrants of sub-Saharan origin, parasitic infection is the leading cause of eosinophilia, which is generally interpreted as a defense mechanism. A side effect of the inflammatory mediators released by eosinophils is damage to host organs, especially the heart. The main objectives of this study were to i) assess cardiac involvement in asymptomatic sub-Saharan immigrants with eosinophilia, ii) relate the presence of lesions with the degree of eosinophilia, and iii) study the relationship between cardiac involvement and the type of causative parasite. METHODOLOGY/PRINCIPLE FINDINGS: In total, the study included 50 black immigrants (37 patients and 13 controls) from sub-Saharan Africa. In all subjects, heart structure and function were evaluated in a blinded manner using Sonos 5500 echocardiographic equipment. The findings were classified and described according to established criteria. The diagnostic criteria for helminthosis were those reported in the literature. Serum eosinophil-derived neurotoxin levels were measured using enzyme-linked immunosorbent assay. A significant association was found between the presence of eosinophilia and structural alterations (mitral valve thickening). However, the lack of an association between the degree of eosinophilia and heart valve disease and the absence of valve involvement in some patients with eosinophilia suggest the role of other factors in the appearance of endocardial lesions. There was also no association between the type of helminth and valve involvement. CONCLUSIONS: We, therefore, suggest that transthoracic echocardiography be performed in every sub-Saharan individual with eosinophilia in order to rule out early heart valve lesions.

Modulation of Haemonchus contortus infection by depletion of γδ+ T cells in parasite resistant Canaria Hair Breed sheep.

Canaria Hair Breed (CHB) sheep display resistance against the adult stage of the nematode, Haemonchus contortus. Previous studies have suggested significant correlations between γδ+ T lymphocytes and fecundity of female adult worms, suggesting a novel role in immune modulation by these cells. The largest proportion of γδ+ T lymphocytes in sheep are the subpopulation of γδ+/WC1+ T cells. The aim of this study was to evaluate the effect of γδ+/WC1+ T cell depletion via infusion of anti-γδ/WC1 monoclonal antibody (mAb) on the subsequent immune response of CHB sheep infected with H. contortus. Significantly lower γδ+ T cell levels in both peripheral blood and in the basal layers of the abomasal tissue resulted following anti-γδ/WC1 mAb infusion of CHB sheep compared to control animals. Worms recovered from the anti-γδ/WC1 mAb treated CHB sheep had significantly longer female worms with correspondingly more eggs in utero than the saline control group. Significant correlations between eosinophils and worm length and fecundity were no longer apparent in the anti-γδ/WC1 mAb treated CHB sheep. These results support the notion that γδ+ T cells in CHB sheep play a critical role in fecundity regulation (length and eggs in utero) of H. contortus adult female worms, and highlights a new mechanism of modulation by this lymphocyte population, possibly involving eosinophil activation.

Eosinophils are required to suppress Th2 responses in Peyer's patches during intestinal infection by nematodes.

Infections with enteric nematodes result in systemic type 2 helper T (Th2) responses, expansion of immunoglobulin (Ig)G1 antibodies, and eosinophilia. Eosinophils have a supportive role in mucosal Th2 induction during airway hyperreactivity. Whether eosinophils affect the local T-cell and antibody response in the gut-associated lymphoid tissue during enteric infections is unknown. We infected eosinophil-deficient ΔdblGATA-1 mice with the Th2-inducing small intestinal nematode Heligmosomoides polygyrus and found that parasite fecundity was decreased in the absence of eosinophils. A lack of eosinophils resulted in significantly augmented expression of GATA-3 and IL-4 by CD4+ T cells during acute infection, a finding strictly limited to Peyer's patches (PP). The increase in IL-4-producing cells in ΔdblGATA-1 mice was particularly evident within the CXCR5+PD-1+ T-follicular helper cell population and was associated with a switch of germinal centre B cells to IgG1 production and elevated serum IgG1 levels. In contrast, infected wild-type mice had a modest IgG1 response in the PP, whereas successfully maintaining a population of IgA+ germinal center B cells. Our results suggest a novel role for eosinophils during intestinal infection whereby they restrict IL-4 responses by follicular T helper cells and IgG1 class switching in the PP to ensure maintenance of local IgA production.

Eosinophils in Helminth Infection: Defenders and Dupes.

Eosinophilia is a central feature of the host response to helminth infection. Larval stages of parasitic worms are killed in vitro by eosinophils in the presence of specific antibodies or complement. These findings established host defense as the paradigm for eosinophil function. Recently, studies in eosinophil-ablated mouse strains have revealed an expanded repertoire of immunoregulatory functions for this cell. Other reports document crucial roles for eosinophils in tissue homeostasis and metabolism, processes that are central to the establishment and maintenance of parasitic worms in their hosts. In this review, we summarize current understanding of the significance of eosinophils at the host-parasite interface, highlighting their distinct functions during primary and secondary exposure.

Eosinophils may play regionally disparate roles in influencing IgA(+) plasma cell numbers during large and small intestinal inflammation.

BACKGROUND: Eosinophils are innate immune cells present in the intestine during steady state conditions. An intestinal eosinophilia is a hallmark of many infections and an accumulation of eosinophils is also observed in the intestine during inflammatory disorders. Classically the function of eosinophils has been associated with tissue destruction, due to the release of cytotoxic granule contents. However, recent evidence has demonstrated that the eosinophil plays a more diverse role in the immune system than previously acknowledged, including shaping adaptive immune responses and providing plasma cell survival factors during the steady state. Importantly, it is known that there are regional differences in the underlying immunology of the small and large intestine, but whether there are differences in context of the intestinal eosinophil in the steady state or inflammation is not known. RESULTS: Our data demonstrates that there are fewer IgA(+) plasma cells in the small intestine of eosinophil-deficient ΔdblGATA-1 mice compared to eosinophil-sufficient wild-type mice, with the difference becoming significant post-infection with Toxoplasma gondii. Remarkably, and in complete contrast, the absence of eosinophils in the inflamed large intestine does not impact on IgA(+) cell numbers during steady state, and is associated with a significant increase in IgA(+) cells post-infection with Trichuris muris compared to wild-type mice. Thus, the intestinal eosinophil appears to be less important in sustaining the IgA(+) cell pool in the large intestine compared to the small intestine, and in fact, our data suggests eosinophils play an inhibitory role. The dichotomy in the influence of the eosinophil over small and large intestinal IgA(+) cells did not depend on differences in plasma cell growth factors, recruitment potential or proliferation within the different regions of the gastrointestinal tract (GIT). CONCLUSIONS: We demonstrate for the first time that there are regional differences in the requirement of eosinophils for maintaining IgA+ cells between the large and small intestine, which are more pronounced during inflammation. This is an important step towards further delineation of the enigmatic functions of gut-resident eosinophils.

The schistosome glutathione S-transferase P28GST, a unique helminth protein, prevents intestinal inflammation in experimental colitis through a Th2-type response with mucosal eosinophils.

Intestinal helminth parasites are potent inducers of T helper type 2 (Th2) response and have a regulatory role, notably on intestinal inflammation. As infection with schistosomes is unlikely to provide a reliable treatment of inflammatory bowel diseases, we have investigated the beneficial effect of a schistosome enzymatic protein, the 28-kDa glutathione S-transferase (P28GST), on the modulation of disease activity and immune responses in experimental colitis. Our results showed that immunization with recombinant P28GST is at least as efficient as established schistosome infection to reduce colitis lesions and expression of pro-inflammatory cytokines. Considering underlying mechanisms, the decrease of inflammatory parameters was associated with the polarization of the immune system toward a Th2 profile, with local and systemic increases of interleukin (IL)-13 and IL-5. Dense eosinophil infiltration was observed in the colons of P28GST-immunized rats and mice. Depletion of eosinophils by treatment with an anti-Siglec-F monoclonal antibody and use of IL-5-deficient mice led to the loss of therapeutic effect, suggesting the crucial role for eosinophils in colitis prevention by P28GST. These findings reveal that immunization with P28GST, a unique recombinant schistosome enzyme, ameliorates intestinal inflammation through eosinophil-dependent modulation of harmful type 1 responses, representing a new immuno-regulatory strategy against inflammatory bowel diseases.

Regulatory T-cell neutralization in mice during filariasis helps in parasite clearance by enhancing T helper type 17-mediated pro-inflammatory response.

Lymphatic filariasis leads to profound impairment of parasite-specific T helper type 1 (Th1) and Th2 immune responses and significantly increases the expression of regulatory networks and regulatory effectors like transforming growth factor-ß, CD25, cytotoxic T-lymphocyte antigen 4, glucocorticoid-induced tumour necrosis factor receptor (GITR) and regulatory T (Treg) cells, which together play an important role in immunosuppression. While Treg cells suppress the activity of effector cells, monocyte dysfunction, characterized by an alternatively activated immunoregulatory phenotype, is one hypothesis that explains the lack of an antigen-specific T-cell response in infected individuals. In the present study, we administered neutralizing antibodies against the Treg cell-associated markers CD25 and GITR and observed its effects on filaria-induced immunosuppression. Our results show that administration of anti-CD25 and anti-GITR in infected animals not only arrested the accumulation of Treg cells and reduced arginase activity, but also led to an increase in the percentages of Th17 cells in the secondary lymphoid organs of mice. Elevated levels of interferon-γ and decreased levels of interleukin-10 were also noted in the culture supernatants of mouse splenocytes that were treated with neutralizing antibodies. Furthermore, treatment with neutralizing antibodies enhanced the expression of inducible nitric oxide synthase on host macrophages and CD40 on host dendritic cells with concomitant decreased expression of alternative activation markers Arg1, Ym1 and Fizz1, which together lead to reduced parasite burden in treated animals. In summary, administration of neutralizing antibodies helps in breaking the regulatory network in mice and limits parasite-induced immunosuppression at the earliest host-parasite interface.

Leucocyte-derived extracellular trap formation significantly contributes to Haemonchus contortus larval entrapment.

BACKGROUND: Polymorphonuclear neutrophil (PMN) and eosinophil extracellular trap (ETs) formation has recently been described as an important host effector mechanism against invading pathogens. So far, scarce evidence on metazoan-triggered ET formation has been published. We here describe for the first time Haemonchus contortus-triggered ETs being released by bovine PMN and ovine eosinophils in response to ensheathed and exsheathed third stage larvae (L3). METHODS: The visualization of ETs was achieved by SEM analysis. The identification of classical ETs components was performed via fluorescence microscopy analysis. The effect of larval exsheathment and parasite integrity on ET formation was evaluated via Pico Green®- fluorescence intensities. ETs formation under acidic conditions was assessed by using media of different pH ranges. Parasite entrapment was evaluated microscopically after co-culture of PMN and L3. ET inhibition experiments were performed using inhibitors against NADPH oxidase, NE and MPO. Eosinophil-derived ETs were estimated via fluorescence microscopy analysis. RESULTS: L3 significantly induced PMN-mediated ETs and significant parasite entrapment through ETs structures was rapidly observed after 60 min of PMN and L3 co-culture. Co-localization studies of PMN-derived extracellular DNA with histones (H3), neutrophil elastase (NE) and myeloperoxidase (MPO) in parasite-entrapping structures confirmed the classical characteristics of ETs. Haemonchus contortus-triggered ETs were significantly diminished by NADPH oxidase-, NE- and MPO-inhibition. Interestingly, different forms of ETs, i.e. aggregated (aggETs), spread (sprETs) and diffused (diffETs) ETs, were induced by L3. AggETs and sprETs firmly ensnared larvae in a time dependent manner. Significantly stronger aggETs reactions were detected upon exposure of PMN to ensheathed larvae than to exsheathed ones. Low pH conditions as are present in the abomasum did not block ETosis and led to a moderate decrease of ETs. Eosinophil-ETs were identified extruding DNA via fluorescence staining. CONCLUSION: We postulate that ETs may limit the establishment of H. contortus within the definitive host by immobilizing the larvae and hampering them from migrating into the site of infection. Consequently, H. contortus-mediated ET formation might have an impact on the outcome of the disease. Finally, besides PMN-triggered ETs, we here present first indications of ETs being released by eosinophils upon H. contortus L3 exposure.

Toxocara canis and the allergic process.

The protective effect of infectious agents against allergic reactions has been thoroughly investigated. Current studies have demonstrated the ability of some helminths to modulate the immune response of infected hosts. The objective of the present study was to investigate the relationship between Toxocara canis infection and the development of an allergic response in mice immunised with ovalbumin (OVA). We determined the total and differential blood and bronchoalveolar lavage fluid cells using BALB/c mice as a model. To this end, the levels of interleukin (IL)-4, IL-5 and IL-10 and anti-OVA-IgE were measured using an ELISA. The inflammatory process in the lungs was observed using histology slides stained with haematoxylin and eosin. The results showed an increase in the total number of leukocytes and eosinophils in the blood of infected and immunised animals at 18 days after infection. We observed a slight lymphocytic inflammatory infiltrate in the portal space in all infected mice. Anti-OVA-IgE levels were detected in smaller proportions in the plasma of immunised and infected mice compared with mice that were only infected. Therefore, we concluded that T. canis potentiates inflammation in the lungs in response to OVA, although anti-OVA-IgE levels suggest a potential reduction of the inflammatory process through this mechanism.