Understanding the laminated layer of larval Echinococcus II: immunology

Histopathological assessment of the viability of hepatic alveolar echinococcosis

AIMS

Infections by the larval stage of the tape worms Echinococcus multilocularis and Echinococcus granulosus s.l. are potentially fatal zoonoses affecting humans as dead-end hosts. Histopathological evaluation of hepatic echinococcosis is an integral part of patient management, including the distinction between alveolar (AE) and cystic echinococcosis (CE), which are associated with different disease courses and treatments. To improve histopathological assessment of Echinococcus lesions, we aimed to develop robust criteria to evaluate their viability and decay.

METHODS AND RESULTS

Histomorphological criteria for determining parasitic viability based on the morphology of parasite structures and different stages of their decay were defined based on a clinically and molecularly defined cohort comprising 138 specimens from 112 patients (59 AE and 53 CE); 618 AE lesions were assessed for histopathological viability comparing haematoxylin and eosin (H&E) staining with mAbEm18 and mAbEm2G11 immunostaining. Moreover, parasite viability was systematically mapped in cross-sections of five additional AE lesions. Protoscoleces in CE and AE displayed variable states of degeneration. Albendazole had no significant effect on the morphology of parasite structures. Viability assessment revealed high agreement between H&E and mAbEm18, but not mAbEm2G11 staining, suggesting mAbEm18 staining as reliable for parasite viability assessment. H&E and mAbEm18 staining displayed a central-peripheral gradient of parasite viability and decay across parasitic lesions, with decayed cystic lesions located more towards the lesion centre while the most viable cystic lesions were located more peripherally.

CONCLUSIONS

Histopathological criteria corroborated by mAbEm18 staining provide a simple and reliable tool to assess the viability of AE lesions, knowledge of which is a valuable decision-making tool for further treatment.

Untargeted metabolomics to discriminate liver and lung hydatid cysts: Importance of metabolites involved in the immune response

The Echinococcus granulosus sensu lato species complex is responsible for the neglected zoonotic disease known as cystic echinococcosis (CE). Humans and livestock are infected via fecal-oral transmission. CE remains prevalent in Western China, Central Asia, South America, Eastern Africa, and the Mediterranean. Approximately one million individuals worldwide are affected, influencing veterinary and public health, as well as social and economic matters. The infection causes slow-growing cysts, predominantly in the liver and lungs, but can also develop in other organs. The exact progression of these cysts is uncertain. This study aimed to understand the survival mechanisms of liver and lung CE cysts from cattle by determining their metabolite profiles through metabolomics and multivariate statistical analyses. Non-targeted metabolomic approaches were conducted using quadrupole-time-of-flight liquid chromatography/mass spectrometry (LC-QTOF-MS) to distinguish between liver and lung CE cysts. Data processing to extract the peaks on complex chromatograms was performed using XCMS. PCA and OPLS-DA plots obtained through multiple statistical analyses showed interactions of metabolites within and between groups. Metabolites such as glutathione, prostaglandin, folic acid, and cortisol that cause different immunological reactions have been identified both in liver and lung hydatid cysts, but in different ratios. Considering the differences in the metabolomic profiles of the liver and lung cysts determined in the present study will contribute research to enlighten the nature of the cyst and develop specific therapeutic strategies.

The Acute Inflammatory Potential of Particles From the Echinococcus granulosus Laminated Layer Is Moderated by Its Calcium Inositol Hexakisphosphate Component

Cystic echinococcosis is caused by the tissue-dwelling larva (hydatid) of Echinococcus granulosus sensu lato. A salient feature is that this larva is protected by the acellular laminated layer (LL). As the parasite grows, the LL sheds abundant particles that can accumulate in the parasite's vicinity. The potential of LL particles to induce inflammation in vivo has not been specifically analysed. It is not known how each of its two major components, namely highly glycosylated mucins and calcium inositol hexakisphosphate (InsP6) deposits, impacts inflammation induced by the LL as a whole. In this work, we show that LL particles injected intraperitoneally cause infiltration of eosinophils, neutrophils and monocytes/macrophages as well as the disappearance of resident (large peritoneal) macrophages. Strikingly, the absence of calcium InsP6 enhanced the recruitment of all the inflammatory cell types analysed. In contrast, oxidation of the mucin carbohydrates caused decreased recruitment of neutrophils. The carbohydrate-oxidised particles caused cell influx nonetheless, which may be explained by possible receptor-independent effects of LL particles on innate immune cells, as suggested by previous works from our group. In summary, LL particles can induce acute inflammatory cell recruitment partly dependent on its mucin glycans, and this recruitment is attenuated by the calcium InsP6 component.

Modulatory Effects of Hydatid Cyst Fluid on a Mouse Model of Experimental Autoimmune Encephalomyelitis

The reduced burden of helminth parasites in industrialized countries is probably one of the reasons for the increased prevalence of autoimmune disorders such as multiple sclerosis (MS). The current study aimed to evaluate the potential preventive effects of hydatid cyst fluid (HCF) on the disease severity in an EAE mouse model of MS. EAE-induced mice were treated with HCF before and after EAE induction. An RT-PCR-based evaluation of IFN-γ, IL-1β, TNF, T-bet, IL-4, GATA3, IL-17, RoRγ, TGF-β, and FOXP3 expression levels in splenocytes and an ELISA-based analysis of IFN-γ and IL-4 levels in cell culture supernatant of splenocytes were performed. Histopathological examinations of mice during the study were also conducted. The expression levels of T-bet, IL-4, GATA3, TGF-β, and FOXP3 in EAE + HCF mice were significantly higher compared to EAE + PBS mice. In the EAE + HCF group, the expression levels of IFN-γ, IL-1β, and TNF were significantly lower than in the EAE + PBS group. The histopathological results showed significantly reduced inflammation and demyelination in EAE + HCF mice compared to EAE + PBS mice. Our study provides proof-of-concept in the EAE mouse model of MS that helminth-derived products such as HCF have a potential prophylactic effect on MS development and present a novel potential therapeutic strategy.

Microbial evasion of the complement system: a continuous and evolving story

The complement system is a fundamental part of the innate immune system that plays a key role in the battle of the human body against invading pathogens. Through its three pathways, represented by the classical, alternative, and lectin pathways, the complement system forms a tightly regulated network of soluble proteins, membrane-expressed receptors, and regulators with versatile protective and killing mechanisms. However, ingenious pathogens have developed strategies over the years to protect themselves from this complex part of the immune system. This review briefly discusses the sequence of the complement activation pathways. Then, we present a comprehensive updated overview of how the major four pathogenic groups, namely, bacteria, viruses, fungi, and parasites, control, modulate, and block the complement attacks at different steps of the complement cascade. We shed more light on the ability of those pathogens to deploy more than one mechanism to tackle the complement system in their path to establish infection within the human host.

Echinococcus granulosus as a Promising Therapeutic Agent against Triplenegative Breast Cancer

Abstract:

Breast cancer is a major cause of cancer deaths in women, with approximately 1.2 million new cases per year. Current treatment options for breast cancer include surgery, radiation, hormone therapy, and chemotherapy. However, the non-selective cytotoxicity of chemotherapeutic agents often leads to severe side effects, while drug resistance can worsen patient outcomes. Therefore, the development of more effective and less toxic anticancer drugs is a critical need. This study aimed to review the literature on Echinococcus granulosus antigens with anticancer potential against triple-negative breast cancer. Recent studies have suggested that certain parasite antigens may have potential anticancer effects. Specifically, research has shown that echinococcosis, a disease caused by the parasitic cestode Echinococcus granulosus, may have a protective effect against cancer. These findings offer new insights into the potential use of E. granulosus antigens in the development of novel cancer therapies and tumor cell vaccines. The findings of recent studies suggested that E. granulosus antigens may have the potential to be used in effective and less toxic cancer treatments. However, further research is needed to fully understand the mechanisms behind the anticancer effects of these antigens and develop new cancer therapies and vaccines

Mucins Shed from the Laminated Layer in Cystic Echinococcosis Are Captured by Kupffer Cells via the Lectin Receptor Clec4F

Cystic echinococcosis is caused by the larval stages (hydatids) of cestode parasites belonging to the species cluster Echinococcus granulosus sensu lato, with E. granulosus sensu stricto being the main infecting species. Hydatids are bladderlike structures that attain large sizes within various internal organs of livestock ungulates and humans. Hydatids are protected by the massive acellular laminated layer (LL), composed mainly of mucins. Parasite growth requires LL turnover, and abundant LL-derived particles are found at infection sites in infected humans, raising the question of how LL materials are dealt with by the hosts. In this article, we show that E. granulosus sensu stricto LL mucins injected into mice are taken up by Kupffer cells, the liver macrophages exposed to the vascular space. This uptake is largely dependent on the intact mucin glycans and on Clec4F, a C-type lectin receptor which, in rodents, is selectively expressed in Kupffer cells. This uptake mechanism operates on mucins injected both in soluble form intravenously (i.v.) and in particulate form intraperitoneally (i.p.). In mice harboring intraperitoneal infections by the same species, LL mucins were found essentially only at the infection site and in the liver, where they were taken up by Kupffer cells via Clec4F. Therefore, shed LL materials circulate in the host, and Kupffer cells can act as a sink for these materials, even when the parasite grows in sites other than the liver.

Ex vivo Immuno-modulatory effect of Echinococcus granulosus laminated layer during allergic rhinitis and allergic asthma: A study in Algerian Patients

The effect of helminthic infections on allergic diseases and asthma is still inconclusive. Moreover, there is considerable evidence suggesting that nitric oxide (NO), metalloproteinases and pro-inflammatory cytokines play a significant role in the physiopathology of these diseases. In this sense, the aim of our study is to investigate the ex vivo immunomodulatory effect of the laminated layer (LL, outside layer of parasitic cyst) of the helminth Echinococcus granulosus on NO, IL-17A and IL-10 production. In the first step of our study, we evaluated in vivo the NO, MMP-9, IL-17A, IL-10 levels in Algerian patients with allergic asthma and allergic rhinitis and their changes in relation with exacerbation status of the patients. In the principal part of our work, we assessed NO, IL-10 and IL-17A levels in supernatants of patients PBMCs cultures before and after stimulation with LL. Our results indicate a significant reduction in NO production by PBMCs of patients with allergic rhinitis and allergic asthma whether mild, moderate or severe after stimulation with LL. Interestingly, LL induces a significant decrease in the production of NO and IL17-A levels as well as an increase in the production of IL-10 in the cultures performed with PBMC of patients with severe allergic asthma. Importantly, our data indicate that LL exert a down-modulatory effect on inflammatory mediators (NO, IL-17A) and up immune-regulatory effect on IL-10 production. Collectively, our study supports the hygiene hypothesis suggesting that Echinococcus granulosus infection like other helminths could prevent and/or modulate inflammation responses during inflammatory diseases.

Past and Present of Diagnosis of Echinococcosis: A Review (1999-2021)

The larval forms of taeniid cestodes belonging to the genus Echinococcus are the source of the zoonotic infection known as echinococcosis. Alveolar and cystic echinococcosis are caused by Echinococcus multilocularis and Echinococcus granulosus (s. s) respectively. It is endemic in several regions of the world. In this systematic review, we describe diagnosis, and the species (human, canids, livestock, and small rodents) affected by cystic (CE) and alveolar echinococcosis (AE). From 1999 to 2021, we searched the online directory through PubMed, SCOPUS, Web of Science, and google scholar. Among the 37,700 records found in the online databases, 187 publications met our eligibility requirements. The majority of investigations employed a range of diagnostic methods, such as ELISA, imaging, copro-PCR, necropsy or arecoline hydrobromide purgation, morphological cestode confirmation, and fecal sieving/flotation to detect and confirm Echinococcus infection. ELISA was the most commonly used method followed by PCR, and imaging. The research team retrieved data describing the incidence or assessment of the diagnostic test for E. multilocularis in humans (N = 99), canids (N = 63), small ruminants (N = 13), large ruminants (N= 3), camel (N= 2), pigs (N=2) and small mammals (N= 5). This study was conducted to explore the diagnostic tools applied to detect echinococcosis in humans as well as animals in prevalent countries, and to report the characteristic of new diagnostic tests for disease surveillance. This systematic review revealed that ELISA (alone or in combination) was the most common method used for disease diagnosis and diagnostic efficacy and prevalence rate increased when recombinant antigens were used. It is highly recommended to use combination protcols such as serological with molecular and imaging technique to diagnose disease. Our study identified scarcity of data of reporting echinococcosis in humans/ animals in low-income or developing countries particularly central Asian countries. Study reports in small rodents indicate their role in disease dissemination but real situation in these host is not refected due to limited number of studies. Even though echinococcosis affects both public health and the domestic animal sector, therefore, it is important to devise new and strengthe implementation of the existing monitoring, judging, and control measures in this estimate.

Proteomic profiling of hydatid fluid from pulmonary cystic echinococcosis

BACKGROUND

Most cystic echinococcosis cases in Southern Brazil are caused by Echinococcus granulosus and Echinococcus ortleppi. Proteomic studies of helminths have increased our knowledge about the molecular survival strategies that are used by parasites. Here, we surveyed the protein content of the hydatid fluid compartment in E. granulosus and E. ortleppi pulmonary bovine cysts to better describe and compare their molecular arsenal at the host-parasite interface.

METHODS

Hydatid fluid samples from three isolates of each species were analyzed using mass spectrometry-based proteomics (LC-MS/MS). In silico functional analyses of the identified proteins were performed to examine parasite survival strategies.

RESULTS

The identified hydatid fluid protein profiles showed a predominance of parasite proteins compared to host proteins that infiltrate the cysts. We identified 280 parasitic proteins from E. granulosus and 251 from E. ortleppi, including 52 parasitic proteins that were common to all hydatid fluid samples. The in silico functional analysis revealed important molecular functions and processes that are active in pulmonary cystic echinococcosis, such as adhesion, extracellular structures organization, development regulation, signaling transduction, and enzyme activity.

CONCLUSIONS

The protein profiles described here provide evidence of important mechanisms related to basic cellular processes and functions that act at the host-parasite interface in cystic echinococcosis. The molecular tools used by E. granulosus and E. ortleppi for survival within the host are potential targets for new therapeutic approaches to treat cystic echinococcosis and other larval cestodiases.

Evaluation of Allicin Against Alveolar Echinococcosis In Vitro and in a Mouse Model

Purpose

At present, the chemotherapy for alveolar echinococcosis (AE) is mainly based on albendazole (ABZ). However, more than 20% of patients fail chemotherapy. Therefore, new and more effective treatments are urgently needed. Allicin has been reported to have antibacterial and antiparasitic effects. The objectives of the present study were to investigate the in vivo and in vitro efficacy of allicin against Echinococcus multilocularis (E. multilocularis).

Methods

The effects of allicin on protoscolex survival and structural changes were evaluated in vitro. The 4-week-old BALB/c male mice used for in vivo modelling underwent inoculation of E. multilocularis protoscoleces by intraperitoneal injection, followed by intragastric administration of allicin for 6 weeks. Then, the effects of allicin on lymphocyte subsets, metacestode growth and host tissue matrix metalloproteinase 2 (MMP2)/MMP9 expression around metacestodes in mice were evaluated. The toxicity of allicin was further evaluated in vivo and in vitro.

Results

Att 40 μg/mL, allicin showed a killing effect on protoscoleces in vitro and treatment resulted in the destruction of protoscolex structure. Molecular docking showed that allicin could form hydrogen bonds with E. multilocularis cysteine enzymes. After 6 weeks of in vivo allicin treatment, the spleen index of mice was increased and the weight of metacestodes was reduced. Allicin increased the proportion of CD4⁺ T cells and decreased the proportion of CD8⁺ T cells in the peripheral blood and spleen. Pathological analysis of the metacestodes showed structural disruption of the germinal and laminated layers after allicin treatment. In addition, allicin inhibited the expression of MMP2 and MMP9 in metacestode-surrounding host tissues. At 160 μg/mL, allicin had no significant toxicity to normal hepatocytes but could inhibit hepatoma cell proliferation. At 30 mg/kg, allicin had no significant hepatorenal toxicity in vivo.

Conclusion

These results suggest that allicin exerts anti-E. multilocularis effects in vitro and in vivo and can enhance immune function in mice, with the potential to be developed as a lead compound against echinococcosis.

Echinococcus multilocularis specific antibody, systemic cytokine, and chemokine levels, as well as antigen-specific cellular responses in patients with progressive, stable, and cured alveolar echinococcosis: A 10-year follow-up

Background

The infestation with Echinococcus multilocularis larvae may persist in humans for up to decades without evident clinical symptoms. Longitudinal investigations are needed to understand the dynamic immunological processes in alveolar echinococcosis (AE) patients associated with an active and progressive, a stable or a regressive course of disease.

Methodology/Principal findings

This study evaluated the E. multilocularis specific antibody responses, systemic cytokine, and chemokine serum levels over a 10-year follow-up period, as well as cellular responsiveness in AE patients. Our results demonstrate a rapid decrease in antibodies against E. multilocularis specific antigen Em2+. Especially in cured patients, these antibodies remained negative, making them a significant predictor for cured AE. E. multilocularis specific IgG4, and indirect hemagglutination IHA decreased later in time, after around 5 years. While total IgE did not show significant dynamics over the course of disease, E. multilocularis specific IgE decreased after one to two years, and increasing levels were a significant predictor of progressive disease. There was no significant change in systemic IL-8, IL-9, CCL18 or CCL20 serum levels over time. Univariate analysis across groups indicated lower IL-8 levels in cured patients; however, this result could not be confirmed by multivariate analysis. Levels of CCL17 decreased during treatment, especially in cured patients, and thus might serve as a predictive or risk factor for progressive disease. Levels of IL-10 and CCL13 decreased during disease, especially after five and ten years of intervention. The E. multilocularis antigen (EmAg) inducible cellular productions of MCP1(CCL13), TARC(CCL17) and PARC(CCL18) were lowest in patients with cured AE and infection-free controls, while the EmAg inducible cellular production of IFN-γ increased after cure. Significant positive cytokine and chemokine correlations were observed in AE patients for IL-9, IL-10, CCL13(MCP-4), CCL17(TARC) and CCL20(LARC)(for all p<0.001). E. multilocularis specific IgG4 response correlated positively with TARC (p<0.001). Both markers enhanced over time in progressive disease and decreased after cure. The levels of IL-8, IL-10, MCP4 and LARC enhanced with AE regression.

Conclusions/Significance

Repeated biomarker surveys are advisable to evaluate progression or regression of disease during longitudinal follow-up and such analyses can support imaging techniques and improve staging of AE patients.

Alveolar echinococcosis (AE) is a severe disease caused by Echinococcus multilocularis, the fox tapeworm. Humans exposed to E. multilocularis may develop severe AE with progressive tissue and organ infiltrating growth of the larval stage. The E. multilocularis larvae appear to have developed effective immune evasion mechanisms which facilitate an asymptomatic incubation and an extended host and parasite coexistence for decades. Over a 10-year follow-up, this investigation aimed to gain a better understanding of the immunological process associated with an active and progressive, a stable or a regressive course of AE. In summary, the rapid decrease of antibodies against the E. multilocularis specific antigen Em2+, especially in cured patients, makes them a significant predictor for cured AE. The positive relation of E. multilocularis specific IgG4 responses and chemokine levels of TARC can indicate AE progression when both enhance over time. Enhanced levels of cytokines IL-8, IL-10, and chemokines MCP4 and LARC may predict AE regression. Repeated biomarker surveys are advisable to evaluate progression or regression of AE during longitudinal follow up, and such analyses can support imaging techniques and improve staging of AE patients.

Ultrastructural characterization of the tegument in protoscoleces of Echinococcus ortleppi

Cystic echinococcosis is a globally distributed zoonosis caused by cestodes of the Echinococcus granulosus sensu lato (s.l.) complex, with Echinococcus ortleppi mainly involved in cattle infection. Protoscoleces show high developmental plasticity, being able to differentiate into either adult worms or metacestodes within definitive or intermediate hosts, respectively. Their outermost cellular layer is called the tegument, which is important in determining the infection outcome through its immunomodulating activities. Herein, we report an in-depth characterization of the tegument of E. ortleppi protoscoleces performed through a combination of scanning and transmission electron microscopy techniques. Using electron tomography, a three-dimensional reconstruction of the tegumental cellular territories was obtained, revealing a novel structure termed the 'tegumental vesicular body' (TVB). Vesicle-like structures, possibly involved in endocytic/exocytic routes, were found within the TVB as well as in the parasite glycocalyx, distal cytoplasm and close inner structures. Furthermore, parasite antigens (GST-1 and AgB) were unevenly localised within tegumental structures, with both being detected in vesicles found within the TBV. Finally, the presence of host (bovine) IgG was also assessed, suggesting a possible endocytic route in protoscoleces. Our data forms the basis for a better understanding of E. ortleppi and E. granulosus s.l. structural biology.

In vitro immunoregulatory activity and anti-inflammatory effect of Echinococcus granulosus laminated layer

The Laminated layer of Echinococcus granulosus (LL) is the outer layer of the hydatic cyst. It plays a pivotal role in protecting the metacestode from host immunity. In our current study, we investigated the immunomodulatory effect of the LL on mouse spleen cells in presence of Lipopolysaccharide (LPS). Mouse spleen cells were cultured with or without LL in presence of LPS. After 24 h, the nitrites level representative of Nitric oxide (NO) production was measured in the culture supernatant by Griess-modified method. In addition, the mRNA expression levels of cytokines (IFN-γ, IL-1β, TGF-β, IL-10), Foxp3, and CTLA-4 were measured by quantitative Real-Time Polymerase chain reaction (qRT-PCR). Interestingly, our results showed a significant decrease (p< 0.01) in NO production and IFN-γ mRNA level (p< 0.001) from LPS- induced spleen cells in response to LL after 24h of culture. Moreover, LPS induced high level of IL-1β that was significantly (p<0.05) down regulated by LL. Importantly, mRNA levels of TGF-β (p< 0.01), Foxp3 and IL-10 (p< 0.05) were significantly upregulated by LL. In conclusion, our data indicated the in vitro immuno-regulatory and anti-inflammatory effects of the hydatic Laminated Layer on mouse spleen cells. These effects are related to an innate response implicating up-regulation of Foxp3, IL-10 and TGF-β expression and down-regulation of IFN-γ and IL-1β expression. LL could constitute a potential candidate for controlling inflammation during inflammatory disease.

Primary pelvic echinococcosis though uncommon but not rare

Echinococcosis is caused by larva of Echinococcus granulosus. Liver being most commonly involved, other organs/body parts such as bone involvement is not so uncommon, especially in cattle-raising countries such as India. Primary osseous echinococcosis remains undiagnosed until complications have developed. We report a case of complicated pelvic echinococcosis presented with left gluteal mass, acetabulum and femoral head destruction, and reduced hip mobility. Pre- and postoperative chemotherapy with albendazole and en bloc surgical removal of the cyst were advocated as the preferred option of treatment. Primary osseous echinococcosis must be kept in mind when encountering a case of chronic bony mass not responding to antitubercular therapy, and hydatid serology should be performed along with other imaging and histopathological examinations to support or confirm the diagnosis to prevent long-term complications.

Hijacking Factor H for Complement Immune Evasion

The complement system is an essential player in innate and adaptive immunity. It consists of three pathways (alternative, classical, and lectin) that initiate either spontaneously (alternative) or in response to danger (all pathways). Complement leads to numerous outcomes detrimental to invaders, including direct killing by formation of the pore-forming membrane attack complex, recruitment of immune cells to sites of invasion, facilitation of phagocytosis, and enhancement of cellular immune responses. Pathogens must overcome the complement system to survive in the host. A common strategy used by pathogens to evade complement is hijacking host complement regulators. Complement regulators prevent attack of host cells and include a collection of membrane-bound and fluid phase proteins. Factor H (FH), a fluid phase complement regulatory protein, controls the alternative pathway (AP) both in the fluid phase of the human body and on cell surfaces. In order to prevent complement activation and amplification on host cells and tissues, FH recognizes host cell-specific polyanionic markers in combination with complement C3 fragments. FH suppresses AP complement-mediated attack by accelerating decay of convertases and by helping to inactivate C3 fragments on host cells. Pathogens, most of which do not have polyanionic markers, are not recognized by FH. Numerous pathogens, including certain bacteria, viruses, protozoa, helminths, and fungi, can recruit FH to protect themselves against host-mediated complement attack, using either specific receptors and/or molecular mimicry to appear more like a host cell. This review will explore pathogen complement evasion mechanisms involving FH recruitment with an emphasis on: (a) characterizing the structural properties and expression patterns of pathogen FH binding proteins, as well as other strategies used by pathogens to capture FH; (b) classifying domains of FH important in pathogen interaction; and (c) discussing existing and potential treatment strategies that target FH interactions with pathogens. Overall, many pathogens use FH to avoid complement attack and appreciating the commonalities across these diverse microorganisms deepens the understanding of complement in microbiology.

Molecular characterization and serodiagnostic potential of Echinococcus granulosus hexokinase

Background

Cystic echinococcosis (CE), caused by the larval stage of Echinococcus granulosus (sensu stricto), is a life-threatening but neglected zoonosis. Glycolytic enzymes are crucial molecules for the survival and development of E. granulosus. The aim of this study was to investigate the molecular characterization, immunogenicity, tissue distribution and serodiagnostic potential of E. granulosus hexokinase (EgHK), the first key enzyme in the glycolytic pathway.

Methods

EgHK was cloned and expressed in Escherichia coli. Specific serum antibodies were evaluated in mice immunized with recombinant EgHK (rEgHK). The location of EgHK in the larval stage of E. granulosus was determined using fluorescence immunohistochemistry, and the potential of rEgHK as a diagnostic antigen was investigated in patients with CE using indirect enzyme-linked immunosorbent assay (ELISA).

Results

Recombinant EgHK could be identified in the sera of patients with CE and in mouse anti-rEgHK sera. High titers of specific immunoglobulin G were induced in mice after immunization with rEgHK. EgHK was mainly located in the tegument, suckers and hooklets of protoscoleces and in the germinal layer and laminated layer of the cyst wall. The sensitivity and specificity of the rEgHK-ELISA reached 91.3% (42/46) and 87.8% (43/49), respectively.

Conclusions

We have characterized the sequence, structure and location of EgHK and investigated the immunoreactivity, immunogenicity and serodiagnostic potential of rEgHK. Our results suggest that EgHK may be a promising candidate for the development of vaccines against E. granulosus and an effective antigen for the diagnosis of human CE.

Establishing and evaluation of a polymerase chain reaction for the detection of Echinococcus multilocularis in human tissue

BACKGROUND

Alveolar echinococcosis (AE) is caused by metacestode larva of the tapeworm Echinococcus multilocularis. AE diagnostics currently rely on imaging techniques supported by serology, but unequivocal detection of AE is difficult. Although polymerase chain reaction (PCR)-based methods to detect tapeworm DNA in biopsies have been suggested for several species, no validated protocol adhering to accepted guidelines has so far been presented for AE diagnostics. We herein established a PCR protocol for metacestode biopsies and technically evaluated the method using isolated parasite DNA and cells, biopsies of clinically relevant material, and formalin fixed paraffin-embedded (FFPE) human tissue blocks. We compared the results with an immunochemical (IHC) approach using the monoclonal antibody Em2G11 specific for the antigen Em2 of E. mulitlocularis.

METHODOLOGY/PRINCIPAL FINDINGS

Based on tapeworm 12S rDNA sequences we established and validated a PCR protocol for robust detection of as little as 50 parasite cells per specimen and report 127 cases of positive identification of Echinococcus species in samples from humans and animals. For further validation, we analyzed 45 liver, heart, brain, and soft tissue samples as well as cytological probes of aspirates of FFPE-material from 18 patients with clinically confirmed AE. Of each patient we analyzed (i) fully viable lesions with laminated layer; (ii) tissue with mAbEm2G11-positive small particles of E. multilocularis (spems); (iii) mAbEm2G11-negative tissue adjacent to the main lesion; and (iv) lymph node tissue with mAbEm2G11-positive spems. To identify the areas for the PCR-based approach, we performed IHC-staining with the monoclonal antibody Em2G11. Micro-dissected tissue of these areas was then used for PCR-analysis. 9 of 15 analyzed samples with viable E. multilocularis lesions with laminated layer were positive by PCR. Of this group, all samples preserved for less than 6 years (6/6) were tested positive. 11 of 15 samples of spems and 7 of 9 samples of the control group mAbEm2G11-negative tissue were negative by PCR. We further show that all probes from lymph nodes with spems are PCR negative.

CONCLUSIONS/SIGNIFICANCE

We present a sensitive PCR method for the detection of E. multilocularis in human tissue, particularly in fresh biopsy material and tissue blocks stored for less than 5 years. While the diagnostic sensitivity of material containing only spems was higher using IHC, PCR detection was possible in IHC negative liver tissue and in patients with negative serology. Our results support the view that spems do not contain parasitic DNA or viable cells of the parasite. spems thus most probably do not directly contribute to metastasis formation during AE.

Fasciola hepatica co-infection enhances Th1 immune response in the adventitial layer of non-fertile Echinococcus granulosus cysts

Cystic echinococcosis is a widespread zoonosis caused by the larval stage of the tapeworm Echinococcus granulosus. In intermediary hosts, two types of echinococcal cysts can be found: fertile, which produce protoscoleces, the infective form of the parasite to dogs; and infertile, that do not present protoscoleces and therefore are not able to continue with the parasite life cycle. The adventitial layer, the local immune response against the cyst, plays an important role in cyst fertility. Grazing cattle can often feature Fasciola hepatica co-infection, a parasite known to modulate the host systemic immune response. In this work the cellular Th1/Th2 immune profiles were evaluated in the adventitial layer of fertile and non-fertile cysts with and without co-infection with Fasciola hepatica. Measuring with immunohistochemistry and qPCR in adventitial layer, we report that non-fertile cysts present higher levels of Th1 cytokines (IFN-γ (P < 0.0001) and TNF-α (P < 0.05)), and fertile cysts have higher levels of Th2 cytokines (IL-4 (P < 0.001)). Co-infection with Fasciola hepatica is associated with a decrease in the expression of IL-4 (P < 0.05) and an increase in the expression of IFN-γ (P < 0.0001) in the adventitial layer of fertile cysts. Non-fertile cysts were associated with higher levels of Th1 cytokines in the adventitial layer, with IFN-γ expression enhanced by F. hepatica co-infection (P < 0.0001), confirming that polyparasitism should be considered in the treatment and control of naturally infected cattle.

Cystic Echinococcosis: Clinical, Immunological, and Biomolecular Evaluation of Patients from Sardinia (Italy)

Cystic echinococcosis (CE), a zoonotic disease caused by the larval stage of the tapeworm Echinococcus granulosus sensu lato (s.l.), is a worldwide public health problem. Echinococcus granulosus sensu stricto (s.s.), associated with G1 and G3 genotypes, is endemic with high prevalence in the Mediterranean basin. The parasite's life cycle comprises definitive hosts (canids) and intermediate hosts (ruminants) and can occasionally involve humans. The main aim of this research was to confirm the diagnosis of 13 patients suspected of CE who presented different complications and needed the surgical removal of the cysts. We also wanted to understand and clarify more the diagnosis of echinococcosis in humans. For this purpose, the patients first underwent cyst evaluation by ultrasound (US), immunological analysis, and then total pericystectomy, followed by parasitological, histopathological, and molecular biology examinations of the cysts. US stadiated one CE1, one CE2, eight CE3b, one CE4, and two CE5; immunology evidenced nine positives; histopathology confirmed 11 CE cysts, of which 8 fertile presenting protoscoleces were identified as E. granulosus s.s. by molecular biology, genotyped as three G1 and four G3 by neighbor-joining (NJ) phylogenetic tree. In conclusion, the results showed that 11 patients were affected by E. granulosus s.s. G1 orG3, and 2 cystic neoformations were of non-parasitic origin.

Proteomic analysis of plasma exosomes from Cystic Echinococcosis patients provides in vivo support for distinct immune response profiles in active vs inactive infection and suggests potential biomarkers

The reference diagnostic method of human abdominal Cystic Echinococcosis (CE) is imaging, particularly ultrasound, supported by serology when imaging is inconclusive. However, current diagnostic tools are neither optimal nor widely available. The availability of a test detecting circulating biomarkers would considerably improve CE diagnosis and cyst staging (active vs inactive), as well as treatments and follow-up of patients. Exosomes are extracellular vesicles involved in intercellular communication, including immune system responses, and are a recognized source of biomarkers. With the aim of identifying potential biomarkers, plasma pools from patients infected by active or inactive CE, as well as from control subjects, were processed to isolate exosomes for proteomic label-free quantitative analysis. Results were statistically processed and subjected to bioinformatics analysis to define distinct features associated with parasite viability. First, a few parasite proteins were identified that were specifically associated with either active or inactive CE, which represent potential biomarkers to be validated in further studies. Second, numerous identified proteins of human origin were common to active and inactive CE, confirming an overlap of several immune response pathways. However, a subset of human proteins specific to either active or inactive CE, and central in the respective protein-protein interaction networks, were identified. These include the Src family kinases Src and Lyn, and the immune-suppressive cytokine TGF-β in active CE, and Cdc42 in inactive CE. The Src and Lyn Kinases were confirmed as potential markers of active CE in totally independent plasma pools. In addition, insights were obtained on immune response profiles: largely consistent with previous evidence, our observations hint to a Th1/Th2/regulatory immune environment in patients with active CE and a Th1/inflammatory environment with a component of the wound healing response in the presence of inactive CE. Of note, our results were obtained for the first time from the analysis of samples obtained in vivo from a well-characterized, large cohort of human subjects.

The immunotherapy with hMASP-2 DNA nanolipoplexes against echinococcosis in experimentally protoscolex-infected mice

Cystic echinococcosis (CE), a complex and neglected zoonotic infectious disease, is mainly caused by larval tapeworm Echinococcus granulosus with a worldwide distribution. For CE, an effective drug treatment is not yet available. The present study was conducted to evaluate the efficacy of hMASP-2-based immunotherapy against hydatid cysts by using murine model. Eighteen weeks after infection with 2000 viable protoscoleces intraperitoneally, the infected mice were treated with hMASP-2 DNA nanolipoplexes (pcDNA3.1-hMASP-2) and albendazole respectively. After six weeks treatment, a significant reduction in the weight of cysts was observed both in the pcDNA3.1-hMASP-2 group and albendazole group compared with the untreated group (P  <  0.05). The hMASP-2 DNA nanolipoplexes not only inhibited the development of germinal layer, but also induced the extensive degeneration and damage of the germinal layer cells. Furthermore, compared with the untreated group, the number of CD4⁺T cells and CD8⁺T cells and the level of serum IFN-γ were significantly increased (P < 0.05). The frequency of PD-1⁺T-cell subpopulations including CD4⁺PD-1⁺T cells and CD8⁺PD-1⁺T cells and the level of serum IL-4 were notably decreased (P < 0.05) in the pcDNA3.1-hMASP-2 treatment group. Therefore, the hMASP-2 DNA nanolipoplexes displayed an effective treatment for echinococcosis through inhibiting the development of cysts and up-regulatory T-cell immunity. This new hMASP-2-based immunotherapeutic strategy could be a potential alternative for the treatment of CE, but further studies are recommended to evaluate the full potential of these hMASP-2 DNA nanolipoplexes in the treatment of human CE.

Cattle co-infection of Echinococcus granulosus and Fasciola hepatica results in a different systemic cytokine profile than single parasite infection

E. granulosus is a cestode that causes Cystic Echinococcosis (CE), a zoonotic disease with worldwide presence. The immune response generated by the host against the metacestode induces a permissive Th2 response, as opposed to pro-inflammatory Th1 response. In this view, mixed Th2 and regulatory responses allow parasite survival. Overall, larval Echinococcus infections induce strong regulatory responses. Fasciola hepatica, another common helminth parasite, represents a major infection in cattle. Co-infection with different parasite species in the same host, polyparasitism, is a common occurrence involving E. granulosus and F. hepatica in cattle. ‘While it is known that infection with F. hepatica also triggers a polarized Th2/Treg immune response, little is reported regarding effects on the systemic immune response of this example of polyparasitism. F. hepatica also triggers immune responses polarized to the Th2/ Treg spectrum. Serum samples from 107 animals were analyzed, and were divided according to their infection status and Echinococcal cysts fertility. Cytokines were measured utilizing a Milliplex Magnetic Bead Panel to detect IFN-γ, IL-1, IL-2, IL-4, IL-6, IL-10, IL-12 and IL-18. Cattle infected only with F. hepatica had the highest concentration of every cytokine analyzed, with both 4.24 and 3.34-fold increases in IL-10 and IL-4, respectively, compared to control animals, followed by E. granulosus and F. hepatica co-infected animals with two-fold increase in IL-10 and IL-4, compared to control animals, suggesting that E. granulosus co-infection dampens the cattle Th2/Treg immune response against F. hepatica. When considering Echinococcal cyst fertility and systemic cytokine concentrations, fertile cysts had higher IFN-γ, IL-6 and IL-18 concentrations, while infertile cysts had higher IL-10 concentrations. These results show that E. granulosus co-infection lowers Th1 and Th2 cytokine serological concentration when compared to F. hepatica infection alone. E. granulosus infections show no difference in IFN-γ, IL-1, IL-2, IL-6 and IL-18 levels compared with control animals, highlighting the immune evasion mechanisms of this cestode.

Activation of the NLRP3 Inflammasome by Particles from the Echinococcus granulosus Laminated Layer

The interaction of dendritic cells and macrophages with a variety of rigid noncellular particles triggers activation of the NLRP3 inflammasome and consequent secretion of interleukin 1β (IL-1β). Noncellular particles can also be generated in the context of helminth infection, since these large pathogens often shed their outermost structures during growth and/or molting. One such structure is the massive, mucin-based, soft, flexible laminated layer (LL), which protects the larval stages of cestodes of the genus Echinococcus.

The interaction of dendritic cells and macrophages with a variety of rigid noncellular particles triggers activation of the NLRP3 inflammasome and consequent secretion of interleukin 1β (IL-1β). Noncellular particles can also be generated in the context of helminth infection, since these large pathogens often shed their outermost structures during growth and/or molting. One such structure is the massive, mucin-based, soft, flexible laminated layer (LL), which protects the larval stages of cestodes of the genus Echinococcus. We show that particles from the Echinococcus granulosus LL (pLL) trigger NLRP3- and caspase-1-dependent IL-1β in lipopolysaccharide (LPS)-primed mouse bone marrow-derived dendritic cells (BMDC). This response can be elicited by pLL too large for phagocytosis and nonetheless requires actin dynamics, Syk, and phosphatidylinositol 3-kinase (PI3K). These three requirements had already been observed in our previous study on the alteration by pLL of CD86, CD40, IL-10, and IL-12 responses to LPS in BMDC; however, we now show that these alterations are independent of NLRP3 and caspase-1. In other words, an initial interaction with particles requiring actin dynamics, Syk, and PI3K, but not phagocytosis, elicits both NLRP3-dependent and NLRP3-independent responses. Intraperitoneal injection of pLL induced IL-1β, suggesting that contact with LL materials induces IL-1β in the E. granulosus infection setting. Our results extend our understanding of NLRP3 inflammasome activation by noncellular particulate materials both to helminth-derived materials and to flexible/soft materials.

Combining Computed Tomography and Histology Leads to an Evolutionary Concept of Hepatic Alveolar Echinococcosis

Alveolar echinococcosis (AE) is caused by the intermediate stage of Echinococcus multilocularis. We aimed to correlate computed tomography (CT) data with histology to identify distinct characteristics for different lesion types. We classified 45 samples into five types with the Echinococcus multilocularis Ulm Classification for Computed Tomography (EMUC-CT). The various CT lesions exhibited significantly different histological parameters, which led us to propose a progression model. The initial lesion fit the CT type IV classification, which comprises a single necrotic area with the central located laminated layer, a larger distance between laminated layer and border zone, a small fibrotic peripheral zone, and few small particles of Echinococcus multilocularis (spems). Lesions could progress through CT types I, II, and III, characterized by shorter distances between laminated layer and border zone, more spems inside and surrounding the lesion, and a pronounced fibrotic rim (mostly in type III). Alternatively, lesions could converge to a highly calcified, regressive state (type V). Our results suggest that the CT types mark sequential stages of the infection, which progress over time. These distinct histological patterns advance the understanding of interactions between AE and human host; moreover, they might become prognostically and therapeutically relevant.

Transcriptomic Features of Echinococcus granulosus Protoscolex during the Encystation Process

Cystic echinococcosis (CE) is a zoonotic infection caused by Echinococcus granulosus larvae. It seriously affects the development of animal husbandry and endangers human health. Due to a poor understanding of the cystic fluid formation pathway, there is currently a lack of innovative methods for the prevention and treatment of CE. In this study, the protoscoleces (PSCs) in the encystation process were analyzed by high-throughput RNA sequencing. A total of 32,401 transcripts and 14,903 cDNAs revealed numbers of new genes and transcripts, stage-specific genes, and differently expressed genes. Genes encoding proteins involved in signaling pathways, such as putative G-protein coupled receptor, tyrosine kinases, and serine/threonine protein kinase, were predominantly up-regulated during the encystation process. Antioxidant enzymes included cytochrome c oxidase, thioredoxin glutathione, and glutathione peroxidase were a high expression level. Intriguingly, KEGG enrichment suggested that differentially up-regulated genes involved in the vasopressin-regulated water reabsorption metabolic pathway may play important roles in the transport of proteins, carbohydrates, and other substances. These results provide valuable information on the mechanism of cystic fluid production during the encystation process, and provide a basis for further studies on the molecular mechanisms of growth and development of PSCs.

Recent advances on innate immune pathways related to host-parasite cross-talk in cystic and alveolar echinococcosis

Cystic echinococcosis (CE) and alveolar echinococcosis (AE) are life-threatening parasitic infections worldwide caused by Echinococcus granulosus (sensu lato) and E. multilocularis, respectively. Very little is known about the factors affecting innate susceptibility and resistance to infection with Echinococcus spp. Although benzimidazolic drugs against CE and AE have definitively improved the treatment of these cestodes; however, the lack of successful control campaigns, including the EG95 vaccine, at a continental level indicates the importance of generating novel therapies. This review represents an update on the latest developments in the regulatory functions of innate immune pathways such as apoptosis, toll-like receptors (TLRs), and inflammasomes against CE and AE. We suggest that apoptosis can reciprocally play a bi-functional role among the host-Echinococcus metabolite relationships in suppressive and survival mechanisms of CE. Based on the available information, further studies are needed to determine whether the orchestrated in silico strategy for designing inhibitors and interfering RNA against anti-apoptotic proteins and TLRs would be effective to improve new treatments as well as therapeutic vaccines against the E. granulosus and E. multilocularis.

Arginase promotes immune evasion of Echinococcus granulosus in mice

BACKGROUND

Cystic echinococcosis is a chronic disease caused by infection with the larvae of Echinococcus granulosus. The parasite's ability to establish persistent infection is partly due to its evolving immune evasion strategies. One strategy may involve the protective effect of arginase, which impedes the control of pathogens or tumors, whereas it remains largely unknown during E. granulosus infection. Here, we analyzed whether arginase was produced in peritoneal cells and assessed its role in immunosuppression in mice infected with protoscoleces of E. granulosus.

METHODS

BALB/c mice injected with protoscoleces of E. granulosus were used to evaluate the expression of arginase (ARG) in mRNA and protein levels. The profiles of ARG-1 expression in peritoneal cells and CD3ζ expression in T cells from spleens were assessed at different time points (3, 6, 9 and 12 months post-infection) by flow cytometry. In vitro, peritoneal cells were co-cultured with purified T cells in a transwell system, and the levels of CD3ζ re-expression were compared by flow cytometry. Meanwhile, the changes of L-arginine and its related metabolites in serum were tested.

RESULTS

Compared to the control group, the peritoneal cells from infected mice showed higher levels of ARG-1 mRNA and protein, unchanged ARG-2 and iNOS. Enhanced ARG-1 expression was present in SSC^lowCD11b⁺F4/80⁺, CD11b⁺CD11c⁺, CD11b⁺Gr-1⁺Ly-6C⁺Ly-6G^-, CD11b⁺Gr-1⁺Ly-6C^-Ly-6G⁺, CD11b⁺Gr-1⁺ and CD11b⁺Ly-6G⁺ cells. The proportion of cells and the proportion of ARG-1 expression in corresponding cells exhibited a rising trend along with the extension of infection time, except for fluctuations in SSC^lowCD11b⁺F4/80⁺ and CD11b⁺CD11c⁺ cells at 12 months post-infection, whereas the expression of CD3ζ chain in CD4⁺ and CD8⁺ T cells showed a descending trend. Purified T cells showed declined re-expression of CD3ζ when co-cultured with peritoneal cells from infected mice, and CD3ζ was regenerated by supplement of L-arginine or arginase inhibitor BEC, rather than NOS inhibitor L-NMMA or catalase. Meanwhile, the concentrations of L-arginine, L-citrulline and NO decreased, and those of L-ornithine and urea increased in serum post-infection.

CONCLUSIONS

Our findings demonstrated that ARG-1 expression is enhanced in multiple myeloid cells from peritoneum and promotes immune evasion of E. granulosus in mice by inhibiting the expression of T cell receptor CD3ζ chain and antagonism against iNOS.

Particles from the Echinococcus granulosus Laminated Layer Inhibit CD40 Upregulation in Dendritic Cells by Interfering with Akt Activation

The larval stage of the cestode Echinococcus granulosus causes cystic echinococcosis in humans and livestock. This larva is protected by the millimeter-thick, mucin-based laminated layer (LL), from which materials have to be shed to allow parasite growth. We previously reported that dendritic cells (DCs) respond to microscopic pieces of the mucin gel of the LL (pLL) with unconventional maturation phenotypes, in the absence or presence of Toll-like receptor (TLR) agonists, including lipopolysaccharide (LPS).

The larval stage of the cestode Echinococcus granulosus causes cystic echinococcosis in humans and livestock. This larva is protected by the millimeter-thick, mucin-based laminated layer (LL), from which materials have to be shed to allow parasite growth. We previously reported that dendritic cells (DCs) respond to microscopic pieces of the mucin gel of the LL (pLL) with unconventional maturation phenotypes, in the absence or presence of Toll-like receptor (TLR) agonists, including lipopolysaccharide (LPS). We also reported that the presence of pLL inhibited the activating phosphorylation of the phosphatidylinositol 3-kinase (PI3K) effector Akt induced by granulocyte-macrophage colony-stimulating factor or interleukin-4. We now show that the inhibitory effect of pLL extends to LPS as a PI3K activator, and results in diminished phosphorylation of GSK3 downstream from Akt. Functionally, the inhibition of Akt and GSK3 phosphorylation are linked to the blunted upregulation of CD40, a major feature of the unconventional maturation phenotype. Paradoxically, all aspects of unconventional maturation induced by pLL depend on PI3K class I. Additional components of the phagocytic machinery are needed, but phagocytosis of pLL particles is not required. These observations hint at a DC response mechanism related to receptor-independent mechanisms proposed for certain crystalline and synthetic polymer-based particles; this would fit the previously reported lack of detection of molecular-level motifs necessary of the effects of pLL on DCs. Finally, we report that DCs exposed to pLL are able to condition DCs not exposed to the material so that these cannot upregulate CD40 in full in response to LPS.

Ultrastructural changes in hydatid cyst walls obtained from human cases, exposed to different therapeutic approaches

Recurrence of cystic echinococcosis as a result of treatment failure is frequently reported to cause a major problem in management of such serious parasitic infection. The deeply seated innermost germinal layer of hydatid cysts is a relatively delicate layer, yet responsible for viability maintenance of this parasitic stage. In this study, a trial was done to explore the ultrastructural changes in germinal and laminated layer of the hydatid cyst for the first time in human cases exposed to different therapeutic approaches which were done earlier to the final open surgical intervention. Four groups were included: group 1 did not receive any earlier form of treatment; group 2 was previously treated with only medical therapy; group 3 was treated with a single course of medical treatment, plus a single PAIR technique; group 4 was treated with multiple courses of medical treatment plus multiple PAIR techniques. Complete alteration of ultrastructural features of germinal and laminated layers were observed only with samples from group 4, indicating a kind of failure of the therapeutic approaches used in group, 1, 2, and 3, unless repeated in group 4 to achieve a real change regarding the fitness of the parasitic cystic lesions. Searching for more effective, safe, therapeutic method is highly recommended which may end the suffering of the affected patients.

Inefficient and abortive classical complement pathway activation by the calcium inositol hexakisphosphate component of the Echinococcus granulosus laminated layer

Persistent extracellular tissue-dwelling pathogens face the challenge of antibody-dependent activation of the classical complement pathway (CCP). A prime example of this situation is the larva of the cestode Echinococcus granulosus sensu lato, causing cystic echinococcosis. This tissue-dwelling, bladder-like larva is bounded by a cellular layer protected by the outermost acellular "laminated layer" (LL), to which host antibodies bind. The LL is made up of a mucin meshwork and interspersed nano-deposits of calcium inositol hexakisphosphate (calcium InsP₆). We previously reported that calcium InsP₆ bound C1q, apparently initiating CCP activation. The present work dissects CCP activation on the LL. Most of the C1 binding activity in the LL corresponded to calcium InsP₆, and this binding was enhanced by partial proteolysis of the mucin meshwork. The remaining C1 binding activity was attributable to host antibodies, which included CCP-activating IgG isotypes. Calcium InsP₆ made only a weak contribution to early CCP activation on the LL, suggesting inefficient C1 complex activation as reported for other polyanions. CCP activation on calcium InsP₆ gave rise to a dominant population of C3b deposited onto calcium InsP₆ itself that appeared to be quickly inactivated. Apparently as a result of inefficient initiation plus C3b inactivation, calcium InsP₆ made no net contribution to C5 activation. We propose that the LL protects the underlying parasite cells from CCP activation through the combined effects of inefficient permeation of C1 through the mucins and C1 retention on calcium InsP₆. This mechanism does not result in C5 activation, which is known to drive parasite-damaging inflammation.

In vitro efficacies of solubility-improved mebendazole derivatives against Echinococcus multilocularis

Recently, we introduced an epoxy group to mebendazole by a reaction with epichlorohydrin and obtained two isoforms, mebendazole C1 (M-C1) and mebendazole C2 (M-C2). The in vitro effects of mebendazole derivatives at different concentrations on Echinococcus multilocularis protoscoleces and metacestodes as well as cytotoxicity in rat hepatoma (RH) cells were examined. The results demonstrated that the solubility of the two derivatives was greatly improved compared to mebendazole. The mortality of protoscoleces in vitro reached to 70–80% after 7 days of exposure to mebendazole or M-C2, and M-C2 showed higher parasiticidal effects than mebendazole (P > 0.05). The parasiticidal effect of M-C1 was low, even at a concentration of 30 µm. The percentage of damaged metacestodes that were treated with mebendazole and M-C2 in vitro at different concentrations were similar, and M-C1 exhibited insignificant effects on metacestodes. Significant morphological changes on protoscoleces and metacestodes were observed after treatment with mebendazole and M-C2. In addition, the introduction of an epoxy group to mebendazole also reduced its cytotoxicity in RH cells. Our results demonstrate that the introduction of an epoxy group not only improved the solubility of mebendazole, but also increased its parasiticidal effects on E. multilocularis and reduced its cytotoxicity in RH cells.

Extracellular vesicles from Echinococcus granulosus larval stage: Isolation, characterization and uptake by dendritic cells

The secretion of extracellular vesicles (EVs) in helminth parasites is a constitutive mechanism that promotes survival by improving their colonization and adaptation in the host tissue. In the present study, we analyzed the production of EVs from supernatants of cultures of Echinococcus granulosus protoscoleces and metacestodes and their interaction with dendritic cells, which have the ability to efficiently uptake and process microbial antigens, activating T lymphocytes. To experimentally increase the release of EVs, we used loperamide, a calcium channel blocker that increases the cytosolic calcium level in protoscoleces and EV secretion. An exosome-like enriched EV fraction isolated from the parasite culture medium was characterized by dynamic light scattering, transmission electron microscopy, proteomic analysis and immunoblot. This allowed identifying many proteins including: small EV markers such as TSG101, SDCBP, ALIX, tetraspanins and 14-3-3 proteins; proteins involved in vesicle-related transport; orthologs of mammalian proteins involved in the immune response, such as basigin, Bp29 and maspardin; and parasite antigens such as antigen 5, P29 and endophilin-1, which are of special interest due to their role in the parasite-host relationship. Finally, studies on the EVs-host cell interaction demonstrated that E. granulosus exosome-like vesicles were internalized by murine dendritic cells, inducing their maturation with increase of CD86 and with a slight down-regulation in the expression of MHCII molecules. These data suggest that E. granulosus EVs could interfere with the antigen presentation pathway of murine dendritic cells inducing immunoregulation in the host. Further studies are needed to better understand the role of these vesicles in parasite survival and as diagnostic markers and new vaccines.

Human cystic echinococcosis, caused by chronic infection with the larval stage of Echinococcus granulosus, affects over 1 million people worldwide. This helminth parasite secretes numerous excretory/secretory products that are in contact with host tissues where it establishes hydatid cysts. In this study, we comprehensively characterized extracellular vesicles (EVs) from E. granulosus protoscoleces and metacestodes, and demonstrated for the first time that the exosome-like vesicles from helminths can interact with host dendritic cells and carry several immunoregulatory proteins. This study provides valuable data on cestode-host immune communication. Nevertheless, further research on EVs is needed to fully understand their role in the parasite-host interface and obtain new data concerning their function as therapeutic markers and diagnostic tools.

Therapeutic and immunoregulatory effects of water-soluble alkaloids E2-a from Sophora moorcroftiana seeds as a novel potential agent against echinococcosis in experimentally protoscolex-infected mice

Novel compounds and more efficient treatment options are urgently needed for the treatment of cystic echinococcosis (CE), which is caused by Echinococcus granulosus. The decoction of Sophora moorcroftiana (Fabaceae) has been used to treat parasitosis for years in traditional Tibetan medicine. The aim of this study was to screen insecticidal water-soluble alkaloids from S. moorcroftiana seeds and evaluate the therapeutic effects against CE and the immune response induced by the alkaloidal fraction. Low polarity compounds (E2-a) were isolated from water-soluble alkaloid (E2) and matrine and sophocarpine were identified as major components. The E2-a fraction was more effective against protoscoleces than other constituents from S. moorcroftiana. After 20 weeks of secondary infection with protoscoleces, mice were orally treated with E2-a (100 mg/kg/day) for 6 weeks to evaluate therapeutic and immunoregulatory activities. Compared with the untreated group, E2-a treatment induced a significant reduction in cyst weight (mean 2.93 g) (p < 0.05) and an impaired ultrastructural modification of the cyst. Interestingly, the application of E2-a resulted in a significant increased frequency of CD3⁺CD4⁺ T-cell subsets and decreased frequency of CD3⁺PD-1⁺ T-cell subsets, compared with protoscolece-infected mice without treatment. The E2-a fraction of S. moorcroftiana can inhibit the cyst development of CE and boost the specific immune response by reducing the expression of PD-1 and accelerate the cytokine secretion of antigen-specific T-cells. All data suggest the E2-a fraction from S. moorcroftiana seeds may be used as a new potential therapeutic option against E. granulosus infection.

Th1/Th2-type cytokine profile in C57 black mice inoculated with live Echinococcus granulosus protoscolices

BACKGROUND AND OBJECTIVE

Cystic echinococcosis (CE) is a widespread parasitic disease caused by infection with the larval stage of a tapeworm, Echinococcus granulosus. The immune response to hydatid cyst in intermediate hosts is a complex and contradictory issue. It is suggested that a Th2 response would favor the establishment of the parasite, whereas a Th1 response would be lethal for the parasite. Thus, the aim of the present study was to evaluate the levels of IL2, TNFα, and IFNγ as T helper (Th)1-type cytokines, IL4 as a Th2-type cytokine, and total IgG in C57/black mice inoculated with E. granulosus protoscoleces (PSCs).

MATERIALS AND METHOD

In this experimental study, six C57/black mice were intraperitoneally inoculated with live E. granulosus PSCs and a control group consist of six C57/black mice received normal saline. The quantitative concentrations of IL2, TNFα, IFNγ, and IL4 were determined in the first, second, fourth, eighth and 12th-week post inoculation in both case and control groups.

RESULTS

The results showed that at the early post-infection phase (3-4 weeks) the Th1-type cytokine profile was predominant, however the shift to Th2-type cytokine took place in the 4th week.

CONCLUSION

Based on the results of the present study, we can suggest that the shift from Th1 to Th2 reactivity may be associated with persistent of the disease because Th2 reactivity may be less effective than Th1 reactivity in countering the parasite.

A 53 KDa Glycan Antigen of Hydatid Cyst Wall May Involve in Evasion from Host Immune System

Background:

Recent studies have shown that similar host glycan antigens are expressed by helminths such as Echinococcus granulosus hydatid cysts to evade from host immune system. In this work to investigate these antigens further, immunological cross-reactivity between human sera and hydatid cyst wall antigens has been investigated.

Materials and Methods:

Hydatid cyst wall antigens were used in enzyme-linked immunosorbent assay and Western immunoblotting and probed with pooled sera of hydatidosis patients and healthy controls. Sodium metaperiodate treatment was used to investigate glycan antigens.

Results:

A band with molecular weight about 53 KDa reacted with both hydatid patients' sera and also normal human sera. It has been shown that this band was a glycan antigen.

Conclusions:

A 53 KDa glycan antigen of hydatid cyst wall that reacted with all human sera may have an important role for evasion from host immune system.

Immunohistochemical observation of local inflammatory cell infiltration in the host-tissue reaction site of human hydatid cysts

The aim of this study was to evaluate the pattern of local immune cell infiltration in human cystic echinococcosis (CE) by identifying the subtypes of immune cells using immunohistochemistry (IHC). Fifty surgically removed hydatid cyst samples and surrounding tissues were collected from patients referred to Al-Zahra Hospital, Isfahan, Iran. IHC was performed on the surrounding host tissue of hydatid cysts using anti-human CD3, CD19, CD8, CD4, CD68, CD56, Ki-67 and Foxp3 (forkhead box P3) antibodies. The results were then compared to hepatocellular carcinoma and chronic hepatitis. In the host-tissue reaction site of liver hydatid cysts, a distinct pattern of local immune cell response, which outwardly consisted of a pack of the fibrous elements, a layer of palisading macrophages, an eosinophil-containing layer and a layer of accumulated lymphocytes, was observed. However, in some cases there were no positive cells for CD56+ natural killer cells and Foxp3+ regulatory T cells. The CD3+ T cells were the predominant inflammatory cells in all groups, followed by CD19+ B cells. It can be concluded that different immune cells are involved in the local response to human hydatid cysts.

In vitro and in vivo effects of chitosan-praziquantel and chitosan-albendazole nanoparticles on Echinococcus granulosus Metacestodes

Cystic echinococcosis (CE), which is caused by the metacestode of Echinococcus granulosus, is one of the most important zoonoses affecting humans. Benzimidazoles (in particular albendazole) and praziquantel (PZQ) are effective against CE, but poor water solubility of these agents often leads to inadequate results. Here, we evaluate the effects of chitosan-albendazole (ChABZ) and chitosan-praziquantel (ChPZQ) nanoparticles as a new formulation on hydatid cysts both in vitro and in vivo. Developed microcysts in culture were treated with different concentrations of ChABZ and ChPZQ nanoparticles (either alone or in combination), and ABZ + PZQ suspension. The viability rate of microcysts was used to evaluate the drug efficacies. In addition, the prophylactic and therapeutic effects of the drugs were studied on infected DBA/2 mice. Transmission electron microscopy was used to observe the ultra-structural changes. The viability rate of microcysts and differences in cyst weights were compared by ANOVA, and the cyst numbers were compared using the Kruskal-Wallis test. The combination of ChABZ + ChPZQ nanoparticles was more effective than the ABZ + PZQ suspension in vitro (p < 0.05). In prophylaxy, a significant reduction was observed both in size and in number of the cysts in ChABZ + ChPZQ nanoparticle groups compared with the control group (p < 0.05). In the therapeutic stage, however, this treatment only reduced the cyst numbers. Degeneration of the microcysts treated with the drugs was evident in the ultra-structural imaging. Overall, the nanoparticulate drugs were more effective than their suspension counterparts, but further studies are recommended to evaluate the full potential of these nanoparticles in the treatment of human CE.

Efficacy of ursolic acid against Echinococcus granulosus in vitro and in a murine infection model

BACKGROUND

Cystic echinococcosis is a global public health problem; however, the drugs (albendazole and mebendazole) currently recommended by WHO for its treatment, have limited efficacy. Therefore, novel drugs are required to provide more choices for the treatment of this disease.

METHODS

The anthelmintic effects of ursolic acid (UA) were tested on Echinococcus granulosus protoscoleces, germinal cells and metacestodes in vitro. The in vivo efficacy of UA was investigated in mice following secondary infection with E. granulosus. Furthermore, the corresponding ultrastructural damage induced by UA was evaluated by electron microscopy.

RESULTS

In vitro, 45.95 ± 5.30% of protoscoleces were killed by UA at 40 μg/ml, while the growth of more than 90% of germinal cells was inhibited by UA at 10 to 40 μg/ml. The same effect was observed in metacestodes 7 days after treatment with UA at 10, 20 and 40 μg/ml, and more than 50% of metacestodes showed loss of integrity at the end of the experiment. In vivo, metacestode weight was significantly reduced following oral administration of UA at 200 and 100 mg/kg (39.5 and 38.3%, respectively). Additionally, ultrastructural damage, such as alternations in germinal cell morphology and formation of vacuoles and lipid granules were observed in parasites treated with UA in vitro, while detachment of the germinal layer from the laminated layer was also seen in metacestodes in vivo.

CONCLUSIONS

UA was demonstrated to exert parasiticidal activity against E. granulosus in vitro and in vivo, thus implicating UA as a potential anti-echinococcosis agent.

Immunology of cystic echinococcosis (hydatid disease)

BACKGROUND

The neglected disease cystic echinococcosis is caused by larval Echinococcus granulosus flatworms, which form bladder-like hydatid cysts in liver, lungs, and other organs.

SOURCES OF DATA

Published literature.

AREAS OF AGREEMENT

Establishing larvae are susceptible to antibody-dependent killing, as attested by successful animal vaccination, whereas once established they are partially protected by the so-called laminated layer. Host responses are Th2 dominated, with a Th1 component. Diagnostic antigens from cyst fluid are known, but responses appear absent in one-fifth of patients.

AREAS OF CONTROVERSY

Is evasion mainly based on induction of Th2 or regulatory responses by the parasite?

GROWING POINTS

The parasite induces regulatory responses. The laminated layer has immune-regulatory properties.

AREAS TIMELY FOR DEVELOPING RESEARCH

Develop tools for functional genomics; characterize immunologically interesting proteins suggested by genomic information; analyse infection in broader context of granulomatous responses; identify molecules secreted/excreted by intact larvae/cysts towards their outside, including diffusible immune-regulators.

Antibody response to glycan antigens of hydatid cyst fluid, laminated layer and protoscolex of Echinococcus granulosus

Background: Hydatid disease is characterized by long-term growth of hydatid cysts in the human. The glycan antigens have an important role in the immunology of hydatid cyst. In this study immunological reaction of host sera to different glycan antigens of the cyst, has been investigated.

Methods: The antibody responses were tested to glycoprotein and glycolipid of the laminated layer (LL), cyst fluid (CF) and protoscolex (PS) antigens of E. Granulosus using ELISA and western immunoblotting tests. Thin-layer chromatography and ß-elimination were used for glycan purification.

Results: Both hydatid cyst and normal human sera reacted with hydatid cyst fluid, protoscolices, laminated layer, glycoprotein and glycolipid antigens. The most antigen-antibody reaction was related to CF and PS antigens, and LL antigens had the minimal reaction with the sera. Thin layer chromatography (TLC) of the antigens showed presence of many glycan bands in the laminated layer.

Conclusion: The parasite may elaborate different glycan antigens in LL to evade host immune response.

Echinococcus-Host Interactions at Cellular and Molecular Levels

The potentially lethal zoonotic diseases alveolar and cystic echinococcosis are caused by the metacestode larval stages of the tapeworms Echinococcus multilocularis and Echinococcus granulosus, respectively. In both cases, metacestode growth and proliferation occurs within the inner organs of mammalian hosts, which is associated with complex molecular host-parasite interactions that regulate nutrient uptake by the parasite as well as metacestode persistence and development. Using in vitro cultivation systems for parasite larvae, and informed by recently released, comprehensive genome and transcriptome data for both parasites, these molecular host-parasite interactions have been subject to significant research during recent years. In this review, we discuss progress in this field, with emphasis on parasite development and proliferation. We review host-parasite interaction mechanisms that occur early during an infection, when the invading oncosphere stage undergoes a metamorphosis towards the metacestode, and outline the decisive role of parasite stem cells during this process. We also discuss special features of metacestode morphology, and how this parasite stage takes up nutrients from the host, utilizing newly evolved or expanded gene families. We comprehensively review mechanisms of host-parasite cross-communication via evolutionarily conserved signalling systems and how the parasite signalling systems might be exploited for the development of novel chemotherapeutics. Finally, we point to an urgent need for the development of functional genomic techniques in this parasite, which will be imperative for hypothesis-driven analyses into Echinococcus stem cell biology, developmental mechanisms and immunomodulatory activities, which are all highly relevant for the development of anti-infective measures.

Particles from the Echinococcus granulosus laminated layer inhibit IL-4 and growth factor-driven Akt phosphorylation and proliferative responses in macrophages

Proliferation of macrophages is a hallmark of inflammation in many type 2 settings including helminth infections. The cellular expansion is driven by the type 2 cytokine interleukin-4 (IL-4), as well as by M-CSF, which also controls homeostatic levels of tissue resident macrophages. Cystic echinococcosis, caused by the tissue-dwelling larval stage of the cestode Echinococcus granulosus, is characterised by normally subdued local inflammation. Infiltrating host cells make contact only with the acellular protective coat of the parasite, called laminated layer, particles of which can be ingested by phagocytic cells. Here we report that a particulate preparation from this layer (pLL) strongly inhibits the proliferation of macrophages in response to IL-4 or M-CSF. In addition, pLL also inhibits IL-4-driven up-regulation of Relm-α, without similarly affecting Chitinase-like 3 (Chil3/Ym1). IL-4-driven cell proliferation and up-regulation of Relm-α are both known to depend on the phosphatidylinositol (PI3K)/Akt pathway, which is dispensable for induction of Chil3/Ym1. Exposure to pLL in vitro inhibited Akt activation in response to proliferative stimuli, providing a potential mechanism for its activities. Our results suggest that the E. granulosus laminated layer exerts some of its anti-inflammatory properties through inhibition of PI3K/Akt activation and consequent limitation of macrophage proliferation.

Regulation of immunity by Taeniids: lessons from animal models and in vitro studies

Taeniidae is the largest family of the Cyclophyllidea order of parasites despite being composed of just two genera: Taenia spp and Echinococcus spp. These parasites are flatworms with a terrestrial life cycle, having an immature or larval stage called metacestode, which develops into the mature form within the intestine of the primary host after being consumed in raw or poorly cooked meat. Consumed eggs hatch into oncospheres, penetrate the intestinal walls and are transported via the bloodstream to later develop into metacestodes within the muscles and internal organs of secondary and sometimes primary hosts, thereby initiating the cycle again. Larval stages of both Taenia spp and Echinococcus spp are well known to produce tissue-dwelling, long-lasting infections; in this stage, these parasites can reach centimetres (macroparasites) and both genera may cause life-threatening diseases in humans. Establishing such long-term infections requires an exceptional ability to modulate host immunity for long periods of time. In this review, we analyse the immunoregulatory mechanisms induced by these tapeworms and their products, mainly discussing the importance of taeniid strategies to successfully colonize their hosts, such as antigen-presenting cell phenotype manipulation and the consequent induction of T-cell anergy, among others.