Cell mediated immunity to liver fluke antigens during experimental Fasciola hepatica infection of cattle

Summary Cell mediated immunity (CMI) to Fasciola hepatica antigens was detected by lymphocyte proliferation and interleukin-2 (IL-2) production tests in cattle during the first 4 weeks following liver fluke infection. From the fifth week of infection onwards peripheral blood lymphocytes were unresponsive to fluke antigens by these in vitro tests. Investigations into the cause of this unresponsiveness found no evidence to suggest a selective loss of the IL-2 producing lymphocyte sub-population or that macrophages were responsible for the suppression or that antigen responsive cells were being sequestered in the spleen and mesenteric lymph nodes. Tests carried out on culture supernatants demonstrated the production during this unresponsive period of factors capable of suppressing in vitro responses to PHA. Although further tests failed to show antigen specific suppressor factors the presence of MHC restricted suppressor factors could not be ruled out. The early and transient appearance of CMI during F. hepatica infection of cattle indicates that delayed type hypersensitivity is unlikely to be important in protective immunity in cattle.     

Fasciola hepatica infection downregulates Th1 responses in mice

Immune responses induced with helminth parasites have been extensively studied, but there is limited information on those to Fasciola hepatica, especially on the subtype of T cell induced with this parasite. We investigated the local and systemic T cell responses of different strains of mice following oral infection with doses of metacercariae from F. hepatica. Spleen cells from BALB/c and 129Sv/Ev mice given a low-dose (5 metacercariae) infection exhibited a Th2 response, producing high levels of the cytokines IL-4 and IL-5, and low levels of IFN-gamma and IL-2. In contrast, C57BL/6 mice showed a mixed Th1/Th2 response. A more marked polarization to a Th2 response was observed in BALB/c, 129Sv/Ev exposed to a high-dose (15 metacercariae) infection and the C57BL/6 mice also exhibited a clear Th2 response. IL-4 defective (IL-4-/-) C57BL/6 mice infected with 5 metacercariae produced less IFN-gamma and more IL-5 compared to their wild-type C57BL/6 counterparts, suggesting that IL-4 is important in establishing the Th2 type response in murine fasciolosis. However, the secretion of IFN-gamma and IL-2 was completely suppressed in the high-dose infection and this was also observed in IL-4-/- mice. Thus, liver flukes may secrete molecules that downregulate Th1 responses. T cell responses in the mesenteric (MLN) and hepatic lymph nodes (HLN) were also examined since newly excysted juveniles infect through the intestinal wall of their host before migrating to the hepatic tissue. Cells from both MLN and HLN secreted higher levels of IL-4 and IL-5 compared to spleen cells. We also observed a difference in cytokine profiles secreted by the MLN and HLN, which may reflect responses to antigens liberated by newly excysted juveniles and hepatic stage parasites, respectively.     

T cell subset involvement in immune responses to Fasciola hepatica infection in cattle

The lymphocyte response to F. hepatica during a primary infection in cattle was analysed to define the role of T cell subsets in the immune response. Blood lymphocytes were isolated from eight cattle infected with F. hepatica via trickle infection over a ten-day period and from two non-infected controls. CD4+, CD8+ and gamma delta + T cells were depleted from whole lymphocyte populations by magnetic bead depletion. Lymphocytes from infected animals demonstrated a transient, but marked elevation in responsiveness to F. hepatica antigen between weeks 3 and 8 post-infection. Responses were attenuated by depletion of CD4+ and CD8+ T cells during this period. Depletion of gamma delta + T cells attenuated antigen responses at one time point only, and at an earlier stage post-infection than when alpha beta + T cells were depleted. Responses to antigen correlated positively with both hepatic fluke burden and with the degree of hepatic damage. This suggests that the cellular immune response was not protective. Antigen responses in gamma delta + T cell-depleted populations were also associated with post-mortem fluke burden and with hepatic damage. This suggests that gamma delta + T cells are involved in down regulating alpha beta + lymphocytes which may have a role in a non-protective or immunopathological immune responses.     

Does Fasciola hepatica infection modify the response of acute hepatitis C virus infection to IFN-α treatment?

Immunologic response to acute hepatitis C is mainly a Th1 response, whereas fasciolopsiasis is associated with a diverse T-cell response. Interferon-alpha has immunomodulatory effects and enhances Th1 immune response. Fasciola infection could theoretically interfere with the Th1 immune response, even when acquired after an initial response to interferon-alpha treatment for acute hepatitis C virus (HCV) infection. We report here the case of a male patient who acquired Fasciola hepatica infection after an initial response to IFN-alpha therapy with a favorable outcome     

肝片形吸虫感染宿主细胞免疫的研究进展

肝片形吸虫病是一种危害严重的人兽共患病,肝片形吸虫主要感染反刍动物及包括人类在内的哺乳动物,是一个严重威胁健康、影响经济发展的公共卫生问题。目前治疗肝片形吸虫病的药物少、疗效有限。大量研究表明,肝片形吸虫受宿主免疫应答的调控,本文对肝片形吸虫病的发病机制、肝片形吸虫主要参与诱导的几种机体细胞免疫反应及相关的研究进展进行综述.以期为肝片形吸虫病的临床治疗提供资料。     

Fasciola hepatica in the rat: immune responses associated with the development of resistance to infection

F. hepatica infections were established in rats and immune responses were monitored during primary and challenge infections. Antibody levels peaked at 3 weeks post-primary infection and at 6 days post-challenge infection. No significant correlation was found between antibody titre and number of flukes recovered at autopsy. Immunoblotting revealed a limited number of immunogenic polypeptides. When antibodies from these reactive bands were eluted and tested by IFA they all gave identical binding patterns: on juvenile fluke sections tegumental syncytium, tegumental cells and gut cells were labelled, while on adult sections the same antibodies labelled gut cells, reproductive tissue, excretory ducts and flame cells. This suggested that these tissues shared a common epitope or range of epitopes. A pronounced eosinophilia was observed throughout the infection period studied and infected liver sections showed massive cellular infiltration. Histochemical and immunocytochemical investigation of infected liver revealed the presence of large numbers of eosinophils, neutrophils, lymphocytes and phagocytes. The implications of these findings, to an understanding of concomitant immunity in the rat are discussed.     

Killing of newly excysted juveniles of Fasciola hepatica in sensitized rats

Newly excysted juvenile Fasciola hepatica were injected intraperitoneally into previously sensitized rats. They were recovered at various intervals post-injection and examined by light and electron microscopy. The challenge flukes were rapidly coated with peritoneal cells which, in the early stages, were mainly eosinophils. The eosinophils adhered closely to the flukes and degranulated on to their surface releasing cytochemically detectable peroxidase. Vacuoles formed in the tegument of the flukes beneath the adherent eosinophils and these increased in size until they spanned the width of the tegument, thus destroying its continuity. From 4 h post-injection some of the flukes had lost their teguments and were surrounded by phagocytic cells, particularly neutrophils; at this stage they were judged to be dead. During the first five minutes post-injection degranulating mast cells were associated with the challenge flukes. Their role in eosinophil chemotaxis is discussed as are the possible mechanisms of eosinophil adherence and degranulation. Using an anti-C₃ fluorescein conjugate, it was demonstrated that C₃ was not bound to the surface of challenge flukes either in vitro or in vitro in immune serum.     

Clinical presentation and management of Fasciola hepatica infection: single-center experience

AIM:To identify the characteristic clinical,laboratory and radiological findings and response to treatment in patients with fascioliasis.METHODS:Patients who were diagnosed with Fasciola hepatica infection were included in this prospective study.Initial clinical,laboratory and radiological findings were recorded.All patients were followed until a complete response was achieved or for 6 mo after treatment discontinuation.RESULTS:Fasciola hepatica infection was diagnosed in 30 patients(24 females;mean age:42....     

Fasciola hepatica: rapid switching of stage-specific antigen expression after infection

Early developmental stages of the trematode parasite Fasciola hepatica were collected from the peritoneal cavity and liver of mice during a ten day infection period. Using one dimensional SDS-PAGE, differences in protein expression profiles were observed in stages collected on the same day post-infection in different physiological locations and also in juvenile parasites collected from the same location on different days post-infection. Four rat monoclonal antibodies were raised against the parasite using lymph nodes draining infected tissues. Three monoclonal antibodies, FY3-1, FY3-2 and FY4-7, were generated using cells from the mesenteric lymph node of recently challenged immune rats, while FY1-6 was derived from hepatic lymph node cells of a chronically infected rat. The epitope recognized by FY3-2 appeared to be carbohydrate in nature and was present on the surface of newly excysted juveniles. Immunoblots revealed that the antigens recognized by FY3-1, FY3-2 and FY4-7 were only expressed for two days after infection. In contrast, FY1-6 recognized epitopes expressed across all developmental stages screened. The rapid changes in protein and antigen expression observed during the early stages of infection may assist the parasite to evade the host immune response.     

The serum antibody response of infected rats, rabbits, lambs and calves to Fasciola hepatica adult antigen fractions separated by preparative flatbed iso-electrofocussing

Electrofocusing of F. hepatica adult antigen in granulated gels separated the material into 22 arbitrary fractions. Polyacrylamide gel analysis demonstrated groups of proteins with similar iso-electric points in 19 of the fractions. A microplate ELISA detected antigens in all 22 fractions and was used to test the serum antibody response in infected rats, rabbits, lambs and calves to these antigen fractions. The results indicated that rat and calf sera gave a much stronger response than rabbit and lamb sera to the antigens which separated above pH 7.0. It is possible that the greater efficiency of the rat and bovine immune systems in combating re-infection with F. hepatica may be related to this response.     

A study of the antigens produced by adult Fasciola hepatica maintained in vitro

Summary Metabolic antigen of adult Fasciola hepatica was prepared by concentrating the culture medium in which 100 adult flukes had been maintained in vitro for 7 days. Serological reactions between this antigen and sera from fluke-infected rabbits, rats and sheep were studied using immunodiffusion in agar and enzyme linked immunosorbent assay. The used medium contained a number of antigenic components and their various reactions with the sera from these different hosts were investigated.     

Fasciola hepatica: changes in tegument during killing of adult flukes surgically transferred to sensitized rats

Summary Adult Fasciola hepatica were placed intraperitoneally into rats which had been sensitized by an oral infection of 20 metacercariae given 3–5 weeks previously. Implanted flukes were recovered at intervals during the next 24 h. Wax embedded sections of flukes and surface impressions of attached cells were examined by light microscopy (LM). Flukes were also examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In all stages, post transplantation, increased secretory activity was noted at the tegu-mental surface both by the blebbing of membrane and the formation of microvilli. Monitoring of the surface by SEM revealed attachment of very few cells (less than 100/sq mm) in the first hour. By TEM some of these were found to be eosinophils. At 1.5 h local palisading of cells, mainly eosinophils, occurred. Many of these degranulated at a distance from the parasite. Between 2 and 4 h many more neutrophils and macrophages were found, with fewer eosinophils. In the period up to 4 h the tegumental syncytium became charged with abnormally high concentrations of secretory granules and the surface membrane was maintained often enclosing apparently damaged areas. No cells penetrated the syncytium at this stage. Between 4 and 12 h the number of secretory granules in the tegument declined. Around 12 h the remaining granules contributed to the formation of large irregular microvilli. It was at this stage that neutrophils, macrophages and occasional eosinophils moved into the syncytium and began to lift it from beneath.     

Neutralization of the activity of a Fasciola hepatica cathepsin L proteinase by anti-cathepsin L antibodies

Fasciola hepatica secretes a cathepsin L proteinase that is suggested to play an in vivo role in immunoprotection since the enzyme can cleave host immunoglobulin. In the present report, rabbit anti-cathepsin L IgG was shown to bind to the cathepsin L enzyme and inhibit its ability to cleave IgG molecules. Cathepsin L can prevent the antibody-mediated attachment of eosinophils to newly excysted juveniles in in vitro assays; however, if anti-cathepsin L IgG are mixed with the cathepsin L prior to the addition of the enzyme to the assay, eosinophils attach to the newly excysted juveniles. Thus it is possible to prepare antibodies that can bind and disrupt the biological activity of the F. hepatica cathepsin L.     

肝片吸虫谷胱甘肽S-转移酶基因的克隆表达及活性分析

目的克隆和表达肝片吸虫谷胱甘肽S-转移酶基因(FhGST)以研究重组蛋白免疫学特性。方法参考Gen-Bank上发表的FhGST基因序列设计一对特异性引物,利用RT-PCR法扩增FhGST基因,将扩增产物克隆入pET-30a(+),构建重组表达载体。经PCR、双酶切和序列测定鉴定后转入E.coliBL21(DE3)宿主菌,经IPTG诱导表达,SDS-PAGE和Western blotting对该重组蛋白进行分析和鉴定。结果成功获得肝片吸虫GST基因全长为657bp的编码序列,SDS-PAGE结果表明重组蛋白分子量为31.3kDa,以包涵体形式表达。Western blotting结果证实重组蛋白能被其免疫的SD大鼠血清识别,表明其具有免疫原性;并且能与感染肝片吸虫的绒山羊血清发生反应,表明重组蛋白具有免疫反应性。结论成功的克隆了肝片吸虫谷胱甘肽S-转移酶基因,实现了在原核表达系统中高效表达重组蛋白,并具有良好的免疫学活性。     

Protection to Fasciola hepatica in the gut mucosa of immune rats is associated with infiltrates of eosinophils,IgG1 and IgG2a antibodies around the parasites

We investigated the immune effector mechanisms that underlie protection against F. hepatica in the gut wall of immune rats, using (immuno)histochemistry. In the lamina propria of immune Wistar rats, four weeks after oral infection, frequencies of IgE-positive cells, eosinophils and mucosal mast cells were significantly increased, compared with naïve rats. These factors represent the traditional effector mechanisms against helminths. No significant differences were detected between the two groups in frequencies of IgM-, IgG2a-, IgG1- and IgA- positive cells, CD4- and CD8-positive cells, NK cells, macrophages, neutrophils or goblet cells. Upon challenge of immune rats with F. hepatica in an ex vivo gut segment, NEJs that migrated through the (sub)mucosa were coated with IgG1 and IgG2a antibodies and surrounded by eosinophils. No IgE or IgA antibodies were detected on the parasites. The onset of these immune effector responses, two h after challenge, was related to the expression of protection. These results suggest that NEJs are killed by an eosinophil-mediated cytotoxic response involving IgG antibodies. These antibodies were not produced in the intestine, but infiltrated the gut upon challenge. The observed immune effector responses were not restricted to the site where the primary infection is located, namely the small intestine, but were also detected in the large intestine. The presence of the protective immune mechanisms in two other rat strains demonstrates the pivotal importance of these responses, irrespective the genetic background of the host.     

The immune response of various species to Fasciola hepatica infection

The trematode F. hepatica is an internal parasite of many species of animals including men. In ruminants, fasciolosis is an economically important disease often resulting in a chronic and sub-clinical infection. The mechanisms of immune responses of final hosts to this infection are still poorly understood. Experimental and clinical studies reported so far suggest that both humoral and cellular effectors of the immune response are important to control the duration of F. hepatica infection. However, there are considerable variation both inter-species and between various strains of the same species in regulation of the response as well as abilities to develop resistance to subsequent infections.     

Cellular responses during liver fluke infection in sheep and its evasion by the parasite

The cellular immune response in sheep to an acute and chronic primary and an acute secondary liver fluke infection were examined by immunohistology of liver tissue and flowcytometry of lymphocytes from the draining hepatic lymph nodes. Ten days after primary infection, portal tract areas surrounding migratory tunnels were infiltrated with CD4⁺ and CD8⁺ lymphocytes with fewer B cells and T19⁺ T cells. Micro abscesses were distributed sporadically in the liver parenchyma and young flukes could be easily observed in the liver tissue free from inflammatory cells. More intensive infiltration of the portal tract areas was observed during a secondary liver fluke infection characterized by a pronounced increase in eosinophils, B cells and CD4⁺ T cells. In addition, there was an increase in MHC class II⁺ fibroblastic-like cells surrounding the migratory tracts. In contrast to the primary infection, no young flukes were observed in the same tissue areas during the secondary infection. Chronic primary infections were characterized by perilobular fibrosis and a predominance of CD8⁺ and γδ-TCR⁺ T19^- T cells distributed within fibrotic strands. Distinct B cell follicles were observed in the fibrotic strands and near major bile ducts and necrotic patches. Pronounced lymphocyte infiltration could occasionally be observed surrounding liver fluke eggs lodged in liver tissue. A progressive increase in lymph node weight, cell number and CD4/CD8 ratio was observed in the acute and chronic primary infections. The role of the infiltrating cell populations and possible mechanisms of immune evasion by the parasite are discussed.     

Humoral responses in mice following vaccination with DNA encoding glutathione S-transferase of Fasciola hepatica: effects of mode of vaccination and the cellular compartment of antigen expression

The humoral responses in mice following vaccination with DNA constructs encoding Fasciola hepatica glutathione S-transferase (GST) have been evaluated. GST47 cDNA was subcloned into two DNA vaccine vectors, VR1012 and VR1020, which direct expression to the cytoplasmic and extracellular compartments, respectively. Expression was confirmed by transfection into COS 7 cells. Groups of mice were vaccinated with these constructs, by either intramuscular injection with the VR1012-or VR1020-based constructs, or intradermal vaccination (with a gene gun) with the VR1020-based construct. Vaccination with the construct designed for secretion resulted in an increased humoral response compared to vaccination with the nonsecretory construct. The level of the total humoral response after vaccination with the secretion construct was not dependent on the route of vaccination. However, the isotype profile of the response differed between the groups; intramuscular vaccination with the construct directing cytoplasmic expression yielded an immuoglobulin (Ig)G2a dominant (Th1-type) response, intradermal vaccination with the secretory construct a IgG1/IgE dominant (Th2-type) response, and intramuscular vaccination with the secretory construct a mixed isotype response. These results demonstrate that the immunogenicity of a DNA vaccine based on Fasciola GST, as well as the isotype of the response against GST, is determined by the mode of vaccine administration.     

Peripheral immune responses in pregnant cattle following Neospora caninum infection

Experimental infection of cattle with Neospora caninum in early gestation causes foetal death, but the foetus survives infection in late gestation. An immunological mechanism of abortion has been suggested; therefore changes in the maternal immune response during pregnancy could account for these differences. We have investigated the peripheral immune responses of pregnant cattle following an intravenous inoculation with 10(7) N. caninum tachyzoites in early and late gestation. Percentages of CD2+ and CD4+ T-cells in peripheral blood mononuclear cells (PBMC) increased 1-2 weeks after infection in both early (day 70) and late (day 210) gestation, and percentages of CD8+ T-cells increased 1-2 weeks after infection at day 70. Interleukin-4 (IL-4) and interferon-gamma (IFN-gamma) mRNA expression in PBMC increased 1-2 weeks after infection at day 210 and IL-4 increased 1-2 weeks after infection at day 70. Immunomagnetic isolation of CD4+ cells from PBMC showed that they were a major source of IL-4 and IFN-gamma, and expression of both cytokines increased in CD4+ cells after infection in early and late gestation. These results suggest that CD4+ cells proliferate and express IL-4 and IFN-gamma in response to N. caninum irrespective of the stage of gestation when infection occurs.     

Clinical significance of the number of retrieved lymph nodes in early gastric cancer with submucosal invasion

The prognosis of early gastric cancer (EGC) with submucosal invasion is favorable; however, several cases of recurrence have been reported even after curative gastrectomy. This study aimed to investigate risk factors and evaluate the clinical significance of the number of retrieved lymph nodes (LNs) in EGC with submucosal invasion. We retrospectively analyzed the data of 443 patients with gastric cancer with submucosal invasion after curative gastrectomy for recurrent risk factors. Recurrence was observed in 22 of the 443 gastric cancer patients with submucosal invasion. In the univariate analysis, the risk factors for recurrence were the number of retrieved LNs ≤ 25 and node metastasis. In the multivariate analysis, retrieved LNs ≤ 25 (hazard ratio [HR] = 5.754, P-value = .001) and node metastasis (HR = 3.031, P-value = .029) were independent risk factors for recurrence after curative gastrectomy. Body mass index was related to retrieved LNs ≤ 25 in univariate and multivariate analyses (HR = .510, P = .002). The number of retrieved LNs and node metastases were independent risk factors for EGC with submucosal invasion. For EGC with submucosal invasion, retrieved LNs > 25 are necessary for appropriate diagnosis and treatment.