Profile of cytokine production within the periparasitic granuloma in human alveolar 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.

The correlations between Th1 and Th2 cytokines in human alveolar echinococcosis

Background

Alveolar echinococcosis (AE) is a zoonotic parasitic disease caused by Echinococcus multilocularis larval tapeworm infections in humans that severely impairs the health of affected patients in the northern hemisphere.

Methods

The expression levels of 20 cytokines associated with AE infection were measured by enzyme-linked immunosorbent assay, and the correlations between these cytokines were analysed in the R programming language.

Results

Serum cytokine levels differed among individuals in both the AE patient and healthy control groups. The results of the correlations among the cytokines showed obvious differences between the two groups. In the AE patients group, Th1 and Th2 cytokines formed a more complicated network than that in the healthy control group.

Conclusions

The altered correlations between Th1 and Th2 cytokines may be closely associated with AE infection, which may provide a new explanation for the essential differences between AE patients and healthy individuals.

Expansion of Host Regulatory T Cells by Secreted Products of the Tapeworm Echinococcus multilocularis

Background

Alveolar echinococcosis (AE), caused by the metacestode larval stage of the fox-tapeworm Echinococcus multilocularis, is a chronic zoonosis associated with significant modulation of the host immune response. A role of regulatory T-cells (Treg) in generating an immunosuppressive environment around the metacestode during chronic disease has been reported, but the molecular mechanisms of Treg induction by E. multilocularis, particularly parasite immunoregulatory factors involved, remain elusive so far.

Methodology/Principal Findings

We herein demonstrate that excretory/secretory (E/S) products of the E. multilocularis metacestode promote the formation of Foxp3+ Treg from CD4+ T-cells in vitro in a TGF-β-dependent manner, given that this effect was abrogated by treatment with antibody to mammalian TGF-β. We also show that host T-cells secrete elevated levels of the immunosuppressive cytokine IL-10 in response to metacestode E/S products. Within the E/S fraction of the metacestode we identified an E. multilocularis activin A homolog (EmACT) that displays significant similarities to mammalian Transforming Growth Factor-β (TGF-β/activin subfamily members. EmACT obtained from heterologous expression failed to directly induce Treg expansion from naïve T cells but required addition of recombinant host TGF-β to promote CD4+ Foxp3+ Treg conversion in vitro. Furthermore, like in the case of metacestode E/S products, EmACT-treated CD4+ T-cells secreted higher levels of IL-10. These observations suggest a contribution of EmACT to in vitro expansion of Foxp3+ Treg by the E. multilocularis metacestode. Using infection experiments we show that intraperitoneally injected metacestode tissue expands host Foxp3+ Treg, confirming the expansion of this cell type in vivo during parasite establishment.

Conclusion/Significance

In conclusion, we herein demonstrate that E. multilocularis larvae secrete factors that induce the secretion of IL-10 by T-cells and contribute to the expansion of TGF-b-driven Foxp3+ Treg, a cell type that has been reported crucial for generating a tolerogenic environment to support parasite establishment and proliferation. Among the E/S factors of the parasite we identified a factor with structural and functional homologies to mammalian activin A which might play an important role in these activities.

Potential role of NF-κB pathway in the immuno-inflammatory responses during human cystic echinococcosis

Cystic echinococcosis (CE) induces in the human host innate and adaptive immune response that plays an important role in controlling the immunopathogenesis. Due to the crucial role of nuclear factor kappa B (NF-κB) in regulating immuno-inflammatory processes, we investigated its potential contribution in systemic and local immuno-inflammatory responses in primary CE patients and relapsed patients. The expression of NF-κB and inducible nitric oxide synthase (iNOS) was analyzed in peripheral blood mononuclear cells (PBMC) as well as in pericystic layer of pulmonary hydatid cysts from Algerian primary CE patients and relapsed patients. Tumor necrosis factor alpha (TNF-α) and nitric oxide (NO) production was evaluated in plasma samples. Our results showed high iNOS and NF-κB expression in both PBMCs and pericystic histiocytes from primary CE patients. In addition, substantial amounts of systemic NO and TNF-α were detected in the same patients. Remarkably, relapsed patients exhibited a low NF-κB and iNOS expression associated with low amounts of plasmatic TNF-α and NO. Collectively, NF-κB/iNOS pathway is involved in the host defense mechanisms at the systemic and local level during primary CE. Our results indicate that the inhibition of this pathway in relapsed patients will attenuate protective immunity and promote parasite escape. This study allowed to identify a novel predictive biomarkers of hydatidosis.

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.

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.

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.

Laboratory Diagnosis of Echinococcus spp. in Human Patients and Infected Animals

Among the species composing the genus Echinococcus, four species are of human clinical interest. The most prevalent species are Echinococcus granulosus and Echinococcus multilocularis, followed by Echinococcus vogeli and Echinococcus oligarthrus. The first two species cause cystic echinococcosis (CE) and alveolar echinococcosis (AE) respectively. Both diseases have a complex clinical management, in which laboratory diagnosis could be an adjunctive to the imaging techniques. To date, several approaches have been described for the laboratory diagnosis and followup of CE and AE, including antibody, antigen and cytokine detection. All of these approaches are far from being optimal as adjunctive diagnosis particularly for CE, since they do not reach enough sensitivity and/or specificity. A combination of several methods (e.g., antibody and antigen detection) or of several (recombinant) antigens could improve the performance of the adjunctive laboratory methods, although the complexity of echinococcosis and heterogeneity of clinical cases make necessary a deep understanding of the host-parasite relationships and the parasite phenotype at different developmental stages to reach the best diagnostic tool and to make it accepted in clinical practice. Standardization approaches and a deep understanding of the performance of each of the available antigens in the diagnosis of echinococcosis for the different clinical pictures are also needed. The detection of the parasite in definitive hosts is also reviewed in this chapter. Finally, the different methods for the detection of parasite DNA in different analytes and matrices are also reviewed.

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.

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.

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.

MHC-DRB1/DQB1 Gene Polymorphism and Its Association with Resistance/Susceptibility to Cystic Echinococcosis in Chinese Merino Sheep

The aim of this study was to analyze the relationship between polymorphism of the MHC-DRB1/DQB1 gene and its resistance to Cystic Echinococcosis (C.E), as well as to screen out the molecular genetic marker of antiechinococcosis in Chinese Merino sheep. The MHCII-DRB1/DQB1 exon 2 was amplified by polymerase chain reaction (PCR) from DNA samples of healthy and hydatidosis sheep. PCR products were characterized by restriction fragment length polymorphism (RFLP) technique. Five restriction enzymes (Mval, HaeIII, SacI, SacII, and Hin1I) were employed to cut DRB1, while seven restriction enzymes (MroxI, ScaI, SacII, NciI, TaqI, Mval, and HaeIII) were employed to cut DQB1.Results showed that frequencies of patterns Mvalbb (P < 0.01), SacIab in DRB1 exon 2 (P < 0.05), and TaqIaa, HaeIIInn (P < 0.01) in DQB1 exon 2 were significantly higher in the healthy group compared with the C.E individuals, which implied that there was a strong association between these genotypes and hydatidosis resistance or susceptibility. Chi-square test showed that individuals with the genic haplotype DRB1-SacIab/DRB1-Mvalbb/DQB1-TaqIaa/DQB1-HaeIIInn (P < 0.01) were relatively resistant to C.E, while individuals with the genic haplotypes DRB1-Mvalbc/DQB1-Mvalyy/DQB1-TaqIab/DQB1-HaeIIImn (P < 0.01) and DRB1-Mvalbb/DQB1-Mvalcc/DQB1-TaqIab/DQB1-HaeIIImn (P < 0.01) were more susceptible to C.E. In addition, to confirm these results, a fielding experiment was performed with Chinese Merino sheep which were artificially infected with E.g. The result was in accordance with the results of the first study. In conclusion, MHC-DRB1/DQB1 exon 2 plays an important role as resistant to C.E in Chinese Merino sheep. In addition, the molecular genetic marker of antiechinococcosis (DRB1-SacIab/DRB1-Mvalbb/DQB1-TaqIaa/DQB1-HaeIIInn) was screened out in Chinese Merino sheep.

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

Pathogenesis of chronically developing alveolar echinococcosis (AE) is characterized by a continuous, granulomatous, periparasitic infiltration of immune cells surrounding the metacestode of Echinococcus multilocularis (E.multilocularis) in the affected liver. A detailed cytokine and chemokine profile analysis of the periparasitic infiltrate in the liver has, however, not yet been carried out in a comprehensive way all along the whole course of infection in E. multilocularis intermediate hosts. We thus assessed the hepatic gene expression profiles of 18 selected cytokine and chemokine genes using qRT-PCR in the periparasitic immune reaction and the subsequent adjacent, not directly affected, liver tissue of mice from day 2 to day 360 post intra-hepatic injection of metacestode. DNA microarray analysis was also used to get a more complete picture of the transcriptional changes occurring in the liver surrounding the parasitic lesions. Profiles of mRNA expression levels in the hepatic parasitic lesions showed that a mixed Th1/Th2 immune response, characterized by the concomitant presence of IL-12α, IFN-γ and IL-4, was established very early in the development of E. multilocularis. Subsequently, the profile extended to a combined tolerogenic profile associating IL-5, IL-10 and TGF-β. IL-17 was permanently expressed in the liver, mostly in the periparasitic infiltrate; this was confirmed by the increased mRNA expression of both IL-17A and IL-17F from a very early stage, with a subsequent decrease of IL-17A after this first initial rise. All measured chemokines were significantly expressed at a given stage of infection; their expression paralleled that of the corresponding Th1, Th2 or Th17 cytokines. In addition to giving a comprehensive insight in the time course of cytokines and chemokines in E. multilocularis lesion, this study contributes to identify new targets for possible immune therapy to minimize E. multilocularis-related pathology and to complement the only parasitostatic effect of benzimidazoles in AE.

TGF-β and TGF-β/Smad signaling in the interactions between Echinococcus multilocularis and its hosts

Alveolar echinococcosis (AE) is characterized by the development of irreversible fibrosis and of immune tolerance towards Echinococcus multilocularis (E. multilocularis). Very little is known on the presence of transforming growth factor-β (TGF-β) and other components of TGF-β/Smad pathway in the liver, and on their possible influence on fibrosis, over the various stages of infection. Using Western Blot, qRT-PCR and immunohistochemistry, we measured the levels of TGF-β1, TGF-β receptors, and down-stream Smads activation, as well as fibrosis marker expression in both a murine AE model from day 2 to 360 post-infection (p.i.) and in AE patients. TGF-β1, its receptors, and down-stream Smads were markedly expressed in the periparasitic infiltrate and also in the hepatocytes, close to and distant from AE lesions. Fibrosis was significant at 180 days p.i. in the periparasitic infiltrate and was also present in the liver parenchyma, even distant from the lesions. Over the time course after infection TGF-β1 expression was correlated with CD4/CD8 T-cell ratio long described as a hallmark of AE severity. The time course of the various actors of the TGF-β/Smad system in the in vivo mouse model as well as down-regulation of Smad7 in liver areas close to the lesions in human cases highly suggest that TGF-β plays an important role in AE both in immune tolerance against the parasite and in liver fibrosis.

Parasite-specific IL-17-type cytokine responses and soluble IL-17 receptor levels in Alveolar Echinococcosis patients

Alveolar Echinococcosis (AE) caused by the cestode Echinococcus multilocularis, is a severe helminth infection of man, where unrestricted parasite growth will ultimately result in organ failure and fatality. The tissue-infiltrative growth of the larval metacestode and the limited efficacy of available drugs complicate successful intervention in AE; patients often need life-long medication, and if possible, surgical resection of affected tissues and organs. Resistance to AE has been reported, but the determinants which confer protection are not known. ln this study, we analyzed in patients at distinct stages of Alveolar Echirococcosis, that is cured, stable and progressive AE, as well as in infection-free controls, the cellular production and plasma levels of pro-inflammatory cytokines lL-17A, lL-17B, lL-17F and their soluble receptors lL-17RA (slL-17RA) and IL-17RB (sIL-17RB). Significantly elevated levels of IL-17B and slL-17RB were observed, whilst lL-17F and slL-17RA were reduced in patients with AE. Similarly, the cellular production of lL-17F and slL-L7RA in response to E. multilocularis antigens was low in AE patients, while levels of slL-17RB were highly enhanced. These observations suggest immune-modulating properties of E. multitocularis on lL-17 cytokine-mediated pro-inflammatory immune responses; this may facilitate the tissue infiltrative growth of the parasite and its persistence in the human host.

Association of HLA and post-schistosomal hepatic disorder: a systematic review and meta-analysis

Several human genetic variants, HLA antigens and alleles are reportedly linked to post-schistosomal hepatic disorder (PSHD), but the results from these reports are highly inconclusive. In order to estimate overall associations between human genetic variants, HLA antigens, HLA alleles and PSHD, we systematically reviewed and performed a meta-analysis of relevant studies in both post-schistosomal hepatic disorder and post-schistosomal non-hepatic disorder patients. PubMed, Scopus, Google Scholar, The HuGE Published Literature database, Cochrane Library, and manual search of reference lists of articles published before July 2009 were used to retrieve relevant studies. Two reviewers independently selected articles and extracted data on study characteristics and data regarding the association between genetic variants, HLA antigens, HLA alleles and PSHD in the form of 2×2 tables. A meta-analysis using fixed-effects or random-effects models to pooled odds ratios (OR) with corresponding 95% confidence intervals were calculated only if more than one study had investigated particular variation. We found 17 articles that met our eligibility criteria. Schistosoma mansoni and Schistosoma japonicum were reported as the species causing PSHD. Since human genetic variants were only investigated in one study, these markers were not assessed by meta-analysis. Thus, only HLA-genes (a total of 66 HLA markers) were conducted in the meta-analysis. Our meta-analysis showed that human leucocyte antigens HLA-DQB1*0201 (OR=2.64, P=0.018), DQB1*0303 (OR=1.93, P=0.008), and DRB1*0901 (OR=2.14, P=0.002) alleles and HLA-A1 (OR=5.10, P=0.001), A2 (OR=2.17, P=0.005), B5 (OR=4.63, P=0.001), B8 (OR=2.99, P=0.02), and B12 (OR=5.49, P=0.005) serotypes enhanced susceptibility to PSHD, whereas HLA-DQA1*0501 (OR=0.29, P≤0.001) and DQB1*0301 (OR=0.58, P=0.007) were protective factors against the disease. We further suggested that the DRB1*0901-DQB1*0201, DRB1*0901-DQB1*0303 and A1-B8 haplotypes enhanced susceptibility to PSHD, whereas DQA1*0501-DQB1*0301 linkage decreased the risk of PSHD. The result improved our understanding of the association between the HLA loci and PSHD with regard to pathogenic or protective T-cells and provided novel evidence that HLA alleles may influence disease severity.

The role of evolutionarily conserved signalling systems in Echinococcus multilocularis development and host-parasite interaction

Alveolar echinococcosis, one of the most serious and life-threatening zoonoses in the world, is caused by the metacestode larval stage of the fox-tapeworm Echinococcus multilocularis. Mostly due to its accessibility to in vitro cultivation, this parasite has recently evolved into an experimental model system to study larval cestode development and associated host-parasite interaction mechanisms. Respective advances include the establishment of axenic in vitro cultivation systems for parasite larvae as well as culture systems by which the early development of metacestode vesicles from totipotent parasite stem cells can be reconstituted under controlled laboratory conditions. A series of evolutionarily conserved signalling molecules of the insulin, epidermal growth factor and transforming growth factor-beta pathways that are able to functionally interact with corresponding host cytokines have been described in E. multilocularis and most likely play a crucial role in parasite development within the liver of the intermediate host. Furthermore, a whole genome sequencing project has been initiated by which a comprehensive picture on E. multilocularis cell-cell communication systems will be available in due time, including information on parasite cytokines that are secreted towards host tissue and thus might affect the immune response. In this article, an overview of our current picture on Echinococcus signalling systems will be given, and the potential to exploit these pathways as targets for anti-parasitic chemotherapy will be discussed.

Echinococcus multilocularis and its intermediate host: a model of parasite-host interplay

Host-parasite interactions in the E. multilocularis-intermediate host model depend on a subtle balance between cellular immunity, which is responsible for host's resistance towards the metacestode, the larval stage of the parasite, and tolerance induction and maintenance. The pathological features of alveolar echinococcosis. the disease caused by E. multilocularis, are related both to parasitic growth and to host's immune response, leading to fibrosis and necrosis, The disease spectrum is clearly dependent on the genetic background of the host as well as on acquired disturbances of Th1-related immunity. The laminated layer of the metacestode, and especially its carbohydrate components, plays a major role in tolerance induction. Th2-type and anti-inflammatory cytokines, IL-10 and TGF-β, as well as nitric oxide, are involved in the maintenance of tolerance and partial inhibition of cytotoxic mechanisms. Results of studies in the experimental mouse model and in patients suggest that immune modulation with cytokines, such as interferon-α, or with specific antigens could be used in the future to treat patients with alveolar echinococcosis and/or to prevent this very severe parasitic disease.

Echinococcus multilocularis as an experimental model in stem cell research and molecular host-parasite interaction

Totipotent somatic stem cells (neoblasts) are key players in the biology of flatworms and account for their amazing regenerative capability and developmental plasticity. During recent years, considerable progress has been made in elucidating molecular features of neoblasts from free-living flatworms, whereas their role in parasitic species has so far merely been addressed by descriptive studies. Very recently, however, significant advances have been made in the in vitro culture of neoblasts from the cestode Echinococcus multilocularis. The isolated cells proved capable of generating mature metacestode vesicles under laboratory conditions in a manner that closely resembles the oncosphere-metacestode transition during natural infections. Using the established neoblast cultivation protocols, combined with targeted manipulation of Echinococcus genes by RNA-interference, several fundamental questions of host-dependent parasite development can now be addressed. Here, I give an overview of current cultivation techniques for E. multilocularis neoblasts and present experimental approaches to study their function. Furthermore, I introduce the E. multilocularis genome sequencing project that is presently in an advanced stage. The combined input of data from the E. multilocularis sequencing project, stem cell cultivation, and recently initiated attempts to genetically manipulate Echinococcus will provide an ideal platform for hypothesis-driven research into cestode development in the next years.

Immune response of mice with alveolar echinococcosis to therapy with transfer factor, alone and in combination with albendazole

The effect of dialysable leucocyte extract (transfer factor TF) on immune response of mice infected with Echinococcus multilocularis and treated with albendazole (ABZ) was observed. TF administration increased the parasite-suppressed proliferative response of T and B lymphocytes of infected mice from weeks 8 to 12 or 14 post infection (p.i.), respectively, with the most stimulative effect after TF+ABZ therapy. The CD4 T cell presence in the spleen of infected mice with TF or TF+ABZ therapy was increased from weeks 6 to 12 or 14 p.i., respectively. The production of IFN-gamma (Th1 cytokine) after TF or TF+ABZ therapy was significantly higher from weeks 6 to 12 p.i., and during this time, the significantly inhibited IL-5 synthesis (Th2 cytokine) was detected, particularly after TF+ABZ therapy. The superoxide anion (O2-) production in peritoneal macrophages of infected mice treated with TF or TF+ABZ was stimulated from weeks 8 to 18 p.i. The immunomodulative effect of TF reduced the growth of larval cysts till week 14 p.i. with a comparable intensity to the anthelmintic drug ABZ. Combined therapy TF+ABZ resulted in the greatest parasite restriction and reduced the cyst development till the end of the experiment.

Components of the mitogen-activated protein kinase cascade are activated in hepatic cells by Echinococcus multilocularis metacestode

AIM: To explore the effect of Echinococcus multilocularis (E. multilocularis) on the activation of mitogen-activated protein kinase (MAPK) signaling pathways and on liver cell proliferation.

METHODS: Changes in the phosphorylation of MAPKs and proliferating cell nuclear antigen (PCNA) expression were measured in the liver of patients with alveolar echinococcosis (AE). MAPKs, MEK1/2 [MAPK/extracellular signal-regulated protein kinase (ERK) kinase] and ribosomal S6 kinase (RSK) phosphorylation were detected in primary cultures of rat hepatocytes in contact in vitro with (1) E. multilocularis vesicle fluid (EmF), (2) E. multilocularis-conditioned medium (EmCM).

RESULTS: In the liver of AE patients, ERK 1/2 and p38 MAPK were activated and PCNA expression was increased, especially in the vicinity of the metacestode. Upon exposure to EmF, p38, c-Jun N-terminal kinase (JNK) and ERK1/2 were also activated in hepatocytes in vitro, as well as MEK1/2 and RSK, in the absence of any toxic effect. Upon exposure to EmCM, only JNK was up-regulated.

CONCLUSION: Previous studies have demonstrated an influence of the host on the MAPK cascade in E. multilocularis. Our data suggest that the reverse, i.e. parasite-derived signals efficiently acting on MAPK signaling pathways in host liver cells, is actually operating.

Imunomodulative effect of liposomized muramyltripeptide phosphatidylethanolamine (L-MTP-PE) on mice with alveolar echinococcosis and treated with albendazole

The effect of liposomized muramyltripeptide phosphatidylethanolamine (L-MTP-PE) administered separately or with anthelmintic albendazole (ABZ) on cellular immunity of mice with alveolar echinococcosis was studied. The proliferative activity of splenic T and B lymphocytes was the most stimulated after combined L-MTP-PE + ABZ therapy [from weeks 8 to 14 post-infection (p.i.)] that also induced a long-term development of protective Th1 response (the highest serum concentration of IFN-gamma from weeks 8 to 18 p.i.). On the contrary, Th2 response (cytokine IL-5) in infected mice treated with L-MTP-PE was inhibited since week 8 p.i., but a significant long-term decrease in IL-5 concentration was found after combined L-MTP-PE+ABZ therapy until the end of the experiment (until week 26 p.i.). L-MTP-PE stimulated the production of superoxide anion (O2-) by peritoneal macrophages from weeks 8 to 12 p.i., but the highest O2- production was accordingly recorded after therapy L-MTP-PE+ABZ from weeks 8 to 18 p.i. Stimulation of cellular immunity of mice with alveolar echinococcis with L-MTP-PE and an interaction with ABZ's anti-parasitic effect resulted in the greatest and long-term reduction of growth of Echinococcus multilocularis cysts in the host from week 10 p.i. until the end of the experiment.

Association between hepatic alveolar echinococcosis and frequency of human leukocyte antigen class I and II alleles in Turkish patients

BACKGROUND

Human alveolar echinococcosis (AE) is a potentially fatal, chronically progressive hepatic infestation that is characterized by a long asymptomatic period in which an invasive tumor-like lesion develops. Several studies have suggested that genetic susceptibility to AE may be linked to HLA class II alleles. We investigated the association between AE and antigen HLA-A, B, C, DR and DQ profiles of patients with hepatic AE (HAE) in the eastern part of Turkey.

METHODS

This case-controlled study was performed on 44 unrelated patients with HAE and 76 control subjects. The diagnosis was supported by clinical, radiological, and histopathological evidence. The association of class I and class II HLA antigens was examined in the patients with HAE and control subjects.

RESULTS

There was an increase in the antigen frequencies of HLA-DRB1*15, HLA-DQB1*02, 06, 07 in the HAE patientscompared with those in the control group (P < 0.05, P < 0.001, P < 0.01, P < 0.05, respectively). HLA-DQB1*02, 06, 07 were more frequent in patients with stages III and IV who were classified according to the PNM staging system.

CONCLUSIONS

The present study indicates that susceptibility to HAE in the Turkish population is essentially HLA class II and poorly class I mediated, with HLA-26, and DRB1*015, DQB1* 02, 06, 07 with more allele distribution in the patient group. Our results are not similar to those of other studies, but contribute to the discussions on the association of HLA class I and class II alleles with AE.

The immunodiagnosis of Echinococcus multilocularis infection

Alveolar echinococcosis (AE) is a severe zoonotic disease caused by the metacestode stage of Echinococcus multilocularis. The infection can have fatal consequences in humans if treatment is not provided, so early diagnosis is fundamental for initiating treatment and reducing morbidity and mortality. In addition, detection of the parasite in the definitive host plays a central role in epidemiological studies and surveillance programmes for control of AE. This review presents an overview of the present situation regarding the immunodiagnosis of E. multilocularis infection. Special attention is given to the description of the native, partially purified and recombinant antigens available currently for immunodiagnostic purposes. Recent advances in the primary serodiagnosis and follow-up of AE patients are highlighted, including the detection of specific cytokine profiles. Progress in the immunodiagnosis of intestinal E. multilocularis infection in definitive hosts, particularly the detection of excretory-secretory and integument products of the worm in faeces (copro-antigens) by ELISA, is also discussed.

Echinococcus multilocularis metacestode extract triggers human basophils to release interleukin-4

Infections with parasitic helminths are associated with a T helper 2 (Th2) immune response and IgE production. The underlying mechanism, however, is only partially understood. Recently we have isolated a protein from extracts of Schistosoma mansoni eggs that triggers human basophils from non-sensitized donors to release interleukin-4 (IL-4), the key cytokine of a Th2 response. We called this protein IPSE (for IL-4-inducing principle from Schistosoma mansoni eggs). Supposing that IPSE-like IL-4-inducing activities might be a general principle shared among different helminth species, we investigated extracts from the cestode E. multilocularis for its effect on human basophils. Our results showed that extracts from metacestodes of E. multilocularis cause basophil degranulation, as well as the secretion of histamine, IL-4 and IL-13, in a dose-dependent manner. IgE stripping and resensitization of basophils indicated that the mechanism of IL-4 induction requires the presence of IgE on the cells. Since analogous properties have been demonstrated earlier for IPSE, we think that S. mansoni and E. multilocularis may induce a Th2 response in their hosts via a related mechanism, namely, by the induction of IL-4 release from basophils.

Echinococcosis and allergy

The larval stages of Echinococcus granulosus and E. multilocularis are involved in parasitic diseases in humans: cystic echinococcosis (CE) ("hydatid disease") and alveolar echinococcosis (AE), respectively. Both diseases and parasites have tight links with allergy because of the immunological characteristics that contribute to maintain the larvae in their human host as well as their potential in inducing clinical anaphylactic reactions in some patients. Clinical observations in patients and data obtained from mass screenings in various countries have identified both forms of echinococcosis as "polar diseases," i.e., diseases where immunological background of the patients was related to the clinical presentation and course. In particular, abortive cases (i.e., spontaneous cures) have been found in many subjects in endemic areas. On the other hand, immune suppression was associated with severe disease. AE especially might be considered as an opportunistic infection. Experimental and clinical studies have shown that Th1-related immune response was associated with protection and Th2-related response was associated with parasite growth. Genetic characteristics of the host are related to both occurrence and severity of AE and are associated with the extent of IL-10 secretion, which is a major feature of chronic progressing echinococcosis. Anaphylactic reactions, including urticaria, edema, respiratory symptoms, and anaphylactic shock due to spontaneous or provoked rupture of the parasitic cyst, are well known in CE. Anaphylactic reactions in AE are far less frequent, and have been observed in rare cases at time of metastatic dissemination of the parasitic lesions. Echinococcus-specific IgE is present in most of the patients and associated with severity. Specific histamine release by circulating basophils stimulated with E. granulosus antigens is present in all patients with CE and AE. Echinococcus allergens include (1) AgB 12-kDa subunit, a protease inhibitor and a potent Th2 inducer; (2) Ag5, a serine protease; (3) EA 21, a specific cyclophilin, with a homology with other types of cyclophilins; (4) Eg EF-1 beta/delta an elongation factor, with a homology with Strongyloides stercoralis EF that shares the same IgE epitope. A clinical cross-reaction with Thiomucase, a mucopolysaccharidase used in arthritis treatment, has recently been published. However, despite the potential risk of allergic reactions, the dogma "never puncture a hydatid cyst" is no longer valid. International experience of therapeutic technique of "puncture, aspiration, injection, re-aspiration" of hydatid cysts developed at the beginning of the 1980s has proved to be successful in a variety of selected indications that have been reviewed by WHO recommendations. A better understanding of the immunological background of echinococcosis in humans has led to new therapeutic developments, such as immunomodulation using interferon alpha. Th2-driven immunological response and IL-10-related tolerance state are common characteristics of atopic allergy and echinococcosis. The example of echinococcosis stresses the ambiguous links that exist between parasitic and allergic diseases, and show the usefulness of comparing these diseases to better understand how immune deviation may lead to pathological events and to find new therapeutic and.or preventive agents.

HLA alleles, IFN-gamma responses to HPV-11 E6, and disease severity in patients with recurrent respiratory papillomatosis

Recurrent respiratory papillomatosis (RRP) remains an immunologic enigma. Human papillomavirus (HPV) types 6 and 11 are the predominant HPV viruses that cause papilloma development. However, it is unclear why only a very small fraction of HPV-exposed individuals develop RRP. We performed high-resolution HLA class I and II genotyping on 70 randomly selected patients (56 Caucasians and 14 African-Americans) with RRP. We report, for the first time, an increased frequency of HLA-DRB1*0102 in Caucasian patients with RRP, suggesting that this allele predisposes individuals to RRP. Additionally, HLA-DRB1*0301, DQB1*0201, and DQB1*0202 alleles were selectively enriched in Caucasians with severe disease, suggesting that these alleles may regulate disease severity. In contrast, HLA-DQB1*0602 was more frequent in controls than in Caucasians with severe disease, suggesting a severity-sparing effect of this allele. Furthermore, both DQB1*0201 and DQB1*0202 were enriched, whereas DQB1*0602 was absent, in African-Americans. Interestingly, HLA-DRB1*0301 and DQB1*0201 correlated with reduced interferon-gamma expression in patients with RRP. Larger studies are needed to identify other class II major histocompatibility complex alleles that may influence disease predisposition, disease severity, or both, especially in African-American patients, to ultimately illuminate the regulatory effects of these alleles in the predisposition and severity of RRP.

Echinococcus multilocularis

PURPOSE OF REVIEW

Echinococcus multilocularis is a tapeworm of foxes that may cause a zoonotic infection resulting in a highly pathogenic and potentially fatal chronic liver infestation called human alveolar echinococcosis. Radical liver resection currently offers the only potential cure. Although alveolar echinococcosis is a rare parasitic disease that is restricted to transmission in the northern hemisphere, the parasite is geographically widespread being distributed from Alaska, across Canada and north central USA, through northern Europe and Eurasia to Japan. The present review summarizes the background to this helminthic infection and recent contributions in areas of pathology, diagnosis, treatment and transmission.

RECENT FINDINGS

Concern is growing in Europe that the prevalence and distribution of E. multilocularis in red foxes has increased significantly in the last 10-15 years. A retrospective analysis revealed >550 cases of human alveolar echinococcosis diagnosed between 1982-2000, with the majority in France, Germany and Switzerland. Human prevalence rates >3% occur in central northwest China and the disease is of public health concern in northern Japan. Improvements in immunodiagnosis with native and recombinant antigens have enabled more accurate confirmation of hepatic image findings, while development of in-vitro culture of metacestode tissues provides a useful model for screening new anti-alveolar echinococcosis drugs as alternatives to albendazole and surgery. Recombinant molecules from the oncosphere and metacestode stages have shown potential as vaccine candidates. New tools of coproantigen and copro-DNA detection for vulpine infections have proved highly beneficial in epidemiological and transmission ecology studies, as has a landscape ecology approach to develop risk models for communities in endemic areas.

SUMMARY

It is possible that human AE will become an emergent zoonosis in some regions of Europe and Eurasia. Improvements in diagnostic and treatment approaches are being investigated. Further understanding of host immune responses will aid in characterization of disease pathology. Control of E. multilocularis in its natural cycles will be difficult due to the involvement of wild animal hosts, however use of anthelminthic baits and dosing of domestic dogs may reduce transmission at local scales.

The ambiguous role of immunity in echinococcosis: protection of the host or of the parasite?

In Echinococcus infection, at the metacestode stage, studies of the immune responses in the experimental murine model as well as in humans have shown that (1) cellular immunity induced by a Th1-type cytokine secretion was able to successfully kill the metacestode at the initial stages of development; (2) antigenic proteins and carbohydrates (and perhaps non-antigenic, mitogenic components) of the oncosphere/metacestode were able to interfere with antigen presentation and cell activation so that host lymphocytes and other immune cells could produce cytokines (especially IL-10) and other mediators able to inhibit the effector phase of cellular immune reaction; and (3) immunogenetic characteristics of the host were essential to this parasite-induced deviation of the immune response. In E. multilocularis infection, a combined Th1 and Th2 cytokine profile appears crucial for prolonged metacestode growth and survival. It may be hypothesized that Th1 cytokines promote the initial cell recruitment around the metacestode and are involved in the chronicity of the cell infiltrate leading to a fully organized periparasitic granuloma and its consequences, fibrosis and necrosis. The Th2 cytokines, on the other hand, could be responsible for the inhibition of a successful parasite killing especially because of the 'anti-inflammatory' potency of IL-10. This combination of various arms of the immune response results in a partial protection of both Echinococcus metacestode and host. However, it may also be considered responsible for several complications of the disease. The Th2-related IgE synthesis and mast cell activation, well known to be responsible for anaphylactic reactions in cystic echinococcosis, are more rarely involved in 'allergic' complications in alveolar echinococcosis (AE). However, the partial but chronic effects of the efficient Th1-related cellular immune response are responsible for cytotoxic events which both help metacestode growth and dissemination and lead to the central necrosis of the lesions and clinical complications of AE. Moreover, the Th-1 response is responsible for the major and irreversible fibrosis which leads to bile duct and vessel obstruction. In addition, the peri-parasitic fibrosis may be one of the reasons for the relative lack of efficacy of antiparasitic drugs. Modulation of the host immune response, by using Interferon alpha for instance, may be a new tool to generate an effective immune response against the parasite and to prevent AE and its complications.