Trichinella spiralis infection rapidly induces lung inflammatory response: the lung as the site of helminthocytotoxic activity

Trichinella spiralis -induced immunomodulation signatures on gut microbiota and metabolic pathways in mice

The hygiene hypothesis proposes that decreased exposure to infectious agents in developed countries may contribute to the development of allergic and autoimmune diseases. Trichinella spiralis, a parasitic roundworm, causes trichinellosis, also known as trichinosis, in humans. T. spiralis had many hosts, and almost any mammal could become infected. Adult worms lived in the small intestine, while the larvae lived in muscle cells of the same mammal. T. spiralis was a significant public health threat because it could cause severe illness and even death in humans who eat undercooked or raw meat containing the parasite. The complex interactions between gastrointestinal helminths, gut microbiota, and the host immune system present a challenge for researchers. Two groups of mice were infected with T. spiralis vs uninfected control, and the experiment was conducted over 60 days. The 16S rRNA gene sequences and untargeted LC/MS-based metabolomics of fecal and serum samples, respectively, from different stages of development of the Trichinella spiralis-mouse model, were examined in this study. Gut microbiota alterations and metabolic activity accompanied by parasite-induced immunomodulation were detected. The inflammation parameters of the duodenum (villus/crypt ratio, goblet cell number and size, and histological score) were involved in active inflammation and oxidative metabolite profiles. These profiles included increased biosynthesis of phenylalanine, tyrosine, and tryptophan while decreasing cholesterol metabolism and primary and secondary bile acid biosynthesis. These disrupted metabolisms adapted to infection stress during the enteral and parenteral phases and then return to homeostasis during the encapsulated phase. There was a shift from an abundance of Bacteroides in the parenteral phase to an abundance of probiotic Lactobacillus and Treg-associated-Clostridia in the encapsulated phase. Th2 immune response (IL-4/IL-5/IL-13), lamina propria Treg, and immune hyporesponsiveness metabolic pathways (decreased tropane, piperidine and pyridine alkaloid biosynthesis and biosynthesis of alkaloids derived from ornithine, lysine, and nicotinic acid) were all altered. These findings enhanced our understanding of gut microbiota and metabolic profiles of Trichinella -infected mice, which could be a driving force in parasite-shaping immune system maintenance.

Trickle infection with Heligmosomoides polygyrus results in decreased worm burdens but increased intestinal inflammation and scarring

Introduction

Intestinal roundworms cause chronic debilitating disease in animals, including humans. Traditional experimental models of these types of infection use a large single-dose infection. However, in natural settings, hosts are exposed to parasites on a regular basis and when mice are exposed to frequent, smaller doses of Heligmosomoides polygyrus, the parasites are cleared more quickly. Whether this more effective host response has any negative consequences for the host is not known.

Results

Using a trickle model of infection, we found that worm clearance was associated with known resistance-related host responses: increased granuloma and tuft cell numbers, increased levels of granuloma IgG and decreased intestinal transit time, as well as higher serum IgE levels. However, we found that the improved worm clearance was also associated with an inflammatory phenotype in and around the granuloma, increased smooth muscle hypertrophy/hyperplasia, and elevated levels of Adamts gene expression.

Discussion

To our knowledge, we are the first to identify the involvement of this protein family of matrix metalloproteinases (MMPs) in host responses to helminth infections. Our results highlight the delicate balance between parasite clearance and host tissue damage, which both contribute to host pathology. When continually exposed to parasitic worms, improved clearance comes at a cost.

Searching for the one(s): Using Probiotics as Anthelmintic Treatments

Helminths are a major health concern as over one billion people are infected worldwide and, despite the multiple efforts made, there is still no effective human vaccine against them. The most important drugs used nowadays to control helminth infections belong to the benzimidazoles, imidazothiazoles (levamisole) and macrocyclic lactones (avermectins and milbemycins) families. However, in the last 20 years, many publications have revealed increasing anthelmintic resistance in livestock which is both an economical and a potential health problem, even though very few have reported similar findings in human populations. To deal with this worrying limitation of anthelmintic drugs, alternative treatments based on plant extracts or probiotics have been developed. Probiotics are defined by the Food and Agriculture Organization as live microorganisms, which, when consumed in adequate amounts, confer a health benefit to the host. It has been proven that probiotic microbes have the ability to exert an immunomodulatory effect both at the mucosa and the systemic level. The immune response against gastrointestinal helminths is characterized as a type 2 response, with high IgE levels, increased numbers and/or activity of Th2 cells, type 2 innate lymphoid cells, eosinophils, basophils, mast cells, and alternatively activated macrophages. The oral administration of probiotics may contribute to controlling gastrointestinal helminth infections since it has been demonstrated that these microorganisms stimulate dendritic cells to elicit a type 2 or regulatory immune response, among other effects on the host immune system. Here we review the current knowledge about the use of probiotic bacteria as anthelmintic therapy or as a complement to traditional anthelmintic treatments. Considering all research papers reviewed, we may conclude that the effect generated by probiotics on helminth infection depends not only on the parasite species, their stage and localization but also on the administration scheme.

'Curved tunnel' sign on MRI: a typical radiological feature in hepatic trichinellosis

PURPOSE

To summarize the clinical and radiological features of hepatic trichinellosis.

METHODS

Patients diagnosed with trichinellosis and liver involvement in our institution since 2011 were included retrospectively. Then, qualified patients were divided into a seropositive group and a clinically diagnosed group. Preoperative liver CT and/or MRI images were evaluated independently by two radiologists. The correlations between the radiological and pathological features were evaluated by a radiologist and a pathologist. Independent t-tests were carried out to assess clinical data between groups and those reported in the previous literature. Values of P less than 0.05 were considered statistically significant.

RESULTS

Eventually, ten patients were enrolled, five in each group. All patients recovered successfully after surgical (n = 8) or conservative treatment (n = 2). The clinical, radiological, and pathological features were highly consistent between the two groups. All patients were under 60 years of age (48.0 ± 7.9 years in the seropositive group, 48.6 ± 10.1 years in the clinically diagnosed group), and they were older than those previously reported in the literature (30.5 ± 17 years, n  =  31; P = 0.032 and 0.028). Eosinophilia was found in four patients, and all were mildly increased (˂ 1.5 × 10⁹/L). Lesions in all patients were in the right lobe of the liver, and nine of them showed a characteristic 'curved tunnel' sign on DCE-MRI images. None of the patients had signs or evidence of extrahepatic infection.

CONCLUSION

The 'curved tunnel' sign on MRI is a typical radiological feature in hepatic trichinellosis.

Resiniferatoxin promotes adult worm expulsion in Trichinella spiralis-infected rats by Th2 immune response modulation

BACKGROUND

The immune response during T spiralis infection is characterized by an increase in eosinophils and mast cells, as well as Th2 cytokine production, such as interleukin (IL)-4, IL-10 and IL-13, promoting T spiralis expulsion from the host. However, this response damages the host, favouring the parasite survival. In the search for new pharmacological strategies that protect against T spiralis infection, a recent study showed that treatment with resiniferatoxin (RTX) modulates the Th1 cytokines production, reducing muscle parasite burden.

OBJECTIVE

To evaluate the effect of RTX treatment on the Th2 cytokines production, the number of eosinophils, mast cells and the intestinal expulsion of T spiralis.

METHODS

Serum levels of IL-4, IL-10 and IL-13 were quantified by ELISA; the number of eosinophils, mast cells and the adult worms of T spiralis in the small intestine was quantified.

RESULTS

RTX treatment increased serum levels of IL-4, IL-10 and IL-13, and it decreases intestinal eosinophilia, however, favours the mastocytosis, promoting T spiralis intestinal expulsion.

CONCLUSIONS

These findings suggest that RTX is capable to modulate the Th2 immune response, promoting T spiralis expulsion, which contributes to the defence against T spiralis infection, placing the RTX as a potential immunomodulatory drug.

Protein deficiency during Trichinella spiralis infection impairs lung immunity against newborn larvae

The goal of this study was to analyse the effects of a protein-deficient (PD) diet on antibody-dependent cell-mediated cytotoxicity (ADCC) in vitro against newborn larvae (NBL) of Trichinella spiralis in the lungs of infected rats. Two groups of weaning Wistar rats received a PD diet (6.5% casein) and other two received a control diet (C, 20% casein). After ten days, one group of each diet was infected (PD_I and C_I ) with muscle larvae. Lung tissue extracts (LTE) and lung cell suspension (LCS) were obtained. PD_I had lower titres of anti-NBL antibodies in LTE than C_I . In ADCC assays using control cells, NBL mortality percentage was lower with LTE from PD_I than LTE from C_I (P < .01). In assays using control cytotoxic sera, ADCC was exerted by LCS from C_I at all days post-infection (p.i.), but only by LCS from 13 days p.i. from PD_I . ADCC assays combining LTE and LCS from the same group showed a lower response for PD_I than for C_I (P < .0001). LCS from PD_I contained lower numbers of neutrophils, eosinophils and FcεRI⁺ cells than C_I . PD may diminish ADCC activity against T spiralis NBL in lungs through alterations in specific antibodies and effector cells.

Cellular and molecular changes and immune response in the intestinal mucosa during Trichinella spiralis early infection in rats

Background:

The main targets of the host’s immune system in Trichinella spiralis infection are the adult worms (AW), at the gut level, and the migrant or newborn larvae (NBL), at systemic and pulmonary levels. Most of the studies carried out in the gut mucosa have been performed on the Payer’s patches and/or the mesenteric lymph nodes but not on the lamina propria, therefore, knowledge on the gut immune response against T. spiralis remains incomplete.

Methods

This study aimed at characterizing the early mucosal immune response against T. spiralis, particularly, the events taking place between 1 and 13 dpi. For this purpose, Wistar rats were orally infected with muscle larvae of T. spiralis and the humoral and cellular parameters of the gut immunity were analysed, including the evaluation of the ADCC mechanism exerted by lamina propria cells.

Results

A marked inflammation and structural alteration of the mucosa was found. The changes involved an increase in goblet cells, eosinophils and mast cells, and B and T lymphocytes, initially displaying a Th1 profile, characterised by the secretion of IFN-γ and IL-12, followed by a polarization towards a Th2 profile, with a marked increase in IgE, IgG1, IL-4, IL-5 and IL-13 levels, which occurred once the infection was established. In addition, the helminthotoxic activity of lamina propria cells demonstrated the role of the intestine as a place of migrant larvae destruction, indicating that not all the NBLs released in the gut will be able to reach the muscles.

Conclusions

The characterization of the immune response triggered in the gut mucosa during T. spiralis infection showed that not only an effector mechanism is directed toward the AW but also towards the NBL as a cytotoxic activity was observed against NBL exerted by lamina propria cells.

Role of iBALT in Respiratory Immunity

Pulmonary respiration inevitably exposes the mucosal surface of the lung to potentially noxious stimuli, including pathogens, allergens, and particulates, each of which can trigger pulmonary damage and inflammation. As inflammation resolves, B and T lymphocytes often aggregate around large bronchi to form inducible Bronchus-Associated Lymphoid Tissue (iBALT). iBALT formation can be initiated by a diverse array of molecular pathways that converge on the activation and differentiation of chemokine-expressing stromal cells that serve as the scaffolding for iBALT and facilitate the recruitment, retention, and organization of leukocytes. Like conventional lymphoid organs, iBALT recruits naïve lymphocytes from the blood, exposes them to local antigens, in this case from the airways, and supports their activation and differentiation into effector cells. The activity of iBALT is demonstrably beneficial for the clearance of respiratory pathogens; however, it is less clear whether it dampens or exacerbates inflammatory responses to non-infectious agents. Here, we review the evidence regarding the role of iBALT in pulmonary immunity and propose that the final outcome depends on the context of the disease.

Protein malnutrition impairs the immune control of Trichinella spiralis infection

OBJECTIVES

We aimed to analyze the effect of a protein-deficient diet on mucosal and systemic immunity during a Trichinella spiralis infection.

METHODS

Two groups of weaning Wistar rats received a protein-deficient diet (6.5% casein) and the other two groups received a control diet (20% casein). After 10 d, one group of each diet was infected (PD_I and C_I) with muscle larvae (infecting stage). Food intake and body weight were assessed over time. Blood eosinophils counts, antibodies in serum, and tissue extracts were assessed at different days postinfection. Histologic studies were done in the lungs and intestines, and adult worm (AW) fecundity index score and muscle parasite burden were determined.

RESULTS

Food and protein intake were lower in PD_I than in C_I. Body weight was lower in PD_I than in a non-infected protein-deficient diet. Eosinophils counts were lower in PD_I than in C_I. Total and specific antibodies were lower in PD_I than C_I. PD_I had a reduced number of mast and goblet cells in the lungs and intestines compared with C_I. The persistence of AW in the intestines and migrant larvae at the lungs was longer in PD_I than in C_I.. The AW fecundity index score was higher in PD_I than in C_I. Finally, PD_I evidenced a higher muscular parasite burden than C_I.

CONCLUSIONS

Protein deficiency affects the mucosal and systemic immune response to Trichinella spiralis and delays the expulsion and increases the fecundity index score of AW, which leads to a higher parasite burden in the muscles.

Comprehensive analysis of immune, extracellular matrices and pathogens profile in lung granulomatosis of unexplained etiology

This study analyzed the type 1 and type 2T helper (Th1/Th2) cytokines (including interleukins), immune cellular, matrix profile, and pathogens in granulomas with unexplained etiology compared to those with infectious and noninfectious etiology. Surgical lung biopsies from 108 patients were retrospectively reviewed. Histochemistry, immunohistochemistry, immunofluorescence, morphometry and polymerase chain reaction were used, respectively, to evaluate total collagen and elastin fibers, collagen I and III, immune cells, cytokines, matrix metalloproteinase-9, myofibroblasts, and multiple usual and unusual pathogens. No relevant polymerase chain reaction expression was found in unexplained granulomas. A significant difference was found between the absolute number of eosinophils, macrophages, and lymphocytes within granulomas compared to uninvolved lung tissue. Granulomas with unexplained etiology (UEG) presented increased number of eosinophils and high expression of interleukins (ILs) IL-4/IL-5 and transforming growth factor-β. In sarcoidosis, CD4/CD8 cell number was significantly higher within and outside granulomas, respectively; the opposite was detected in hypersensitivity pneumonitis. Again, a significant difference was found between the high number of myofibroblasts and matrix metalloproteinase-9 in UEG, hypersensitivity pneumonitis, and sarcoidosis compared to granulomas of tuberculosis. Granulomas of paracoccidioisis exhibited increased type I collagen and elastic fibers. Th1 immune cellular profile was similar among granulomas with unexplained, infectious, and noninfectious etiology. In contrast, modulation of Th2 and matrix remodeling was associated with more fibroelastogenesis and scarring of lung tissue in UEG compared to infectious and noninfectious. We concluded that IL-4/IL-5 and transforming growth factor-β might be used as surrogate markers of early fibrosis, reducing the need for genotyping, and promise therapeutic target in unexplained granulomas.

Chemokines and receptors in intestinal B lymphocytes

Recent studies indicate that chemoattractant cytokines (chemokines) and their receptors modulate intestinal B lymphocytes in different ways, including regulating their maturity and differentiation in the bone marrow and homing to intestinal target tissues. Here, we review several important chemokine/chemokine receptor axes that guide intestinal B cells, focusing on the homing and migration of IgA antibody-secreting cells (IgA-ASCs) to intestinal-associated lymphoid tissues. We describe the selective regulation of these chemokine axes in coordinating the IgA-ASC trafficking in intestinal diseases. Finally, we discuss the role of B cells as chemokine producers serving dual roles in regulating the mucosal immune microenvironment.

Therapeutic Effects of Resiniferatoxin Related with Immunological Responses for Intestinal Inflammation in Trichinellosis

The immune response against Trichinella spiralis at the intestinal level depends on the CD4⁺ T cells, which can both suppress or promote the inflammatory response through the synthesis of diverse cytokines. During the intestinal phase, the immune response is mixed (Th1/Th2) with the initial predominance of the Th1 response and the subsequent domination of Th2 response, which favor the development of intestinal pathology. In this context, the glucocorticoids (GC) are the pharmacotherapy for the intestinal inflammatory response in trichinellosis. However, its therapeutic use is limited, since studies have shown that treatment with GC suppresses the host immune system, favoring T. spiralis infection. In the search for novel pharmacological strategies that inhibit the Th1 immune response (proinflammatory) and assist the host against T. spiralis infection, recent studies showed that resiniferatoxin (RTX) had anti-inflammatory activity, which decreased the serum levels of IL-12, INF-γ, IL-1β, TNF-α, NO, and PGE₂, as well the number of eosinophils in the blood, associated with decreased intestinal pathology and muscle parasite burden. These researches demonstrate that RTX is capable to inhibit the production of Th1 cytokines, contributing to the defense against T. spiralis infection, which places it as a new potential drug modulator of the immune response.

Trichinella spiralis: killing of newborn larvae by lung cells

The migratory stage of Trichinella spiralis, the newborn larva (NBL), travels along the pulmonary microvascular system on its way to the skeletal muscle cells. The present work studies the capability of lung cells to kill NBL. For this purpose, in vitro cytotoxicity assays were performed using NBL, lung cell suspensions from Wistar rats, rat anti-NBL surface sera, and fresh serum as complement source. The cytotoxic activity of lung cells from rats infected on day 6 p.i. was compared with that from noninfected rats. Two and 20 h-old NBL (NBL2 and NBL20) were used as they had shown to exhibit different surface antigens altering their biological activity. Sera antibodies were analyzed by indirect immunofluorescence assay, and cell populations used in each assay were characterized by histological staining. The role of IgE in the cytotoxic attack against NBL was analyzed using heated serum. The FcεRI expression on cell suspensions was examined by flow cytometry. Results showed that lung cells were capable of killing NBL by antibody-dependent cell-mediated cytotoxicity (ADCC). Lung cells from infected animals yielded the highest mortality percentages of NBL, with NBL20 being the most susceptible to such attack. IgE yielded a critical role in the cytotoxic attack. Regarding the analysis of cell suspensions, cells from infected rats showed an increase in the percentage of eosinophils, neutrophils, and the number of cells expressing the FcεRI receptor. We conclude that lung cells are capable of killing NBL in the presence of specific antibodies, supporting the idea that the lung is one of the sites where the NBL death occurs due to ADCC.

Qualitative and quantitative studies of eosinophils in parasitic infections

Th2 responses such as peripheral and tissue eosinophilia are characteristic features in the host animals infected with Strongyloides venezuelensis and Trichinella spiralis. Th2 responses are characterized by a specific profile of cytokines and chemokines induced during the course of infection. In this chapter, we describe the methodology that is utilized in our laboratories to study the production of cytokine, chemokine, and antibodies related to the eosinophilia seen in mice infected with the parasites. Furthermore, protocols are described for the different methods used to study eosinophil functions in the blood and tissues of these experimental models of parasitic infections.

Comparative ultrastructural studies of the alterations to mouse lung parenchyma during Trichinella spiralis or Toxocara canis infection

Trichinella spiralis and Toxocara canis larvae migrated through the lung and induced many alterations in the lung parenchyma. Using electron microscopy, we identified and described the histopathological changes. These changes resulted from mechanical damage or from local inflammatory reactions provoked by larvae. The pattern of changes was described between 6 and 12 days post-infection (DPI) with T. spiralis larvae, and between 21 and 28 DPI with T. canis. The ultrastructural studies demonstrated that T. spiralis larvae migrating through the lungs evoked mainly destruction of type I epithelial cells, destruction of lamellar bodies of epithelial cells or extracellular alveolar lining layer. The severity of these changes was dependent on the number of infective larvae (400 or 800 T. spiralis larvae) and possibly the result of mechanical damage in the lung parenchyma. In contrast, infection with T. canis larvae initiated mainly eosinophilic perivasculitis and vasculitis as well as macrophage accumulation in the lung, which were additionally impacted by numerous crystalloid inclusions in macrophages. Trichinella spiralis larvae and T. canis larvae induced different pathological changes in the lungs of infected mice.

Differential pathological and immune responses in newly weaned ferrets are associated with a mild clinical outcome of pandemic 2009 H1N1 infection

Young children are typically considered a high-risk group for disease associated with influenza virus infection. Interestingly, recent clinical reports suggested that young children were the smallest group of cases with severe pandemic 2009 H1N1 (H1N1pdm) influenza virus infection. Here we established a newly weaned ferret model for the investigation of H1N1pdm infection in young age groups compared to adults. We found that young ferrets had a significantly milder fever and less weight loss than adult ferrets, which paralleled the mild clinical symptoms in the younger humans. Although there was no significant difference in viral clearance, disease severity was associated with pulmonary pathology, where newly weaned ferrets had an earlier pathology improvement. We examined the immune responses associated with protection of the young age group during H1N1pdm infection. We found that interferon and regulatory interleukin-10 responses were more robust in the lungs of young ferrets. In contrast, myeloperoxidase and major histocompatibility complex responses were persistently higher in the adult lungs; as well, the numbers of inflammation-prone granulocytes were highly elevated in the adult peripheral blood. Importantly, we observed that H1N1pdm infection triggered formation of lung structures that resembled inducible bronchus-associated lymphoid tissues (iBALTs) in young ferrets which were associated with high levels of homeostatic chemokines CCL19 and CXCL13, but these were not seen in the adult ferrets with severe disease. These results may be extrapolated to a model of the mild disease seen in human children. Furthermore, these mechanistic analyses provide significant new insight into the developing immune system and effective strategies for intervention and vaccination against respiratory viruses.

Corticosteroid administration reduces the concentration of hyaluronan in bronchoalveolar lavage in a murine model of eosinophilic airway inflammation

OBJECTIVE

To analyze the effect of corticosteroid administration on the concentration of hyaluronan (HA) in bronchoalveolar lavage (BAL) in a murine model of eosinophilic airway inflammation and to study the mechanisms involved.

MATERIALS AND METHODS

Untreated-mice or mice treated with 1 μg/g/day betamethasone (Bm) or 0.25 μg/g/day(-1) budesonide (Bd) were sensitized and challenged with Dermatophagoides pteronyssinus (Dp) or saline (control group). The concentration of HA in BAL was determined by ELISA. In vitro migration assays were performed using a Boyden chamber and the expression of HA synthases (HAS) was analyzed by RT-PCR.

RESULTS

We found a significant increase (P < 0.01) in the levels of HA in BAL from Dp-treated mice that was prevented by Bm or Bd. Corticosteroids also inhibited the increase in HAS expression, and the phosphorylation of Akt and ERK in the lungs of challenged mice. Finally, we found that low molecular weight HA induces the chemotaxis of BAL cells in vitro through a mechanism mediated by CD44.

CONCLUSION

We conclude that corticosteroids prevent the increase in HA in BAL from Dp-challenged mice. This effect is associated with reduced expression of HAS and reduced phosphorylation of Akt and ERK in the lungs of challenged mice.