Transcriptional profiles of cytokine/chemokine factors of immune cell-homing to the parasitic lesions: a comprehensive one-year course study in the liver of E. multilocularis-infected mice

Immunology of a unique biological structure: the Echinococcus laminated layer

The larval stages of the cestode parasites belonging to the genus Echinococcus grow within internal organs of humans and a range of animal species. The resulting diseases, collectively termed echinococcoses, include major neglected tropical diseases of humans and livestock. Echinococcus larvae are outwardly protected by the laminated layer (LL), an acellular structure that is unique to this genus. The LL is based on a fibrillar meshwork made up of mucins, which are decorated by galactose-rich O-glycans. In addition, in the species cluster termed E. granulosus sensu lato, the LL features nano-deposits of the calcium salt of myo-inositol hexakisphosphate (Insp6). The main purpose of our article is to update the immunobiology of the LL. Major recent advances in this area are (i) the demonstration of LL "debris" at the infection site and draining lymph nodes, (ii) the characterization of the decoy activity of calcium Insp6 with respect to complement, (iii) the evidence that the LL mucin carbohydrates interact specifically with a lectin receptor expressed in Kupffer cells (Clec4F), and (iv) the characterization of what appear to be receptor-independent effects of LL particles on dendritic cells and macrophages. Much information is missing on the immunology of this intriguing structure: we discuss gaps in knowledge and propose possible avenues for research.

Enzymatic characteristics and preventive effect of leucine aminopeptidase against Echinococcus multilocularis

Alveolar echinococcosis, a parasitic zoonotic disease caused by the larval stage of Echinococcus multilocularis infection, is a global epidemic in Eurasia and North America. Leucine aminopeptidase (LAP) of the M17 peptidase family could act on an ideal target antigen in diagnosis and prevention of parasitic diseases (schistosomiasis, malaria, fascioliasis) because of its good immunogenicity. In this study, the bioinformatic and enzymatic characterizations of recombinant Echinococcus multilocularis LAP (rEm-LAP) were evaluated. A prokaryotic expression system for rEm-LAP protein was established and its immunogenicity and preventive efficacy were demonstrated in a BALB/c mice model. This is the first report about the LAP of Echinococcus multilocularis and with a 57.4 KD purified rEm-LAP protein successfully expressed by pCzn1-LAP in Escherichia coli BL-21 cells. Enzymatic analysis results showed optimal rEm-LAP activity at pH 9. Serum indirect ELISA demonstrated that rEm-LAP could induce a Th1 and Th2 mixed-type immunological response and produce high levels of IgG, IgG1, IgG2a, IgM, and IgA. Furthermore, serum IFN-γ and IL-4 secretion were increased compared with the control groups. Finally, vaccination with rEm-LAP significantly decreased both the number and size of the cysts in Echinococcus multilocularis metacestode infected mice model. The current study provides evidence that rEm-LAP could be a potential vaccine antigen of Echinococcus multilocularis.

Prognostic value of plasma IL-27 on biological viability of hepatic cystic echinococcosis

OBJECTIVES

To investigate potential biomarkers for distinguishing biological viability of hepatic cystic echinococcosis.

METHODS

Using Luminex assay we measured plasma concentrations of cytokine and chemokine in patients with active and non-active cysts (hepatic cystic echinococcosis (HCE), n = 47) and stable/progressive hepatic alveolar echinococcosis (HAE, n = 38), and in comparable infection-free volunteers (n = 48). Disease progression was staged according to the classification standard.

RESULTS

Compared with healthy controls, enhanced elevation was found of T helper 22 type cytokine interleukin (IL)-22 and chemokines Eotaxin, interferon-γ inducible protein-10, monocyte chemoattractant protein-1, and stromal cell-derived factor-1α concentrations in HAE patients, and IL-22, growth-related oncogene α, monocyte chemoattractant protein-1, regulated on activation normal T-expressed and secreted, and stromal cell-derived factor-1α concentrations in HCE patients (P < 0.05-0.001). For HCE patients, only IL-27 concentrations in non-active HCE were significantly lower than in active HCE. In logistic regression analysis, IL-27 <20.79 pg/mL was an independent risk factor for HCE biological viability with receiver operating characteristic analysis at a 44.23 pg/mL cut-off resulting in 0.72 area under the curve.

CONCLUSIONS

Our findings correlate multiple cytokine and chemokine secretion patterns in HAE and HCE patients with different disease progression stages. IL-27 could serve as a referring biomarker for distinguishing HCE biological viability and provide a preliminary foundation for clinical decision-making.

Identification of candidate biomarkers of liver hydatid disease via microarray profiling, bioinformatics analysis, and machine learning

Objectives

Liver echinococcosis is a severe zoonotic disease caused by Echinococcus (tapeworm) infection, which is epidemic in the Qinghai region of China. Here, we aimed to explore biomarkers and establish a predictive model for the diagnosis of liver echinococcosis.

Methods

Microarray profiling followed by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis was performed in liver tissue from patients with liver hydatid disease and from healthy controls from the Qinghai region of China. A protein–protein interaction (PPI) network and random forest model were established to identify potential biomarkers and predict the occurrence of liver echinococcosis, respectively.

Results

Microarray profiling identified 1152 differentially expressed genes (DEGs), including 936 upregulated genes and 216 downregulated genes. Several previously unreported biological processes and signaling pathways were identified. The FCGR2B and CTLA4 proteins were identified by the PPI networks and random forest model. The random forest model based on FCGR2B and CTLA4 reliably predicted the occurrence of liver hydatid disease, with an area under the receiver operator characteristic curve of 0.921.

Conclusion

Our findings give new insight into gene expression in patients with liver echinococcosis from the Qinghai region of China, improving our understanding of hepatic hydatid disease.

Impact of Albendazole on Cytokine and Chemokine Response Profiles in Echinococcus multilocularis-Inoculated Mice

Objective

Alveolar echinococcosis (AE) is a zoonosis caused by the larval stage of the metacestode Echinococcosis multilocularis with a tumor-like behavior in the targeted organ, especially in the liver. Surgery with albendazole is first-line modality for AE. Drug discontinuation is usually based upon the parasitic viability shown by the positron emission tomography (PET) scan. However, as a demanding and expensive method, it is not widely practiced in majority of the endemic regions. Further understanding on the cytokine and chemokine response profiles in AE patients may provide an interesting insight for potential markers in viability assessment.

Methods

Mice were inoculated with Echinococcus multilocularis intrahepatically to develop the hepatic AE murine model. Oral albendazole administration was then applied for three months after the first inoculation, and peripheral and regional immune cells including type 1 T helper cells (Th), Th2, Th17, regulatory T (Treg) cells, related cytokines, and chemokines were examined.

Results

The hepatic AE lesion was confirmed by ultrasound examination resulting in a successful rate of 70%. Among the 17 cytokines and chemokines detected, plasma levels of IL-23 were significantly higher in E. multilocularis-infected mice when compared to the control group; furthermore, more obvious increasing levels were found after albendazole treatment (p < 0.05). All chemokine levels other than eotaxin and MCP-3 were slightly higher in E. multilocularis-infected mice compared to the control group (p > 0.05). Eotaxin levels were significantly decreased in mice with E. multilocularis infection followed by albendazole treatment (p < 0.05). Both IL-17A and IL-23 expressions in hepatic AE lesions were significantly higher and related with disease activity.

Conclusion

Albendazole administration influenced the balance of immune response and promotes the secretion of proinflammatory factors which is beneficial to parasite clearance. IL-23 seems to be associated with the successful albendazole treatment in mice with E. multilocularis infection; such a change could be translated into clinical application in the near future.

Dual Role of Hepatic Macrophages in the Establishment of the Echinococcus multilocularis Metacestode in Mice

Echinococcus multilocularis larvae, predominantly located in the liver, cause a tumor-like parasitic disease, alveolar echinococcosis (AE), that is characterized by increased infiltration of various immune cells, including macrophages, around the lesion that produces an "immunosuppressive" microenvironment, favoring its persistent infection. However, the role of hepatic macrophages in the host defense against E. multilocularis infection remains poorly defined. Using human liver tissues from patients with AE and a hepatic experimental mouse model of E. multilocularis, we investigated the phenotype and function of hepatic macrophages during the parasite infection. In the present study, we found that a large number of CD68⁺ macrophages accumulated around the metacestode lesion in the liver of human AE samples and that both S100A9⁺ proinflammatory (M1 phenotype) and CD163⁺ anti-inflammatory (M2 phenotype) macrophages were significantly higher in close liver tissue (CLT) than in distant liver tissue (DLT), whereas M2 macrophages represent the dominant macrophage population. Furthermore, E. multilocularis-infected mice exhibited a massive increase in macrophage (F4/80⁺) infiltration in the liver as early as day 5, and the infiltrated macrophages were mainly monocyte-derived macrophages (CD11b^hi F4/80^int MoMFs) that preferentially differentiated into the M1 phenotype (iNOS⁺) at the early stage of E. multilocularis infection and then polarized to anti-inflammatory macrophages of the M2 phenotype (CD206⁺) at the chronic stage of infection. We further showed that elimination of macrophages by treatment of mice with clodronate-liposomes before E. multilocularis infection impaired worm expulsion and was accompanied by a reduction in liver fibrosis, yielding a high parasite burden. These results suggest that hepatic macrophages may play a dual role in the establishment and development of E. multilocularis metacestodes in which early larvae clearance is promoted by M1 macrophages while persistent metacestode infection is favored by M2 macrophages.

Regulation of hepatic microRNAs in response to early stage Echinococcus multilocularis egg infection in C57BL/6 mice

We present a comprehensive analysis of the hepatic miRNA transcriptome at one month post-infection of experimental primary alveolar echinococcosis (AE), a parasitic infection caused upon ingestion of E. multilocularis eggs. Liver tissues were collected from infected and non-infected C57BL/6 mice, then small RNA libraries were prepared for next-generation sequencing (NGS). We conducted a Stem-loop RT-qPCR for validation of most dysregulated miRNAs. In infected mice, the expression levels of 28 miRNAs were significantly altered. Of these, 9 were up-regulated (fold change (FC) ≥ 1.5) and 19 were down-regulated (FC ≤ 0.66) as compared to the non-infected controls. In infected livers, mmu-miR-148a-3p and mmu-miR-101b-3p were 8- and 6-fold down-regulated, respectively, and the expression of mmu-miR-22-3p was reduced by 50%, compared to non-infected liver tissue. Conversely, significantly higher hepatic levels were noted for Mus musculus (mmu)-miR-21a-5p (FC = 2.3) and mmu-miR-122-5p (FC = 1.8). In addition, the relative mRNA expression levels of five genes (vegfa, mtor, hif1-α, fasn and acsl1) that were identified as targets of down-regulated miRNAs were significantly enhanced. All the five genes exhibited a higher expression level in livers of E. multilocularis infected mice compared to non-infected mice. Finally, we studied the issue related to functionally mature arm selection preference (5p and/or 3p) from the miRNA precursor and showed that 9 pre-miRNAs exhibited different arm selection preferences in normal versus infected liver tissues. In conclusion, this study provides first evidence that miRNAs are regulated early in primary murine AE. Our findings raise intriguing questions such as (i) how E. multilocularis affects hepatic miRNA expression;(ii) what are the alterations in miRNA expression patterns in more advanced AE-stages; and (iii) which hepatic cellular, metabolic and/or immunologic processes are modulated through altered miRNAs in AE. Thus, further research on the regulation of miRNAs during AE is needed, since miRNAs constitute an attractive potential option for development of novel therapeutic approaches against AE.

Various infectious diseases in humans have been associated with altered expression patterns of microRNAs (miRNAs), a class of small non-coding RNAs involved in negative regulation of gene expression. Herein, we revealed that significant alteration of miRNAs expression occurred in murine liver subsequently to experimental infection with E. multilocularis eggs when compared to non-infected controls. At the early stage of murine AE, hepatic miRNAs were mainly down-regulated. Respective target genes of the most extensively down-regulated miRNAs were involved in angiogenesis and fatty acid synthesis. Furthermore, we found higher mRNA levels of three angiogenic and two lipogenic genes in E. multilocularis infected livers compared to non-infected controls. Angiogenesis and fatty acid biosynthesis may be beneficial for development of the E. multilocularis metacestodes. In fact the formation of new blood vessels in the periparasitic area may ensure that parasites are supplied with oxygen and nutrients and get rid of waste products. Additionally, E. multilocularis is not able to undertake de novo fatty acid synthesis, thus lipids must be scavenged from its host. More research on the regulation of the hepatic miRNA transcriptome at more advanced stages of AE is needed.

miRNAs and lncRNAs in Echinococcus and Echinococcosis

Echinococcosis are considered to be potentially lethal zoonotic diseases that cause serious damage to hosts. The metacestode of Echinococcus multilocularis and E. granulosus can result in causing the alveolar and cystic echinococcoses, respectively. Recent studies have shown that non-coding RNAs are widely expressed in Echinococcus spp. and hosts. In this review, the two main types of non-coding RNAs—long non-coding RNAs (lncRNAs) and microRNAs (miRNAs)—and the wide-scale involvement of these molecules in these parasites and their hosts were discussed. The expression pattern of miRNAs in Echinococcus spp. is species- and developmental stage-specific. Furthermore, common miRNAs were detected in three Echinococcus spp. and their intermediate hosts. Here, we primarily focus on recent insights from transcriptome studies, the expression patterns of miRNAs and lncRNAs, and miRNA-related databases and techniques that are used to investigate miRNAs in Echinococcus and echinococcosis. This review provides new avenues for screening therapeutic and diagnostic markers.

Echinococcosis: Advances in the 21st Century

Echinococcosis is a zoonosis caused by cestodes of the genus Echinococcus (family Taeniidae). This serious and near-cosmopolitan disease continues to be a significant public health issue, with western China being the area of highest endemicity for both the cystic (CE) and alveolar (AE) forms of echinococcosis. Considerable advances have been made in the 21st century on the genetics, genomics, and molecular epidemiology of the causative parasites, on diagnostic tools, and on treatment techniques and control strategies, including the development and deployment of vaccines. In terms of surgery, new procedures have superseded traditional techniques, and total cystectomy in CE, ex vivo resection with autotransplantation in AE, and percutaneous and perendoscopic procedures in both diseases have improved treatment efficacy and the quality of life of patients. In this review, we summarize recent progress on the biology, epidemiology, diagnosis, management, control, and prevention of CE and AE. Currently there is no alternative drug to albendazole to treat echinococcosis, and new compounds are required urgently. Recently acquired genomic and proteomic information can provide a platform for improving diagnosis and for finding new drug and vaccine targets, with direct impact in the future on the control of echinococcosis, which continues to be a global challenge.

Subcutaneous Inoculation of Echinococcus multilocularis Induces Delayed Regeneration after Partial Hepatectomy

Alveolar echinococcosis (AE) is caused by the larval stage of echinococcus multilocularis (E. multilocularis), and hepatectomy is the main modality in hepatic AE patients. Liver regeneration after partial hepatectomy (PHx) in such patients is challenging, and further investigation is needed. Thus far, knowledge regarding the possible impact of E. multilocularis on liver regeneration after PHx is limited. Herein, a subcutaneous infection model of E. multilocularis was developed in C57 BL/6 mice, and after 3 months, PHx was performed. Plasma and liver samples were harvested under inhalational isofluorane (2%) anaesthesia at designated post-PHx time points (0, 24, 48, 96 and 168 h). The parameters included the future remnant liver/body weight ratio (FLR/BW), liver function tests (AST and ALT) and related cytokines (TNF-α, IL-6, Factor V, HMGB1, TGF-β, TSP-1, and TLR4) and proteins (MyD88 and STAT3). To assess the proliferation intensity of hepatocytes, BrdU, Ki67 and PAS staining were carried out in regenerated liver tissue. The FLR/BW in the infected group from 48 h after surgery was lower than that in the control group. The BrdU positive hepatocyte proportions reached their peak at 48 h in the control group and 96 h in the infected group and then gradually decreased. During the first 48 h after surgery, both the AST and ALT levels in the infected group were lower; however, these levels were altered from 96 h after surgery. In the infected group, the concentrations and mRNA expression levels of the pre-inflammatory cytokines TNF-α and IL-6 demonstrated a delayed peak. Moreover, post-operatively, the TGF-β and TSP-1 levels showed high levels in the infected group at each different time-point compared to those in the control group; however, high levels of TGF-β were observed at 96 h in the control group. The MyD88 and STAT3 protein expression levels in the infected group were markedly higher than those in the control group 96 h after surgery. Delayed liver regeneration after PHx was observed in the C57 BL/6 mice with the subcutaneous infection of E. multilocularis in the current study. This phenomenon could be partially explained by the alteration in the pro-inflammatory cytokines in the immunotolerant milieu induced by chronic E. multilocularis infection.

Immunotherapy of alveolar echinococcosis via PD-1/PD-L1 immune checkpoint blockade in mice

The growth potential of the tumour‐like Echinococcus multilocularis metacestode (causing alveolar echinococcosis, AE) is directly dependent upon the nature/function of the periparasitic adaptive host immune‐mediated processes. PD‐1/PD‐L1 pathway (programmed cell death 1), which inhibits lymphocytic proliferation in tumour development, is over‐expressed at the chronic stage of AE. We tested the impact of a PD‐1/PD‐L1 pathway blockade on the outcome of both chronic AE (intraperitoneal metacestode inoculation, secondary AE and SAE) and acute AE (peroral egg infection, primary AE and PAE). To assess the parasite proliferation potential, we measured parasite mass weight for SAE and liver lesion number for PAE. In both models, the parasite load was significantly decreased in response to anti‐PD‐L1 antibody treatment. In SAE, anti‐PDL1 administration was associated with increased Th1 response parameters and decreased Treg responses, while in PAE anti‐PDL1 administration was associated with fewer lesions in the liver and decreased Treg/Th2 responses. Our findings highly suggested that a PD‐1/PD‐L1 pathway blockade triggered the host immune responses in favour of an immune‐mediated control of E. multilocularis proliferation. Based on this, future studies that combine PD‐1/PD‐L1 blockade with a parasitostatic albendazole medication may yield in a putatively curative therapeutic approach to control alveolar echinococcosis.

Foxp3+ T Regulatory Cells as a Potential Target for Immunotherapy against Primary Infection with Echinococcus multilocularis Eggs

Alveolar echinococcosis (AE) is a lethal disease caused by infection with the metacestode stage of the helminth Echinococcus multilocularis, which develops into a tumorlike mass in susceptible intermediate hosts. The growth potential of this parasite stage is directly linked to the nature of the surrounding periparasitic immune-mediated processes. In a first step (experiment 1), mice were orally infected with E. multilocularis eggs, to be used for assessing the hepatic expression profiles of 15 selected cytokine and chemokine genes related to acquired immunity from 21 to 120 days postinfection. The early stage of infection in immunocompetent animals was marked by a mixed Th1/Th2 immune response, as characterized by the concomitant presence of gamma interferon (IFN-γ) and interleukin-4 (IL-4) and their related chemokines. At the late stage of AE, the profile extended to a combined tolerogenic mode including Foxp3, IL-10, and transforming growth factor beta (TGF-β) as key components. In a second step (experiment 2), the effect of T regulatory cell (Treg) deficiency on metacestode growth was assessed in E. multilocularis-infected DEREG (depletion of regulatory T cells) mice upon induction of Treg deficiency with diphtheria toxin (DT). The parasite lesions were significantly smaller in the livers of treated mice than in corresponding control groups. Foxp3⁺ Tregs appear to be one of the key players in immune-regulatory processes favoring metacestode survival by affecting antigen presentation and suppressing Th1-type immune responses. For these reasons, we suggest that affecting Foxp3⁺ Tregs could offer an attractive target in the development of an immunotherapy against AE.

Plasma IL-23 and IL-5 as surrogate markers of lesion metabolic activity in patients with hepatic alveolar echinococcosis

Fluorodeoxyglucose (FDG) uptake by alveolar echinococcosis (AE) liver lesions is a signal of their metabolic activity and of disease progression. In order to find a surrogate marker for this status, we investigated whether parameters of the peripheral and/or periparasitic immune responses were associated with metabolic activity in a prospective case-control study of 30 AE patients and 22 healthy controls. Levels of 18 cytokines and chemokines, representative of innate and adaptive immune responses, were assessed in plasma and peripheral cells of two groups of patients with (MAAE) and without (MIAE) metabolically active lesions, and in the liver of MAAE patients. Mixed cytokine profile was observed in the peripheral blood of AE patients, with a predominance of Th2, Th17 and Treg responses. Among the detected markers only plasma IL-5 and IL-23, more elevated in MAAE patients, were found discriminant. Discrimination between MAAE and MIAE patients obtained by using IL-23 was improved when IL-5 was used in combination. The combination of elevated levels of IL-5 and IL-23 is significantly associated with FDG uptake at PET scan. It offers a new tool for the follow-up of AE patients which could substitute to FDG-PET whenever non-available to assess disease progression.

Larval Echinococcus multilocularis infection reduces dextran sulphate sodium-induced colitis in mice by attenuating T helper type 1/type 17-mediated immune reactions

The tumour‐like growth of larval Echinococcus multilocularis tissue (causing alveolar echinococcosis, AE) is directly linked to the nature/orientation of the periparasitic host immune‐mediated processes. Parasite‐mediated immune suppression is a hallmark triggering infection outcome in both chronic human and murine AE. So far, little is known about secondary systemic immune effects of this pathogen on other concomitant diseases, e.g. endogenous gut inflammation. We examined the influence of E. multilocularis infection on murine dextran sodium sulphate (DSS) ‐induced colitis. At 3 months after E. multilocularis infection (chronic stage), the mice were challenged with 3% DSS in the drinking water for 5 days plus subsequently with tap water (alone) for another 4 days. After necropsy, fixed tissues/organs were sectioned and stained with haematoxylin & eosin for assessing inflammatory reactions. Cytokine levels were measured by flow cytometry and quantitative RT‐PCR. Colitis severity was assessed (by board‐certified veterinary pathologists) regarding (i) colon length, (ii) weight loss and (iii) a semi‐quantitative score of morphological changes. The histopathological analysis of the colon showed a significant reduction of DSS‐induced gut inflammation by concomitant E. multilocularis infection, which correlated with down‐regulation of T helper type 1 (Th1)/Th17 T‐cell responses in the colon tissue. Echinococcus multilocularis infection markedly reduced the severity of DSS‐induced gut inflammation upon down‐regulation of Th1/Th17 cytokine expression and attenuation of CD11b⁺ cell activation. In conclusion, E. multilocularis infection remarkably reduces DSS‐induced colitis in mice by attenuating Th1/Th17‐mediated immune reactions.

MicroRNA expression profile in RAW264·7 macrophage cells exposed to Echinococcus multilocularis metacestodes

MicroRNAs (miRNAs) are short noncoding RNAs, involved in the regulation of parasite diseases. However, a role of miRNAs in Echinococcus multilocularis infection remains largely unknown. In this study, we first found the expression levels of key genes involved in miRNA biogenesis and function, including Ago2, Xpo5, Tarbp2 and DgcR8, were obviously altered in the macrophage RAW264·7 cells exposed to E. multilocularis metacestodes. Compared with the control, 18 and 32 known miRNAs were found to be differentially expressed (P 2) in the macrophages exposed to E. multilocularis metacestodes for 6 and 12 h, respectively. Among these, several are known to be involved in regulating cytokine activities and immune responses. Quantitative real-time polymerase chain reaction results showed that the expression of nine selected miRNAs was consistent with the sequencing data at each treatment time points. Moreover, there were statistically significant correlations between the expression levels of miRNAs and their corresponding targeted genes. Our data give us some clues to pinpoint a role of miRNAs in the course of infection and immunity of E. multilocularis.

Expression of toll-like receptor 2, 4 and related cytokines in intraperitoneally inoculated Balb/C mice with Echinococcus multilocularis

Immune response pattern between host and Echinococcus multilocularis (E. multilocularis) is considered as a crucial point in development of alveolar echinococcosis (AE). In this study, we are aiming to study the expression patterns of TLR2 and TLR4 with related cytokines and transcription factors in secondary E. multilocularis infected murine model. The murine model of AE was developed by using intraperitoneal inoculation of E. multilocularis protoscolexes and albendazole (E. m+ABZ group) or carboxy methyle cellulose (CMC; E. m+CMC group) administration via gastric tube was initiated in the third month and continued for one month. Mice with CMC administration served as negative controls (C+CMC group). The splenic cells and peritoneal exudates cells (PECs) were prepared and the levels of IFN-γ, IL-10, and IL-5 in splenic cells and PECs culture supernatants were detected using enzyme linked immune-sorbent assay (ELISA). Besides, the mRNA expression levels of TLR2, 4, transcription factors and cytokines were detected by using real-time fluorescent quantitative reverse-transcription polymerase chain reaction (qRT-PCR). The concentration levels of IFN-γ, IL-10, and IL-5 in PECs and splenic cell supernatants were extremely lower, however, significantly elevated after stimulated with Concanavalin A (ConA) for 36 h with higher concentrations in E. m+CMC group comparing to both E. m+ABZ and C+CMC group. The mRNA levels of TLR2, 4 and GATA3, IFN-γ, IL-10 in splenic cells were significantly increased in E. m+CMC group comparing with other groups. Simultaneously, T-bet mRNA expressions were elevated in E. m+ABZ and C+CMC group compared to E. m+CMC group. In addition, T-bet/GATA3 ratios was higher in E. m+ABZ group compared to E. m+CMC group and were higher in C+CMC group than those in E. m+CMC group. TLR2 mRNA expression in splenic cells showed a positive correlation with IL-10 concentration levels in splenic cell culture supernatants. The present study provides evidence on the possible role of TLR2 in the process of immune tolerance during E. multilocularis infection and suggests albendazole treatment might reverse the immune tolerance situation and improve parasite clearance process.

Depletion of FoxP3+ Tregs improves control of larval Echinococcus multilocularis infection by promoting co-stimulation and Th1/17 immunity

Introduction

The growth potential of the tumor‐like Echinococcus multilocularis metacestode (causing alveolar echinococcosis, AE) is directly linked to the nature/function of the periparasitic host immune‐mediated processes. Previous studies had shown that regulatory T cells (Tregs) become gradually up‐regulated in the course of both chronic human and murine AE. Thus we now tackled the role of FoxP3⁺ Tregs and FoxP3⁺‐Treg‐regulated immune response in contributing to the control of this helminthic infection.

Methods

The infection outcome in E. multilocularis‐infected DEREG mice was measured upon determining parasite load (wet weight of parasitic metacestode tissue). Flow cytometry and qRT‐PCR were used to assess Treg, Th17‐, Th1‐, Th2‐type immune responses and antigen presenting cell activation.

Results

We showed that E. multilocularis‐infected DEREG‐mice treated with DT (as compared to infected control DEREG‐mice without DT application) exhibited a significantly lower parasite load, associated with a persisting capacity of co‐stimulation, and an increased Th1/Th17‐polarization.

Conclusions

FoxP3⁺ Tregs appear as one of the key players in immune regulatory processes favoring (i) metacestode survival by inhibiting the maturation potential of co‐stimulatory activity and (ii) T cell exhaustion (suppressing Th1/Th17‐type immune responses). We showed as well that prospectively, targeting FoxP3⁺ Tregs could be an option to develop an immunotherapy against AE.

Albendazole increases the inflammatory response and the amount of Em2-positive small particles of Echinococcus multilocularis (spems) in human hepatic alveolar echinococcosis lesions

Background

Alveolar echinococcosis (AE) is caused by the metacestode stage of Echinococcus multilocularis. The inflammatory response to this infection is influenced by the interaction of the parasite with the host. We aimed to analyze human liver lesions infected with Echinococcus multilocularis and the changes of the cellular infiltrates during albendazole (ABZ) treatment.

Methodology/Principal findings

We analyzed liver tissue samples from 8 untreated patients, 5 patients treated with two daily doses of 400 mg ABZ for up to two months and 7 patients treated for more than two months with the same ABZ therapy. A broad panel of monoclonal antibodies was used to characterize the lesion by immunohistochemistry. A change in the cellular infiltrate was observed between the different chemotherapy times. During the initial phases of treatment an increase in CD15⁺ granulocytes and CD68⁺ histocytes as well as in small particles of Echinococcus multilocularis (spems) was observed in the tissue surrounding the metacestode. Furthermore, we observed an increase in CD4⁺ T cells, CD20⁺ B cells and CD38⁺ plasma cells during a longer duration of treatment.

Conclusions/Significance

ABZ treatment of AE leads to morphological changes characterized by an initial, predominantly acute, inflammatory response which is gradually replaced by a response of the adaptive immune system.

Alveolar echinococcosis (AE) is a life-threatening disease in humans caused by the larval stages of E. multilocularis. It has been shown that the infection in humans is associated with a modulated immune response. Depending on multiple factors, such as the stage of disease, total or partial surgical resection and albendazole (ABZ) therapy are treatments of choice. ABZ is known as a parasitostatic drug that has to be administered for years to suppress metacestode development. Here we compared human liver lesions before and after short and long term treatment with ABZ by immunohistochemistry using a broad panel of antibodies. We found a change in the cellular infiltrate, characterized by a shift to an infiltrate rich in T cells, B cells and plasma cells during long-term treatment with ABZ, including a pronounced detection of small particles of E. multilocularis (spems). We argue that ABZ treatment is likely to change the cellular infiltrate, leading to an enhancement of the host immune response during treatment.

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.

Immunoregulation in larval Echinococcus multilocularis infection

Alveolar echinococcosis (AE) is a clinically very severe zoonotic helminthic disease, characterized by a chronic progressive hepatic damage caused by the continuous proliferation of the larval stage (metacestode) of Echinococcus multilocularis. The proliferative potential of the parasite metacestode tissue is dependent on the nature/function of the periparasitic immune-mediated processes of the host. Immune tolerance and/or down-regulation of immunity are a marked characteristic increasingly observed when disease develops towards its chronic (late) stage of infection. In this context, explorative studies have clearly shown that T regulatory (Treg) cells play an important role in modulating and orchestrating inflammatory/immune reactions in AE, yielding a largely Th2-biased response, and finally allowing thus long-term parasite survival, proliferation and maturation. AE is fatal if not treated appropriately, but the current benzimidazole chemotherapy is far from optimal, and novel options for control are needed. Future research should focus on the elucidation of the crucial immunological events that lead to anergy in AE, and focus on providing a scientific basis for the development of novel and more effective immunotherapeutical options to support cure AE by abrogating anergy, anticipating also that a combination of immuno- and chemotherapy could provide a synergistic therapeutical effect.

Immunology of Alveolar and Cystic Echinococcosis (AE and CE)

Cystic and alveolar echinococcosis are severe chronic helminthic diseases caused by the cystic growth or the intrahepatic tumour-like growth of the metacestode of Echinococcus granulosus or Echinococcus multilocularis, respectively. Both parasites have evolved sophisticated strategies to escape host immune responses, mainly by manipulating and directing this immune response towards anergy and/or tolerance. Recent research studies have revealed a number of respective immunoregulatory mechanisms related to macrophages and dendritic cell as well as T cell activities (regulatory T cells, Tregs). A better understanding of this complex parasite-host relationship, and the elucidation of specific crucial events that lead to disease, represents targets towards the development of novel treatment strategies and options.

Parasitic infection as a potential therapeutic tool against rheumatoid arthritis

Parasites, which are a recently discovered yet ancient dweller in human hosts, remain a great public health burden in underdeveloped countries, despite preventative efforts. Rheumatoid arthritis is a predominantly cosmopolitan health problem with drastic morbidity rates, although encouraging progress has been achieved regarding treatment. However, although various types of methods and agents have been applied clinically, their broad usage has been limited by their adverse effects and/or high costs. Sustained efforts have been exerted on the 'hygiene hypothesis' since the 1870s. The immunosuppressive nature of parasitic infections may offer potential insight into therapeutic strategies for rheumatoid arthritis, in which the immune system is overactivated. An increasing number of published papers are focusing on the preventive and/or curative effect of various parasitic infection on rheumatoid arthritis from experimental studies to large-scale epidemiological studies and clinical trials. Therefore, the present review aimed to provide a general literature review on the possible beneficial role of parasitic infection on rheumatoid arthritis.

Gene Expression Profile in the Liver of Sheep Infected with Cystic Echinococcosis

Background

Cystic Echinococcosis (CE), caused by infection with the Echinococcus granulosus (E. granulosus), represents considerable health problems in both humans and livestock. Nevertheless, the genetic program that regulates the host response to E. granulosus infection is largely unknown. Previously, using microarray analysis, we found that the innate immunity played a vital role in the E. granulosus defense of the intestine tissue where E. granulosus first invaded. Subsequently, we turned our attention to investigating the molecular immune mechanism in its organ target, the liver, which is where the E. granulosus metacestodes are established and live for very long periods. In this work, the microarray-based methodology was used to study gene expression profiles in the liver of sheep infected with E. granulosus at 8 weeks post infection, corresponding to the early cystic established phase.

Methods

A total of 6 female-1-year-old healthy Kazakh sheep were used for the experiments. Three Kazakh sheep were orally infected with E. granulosus eggs, and the others remained untreated and served as controls. Sheep were humanely euthanized and necropsized at 8 weeks post-infection (the early stage of cyst established). The microarray was used to detect differential hepatic gene expression between CE infection sheep and healthy controls at this time point. Real-time PCR was used to validate the microarray data.

Results

We found that E. granulosus infection induces 153 differentially expressed genes in the livers of infected sheep compared with healthy controls. Among them, 87 genes were up-regulated, and 66 genes were notably down-regulated. Functional analysis showed that these genes were associated with three major functional categories: (a) metabolism, (b) the immune system and (c) signaling and transport. Deeper analysis indicated that complement together with other genes associated with metabolism, played important roles in the defense of E. granulosus infection.

Conclusion

The present study identified genes profiling in the liver tissue of E. granulosus infection in sheep. The expression pattern obtained here could be helpful for understanding the molecular immunity mechanisms of host responses to E. granulosus infection. However, it is necessary to carry out further studies to evalute the role of these genes.

Hydatid cyst fluid promotes peri-cystic fibrosis in cystic echinococcosis by suppressing miR-19 expression

Background

Echinococcus granulosus infection causes cystic echinococcosis (CE); the generation of liver fibrosis around the parasitic larval cyst (metacestode) may play a major role in the spontaneous limitation of the parasitic growth; however, fibrogenesis has received little attention in CE. It has been reported that miR-19b plays a role in various diseases, including infectious diseases, by regulating fibrogenesis. However, its function in the development of liver fibrosis in E. granulosus infection is unknown.

Methods

The expression of miR-19b and genes that are involved in liver fibrosis were analysed in E. granulosus-infected human livers using qRT-PCR. The role of miR-19b on hepatic stellate cells (LX-2 cells in vitro) treated with hydatid cyst fluid (HCF) was then analysed by 3-(4, 5-dimet-hylthiazol-2-yl)-2, 4-diphenyl-tetrazolium bromide (MTT) assay, qRT-PCR, Western blot and flow cytometry.

Results

The results showed that the expression of miR-19 was significantly reduced in the pericystic collagen-rich liver tissue of CE patients, compared to normal liver. Incubation of LX-2 cells (in vitro) with HCF induced a decreased proliferation of these cells and a reduced expression of miR-19, inversely correlated with the expression of collagen 1A1 and TGF-β receptor II (TβRII). Conversely, overexpression of miR-19 by LX-2 cells inhibited the proliferation of these cells and led to decreased TβRII expression.

Conclusions

Our study provides new evidence for the intervention of miRNAs in the regulation of fibrosis in infectious diseases; it suggests that E. granulosus can inhibit miR-19 liver expression and promote fibrosis through the increase in TβRII, the activation of hepatic stellate cells and extracellular matrix production.

The Potential Role of Th9 Cell Related Cytokine and Transcription Factors in Patients with Hepatic Alveolar Echinococcosis

Human alveolar echinococcosis (AE) is a lethal parasitic infectious disease which may lead to liver failure if left untreated. It is caused by the larval stage of the fox tapeworm Echinococcus multilocularis and usually develops a substantial infiltrative occupation in solid organs. During the infection, T helper subsets are known to play crucial role in crosstalk between the parasite and human host. Th9 cells, a new member of CD4⁺ T cell family which is characterized by its specific cytokine IL-9 and transcription factors PU.1 and IRF-4, have been known recently to have a critical role in allergic diseases, and cancers as well as the parasitic infection. To assess the potential role of Th9 cells during the infection, the mRNA levels of IL-9, PU.1, and IRF-4 both in peripheral blood mononuclear cells and in liver tissues were, respectively, detected by using real-time PCR. The plasma concentration levels of IL-9 were detected by using enzyme linked immunosorbent assay (ELISA). Th9 related cytokine IL-9 and transcription factors PU.1 and IRF-4 mRNA levels elevated both in PBMCs, and in hepatic lesion and paralesion tissues in AE patients. This may facilitate the infiltrative growth of the parasite and its persistence in human host.

An Immediate Innate Immune Response Occurred In the Early Stage of E. granulosus Eggs Infection in Sheep: Evidence from Microarray Analysis

BACKGROUND

Cystic Echinococcosis(CE), caused by infection with the larval stage of the cestode Echinococcus granulosus (E. granulosus), is a chronic parasitic zoonosis, with highly susceptible infection in sheep. However, the comprehensive molecular mechanisms that underlie the process of E. granulosus infection in the early stage remain largely unknown. The objective of this present study was to gain a cluster of genes expression profiles in the intestine tissue of sheep infected with CE.

METHODS

Nine healthy sheep were divided into infection group and healthy controls, with six infected perorally 5000 E. granulosus eggs suspended in 1000 μl physiological saline and three controls perorally injected 1000 μl physiological saline. All animals were sacrificed at 4 hours post-infection, respectively. The intestine tissue was removed and the RNA was extracted. In the infection group, the biology replicates were designed to make sure the accuracy of the data. The ovine microarrays were used to analyze changes of gene expression in the intestine tissue between CE infected sheep and healthy controls. Real-time PCR was used to assess reliability of the microarray data.

RESULTS

By biology repeats, a total of 195 differentially expressed genes were identified between infected group and controls at 4 hours post-infection, with 105 genes related to immune responses, while 90 genes associated with functions including energy metabolism, fat soluble transport, etc. Among the 105 immunity genes, 72 genes showed up-regulated expression levels while 33 showed down-regulation levels. Function analysis showed that most of up-regulated genes were related to innate immune responses, such as mast cell, NK cell, cytokines, chemokines and complement. In addition, Real-time PCR analysis of a random selection of nine genes confirmed the reliability of the microarray data.

CONCLUSION

To our knowledge, this is the first report describing gene expression profiles in the intestine tissue of CE infection sheep. These results suggested that the innate immune system was activated to elicit immediate defense in the intestine tissue where E. granulosus invaded in at 4 hour-post infection. Furthermore, future interest will also focus on unraveling similar events, especially for the function of adaptive immunity, but at late stage infection.

Susceptibility versus resistance in alveolar echinococcosis (larval infection with Echinococcus multilocularis)

Epidemiological studies have demonstrated that the majority of human individuals exposed to infection with Echinococcus spp. eggs exhibit resistance to disease as shown by either seroconversion to parasite--specific antigens, and/or the presence of 'dying out' or 'aborted' metacestodes, not including hereby those individuals who putatively got infected but did not seroconvert and who subsequently allowed no development of the pathogen. For those individuals where infection leads to disease, the developing parasite is partially controlled by host immunity. In infected humans, the type of immune response developed by the host accounts for the subsequent trichotomy concerning the parasite development: (i) seroconversion proving infection, but lack of any hepatic lesion indicating the failure of the parasite to establish and further develop within the liver; or resistance as shown by the presence of fully calcified lesions; (ii) controlled susceptibility as found in the "conventional" alveolar echinococcosis (AE) patients who experience clinical signs and symptoms approximately 5-15 years after infection, and (iii) uncontrolled hyperproliferation of the metacestode due to an impaired immune response (AIDS or other immunodeficiencies). Immunomodulation of host immunity toward anergy seems to be triggered by parasite metabolites. Beside immunomodulating IL-10, TGFβ-driven regulatory T cells have been shown to play a crucial role in the parasite-modulated progressive course of AE. A novel CD4+CD25+ Treg effector molecule FGL2 recently yielded new insight into the tolerance process in Echinococcus multilocularis infection.

Prevention and Immunotherapy of Secondary Murine Alveolar Echinococcosis Employing Recombinant EmP29 Antigen

Alveolar echinococcosis (AE) is caused by infection with the larval stage of the tapeworm Echinococcus multilocularis. An increasing understanding of immunological events that account for the metacestode survival in human and murine AE infection prompted us to undertake explorative experiments tackling the potential of novel preventive and/or immunotherapeutic measures. In this study, the immunoprotective and immunotherapeutic ability of recombinant EmP29 antigen (rEmP29) was assessed in mice that were intraperitoneally infected with E. multilocularis metacestodes. For vaccination, three intraperitoneal injections with 20μg rEmP29 emulsified in saponin adjuvants were applied over 6 weeks. 2 weeks after the last boost, mice were infected, and at 90 days post-infection, rEmP29-vaccinated mice exhibited a median parasite weight that was reduced by 75% and 59% when compared to NaCl- or saponin–treated control mice, respectively. For immunotherapeutical application, the rEmP29 (20μg) vaccine was administered to experimentally infected mice, starting at 1 month post-infection, three times with 2 weeks intervals. Mice undergoing rEmP29 immunotherapy exhibited a median parasite load that was reduced by 53% and 49% when compared to NaCl- and saponin–treated control mice, respectively. Upon analysis of spleen cells, both, vaccination and treatment with rEmP29, resulted in low ratios of Th2/Th1 (IL-4/IFN-γ) cytokine mRNA and low levels of mRNA coding for IL-10 and IL-2. These results suggest that reduction of the immunosuppressive environment takes place in vaccinated as well as immunotreated mice, and a shift towards a Th1 type of immune response may be responsible for the observed increased restriction of parasite growth. The present study provides the first evidence that active immunotherapy may present a sustainable route for the control of AE.

Current medical management of AE that relies on surgery and continuous benzimidazole administration is of limited effectiveness. Therefore, alternative preventive and therapeutic tools need to be explored. Here, we demonstrate that vaccination with recombinant antigen EmP29 (rEmP29), prior or after secondary infection of BALB/c mice, resulted in a significant reduction of the median parasite weight when compared to different control groups. We then characterized the transcription level of splenic IL-4 and IFN-γ cytokines as hallmarks for AE-anti-protective humoral immune reaction (Th2) and for AE-effective (restrictive) cellular response (Th1), respectively. Results revealed that vaccinated mice in pre- or post-infection situation exhibited the lowest IL-4/IFN-γ mRNA ratios. In addition, those groups showed also significantly low levels of IL-10-encoding mRNA coding (immunosuppressive cytokine), as well as IL-2. These findings suggest that reduction of parasite load in rEmP29-vaccinated mice (in pre- or post-infection status) might be triggered by a decline of the immunosuppressive environment and a change of the host immune reaction towards a Th1-re-oriented cell-mediated immune defense. A similar non-specific effect appears also to be yielded by the immunostimulating adjuvants. This study provides the first insight into the potential benefits of antigen-specific immunotherapy as new treatment option of AE.

Deletion of Fibrinogen-like Protein 2 (FGL-2), a Novel CD4+ CD25+ Treg Effector Molecule, Leads to Improved Control of Echinococcus multilocularis Infection in Mice

Background

The growth potential of the tumor-like Echinococcus multilocularis metacestode (causing alveolar echinococcosis, AE) is directly linked to the nature/function of the periparasitic host immune-mediated processes. We previously showed that Fibrinogen-like-protein 2 (FGL2), a novel CD4⁺CD25⁺ Treg effector molecule, was over-expressed in the liver of mice experimentally infected with E. multilocularis. However, little is known about its contribution to the control of this chronic helminth infection.

Methods/Findings

Key parameters for infection outcome in E. multilocularis-infected fgl2^-/- (AE-fgl2^-/-) and wild type (AE-WT) mice at 1 and 4 month(s) post-infection were (i) parasite load (i. e. wet weight of parasitic metacestode tissue), and (ii) parasite cell proliferation as assessed by determining E. multilocularis 14-3-3 gene expression levels. Serum FGL2 levels were measured by ELISA. Spleen cells cultured with ConA for 48h or with E. multilocularis Vesicle Fluid (VF) for 96h were analyzed ex-vivo and in-vitro. In addition, spleen cells from non-infected WT mice were cultured with rFGL2/anti-FGL2 or rIL-17A/anti-IL-17A for further functional studies. For Treg-immune-suppression-assays, purified CD4⁺CD25⁺ Treg suspensions were incubated with CD4⁺ effector T cells in the presence of ConA and irradiated spleen cells as APCs. Flow cytometry and qRT-PCR were used to assess Treg, Th17-, Th1-, Th2-type immune responses and maturation of dendritic cells. We showed that AE-fgl2^-/- mice exhibited (as compared to AE-WT-animals) (a) a significantly lower parasite load with reduced proliferation activity, (b) an increased T cell proliferative response to ConA, (c) reduced Treg numbers and function, and (d) a persistent capacity of Th1 polarization and DC maturation.

Conclusions

FGL2 appears as one of the key players in immune regulatory processes favoring metacestode survival by promoting Treg cell activity and IL-17A production that contributes to FGL2-regulation. Prospectively, targeting FGL2 could be an option to develop an immunotherapy against AE and other chronic parasitic diseases.

In larval E. multilocularis infection causing alveolar echinococcosis (AE) in humans as well as mice, immune tolerance and/or down-regulation of protective immunity is a marked characteristic of this chronic disease. Our study provides a comprehensive evidence for a major involvement of the recently identified CD4⁺ CD25⁺ Regulatory T Cell Effector Molecule FGL2 to the outcome of AE. Our major findings are as follows: 1) FGL2 is mostly secreted by Tregs and partly contributes to their functions; 2) FGL2 can down-regulate the maturation of DCs, suppress Th1 and Th17 immune responses, and support Th2 and Treg immune responses, and finally 3) IL-17A contributes to FGL2 secretion. Based on the present findings in mice, we will investigate FGL2 as a potential marker of progression of AE in human patients, or as a potential immunotherapeutical target. Early prediction of parasite regression (currently not yet possible) would allow clinicians to plan for withdrawing benzimidazole treatment, which is currently administered for life. Then, FGL2 should be investigated as a target for an anticipated immunomodulatory treatment of patients with progressive AE, especially of those who are non- or low-responders to benzimidazole treatment, or who suffer from side-effects due to chemotherapy.

Investigating the impact of Echinococcus multilocularis vesicular fluid on human cells from healthy blood donors

CONTEXT AND OBJECTIVES

Alveolar echinococcosis (AE) is a severe chronic helminthic disease that mimics slow-growing liver cancer. Previous studies using murine models suggest that Echinococcus multilocularis (Em) metacestodes have developed mechanisms which impair the natural inflammatory host response. The aim of this study was to investigate in vitro the impact of Em vesicular fluid (VF) on monocytes, monocytes derived dendritic cells and lymphocytes from healthy blood donors.

METHODS

First, assays were performed to investigate whether or not Em-VF influences monocyte-derived dendritic cell (MoDC) differentiation and maturation. Monocytes during differentiation and immature MoDCs were exposed to Em-VF. The effect of Em-VF was assessed using flow cytometry (CD86, CD83, CD80) and immune assays (IL-10 and TGFβ). Second, assays were performed to investigate the interaction between Em-VF, peripheral blood monocyte cells (PBMC) and Toll-like Receptor (TLR) agonists (LPS, PolyIC, R848 and CpG). PBMC were stimulated by each of the TLR agonists with and without Em-VF. The subsequent TGFβ production was assessed.

RESULTS

Exposure to Em-VF had bearing on both differentiation and maturation of MoDC, but only partially. A decrease in the expression of co-stimulatory molecules was observed; however, levels of immune-regulatory cytokines were stable. PBMC exposed simultaneously to Em-VF and LPS induced a significant increase of TGFβ (p<0.05, Wilcoxon signed-rank test). Further experiments showed that TGFβ production was lymphocyte-dependent.

CONCLUSION

The assays performed confirmed that Em-VF influences the host immune response. However, only minor changes were observed when investigating the Em-VF impact on cells from healthy blood donors. Assays with TLR agonists suggested that co-stimulation with LPS reinforces the response of healthy blood donors exposed to Em-VF.

Innovation in hepatic alveolar echinococcosis imaging: best use of old tools, and necessary evaluation of new ones

Hepatic Alveolar Echinococcosis (HAE), caused by larvae of Echinococcus multilocularis, is a rare but potentially lethal parasitic disease. The first diagnostic suspicion is usually based on hepatic ultrasound exam performed because of abdominal symptoms or in the context of a general checkup; HAE diagnosis may thus also be an incidental finding on imaging. The next step should be Computed Tomography (CT) or Magnetic Resonance Imaging (MRI). They play an important role in the initial assessment of the disease; with chest and brain imaging, they are necessary to assess the PNM stage (parasite lesion, neighboring organ invasion, metastases) of a patient with AE. Performed at least yearly, they also represent key exams for long-term follow-up after therapeutic interventions. Familiarity of radiologists with HAE imaging findings, especially in the endemic regions, will enable earlier diagnosis and more effective treatment. Fluorodeoxyglucose Positron Emission Tomography (FDG-PET) is currently considered to be the only noninvasive, albeit indirect, tool for the detection of metabolic activity in AE. Delayed acquisition of images (3 hrs after FDG injection) enhances its sensitivity for the assessment of lesion metabolism and its reliability for the continuation/withdrawal of anti-parasite treatment. However, sophisticated equipment and high cost widely limit PET/CT use for routine evaluation. Preliminary studies show that new techniques, such as contrast-enhanced ultrasound (US), Dual Energy CT or Spectral CT, and Diffusion-Weighted MRI, might also be useful in detecting the blood supply and metabolism of lesions. However, they cannot be recommended before further evaluation of their reliability in a larger number of patients with a variety of locations and stages of AE lesions.

Echinococcus metacestode: in search of viability markers

Epidemiological studies have demonstrated that most humans infected with Echinococcus spp. exhibit resistance to disease. When infection leads to disease, the parasite is partially controlled by host immunity: in case of immunocompetence, the normal alveolar echinococcosis (AE) or cystic echinococcosis (CE) situation, the metacestode grows slowly, and first clinical signs appear years after infection; in case of impaired immunity (AIDS; other immunodeficiencies), uncontrolled proliferation of the metacestode leads to rapidly progressing disease. Assessing Echinococcus multilocularis viability in vivo following therapeutic interventions in AE patients may be of tremendous benefit when compared with the invasive procedures used to perform biopsies. Current options are F18-fluorodeoxyglucose-positron emission tomography (FDG-PET), which visualizes periparasitic inflammation due to the metabolic activity of the metacestode, and measurement of antibodies against recEm18, a viability-associated protein, that rapidly regresses upon metacestode inactivation. For Echinococcus granulosus, similar prognosis-associated follow-up parameters are still lacking but a few candidates may be listed. Other possible markers include functional and diffusion-weighted Magnetic Resonance Imaging (MRI), and measurement of products from the parasite (circulating antigens or DNA), and from the host (inflammation markers, cytokines, or chemokines). Even though some of them have been promising in pilot studies, none has been properly validated in an appropriate number of patients until now to be recommended for further use in clinical settings. There is therefore still a need to develop reliable tools for improved viability assessment to provide the sufficient information needed to reliably withdraw anti-parasite benzimidazole chemotherapy, and a basis for the development of new alternative therapeutic tools.