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PubMed1999

Antibody and Th1/Th2-type responses in BALB/c mice inoculated with live or dead Echinococcus granulosus protoscoleces.

The aims of this study were to investigate whether a Th1- or a Th2-type response is stimulated in the first stages of experimental infection with Echinococcus granulosus, and to determine whether live or dead protoscoleces equally contribute to such Th1/Th2-type polarization. Live parasites stimulated the production of IL-10, IL-4 and IL-5 as early as week 1 postinoculation. The levels of IL-10 and IL-4 decreased towards week 4 p.i. and that of IFN gamma increased. The production of specific antibodies was characterized by high levels of systemic IgG1 and local IgM and IgG3 (measured in peritoneal lavages). In contrast, dead parasites induced elevated levels of IL-4, IFN gamma, IL-10 and IL-5 on week 1 postinoculation followed by a decrease of IFN gamma and an increase of IL-4. Low levels of specific antibodies were stimulated by dead parasites both systemically and in the peritoneal cavity. These results show that E. granulosus infection induced an early Th2-type response and that live parasites stimulated stronger antibody responses than dead parasites. In addition, they strongly suggest that both phenomena were modulated by live protoscoleces.

Animals↗
PubMed1999

Antibody response in CD4-depleted mice after immunization or during early infection with Echinococcus granulosus.

The aims of this work were to investigate the existence of T-independent antigens in Echinococcus granulosus protoscoleces and to evaluate the relative contribution of T-independent stimulation to the overall antibody response in early infection. Mice depleted of CD4(+)-cells were immunized with protoscolex somatic antigens (PSA) or infected with E. granulosus protoscoleces (PSC). Results showed that the response of CD4-depleted immunized mice had the expected characteristics of a T-independent stimulation and that such T-independent stimulation was important mainly during primary response. During infection absence of CD4(+)-cells affected mainly the secretion of all IgG subclasses with the exception of IgG3 and IgM. To carry out a preliminary isolation of PSC T-independent antigens we prepared a carbohydrate enriched fraction from protoscolex antigens, using a monoclonal antibody specific for the carbohydrate moiety Gal alpha(1,4)Gal highly expressed in PSC. This fraction was mitogenic for naive mouse splenocytes and was recognized by a high percentage of the specific antibodies secreted by CD4-depleted immunized or infected mice. In summary, these results suggest that E. granulosus protoscoleces contain immunogenic T-independent antigens. Primary antibody responses to protoscolex somatic antigens and the production of IgM and IgG3 in early infection would be mainly stimulated by a T-independent mechanism.

Animals↗
PubMed1999

Cytokine and chemokine secretion by human peripheral blood cells in response to viable Echinococcus multilocularis metacestode vesicles.

In human alveolar echinococcosis, asexually proliferating metacestodes of Echinococcus multilocularis progressively infiltrate host tissues and cause serious pathology to the affected organs. This study employed an in vitro culture of E. multilocularis and examined the production of cytokines and chemokines by peripheral blood cells from echinococcosis patients in response to viable proliferating E. multilocularis metacestode vesicles (Em-vesicles). A significant interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) production was elicited in echinococcosis patients when their cells were cocultured with viable Em-vesicles and autologous immune sera. Furthermore, in echinococcosis patients, substantial amounts of cytokines were detected; and the levels of IL-12 and IL-13 found in patients correlated with the actual state of clinical disease. These observations suggest that viable E. multilocularis vesicles will induce significant cellular production of cytokines and chemokines in patients, and that such immune mediators may activate and enhance antibody-dependent cellular effector mechanism against proliferating metacestodes of E. multilocularis.

Adult↗
PubMed1999

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.

Animals↗
PubMed1999

Cloning and expression of a cDNA encoding an elongation factor 1beta/delta protein from Echinococcus granulosus with immunogenic activity.

A cDNA clone (Eg EF-1beta/delta) of Echinococcus granulosus has been isolated by an expression library screened with immunoglobulin (Ig)E of sera from patients with cystic echinococcosis (CE). The Eg EF-1beta/delta was identified on the basis of sequence homology to the subunits beta or delta of the elongation factor-1. The amino acid sequence deduced from this open reading frame is 244 residues long with a predicted molecular mass of 31 kDa. In Southern blot under high stringent condition, Eg EF-1beta/delta hybridized to genomic DNA of E.granulosus at two bands of 4 and 2.5 Kb. In immunoblotting analysis, the Eg EF-1beta/delta protein shows immunological reactivity with sera from CE patients: 51.7% of sera contained IgE, 41.7% IgG and 18.3% IgG4 specific to the recombinant protein. We identify the Eg EF-1beta/delta by immunoblotting with specific monoclonal antibody both in protoscoleces and in sheep hydatid fluid. The higher percentage of humoral immune response against Eg EF-1beta/delta observed in CE patients with calcified cysts than in patients with active cysts indicates the possible release of the protein in the hydatid fluid after protoscoleces degeneration suggesting the possible use of this antigen in the immunosurveillance of CE. Overall, these findings seem to assign to Eg EF-1beta/delta a key role in the allergic disorders and in the complex host-parasite relationship in CE.

Allergens↗
PubMed2000

Contribution of C5-mediated mechanisms to host defence against Echinococcus granulosus hydatid infection.

The aim of this work was to investigate the contribution of complement C5-mediated mechanisms, with an emphasis on inflammation, to host defences against Echinococcus granulosus hydatid disease. Thus, we compared the systemic and local inflammatory responses induced by the parasite, and the outcome of infection, between congenic C5-sufficient (B10.D2 n/SnJ) and C5-deficient (B10.D2 o/SnJ) mice challenged with protoscoleces. Indirect evidence of in-vivo complement activation during the establishment phase was obtained; infection induced serum amyloid P and eosinophil responses which were dependent on C5. Early recruitment of polymorphonuclear cells was not dependent on the presence of C5. The higher capacity of C5-sufficient mice to recruit eosinophils was also observed during the cystic phase of infection, and mice recruiting more eosinophils developed lower parasite masses. Analysis of the outcome of infection after 8 months showed that C5-sufficient mice were more resistant to infection than C5-deficient mice in terms of individuals with no cysts; this trend was not statistically significant. In addition, C5-deficient mice developed higher numbers of large (> 5 mm in diameter) cysts and higher cyst weights than C5-sufficient mice indicating that C5-mediated mechanisms are detrimental for parasite growth. Taken together, our results suggest that complement, through C5-mediated effectors, contributes to host defences by both restricting the establishment of infection and controlling the growth of established cysts. This contribution may, at least partially, be associated with the ability of C5a to promote eosinophil infiltration.

Animals↗
PubMed2000

Echinococcus granulosus: assays for hydatid immunoregulatory factors using established lymphoid cell lines.

Mitosis, mitochondrial metabolic rate and proliferation were measured in established lymphoid cell lines exposed to chromatographic fractions of equine Echinococcus granulosus hydatid fluid. In several cell lines, one or more of the three parameters were modified by the exposure. As an assay for potential immunoregulatory activity, the method was simple and repeatable. The following novel observations were made: (1) Mitotic reaction was found among lines of T-cell, B-cell and macrophage origin; (2) mitosis was accompanied by proliferation in the B-cell lines, B9 and A20, and in the macrophage lines, HL-60 and P388d. With mitotically responsive T-cells, proliferation was slight in CTLL-2 and absent in D10, implying cell-cycle modification; (3) mitotic responsiveness tended to occur in cell lines with mature characteristics; (4) among cytokine-dependent cell lines, hydatid fluid FPLC fraction 1 mimicked IL-1 and several fractions mimicked IL-2 and IL-6 in the maintenance of mitosis; and (5) there was significant statistical interaction between the influences of mammalian cytokines and hydatid fluid fractions, implying that the propensity of antigenically unprimed lymphoid cells to be regulated by E. granulosus is conditioned by cytokine activity.

Adjuvants, Immunologic↗
PubMed2001

Modulation of the cellular immune response by a carbohydrate rich fraction from Echinococcus granulosus protoscoleces in infected or immunized Balb/c mice.

Infection of Balb/c mice with Echinococcus granulosus protoscoleces constitutes the model for secondary hydatid infection. The immune response of Balb/c mice infected with E. granulosus is characterized by secretion of antibodies specific for carbohydrate epitopes and production of type-2 cytokines. A role for glycoconjugates in the induction of type-2 responses has been suggested in other host--parasite systems. Although glycoconjugates are immunogenic in E. granulosus infection, the role of these molecules in the establishment of the type-2 response has never been analysed. In this study, a carbohydrate rich fraction (E4+) from E. granulosus protoscoleces was obtained using the monoclonal antibody E492/G1 specific for the moiety Galalpha(1,4)Gal which is widely represented in protoscoleces and other E. granulosus antigenic preparations. The results showed that E4+ was immunogenic in Balb/c mice evoking an antibody response mainly directed against carbohydrate epitopes. In addition, splenocytes from E4+-immunized mice showed suppressed proliferative responses to Con A and E4+ induced IL-10 secretion by E4+-primed and naive splenocytes. The fraction E4+ also was immunogenic in infected mice during early infection. In this case also, splenocytes from infected mice as well as peritoneal cells from infected or naive mice, when stimulated in vitro with E4+, secreted IL-10. Collectively, these results suggest that E4+ may be involved in immunosuppression phenomena and, by stimulating IL-10 secretion, may contribute to the induction and sustaining of the type-2 cytokine response established in early experimental infection.

Animals↗
PubMed2001

In-vitro susceptibility of hydatid cysts of Echinococcus granulosus to nitric oxide and the effect of the laminated layer on nitric oxide production.

Murine hydatid cysts of Echinococcus granulosus were incubated in vitro in the presence of nitric oxide produced from S-nitroso-N-acetylpenicillamine (SNAP) or interferon-gamma activated peritoneal macrophages. In both situations, evidence of cyst damage and death was observed by microscopy in over 77% of cysts after 3 days, indicating that intact hydatid cysts could be susceptible to a Th1 driven macrophage attack. A crude extract of the laminated layer from cysts was found to be able to reduce the production of nitric oxide from activated macrophages in vitro and in vivo and this may have been due to phagocytosis of laminated layer fragments by the macrophages. The results indicate that, although cysts may be susceptible to the effects of nitric oxide, the laminated layer may be involved in downregulating nitric oxide production.

Animals↗
PubMed2001

Assessment of in vivo complement activation on the Echinococcus granulosus hydatid cyst wall.

The larval stage of the parasite Echinococcus granulosus causes hydatid disease. The hydatid cyst is potentially capable of activating host complement, since it is a large, persistent, carbohydrate-rich structure, coated with host immunoglobulins, and localized in the host's internal organs. Nonetheless, in vitro studies have suggested that the cyst surface, the hydatid cyst wall (HCW), is a poor complement activator. In this study, we assessed the occurrence of in vivo complement activation on the hydatid cyst by measuring the levels of two complement activation products, C3d and complexes bearing a C9 activation neoepitope (TCC/MAC), in extracts from HCW of human origin. Low amounts of C3d and TCC/MAC were found in HCW in comparison with their levels in normal human plasma and activated human sera, suggesting that in vivo complement activation on HCW is efficiently down-regulated. This regulation may contribute to limit host inflammation which has been observed to correlate with parasite degeneration and death.

Animals↗
PubMed2003

Pro-inflammatory (IL-1beta, IL-18) cytokines and IL-8 chemokine release by PBMC in response to Echinococcus multilocularis metacestode vesicles.

In humans infected with Echinococcus multilocularis, larval metacestodes will develop, proliferate and progressively infiltrate the surrounding host tissues by exogenous budding of parasitic microvesicles or cell lines which detach from the original tumour and thus become transported through blood or lymph vessels into other organs. Cellular effector mechanisms constitute the most effective means to restrict parasite persistence and proliferation, and here we demonstrate that E. multilocularis vesicle antigens will induce pro-inflammatory, regulatory and chemokine release by PBMC from patients. The pro-inflammatory cytokines IL-1beta and IL-18 were reduced in echinococcosis patients, regulatory IL-10 was similar, but parasite vesicle-induced IL-8 was dominant and clearly elevated in patients. Such selective and opposite dynamics of inflammatory cytokines and chemokine release may prevent overwhelming and pathogenic inflammation, and constitute an appropriate response for attraction of effector cells into the periparasitic tissues with the capacity to limit E. multilocularis metacestode proliferation and dissemination.

Animals↗
PubMed2003

Molecular and immunological characterization of the C-terminal region of a new Echinococcus granulosus Heat Shock Protein 70.

By screening an expression library of Echinococcus granulosus with IgE from sera of patients with cystic echinococcosis (CE) and allergic reactions, we isolated the C-terminal region of a new heat shock protein (HSP)70 of E. granulosus. The protein, named Eg2HSP70, has close homology with the C-terminal region of Dermatophagoides farinae and human HSP70. We investigated the humoral and cell-mediated immune responses to this antigen in patients with CE grouped according to the presence of allergic reactions. Immunoblotting detected total IgG, IgG4 and IgE specific to Eg2HSP70 (83% of sera contained IgG, 31% IgG4 and 57% IgE). No significant difference was found in immunoglobulin percentages according to the presence of allergic reactions. Immunoblotting inhibition showed that no IgG or IgE specific to Eg2HSP70 cross-reacted with D. farinae or human HSP70. Eg2HSP70-stimulated PBMC from 26 patients produced significantly greater amounts of TNF-alpha, IFN-gamma, and IL-10 than unstimulated cultures in all patients, irrespective of the presence of allergic reactions (P < 0.05). They also produced significantly greater amounts of IL-4 than unstimulated cultures exclusively in patients with allergic reactions (P < 0.05). These findings show that Eg2HSP70 is a new antigenic molecule inducing both B and T cell responses.

Adult↗
PubMed2003

Cytokine response and outcome of infection depends on the infective dose of parasites in experimental infection by Echinococcus granulosus.

We here analysed whether the cytokine responses in early and late experimental infection with Echinococcus granulosus depend on the dose of parasites to which the host is exposed. To this purpose Balb/c mice were inoculated intraperitoneally (i.p.) with either 500 or 2000 protoscoleces. Splenocytes of mice were obtained at days 3, 7, 14 and 21 and also on week 37 post-infection and cultured in vitro with protoscolex antigens. Type-1 and type-2 cytokines were analysed in supernatants by ELISA. Results showed that the inoculation of 500 protoscoleces induced an early type-0 and a late type-2 cytokine response, whereas the inoculation of 2000 protoscoleces induced an early type-2 and a late type-0 cytokine response. Parasite growth was lower in the group inoculated with the low infective dose. These results indicate that the cytokine response during the infection by the helminth E. granulosus depends on the dose of parasites to which the host has been exposed.

Animals↗
PubMed2003

Immunoglobulin profiles in a murine intermediate host model of resistance for Echinococcus granulosus infection.

We have shown previously that primary infection of Chinese Kunming (CKM) mice with Echinococcus granulosus oncospheres is protective against subsequent challenge. Nine groups of mice were infected with the oncospheres of E. granulosus by different routes (intraperitoneal, subcutaneous or intravenous injection). After infection, serum was collected after different periods of time and serum antibodies were tested by ELISA against oncospheral proteins and hydatid cyst fluid antigens. The results indicated that CKM mice produced low levels of antibodies before a secondary challenge infection given 3 weeks later by a different route. Most mice did not evoke significant antibody responses against oncospheral antigens until 5 weeks after infection. The level of IgG, especially IgG1 against oncospheral antigens increased from week 4 post-infection (p.i.), to a maximum at week 9 p.i. In addition, antibodies against hydatid cyst fluid antigens increased at the same time as the recognition of oncospheral antigens. Immunoblots using hydatid cyst fluid showed that the first antigen that was recognized - an 8-kDa protein, possibly the smallest subunit of Antigen B - appeared 5-6 weeks p.i. and reactivity to this molecule was intensive at week 9 p.i. The results suggest that protection against secondary infection was not principally antibody-mediated during the initial phases of infection, when cellular immune responses may play a pivotal role in the protective mechanism.

Animals↗
PubMed1990

The ecology of Echinococcus multilocularis (Cestoda: Taeniidae) on St. Lawrence Island, Alaska. II. Helminth populations in the definitive host.

The helminths of 1,579 arctic foxes from St. Lawrence Island were investigated by standard methods. The foxes, obtained mainly during the winter from fur trappers, harbored 22 species of helminths. Four of those were trematodes, viz., Maritrema afanassjewi Belopol'skaia, 1952, Orthosplanchnus pygmaeus Iurakhno, 1967, Plagiorchis elegans (Rudolphi, 1802) and Alaria marcianae (LaRue, 1917), each of which occurred in a single host. Two species of cestodes, Diphyllobothrium dendriticum (Nitzsch, 1824) and Mesocestoides kirbyi Chandler, 1940, were uncommon (in 2.7 and 1.3% of the foxes, respectively). Taenia polyacantha Leuckart, 1856 and Echinococcus multilocularis Leuckart, 1863 were present in about 80% of the foxes, and Taenia crassiceps (Zeder, 1800) in less than 10%. The specimens of Taenia spp. from the autumn-winter sample were usually destrobilate. In about 2% of the foxes, acanthocephalans of six species occurred. Four of those, of the genus Corynosoma Lühe, 1904, were common in marine mammals of the region; a fifth, Corynosoma clavatum Goss, 1940, has been reported previously only from marine birds of the Southern Hemisphere; and the sixth, Polymorphus cf. minutus (Goeze, 1782), has been found widely in waterfowl of the Northern Hemisphere. Of the nematodes, Sobolophyme baturini Petrov, 1930, Cylicospirura felineus (Chandler, 1925), and Physaloptera sp. were rare (with each in only one to three foxes). Trichinella nativa Boev et Britov, 1972 and Crenosoma vulpis (Dujardin, 1844) were uncommon (1.5 and 4%, respectively). The nematodes most often present were Toxascaris leonina (von Linstow, 1902) (89%) and Uncinaria stenocephala (Railliet, 1884) (40%). Several of the rare to uncommon helminths probably were transported to the island by foxes immigrating from the adjacent continents via the pack ice.

Acanthocephala↗
PubMed1994

Specific cellular and humoral immune responses induced by different antigen preparations of Echinococcus multilocularis metacestodes in patients with alveolar echinococcosis.

A specific proliferation of the peripheral blood mononuclear cells (PBMC) stimulated by antigens of Echinococcus sp. has been shown in patients with cystic as well as alveolar echinococcosis. However, the development of a major granulomatous reaction around the parasitic larvae is a characteristic feature of the local immune response to E. multilocularis while humoral immune responses seem to predominate in E. granulosus infection. The aim of this study was to analyse the specific proliferation of the PBMC from 36 patients with alveolar echinococcosis, and 23 controls, induced by a crude preparation of E. multilocularis (EmcAg) as well as by two E. multilocularis specific antigen preparations, the Em2 antigen and the protoscolex (ESAg) antigen. The significant correlation observed between the proliferation index either by Em2 and ES or by Emc suggests that both antigens account for an important part of the lymphocyte proliferative response. The strong effect of these species specific antigens on lymphocyte proliferation is confirmed by the comparison of the results obtained in this study to those obtained in a previous study of specific cellular immunity to E. granulosus antigens in patients with cystic echinococcosis. The proliferation indices were significantly elevated in all those 7 patients with a proven AE who were sero-negative using the Emc ELISA as well as in the 12 patients also seronegative, but using the Em2 ELISA. In 5 seronegative patients who had had a complete resection of the parasitic lesions two years before the lymphocyte proliferation evaluation, the PI was above the threshold value for two dilutions of EmcAg. PI under the threshold values were obtained only in patients with residual lesions. These results suggest that E. multilocularis specific antigens promote the proliferation of lymphocytes which could be TH1 cells, responsible for the intense periparasitic granulomatous reaction characteristic of alveolar echinococcosis.

Adult↗