Helminths can manipulate their host’s gut microbiota, with the expansion of the lactobacilli population being a common feature. This process profoundly influences host immunoregulation, yet the underlying mechanisms remain almost unknown. Using a tissue-dwelling helminth model (larval Echinococcus multilocularis) while validating key findings from other helminth infections, we show that helminths harness the antibacterial program of host innate immunity to transform the host gut microbiome and control gut microbiota-mediated immunity. Using multifaceted techniques, we elucidate that cathelicidin-related antimicrobial peptide (CRAMP), derived from the expanded CD11b+CD206+ macrophages rather than the intestinal epithelial cells, is the key component that enters into the gut ecological system and enhances the fitness of Lactobacillus by selectively killing gram-negative microbes like enterobacteria. Furthermore, through in vitro cell culturing and in vivo dietary intervention experiments, we demonstrate that this regulation from innate immunity is boosted via toll-like receptor signaling by helminth’s secretory products, which could be sufficiently tuned down by dietary vitamin D through its receptor and cyp27b1. Importantly, using microbiota-targeted treatment methods, we prove that this signaling bolsters gut microbiota-mediated host intestinal Foxp3+ Treg cell expansion and parasite survival and that therapies targeting this signaling are effective in treating infection. We outline a dietary micronutrient-dependent mechanism by which helminths leverage host innate immunity to edit the host gut microbiome and thereby control immunosuppression precisely.

Monieziasis is a prevalent issue in small ruminant husbandry, primarily caused by Moniezia expansa and M. benedeni in China. There is a critical need for highly sensitive methods for disease surveillance and prevention. In this study, we developed a visual assay combining recombinase polymerase amplification (RPA) with a lateral flow strip (RPA-LFD) for the rapid detection of Moniezia spp. in sheep fecal samples. Seven primer/probe sets were designed based on a specific fragment of the M. expansa β-tubulin gene (MTUB). The RPA-LFD assay performed optimally under reaction conditions of 39 ℃ for 15 min, with a primer-to-probe ratio of 4:0.6. The optimized method demonstrated high specificity for Moniezia spp., with no cross-reactivity with genomic DNA from other common gastrointestinal parasites in ruminant livestock. The detection limit was 10 copies/μL of plasmid DNA or 10 pg/μL of M. expansa genomic DNA per reaction. When compared to PCR using clinical and sheep-simulated samples, the RPA-LFD assay exhibited equivalent detection capability, achieving 95.7 % consistency (K value = 0.939, p < 0.001). These results suggest that the RPA-LFD method is a reliable and portable diagnostic tool for routine screening, monitoring, and rapid confirmation of monieziasis in sheep flocks, particularly in endemic areas and remote regions.

Liver diseases often coincide with dysregulated gut homeostasis and Streptococcus overgrowth, yet the underlying mechanisms remain unclear. Here, we study patients with liver echinococcosis and other liver conditions. We observe that these patients frequently exhibit a co-occurrence of an ectopic expansion of orally derived Streptococcus species implicated in intestinal inflammation, alongside a bile acid deficiency in the gut. This association is typically characterized by the reduction of 12-ketolithocholic acid (12-KetoLCA), which exerts potent membrane-disrupting activity. We show that liver disorders compromise gut resistance to oral microbes due to a loss of ecological control from bile acids, particularly 12-KetoLCA. This bile-acid-conferred gut barrier is regulated by cytochrome P450 enzymes and can be reconstituted through adeno-associated virus (AAV) gene therapy targeting these genes. Additionally, we reveal that supplementation with 12-KetoLCA prevents oral Streptococcus-driven gut inflammation through antibacterial activity. Our findings underscore the essential role of bile acids in maintaining the oral-gut barrier.

Helminths serve as principal regulators in modulating host immune responses, and their excretory-secretory proteins are recognized as potential therapeutic agents for inflammatory bowel disease. Nevertheless, our comprehension of the mechanisms underlying immunoregulation remains restricted. This investigation delves into the immunomodulatory role of a secretory protein serpin (Emu-serpin), within the larval stage of Echinococcus multilocularis. Our observations indicate that Emu-serpin effectively alleviates dextran sulfate sodium-induced colitis, yielding a substantial reduction in immunopathology and an augmentation of anti-inflammatory cytokines. Furthermore, this suppressive regulatory effect is concomitant with the reduction of gut microbiota dysbiosis linked to colitis, as evidenced by a marked impediment to the expansion of the pathobiont taxa Enterobacteriaceae. In vivo experiments demonstrate that Emu-serpin facilitates the expansion of M2 phenotype macrophages while concurrently diminishing M1 phenotype macrophages, alongside an elevation in anti-inflammatory cytokine levels. Subsequent in vitro investigations involving RAW264.7 and bone marrow macrophages reveal that Emu-serpin induces a conversion of M2 macrophage populations from a pro-inflammatory to an anti-inflammatory phenotype through direct inhibition. Adoptive transfer experiments reveal the peritoneal macrophages induced by Emu-serpin alleviate colitis and gut microbiota dysbiosis. In summary, these findings propose that Emu-serpin holds the potential to regulate macrophage polarization and maintain gut microbiota homeostasis in colitis, establishing it as a promising candidate for developing helminth therapy for preventing inflammatory diseases.

Human taeniasis, caused by Taenia tapeworms, is a global parasitic disease with significant implications for public health and food safety. These tapeworms can grow to considerable sizes and potentially impact the microecology of the host gut. Despite their importance, the effects of Taenia infection on host gut microbiota haven't been thoroughly investigated. In this study, we conducted a cross-sectional analysis of the gut microbiome in patients infected with Taenia asiatica (n = 87) compared to healthy controls (n = 79) in the Dali cohort, China. We also performed a longitudinal assessment of microbial changes following deworming in a subset of patients (n = 24). Our findings reveal a significant shift in gut microbial composition, characterized by increased alpha-diversity and an enrichment of Prevotella-driven enterotypes in infected patients compared to healthy controls. The stability of these microbial features post-deworming varied widely among individuals and was lower in those with lower initial alpha diversity and Prevotella-enterotype before deworming. We observed a significant depletion of Bifidobacterium species in infected individuals, regardless of enterotypes, and these prebiotics did not recover post-deworming. Metabolic network analysis and in vitro experiments suggest that the reduction of Bifidobacterium was linked to metabolic competition for ecological niches or nutrients, particularly stachyose, from other microbes rather than the parasitism itself. Furthermore, our machine learning analysis demonstrated that taxa associated with Bifidobacterium in stachyose metabolism could robustly predict infection but could not predict deworming. This study highlights the substantial impact of taeniasis on the human gut microbiome and overall gut health.

为了深入研究猪带绦虫丝氨酸蛋白酶抑制分子(Ts-serpin-2)对THP-1细胞炎性细胞因子分泌的调节作用,本实验通过RT-PCR从猪带绦虫成虫扩增获得Ts-serpin-2(TsM_000807300)的编码序列CDS,利用毕赤酵母表达Ts-serpin-2重组蛋白.利用发色底物特异性反应检测Ts-serpin-2蛋白对猪胰蛋白酶、胰弹性蛋白酶、牛α-糜蛋白酶、猪胃蛋白酶、木瓜酶、凝血酶和组织蛋白酶G的抑制效果.重组蛋白Ts-serpin-2处理THP-1细胞24 h,应用qRT-PCR和ELISA方法检测各炎性细胞因子差异表达水平.结果显示,真核酵母表达的重组蛋白Ts-serpin-2分子量约为48 kDa,具有蛋白酶抑制活性,对牛α-糜蛋白酶、猪胰弹性蛋白酶及猪胰蛋白酶的活性均有明显的抑制作用.重组蛋白Ts-serpin-2可抑制LPS活化的THP-1细胞促炎性细胞因子IL-1β、IL-6、IL-12α、IFN-γ和iNOS2 mRNA的转录水平,促进IL-4刺激的THP-1细胞抗炎性细胞因子IL-10的表达.ELISA结果显示,Ts-serpin-2能够抑制巨噬细胞分泌致炎因子TNF-α、IL-6和IFN-γ,刺激IL-10的分泌,与qRT-PCR检测结果基本一致.上述研究结果表明猪带绦虫Ts-serpin-2可通过调节宿主巨噬细胞分泌的炎性因子影响虫体入侵过程中宿主的免疫应答.

Tissue-dwelling helminths affect billions of people around the world. They are potent manipulators of the host immune system, prominently by promoting regulatory T cells (Tregs) and are generally associated with a modified host gut microbiome. However, the role of the gut microbiota in the immunomodulatory processes for these non-intestinal parasites is still unclear. In the present study, we used an extra-intestinal cestode helminth model-larval Echinococcus multilocularis to explore the tripartite partnership (host-helminth-bacteria) in the context of regulating colonic Tregs in Balb/c mice. We showed that larval E. multilocularis infection in the peritoneal cavity attenuated colitis in Balb/c mice and induced a significant expansion of colonic Foxp3(+) Treg populations. Fecal microbiota depletion and transplantation experiments showed that the gut microbiota contributed to increasing Tregs after the helminth infection. Shotgun metagenomic and metabolic analyses revealed that the gut microbiome structure after infection was significantly shifted with a remarkable increase of Lactobacillus reuteri and that the microbial metabolic capability was reprogrammed to produce more Treg cell regulator-short-chain fatty acids in feces. Furthermore, we also prove that the L. reuteri strain elevated in infected mice was sufficient to promote the colonic Treg frequency and its growth was potentially associated with T cell-dependent immunity in larval E. multilocularis infection. Collectively, these findings indicate that the extraintestinal helminth drives expansions of host colonic Tregs through the gut microbes. This study suggests that the gut microbiome serves as a critical component of anti-inflammation effects even for a therapy based on an extraintestinal helminth.

Long non-coding RNAs (lncRNAs) and messenger RNAs (mRNAs) play crucial roles in regulating various physiological and pathological processes. However, the role of lncRNAs and mRNAs in mediating the liver response during Toxocara canis infection remains incompletely understood. In the present study, the expression profile of lncRNAs and mRNAs was investigated in the liver of Beagle dogs infected by T. canis using high-throughput RNA sequencing. Compared with the control groups, 876 differentially expressed (DE) lncRNAs and 288 DEmRNAs were identified at 12 h post-infection (hpi), 906 DElncRNAs and 261 DEmRNAs were identified at 24 hpi, and 876 DElncRNAs and 302 DEmRNAs were identified at 36 days post-infection (dpi). A total of 16 DEmRNAs (e.g. dpp4, crp and gnas) were commonly identified at the three infection stages. Enrichment and co-localization analyses identified several pathways involved in immune and inflammatory responses during T. canis infection. Some novel DElncRNAs, such as LNC_015756, LNC_011050 and LNC_011052, were also associated with immune and inflammatory responses. Also, LNC_005105 and LNC_005401 were associated with the secretion of anti-inflammatory cytokines, which may play a role in the healing of liver pathology at the late stage of infection. Our data provided new insight into the regulatory roles of lncRNAs and mRNAs in the pathogenesis of T. canis and improved our understanding of the contribution of lncRNAs and mRNAs to the immune and inflammatory response of the liver during T. canis infection.

The small ubiquitin-like modifier (SUMO) plays important roles, with the SUMOylation pathway as one of its core components. In the present work, a single SUMO gene was initially identified from Taenia pisiformis and designated as TpSUMO. Bioinformatic analysis showed that the TpSUMO gene contained a 309 bp open reading frame (ORF), encoding 102 amino acids, and had a predicted molecular weight of ∼12 kDa. The amino acid sequence of TpSUMO was deduced and it shared 44.00% identity with human SUMO2 (HsSUMO2) and exhibited more than 97.78% identity with SUMOs from Taenia and Echinococcus. TpSUMO possessed a putative non-consensus site (FK11MG) within its N-terminus and a typical di-glycine (GG) motif at the C-terminus. Basic local alignment search tool (BLAST) analysis showed that only a single SUMO-related ortholog was present in each set of known genome data for fourteen tapeworm species. The precursor His-TpSUMO-FL, mature His-TpSUMO-GG and mutant His-TpSUMO-GGK11R proteins (∼18 kDa) were expressed in Escherichia coli Rosseta (DE3), and rabbit polyclonal anti-TpSUMO was generated with a high titer of 1.28 × 105. In vitro SUMOylation assay results showed that TpSUMO multimer formation in the His-TpSUMO-GG reaction could be catalyzed by the human SAE1/SAE2 and UBC9 conjugation system, but K11R mutation disrupted TpSUMO chain synthesis. Quantitative real-time PCR (qRT-PCR) further revealed that TpSUMO was ubiquitously expressed in different stages of T. pisiformis and in higher levels during an early development phase (day 14) of adult worms. Immunofluorescence localization showed that TpSUMO was detected in the bladder wall of cysticerci, in the testis in immature segment, and within eggs in the gravid proglottids. These findings indicated that TpSUMO is a new member of the SUMO protein family and may play a vital role in regulation of functions within proteins involved in worm growth and development.

Helminth infection affects over 1 billion people worldwide. However, its relationship with the gut mycobiome remains unknown.

Blastocystis is a common human intestinal protozoan parasite. Little is known about its prevalence in echinococcosis. This study tested whether Echinococcus multilocularis infection would increase host susceptibility to Blastocystis. A total of 114 fecal samples (68 hydatid disease patients and 46 healthy people) were collected from Tibetans in the Qinghai province in China. The presence of Blastocystis was identified by sequencing of the small subunit (SSU) rRNA gene. Balb/c mice were co-infected with Blastocystis and E. multilocularis and tested for host susceptibility to Blastocystis. The overall Blastocystis prevalence was 12.3%; 16.2% in the patients and 4.4% in healthy people (p < 0.05). Sequence analysis identified three known Blastocystis genotypes, including ST1, ST2, and ST3, and one unknown genotype. Experimental dual infection significantly reduced mouse survival rate (20%), induced more severe signs, and increased intestinal damages with a higher intestinal colonization level of Blastocystis. The mouse model showed that E. multilocularis infection increases host susceptibility to Blastocystis. Our study shows a significantly higher prevalence of Blastocystis in patients with liver echinococcosis and reveals that non-intestinal E. multilocularis infection increases host susceptibility to the Blastocystis. Our results highlight that E. multilocularis infection is associated with Blastocystis. These findings remind us that more attention should be paid to the gut health of the patients with a helminth infection during clinical patient care.

目的 建立豆状囊尾蚴体外长期培养方法,并对其培养分泌产物进行鉴定.方法 将豆状带绦虫虫卵经口感染新西兰白兔(2 000枚/只),感染后3个月,从感染兔腹腔中收集豆状囊尾蚴.将虫体随机分为PBS组、RPMI1640组、胆汁组(RPMI1640+10％兔胆汁)和血清组(RPMI1640+10％无外泌体胎牛血清),10个/组,37℃、5％CO2培养后5min、1h、2h、12h、24 h、36 h、48 h及其后每天进行观察,记录豆状囊尾蚴头节翻出情况、虫体活力、体外存活时间及形态改变等,筛选适宜的培养条件.取50个幼虫在细胞瓶(25 cm2)中按筛选出的培养条件培养,每隔48小时收集培养液离心浓缩,取上清,蛋白质免疫印迹(Western blotting)检测豆状带绦虫烯醇化酶(Tpeno)和Tp14-3-3蛋白的表达情况.收集豆状囊尾蚴培养上清,提取外泌体,分别与阴性兔血清、CD63抗体、抗Tpeno单克隆抗体1D7和抗Tp14-3-3多克隆抗体孵育45 min,再加入胶体金标记的IgG,透射电镜观察外泌体形态,免疫电镜检测其标记蛋白CD63、Tpeno和Tp14-3-3表达情况.采用SPSS 20.0统计学软件进行数据分析,组间比较采用单因素方差分析.结果 培养前的豆状囊尾蚴呈椭圆形,有内凹的点状乳白色头节;PBS组可存活7d;RPMI 1640组可存活2个月;胆汁组存活时间最短,仅48h;血清组幼虫存活时间最长,可达3个月以上,高于其他3个组(P＜0.05).存活期内,PBS组、RPMI 1640组、胆汁组和血清组幼虫囊泡长度分别为(1.38±0.39)、(1.30±0.12)、(1.18±0.59)和(1.83±0.10)cm;宽度分别为(0.45±0.10)、(0.68±0.05)、(0.25±0.06)和(0.85±0.05)cm;血清组虫体囊泡长度和宽度与其余3组相比差异均有统计学意义(F长 度=7.58、65.93、7.11,F宽度=73.85、29.41、308.57,P＜0.05 或P＜0.01).培养 12 h 时,PBS组、RPMI 1640组、胆汁组和血清组幼虫头节翻出率分别为(33.3±5.8)％、(20.0±0.0)％、(100.0±0.0)％、(13.3±5.8)％,其中血清组与PBS和胆汁组头节翻出率差异有统计学意义(F=18.00、676.00,P＜0.01).对各组培养效果比较显示,血清组的培养液(RPMI 1640+10％无外泌体胎牛血清)为最适培养液.SDS-PAGE电泳分析结果显示,利用RPMI 1640+10％无外泌体胎牛血清培养豆状囊尾蚴,可成功提取到虫体的代谢_分泌产物和外泌体蛋白.Western blotting分析结果显示,用特异性抗体检测可见Tpeno和Tp14-3-3阳性条带,相对分子质量(Mr)分别约47 000和28 000,与预期相符.透射电镜下豆状囊尾蚴外泌体大小不一,直径为50～150 nm,为圆形或椭圆形的囊泡.免疫电镜分析显示,阴性兔血清不能识别外泌体蛋白,未见胶体金颗粒标记;外泌体标志蛋白CD63、虫体特异性蛋白Tpeno和Tp14-3-3均为阳性表达,胶体金颗粒标记明显.结论 初步建立了豆状囊尾蚴体外培养体系,可连续培养豆状囊尾蚴至少3个月以上.采用该体外培养方法培养可在培养上清中成功提取豆状囊尾蚴的外泌体.

BackgroundAlveolar echinococcosis (AE), which is caused by larval Echinococcus multilocularis, is one of the world's most dangerous neglected diseases. Currently, no fully effective treatments are available to cure this disease.MethodsIn vitro protoscolicidal assay along with in vivo murine models was applied in repurposing drugs against AE. Genome-wide identification and homology-based modeling were used for predicting drug targets. RNAi, enzyme assay, and RNA-Seq analyses were utilized for investigating the roles in parasite survival and validations for the drug target.FindingsWe identified nelfinavir as the most effective HIV protease inhibitor against larval E. multilocularis. Once-daily oral administration of nelfinavir for 28 days resulted in a remarkable reduction in parasite infection in either immune-competent or immunocompromised mice. E. multilocularis DNA damage-inducible 1 protein (EmuDdi1) is predicted as a target candidate for nelfinavir. We proved that EmuDdi1 is essential for parasite survival and protein excretion and acts as a functionally active protease for this helminth. We found nelfinavir is able to inhibit the proteolytic activity of recombinant EmuDdi1 and block the EmuDdi1-related pathways for protein export. With other evidence of drug efficacy comparison, our results suggest that inhibition of EmuDdi1 is a mechanism by which this HIV proteinase inhibitor mediates its antiparasitic action on echinococcosis.InterpretationThis study demonstrates that nelfinavir is a promising candidate for treating echinococcosis. This drug repurposing study proves that the widely prescribed drug for AIDS treatment is potent in combating E. multilocularis infection and thus provides valuable insights into the development of single-drug therapy for highly prevalent co-infection between HIV and helminth diseases.FundingThis work was supported by the National Natural Science Foundation of China (31802179), the Natural Science Foundation of Gansu Province, China (No. 21JR7RA027), and the State Key Laboratory of Veterinary Etiological Biology (No. SKLVEB2021YQRC01).

Taenia pisiformis is one of the most widespread gastrointestinal parasites and its larvae (cysticercosis) causes significant economic loss to rabbit industry. No efficient drug is available for this disease to date. To better understand its genomics, we assembled a 211-Mb high quality genome of T. pisiformis at chromosome level with a scaffold N50 size of 20 Mbp. Totally, 12,097 protein-coding genes was predicted from the genome. Genome-level phylogenetic analysis confirmed the taxonomic affiliations with other tapeworms and revealed that T. pisiformis diverged from its closely related relative T. hydatigena ∼ 14.6 Mya. Comparative genomic analyses revealed that the T. pisiformis genome was characterized by adaptive features of strong positive selection signals from carbohydrate/lipid metabolism and body surface integrity, and of expanded gene families related to metabolism of amino acids and lipids. The high-quality genome of T. pisiformis constitutes a resource for the comparative genomics and for further applications in general parasitology.

主要研究猪带绦虫丝氨酸蛋白酶抑制剂Ts-serpin-1(WormBase:TsM_000065700)对宿主THP-1细胞的免疫调节作用.通过设计特异性引物和RT-PCR扩增技术,获得Ts-serpin-1编码序列,用qRT-PCR分析Ts-serpin-1基因在猪带绦虫成虫和中绦期幼虫的表达情况;构建pCold-Ts-serpin-1原核表达载体,诱导表达纯化重组蛋白Ts-serpin-1;用重组蛋白Ts-serpin-1处理THP-1细胞,采用qRT-PCR和ELISA方法检测Ts-serpin-1处理THP-1细胞后,各炎性细胞因子的变化情况.结果显示:获得的Ts-serpin-1目的基因长度为1149 bp,编码382个氨基酸,含有Serpin家族特有的反应中心环.Ts-serpin-1基因在猪带绦虫成虫和中绦期幼虫均表达,且成虫表达量显著高于幼虫.重组蛋白Ts-serpin-1的分子质量约为43ku,可抑制THP-1细胞促炎性细胞因子IL-6、IL-1β、IL-12、TNF-α、IFN-y和iNOS2的表达,促进抗炎性细胞因子IL-10和TGF-β的分泌表达.以上结果提示,Ts-serpin-1在寄生虫-宿主互作过程中可能发挥重要作用.

为阐明猪带绦虫(Taenia solium)丝氨酸蛋白酶抑制剂(Tsserpin570)对蛋白酶的抑制作用,通过RT-PCR从猪带绦虫成虫cDNA扩增获得Tsserpin570(TsM_000807300)的完整CDS序列,并构建了 pCold-Tsserpin570原核表达载体,利用发色底物法检测可溶性重组蛋白Tsserpin570对蛋白酶活性的抑制作用.结果显示:RT-PCR扩增获得的Tsserpin570基因片段长1 206 bp,其蛋白的分子质量为46 ku,含有serpin家族特有的反应中心环及DEEGAE和FIVDHPFLFFI家族保守序列.qRT-PCR结果显示,Tsserpin570基因在猪带绦虫成虫和囊尾蚴阶段均有表达,且在成虫的表达量显著高于囊尾蚴的.pCold-Tsserpin570原核表达载体经IPTG诱导表达后获得可溶性重组蛋白Tsserpin570,可被猪囊尾蚴阳性血清识别.基于发色底物法检测Tsserpin570对牛α-胰糜蛋白酶、猪胰弹性蛋白酶、猪胰蛋白酶、人白细胞组织蛋白酶G、人血浆凝血酶、猪胃蛋白酶和木瓜蛋白酶等蛋白酶的活性抑制作用发现,其对牛α-胰糜蛋白酶、胰蛋白酶及弹性蛋白酶的活性均有明显的抑制作用.以上结果提示,Tsserpin570对多种丝氨酸蛋白酶均具有较强的抑制作用.

Taenia hydatigena is a widespread gastrointestinal helminth that causes significant health problems in livestock industry. This parasite can survive in a remarkably wide range of intermediate hosts and affects the transmission dynamics of zoonotic parasites. T. hydatigena is therefore of particular interest to researchers interested in studying zoonotic diseases and the evolutionary strategies of parasites. Herein we report a high-quality draft genome for this tapeworm, characterized by some hallmarks (e.g., expanded genome size, wide integrations of viral-like sequences and extensive alternative splicing during development), and specialized adaptations related to its parasitic fitness (e.g., adaptive evolutions for teguments and lipid metabolism). Importantly, in contrast with the evolutionarily close trematodes, which achieve gene diversification associated with immunosuppression by gene family expansions, in T. hydatigena and other cestodes, this is accomplished by alternative splicing and gene loss. This indicates that these two classes have evolved different mechanisms for survival. In addition, molecular targets for diagnosis and intervention were identified to facilitate the development of control interventions. Overall, this work uncovers new strategies by which helminths evolved to interact with their hosts.

Extracellular vesicles (EVs) from parasitic helminths play an important role in immunomodulation. However, EVs are little studied in the important parasite Fasciola gigantica. Here the ability of EVs from F. gigantica to induce cellular response to stress (reactive oxygen species generation, autophage and DNA damage response) in human intrahepatic biliary epithelial cells (HIBEC) was investigated. F. gigantica-derived EVs were isolated by ultracentrifugation, and identified with transmission electron microscopy, nanoparticle size analysis and parasite-derived EV markers. Internalization of EVs by HIBEC was determined by confocal immunofluorescence microscopy and flow cytometry. ROS levels in HIBEC were detected by molecular probing. EVs-induced autophagy and DNA-damaging effects were determined by evaluating expression levels of light chain 3B protein (LC3B), phosphor- H2A.X and phosphor-Chk1, respectively. Results revealed that EVs with sizes predominately ranging from 39 to 110 nm in diameter were abundant in adult F. gigantica and contained the parasite-derived marker proteins enolase and 14-3-3, and EVs were internalized by HIBEC. Further, uptake of EVs into HIBEC was associated with increased levels of reactive oxygen species, LC3Ⅱ, phosphor-H2A.X and phosphor-Chk1, suggesting EVs are likely to induce autophagy and DNA damage & repair processes. These results indicate F. gigantica EVs are associated with modulations of host cell responses and have a potential important role in the host-parasite interactions.

Polymorphonuclear neutrophils (PMNs) are the most abundant leukocytes and are among the first line of immune system defense. PMNs can form neutrophil extracellular traps (NETs) in response to some pathogens. The release of NETs plays an important role in trapping and killing invading parasites. However, the effects of NETs on parasitic trematode infections remain unclear. In the present study, water buffalo NET formation, triggered by the newly excysted juveniles (NEJs) of Fasciola gigantica, was visualized by scanning electron microscopy. The major components of the structure of NETs were characterized by immunofluorescence. Viability of flukes incubated with water buffalo PMNs were examined under light microscopy. The results revealed that F. gigantic juveniles triggered PMN-mediated NETs. These NETs were confirmed to comprise the classic characteristics of NETs: DNA, histones, myeloperoxidase and neutrophil elastase. Although NETs were formed in response to viable larvae, the larvae were not killed in vitro. These results suggest that NET formation may serve as a mechanism to hamper the migration of large larvae to facilitate immune cells to kill them. This study demonstrates, for the first time, that parasitic trematode juveniles can trigger NET formation.

Circulating miRNAs are stably existed in serum and plasma and can serve as a novel class of biomarkers for the diagnosis of helminthic infection. Fasciola gigantica, the causative agents of fascioliasis, live in the liver of in humans and ruminants, especially cattle, goat and sheep. In this study, a total of 121 host circulating miRNAs were differentially expressed (2 >= fold change, p < 0.05), of which 44 miRNAs were up-regulated and 77 miRNAs were significantly down-regulated. Consistent with the sequencing data, qRT-PCR results showed that the expression levels of bta-miR-21-5p and bta-miR-23a were elevated gradually and bta-miR-125a was decreased gradually at the F. gigantica infection time points. Four F. gigantica-specific miRNAs, including three known miRNAs (fgi-miR-87, fgi-miR-71, and fgi-miR-124), and one novel miRNA (novel miR-1) were identified in the sera of F. gigantica-infected buffaloes. Further analyses demonstrated that two parasite-derived miRNAs (fgi-miR-87 and fgi-miR-71) were specifically detected in sera of F. gigantica-infected buffaloes. These findings will be helpful to understand the roles of circulating miRNAs in host-parasite interaction and to potentiate serum miRNAs as diagnostic targets for F. gigantica.