Effect of recombinant serine protease from adult stage of Trichinella spiralis on TNBS-induced experimental colitis in mice

The prophylactic and therapeutic impact of Trichinella spiralis larvae excretory secretory antigens- loaded Ca-BTC metal organic frameworks on induced murine colitis

Background: Inflammatory bowel disease is an autoimmune disease that affects the gut. T. spiralis larvae (E/S Ags) loaded on calcium-benzene-1,3,5-tricarboxylate metal-organic frameworks (Ca-BTC MOFs) were tested to determine whether they might prevent or cure acetic acid-induced murine colitis. Methods: T. spiralis larvae E/S Ags/Ca-BTC MOFs were used in prophylactic and therapeutic groups to either precede or follow the development of murine colitis. On the seventh day after colitis, mice were slaughtered. The effect of our target antigens on the progress of the colitis was evaluated using a variety of measures, including survival rate, disease activity index, colon weight/bodyweight, colon weight/length) ratios, and ratings for macroscopic and microscopic colon damage. The levels of inflammatory cytokines (interferon-γ and interleukin-4), oxidative stress marker malondialdehyde, and glutathione peroxidase in serum samples were evaluated. Foxp3 T-reg expression was carried out in colonic and splenic tissues. Results: T. spiralis larvae E/S Ags/Ca-BTC MOFs were the most effective in alleviating severe inflammation in murine colitis. The survival rate, disease activity index score, colon weight/length and colon weight/bodyweight ratios, and gross and microscopic colon damage scores have all considerably improved. A large decrease in proinflammatory cytokine (interferon-γ) and oxidative stress marker (malondialdehyde) expression and a significant increase in interleukin-4 and glutathione peroxidase expression were obtained. The expression of Foxp3+ Treg cells was elevated in colonic and splenic tissues. Conclusion: T. spiralis larvae E/S Ags/Ca-BTC MOFs had the highest anti-inflammatory, antioxidant, and cytoprotective capabilities against murine colitis and might be used to develop new preventative and treatment strategies.

Trichinella spiralis inhibits myoblast differentiation by targeting SQSTM1/p62 with a secreted E3 ubiquitin ligase

Trichinella spiralis infection is associated with the formation of cysts within host skeletal muscle cells, thereby enabling immune evasion and subsequent growth and development; however, the pathogenic factors involved in this process and their mechanisms remain elusive. Here, we found that Ts-RNF secreted by T. spiralis is required for its growth and development in host cells. Further study revealed that Ts-RNF functions as an E3 ubiquitin ligase that targets the UBA domain of SQSTM1/p62 by forming K63-type ubiquitin chains. This modification interferes with autophagic flux, leading to impaired mitochondrial clearance and abnormal myotube differentiation and fusion. Our results established that T. spiralis increases its escape by interfering with host autophagy via the secretion of an E3 ubiquitin ligase.

Dietary Zinc Ameliorates TNBS-Induced Colitis in Mice Associated with Regulation of Th1/Th2/Th17 Balance and NF-κB/NLRP3 Signaling Pathway

Inflammatory bowel diseases (IBDs), including Crohn's disease and ulcerative colitis, are chronic relapsing inflammatory gastrointestinal tract diseases of uncertain origin, which are frequently associated with zinc deficiency. Animal models have a considerable value in elucidating the process of IBD. In this study, 50 male C57BL/6 J mice were randomly assigned to five groups: control group (Con), 2,4,6-trinitrobenzenesulfonic acid (TNBS) group, and three zinc supplementation groups, namely 160 ppm group, 400 ppm group, and 1000 ppm group. The results showed that supplementation of dietary zinc with zinc oxide could effectively relieve the severity of ulcerative colitis induced by TNBS in mice. We demonstrate that the protective mechanism involves the immunomodulation of dietary zinc by increasing CD3+, CD3+CD8+, and Th2 cells, suppressing Th1 and Th17 cells, and decreasing the production of serum IL-1β and IL-18. The dietary zinc oxide seems to be able to suppress the NF-κB/NLRP3 signaling pathway by downregulating the mRNA and protein expression of NIK, IKK, NF-κB, and NLRP3. The results suggest that dietary supplementation of zinc oxide may protect against colitis, and proper daily zinc supplementation may reduce the risk of IBD.

Galectin from Trichinella spiralis alleviates DSS-induced colitis in mice by regulating the intestinal microbiota

According to numerous reports, Trichinella spiralis (T. spiralis) and its antigens can reduce intestinal inflammation by modulating regulatory immunological responses in the host to maintain immune homeostasis. Galectin has been identified as a protein that is produced by T. spiralis, and its characterization revealed this protein has possible immune regulatory activity. However, whether recombinant T. spiralis galectin (rTs-gal) can cure dextran sulfate sodium (DSS)-induced colitis remains unknown. Here, the ability of rTs-gal to ameliorate experimental colitis in mice with inflammatory bowel disease (IBD) as well as the potential underlying mechanism were investigated. The disease activity index (DAI), colon shortening, inflammatory cell infiltration, and histological damage were used as indicators to monitor clinical symptoms of colitis. The results revealed that the administration of rTs-gal ameliorated these symptoms. According to Western blotting and ELISA results, rTs-gal may suppress the excessive inflammatory response-mediated induction of TLR4, MyD88, and NF-κB expression in the colon. Mice with colitis exhibit disruptions in the gut flora, including an increase in gram-negative bacteria, which in turn can result in increased lipopolysaccharide (LPS) production. However, injection of rTs-gal may inhibit changes in the gut microbiota, for example, by reducing the prevalence of Helicobacter and Bacteroides, which produce LPS. The findings of the present study revealed that rTs-gal may inhibit signalling pathways that involve enteric bacteria-derived LPS, TLR4, and NF-κB in mice with DSS-induced colitis and attenuate DSS-induced colitis in animals by modulating the gut microbiota. These findings shed additional light on the immunological processes underlying the beneficial effects of helminth-derived proteins in medicine.

Thymopentin ameliorates experimental colitis via inhibiting neutrophil extracellular traps

BACKGROUND

The long-term prognosis of Crohn's disease (CD) remains unsatisfactory. Therefore, we assessed the therapeutic effect of thymopentin (TP5) in a mouse model of 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis, which mimics CD, and analyzed its impact on neutrophil extracellular traps (NETs).

METHODS

NET markers, including myeloperoxidase (MPO), neutrophil elastase (NE), citrullinated histone H3 (CitH3), peptidyl arginine deiminase IV (PAD4), and double-stranded DNA (dsDNA) were assessed by immunostaining and enzyme-linked immunosorbent assay. NET formation was evaluated in vitro. Neoseptin 3, a specific NET agonist, was used to reverse the effect of TP5 on TNBS-induced colitis. The action mechanism of TP5 was investigated using RNA-seq.

RESULTS

TP5 ameliorated weight loss (P < 0.001), disease activity index (DAI) (P = 0.05), colon shrinkage (P = 0.04), and elevated levels of tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1β, IL-6, and neutrophils in the TNBS group. The TNBS group exhibited increased MPO, NE, CitH3, PAD4, dsDNA and MPO-DNA levels (all P < 0.001), which decreased after TP5 administration (P = 0.01, P < 0.001, P < 0.001, P < 0.001, P = 0.02, and P = 0.02 respectively). Tissue CitH3 levels were positively correlated with DAI and TNF-α levels (P < 0.05). Furthermore, phorbol 12-myristate 13-acetate-stimulated NET formation increased by 1.8-, 2.8-, and 2.3-fold in vitro in the control, TNBS + saline, and TNBS + TP5 groups, respectively. Neoseptin 3 significantly reversed the effect of TP5. RNA-seq revealed potential pathways underlying the effect of TP5.

CONCLUSION

TP5 effectively ameliorated colitis by suppressing NETs in the experimental CD model.

Excretory/secretory products from Trichinella spiralis adult worms ameliorate myocardial infarction by inducing M2 macrophage polarization in a mouse model

BACKGROUND

Ischemia-induced inflammatory response is the main pathological mechanism of myocardial infarction (MI)-caused heart tissue injury. It has been known that helminths and worm-derived proteins are capable of modulating host immune response to suppress excessive inflammation as a survival strategy. Excretory/secretory products from Trichinella spiralis adult worms (Ts-AES) have been shown to ameliorate inflammation-related diseases. In this study, Ts-AES were used to treat mice with MI to determine its therapeutic effect on reducing MI-induced heart inflammation and the immunological mechanism involved in the treatment.

METHODS

The MI model was established by the ligation of the left anterior descending coronary artery, followed by the treatment of Ts-AES by intraperitoneal injection. The therapeutic effect of Ts-AES on MI was evaluated by measuring the heart/body weight ratio, cardiac systolic and diastolic functions, histopathological change in affected heart tissue and observing the 28-day survival rate. The effect of Ts-AES on mouse macrophage polarization was determined by stimulating mouse bone marrow macrophages in vitro with Ts-AES, and the macrophage phenotype was determined by flow cytometry. The protective effect of Ts-AES-regulated macrophage polarization on hypoxic cardiomyocytes was determined by in vitro co-culturing Ts-AES-induced mouse bone marrow macrophages with hypoxic cardiomyocytes and cardiomyocyte apoptosis determined by flow cytometry.

RESULTS

We observed that treatment with Ts-AES significantly improved cardiac function and ventricular remodeling, reduced pathological damage and mortality in mice with MI, associated with decreased pro-inflammatory cytokine levels, increased regulatory cytokine expression and promoted macrophage polarization from M1 to M2 type in MI mice. Ts-AES-induced M2 macrophage polarization also reduced apoptosis of hypoxic cardiomyocytes in vitro.

CONCLUSIONS

Our results demonstrate that Ts-AES ameliorates MI in mice by promoting the polarization of macrophages toward the M2 type. Ts-AES is a potential pharmaceutical agent for the treatment of MI and other inflammation-related diseases.

Inhibition of GSDMD-mediated pyroptosis triggered by Trichinella spiralis intervention contributes to the alleviation of DSS-induced ulcerative colitis in mice

BACKGROUND

Inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), is increasing worldwide. Although there is currently no completely curative treatment, helminthic therapy shows certain therapeutic potential for UC. Many studies have found that Trichinella spiralis (T.s) has a protective effect on UC, but the specific mechanism is still unclear.

METHODS

Balb/c mice drank dextran sulfate sodium (DSS) to induce acute colitis and then were treated with T.s. In vitro experiments, the LPS combination with ATP was used to induce the pyroptosis model, followed by intervention with crude protein from T.s (T.s cp). Additionally, the pyroptosis agonist of NSC or the pyroptosis inhibitor vx-765 was added to intervene to explore the role of pyroptosis in DSS-induced acute colitis. The degree of pyroptosis was evaluated by western blot, qPCR and IHC, etc., in vivo and in vitro.

RESULTS

T.s intervention significantly inhibited NLRP3 inflammasome activation and GSDMD-mediated pyroptosis by downregulating the expression of pyroptosis-related signatures in vitro (cellular inflammatory model) and in vivo (DSS-induced UC mice model). Furthermore, blockade of GSDMD-mediated pyroptosis by the caspase-1 inhibitor vx-765 has a similar therapeutic effect on DSS-induced UC mice with T.s intervention, thus indicating that T.s intervention alleviated DSS-induced UC in mice by inhibiting GSDMD-mediated pyroptosis.

CONCLUSION

This study showed that T.s could alleviate the pathological severity UC via GSDMD-mediated pyroptosis, and it provides new insight into the mechanistic study and application of helminths in treating colitis.

Updated immunomodulatory roles of gut flora and microRNAs in inflammatory bowel diseases

Inflammatory bowel disease is a heterogeneous intestinal inflammatory disorder, including ulcerative colitis (UC) and Crohn's disease (CD). Existing studies have shown that the pathogenesis of IBD is closely related to the host's genetic susceptibility, intestinal flora disturbance and mucosal immune abnormalities, etc. It is generally believed that there are complicated interactions between host immunity and intestinal microflora/microRNAs during the occurrence and progression of IBD. Intestinal flora is mainly composed of bacteria, fungi, viruses and helminths. These commensals are highly implicated in the maintenance of intestinal microenvironment homeostasis alone or in combination. MiRNA is an endogenous non-coding small RNA with a length of 20 to 22 nucleotides, which can perform a variety of biological functions by silencing or activating target genes through complementary pairing bonds. A large quantity of miRNAs are involved in intestinal inflammation, mucosal barrier integrity, autophagy, vesicle transportation and other small RNA alterations in IBD circumstance. In this review, the immunomodulatory roles of gut flora and microRNAs are updated in the occurrence and progression of IBD. Meanwhile, the gut flora and microRNA targeted therapeutic strategies as well as other immunomodulatory approaches including TNF-α monoclonal antibodies are also emphasized in the treatment of IBD.

Trichinella spiralis cystatin alleviates polymicrobial sepsis through activating regulatory macrophages

BACKGROUND

Sepsis is a life-threateningorgandysfunction caused by the cytokine storm induced by the severe bacterial infection. Excessive inflammatory responses are responsible for the lethal organ damage during the early stage of sepsis. Helminth infection and helminth-derived proteins have been identified to have the ability to immunomodulate the host immune system by reducing inflammation against inflammatory diseases. Trichinella spiralis cystatin (Ts-Cys) is a cysteine protease inhibitor with strong immunomodulatory functions on host immune system. Our previous studies have shown that excretory-secretory proteins of T. spiralis reduced sepsis-induced inflammation and Ts-Cys was able to inhibit macrophages to produce inflammatory cytokines. Whether Ts-Cys has a therapeutic effect on polymicrobial sepsis and related immunological mechanism are not yet known.

METHODS

Sepsis was induced in BALB/c mice using cecal ligation and puncture (CLP), followed by intraperitoneal injection of 15 µg recombinant Ts-Cys (rTs-Cys). The therapeutic effect of rTs-Cys on sepsis was evaluated by observing the 72-hour survival rates of CLP-induced septic mice and the acute injury of lung and kidney through measuring the wet/dry weight ratio of lung, the levels of blood urea nitrogen (BUN) and creatinine (Cr) in sera and the tissue section pathology. The potential underlying mechanism was investigated using mouse bone marrow-derived macrophages (BMDMs) by observing the effect of rTs-Cys on LPS-stimulated macrophage polarization. The expression of genes associated with macrophage polarization in BMDMs and tissues of septic mice was measured by Western Blotting and qPCR.

RESULTS

In this study, we demonstrated the treatment with rTs-Cys alleviated CLP-induced sepsis in mice with significantly reduced pathological injury in vital organs of lung and kidney and reduced mortality of septic mice. The further study identified that treatment with rTs-Cys promoted macrophage polarization from classically activated macrophage (M1) to alternatively activated macrophage (M2) phenotype via inhibiting TLR2/MyD88 signal pathway and increasing expression of mannose receptor (MR), inhibited pro-inflammatory cytokines (TNF-α, IL-6 and IL-1β) and increased regulatory anti-inflammatory cytokines (IL-10 and TGF-β) in sera and tissues (lung and kidney) of mice with polymicrobial sepsis.

CONCLUSIONS

Our results demonstrated that rTs-Cys had a therapeutic effect on sepsis through activating regulatory macrophages possibly via suppressing TLR2/MyD88 signal pathway. We also identified that rTs-Cys-induced M2 macrophage differentiation was associated with increased expression of MR on the surface of macrophages. Our results underscored the importance of MR in regulating macrophages during the treatment with rTs-Cys, providing another immunological mechanism in which helminths and their derived proteins modulate the host immune system. The findings in this study suggest that rTs-Cys is a potential therapeutic agent for the prevention and treatment of sepsis and other inflammatory diseases.

Trichinella-induced immunomodulation: Another tale of helminth success

Trichinella spiralis is a unique parasite in that both the adults and larvae survive in two different intracellular niches in the same host. The immune response, albeit intense, is highly modulated to ensure the survival of both the host and the parasite. It is skewed to T helper 2 and regulatory arms. Diverse cells from both the innate and adaptive compartments of immunity, including dendritic cells, T regulatory cells, and alternatively activated macrophages are thought to mediate such immunomodulation. The parasite has also an outstanding ability to evade the immune system by several elaborate processes. The molecules derived from the parasites including Trichinella, particularly the components of the excretory-secretory products, are being continually identified and explored for the potential of ameliorating the immunopathology in animal models of diverse inflammatory and autoimmune human diseases. Herein we discuss the various aspects of Trichinella-induced immunomodulation with a special reference to the practical implications of the immune system manipulation in alleviating or possibly curing human diseases.

Cytokines profile in neonatal and adult wild-type mice post-injection of U. S. pediatric vaccination schedule

Introduction

A recent study from our laboratory demonstrated a number of neurobehavioral abnormalities in mice colony injected with a mouse-weight equivalent dose of all vaccines that are administered to infants in their first 18 months of life according to the U. S. pediatric vaccination schedule.

Cytokines have been studied extensively as blood immune and inflammatory biomarkers, and their association with neurodevelopmental disorders. Given the importance of cytokines in early neurodevelopment, we aimed to investigate the potential post-administration effects of the U. S. pediatric vaccines on circulatory cytokines in a mouse model.

In the current study, cytokines have been assayed at early and late time points in mice vaccinated early in postnatal life and compared with placebo controls.

Materials and methods

Newborn mouse pups were divided into three groups: i) vaccine (V1), ii) vaccine ​× ​3 (V3) and iii) placebo control. V1 group was injected with mouse weight-equivalent of the current U. S. pediatric vaccine schedule. V3 group was injected with same vaccines but at triple the dose and the placebo control was injected with saline. Pups were also divided according to the sampling age into two main groups: acute- and chronic-phase group. Blood samples were collected at postnatal day (PND) 23, two days following vaccine schedule for the acute-phase group or at 67 weeks post-vaccination for the chronic-phase groups. Fifteen cytokines were analyzed: GM-CSF, IFN-γ, IL-1β, IL-2, IL-4, IL-5, IL-6, IL-9, IL-10, IL-12p70, IL-13, IL-17A, MCP-1, TNF-α, and VEGF-A. Wilcoxon Rank Sum test or unpaired Student's t-test was performed where applicable.

Results

IL-5 levels in plasma were significantly elevated in the V1 and V3 group compared with the control only in the acute-phase group. The elevation of IL-5 levels in the two vaccine groups were significant irrespective of whether the sexes were combined or analyzed separately. Other cytokines (VEGF-A, TNF-α, IL-10, MCP-1, GM-CSF, IL-6, and IL-13) were also impacted, although to a lesser extent and in a sex-dependent manner. In the acute-phase group, females showed a significant increase in IL-10 and MCP-1 levels and a decrease in VEGF-A levels in both V1 and V3 group compared to controls. In the acute-phase, a significant increase in MCP-1 levels in V3 group and CM-CSF levels in V1 and V3 group and decrease in TNF-α levels in V1 group were observed in treated males as compared with controls. In chronic-phase females, levels of VEGF-A in V1 and V3 group, TNF-α in V3 group, and IL-13 in V1 group were significantly decreased in contrast with controls. In chronic-phase males, TNF-α levels were significantly increased in V1 group and IL-6 levels decreased in V3 group in comparison to controls. The changes in levels of most tested cytokines were altered between the early and the late postnatal assays.

Conclusions

IL-5 levels significantly increased in the acute-phase of the treatment in the plasma of both sexes that were subjected to V1 and V3 injections. These increases had diminished by the second test assayed at week 67. These results suggest that a profound, albeit transient, effect on cytokine levels may be induced by the whole vaccine administration supporting our recently published observations regarding the behavioral abnormalities in the same mice. These observations support the view that the administration of whole pediatric vaccines in a neonatal period may impact at least short-term CNS functions in mice.

Harnessing immunomodulatory mechanisms of Trichinella spiralis to design novel nanomedical approaches for restoring self-tolerance in autoimmunity

The rapid increase in the prevalence of autoimmune diseases in recent decades, especially in developed countries, coincided with improved living conditions and healthcare. Part of this increase could be ascribed to the lack of exposure to infectious agents like helminths that co-evolved with us and display potent immune regulatory actions. In this review we discussed many investigations, including our own, showing that Trichinella spiralis via its excretory-secretory products attenuate Th1/Th17 immunopathological response in autoimmunity and potentiate the protective Th2 and or regulatory T cell response, acting as an effective induction of tolerogenic dendritic cells (DCs), and probably mimicking the autoantigen in some diseases. A recent discovery of T. spiralis extracellular vesicles (TsEVs) suggested that inducing a complex regulation of the immune response requires simultaneous delivery of different signals in nano-sized packages. Indeed, different artificial nanomedical approaches discussed here suggested that co-delivery of multiple signals via nanoparticles is the most promising strategy for the treatment of autoimmune diseases. Although a long way is ahead of us before we could completely replicate natural nano-delivery systems which are both safe and potent in restoring self-tolerance, a clear path is being opened from a careful examination of parasite-host interactions.

Efficient Stool Collection Methods for Evaluating the Diarrhea Score in Mouse Diarrhea Models

BACKGROUND/AIM

The mouse diarrhea score is usually determined by evaluating stool consistency and shape. Thus, defecated stools should be collected without damage or contamination. The study aimed to develop improved mouse stool collection methods and diarrhea-scoring criteria.

MATERIALS AND METHODS

We developed improved stool collection methods (paper towel methods) and compared them with previously used ones (stool collection using regular cages containing bedding chips or filter paper and metabolic cages).

RESULTS

Compared to previously used methods, paper towel methods collected stools without bedding chips-induced contamination, mouse body/foot-induced damage, or sampling errors. When using paper towel methods, wet stools create water marks (diarrhea marks) on paper towels with strong water absorption capacity, by which diarrheal severity can be analyzed semi-quantitatively. To improve the objectivity in determining diarrhea scores, practical diarrhea-scoring criteria were also proposed.

CONCLUSION

These results would be helpful to researchers facing difficulties in evaluating the mouse diarrhea score.

The effects of helminth infections against type 2 diabetes

Type 2 diabetes mellitus (T2D) is a prevalent inflammation-related disease characterized by insulin resistance and elevated blood glucose levels. The high incidence rate of T2D in Western societies may be due to environmental conditions, including reduced worm exposure. In human and animal models, some helminths, such as Schistosoma, Nippostrongylus, Strongyloides, and Heligmosomoides, and their products reportedly ameliorate or prevent T2D progression. T2D induces adaptive immune pathways involved in the inhibition of type 1 immune responses, promotion of type 2 immune responses, and expansion of regulatory T cells and innate immune cells, such as macrophages, eosinophils, and group 2 innate lymphoid cells. Among immune cells expanded in T2DM, type 2 immune cells and macrophages are the most important and may have synergistic effects. The stimulation of host immunity by helminth infections also promotes interactions between the innate and adaptive immune systems. In this paper, we provide a comprehensive review of intestinal helminths' protective effects against T2D.

Therapeutic Efficacy of Excretory-Secretory Products of Trichinella spiralis Adult Worms on Sepsis-Induced Acute Lung Injury in a Mouse Model

Acute lung injury (ALI) is a common complication of systemic inflammation or sepsis with high morbidity and mortality. Although many studies have confirmed that helminth-derived proteins had strong immunomodulatory functions and could be used to treat inflammatory diseases, there is no report on the therapeutic effect of excretory-secretory products of Trichinella spiralis adult worms (Ts-AES) on sepsis-induced ALI. In this study, the therapeutic efficacy of Ts-AES on sepsis-induced ALI and the underlying immunological mechanism and the signaling pathway were investigated. The results indicated that after being treated with Ts-AES, the survival rate of mice with CLP-induced sepsis was significantly increased to 50% for 72 hours after CLP surgery compared to PBS control group with all mice died. The sepsis-induced ALI was largely mitigated characterized by reduced inflammation cell infiltration and pathological changes in lung tissue, with decreased lung injury scores and lung wet/dry weight ratio. The therapeutic efficacy of Ts-AES is associated with stimulated Tregs response with increased regulatory cytokines IL-10 and TGF-β and downregulated pro-inflammatory cytokines (TNF-α, IL-6, IL-1β). The expression of HMGB1, TLR2 and MyD88 in lung tissue was inhibited after treatment of Ts-AES. Our results demonstrated that Ts-AES play an important role in immunomodulation and confer a therapeutic effect on sepsis-induced ALI through inhibiting pro-inflammatory cytokines. The activation of Tregs and increased level of regulatory cytokines IL-10 and TGF-β are possibly involved in the immunomodulatory functions of Ts-AES through HMGB1/TLR2/MyD88 signal pathway. The findings suggest Ts-AES is a potential therapeutic agent for prevention and treatment of sepsis-induced ALI and other inflammatory diseases.

Time-resolved transcriptional profiling of Trichinella-infected murine myocytes helps to elucidate host-pathogen interactions in the muscle stage

Background

Parasites of the genus Trichinella are the pathogenic agents of trichinellosis, which is a widespread and severe foodborne parasitic disease. Trichinella spiralis resides primarily in mammalian skeletal muscle cells. After invading the cells of the host organism, T. spiralis must elude or invalidate the host’s innate and adaptive immune responses to survive. It is necessary to characterize the pathogenesis of trichinellosis to help to prevent the occurrence and further progression of this disease. The aims of this study were to elucidate the mechanisms of nurse cell formation, pathogenesis and immune evasion of T. spiralis, to provide valuable information for further research investigating the basic cell biology of Trichinella-infected muscle cells and the interaction between T. spiralis and its host.

Methods

We performed transcriptome profiling by RNA sequencing to identify global changes at 1, 3, 7, 10 and 15 days post-infection (dpi) in gene expression in the diaphragm after the parasite entered and persisted within the murine myocytes; the mice were infected by intravenous injection of newborn larvae. Gene expression analysis was based on the alignment results. Differentially expressed genes (DEGs) were identified based on their expression levels in various samples, and functional annotation and enrichment analysis were performed.

Results

The most extensive and dynamic gene expression responses in host diaphragms were observed during early infection (1 dpi). The number of DEGs and genes annotated in the Kyoto Encyclopedia of Genes and Genomes and Gene Ontology databases decreased significantly in the infected mice compared to the uninfected mice at 3 and 7 dpi, suddenly increased sharply at 10 dpi, and then decreased to a lower level at 15 dpi, similar to that observed at 3 and 7 dpi. The massive initial reaction of the murine muscle cells to Trichinella infection steadied in the later stages of infection, with little additional changes detected for the remaining duration of the studied process. Although there were hundreds of DEGs at each time point, only 11 genes were consistently up- or downregulated at all 5 time points.

Conclusions

The gene expression patterns identified in this study can be employed to characterize the coordinated response of T. spiralis-infected myocytes in a time-resolved manner. This comprehensive dataset presents a distinct and sensitive picture of the interaction between host and parasite during intracellular infection, which can help to elucidate how pathogens evade host defenses and coordinate the biological functions of host cells to survive in the mammalian environment.

The Regulation of Intestinal Inflammation and Cancer Development by Type 2 Immune Responses

The gut is among the most complex organs of the human body. It has to exert several functions including food and water absorption while setting up an efficient barrier to the outside world. Dysfunction of the gut can be life-threatening. Diseases of the gastrointestinal tract such as inflammatory bowel disease, infections, or colorectal cancer, therefore, pose substantial challenges to clinical care. The intestinal epithelium plays an important role in intestinal disease development. It not only establishes an important barrier against the gut lumen but also constantly signals information about the gut lumen and its composition to immune cells in the bowel wall. Such signaling across the epithelial barrier also occurs in the other direction. Intestinal epithelial cells respond to cytokines and other mediators of immune cells in the lamina propria and shape the microbial community within the gut by producing various antimicrobial peptides. Thus, the epithelium can be considered as an interpreter between the microbiota and the mucosal immune system, safeguarding and moderating communication to the benefit of the host. Type 2 immune responses play important roles in immune-epithelial communication. They contribute to gut tissue homeostasis and protect the host against infections with helminths. However, they are also involved in pathogenic pathways in inflammatory bowel disease and colorectal cancer. The current review provides an overview of current concepts regarding type 2 immune responses in intestinal physiology and pathophysiology.

Excretory/Secretory Products From Trichinella spiralis Adult Worms Attenuated DSS-Induced Colitis in Mice by Driving PD-1-Mediated M2 Macrophage Polarization

Helminth-modulated macrophages contribute to attenuating inflammation in inflammatory bowel diseases. The programmed death 1 (PD-1) plays an important role in macrophage polarization and is essential in the maintenance of immune system homeostasis. Here, we investigate the role of PD-1-mediated polarization of M2 macrophages and the protective effects of excretory/secretory products from Trichinella spiralis adult worms (AES) on DSS-induced colitis in mice. Colitis in mice was induced by oral administration of dextran sodium sulfate (DSS) daily. Mice with DSS-induced colitis were treated with T. spiralis AES intraperitoneally, and pathological manifestations were evaluated. Macrophages in mice were depleted with liposomal clodronate. Markers for M1-type (iNOS, TNF-α) and M2-type (CD206, Arg-1) macrophages were detected by qRT-PCR and flow cytometry. Macrophage expression of PD-1 was quantified by flow cytometry; RAW 264.7 cells and peritoneal macrophages were used for in vitro tests, and PD-1 gene knockout mice were used for in vivo investigation of the role of PD-1 in AES-induced M2 macrophage polarization. Macrophage depletion was found to reduce DSS-induced colitis in mice. Treatment with T. spiralis AES significantly increased macrophage expression of CD206 and Arg-1 and simultaneously attenuated colitis severity. We found T. spiralis AES to enhance M2 macrophage polarization; these findings were confirmed studying in vitro cultures of RAW264.7 cells and peritoneal macrophages from mice. Further experimentation revealed that AES upregulated PD-1 expression, primarily on M2 macrophages expressing CD206. The AES-induced M2 polarization was found to be decreased in PD-1 deficient macrophages, and the therapeutic effects of AES on colitis was reduced in PD-1 knockout mice. In conclusion, the protective effects of T. spiralis AES on DSS-induced colitis were found to associate with PD-1 upregulation and M2 macrophage polarization. Thus, PD-1-mediated M2 macrophage polarization is a key mechanism of helminth-induced modulation of the host immune system.