Immunosuppressive Ability of Trichinella spiralis Adults Can Ameliorate Type 2 Inflammation in a Murine Allergy Model

BACKGROUND

There is an increase in the global incidence of allergies. The hygiene hypothesis and the old friend hypothesis reveal that helminths are associated with the prevalence of allergic diseases. The therapeutic potential of Trichinella spiralis is recognized; however, the stage at which it exerts its immunomodulatory effect is unclear.

METHODS

We evaluated the differentiation of bone marrow-derived macrophages stimulated with T spiralis excretory-secretory products. Based on an ovalbumin-induced murine model, T spiralis was introduced during 3 allergy phases. Cytokine levels and immune cell subsets in the lung, spleen, and peritoneal cavity were assessed.

RESULTS

We found that T spiralis infection reduced lung inflammation, increased anti-inflammatory cytokines, and decreased Th2 cytokines and alarms. Recruitment of eosinophils, CD11b+ dendritic cells, and interstitial macrophages to the lung was significantly suppressed, whereas Treg cells and alternatively activated macrophages increased in T spiralis infection groups vs the ovalbumin group. Notably, when T spiralis was infected prior to ovalbumin challenge, intestinal adults promoted proportions of CD103+ dendritic cells and alveolar macrophages.

CONCLUSIONS

T spiralis strongly suppressed type 2 inflammation, and adults maintained lung immune homeostasis.

A novel trypsin of Trichinella spiralis mediates larval invasion of gut epithelium via binding to PAR2 and activating ERK1/2 pathway

BACKGROUND

Proteases secreted by Trichinella spiralis intestinal infective larvae (IIL) play an important role in larval invasion and pathogenesis. However, the mechanism through which proteases mediate larval invasion of intestinal epithelial cells (IECs) remains unclear. A novel T. spiralis trypsin (TsTryp) was identified in IIL excretory/secretory (ES) proteins. It was an early and highly expressed protease at IIL stage, and had the potential as an early diagnostic antigen. The aim of this study was to investigate the biological characteristics of this novel TsTryp, its role in larval invasion of gut epithelium, and the mechanisms involved.

METHODOLOGY/PRINCIPAL FINDING

TsTryp with C-terminal domain was cloned and expressed in Escherichia coli BL21 (DE3), and the rTsTryp had the enzymatic activity of natural trypsin, but it could not directly degrade gut tight junctions (TJs) proteins. qPCR and western blotting showed that TsTryp was highly expressed at the invasive IIL stage. Immunofluorescence assay (IFA), ELISA and Far Western blotting revealed that rTsTryp specifically bound to IECs, and confocal microscopy showed that the binding of rTsTryp with IECs was mainly localized in the cytomembrane. Co-immunoprecipitation (Co-IP) confirmed that rTsTryp bound to protease activated receptors 2 (PAR2) in Caco-2 cells. rTsTryp binding to PAR2 resulted in decreased expression levels of ZO-1 and occludin and increased paracellular permeability in Caco-2 monolayers by activating the extracellular regulated protein kinases 1/2 (ERK1/2) pathway. rTsTryp decreased TJs expression and increased epithelial permeability, which could be abrogated by the PAR2 antagonist AZ3451 and ERK1/2 inhibitor PD98059. rTsTryp facilitated larval invasion of IECs, and anti-rTsTryp antibodies inhibited invasion. Both inhibitors impeded larval invasion and alleviated intestinal inflammation in vitro and in vivo.

CONCLUSIONS

TsTryp binding to PAR2 activated the ERK1/2 pathway, decreased the expression of gut TJs proteins, disrupted epithelial integrity and barrier function, and consequently mediated larval invasion of the gut mucosa. Therefore, rTsTryp could be regarded as a potential vaccine target for blocking T. spiralis invasion and infection.

Trichinella spiralis cathepsin L induces macrophage M1 polarization via the NF-κB pathway and enhances the ADCC killing of newborn larvae

BACKGROUND

During the early stages of Trichinella spiralis infection, macrophages predominantly undergo polarization to the M1-like phenotype, causing the host's inflammatory response and resistance against T. spiralis infection. As the disease progresses, the number of M2-type macrophages gradually increases, contributing to tissue repair processes within the host. While cysteine protease overexpression is typically associated with inflammation, the specific role of T. spiralis cathepsin L (TsCatL) in mediating macrophage polarization remains unknown. The aim of this study was to assess the killing effect of macrophage polarization mediated by recombinant T. spiralis cathepsin L domains (rTsCatL2) on newborn larvae (NBL).

METHODS

rTsCatL2 was expressed in Escherichia coli strain BL21. Polarization of the rTsCatL2-induced RAW264.7 cells was analyzed by enzyme-linked immunosorbent assay (ELISA), quantitative PCR (qPCR), western blot, immunofluorescence and flow cytometry. The effect of JSH-23, an inhibitor of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), on rTsCatL2-induced M1 polarization investigated. Cytotoxic effects of polarized macrophages on NBL were observed using in vitro killing assays.

RESULTS

Following the co-incubation of rTsCatL2 with RAW264.7 murine macrophage cells, qPCR and ELISA revealed increased transcription and secretion levels of inducible nitric oxide synthase (iNOS), interleukin (IL)-6, IL-1β and tumor necrosis factor alpha (TNF-α) in macrophages. Western blot analysis showed a significant increase in iNOS protein expression, while the expression level of arginase-1 protein remained unchanged. Flow cytometry revealed a substantial increase in the number of CD86-labeled macrophages. The western blot results also indicated that rTsCatL2 increased the expression levels of phospho-NF-κB and phospho-nuclear factor-κB inhibitor alpha (IκB-α) proteins in a dose-dependent manner, while immunofluorescence revealed that rTsCatL2 induced nuclear translocation of the p65 subunit of NF-κB (NF-κB p65) protein in macrophages. The inhibitory effect of JSH-23 suppressed and abrogated the effect of rTsCatL2 in promoting M1 macrophage polarization. rTsCatL2 mediated polarization of macrophages to the M1-like phenotype and enhanced macrophage adhesion and antibody-dependent cell-mediated cytotoxicity (ADCC) killing of NBL.

CONCLUSIONS

The results indicated that rTsCatL2 induces macrophage M1 polarization via the NF-κB pathway and enhances the ADCC killing of NBL. This study provides a further understanding of the interaction mechanism between T. spiralis and the host.

Effects of Trichinella spiralis and its serine protease inhibitors on autophagy of host small intestinal cells

In eukaryotes, autophagy is induced as an innate defense mechanism against pathogenic microorganisms by self-degradation. Although trichinellosis is a foodborne zoonotic disease, there are few reports on the interplay between Trichinella spiralissurvival strategies and autophagy-mediated host defense. Therefore, this study focused on the association between T. spiralis and autophagy of host small intestinal cells. In this study, the autophagy-related indexes of host small intestinal cells after T. spiralis infection were detected using transmission electron microscopy, hematoxylin and eosin staining, immunohistochemistry, quantitative real-time polymerase chain reaction, and Western blotting. The results showed that autophagosomes and autolysosomes were formed in small intestinal cells, intestinal villi appeared edema, epithelial compactness was decreased, microtubule-associated protein 1A/1B-light chain 3B (LC3B) was expressed in lamina propria stromal cells of small intestine, and the expression of autophagy-related genes and proteins was changed significantly, indicating that T. spiralis induced autophagy of host small intestinal cells. Then, the effect of T. spiralis on autophagy-related pathways was explored by Western blotting. The results showed that the expression of autophagy-related pathway proteins was changed, indicating that T. spiralis regulated autophagy by affecting autophagy-related pathways. Finally, the roles of T. spiralis serine protease inhibitors (TsSPIs), such as T. spiralis Kazal-type SPI (TsKaSPI) and T. spiralis Serpin-type SPI (TsAdSPI), were further discussed in vitro and in vivo experiments. The results revealed that TsSPIs induced autophagy by influencing autophagy-related pathways, and TsAdSPI has more advantages. Overall, our results indicated that T. spiralis induced autophagy of host small intestinal cells, and its TsSPIs play an important role in enhancing autophagy flux by affecting autophagy-related pathways. These findings lay a foundation for further exploring the pathogenesis of intestinal dysfunction of host after T. spiralis infection, and also provide some experimental and theoretical basis for the prevention and treatment of trichinellosis.

Identification of proteins that bind extracellular microRNAs secreted by the parasitic nematode Trichinella spiralis

Small non-coding RNAs such as microRNAs (miRNAs) are conserved across eukaryotes and play key roles in regulating gene expression. In many organisms, miRNAs are also secreted from cells, often encased within vesicles such as exosomes, and sometimes extravesicular. The mechanisms of miRNA secretion, how they are stabilised outside of cells and their functional importance are poorly understood. Recently, we characterised the parasitic nematode Trichinella spiralis as a model to study miRNA secretion. T. spiralis muscle-stage larvae (MSL) secrete abundant miRNAs which are largely extravesicular. Here, we investigated how T. spiralis miRNAs might remain stable outside of cells. Using proteomics, we identified two RNA binding proteins secreted by T. spiralis larvae and characterised their RNA binding properties. One, a homologue of the known RNA binding protein KSRP, binds miRNA in a selective and sequence-specific fashion. Another protein, which is likely a novel RNA binding protein, binds to miRNA without exhibiting sequence specificity. Our results suggest a possible mechanism for miRNA secretion by T. spiralis and may have relevance for understanding the biology of extracellular miRNA more widely.

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.

Trichinella spiralis-Secreted Products Promote Collagen Capsule Formation through TGF-β1/Smad3 Pathway

Trichinella spiralis (T. spiralis) muscle larvae colonize in the host's skeletal muscle cells, which are surrounded by collagen capsules. The mechanism underlying muscle stage larva-induced collagen capsule formation remains unknown. To clarify the mechanism, a T. spiralis muscular-infected mouse model was established by a single lateral tail vein injection with 20,000 T. spiralis newborn larvae (NBL). The infected mice were treated with or without SB525334 (TGF-β1 receptor type I inhibitor). Diaphragms were obtained post-infection, and the expression levels of the TGF-β1/Smad3 pathway-related genes and collagen genes (type IV and VI) were observed during the process of collagen capsule formation. The changes in myoblasts under stimulation of the excretory-secretory (ES) products of NBL with or without SB525334 were further investigated. Results showed that the expression levels of type IV collagen gene, type VI collagen gene, Tgfb1, and Smad3 were significantly increased in infected mice muscle cells. The expression levels of all the above genes were enhanced by the products of NBL in myoblast cells. These changes were reversed by co-treatment with SB525334 in vivo and in vitro. In conclusion, the TGF-β1/Smad3 pathway can be activated by T. spiralis infection in muscle cells. The activated TGF-β1/Smad3 pathway can stimulate the secretion of collagens by myocytes and plays a promoting role in the process of collagen capsule formation. The research has the limitation that the protein identification of the products of NBL has yet to be performed. Therefore, the specific components in the T. spiralis ES products that induce collagen synthesis should be further investigated.

Proteomic profile of Trichinella spiralis infected mice with acute spinal cord injury: A 4D label-free quantitative analysis

Spinal cord injury (SCI) can cause severe loss of locomotor and sensory activities, with no ideal treatment. Emerging reports suggest that the helminth therapy is highly effective in relieving numerous inflammatory diseases. Proteomic profiling is often used to elucidate the underlying mechanism behind SCI. Herein, we systematically compared the protein expression profiles of murine SCI spinal cord and Trichinella spiralis treated murine SCI spinal cord, using a 4D label-free technique known for its elevated sensitivity. Relative to the SCI mice, the T. spiralis-treated mice exhibited marked alterations in 91 proteins (31 up- and 60 down-regulated). Based on our Gene Ontology (GO) functional analysis, the differentially expressed proteins (DEPs) were primarily enriched in the processes of metabolism, biological regulation, cellular process, antioxidant activity, and other cell functions. In addition, according to the Clusters of Orthologous Groups of protein/EuKaryotic Orthologous Groups (COG/KOG) functional stratification, proteins involved in signaling transduction mechanisms belonged to the largest category. Over-expressed DEPs were also enriched in the "NADPH oxidase complex", "superoxide anion generation", "other types of O-glycan biosynthesis", and "HIF-1 signaling pathway". Furthermore, the protein-protein interaction (PPI) network identified the leading 10 hub proteins. In conclusion, we highlighted the dynamic proteomic profiling of T. spiralis-treated SCI mice. Our findings provide significant insight into the molecular mechanism behind T. spiralis regulation of SCI.

Resolution of polycistronic RNA by SL2 trans-splicing is a widely conserved nematode trait

Spliced leader trans-splicing is essential for the processing and translation of polycistronic RNAs generated by eukaryotic operons. In C. elegans, a specialized spliced leader, SL2, provides the 5' end for uncapped pre-mRNAs derived from polycistronic RNAs. Studies of other nematodes suggested that SL2-type trans-splicing is a relatively recent innovation, confined to Rhabditina, the clade containing C. elegans and its close relatives. Here we conduct a survey of transcriptome-wide spliced leader trans-splicing in Trichinella spiralis, a distant relative of C. elegans with a particularly diverse repertoire of 15 spliced leaders. By systematically comparing the genomic context of trans-splicing events for each spliced leader, we identified a subset of T. spiralis spliced leaders that are specifically used to process polycistronic RNAs-the first examples of SL2-type spliced leaders outside of Rhabditina. These T. spiralis spliced leader RNAs possess a perfectly conserved stem-loop motif previously shown to be essential for SL2-type trans-splicing in C. elegans We show that genes trans-spliced to these SL2-type spliced leaders are organized in operonic fashion, with short intercistronic distances. A subset of T. spiralis operons show conservation of synteny with C. elegans operons. Our work substantially revises our understanding of nematode spliced leader trans-splicing, showing that SL2 trans-splicing is a major mechanism for nematode polycistronic RNA processing, which may have evolved prior to the radiation of the Nematoda. This work has important implications for the improvement of genome annotation pipelines in nematodes and other eukaryotes with operonic gene organization.

The deficiency of myelin in the mutant taiep rat induces a differential immune response related to protection from the human parasite Trichinella spiralis

Taiep rat is a myelin mutant with a progressive motor syndrome characterized by tremor, ataxia, immobility episodes, epilepsy and paralysis of the hindlimbs. Taiep had an initial hypomyelination followed by a progressive demyelination associated with an increased expression of some interleukins and their receptors. The pathology correlated with an increase in nitric oxide activity and lipoperoxidation. In base of the above evidences taiep rat is an appropriate model to study neuroimmune interactions. The aim of this study was to analyze the immune responses in male taiep rats after acute infection with Trichinella spiralis. Our results show that there is an important decrease in the number of intestinal larvae in the taiep rat with respect to Sprague-Dawley control rats. We also found differences in the percentage of innate and adaptive immune cell profile in the mesenteric lymphatic nodes and the spleen that correlated with the demyelination process that took place on taiep subjects. Finally, a clear pro-inflammatory cytokine pattern was seen on infected taiep rats, that could be responsible of the decrement in the number of larvae number. These results sustain the theory that neuroimmune interaction is a fundamental process capable of modulating the immune response, particularly against the parasite Trichinella spiralis in an animal model of progressive demyelination due to tubulinopathy, that could be an important mechanism for the clinical course of autoimmune diseases associated with parasite infection.

Identification of a host collagen inducing factor from the excretory secretory proteins of Trichinella spiralis

Background

In a previous study, we found that Trichinella spiralis muscle larva excretory and secretory proteins (ES-P) most likely activate collagen synthesis via TGF-β/Smad signaling, and this event could influence collagen capsule formation.

Methodology/Principal findings

In order to identify the specific collagen inducing factor, ES-P was fractionated by a Superdex 200 10/300 GL column. We obtained three large fractions, F1, F2, and F3, but only F3 had collagen gene inducing ability. After immunoscreening, 10 collagen inducing factor candidates were identified. Among them, TS 15–1 and TS 15–2 were identical to the putative trypsin of T. spiralis. The deduced TS 15–1 (M.W. = 72 kDa) had two conserved catalytic motifs, an N-terminal Tryp_SPc domain (TS 15-1n) and a C-terminal Tryp_SPc domain (TS 15-1c). To determine their collagen inducing ability, recombinant proteins (rTS 15-1n and rTS 15-1c) were produced using the pET-28a expression system. TS 15–1 is highly expressed during the muscle larval stage and has strong antigenicity. We determined that rTS 15-1c could elevate collagen I via activation of the TGF-β1 signaling pathway in vitro and in vivo.

Conclusion/Significance

In conclusion, we identified a host collagen inducing factor from T. spiralis ES-P using immunoscreening and demonstrated its molecular characteristics and functions.

Trichinella spiralis can make collagen capsules in host muscle cells during its life cycle, which encapsulates muscle stage larvae. Many investigators have tried to reveal the complex mechanism behind this collagen capsule architecture, and it has been suggested that several serine proteases in excretory-secretory proteins of the parasite are potential collagen capsule inducing factors. In addition, collagen synthesis is activated through the TGF-β/Smad signaling pathway and these events are closely related with protease activated receptor 2 which was activated by various serine proteases. In this study, we isolated and characterized a collagen gene expression inducer from T. spiralis ES-P using immunoscreening and investigated the candidate protein for its usefulness as a wound healing therapeutic agent.

Immuno-proteomic analysis of Trichinella spiralis, T. pseudospiralis, and T. papuae extracts recognized by human T. spiralis-infected sera

The present study explored potentially immunogenic proteins of the encapsulated (Trichinella spiralis) and non-encapsulated (T. pseudospiralis, T. papuae) species within the genus Trichinella. The somatic muscle larval extracts of each species were subjected to immunoblotting analysis using human T. spiralis-infected serum samples. Fifteen reactive bands of all three species were selected for further protein identification by liquid chromatography-tandem mass spectrometry, and their possible functions were ascertained using the gene ontology. Our findings showed immunogenic protein patterns with molecular mass in the range of 33-67 kDa. Proteomic and bioinformatic analysis revealed a wide variety of functions of 17 identified proteins, which are associated with catalytic, binding, and structural activities. Most proteins were involved in cellular and metabolic processes that contribute in the invasion of host tissues and the larval molting processes. The parasite proteins were identified as actin-5C, serine protease, deoxyribonuclease-2, and intermediate filament protein ifa-1. This information may lead to alternative tools for selection of potential diagnostic protein markers or aid in the design of vaccine candidates for prevention and control of Trichinella infection.

High-level expression and characterization of two serine protease inhibitors from Trichinella spiralis

Serine protease inhibitors (SPIs) play important roles in tissue homeostasis, cell survival, development, and host defense. So far, SPIs have been identified from various organisms, such as animals, plants, bacteria, poxviruses, and parasites. In this study, two SPIs (Tsp03044 and TspAd5) were identified from the genome of Trichinella spiralis and expressed in Escherichia coli. Sequence analysis revealed that these two SPIs contained essential structural motifs, which were well conserved within the tumor-infiltrating lymphocytes (TIL) and serpin superfamily. Based on protease inhibition assays, the recombinant Tsp03044 showed inhibitory effects on trypsin, α-chymotrypsin, and pepsin, while the recombinant TspAd5 could effectively inhibit the activities of α-chymotrypsin and pepsin. Both these inhibitors showed activity between 28 and 48 °C. The expression levels of the two SPIs were also determined at different developmental stages of the parasite with real-time PCR. Our results indicate that Tsp03044 and TspAd5 are functional serine protease inhibitors.

Comparative proteomic analysis of surface proteins of Trichinella spiralis muscle larvae and intestinal infective larvae

The critical step for Trichinella spiralis infection is that muscle larvae (ML) are activated to intestinal infective larvae (IIL) and invade intestinal epithelium to further develop. The IIL is its first invasive stage, surface proteins are directly exposed to host environment and are crucial for larval invasion and development. In this study, shotgun LC-MS/MS was used to analyze surface protein profiles of ML and IIL. Totally, 41 proteins common to both larvae, and 85 ML biased and 113 IIL biased proteins. Some proteins (e.g., putative scavenger receptor cysteine-rich domain protein and putative onchocystatin) were involved in host-parasite interactions. Gene ontology analysis revealed that proteins involved in generation of precursor metabolites and energy; and nucleobase, nucleoside, nucleotide and nucleic acid metabolic process were enriched in IIL at level 4. Some IIL biased proteins might play important role in larval invasion and development. qPCR results confirmed the high expression of some genes in IIL. Our study provides new insights into larval invasion, host-Trichinella interaction and for screening vaccine candidate antigens.

[Effect of the excretory/scretory proteins from Trichinella spiralis on apoptosis of NCI-H446 small-cell lung cancer cells]

OBJECTIVE

To investigate the effect of excretory/secretory proteins from Trichinella spiralis on apoptosis of NCI-H446 small-cell lung cancer cells.

METHODS

Trichinella spiralis muscle stage larvae (5 x 10(6)/ml) were cultured in culture media for 24 h, the excretory/secretory proteins were collected from the supernatant of culture media. NCI-H446 small-cell lung cancer cells (No. A05) were randomly divided into three groups: experiment group (A), standard control group (apoptosis group, B), and control group (C). NCI-H446 cells in groups A and B were cultured with 0.3 mg/ml T. spiralis excretory/secretory proteins, and 6.4 microg/ml cisplatin for 24 h, respectively. NCI-H446 cells of group C were cultured for 24 h without any treatment. The expression of Bcl-2, Fas and Fasl mRNA was detected by RT-PCR. C-myc protein expression level was examined by Western blotting and immunofluorescence assay.

RESULTS

The level of Bcl-2 mRNA was lowest in group A(0.575 +/- 0.047) , Bcl-2 mRNA level in group C (0.975 +/- 0.069) was higher than that of group B (0.850 +/- 0.073) (P<0.05). Fas mRNA level was highest in group A (0.975 +/- 0.115), followed by group B (0.817 +/- 0.121) and group C(0.769 +/- 0.061) (P<0.05). The level of Fasl mRNA in groups A, B, and C was 0.669 +/- 0.051, 0.787 +/- 0.124, and 0.875 +/- 0.125, respectively (P<0.05). Fas/Fasl mRNA ratio in groups A, B, and C was 1.475, 1.038, and 0.878. Western blotting showed that the expression of C-myc protein in group C (1.172 +/- 0.026) was highest, followed by group B (1.074 +/- 0.069) and A (0.566 +/- 0.054) (P<0.05). Immunofluorescence test indicated that the C-mye protein was found in the cytoplasm and the nucleus 24 h after treated with 0.3 mg/ml T. spiralis excretory/secretory proteins and 6.4 p.g/ml cisplatin.

CONCLUSION

Trichinella spiralis excretory/secretory proteins may inhibit apoptosis of NCI-H446 small-cell lung cancer cells by reducing the apoptosis protein C-myc and Bcl-2 mRNA levels, and causing the increase of Fas/Fasl mRNA ratio.

Verifiable hypotheses for thymosin β4-dependent and -independent angiogenic induction of Trichinella spiralis-triggered nurse cell formation

Trichinella spiralis has been reported to induce angiogenesis for nutrient supply and waste disposal by the induction of the angiogenic molecule vascular endothelial cell growth factor (VEGF) during nurse cell formation. However, the action mechanism to induce VEGF in nurse cells by T. spiralis is not known. Hypoxia in nurse cells was suggested as a possible mechanism; however, the presence of hypoxic conditions in infected muscle or nurse cells and whether hypoxia indeed induces the expression of VEGF and subsequent angiogenesis in the infected muscle are both a matter of debate. Our recent studies have shown that thymosin β4, a potent VEGF inducing protein, is expressed in the very early stages of T. spiralis muscle infection suggesting the induction of VEGF in early stage nurse cells. Nevertheless, we now show that hypoxic conditions were not detected in any nurse cell stage but were detected only in the accumulated inflammatory cells. These studies propose that induction of angiogenesis by VEGF in T. spiralis-infected nurse cells was mediated by thymosin β4 and is unrelated to hypoxic conditions.

Identification of differentially expressed genes of Trichinella spiralis larvae after exposure to host intestine milieu

Although it has been known for many years that T. spiralis muscle larvae (ML) can not invade intestinal epithelial cells unless they are exposed to the intestinal milieu and activated into intestinal infective larvae (IIL), which genes in IIL are involved in the process of invasion is still unknown. In this study, suppression subtractive hybridization (SSH) was performed to identify differentially expressed genes between IIL and ML. SSH library was constructed using cDNA generated from IIL as the ‘tester’. About 110 positive clones were randomly selected from the library and sequenced, of which 33 T. spiralis genes were identified. Thirty encoded proteins were annotated according to Gene Ontology Annotation in terms of molecular function, biological process, and cellular localization. Out of 30 annotated proteins, 16 proteins (53.3%) had binding activity and 12 proteins (40.0%) had catalytic activity. The results of real-time PCR showed that the expression of nine genes (Ts7, Ndr family protein; Ts8, serine/threonine-protein kinase polo; Ts11, proteasome subunit beta type-7; Ts17, nudix hydrolase; Ts19, ovochymase-1; Ts22, fibronectin type III domain protein; Ts23, muscle cell intermediate filament protein OV71; Ts26, neutral and basic amino acid transport protein rBAT and Ts33, FACT complex subunit SPT16) from 33 T. spiralis genes in IIL were up-regulated compared with that of ML. The present study provide a group of the potential invasion-related candidate genes and will be helpful for further studies of mechanisms by which T. spiralis infective larvae recognize and invade the intestinal epithelial cells.

TsDAF-21/Hsp90 is expressed in all examined stages of Trichinella spiralis

Trichinella is an important parasitic nematode of animals worldwide. Heat shock proteins are ubiquitous in nature and allow organisms to quickly respond to environmental stress. A portion of the Tsdaf-21 gene, a Caenorhabditis elegans daf-21 homologue encoding heat-shock protein 90 (Hsp90) was cloned from Trichinella spiralis. The partial nucleotide sequence resided near the 5'-end of the gene and encoded a polypeptide of 254 amino acid residues harboring a HATPase-c superfamily domain and Hsp90 protein domain. Phylogenetic analysis revealed that Tsdaf-21 is highly conserved and formed a monophyletic clade with other nematodes. The partial Tsdaf-21 transcript was subcloned and expressed for antibody production. Results using PCR primers specific for the Tsdaf-21 transcript, and mouse polyclonal antisera specific for the recombinant protein showed that both the RNA transcript and the corresponding protein were ubiquitously and consistently expressed in newborn larvae, muscle larvae and both male and female adult worms in the absence of any external stress or stimulation.

Proteomic analysis of Trichinella spiralis proteins in intestinal epithelial cells after culture with their larvae by shotgun LC-MS/MS approach

Although it has been known for many years that Trichinella spiralis initiates infection by invading intestinal epithelium, the mechanisms by which the parasite invades the intestinal epithelium are unknown. The purpose of this study was to screen the invasion-related proteins among the increased proteins of intestinal epithelial cells after culture with T. spiralis and to study their molecular functions. The proteins of HCT-8 cells which cultured with T. spiralis infective larvae were analyzed by SDS-PAGE and Western blot. Results showed that compared with proteins of normal HCT-8 cells, four additional protein bands (115, 61, 35 and 24 kDa) of HCT-8 cells cultured with the infective larvae were recognized by sera of the mice infected with T. spiralis, which may be the invasion-related proteins released by the infective larvae. Three bands (61, 35 and 24 kDa) were studied employing shotgun LC-MS/MS. Total 64 proteins of T. spiralis were identified from T. spiralis protein database by using SEQUEST searches, of which 43 (67.2%) proteins were distributed in a range of 10-70 kDa, and 26 proteins (40.6%) were in the range of pI 5-6. Fifty-four proteins were annotated according to Gene Ontology Annotation in terms of molecular function, biological process, and cellular localization. Out of 54 annotated proteins, 43 proteins (79.6%) had binding activity and 23 proteins (42.6%) had catalytic activity (e.g. hydrolase, transferase, etc.), which might be related to the invasion of intestinal epithelial cells by T. spiralis. The protein profile provides a valuable basis for further studies of the invasion-related proteins of T. spiralis.

SL2-like spliced leader RNAs in the basal nematode Prionchulus punctatus: New insight into the evolution of nematode SL2 RNAs

Spliced-leader (SL) trans-splicing has been found in all molecularly characterized nematode species to date, and it is likely to be a nematode synapomorphy. Most information regarding SL trans-splicing has come from the study of nematodes from a single monophyletic group, the Rhabditida, all of which employ SL RNAs that are identical to, or variants of, the SL1 RNA first characterized in Caenorhabditis elegans. In contrast, the more distantly related Trichinella spiralis, belonging to the subclass Dorylaimia, utilizes a distinct set of SL RNAs that display considerable sequence diversity. To investigate whether this is true of other members of the Dorylaimia, we have characterized SL RNAs from Prionchulus punctatus. Surprisingly, this revealed the presence of a set of SLs that show clear sequence similarity to the SL2 family of spliced leaders, which have previously only been found within the rhabditine group (which includes C. elegans). Expression of one of the P. punctatus SL RNAs in C. elegans reveals that it can compete specifically with the endogenous C. elegans SL2 spliced leaders, being spliced to the pre-mRNAs derived from downstream genes in operons, but does not compete with the SL1 spliced leaders. This discovery raises the possibility that SL2-like spliced leaders were present in the last common ancestor of the nematode phylum.

Spliced leader trans-splicing in the nematode Trichinella spiralis uses highly polymorphic, noncanonical spliced leaders

The trans-splicing of short spliced leader (SL) RNAs onto the 5' ends of mRNAs occurs in a diverse range of taxa. In nematodes, all species so far characterized utilize a characteristic, conserved spliced leader, SL1, as well as variants that are employed in the resolution of operons. Here we report the identification of spliced leader trans-splicing in the basal nematode Trichinella spiralis, and show that this nematode does not possess a canonical SL1, but rather has at least 15 distinct spliced leaders, encoded by at least 19 SL RNA genes. The individual spliced leaders vary in both size and primary sequence, showing a much higher degree of diversity compared to other known trans-spliced leaders. In a survey of T. spiralis mRNAs, individual mRNAs were found to be trans-spliced to a number of different spliced leader sequences. These data provide the first indication that the last common ancestor of the phylum Nematoda utilized spliced leader trans-splicing and that the canonical spliced leader, SL1, found in Caenorhabditis elegans, evolved after the divergence of the major nematode clades. This discovery sheds important light on the nature and evolution of mRNA processing in the Nematoda.

Identification, molecular characterisation and differential expression of caveolin-1 in Trichinella spiralis maturing oocytes and embryos☆

Caveolins are integral membrane proteins implicated in cholesterol homeostasis and transport, endocytosis mechanisms and regulation of signal transduction in differentiated cells. In this work a caveolin-1 gene from the nematode Trichinella spiralis (Ts-cav-1) was cloned and identified as an adult-specific antigen. For this, a cDNA library of T. spiralis 3-day-old adult worms was screened using a stage-specific cDNA-labelled probe. One positive clone contained a cDNA insert of 1427-bp and a full-length open reading frame (ORF) of 687-bp, which encodes for a 229 amino acid polypeptide with a theoretical molecular weight of 26kDa. BLAST and FASTA searches revealed a 36% and 57% identity with Caenorhabditis elegans caveolin-1, respectively. Confocal laser microscopy analysis using antibodies generated against Ts-CAV-1 protein and cross-sections of adult parasites showed that Ts-CAV-1 gradually accumulates on the surface of Trichinella oocytes and embryos, reaching a maximum at 3days p.i., and decreasing during new-born larvae (NBL) development. RT-PCR assays of parasites from 1 to 4days p.i. showed a similar gene expression profile to that observed for Ts-CAV-1 which suggests a specific developmental regulation. Free cholesterol was mainly distributed in the female germ line and it displayed increasing membrane accumulation, similar to the pattern obtained for Ts-CAV-1 protein, which suggests a temporal membrane association with Ts-CAV-1 that in turn will perform the functions mentioned above. Our results strongly indicate that Ts-cav-1 from T. spiralis plays a role in oocyte maturation and embryogenesis during development, demonstrating gender-specific expression.

[Prokaryotic expression of Trichinella spiralis gene Ts21 and identification of the recombinant protein]

OBJECTIVE

To express the antigen gene Ts21 of Trichinella spiralis, purify the recombinant protein and test its antigenicity.

METHODS

T. spiralis gene Ts21 was sub-cloned into the prokaryotic expression vector pMAL-c2X and the recombinant pMAL-c2X-Ts21 was constructed. The recombinant plasmid was transformed into E. coli TB1 strain and induced by IPTG. The expression products were purified by MBP-binding affinity chromatography. The antigenicity of the recombinant protein was examined by SDS-PAGE and Western blotting. Mice were immunized with the recombinant protein, the titer of the immune sera was detected by ELISA. The distribution of Ts21 protein in muscle larvae was observed by IFA.

RESULTS

The molecular weight of the expressed fusion protein was about Mr 63,500 and the expression level peaked at 4 h post-incubation. The portion of the fusion protein accounted for 18.2% of all the protein by thin-layer gel optical scanning. Western blotting demonstrated that the recombinant protein was recognized by sera from mice infected by T. spiralis (T1) and T. nelsoni (T7) as well as sera of patients with trichinellosis, but not by sera from mice infected with T. nativa (T2), T. britovi (T3) and T. pseudospiralis (T4). The recombinant protein did not react with sera from patients with ancylostomiasis, cysticercosis and schistosomiasis, but cross-reacted with sera from patients with paragonimiasis, clonorchiasis and echinococcosis. High titers of antibodies were produced in mice immunized with the recombinant protein. IFA showed that the Ts21 protein was mainly distributed in the cuticle of muscle larvae.

CONCLUSION

The Ts21 antigen gene of T. spiralis has been expressed and the recombinant protein shows antigenicity.

Prolactin-like hormone in the nematode Trichinella spiralis larvae

Expression of prolactin (PRL) or prolactin-like hormone has been reported in invertebrates. We investigated the larval phase of Trichinella spiralis: (a) to express 23 kDa PRL, (b) to define its localization and (c) to test its possible biological activity. Immunostaining in isolated larvae demonstrated positive material to 23 kDa PRL by all along the stichosome, specifically in the stichocytes. Homogenized immunoblot larvae showed a 23 kDa protein band. To assess PRL release and its biological activity, larvae were incubated in culture medium and the excretory/secretory products were analyzed by the Nb2 cells bioassay. A cellular growth equivalent until 10 nM PRL and using antibody against 23 kDa PRL, the growth was blocked. In conclusion our result provides evidence that PRL-like hormone is expressed and secreted by the larvae of T. spiralis.

Identification of stage-specifically expressed genes ofTrichinella spiralisby suppression subtractive hybridization

Newborn larvae (NBL) and adult (Ad) stage-specifically expressed genes or members of gene families ofTrichinella spiraliswere identified by suppression subtractive hybridization (SSH)†. Six cDNA clones were identified as NBL stage-specific, including 1 member of theT. spiralisgene family encoding glutamic acid-rich proteins, 2 clones encoding novel serine proteases, 2 closely related clones encoding proteins that are members of a deoxyribonuclease II (DNase II)-like family and 1 clone with no similarity to known genes. Four stage-specific clones encoding homologues of retinoid X receptor, caveolin, C2H2 type zinc finger protein and a putative protein with no homology to known sequences were obtained from 3-day-old adult worms. One gene specifically up-regulated in the 5-day-old adult worms encoding a putative cuticle collagen was also identified.

[Comparative immunochemical analysis of a complete somatic extract, somatic fractionated and excretory-secretory proteins and antigens of T. spiralis larvae]

The paper deals with the analysis of the protein composition of invasion Trichinella larvae, the immunochemical characteristics ofTrichinella antigens of varying molecular mass, the development of the optimum procedures for having the preparative quantities of immunogenic, the so-called major Trichinella antigens that are the major component for the production of diagnostic and prophylactic agents. Twenty nine protein bands were detected in the composite of a complete somatic Trichinella extract. It was ascertained that the most immunogenic peptides with molecular masses of 30, 43, 52-57, and 63-69 kDa were present in all Trichinella protein products while peptides with molecular masses of 43, 50-55 kDa are major antigens both in the fractionated somatic and excretory-secretory proteins in all incubation periods.

Heat shock protein synthesis over time in infective Trichinella spiralis larvae raised in suboptimal culture conditions

Changes in the viability, infectivity and heat shock protein (Hsp) levels are reported in Trichinella spiralis first stage larvae (L1) stored in 199 medium for up to seven days at 37°C. These conditions induce stress that the larvae, eventually, cannot overcome. After three days of storage, the infectivity and viability were unchanged, although higher Hsp70 levels were observed. After this time, larvae gradually lost viability and infectivity, coinciding with a decrease in Hsp70 and Hsp90 and an increase in actin (a housekeeping protein). In addition, a possibly inducible heat shock protein, Hsp90i, appeared as constitutive Hsp90 disappeared. No significant changes in Hsp60 levels were detected at any time. These results suggest that heat shock proteins initially try to maintain homeostasis, but on failing, may be involved in cell death.

Carrier-specificity of a phosphorylcholine-binding antibody requires the presence of the constant domains and is not dependent on the unique VH49 glycine or VH30 threonine residues

Bacterially-produced antibody fragments, such as single-chain Fv (scFv) which comprises the variable regions of the light (VL) and heavy (VH) chains joined together by a short flexible linker, are useful as diagnostic and therapeutic agents. We previously constructed a scFv fragment from a hybridoma antibody (Mab2) but it unexpectedly lacked the unique carrier specificity of the native antibody. Thus, it bound indiscriminately to various phosphorylcholine (PC)-associated antigens, whereas the hybridoma antibody recognized the PC epitope only in the context of the immunizing antigen. Here, we investigated whether the problem was linker-related by changing the linker composition or by deleting it, but these attempts proved futile. Instead, we have constructed a recombinant Fab fragment of the antibody in bacteria that was carrier-specific. This suggests that constant regions are required for the carrier specificity, which presumably helps to mould the fine structure of the antibody combining site or in stabilizing such a structure. Consistent with this global effect is the finding that replacing specific residues in VH with germ-line residues, namely, VH49 glycine and VH30 threonine, both thought previously to be important for the carrier specificity, had no effect on the carrier specificity of the recombinant Fab.

Thermally induced and developmentally regulated expression of a small heat shock protein in Trichinella spiralis

A cDNA encoding a small heat shock protein of Trichinella spiralis, Ts-sHsp, was cloned and expressed and is herein characterized. This cDNA encoded a predicted protein of 165 amino acids, which had a high sequence identity in alpha crystallin domain with various small heat shock proteins of other organisms. A Western blot analysis indicated that anti-Ts-sHsp recombinant antibody recognized the protein of adults and larvae migrating at about 19 kDa. An in situ localization study showed the protein to be abundantly present in the body wall muscle cells, hypodermis, stichocytes, and esophagus of muscle larvae. The Ts-sHsp recombinant protein possessed chaperone activity to suppress the thermally-induced aggregation of citrate synthase. This sHsp was expressed at various developmental stages of T. spiralis, but at different levels. A high level was observed in mature muscle larvae (infective larvae), which was much higher than the levels seen in adults, newborn larvae, or immature muscle larvae. The expression of the sHsp gene was thermal inducible, thus responding to both cold (0 degrees C) and heat shock (43 degrees C) stress; however, at different patterns. The expression of Ts-sHsp increased gradually from 3 to 72 h after cold stress, while the expression was elevated to its highest after 3 h heat stress and then decreased. These results suggest that this small heat shock protein likely plays a role in the tolerance to both chemical and physical stresses, thereby enhancing the survival ability of Trichinella muscle larvae.

Cyclic AMP signaling contributes to neural plasticity and hyperexcitability in AH sensory neurons following intestinal Trichinella spiralis-induced inflammation

Trichinella spiralis infection causes hyperexcitability in enteric after-hyperpolarising (AH) sensory neurons that is mimicked by neural, immune or inflammatory mediators known to stimulate adenylyl cyclase (AC)/cyclic 3',5'-adenosine monophosphate (cAMP) signaling. The hypothesis was tested that ongoing modulation and sustained amplification in the AC/cAMP/phosphorylated cAMP related element binding protrein (pCREB) signaling pathway contributes to hyperexcitability and neuronal plasticity in gut sensory neurons after nematode infection. Electrophysiological, immunological, molecular biological or immunochemical studies were done in T. spiralis-infected guinea-pigs (8000 larvae or saline) after acute-inflammation (7 days) or 35 days p.i., after intestinal clearance. Acute-inflammation caused AH-cell hyperexcitability and elevated mucosal and neural tissue levels of myeloperoxidase, mast cell tryptase, prostaglandin E2, leukotrine B4, lipid peroxidation, nitric oxide and gelatinase; lower level inflammation persisted 35 days p.i. Acute exposure to blockers of AC, histamine, cyclooxygenase or leukotriene pathways suppressed AH-cell hyperexcitability in a reversible manner. Basal cAMP responses or those evoked by forskolin (FSK), Ro-20-1724, histamine or substance P in isolated myenteric ganglia were augmented after T. spiralis infection; up-regulation also occurred in AC expression and AC-immunoreactivity in calbindin (AH) neurons. The cAMP-dependent slow excitatory synaptic transmission-like responses to histamine (mast cell mediator) or substance P (neurotransmitter) acting via G-protein coupled receptors (GPCR) in AH neurons were augmented by up to 2.5-fold after T. spiralis infection. FSK, histamine, substance P or T. spiralis acute infection caused a 5- to 30-fold increase in cAMP-dependent nuclear CREB phosphorylation in isolated ganglia or calbindin (AH) neurons. AC and CREB phosphorylation remained elevated 35 days p.i.. Ongoing immune activation, AC up-regulation, enhanced phosphodiesterase IV activity and facilitation of the GPCR-AC/cAMP/pCREB signaling pathway contributes to T. spiralis-induced neuronal plasticity and AH-cell hyperexcitability. This may be relevant in gut nematode infections and inflammatory bowel diseases, and is a potential therapeutic target.

Secretion and processing of a novel multi-domain cystatin-like protein by intracellular stages of Trichinella spiralis

The excretory-secretory (ES) proteins of nematode parasites are of major interest as they function at the host-parasite interface and are likely to have roles crucial for successful parasitism. Furthermore, the ES proteins of intracellular nematodes such as Trichinella spiralis may also function to regulate gene expression in the host cell. In a recent proteomic analysis we identified a novel secreted cystatin-like protein from T. spiralis L1 muscle larva. Here we show that the protein, MCD-1 (multi-cystatin-like domain protein 1), contains three repeating cystatin-like domains and analysis of the mcd-1 gene structure suggests that the repeated domains arose from duplication of an ancestral cystatin gene. Cystatins are a diverse group of cysteine protease inhibitors and those secreted by parasitic nematodes are important immuno-modulatory factors. The cystatin superfamily also includes cystatin-like proteins that have no cysteine protease inhibitory activity. A recombinant MCD-1 protein expressed as a GST-fusion protein in Escherichia coli failed to inhibit papain in vitro suggesting that the T. spiralis protein is a new member of the non-inhibitory cystatin-related proteins. MCD-1 secreted from T. spiralis exists as high- and low-molecular weight isoforms and we show that a recombinant MCD-1 protein secreted by HeLa cells undergoes pH-dependent processing that may result in the release of individual cystatin-like domains. Furthermore, we found that mcd-1 gene expression is largely restricted to intracellular stages with the highest levels of expression in the adult worms. It is likely that the major role of the protein is during the intestinal stage of T. spiralis infections.

[Analyzing the time course of changes in the titers of specific antibodies while immunization of animals with the biological agent EgFB with different adjuvants]

The recombinant Echinococcus antigens EgF and EgB were prepared and purified by gel filtration and ion-exchange chromatography (800 and 780 mg, respectively being obtained). Four vaccinating complexes, the major component of which were the recombinant antigens EgF and EgB, were developed and tested in an experiment on rabbits. The time course of changes in antibody genesis was studied during a single immunization of the animals with the biological agent EgFB with different adjuvants for 120 days. The adjuvant substances ensuring as components of the biological agent EgFB a long circulation of specific antibodies to the Echinococcus antigens in the blood flow of the immunized animals (complete Freund's adjuvant, multicomponent oil emulsion) are presented.

Functional characterisation of a nematode secreted GM2-activator protein

We have identified a GM2-activator protein (GM2AP) with highly unusual properties secreted by the nematode parasite Trichinella spiralis. Expression in Pichia pastoris resulted in a hyperglycosylated protein of 28 kDa, but the 18 kDa native protein was not glycosylated. The parasite GM2AP does not facilitate degradation of GM2 ganglioside by N-acetyl-beta-hexosaminidase A, although it does inhibit phospholipase D activity. Lack of the former activity might be explained by the absence of a domain implicated in binding to hexosaminidase. In addition, and contrary to data on the human GM2AP, the nematode homologue does not inhibit platelet activating factor-induced calcium mobilisation in neutrophils, but actually enhances mediator-induced chemotaxis.

Molecules released by helminth parasites involved in host colonization

Parasites are designed by evolution to invade the host and survive in its organism until they are ready to reproduce. Parasites release a variety of molecules that help them to penetrate the defensive barriers and avoid the immune attack of the host. In this respect, particularly interesting are enzymes and their inhibitors secreted by the parasites. Serine-, aspartic-, cysteine-, and metalloproteinases are involved in tissue invasion and extracellular protein digestion. Helminths secrete inhibitors of these enzymes (serpins, aspins, and cystatins) to inhibit proteinases, both of the host and their own. Proteinases and their inhibitors, as well as helminth homologues of cytokines and molecules containing phosphorylcholine, influence the immune response of the host biasing it towards the anti-inflammatory Th2 type. Nucleotide-metabolizing enzymes and cholinesterase are secreted by worms to reduce inflammation and expel the parasites from the gastrointestinal tract. An intracellular metazoan parasite, Trichinella spiralis, secretes, among others, protein kinases and phosphatases, endonucleases, and DNA-binding proteins, which are all thought to interfere with the host cellular signals for muscle cell differentiation. Secretion of antioxidant enzymes is believed to protect the parasite from reactive oxygen species which arise from the infection-stimulated host phagocytes. Aside from superoxide dismutase, catalase (rarely found in helminths), and glutathione peroxidase (selenium-independent, thus having a poor activity with H(2)O(2)), peroxiredoxins are probably the major H(2)O(2)-detoxifying enzymes in helminths. Secretion of antioxidant enzymes is stage-specific and there are examples of regulation of their expression by the concentration of reactive oxygen species surrounding the parasite. The majority of parasite-secreted molecules are commonly found in free-living organisms, thus parasites have only adapted them to use in their way of life.

Potential use of Trichinella spiralis antigen for serodiagnosis of human capillariasis philippinensis by immunoblot analysis

Intestinal capillariasis is an emerging helminthic zoonosis caused by Capillaria philippinensis and is frequently fatal if not diagnosed correctly. The present study demonstrates cross-reactivity between Trichinella spiralis larval antigens and C. philippinensis-infected human sera by immunoblotting. Sera from 16 proven intestinal capillariasis patients and 16 proven trichinosis patients were tested. The antigenic patterns recognized by intestinal capillariasis sera varied with the molecular masses, ranging from less than 20.1 to more than 94 kDa. The immunoblotting profiles of the trichinosis sera were similar to those of the intestinal capillariasis sera. The antigenic bands with 100% reactivity were located at 36.5, 40.5, and 54 kDa, respectively. Sera from patients with trichuriasis, strongyloidiasis, opisthorchiasis, and healthy controls differed clearly from the previous two and produced very faint patterns of reactivity and attenuated bands. This assay is potentially useful for large-scale screenings of persons at risk for C. philippinensis infection. Parasitological stool examinations of the positive cases are necessary as second-tier laboratory tests for confirming the diagnosis.

Profiling excretory/secretory proteins of Trichinella spiralis muscle larvae by two-dimensional gel electrophoresis and mass spectrometry

Infection of mammalian skeletal muscle with the intracellular parasite Trichinella spiralis results in profound alterations in the host cell and a realignment of host cell gene expression. The role of parasite excretory/secretory (E/S) products in mediating these effects is unknown, largely due to the difficulty in identifying and assigning function to individual proteins. In this study, we have used two-dimensional electrophoresis to analyse the profile of muscle larva excreted/secreted proteins and have coupled this to protein identification using MALDI-TOF mass spectrometry. Interpretation of the peptide mass fingerprint data has relied primarily on the interrogation of a custom-made Trichinella EST database and the NemaGene cluster database for T. spiralis. Our results suggest that this proteomic approach is a useful tool to study protein expression in Trichinella spp. and will contribute to the identification of excreted/secreted proteins.

Expressed sequence tags from life cycle stages of Trichinella spiralis: application to biology and parasite control

While the approach taken to date to study Trichinella spp., involves mainly characterization of individual genes of interest, we initiated a genomics approach as an antecedent to more complete genome sequencing. Our approach involves use of expressed sequence tags (ESTs) obtained from three life cycle stages of Trichinella spiralis; adult worms (AD), mature muscle larvae (ML) and immature L1 larvae (immL1, also known as newborn larvae) () to improve the technical capacity for research on Trichinella spp. and to generate information that will aid prospective development of relevant hypotheses. In this review, we will summarize findings of our EST analysis and discuss how they relate to topics mentioned above. The foundation laid by this data will also contribute toward development of a more substantial genomic database and technical capacity to dissect molecular interactions between vertebrate hosts and Trichinella spp.

Calcification of Trichinella spiralis larval capsule

Trichinella spiralis larvae were examined in TEM to identify calcareous corpuscles in the outer part of parasite capsule. The microroentgenographic analysis of calcareous corpuscles mainly demonstrated the presence of phosphorus and calcium. The physiological importance of calcareous corpuscles, as well as their significance in decay of T. spiralis larvae were discussed.

Relationship between heat shock protein levels and infectivity in Trichinella spiralis larvae exposed to different stressors

The aim of the present study was to investigate the relationship between infectivity and the levels of two major heat shock proteins (Hsp70 and Hsp60) in Trichinella spiralis larvae. Parasites were exposed to either sublethal thermal stress (43 and 45 degrees C) or to warm or cold temperature oxidative stress. The stressed larvae were then inoculated into female CD1 mice to determine their infectivity. Hsps were detected and quantified by Western blotting using monoclonal antibodies. Infectivity was expressed as larvae per gram of muscle. Warm temperature oxidative stress (20 mM H2O2 at 37 degrees C) caused a significant increase in Hsp levels and total loss of infectivity. Cold oxidative stress (20 mM H2O2 at 4 degrees C) caused no alterations in either Hsp levels or infectivity. However, high oxidative stress and cold (200 mM H2O2 at 4 degrees C) caused a slight increase in Hsp60 levels and a drastic reduction in infectivity. Exposure of the larvae to 43 or 45 degrees C did not significantly alter Hsp levels or infectivity. These results show that (i) cold reduces the deleterious effects of oxidative stress; (ii) heat induces neither increased Hsp60/Hsp70 levels nor reduces infectivity; (iii) increased Hsp levels induced by oxidative stress may cause lower infectivity.

Helminth regulation of host IL-4Ralpha/Stat6 signaling: mechanism underlying NOS-2 inhibition by Trichinella spiralis

Gastrointestinal nematode infection is known to alter host T cell activation and has been used to study immune and inflammatory reactions in which nitric oxide (NO) is a versatile player. We previously demonstrated that Trichinella spiralis infection inhibits host inducible NO synthase (NOS-2) expression. We now demonstrate that (i) an IL-4 receptor alpha-subunit (IL-4Ralpha)/Stat6-dependent but T cell-independent pathway is the key for the nematode-induced host NOS-2 inhibition; (ii) endogenous IL-4 and IL-13, the only known IL-4Ralpha ligands, are not required for activating the pathway; and (iii) treatment of RAW264.7 cells with parasite-cultured medium inhibits NOS-2 expression but not cyclooxygenase 2 expression. We propose that a yet-unidentified substance is released by the nematode during the host-parasite interaction.

Trichinella spiralis secretes a homologue of prosaposin

Infective larvae and adult stage Trichinella spiralis secrete a protein homologous to prosaposin, the precursor of sphingolipid activator proteins (saposins) A-D originally defined in vertebrates. The protein contains four saposin domains, with the six cysteine residues which form the three intramolecular disulphide bonds in close register in each case. It differs substantially from vertebrate prosaposins in the N-terminal prodomain, the region separating saposins A and B, and completely lacks the C-terminal domain which has been demonstrated to be essential for lysosomal targetting in these organisms. The protein is secreted in unprocessed form with an estimated mass of 56 kDa, and contains a single N-linked glycan which is bound by the monoclonal antibody NIM-M1, characteristic of the TSL-1 antigens which are capped by tyvelose (3,6-dideoxy-D-arabinohexose). Immuno-electron microscopy localised the protein to membrane-bound vesicles and more complex multi-lamellar organelles in diverse tissues including the hypodermis, intestine and stichosomes, although it was absent from the dense-core secretory granules typical of the latter. Possible functions of a secreted prosaposin are discussed.

Damage to cell DNA in the bone marrow and testes of mice with experimental trichinosis

Metabolites of Trichinella spiralis produced genotoxic and cytotoxic effects on somatic and generative cells of the host organism. They increased the number of single-chain breaks, alkaline-labile sites in nuclear DNA, and count of apoptotic cells in the bone marrow and testes of infected mice. These effects depended on the stage of parasite development in the host organism and became more pronounced with increasing invasion intensity.

In vitro genotoxic and cytotoxic effects of protein somatic products from helminths on donor blood lymphocytes

Protein somatic products of adult helminths Hymenolepis nana and Toxocara canis and secretory-excretory somatic product of Trichinella spiralis larvae in vitro produced genotoxic and cytotoxic effects on donor blood lymphocytes, which manifested in accumulation of single-chain breaks, alkaline-labile sites in nuclear DNA, and apoptotic cells. This effect depended on the concentration of parasitic protein products during coculturing.

Developmental regulation and secretion of nematode-specific cysteine-glycine domain proteins in Trichinella spiralis

The muscle larva of Trichinella spiralis is an intracellular parasite of mammalian skeletal muscle, encapsulating within a portion of the myofiber and resulting in muscle de-differentiation. Parasite-derived factors secreted or excreted by the muscle larva are thought to play a role in the formation of the host-parasite complex and in the induction of changes in the host cell. We screened a library enriched for T. spiralis-specific cDNAs and identified a clone encoding a protein with similarity to a predicted secreted or extracellular Caenorhabditis elegans protein. The region of similarity included a conserved cysteine-glycine (CCG) domain, which we have identified as being nematode-specific. This domain is present in the predicted T. spiralis protein, Ts-CCG-1, and in a second protein, Ts-CCG-2, which we identified from subsequent analysis. We showed that while the Ts-ccg-1 gene is constitutively expressed, Ts-ccg-2 gene expression is restricted to the muscle L1 larva. Both predicted proteins contain an N-terminal signal peptide and we subsequently confirmed by MALDI-TOF mass spectrometric analyses of excretory/secretory peptide spots excised from two-dimensional gels that Ts-CCG-2 is secreted.

Proteomic analysis of mouse jejunal epithelium and its response to infection with the intestinal nematode,Trichinella spiralis

Infection with the intestinal nematode Trichinella spiralis induces profound, but stereotypic pathological changes to the epithelium, which are common to many nematode infections. This study describes changes in jejunal epithelial protein expression that reflect these stereotypic responses. Adult male BALB/c mice were infected with T. spiralis, and groups (n = 4) examined on day 14/15 (time of worm rejection) were compared with uninfected controls (n = 4). Jejunal epithelium was harvested and extracted for two-dimensional gel electrophoresis. Tryptic peptide mass fingerprinting was used to create a reference map consisting of a total of 52 landmark spots. Of these, 16 were observed to change in intensity during infection. The changes observed at day 14/15 were of relevance to such mechanisms as lipid utilization and transport (increase in triacylglycerol lipase, and reduction in intestinal fatty acid binding protein) and innate immunity (appearance of intelectin-2). As a result, candidate molecules have been identified for further focused studies on their role in the host response to intestinal nematode infection.

Contrasting roles for IL-10 in protective immunity to different life cycle stages of intestinal nematode parasites

Expulsion of the gastro-intestinal nematode Trichinella spiralis is associated with a pronounced mastocytosis mediated by a T helper (Th) 2 type response involving interleukin (IL)-4 and IL-13. Here we demonstrate that IL-10 is a key regulator of protective immune responses against T. spiralis in vivo. IL-10 knockout mice or normal mice treated with a neutralizing anti-IL-10 receptor antibody are highly susceptible to a primary T. spiralis infection and show significantly delayed adult worm expulsion. Depletion of IL-10 resulted in elevated Th1 and Th2 cytokine responses but significantly reduced numbers of mucosal mast cells in the jejunum. Interestingly, the increase in IFN-gamma detected in the absence of IL-10 resulted in increased immunity to larval stages. Hence, IL-10 has a negative effect on immunity to the tissue dwelling larval stages of T. spiralis but plays a significant biological role as an in vivo regulator of intestinal mast cell responses and is crucially involved in protection against adult stages of intestinal parasites in vivo.

Effect of nitric oxide releasing drugs on the intensity of infection during experimental trichinellosis in mice

Nitric oxide (NO) has been shown to play a critical role in various physiological and pathological conditions. Apart from its physiological functions, NO indirectly participates in certain aspects of the pathology of infectious diseases. The aim of this work was to examine the influence of NO-releasing drugs on the intensity of infection in mice infected with Trichinella spiralis. The selected substances were nitroglycerin, isosorbide dinitrate, nitrendipine, sildenafil, and pentaerythritol. These were administered over a prolonged period of time: from the 3rd to the 28th day post-infection. Our study showed that NO administered during trichinellosis may enhance the infection in mice as compared to untreated controls. Thus, treatment with pentaerythritol caused a 44% increase in the intensity of infection relative to the untreated controls, sildenafil a 37% increase, and nitrendipine a 30% increase. This effect may be related to the action of NO on the host's defence mechanisms.

[Morpholgical, histological and histochemical observations on the effect of albendazole on encysted larvae of Trichinella spiralis in mice]

AIM

To study the mechanism of action of albendazole on encysted larvae of Trichinella spiralis in mice.

METHODS

Twelve Kunming strain mice each infected with 200 T. spiralis larvae were equally divided into two groups. Six mice of the treatment group were treated with 30 mg of albendazole/kg daily for 5 days. Morphological, histological and histochemical methods were used.

RESULTS

The encysted larvae of albendazole-treated group became significantly damaged, most worms were shrunken and surrounded by inflammatory cells. Histochemical study demonstrated that the glycogen and RNA content of the larvae in the treated group was decreased, the activities of SDH, ATPase, ACP were lower than those of the control group.

CONCLUSION

Albendazole can affect the physiological function of Trichinella spiralis.

Characterization and cloning of metallo-proteinase in the excretory/secretory products of the infective-stage larva of Trichinella spiralis

Inhibitor sensitivity assays using azocaesin and FTC-caesin as substrates showed that the excretory/secretory (E/S) products of the infective-stage larvae of Trichinella spiralis contained serine, metallo-, cysteine and aspartic proteinases. The activity of the metallo-proteinase was zinc ion dependent (within a range of ZnSO(4) concentrations). Gelatin-substrate gel electrophoresis revealed two bands of molecular mass 48 and 58 kDa which were sensitive to the metallo-proteinase inhibitor EDTA. The former peptide was probably a cleavage product of the latter. The authenticity of the 58 kDa metallo-proteinase as an E/S product was confirmed by immunoprecipitation. Using PCR and RACE reactions, a complete nucleotide sequence of the metallo-proteinase gene was obtained. It comprised 2,223 bp with an open reading frame encoding 604 amino acid residues. The 3' untranslated region consisted of 352 bp, including a polyadenylation signal AATAA. A consensus catalytic zinc-binding motif was present. The conserved domains suggest that the cloned metallo-proteinase belongs to the astacin family and occurs as a single copy gene with 11 introns and 10 exons. Cluster analysis showed that the sequence of the metallo-proteinase gene of T. spiralis resembles those of Caenorhabdites elegans and Strongyloides stercoralis.

Glucose uptake and metabolism in the Trichinella spiralis nurse cell

Isolated Trichinella spiralis nurse cells transport a significantly greater amount of glucose/mg of protein than the normal skeletal muscle cell line (L6). V(max) and K(m) estimations revealed that nurse cells have a much higher saturation point than L6 cells for glucose. The effects of numerous physiological conditions (Na(+) concentration, pH, and temperature) on nurse cell glucose uptake were investigated. It was determined that sodium concentration had no effect on glucose uptake. Low (<6.5) and high (>7.3) pH and low (5 degrees C) temperatures significantly effected glucose uptake. The two hormones, insulin and epinephrine, appeared to have little, if any, influence on the rate of glucose uptake by nurse cells. Glucose uptake was inhibited in the presence of 6-carbon carbohydrates. The H(+)/glucose symport inhibitors, dicyclohexylcarbodiimide (DCCD) and Carbonyl cyanide 4-trifluoromethoxyphenlhydrazone (FCCP), and the facilitated diffusion inhibitor phloretin also inhibited glucose uptake. Oubain, a Na(+)/glucose symport inhibitor, did not inhibit glucose uptake. These data, in conjunction with Western blot analyses, revealed that the transport of glucose occurs via H(+)/glucose symport and facilitated diffusion, perhaps through the glucose transport proteins GLUT 1 and/or 4. It was also demonstrated that nurse cells are capable of synthesising glycogen. It appears that glycogen is in a constant state of flux and physiological conditions, such as glucose concentration, significantly influence the synthesis of this macromolecule. We conclude that these results are consistent with the hypothesis that nurse cells, at least maintained in vitro, are metabolically highly active but show significant divergence from normal muscle cells in several fundamental aspects of sugar metabolism.