Trichinella spiralis (T. spiralis) is a zoonotic parasitic nematode with a unique life cycle, as all developmental stages are contained within a single host. Excretory-secretory (ES) proteins are the main targets of the interactions between T. spiralis and the host at different stages of development and are essential for parasite survival. However, the ES protein profiles of T. spiralis at different developmental stages have not been characterized. The proteomes of ES proteins from different developmental stages, namely, muscle larvae (ML), intestinal infective larvae (IIL), preadult (PA) 6 h, PA 30 h, adult (Ad) 3 days post-infection (dpi) and Ad 6 dpi, were characterized via label-free mass spectrometry analysis in combination with bioinformatics. A total of 1217 proteins were identified from 9341 unique peptides in all developmental stages, 590 of which were quantified and differentially expressed. GO classification and KEGG pathway analysis revealed that these proteins were important for the growth of the larvae and involved in energy metabolism. Moreover, the heat shock cognate 71 kDa protein was the centre of protein interactions at different developmental stages. The results of this study provide comprehensive proteomic data on ES proteins and reveal that these ES proteins were differentially expressed at different developmental stages. Differential proteins are associated with parasite survival and the host immune response and may be potential early diagnostic antigen or antiparasitic vaccine candidates.

BACKGROUND: Inflammatory bowel disease (IBD) encompasses Crohn\'s Disease and Ulcerative Colitis. Reports have highlighted the potential use of helminths or their byproducts as a possible treatment for IBD; however, the mechanisms underlying their ability to modulate inflammation remain incompletely understood. In the present study, we analyze the possible mechanism of a serine protease inhibitor from adult T. spiralis excretion-secretion products (rTsSPI) on the improvement of colitis.
METHODS: The immune protective effect of rTsSPI was studied by using DSS or Salmonella-induced colitis in female C56BL/6 mice. The effect of rTsSPI on the immune and inflammatory responses, gut microbiota, permeability of colon epithelium and junction proteins was analyzed.
RESULTS: Treating mice with rTsSPI induced type 2 immunity and significantly attenuated clinical symptoms, macroscopical and histological features of DSS or bacteria-induced colonic inflammation. This was accompanied by decreasing neutrophil recruitment in the colonic lamina propria, and reducing TNF-α mRNA levels in the colon; in contrast, the recruitment of M2 macrophages, the expression level of IL-10 and adhesion molecules increased in the colon tissue. Moreover, treatment with rTsSPI led to an improvement in gut microbiota diversity, as well as an increase in the abundance of the bacterial genera Bifidobacterium and Ruminclostridium 5.
CONCLUSIONS: Collective findings suggest that pretreatment with rTsSPI can ameliorate colitis in mice by inducing a Th2-type response with M2 macrophages. Data also indicate that immunotherapy with rTsSPI represents an additional strategy to ameliorate inflammatory processes in IBD by enhancing probiotic colonization and maintaining intestinal epithelial barrier function.

BACKGROUND: Several studies have reported the roles of Trichinella spiralis extracellular vesicles in immune regulation and pathogen diagnosis. Currently, the T. spiralis muscle larvae excretory/secretory product (Ts-ML-ES) is the antigen recommended by the International Commission on Trichinellosis (ICT) for serological diagnosis of trichinellosis. However, it can only be used to detect middle and late stages of infections, and cross-reactions with other parasite detections occur. Therefore, there is a need to identify antigens for specific detection of early stage trichinellosis.
METHODS: Extracellular vesicles of T. spiralis muscle larvae (Ts-ML-EVs) were isolated by ultracentrifugation and characterized by transmission electron microscopy, nanoparticle tracking analysis, flow cytometry and western blot. Ts-ML-EVs protein profiles were analyzed by LC-MS/MS proteomics for identification of potential antigens (Ts-TTPA). Ts-TTPA were cloned into pMAL-c5X vector and expressed as recombinant proteins for evaluation of potential as detected antigens by western blot and ELISA.
RESULTS: Isolated Ts-ML-EVs were round or elliptic (with diameters between 110.1 and 307.6 nm), showing a bilayer membrane structure. The specific surface markers on the Ts-ML-EVs were CD81, CD63, enolase and the 14-3-3 protein. A total of 53 proteins were identified by LC-MS/MS, including a variety of molecules that have been reported as potential detection and vaccine candidates. The cDNA of Ts-TTPA selected in this study has a total length of 1152 bp, encoding 384 amino acids with a molecular weight of 44.19 kDa. It contains a trypsin domain and can be recognized by anti-His antibody. It reacted with swine sera infected with 10,000 T. spiralis at 15, 25, 35 and 60 days post-infection (dpi). At 10 μg/ml, this antigen could detect T. spiralis antibodies from the swine sera at 13 dpi. There were no cross-reactions with the swine sera infected with other parasites including Clonorchis sinensis, Toxoplasma gondii, Taenia suis, Ascaris suis and Trichuris suis.
CONCLUSIONS: This study identifies potential early stage detection antigens and more thoroughly characterizes a serine protease domain-containing protein. Extracellular vesicle proteins may be explored as effective antigens for the early stage detection of trichinellosis.

A novel serine proteinase of Trichinells spiralis (TsSPc) has been identified in the excretion/secretion (ES) antigens, but its role in larval invasion is unclear. The aim of this study was to clone and express TsSPc, identify its biological and biochemical characteristics, and investigate its role on larval invasion of gut epithelium during T. spiralis infection.
TsSPc has a functional domain of serine proteinase, and its tertiary structure consists of three amino acid residues (His88, Asp139 and Ser229) forming a pocket like functional domain. Recombinant TsSPc (rTsSPc) was expressed and purified. The rTsSPc has good immunogenicity. On Western blot analysis, rTsSPc was recognized by infection serum and anti-rTsSPc serum, natural TsSPc in crude and ES antigens was identified by anti-rTsSPc serum. The results of qPCR, Western blot and indirect immunofluorescence test (IIFT) showed that TsSPc was expressed at diverse stage worms, and mainly localized at cuticle, stichosome and intrauterine embryos of this nematode. The rTsSPc had enzymatic activity of native serine protease, which hydrolyzed the substrate BAEE, casein and collagen I. After site directed mutation of enzymatic active sites of TsSPc, its antigenicity did not change but the enzyme activity was fully lost. rTsSPc specifically bound to intestinal epithelium cells (IECs) and the binding sites were mainly localized in cell membrane and cytoplasm. rTsSPc accelerated larval invasion of IECs, whereas anti-rTsSPc antibodies and TsSPc-specific dsRNA obviously hindered larval invasion.
TsSPc was a surface and secretory proteinase of the parasite, participated in larval invasion of gut epithelium, and may be considered as a candidate vaccine target molecule against Trichinella intrusion and infection.

Trichinellosis is considered as a cosmopolitan zoonosis caused by different species of the small nematodes of the genus Trichinella. The present study aimed to provide a broad review for exploring Trichinella sp. infection in humans and animals of Iran and Turkey. Additionally, we aimed to explore bases for trichinellosis prevention and control. Two reports of human trichinellosis following the consumption of meat of wild boar are available in the northern Iran. A large outbreak of trichinellosis and some other sporadic cases are reported mainly as a result of eating wild boar or pork meat from Turkey, where T. britovi is present. Field studies show that Trichinella sp. infections occur in wild carnivores of Iran, particularly the golden jackal (Canis aureus) as the most frequently infected species. T. britovi has been reported to be present elsewhere in Iran in wild mammals, where wild boar is the main source of Trichinella sp. infection. In Turkey, Trichinella spp. has been reported from animals including both domesticated and wild pigs and gray wolf (Canis lupus). However, current data on the distribution of Trichinella taxa are fragmentary in the Anatolian region.

Trichinellosis is caused by Trichinella spiralis, a meat-borne zoonotic disease transmitted to humans through the consumption of infected undercooked or raw meat. Surveillance using safe and precise diagnostic tools to diagnose T. spiralis in sheep is needed to assess the incidence and probability of transmission from sheep to humans. In this study, we developed a real-time PCR assay to detect T. spiralis DNA in ovine muscle samples that can be used as an alternative surveillance tool to ensure food safety using newly designed primers. The assay is specific for the Scfld4 gene of Trichinella (T1) and enables the detection of larvae in ovine muscle tissue samples with high sensitivity and specificity. Trichuris ovis, Oesophagostomum dentatum, Haemonchus contortus, and Bunostomum trigonocephalum showed no nonspecific amplification. The assay could detect Trichinella DNA concentrations as low as 0.0026 ng/μL, equivalent to 0.0064 larvae, indicating a high sensitivity for T. spiralis detection. We used this real-time PCR to detect 73 ovine muscle samples from an ovine abattoir, and five samples tested positive via real-time PCR but negative via microscopy. This assay may provide a more specific and sensitive method for rapidly detecting Trichinella larvae in ovine muscle tissues.

Minks and brown rats are reservoir hosts for many endoparasites including those of the genus Trichinella, a group of parasite nematodes with a worldwide distribution. However, little is known about the prevalence of Trichinella sp. infection in the American mink (Neovison vison) and rats (Rattus norvegicus) in China. Therefore, we aimed to examine the prevalence of Trichinella sp. infection in farmed minks in Weihai city, Shandong province, China and infer the possible route for Trichinella transmission to farmed American minks. In total, 289 muscle samples from minks and 102 carcasses of rats were collected from Weihai City. The appearance of Trichinella sp. was examined using the pooled artificial HCl-pepsin digestion method. The results showed that muscle larvae were detected in 20 of 289 minks (6.92%) and 2 of 102 synanthropic rats (1.96%). The larval density of Trichinella sp. in mink samples ranged from 0.025 to 0.815 larvae per gram (lpg), while the average larval burden in rats was 0.17 lpg. The isolates derived from minks and rats were identified at the species level using multiplex polymerase chain reaction (PCR), which revealed that the size of the two PCR products matched that of T. spiralis at 173 bp. Furthermore, sequence analysis showed 100% identity of the 5S rDNA inter-gene spacer regions of the two isolates to that of T. spiralis. This study presents a novel report of T. spiralis-mediated infection in minks and synanthropic rats in China. We highlight the vulnerability of farmed minks to Trichinella infection through exposure to synanthropic rats, which may raise a public health concern of potential zoonotic risks for domestic animals.

Trichinellosis is caused by Trichinella spiralis muscle larvae (TsML), which is transmitted to human when they eat infected raw or undercooked meat. T. spiralis infection is detected by an enzyme-linked immunosorbent assay (ELISA) using excretory-secretory antigens (ESAg); however, the preparation of ESAg is challenging, and yields are low, which hampers screening efforts. In this study, crude somatic antigens (CSAg) of TsML with molecular weights (MWs) of 43, 79 and 101 kDa have been identified in swine trichinellosis sera with less cross-reaction with uninfected sera and other parasitic infected sera. After that, the CSAg at MWs of 43, 79 and 101 kDa (TsCSAg-43, TsCSAg-79, and TsCSAg-101, respectively) were isolated from sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The eluted antigens were analyzed by IgG-ELISA for sensitivity and specificity, and specific antigens from the three regions were identified by two-dimensional polyacrylamide gel electrophoresis (2-DE) and liquid chromatography-tandem mass spectrometry (LC-MS-MS). The sensitivity of IgG-ELISA using the three eluted antigens was 100% with specificities of 97.77%, 95.54%, 90.63% and for TsCSAg-43, TsCSAg-79, and TsCSAg-101, respectively. The LC-MS-MS results of immunomics showed that 18/20 spots of the antigens with MWs of 43, 79, and 101 kDa represent 11 different proteins identified. TsCSAg-43 showed the highest specificity, indicating that the specific proteins identified, including 45 kDa antigen-trichina [fragment], DNA topoisomerase 2-alpha antigen targeted by protective antibodies, and a conserved hypothetical protein (gi339234223), should be developed and produced in large volumes for further immunodiagnostic studies.

The parasitic nematode Trichinella has a special relationship with its host as it has a unique intracellular location within the feeder cell which is a structure derived from skeletal muscle fiber. It has been proposed that \"parakines\" secreted by Trichinella larvae serve as messengers to implement communication between the parasite and the muscle cells through a molecular cross-talk to ensure permanent coexistence within the host. The Ts-NBL1 protein is considered to be a potential key \"parakine\" involved in the early invasion of the muscle fiber and its transformation into a feeder cell during Trichinella spiralis infection. This study used for the first time yeast two-hybrid (Y2H) technology in Trichinella to identify Ts-NBL1 interacting proteins. GST co-affinity purification experiments confirmed vimentin as an important interactor. The discovery of the new host proteins interacting with Ts-NBL1 will help to suggest that Ts-NBL1 contributes to participate in the capsule formation of feeder cells and provide ideas for understanding the molecular and cellular mechanisms involved in the survival of Trichinella in the host.

Trichinellosis is an important meat-borne zoonotic parasitic disease caused by ingesting raw or semi-cooked meat of pigs and other animals infected with Trichinella sp. muscle larvae. Epidemiological data on human and animal Trichinella sp. infection in the People\'s Republic of China (PRC) during 2009-2020 were analyzed in this review. The results showed that the endemic foci of human trichinellosis are principally localized in southwestern areas, and eight outbreaks covering 479 cases and 2 deaths were reported. Pork is still the primary source of trichinellosis outbreaks. Seven out of 8 outbreaks (87.50%) were caused by ingesting raw or semi-cooked pork. The seroprevalence of swine anti-Trichinella IgG ranged from 0 to 42.11% in 11 provinces/autonomous regions  (P/As), and swine Trichinella infection was detected in six P/A slaughterhouses. The Trichinella-infected pigs came from small backyard farms and outdoor free-ranging pigs in western and southwestern PRC. To prevent trichinellosis, the traditional pig-rearing mode should be improved, more industrialized pig farms should be developed, all pigs should be raised in piggeries under controlled management conditions, and mandatory inspection of Trichinella sp. in slaughtered pigs should be implemented in rural areas of western and southwestern PRC. A One Health approach with participation from governments, public health officials, and medical and veterinary practitioners is vital for controlling zoonotic foodborne trichinellosis.