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Giardia duodenalis , also known as G . intestinalis or G . lamblia , is the major cause of giardiasis leading to diarrheal disease with 280 million people infections annually worldwide. Extracellular vesicles (EVs) have emerged as a ubiquitous mechanism participating in cells communications. The aim of this study is to explore the roles of G . duodenalis EVs (GEVs) in host-pathogen interactions using primary mouse peritoneal macrophages as a model. Multiple methods of electron microscopy, nanoparticle tracking analysis, proteomic assays, flow cytometry, immunofluorescence, qPCR, western blot, ELISA, inhibition assays, were used to characterize GEVs, and explore its effects on the host cell innate immunity as well as the underlying mechanism using primary mouse peritoneal macrophages. Results showed that GEVs displayed typical cup-shaped structure with 150 nm in diameter. GEVs could be captured by macrophages and triggered immune response by increasing the production of inflammatory cytokines Il1β, Il6, Il10, Il12, Il17, Ifng, Tnf, Il18, Ccl20 and Cxcl2. Furthermore, activation of TLR2 and NLRP3 inflammasome signaling pathways involved in this process. In addition, CA-074 methyl ester (an inhibitor of cathepsin B) or zVAD-fmk (an inhibitor of pan-caspase) pretreatment entirely diminished these effects triggered by GEVs exposure. Taken together, these findings demonstrated that GEVs could be internalized into mouse peritoneal macrophages and regulate host cell innate immunity via TLR2 and NLRP3 inflammasome signaling pathways.

Clonorchis sinensis is an important food-borne zoonotic parasite which has been linked to biliary fibrosis and cholangiocarcinoma. However, the details of the pathogenesis of C . sinensis were unclear. To explore the role and regulatory mechanism of toll-like receptor 2 (TLR2) in C . sinensis- induced biliary fibrosis, we established the C . sinensis -infected C57BL/6 mouse model with TLR2 -/- and wild type (WT) mice. The mortality rate, liver lesions, TLR2 and TGF-β1 expression, phosphorylation of Smad2/3, AKT, p38, ERK and p65, and cytokine productions were analyzed. Furthermore, similar parameters were examined in mouse biliary epithelial cells (BECs) co-cultured with C . sinensis excretory/secretory proteins (ESPs). The results showed that TLR2 expression was enhanced significantly in C . sinensis -infected WT mice and mouse BECs. C . sinensis -infected TLR2 -/- mice exhibited an increased weight and a decreased mortality rate; significantly alleviated liver lesions and biliary fibrosis, reduced numbers of myofibroblasts; decreased expression of TGF-β1 and phosphorylation level of AKT, p38 and Smad2/3; significantly decreased production of IL-6, TNF-α and IL-4, while increased production of IFN-γ compared with C . sinensis -infected WT mice. Furthermore, C . sinensis ESPs could activate TLR2-mediated AKT and p38 pathways to increase the production of IL-6 in mouse BECs. In conclusion, these data indicate that C . sinensis infection activated TGF-β1-Smad2/3 through TLR2-mediated AKT and p38 pathways to promote IL-6 production, which resulted in myofibroblast activation and aggravating biliary fibrosis in mice.

Background Infection with Trichomonas vaginalis can lead to cervicitis, urethritis, pelvic inflammatory disease, prostatitis and perinatal complications and increased risk of HIV transmission. Here, we used an RPA-based CRISPR-Cas12a assay system in combination with a lateral flow strip (LFS) (referred to as RPA-CRISPR-Cas12a) to establish a highly sensitive and field-ready assay and evaluated its ability to detect clinical samples. Methods We developed a one-pot CRISPR-Cas12a combined with RPA-based field detection technology for T. vaginalis , chose actin as the target gene to design crRNA and designed RPA primers based on the crRNA binding site. The specificity of the method was demonstrated by detecting genomes from nine pathogens. To improve the usability and visualize the RPA-CRISPR-Cas12a assay results, both fluorescence detection and LFS readouts were devised. Results The RPA-CRISPR-Cas12a assay platform was completed within 60 min and had a maximum detection limit of 1 copy/µl and no cross-reactivity with Candida albicans , Mycoplasma hominis , Neisseria gonorrhoeae , Escherichia coli , Cryptosporidium parvum , G. duodenalis or Toxoplasma gondii after specificity validation. Thirty human vaginal secretions were tested by RPA-CRISPR-Cas12a assays, and the results were read by a fluorescent reporter and LFS biosensors and then compared to the results from nested PCR detection of these samples. Both RPA-CRISPR-Cas12a assays showed 26.7% (8/30) T. vaginalis -positive samples and a consistency of 100% (8/8). The RPA-CRISPR-Cas12a assays had a higher sensitivity than nested PCR (only seven T. vaginalis -positive samples were detected). Conclusions The T. vaginalis RPA-CRISPR-Cas12a assay platform in this study can be used for large-scale field testing and on-site tests without the need for trained technicians or costly ancillary equipment. Graphical abstract

Clonorchis sinensis ( C. sinensis ) is a food-borne zoonotic parasite link to liver fibrosis and cholangiocarcinoma. Limited understanding of its mechanisms in causing liver fibrosis has impeded therapeutic advances for C. sinensis -induced liver lesions. Ferroptosis, a novel form of cell death involving iron overload and lipid peroxidation, exacerbates liver fibrosis; however, its role in C. sinensis infection remains unexplored. In this study, ferroptosis were detected in C. sinensis -infected C57BL/6 mice as well as in AML12 cells stimulated by C. sinensis excretory/secretory products (ESPs). 12 ferroptosis related genes were screened and we found glutathione peroxidase 4 (GPX4, 7 d), solute carrier family 7 member 11 (SLC7A11, 7 d) and nuclear factor erythroid 2 related factor 2 (Nrf2, 35 d) was significantly decreased in mice. Western blot results confirmed C. sinensis and ESPs down-regulated the expression of GPX4, SLC7A11 and Nrf2. GSH depletion, malondialdehyde (MDA) accumulation, mitochondrial structure damage, and iron overload were found in C. sinensis- infected mice and ESPs-stimulated AML12 cells, suggesting that ferroptosis occurred in vivo and in vitro . Treatment with ferroptosis inhibitor Fer-1 in C. sinensis- infected mice alleviated ferroptosis, reduced the productions of IFN-γ, TNF-α, IL-12 and IL-6, and downregulated transforming growth factor (TGF)-β/Smad pathway activation. In AML12 cells, Fer - 1 pretreatment reduced ESPs - induced ferroptosis and IL-6, TNF-α production. Fer - 1 also alleviated liver lesions, reduced parasite load (65%), α-SMA expression and collagen fiber deposition in infected mice. In conclusion, C. sinensis could cause ferroptosis, which promoted the secretions of IL-6 and TNF-α as well as the activation of TGF-β/Smad pathway, leading to exacerbated liver fibrosis.

Pentatrichomonas hominis is a parasitic trichomonads protozoa that parasitizes in the colon and cecum of humans and other animals. Our previous studies have demonstrated that infection with P. hominis is associated with the incidence of colon cancer (37.93%). However, the mechanism by which P. hominis infections increase the incidence of colon cancer remains unclear. Previous studies have suggested that certain parasites promote colon cancer by regulating gut microbiota. This study aimed to elucidate whether the association between P. hominis infections and the increased incidence of colon cancer is related to changes in gut microbiota. Therefore, the gut microbiota patients with colon cancer who were infected with P. hominis and uninfected patients with colon cancer were analyzed by 16S rRNA high-throughput sequencing. The results demonstrated that patients with colon cancer who were not infected with P. hominis showed increased gut bacterial diversity, a higher relative abundance of Alcaligenes sp., Leucobacter sp., Paraprevotella sp., Ruminococcaceae UCG-002 , and a significant reduction in the abundance of Veillonella sp., compared to individuals without colon cancer. Additionally, the relative abundance of the Ruminococcaceae UCG-002 and the Eubacterium eligens groups was reduced, while the relative abundance of bacteria associated with colon cancer, including Flavonifractor sp., Lachnoclostridium sp., and the Ruminococcus gnavus group, increased significantly in patients with colon cancer who were infected with P. hominis , compared to those of uninfected patients with colon cancer. In conclusion, these results suggested that P. hominis infections may aggravate the development of colon cancer and the findings provide new insights for subsequent in-depth studies on the pathogenesis, diagnosis, and prevention of colon cancer.

Neosporosis is considered as one of the main causes of abortion and severe economic losses in dairy industry. The genus serving as one of the confirmed definitive hosts of the apicomplexan parasite ( ) plays a critical role in its life cycle. However, the effects of on its definitive hosts of neutrophils extracellular traps (NETs) formation remain unclear. In the present study, tachyzoite-induced canine NETs formation was observed by scanning electron microscopy (SEM). Visualization of DNA decorated with H3, neutrophil elastase (NE), and myeloperoxidase (MPO) within tachyzoite-induced NETs were examined using fluorescence confocal microscopy analyses. Furthermore, the formation of canine NETs was quantified using Sytox Green staining, and the LDH levels in supernatants were examined by an LDH Cytotoxicity Assay kit. The results clearly showed that NETs-like structures were induced by tachyzoites, and the major components within these structures induced by tachyzoite were further confirmed by fluorescence confocal microscopy visualization. These results suggest that tachyzoites strongly induced NETs formation in canine polymorphonuclear neutrophils (PMN). In functional inhibition assays, the blockings of NADPH oxidase, NE, MPO, SOCE, ERK 1/2, and p38 MAPK signaling pathways significantly inhibited tachyzoite-induced NETs formation. To our knowledge, this study is the first to report the formation of NETs in canine PMN against infection.

Clonorchis sinensis is a zoonotic parasite associated with liver fibrosis and cholangiocarcinoma development. The role of toll-like receptors (TLRs) in C . sinensis infection has not yet been fully elucidated. Here, the TLR3 signaling pathway, cytokine expression and liver fibrosis were examined in C . sinensis- infected wildtype (WT) and TLR3 -/- mice. Polyinosinic-polycytidylic acid (Poly (I:C)) was used to treat C . sinensis infections. The results showed that TLR3 deficiency caused severe clonorchiasis with increased parasite burden, exacerbated proinflammatory cytokine expression and liver lesions, promoted the TGF-β1/Smad2/3 pathway and myofibroblast activation, exacerbated liver fibrosis (compared to WT mice). Poly (I:C) intervention increased the body weight, decreased mouse mortality and parasite burden, reduced liver inflammation, and alleviated C . sinensis- induced liver fibrosis. Furthermore, C . sinensis extracellular vesicles (CsEVs) promote the production of IL-6, TNF in WT biliary epithelial cells (BECs) via p38/ERK pathway, compared with control group, while TLR3 deletion induced much higher levels of IL-6 and TNF in TLR3 -/- BECs than that in WT BECs. Taken together, TLR3 inhibit IL-6 and TNF production via p38/ERK signaling pathway, a phenomenon that resulted in the alleviation of C . sinensis -induced liver fibrosis. Poly (I:C) is a potential treatment for clonorchiasis.

infection is one of the most common causes of waterborne diarrheal disease in a wide array of mammalian hosts, including humans globally. Although numerous studies have indicated that adaptive immune responses are important for defense, however, whether the host innate immune system such as TLRs recognizes remains poorly understood. TLR2 plays a crucial role in pathogen recognition, innate immunity activation, and the eventual pathogen elimination. In this study, we investigated the role of TLR2 as a non-protective inflammatory response on controlling the severity of giardiasis. RT-PCR analysis suggested that TLR2 expression was increased . We demonstrated that -induced cytokines expression by the activation of p38 and ERK pathways TLR2. Interestingly, the expression of IL-12 p40, TNF-α, and IL-6, but not IFN-γ, was enhanced in TLR2-blocked and TLR2 mouse macrophages exposed to trophozoites compared with wild-type (WT) mouse macrophages. Further analysis demonstrated that trophozoites reduced cytokines secretion by activating AKT pathway in WT mouse macrophages. Immunohistochemical staining in cysts infected TLR2 and WT mice showed that TLR2 was highly expressed in duodenum in infected WT mice. Also, infected TLR2 and AKT-blocked mice showed an increased production of IL-12 p40 and IFN-γ compared with infected WT mice at the early stage during infection. Interestingly, infected TLR2 and AKT-blocked mice displayed a decreased parasite burden, an increased weight gain rate, and short parasite persistence. Histological morphometry showed shortened villus length, hyperplastic crypt and decreased ratio of villus height/crypt depth in infected WT mice compared with in infected TLR2 and AKT-blocked mice. Together, our results suggested that TLR2 deficiency leads to alleviation of giardiasis and reduction of parasite burden through the promotion of proinflammatory cytokines production. For the first time, our results demonstrated that TLR2 played a negative role in host defense against .

Giardiasis is a globally prevalent waterborne zoonosis. Rapid enrichment and detection technologies for this disease are essential. Cyst outer wall proteins are ideal targets for the enrichment and detection of cysts in the environment, but there are few available targets with suboptimal effectiveness. In this study, Giardia duodenalis (G. duodenalis) cysts were purified, and outer wall proteins were biotinylated, followed by streptavidin magnetic bead purification and mass spectrometry. Sixty-three novel cyst wall proteins were identified, and their functions were annotated through Gene Ontology (GO) and KEGG analyses. The β-giardin and α-1 giardin were among the newly identified and predicted to be located on the outer wall of G. duodenalis cysts. For the characterization of these two targets, we applied sequence analysis, prokaryotic expression, preparation of polyclonal antibodies, and determination of subcellular localization. Finally, based on β-giardin immunomagnetic beads were prepared using the polyclonal antibodies and tested for their enrichment efficiency. Immunomagnetic beads targeting β-giardin achieved 65% cyst enrichment efficiency in fecal samples, comparable to conventional methods. Clinical evaluation across 163 multi-host fecal samples (ferrets, Siberian tigers, red-crowned cranes) demonstrated concordance with nested PCR, successfully enriching cysts from PCR-positive specimens. The immunomagnetic beads method targeting β-giardin demonstrated effective G. duodenalis cyst enrichment in multi-host fecal samples. These results provide a proteomic framework for the cyst wall proteins of G. duodenalis, expanding the detection targets for G. duodenalis cysts. It also establishes a theoretical foundation for subsequent research on the composition and function of G. duodenalis cysts.

PPVs-based regulation of parasitic protozoa can provide a theoretical basis and direction for PPD prevention and control, although PPVs and PPV regulatory mechanisms remain unclear. In this review, we investigated the differences between PPVs and the unique properties of each virus regarding virus discovery, structures, and life cycles, focused on the Trichomonas vaginalis virus, Giardia lamblia virus, Leishmania RNA virus, and the Cryptosporidium parvum virus 1. Parasite infections affect human and animal health significantly and contribute to a major burden on the global economy. Parasitic protozoan viruses (PPVs) affect the protozoan parasites’ morphology, phenotypes, pathogenicity, and growth rates. This discovery provides an opportunity to develop a novel preventive and therapeutic strategy for parasitic protozoan diseases (PPDs). Currently, there is greater awareness regarding PPVs; however, knowledge of viruses and their associations with host diseases remains limited. Parasite-host interactions become more complex owing to PPVs; however, few studies have investigated underlying viral regulatory mechanisms in parasites. In this study, we reviewed relevant studies to identify studies that investigated PPV development and life cycles, the triangular association between viruses, parasites, and hosts, and the effects of viruses on protozoan pathogenicity. This study highlights that viruses can alter parasite biology, and viral infection of parasites may exacerbate the adverse effects of virus-containing parasites on hosts or reduce parasite virulence. PPVs should be considered in the prevention of parasitic epidemics and outbreaks, although their effects on the host and the complexity of the triangular association between PPVs, protozoans, and hosts remain unclear. IMPORTANCE PPVs-based regulation of parasitic protozoa can provide a theoretical basis and direction for PPD prevention and control, although PPVs and PPV regulatory mechanisms remain unclear. In this review, we investigated the differences between PPVs and the unique properties of each virus regarding virus discovery, structures, and life cycles, focused on the Trichomonas vaginalis virus, Giardia lamblia virus, Leishmania RNA virus, and the Cryptosporidium parvum virus 1. The triangular association between PPVs, parasitic protozoa, and hosts reveals the “double-edged sword” property of PPVs, which maintains a balance between parasitic protozoa and hosts in both positive and negative respects. These studies discuss the complexity of parasitic protozoa and their co-existence with hosts and suggest novel pathways for using PPVs as tools to gain a deeper understanding of protozoal infection and treatment.