Echinococcus multilocularis: relationship between susceptibility/resistance and liver fibrogenesis in experimental mice

Endogenous IL-33 Accelerates Metacestode Growth during Late-Stage Alveolar Echinococcosis

During the course of the infectious disease alveolar echinococcosis (AE), the larval stage of Echinococcus multilocularis develops in the liver, where an initial Th1/Th17 immune response may allow its elimination in resistant individuals. In patients susceptible to infection and disease, the Th2 response initiates later, inducing tolerance to the parasite. The role of interleukin 33 (IL-33), an alarmin released during necrosis and known to drive a Th2 immune response, has not yet been described during AE. Wild-type (WT) and IL-33-/- C57BL/6J mice were infected by peritoneal inoculation with E. multilocularis metacestodes and euthanized 4 months later, and their immune response were analyzed. Immunofluorescence staining and IL-33 enzyme-linked immunosorbent assay (ELISA) were also performed on liver samples from human patients with AE. Overall, metacestode lesions were smaller in IL-33-/- mice than in WT mice. IL-33 was detected in periparasitic tissues, but not in mouse or human serum. In infected mice, endogenous IL-33 modified peritoneal macrophage polarization and cytokine profiles. Th2 cytokine concentrations were positively correlated with parasite mass in WT mice, but not in IL-33-/- mice. In human AE patients, IL-33 concentrations were higher in parasitic tissues than in distant liver parenchyma. The main sources of IL-33 were CD31+ endothelial cells of the neovasculature, present within lymphoid periparasitic infiltrates together with FOXP3+ Tregs. In the murine model, periparasitic IL-33 correlated with accelerated parasite growth putatively through the polarization of M2-like macrophages and release of immunosuppressive cytokines IL-10 and transforming growth factor β1 (TGF-β1). We concluded that IL-33 is a key alarmin in AE that contributes to the tolerogenic effect of systemic Th2 cytokines. IMPORTANCE Infection with the metacestode stage of Echinococcus multilocularis, known as alveolar echinococcosis, is the most severe cestodosis worldwide. However, less than 1% of exposed individuals, in which the immune system is unable to control the parasite, develop the disease. The factors responsible for this interindividual variability are not fully understood. In this in vivo study comparing wild-type and IL-33-/- infected mice, together with data from human clinical samples, we determined that IL-33, an alarmin released following tissue injury and involved in the pathogenesis of cancer and asthma, accelerates the progression of the disease by modulating the periparasitic microenvironment. This suggests that targeting IL-33 could be of interest for the management of patients with AE, and that IL-33 polymorphisms could be responsible for increased susceptibility to AE.

Morphological justification of organ-preserving methods of surgical treatment of patients with liver echinococcosis

The purpose of the research is the study of the morphological structure of echinococcal cysts to assess the possibility of using organ-preserving methods of surgical treatment.Materials and methods. A clinical, instrumental, and morphological fundamental study was performed in the Surgical Clinic of the Botkin Hospital when radiation and morphological data in addition to clinical data were studied for 28 patients who underwent surgical treatment for liver echinococcosis. Excised gross specimens were examined to study the capsule structure, and the penetration of germinal elements of the cysts through membranes of the parasite (64 successively excised primary operated echinococcal cysts).Results and discussion. The fibrous capsule of the echinococcal cyst is a good barrier against Protoscolexes penetrating into the liver tissue. None of the 64 specimens studied in detail was found to have germinal elements of any echinococcal cyst penetrating through its fibrous capsule. The morphological justification of organ-preserving methods in the treatment of patients with liver echinococcosis allows a conclusion that these interventions are safe and radical.

Understanding pathogen–host interplay by expression profiles of lncRNA and mRNA in the liver of Echinococcus multilocularis-infected mice

Almost all Echinococcus multilocularis (Em) infections occur in the liver of the intermediate host, causing a lethal zoonotic helminthic disease, alveolar echinococcosis (AE). However, the long non-coding RNAs (lncRNAs) expression profiles of the host and the potential regulatory function of lncRNA during Em infection are poorly understood. In this study, the profiles of lncRNAs and mRNAs in the liver of mice at different time points after Em infection were explored by microarray. Thirty-one differentially expressed mRNAs (DEMs) and 68 differentially expressed lncRNAs (DELs) were found continuously dysregulated. These DEMs were notably enriched in “antigen processing and presentation”, “Th1 and Th2 cell differentiation” and “Th17 cell differentiation” pathways. The potential predicted function of DELs revealed that most DELs might influence Th17 cell differentiation and TGF-β/Smad pathway of host by trans-regulating SMAD3, STAT1, and early growth response (EGR) genes. At 30 days post-infection (dpi), up-regulated DEMs were enriched in Toll-like and RIG-I-like receptor signaling pathways, which were validated by qRT-PCR, Western blotting and downstream cytokines detection. Furthermore, flow cytometric analysis and serum levels of the corresponding cytokines confirmed the changes in cell-mediated immunity in host during Em infection that showed Th1 and Th17-type CD4+ T-cells were predominant at the early infection stage whereas Th2-type CD4+ T-cells were significantly higher at the middle/late stage. Collectively, our study revealed the potential regulatory functions of lncRNAs in modulating host Th cell subsets and provide novel clues in understanding the influence of Em infection on host innate and adaptive immune response.

Co-administration of silymarin elevates the therapeutic effect of praziquantel through modulation of specific antibody profiles, Th1/Th2/Tregs cytokines and down-regulation of fibrogenesis in mice with Mesocestoides vogae (Cestoda) infection

Silymarin (SIL) represents a natural mixture of polyphenols showing an array of health benefits. The present study, carried out on a model cestode infection induced by Mesocestoides vogae tetrathyridia in the ICR strain of mice, was aimed at investigating the impact of SIL as adjunct therapy on the activity of praziquantel (PZQ) in relation to parasite burden, immunity and liver fibrosis within 20 days post-therapy. In comparison with PZQ alone, co-administration of SIL and PZQ stimulated production of total IgG antibodies to somatic and excretory-secretory antigens of metacestodes and modified the expression patterns of immunogenic molecules in both antigenic preparations. The combined therapy resulted in the elevation of IFN-γ and a decline of TNF-α and TGF-β1 in serum as compared to untreated group; however, SIL attenuated significantly the effect of PZQ on IL-4 and stimulated PZQ-suppressed phagocytosis of peritoneal macrophages. In the liver, SIL boosted the effect of PZQ on gene expression of the same cytokines in a similar way as was found in serum, except for down-regulation of PZQ-stimulated TNF-α. Compared to PZQ therapy, the infiltration of mast cells into liver after SIL co-administration was nearly abolished and correlated with suppressed activities of genes for collagen I, collagen III and α-SMA. In conclusion, co-administration of SIL modified the effects of PZQ therapy on antigenic stimulation of the immune system and modulated Th1/Th2/Tregs cytokines. In liver this was accompanied by reduced fibrosis, which correlated with significantly higher reduction of total numbers of tetrathyridia after combined therapy as compared with PZQ treatment.

Role of stellate cells in hepatic echinococcosis in cattle

Hydatid cysts formed by the metacestodes of Echinococcus granulosus. Cattle suffering from hydatid cyst shows fluid-filled structures, especially in liver. These parasite-induced cysts localized by forming fibrous capsules in the liver. Fibrogenesis is the host immune response in the liver against these parasites. Hepatic stellate cells (HSCs) are localized perisinusoidal space also known as vitamin A-storing cells, characterize the important fibrogenic cell type. In this study, livers from 15 animals with hydatid cyst and 8 healthy animals were used. Hematoxylin and Eosin, masson trichrome staining were performed on the prepared liver sections. Microscopically, cysts were bordered eosinophilic necrotic debris blended with degenerate neutrophils, macrophages, eosinophils, lymphocytes, plasma cells and multinucleated giant cells, which extend into the adjacent fibrous connective tissue. In Masson trichrome staining, the fibrous connective tissue was observed surrounding of hydatid cyst. Glial fibrillary acidic protein (GFAP), collagen I, GFAP/collagen I, positive cells were investigated using either indirect single- or double-labeling immunohistochemical staining. The results indicated that anti-GFAP-positive staining was seen in areas including fibrous tissue just under the foreign body giant cells surrounding the cyst wall. In double immunohistochemical staining, it was observed that HSCs labeled with anti-GFAP antibody in the fibrous connective tissue also labeled anti-collagen I antibody. This study shows that HSCs may responsible for synthesis the collagen I in the development of parasitic fibrosis in cystic echinococcosis in the liver of cattle.

The proangiogenic role of polymorphonuclear myeloid-derived suppressor cells in mice infected with Echinococcus granulosus

The aim of this study was to first evaluate the proangiogenic activity of polymorphonuclear myeloid-derived suppressor cells (PMN-MDSC) in mice infected with Echinococcus granulosus. PMN-MDSCs derived from experimentally infected mice were collected and cultured in vitro, and their effect on angiogenesis was investigated using a human umbilical vein endothelial cell (HUVEC) tube-formation assay stimulated with the supernatant by microscope and the Angiogenesis module of the software NIH Image J. In addition, the expression levels of several functional factors related to proangiogenic activity were analyzed. The results showed that vascular endothelial growth factor (VEGF) was increased in the serum from infected mice, and the PMN-MDSCs expressed VEGF directly. The culture supernatant from PMN-MDSCs significantly promoted HUVECs to form tubes. VEGF mRNA was higher and soluble fms-like tyrosine kinase-1 levels were lower, in PMN-MDSCs from infected mice than in those from control mice. In conclusion, host angiogenesis in mice infected with E. granulosus appeared to be promoted by PMN-MDSCs. Other specific angiogenic factors derived from PMN-MDSCs and parasites in the microenvironment of infection foci should be clarified in further studies, in order to provide more information for the prophylaxis and treatment of echinococcosis.

T-cell tolerance and exhaustion in the clearance of Echinococcus multilocularis: role of inoculum size in a quantitative hepatic experimental model

The local immune mechanisms responsible for either self-healing or sustained chronic infection are not clear, in the development of E. multilocularis larvae. Here, we developed a suitable experimental model that mimics naturally infected livers, according to the parasite load. We demonstrated that local cellular immunity and fibrogenesis are actually protective and fully able to limit metacestode growth in the liver of low or medium dose-infected mice (LDG or MDG), or even to clear it, while impairment of cellular immunity is followed by a more rapid and severe course of the disease in high dose-infected mice (HDG). And recruitment and/ or proliferation of memory T cells (including CD4 Tem, CD8 Tcm and CD8 Tem) and imbalance of T1/T2/T17/Treg-type T cells in liver were not only associated with clearance of the parasite infection in LDG, but also with increased hepatic injury in HDG; in particular the dual role of CD8 T cells depending on the parasite load and the various stages of metacestode growth. Besides, we first demonstrate the association between LAG3- or 2B4-expressing T cells exhaustion and HD inocula in late stages. Our quantitative experimental model appears fully appropriate to study immunomodulation as a therapeutic strategy for patients with Alveolar Echinococcosis.

Echinococcus-Host Interactions at Cellular and Molecular Levels

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

Visualization and Pathological Characteristics of Hepatic Alveolar Echinococcosis with Synchrotron-based X-ray Phase Sensitive Micro-tomography

Propagation-based phase-contrast computed tomography (PPCT) utilizes highly sensitive phase-contrast technology applied to X-ray micro-tomography, especially with the extensive use of synchrotron radiation (SR). Performing phase retrieval (PR) on the acquired angular projections can enhance image contrast and enable quantitative imaging. We employed the combination of SR-PPCT and PR for the histopathological evaluation of hepatic alveolar echinococcosis (HAE) disease and demonstrated the validity and superiority of PR-based SR-PPCT. A high-resolution angular projection data set of a human postoperative specimen of HAE disease was acquired, which was processed by graded ethanol concentration fixation (GECF). The reconstructed images from both approaches, with the projection data directly used and preprocessed by PR for tomographic reconstruction, were compared in terms of the tissue contrast-to-noise ratio and density spatial resolution. The PR-based SR-PPCT was selected for microscale measurement and the 3D visualization of HAE disease. Our experimental results demonstrated that the PR-based SR-PPCT technique is greatly suitable for the discrimination of pathological tissues and the characterization of HAE. In addition, this new technique is superior to conventional hospital CT and microscopy for the three-dimensional, non-destructive microscale measurement of HAE. This PR-based SR-PPCT technique has great potential for in situmicroscale histopathological analysis and diagnosis, especially for applications involving soft tissues and organs.

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.

Cysticercus fasciolaris infection in wild rats (Rattus norvegicus) in Korea and formation of cysts by remodeling of collagen fibers

Cysticercus fasciolaris, the larval form of Taenia taeniaeformis, is commonly encountered in rodents. In our study, 287 wild rats ( Rattus norvegicus) in South Korea were examined in 2010 and 2011. Of 287 rats, 97 (33.8%) were infected with C. fasciolaris. A strong positive correlation was found between the host body weight and prevalence in both sexes, regardless of the year of collection. The liver was the most common habitat of the parasite, and the lung was the most frequent ectopic region, followed by mesentery, pleura, abdominal wall, and kidney. The lesions of the affected organs were generally characterized by well-developed cysts, each containing a larva. However, the cysts within kidney and abdominal wall were poorly organized, filled with abscess, and lacked larvae. Collagen types I and III, but not type IV, played significant roles in constructing the cysts at differential stages, addressed by immunohistochemistry. During cyst wall development, both collagen types contributed equally to cyst formation at the early stage, whereas collagen type I was the major component at the late stage ( p < 0.05). In early-stage cysts, distribution of collagens was interestingly differential depending on the development stage, as collagen type I was localized in the outer layer and type III was located in the inner layer. Our results suggest that an appropriate remodeling process of collagen fibers is necessary for C. fasciolaris to build the well-conditioned cysts in the target organs for survival.

Assessment of Vascularity in Hepatic Alveolar Echinococcosis: Comparison of Quantified Dual-Energy CT with Histopathologic Parameters

Purpose

To investigate whether dual-energy computer tomography(DECT) could determine the angiographic vascularity of alveolar echinococcosis lesions by comparing the quantitative iodine concentration (IC) with the microvascular density (MVD).

Material and Methods

Twenty-five patients (16 men, 9 women; mean age, 40.9 ± 13.8 years) with confirmed hepatic alveolar echinococcosis (HAE) underwent DECT of the abdomen, consisting of arterial phase (AP), portal venous phase (PVP), and delayed phase (DP) scanning, in dual-source mode (100 kV/140 kV). Image data were processed with a DECT software algorithm that was designed for the evaluation of iodine distribution in the different layers (marginal zone, solid and cystic) of the lesions. The CT patterns of HAE lesions were classified into three types: solid type, pseudocystic type and ‘geographic map’ (mixed) type. The IC measurements in different layers and different types of lesions were statistically compared. MVD was examined using CD34 immunohistochemical staining of the resected HAE tissue and scored based on the percentage of positively stained cells and their intensity. Pearson’s correlation analysis was used to evaluate the potential correlation between DECT parameters and MVD.

Results

A total of 27 HAE lesions were evaluated, of which 9 were solid type, 3 were pseudocystic type and 15 were mixed type. The mean lesion size was 100.7 ± 47.3 mm. There was a significant difference in the IC measurements between different layers of HAE lesions during each scan phase (p < 0.001). The IC in the marginal zone was significantly higher than in the solid and cystic components in AP (2.15 mg/mL vs. 0.17 or 0.01 mg/mL), PVP (3.08 mg/mL vs. 0.1 or 0.02 mg/mL), and DP (2.93 mg/mL vs. 0.04 or 0.02 mg/mL). No significant difference was found among the different CT patterns of HAE lesions. Positive expression of CD34 in the marginal zones surrounding HAE lesions was found in 92.5% (25/27) of lesions, of which 18.5% (5/27) were strongly positive, 62.7% (17/27) were moderately positive, and 11.1% (3/27) were weakly positive. In contrast, 7.4% (2/27) of the lesions were negative for CD34. There was a positive correlation between IC measurements and MVD in the marginal zone of HAE lesions (r = 0.73, p < 0.05).

Conclusions

The DECT quantitative iodine concentration was significantly correlated with MVD in the marginal zones surrounding HAE lesions. Dual-energy CT using a quantitative analytic methodology can be used to evaluate the vascularity of AE.

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.

Proline modulates the effect of bisphosphonate on calcium levels and adenosine triphosphate production in cell lines derived from bovine Echinococcus granulosus protoscoleces

Bisphosphonates have been proposed as pharmacological agents against parasite and cancer cell growth. The effect of these compounds on helminthic cell viability and acellular compartment morphology, however, has not yet been studied. The effects of different types of bisphosphonates, namely etidronate (EHDP), pamidronate (APD), alendronate (ABP), ibandronate (IB) and olpadronate (OPD), and their interaction with amiloride, 1,25-dihydroxycholecalciferol (D3) and proline were evaluated on a cell line derived from bovine Echinococcus granulousus protoscoleces (EGPE) that forms cystic colonies in agarose. The EGPE cell line allowed testing the effect of bisphosphonates alone and in association with other compounds that could modulate calcium apposition/deposition, and were useful in measuring the impact of these compounds on cell growth, cystic colony formation and calcium storage. Decreased cell growth and cystic colony formation were found with EHDP, IB and OPD, and increased calcium storage with EHDP only. Calcium storage in EGPE cells appeared to be sensitive to the effect of amiloride, D3 and proline. Proline decreased calcium storage and increased colony formation. Changes in calcium storage may be associated with degenerative changes of the cysts, as shown in the in vitro colony model and linked to an adenosine triphosphate (ATP) decrease. In conclusion, bisphosphonates could be suitable tempering drugs to treat cestode infections.

Hypoxia-inducible factor 1-regulated lysyl oxidase is involved in Staphylococcus aureus abscess formation

Hypoxia-inducible factor 1 (HIF-1) is the key transcription factor involved in the adaptation of mammals to hypoxia and plays a crucial role in cancer angiogenesis. Recent evidence suggests a leading role for HIF-1 in various inflammatory and infectious diseases. Here we describe the role of HIF-1 in Staphylococcus aureus infections by investigating the HIF-1-dependent host cell response. For this purpose, transcriptional profiling of HIF-1α-deficient HepG2 and control cells, both infected with Staphylococcus aureus, was performed. Four hours after infection, the expression of 190 genes, 24 of which were regulated via HIF-1, was influenced. LOX (encoding lysyl oxidase) was one of the upregulated genes with a potential impact on the course of S. aureus infection. LOX is an amine oxidase required for biosynthetic cross-linking of extracellular matrix components. LOX was upregulated in vitro in different cell cultures infected with S. aureus and also in vivo, in kidney abscesses of mice intravenously infected with S. aureus and in clinical skin samples from patients with S. aureus infections. Inhibition of LOX by β-aminopropionitrile (BAPN) did not affect the bacterial load in kidneys or blood but significantly influenced abscess morphology and collagenization. Our data provide evidence for a crucial role of HIF-1-regulated LOX in abscess formation.

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.

Assessment of early hepatic echinococcus multilocularis infection in rats with real-time contrast-enhanced ultrasonography

The aim of this study was to demonstrate characteristic imaging and accurate evaluation of blood perfusion in early stage of hepatic alveolar echinococcosis (HAE) by contrast-enhanced ultrasonography (CEUS). The early stage of experimentally induced secondary HAE in 45 rats was studied. Thirty-six HAE lesions in 33 rats, confirmed by pathologic examination, were examined by ultrasound (US), color Doppler flow imaging (CDFI) and then CEUS. Thirty-three lesions were found in 30 rats by US, and 30 lesions were detected in 27 rats by CEUS. The sensitivity of US and CEUS was 92% (95% CI 76%-98%) and 82% (95% CI 65%-93%), respectively. US imaging characteristics were categorized into four types: hyperechoic spot (type 1, 45.5%, 15/33), granular hyperechoic spots (type 2, 12.1%, 4/33), hyperechoic lesion (type 3, 30.3%, 10/33) and mixed pattern (type 4, 12.1%, 4/33). CDFI failed to detect blood flow signals in any lesions. CEUS results for 30 lesions showed ring enhancement in the peripheral area during the arterial phase and no filling effect in either the portal or the delayed phase (46.7%, 14/30); ring enhancement combined with central septa enhancement during the arterial phase and portal venous phase (46.7, 14/30), and no enhancement (6.6%, 2/30). The enhanced area, confirmed by pathologic examination, was an inflammatory reaction belt surrounding the lesion. The results of this study suggest that US, with high sensitivity, can be used as a screening method for early HAE lesions in the animal model, while CEUS can be used for displaying the peripheral blood perfusion and vesicle structure.

Hepatocyte proliferation/growth arrest balance in the liver of mice during E. multilocularis infection: a coordinated 3-stage course

Background

Alveolar echinococcosis (AE) is characterized by the tumor-like growth of Echinococcus (E.) multilocularis. Very little is known on the influence of helminth parasites which develop in the liver on the proliferation/growth arrest metabolic pathways in the hepatocytes of the infected liver over the various stages of infection.

Methodology/Principal Findings

Using Western blot analysis, qPCR and immunohistochemistry, we measured the levels of MAPKs activation, Cyclins, PCNA, Gadd45β, Gadd45γ, p53 and p21 expression in the murine AE model, from day 2 to 360 post-infection. Within the early (day 2–60) and middle (day60–180) stages, CyclinB1 and CyclinD1 gene expression increased up to day30 and then returned to control level after day60; Gadd45β, CyclinA and PCNA increased all over the period; ERK1/2 was permanently activated. Meanwhile, p53, p21 and Gadd45γ gene expression, and caspase 3 activation, gradually increased in a time-dependent manner. In the late stage (day180–360), p53, p21 and Gadd45γ gene expression were significantly higher in infected mice; JNK and caspase 3 were activated. TUNEL analysis showed apoptosis of hepatocytes. No significant change in CyclinE, p53 mRNA and p-p38 expression were observed at any time.

Conclusions

Our data support the concept of a sequential activation of metabolic pathways which 1) would first favor parasitic, liver and immune cell proliferation and survival, and thus promote metacestode fertility and tolerance by the host, and 2) would then favor liver damage/apoptosis, impairment in protein synthesis and xenobiotic metabolism, as well as promote immune deficiency, and thus contribute to the dissemination of the protoscoleces after metacestode fertility has been acquired. These findings give a rational explanation to the clinical observations of hepatomegaly and of unexpected survival of AE patients after major hepatic resections, and of chronic liver injury, necrosis and of hepatic failure at an advanced stage and in experimental animals.

Time course of gene expression profiling in the liver of experimental mice infected with Echinococcus multilocularis

BACKGROUND

Alveolar echinococcosis (AE) is a severe chronic parasitic disease which behaves like a slow-growing liver cancer. Clinical observations suggest that the parasite, Echinococcus multilocularis (E. multilocularis) influences liver homeostasis and hepatic cell metabolism. However, this has never been analyzed during the time course of infection in the common model of secondary echinococcosis in experimental mice.

METHODOLOGY/PRINCIPAL FINDINGS

Gene expression profiles were assessed using DNA microarray analysis, 1, 2, 3 and 6 months after injection of E. multilocularis metacestode in the liver of susceptible mice. Data were collected at different time points to monitor the dynamic behavior of gene expression. 557 differentially expressed genes were identified at one or more time points, including 351 up-regulated and 228 down-regulated genes. Time-course analysis indicated, at the initial stage of E. multilocularis infection (month 1-2), that most of up-regulated pathways were related to immune processes and cell trafficking such as chemokine-, mitogen-activated protein kinase (MAPK) signaling, and down-regulated pathways were related to xenobiotic metabolism; at the middle stage (month 3), MAPK signaling pathway was maintained and peroxisome proliferator-activated receptor (PPAR) signaling pathway emerged; at the late stage (month 6), most of up-regulated pathways were related to PPAR signaling pathway, complement and coagulation cascades, while down-regulated pathways were related to metabolism of xenobiotics by cytochrome P450. Quantitative RT-PCR analysis of a random selection of 19 genes confirmed the reliability of the microarray data. Immunohistochemistry analysis showed that proliferating cell nuclear antigen (PCNA) was increased in the liver of E. multilocularis infected mice from 2 months to 6 months.

CONCLUSIONS

E. multilocularis metacestode definitely exerts a deep influence on liver homeostasis, by modifying a number of gene expression and metabolic pathways. It especially promotes hepatic cell proliferation, as evidenced by the increased PCNA constantly found in all the experimental time-points we studied and by an increased gene expression of key metabolic pathways.

Angiogenesis and parasitic helminth-associated neovascularization

Successful metazoan parasitism, among many other factors, requires a supply of nutrients and the removal of waste products. There is a prerequisite for a parasite-defined vasculature. The angiogenic mechanism(s) involved presumably depend on the characteristics of the tissue- and vascular system-dwelling, parasitic helminths. Simplistically, 2 possibilities or a combination of both have been considered in this review. The multifactorial induction of parasitic helminth-associated neovascularization could arise through, either a host-, a parasite- or a host-/parasite-dependent, angiogenic switch. Most studies appear to support the first and third hypotheses, but evidence exists for the intrahepatic cestodeEchinococcus multilocularis, the free-living nematodeCaenorhabditis elegansand the intravascular trematodeSchistosoma mansonifor the second inference. In contrast, the nematode anti-coagulant protein NAPc2 from adultAncylostoma caninumis also an anti-angiogenic factor.

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.

Dynamics of hepatic stellate cells, collagen types I and III synthesis and gene expression of selected cytokines during hepatic fibrogenesis following Mesocestoides vogae (Cestoda) infection in mice

In the present study, the relationship between progression of Mesocestoides vogae infection in the liver of mice, the accumulation rate of collagen types I and III, gene expression of fibrogenic factors and cytokines was examined within 6weeks p.i. Due to asexual multiplication, the total number of larvae in the liver increased considerably and 63.4% were found in collagen capsules on day 42 p.i. Intense staining for both collagens was recorded in the activated hepatic stellate cells (HSCs) throughout the period of this study in the inflammatory lesions. With progressing infection, cellular expression of both collagens was confined to the flat cells, myofibroblasts, which were scattered among collagen fibres in parenchymal lesions and capsules. Collagen-positive areas mirrored immunostaining of alpha-smooth muscle actin (alpha-SMA) in HSCs and myofibroblasts. Gene expression of both collagens increased rapidly within 14days p.i. and their expression pattern resembled that for pro-fibrotic cytokine transforming growth factor (TGF)-beta1 and alpha-SMA protein. IL-10 cytokine expression was up-regulated following day 14 p.i. and that of IL-13 was up-regulated early p.i., then transcription elevated gradually mirroring the activity of other pro-fibrotic markers. In contrast, transcription activity of TNF-alpha and IFN-gamma was elevated shortly after infection, followed by the partial down-regulation of gene expression, indicating the lack of larval killing, enhanced granulomatous inflammation and the perpetuation of hepatic fibrosis. Histomorphometric analysis of the parenchymal fibrous lesions, surface areas of larvae surrounded with the inflammatory infiltrates and surface areas of developing or mature larva-containing granulomas, correlated with the proportion of free and encapsulated larvae, immunostaining and gene expression patterns of collagens and pro-fibrotic markers. At a later stage of infection (day 28 p.i. onwards) collagen I-positive areas occupied a greater surface area and formed mature larval capsules and scars in the liver. In contrast, collagen III was less abundant and was localised mainly in the fibrous lesions in damaged parenchyma, suggesting their specific up-regulation as the part of host-protecting and tissue-healing responses.

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.

Immunomodulative effect of glucan and/or glucan supplemented with zinc in albendazole therapy for murine alveolar echinococcosis

The effect of glucan immunomodulator (GI) and glucan supplemented with zinc (GIZn) administered separately or with albendazole (ABZ) on cellular immunity of mice with alveolar echinococcosis was observed. The stimulative effect of GI and GI + ABZ therapy on proliferative response of T lymphocytes was prolonged by GIZn or GIZn + ABZ from week 6 to 14 postinfection (p.i.). The increased proliferation of B lymphocytes was observed during combined therapies GI + ABZ and GIZn + ABZ from week 6 to 12 p.i. Number of splenic CD4 T cells in mice with GI or GI + ABZ therapy was increased only on weeks 6 and 8 p.i. GIZn and GIZn + ABZ therapy prolonged this stimulation from week 6 to 14 p.i. Serum concentration of interferon-gamma (IFN-gamma) was increased after GIZn therapy and reduced after GI therapy from week 8 to 12 p.i. GIZn + ABZ therapy had the highest effect on the IFN-gamma rise from week 8 to 22 p.i. Both GI and GIZn inhibited the serum concentration of interleukin-5 (IL-5) from week 6 p.i. The production of superoxide anion was increased after GI therapy from week 6 to 14 p.i. and after GI + ABZ or GIZn + ABZ therapies from week 12 to 18 p.i. The most effective antiparasitic therapy for alveolar echinococcosis was reached by GIZn + ABZ therapy.

Praziquantel and liposomized glucan-treatment modulated liver fibrogenesis and mastocytosis in mice infected with Mesocestoides vogae (M. corti, Cestoda) tetrathyridia

Beta-glucans are immunomodulators able to activate innate immunity and to potentiate acquired immune reactions. We investigated the impact of co-administration of liposomized beta-glucan on the larvicidal effect of the anthelmintic praziquantel (PZQ) in the livers and peritoneal cavities in mice infected with Mesocestoides vogae (M. corti). Also, within 2 weeks following therapy (up to day 29 p.i.) we examined collagen synthesis in the livers of mice by means of biochemical determination of hydroxyproline concentration, total mast cell counts and cell proliferative capacity using immunohistochemical and radiometrical methods. After co-administration of liposomized glucan (LG) and PZQ efficacy (%) was significantly higher than after treatment with either compound alone, particularly in the peritoneal cavity compared to the liver. In comparison with the control, more intense collagenesis was found in the B-liver parts (high intensity of infection) and lowering of collagen content in the A-parts (very weak infection). This effect was strongest after LG treatment and co-administration of PZQ abolished the pro-fibrotic effect of LG. In all groups, mast cell counts were higher in the B-liver parts than in the A-parts and the dynamics of mastocytosis was profoundly modulated following therapy. Whereas the effect of PZQ was only moderate, early and very strong onset was seen after LG treatment. Administration of PZQ suppressed LG induced-elevation of mast cells counts in both liver parts. Using DNA S-phase markers (BrdU and 3H-thymidine) the proliferative capacity was shown to be associated with several kinds of liver cells. Therapy significantly stimulated [3H]-thymidine incorporation (cell proliferation) only in the A-parts over that in control, the most after LG administration. In summary (i) the anthelmintic effect of PZQ could be enhanced after simultaneous administration of the immunomodulator beta-glucan entrapped in a liposomal carrier, (ii) intense mastocytosis seen after treatment with LG seems to have a direct role in the glucan's pro-fibrotic activity and can be abolished after co-administration of PZQ in a time-dependent manner, (iii) the pattern of cell proliferation indicates that in the case of PZQ treatment, the reparative processes of liver parenchyma are enhanced in an inverse correlation with the intensity of infection.

Usefulness of severe combined immunodeficiency (scid) and inbred mice for studies of cysticercosis and echinococcosis

The topics in this review are the usefulness of immunodeficient and inbred mice for studies of developmental biology, drug efficacy and host specificity in cysticercosis and echinococcosis. In non-obese diabetic severe combined immunodeficiency (NOD/Shi-scid) mice of both sexes, in vitro hatched oncospheres of all three human taeniid species (Taenia solium, Taenia saginata and Taenia asiatica) developed into cysticerci comparable to or bigger than those developed in their known intermediate host animals, whereas only females were susceptible to these infections in other scid mice of BALB/c, C57BL or C.B-17 inbred strains. Detailed morphological observation from post-oncospheral to cysticercus developmental stages is expected to be easy when we use NOD/Shi-scid mice experimentally inoculated with in vitro hatched oncospheres. Metacestocidal effect of oxfendazole was evaluated in NOD/Shi-scid mice experimentally inoculated with oncospheres of T. solium. In Echinococcus multilocularis infection, larval tissue proliferated without induction of inflammatory host responses in scid mice, thus facilitating isolation of the larval vesicles and protoscoleces for biochemical and molecular biological studies. Trans portal inoculation of metacestode tissues resulted in proliferation of secondary echinococcal foci localized exclusively in the liver without metastasis to other tissues or organs. The advantages of a mouse model for Echinococcus granulosus are also described.

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.

[Long-term followup of patients with alveolar echinococcosis]

INTRODUCTION

Alveolar Echinicoccosis is a severe parasitic disease: its natural evolution is comparable to a slowly progressive malignant liver tumour. There is no definitive medical therapy. Surgery remains the only option to assure a cure. This report is our surgical experience for the care of this affection.

PATIENTS AND METHOD

Between 1980 and 2002, 12 patients were operated for an hepatic alveolar echinococcosis. For 11 of them, the affection was primary. Lesions were located in the right liver lobe (n = 9), in the left lobe (n = 1), in both lobes (n = 1) and close to the hilar region (n = 1). Twice there was a diaphragmatic infiltration and once a pleural infiltration. Resections consisted in: segmentectomies in the right lobe (n = 4), right hepatectomy (n = 5, associated once with a partial I and IV segmentectomy), left hepatectomy (n = 1), one liver transplantation (n = 1), one drainage of a parasitic cavity (n = 1). One pleurectomy and a partial diaphragmatic resection were made. All patients were treated postoperatively with benzimidazole chemotherapy.

RESULTS

Three patients presented some complications: segmental necrosis with biloma (n = 1), biliary fistula tract (n = 1), subdiaphragmatic hematoma (n = 1), cholangitis (n = 1). 10 patients are alive (median follow-up of 10 years). Two patients still present some parasitic lesions; the situation remains doubtful for one of them. Two patients died (one of them in the context of a disease progression).

CONCLUSION

Surgical treatment, associated with medical therapy, assured a control of the parasitic lesions or a definitive cure in most cases. When the disease is limited to the liver with no possibility for partial hepatectomy, a transplantation is an option.

Modulation of liver fibrosis and pathophysiological changes in mice infected with Mesocestoides corti (M. vogae) after administration of glucan and liposomized glucan in combination with vitamin C

The effects of glucan and liposomized glucan, alone or co-administered with vitamin C, and empty liposomes on hepatic fibrosis in mice infected with Mesocestoides corti (M. vogae) tetrathyridia were studied. Preparations were administered every third day from day 7 to day 31 post-infection (p.i.), nine doses in total. Activities of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and cholesterol levels were measured in sera collected on days 11, 15, 21, 28, 32, 42, 50 and 65 p.i. Liver fibrosis was studied on the same days by measuring hydroxyproline concentration, which is considered a marker for collagen content. Larvicidal effects of the glucan and liposome preparations were estimated on day 65 p.i. in the liver and peritoneal cavity. Glucan formulations significantly enhanced collagen content, most prominently after administration of liposomized glucan in combination with vitamin C. Activities of both enzymes and cholesterol levels were slightly modified after administration of glucan alone. Liposomized glucan with vitamin C significantly increased ALT and AST activity and cholesterol levels up to days 28-32 p.i., after which they plateaued or declined. The most pronounced decrease was after administration of liposomized glucan and vitamin C. The same pattern of biochemical parameters in serum was observed after administration of empty liposomes, however, collagen content was not modified significantly. Larval counts in the liver and the peritoneal cavity were significantly reduced after treatment with either glucan formulation, but were unaffected following treatment with empty liposomes. In summary, intense fibrosis in the liver of mice treated with liposomized glucan and vitamin C did not result in the most extensive parenchymal cell injury but, rather in the highest efficacy of treatment. Liposomal lipids were probably utilized in the reparation of the damaged parenchymal cells, while glucan stimulated phagocytic cells.

IFN alpha-2a protects mice against a helminth infection of the liver and modulates immune responses

BACKGROUND & AIMS

Hepatic alveolar echinococcosis (AE), caused by the larval growth of Echinococcus multilocularis, is one of the most lethal helminthic diseases with no satisfactory treatment. Advances in the understanding of the host's immune response (Th2 responses associated with a progressive form of AE), have driven the research towards immune stimulation as an alternative possibility to treat patients. We previously reported clinical stabilization associated with a shift from a Th2 to a Th1 cytokine profile in an AE patient treated with interferon (IFN)alpha.

METHODS

The effects of recombinant IFN alpha-2a were analyzed in the susceptible C57BL/6J E. multilocularis infected mice. Parasitic burden, macrophage functions, and specific T-cell responses were studied 15, 45, and 90 days postinfection.

RESULTS

After 90 days postinfection, 75% of infected IFN alpha-2a-treated mice had no hepatic lesions and half were fully protected. IFN alpha-2a treatment markedly decreased the abnormally elevated production of IL-10 in both spleen cell cultures and peritoneal macrophage cultures from infected mice and restored phagocytosis and oxidative metabolism of macrophages. It also inhibited IL-6 and IL-13 antigen-induced secretions in spleen cell cultures.

CONCLUSIONS

Through its immunoregulatory properties, IFN alpha-2a may be effective in a helminthic liver infection and is a promising candidate for clinical application in AE.

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

Th2 responses, especially IL-10 secretion by circulating mononuclear cells are associated with the progressive form of AE and Th1 responses with resistance. The HLA B8, DR3, DQ2 haplotype is associated with the severity of AE in humans through immune-mediated mechanisms including an elevated production of Interleukin-10 (IL-10). Granulomatous infiltration of mononuclear cells around the parasitic vesicles is a hallmark of this disease; however, cytokine production by granuloma cells has never been studied. Tissue samples were taken in the periparasitic area and in the central area of the periparasitic granulomatous lesions from a patient with a progressive AE at surgery. Six pieces for each zone were incubated in culture medium with antibiotics and IL-2, together with irradiated autologous peripheral blood mononuclear cells as feeder cells. After four days the dead feeder cells were removed by density gradient centrifugation. Lymphocytes were stimulated with Echinococcus multilocularis vesicular fluid antigen (Emf) or PHA to study IL-10, IFN-, and IL-4 production in the supernatant. Emf-stimulated mononuclear cells from the central part of the lesions secreted more IL-10 and less IFN-gamma than cells from the periphery of the granuloma. At the basal level, IL-10 secretion by the locally infiltrating cells was also high and this confirms at the local granuloma level our previous results obtained from cultures of circulating mononuclear cells. The present study confirms that IL-10 secretion is a key feature of the immune response against E. multilocularis in humans. The location of the cells which produce the highest amount of IL-10, those in contact with parasitic structures, suggests that the parasite itself is able to modulate the immune response of the host so that the infiltrating cells cannot participate in the effector phase of the cellular immune response. The nature of the parasitic structures involved and the mechanisms which lead to an imbalanced cytokine production remain to be elucidated.

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.

Concepts in immunology and diagnosis of hydatid disease

Echinococcosis is a cosmopolitan zoonosis caused by adult or larval stages of cestodes belonging to the genus Echinococcus (family Taeniidae). The two major species of medical and public health importance are Echinococcus granulosus and E. multilocularis, which cause cystic echinococcosis (CE) and alveolar echinococcosis (AE), respectively. Both CE and AE are both serious diseases, the latter especially so, with a high fatality rate and poor prognosis if managed inappropriately. This review discusses new concepts and approaches in the immunology and diagnosis of CE, but comparative reference has also been made to AE infection and to earlier pivotal studies of both diseases. The review considers immunity to infection in the intermediate and definitive hosts, innate resistance, evasion of the immune system, and vaccination of intermediate and definitive hosts, and it particularly emphasizes procedures for diagnosis of CE and AE, including the value of immunodiagnostic approaches. There is also discussion of the new advances in recombinant and related DNA technologies, especially application of PCR, that are providing powerful tools in the fields of vaccinology and molecular diagnosis of echinococcosis.

Resistance/susceptibility to Echinococcus multilocularis infection and cytokine profile in humans. II. Influence of the HLA B8, DR3, DQ2 haplotype

Differences have been shown between HLA characteristics of patients with different courses of alveolar echinococcosis (AE). Notably the HLA B8, DR3, DQ2 haplotype was associated with more severe forms of this granulomatous parasitic disease. We compared IL-10, IL-5, interferon-gamma (IFN-gamma) and tumour necrosis factor (TNF) secretion by peripheral blood mononuclear cells (PBMC) isolated from eight HLA-DR3+, DQ2+, B8+ AE patients and from 10 HLA-DR3-, DQ2-, B8- patients after non-specific mitogenic and specific Echinococcus multilocularis antigenic in vitro stimulation. PBMC from seven HLA-DR3+, DQ2+, B8+ healthy subjects and nine HLA-DR3-, DQ2-, B8- subjects were also studied as controls. PBMC from AE patients with HLA DR3+, DQ2+ haplotype secreted higher levels of IL-10 without any stimulation and after specific antigenic stimulation than did patients without this haplotype. Higher levels of IL-5 and IFN-gamma were also produced by these patients' PBMC after stimulation with non-purified parasitic antigenic preparations; however, the specific alkaline phosphatase antigen extracted from E. multilocularis induced only Th2-type cytokine secretion. A spontaneous secretion of TNF by HLA DR3+, DQ2+ B8+ AE patients was also found. These results suggest that HLA characteristics of the host can influence immune-mediated mechanisms, and thus the course of AE in humans; specific antigenic components of E. multilocularis could contribute to the preferential Th2-type cytokine production favoured by the genetic background of the host.

Secondary alveolar echinococcosis in lymphotoxin-alpha and tumour necrosis factor-alpha deficient mice: exacerbation of Echinococcus multilocularis larval growth is associated with cellular changes in the periparasitic granuloma

The availability of mice carrying a deletion of LT-alpha and tumour necrosis factor (TNF)-alpha genes enabled us to investigate the role of the TNF during alveolar echinococcosis. We compared the growth rate of Echinococcus multilocularis in LT-alphaTNF-alpha +/+ mice to that of mice having either no or only one LT-alphaTNF-alpha functionnal allele. LT-alphaTNF-alpha -/- mice harboured a significantly higher parasite burden than did the other two populations at 5, 10, and 15 weeks of infection, and they did not survive thereafter. Liver metacestodes removed from these mice were alive and the dehydrogenase activities of peritoneal metacestodes were decreased. Liver lesions regressed in most wild-type mice. Indeed, dead parasites were cordoned by granulomas containing numerous macrophages and lymphocytes leading to focal liver fibrosis at an early stage of infection. In contrast, most of LT-alphaTNF-alpha -/- mice harboured metacestodes interspersed with leucocytes, realising purulent abscesses with secondary extensive irregular fibrosis at a late stage of infection. Heterozygous mice had behavioural characteristics intermediate between homozygous mutants and wild-type mice. Levels of E. multilocularis-specific delayed-type hypersensitivity and serum antibodies were slightly decreased in LT-alphaTNF-alpha -/- mice. This study shows that TNF-alpha and/or LT-alpha genes play an essential role in the immune protection mechanisms against E. multilocularis at the site of infection.