Pathological and immunohistochemical study of the liver and hepatic lymph nodes of sheep chronically reinfected with Fasciola hepatica, with or without triclabendazole treatment

Liver Histopathological and Immunohistochemical Evaluation from Fasciola hepatica Experimentally Infected and Reinfected Sheep

Fasciolosis is an important economic disease of livestock. There is a global interest in the development of protective vaccines since the current anthelmintic therapy is no longer sustainable. A better knowledge of the host-parasite interaction is needed to design effective vaccines. To date, few studies have evaluated host-parasite interaction by comparing infected and reinfected animals. The present study evaluates the microscopical hepatic lesions in sheep infected and reinfected with Fasciola hepatica during the acute and chronic stages of infection. The histopathological study revealed the presence of necrotizing foci (NF1) associated with larvae migration during the early stages of infection in the primoinfected (PI) and reinfected (RI) groups. In the late stages of infection of the PI group and at the early and late stages of infection in the RI groups, extensive necrotizing/hemorrhagic foci (NF2) were found in the vicinity of enlarged bile ducts, some containing adult flukes, suggesting parasites may have caused NF2 while feeding. The immunohistochemical study revealed an increase in Foxp3+ T cells in both PI and RI groups with respect to the UC group and in the infiltrates adjacent to NF1 in the RI groups with respect to the PI group, suggesting the F. hepatica induce Foxp3 T cell expansion to facilitate parasite survival. In addition, in both the PI and RI groups, and during acute and chronic stages of the infection, a poor expression of iNOS was found accompanied by a strong expression of CD163, suggesting a marked M2 activation of macrophages in the hepatic lesions, which may be related with healing processes, and it also may facilitate parasite survival. The main differences between PI and RI animals were the more severe infiltration of eosinophils and Foxp3+ T cells, whereas RI did not modify M2 activation of macrophages which occurs since the early stages of primoinfection.

Evaluation of Th1/Th2, regulatory cytokines and transcriptional factor FoxP3 in sheep immunized with a partially protective and non-protective vaccine and challenged with Fasciola hepatica

Gene expression for Th1/Th2 cytokines (IL-4 and IFN-ɣ), regulatory cytokines (TGF-β and IL-10) and the transcriptional factor FoxP3 was analyzed in the liver and hepatic lymph nodes (HLN) from sheep immunized with partially protective and non-protective vaccine candidates and challenged with Fasciola hepatica. FoxP3 T cells were also evaluated by immunohistochemistry (IHQ). The most remarkable difference between the partially protected vaccinated (V1) group and the non-protected vaccinated (V2) group was a more severe expansion of FoxP3 T cells recorded by IHQ in both the liver and HLN of the V2 group as compared to the V1 group, whereas no differences were found between the V2 group and the infected control (IC) group. Similar results were recorded for FoxP3 gene expression although significant differences among V1 and V2 groups were only significant in the HLN, while FoxP3 gene expression was very similar in the V2 and IC groups both in the liver and HLN. No significant differences for the remaining cytokines were recorded between the V1 and V2 groups, but in the liver the V2 group shows significant increases of IFN-ɣ and IL-10 as compared to the uninfected control (UC) group whereas the V1 group did not. The lower expansion of FoxP3 T cells and lower increase of IFN-ɣ and IL-10 in the partially protected vaccinated group may be related with lower hepatic lesions and fluke burdens recorded in this group as compared to the other two infected groups. The most relevant change in regulatory cytokine gene expression was the significant increase of TGF-β in the liver of IC, V1 and V2 groups as compared to the UC group, which could be related to hepatic lesions.

Fasciolosis: pathogenesis, host-parasite interactions, and implication in vaccine development

Fasciola hepatica is distributed worldwide, causing substantial economic losses in the animal husbandry industry. Human fasciolosis is an emerging zoonosis in Andean America, Asia, and Africa. The control of the disease, both in humans and animals, is based on using anthelmintic drugs, which has resulted in increased resistance to the most effective anthelmintics, such as triclabendazole, in many countries. This, together with the concerns about drug residues in food and the environment, has increased the interest in preventive measures such as a vaccine to help control the disease in endemic areas. Despite important efforts over the past two decades and the work carried out with numerous vaccine candidates, none of them has demonstrated consistent and reproducible protection in target species. This is at least in part due to the high immunomodulation capacity of the parasite, making ineffective the host response in susceptible species such as ruminants. It is widely accepted that a deeper knowledge of the host-parasite interactions is needed for a more rational design of vaccine candidates. In recent years, the use of emerging technologies has notably increased the amount of data about these interactions. In the present study, current knowledge of host-parasite interactions and their implication in Fasciola hepatica vaccine development is reviewed.

First molecular evidence of Clostridium perfringens in adult Fasciola spp. isolates in cattle hosts

Fasciolosis is a parasitic disease caused by Fasciola spp. It is a prevalent helminth infection globally. Clostridial hepatitis is a general name refer to disorders caused by a few clostridial agents that most severely affect the liver. Migration of young parasite forms (mostly Fasciola hepatica) in the parenchymal tissue of the liver causes necrosis and anaerobic environment, stimulating the proliferation of C. novyi type B spores. This study investigated the occurrence of Clostridium spp in adult Fasciola spp isolates. Isolates (n = 100) were collected from the bile ducts of infected cattle after slaughter. Total genomic DNA was extracted from each sample. A multiplex-PCR based on the flagellin C (fliC) gene was used for quick identification of C. chauvoei, C. haemolyticum, C. novyi types A and B, and C. septicum. In addition, a pair of primers Cpa (F) and Cpa (R) were used for detection of the C. perfringens alpha toxin gene. The products were sequenced. No band was obtained after multiplex-PCR of the fliC gene. A 247 bp band was detected in two isolates using the Cpa primers. BLAST analysis of these two isolates characterized both as C. perfringens alpha toxin. This is the first description of the molecular detection of C. perfringens in flukes. Further studies are needed to investigate whether Clostridum species is also carried by other developmental forms (egg and larval stages) of Fasciola spp.

A Partially Protective Vaccine for Fasciola hepatica Induced Degeneration of Adult Flukes Associated to a Severe Granulomatous Reaction in Sheep

Simple Summary

Fasciolosis is a parasitic disease of livestock causing important economic losses worldwide and it is also a zoonosis. Current therapy relies on the use of anthelmintic drugs, which is no longer sustainable due to the increase of anthelmintic resistance and the risk of drug residues in food. A deep understanding of the host-parasite interaction is required to develop protective vaccines for the control of fasciolosis. The aim of the present study is to evaluate the hepatic lesions in sheep vaccinated with a partly protective vaccine for F. hepatica, a non-protective vaccine and an infected control group. The protective vaccine showed less severe hepatic lesions than the infected control group. In addition, in the protective vaccine group dead flukes surrounded by a severe granulomatous inflammation were observed, which taken together with the lower fluke burden, suggests that the host response induced by the partially protective vaccine may have been involved in the death of adult flukes of F. hepatica. This is the first study reporting the presence of degenerated flukes associated to a severe granulomatous inflammation in bile ducts in a vaccine trial, a finding that would be useful for improving vaccine efficacy in future trials.

Abstract

Fasciolosis is an important economic disease of livestock. There is a global interest in the development of protective vaccines since current anthelmintic therapy is no longer sustainable. A better knowledge of the host-parasite interaction is needed for the design of effective vaccines. The present study evaluates the microscopical hepatic lesions in sheep immunized with a partially protective vaccine (VAC1), a non-protective vaccine (VAC2), and an infected control group (IC). The nature of granulomatous inflammation associated with degeneration of adult flukes found in the VAC1 group was characterized by immunohistochemistry. Hepatic lesions (fibrous perihepatitis, chronic tracts, bile duct hyperplasia, infiltration of eosinophils and lymphocytes and plasma cells) were significantly less severe in the VAC1 group than in the IC group. Dead adult flukes within bile ducts were observed only in the VAC1 group and were surrounded by a severe granulomatous inflammation composed by macrophages and multinucleate giant cells with a high expression of lysozyme, CD163 and S100 markers, and a low expression of CD68. Numerous CD3+ T lymphocytes and scarce infiltrate of FoxP3+ Treg and CD208+ dendritic cells were present. This is the first report describing degenerated flukes associated to a severe granulomatous inflammation in bile ducts in a F. hepatica vaccine trial.

Transcriptomic Analysis of Ovine Hepatic Lymph Node Following Fasciola hepatica Infection - Inhibition of NK Cell and IgE-Mediated Signaling

Fasciola hepatica is a trematode parasite responsible for major economic losses in livestock production, and is also a food-borne zoonotic agent in developing rural regions. For years, the immunoregulatory mechanisms employed by the parasite have hampered efforts to develop a successful vaccine candidate. Given that a comprehensive understanding of the immune response to infection is needed, we investigated the gene expression changes in ovine hepatic lymph nodes after experimental infection with F. hepatica. Lymph nodes from uninfected and infected animals were processed for RNA sequencing (RNA-seq) at 16 weeks post-infection. Comparison of groups revealed 5,132 differentially-expressed genes (DEGs). An inhibition of pro-inflammatory pathways, which has previously been described during fasciolosis, was evident in our data. However, other signals previously identified in ruminant peripheral blood mononuclear cells (PBMC) or liver tissue, such as activation of TGF-β or apoptosis-related pathways were not detected. We found inhibition of some key immunological pathways, including natural killer (NK) cell activity and IgE-mediated signaling. These may point to additional some as yet unrecognized mechanisms employed by the parasite to evade the host immune response. Understanding these, and leveraging information from this and other omics studies, will be important for the development of future vaccine prototypes against this parasite.

Fasciola hepatica induces weak NETosis and low production of intra- and extracellular ROS in exposed bovine polymorphonuclear neutrophils

Fasciola hepatica is the causative agent of fasciolosis, a worldwide distributed zoonotic disease, leading to hepatitis in humans and livestock. Newly excysted juveniles (NEJ) of F. hepatica are the first invasive stages to encounter leukocytes of host innate immune system in vivo. Among leukocytes, polymorphonuclear neutrophils (PMN) are the most abundant granulocytes of blood system and first ones to migrate into infection sites. PMN are able to cast neutrophil extracellular traps (NETs), also known as NETosis, consisting of nuclear DNA, decorated with histones, enzymes and antimicrobial peptides, which can entrap and eventually kill invasive parasites. Given that only few large parasitic helminths have been identified as potent NETosis inducers, here we studied for first time whether different F. hepatica stages can also trigger NETosis. Therefore, isolated bovine PMN were co-cultured with viable F. hepatica-NEJ, -metacercariae, -eggs and soluble antigen (FhAg). Interestingly, all stages failed to induce considerable levels of NETosis as detected by immunofluorescence- and scanning electron microscopy (SEM) analyses. NEJ remained motile until the end of incubation period. In line, NETosis quantification via nuclear area expansion (NAE) analysis revealed NEJ as weak NETosis inducers. However, bovine PMN frequently displaced towards motile NEJ and were found attached to NEJ surfaces. Functional PMN chemotaxis assays using vital F. hepatica-NEJ revealed a slight increase of PMN migration when compared to non-exposed controls. Additional experiments on intra- and extracellular reactive oxygen species (ROS) production revealed that soluble FhAg failed to induce ROS production of exposed PMN. Finally, mitochondrial oxygen consumption rates (OCR), extracellular acidification rates (ERAC) and proton production rates (PPR) were not significantly increased in FhAg-stimulated PMN. In summary, data suggest that F. hepatica might effectively evade PMN activation and NETosis by secreting parasite-specific molecules to either resolve NETs or to impair NETosis signaling pathways. We call for future molecular analysis not only on F. hepatica-derived NETosis modulation but also on its possible role in fasciolosis-associated pathology in vivo.

Characterization of dendritic cells and follicular dendritic cells in the hepatic lymph nodes and liver of sheep experimentally infected with Fasciola hepatica

Fasciola hepatica has been shown to have a high capacity for immunomodulation of the host response, making the development of protective vaccines extremely difficult. One of these immunomodulation mechanisms is the impairment of dendritic cells (DC) maturation and, therefore, suppression of antigenic presentation. The aim of this study was to evaluate the pathological changes as well as the characterization of two antigen presenting cells, DC (CD1b, CD83 and MHC-II positive) and follicular dendritic cells (FDC) (CNA.42, S100 and CD83 positive) by immunohistochemistry in the hepatic lymph nodes (HLN) and livers of sheep during the early stages of infection with F. hepatica [9 and 18 days post-infection (dpi)], compared with an uninfected group (UC) as a control. The results revealed a marked hyperplasia of HLN germinal centres at 9 and, in particular, 18 dpi, with respect to the UC group, with coincidental increased expression of CNA.42 in FDC of lymphoid follicles and CD1b in the DC of paracortical areas at 18 dpi. However, the expression of MHC-II and CD83 decreased at 9 and, particularly, at 18 dpi in HLN compared with that in the UC group. Since both markers are related to active presentation of antigens by DC and FDC, the results of the present study suggest that, despite the marked hyperplasia of HLN and increase in DC and FDC numbers during early stages of infection, the DC and FDC antigenic presentation capacity, as suggested by the expression of the markers MHC-II and CD83, is suppressed by the parasite. This suppression was not observed in the liver, probably because of the low number of DC. This is the first study of the immunophenotype of DCs and FDC in sheep infected with F. hepatica.

Pathobiology and diagnosis of clostridial hepatitis in animals

Clostridia can cause hepatic damage in domestic livestock, and wild and laboratory animals. Clostridium novyi type B causes infectious necrotic hepatitis (INH) in sheep and less frequently in other species. Spores of C. novyi type B can be present in soil; after ingestion, they reach the liver via portal circulation where they persist in phagocytic cells. Following liver damage, frequently caused by migrating parasites, local anaerobic conditions allow germination of the clostridial spores and production of toxins. C. novyi type B alpha toxin causes necrotizing hepatitis and extensive edema, congestion, and hemorrhage in multiple organs. Clostridium haemolyticum causes bacillary hemoglobinuria (BH) in cattle, sheep, and rarely, horses. Beta toxin is the main virulence factor of C. haemolyticum, causing hepatic necrosis and hemolysis. Clostridium piliforme, the causal agent of Tyzzer disease (TD), is the only gram-negative and obligate intracellular pathogenic clostridia. TD occurs in multiple species, but it is more frequent in foals, lagomorphs, and laboratory animals. The mode of transmission is fecal-oral, with ingestion of spores from a fecal-contaminated environment. In affected animals, C. piliforme proliferates in the intestinal mucosa, resulting in necrosis, and then disseminates to the liver and other organs. Virulence factors for this microorganism have not been identified, to date. Given the peracute or acute nature of clostridial hepatitis in animals, treatment is rarely effective. However, INH and BH can be prevented, and should be controlled by vaccination and control of liver flukes. To date, no vaccine is available to prevent TD.

Fasciola hepatica induces Foxp3 T cell, proinflammatory and regulatory cytokine overexpression in liver from infected sheep during early stages of infection

The expression of T regulatory cells (Foxp3), regulatory (interleukin [IL]-10 and transforming growth factor beta [TGF-β]) and proinflammatory (tumor necrosis factor alpha [TNF-α] and interleukin [IL]-1β) cytokines was quantified using real time polymerase chain reaction (qRT-PCR) in the liver of sheep during early stages of infection with Fasciola hepatica (1, 3, 9, and 18 days post-infection [dpi]). Portal fibrosis was also evaluated by Masson's trichrome stain as well as the number of Foxp3+ cells by immunohistochemistry. Animals were divided into three groups: (a) group 1 was immunized with recombinant cathepsin L1 from F. hepatica (FhCL1) in Montanide adjuvant and infected; (b) group 2 was uniquely infected with F. hepatica; and (c) group 3 was the control group, unimmunized and uninfected. An overexpression of regulatory cytokines of groups 1 and 2 was found in all time points tested in comparison with group 3, particularly at 18 dpi. A significant increase of the number of Foxp3+ lymphocytes in groups 1 and 2 was found at 9 and 18 dpi relative to group 3. A progressive increase in portal fibrosis was found in groups 1 and 2 in comparison with group 3. In this regard, group 1 showed smaller areas of fibrosis than group 2. There was a significant positive correlation between Foxp3 and IL-10 expression (by immunohistochemistry and qRT-PCR) just as between portal fibrosis and TGF-β gene expression. The expression of proinflammatory cytokines increased gradually during the experience. These findings suggest the induction of a regulatory phenotype by the parasite that would allow its survival at early stages of the disease when it is more vulnerable.

Immune signatures of pathogenesis in the peritoneal compartment during early infection of sheep with Fasciola hepatica

Immune signatures of sheep acutely-infected with Fasciola hepatica, an important pathogen of livestock and humans were analysed within the peritoneal compartment to investigate early infection. Within the peritoneum, F. hepatica antibodies coincided with an intense innate and adaptive cellular immune response, with infiltrating leukocytes and a marked eosinophilia (49%). However, while cytokine qPCR analysis revealed IL-10, IL-12, IL-13, IL-23 and TGFβ were elevated, these were not statistically different at 18 days post-infection compared to uninfected animals indicating that the immune response is muted and not yet skewed to a Th2 type response that is associated with chronic disease. Proteomic analysis of the peritoneal fluid identified infection-related proteins, including several structural proteins derived from the liver extracellular matrix, connective tissue and epithelium, and proteins related to the immune system. Periostin and vascular cell adhesion protein 1 (VCAM-1), molecules that mediate leukocyte infiltration and are associated with inflammatory disorders involving marked eosinophilia (e.g. asthma), were particularly elevated in the peritoneum. Immuno-histochemical studies indicated that the source of periostin and VCAM-1 was the inflamed sheep liver tissue. This study has revealed previously unknown aspects of the immunology and pathogenesis associated with acute fascioliasis in the peritoneum and liver.

Immunohistochemical study and mRNA cytokine profile of the local immune response in cattle naturally infected with Calicophoron daubneyi

In order to recognize the local immune response of the definitive host to Calicophoron daubneyi natural infection, an immunohistochemical study was carried out in the reticulum and rumen in 49 naturally infected cattle. The role of cytokines (IL-4 and IL-10 interleukins and IFN-γ) in the activation of specific defence mechanisms was evaluated by reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) assays to study cytokine mRNA expression. In all infected animals, CD3+ T lymphocytes seemed to be the main element of the inflammatory infiltrate in the reticular and ruminal lamina propria at the point of the parasite adhesion. Intraepithelial globule leukocytes also showed immunolabelling for CD3. Most CD3+ cells also expressed CD4 (T cell helper) antigen although sporadic CD8+-cytotoxic lymphocytes were observed. Local expression of IFN-γ was observed in damaged papillae at the site of parasite attachment and in scattered cells in the lamina propria. B cells (CD79αcy+, CD45+ and IgG+) were found constantly in relation to lymphoid aggregates. MAC387 was expressed in squamous epithelium and in macrophages of the lamina propria of affected papillae. Macrophages in this location also stained positively for CD163 and CD68. Intraepithelial Langerhans cells and macrophages located in the lamina propria showed immunopositivity for MHCII in the affected areas. RT-qPCR analysis confirmed a statistical significant increase of IFN-γ, and IL-10 expression (p<0.01) in the rumen associated with the presence of flukes. These findings suggest a predominant Th1 polarized local immune response with the probable involvement of Th regulatory cells in cattle C. daubneyi natural infection.

Comparative recruitment, morphology and reproduction of a generalist trematode, Dicrocoelium dendriticum, in three species of host

Epidemiological rate parameters of host generalist parasites are difficult to estimate, especially in cases where variation in parasite performance can be attributed to host species. Such cases are likely common for generalist parasites of sympatric grazing mammals. In this study, we combined data from experimental exposures in cattle and sheep and natural infections in elk to compare the recruitment, morphology and reproduction of adult Dicrocoelium dendriticum, a generalist trematode that has emerged in sympatric grazing hosts in Cypress Hills Provincial Park, Alberta. Overall, there were no significant differences in the recruitment of metacercariae and in the pre-patency period of adults in experimentally exposed cattle and sheep. All flukes reached reproductive maturity and the degree of reproductive inequality between individual flukes within each infrapopulation was moderate and approximately equal among the three host species. Neither fluke size nor per capita fecundity was constrained by density dependence. Thus, fitness parameters associated with growth and reproduction were approximately equivalent among at least three species of definitive host, two of which are sympatric on pastures in this Park. The generalist life-history strategy of this trematode, which is known to extend to other stages of its life cycle, has likely contributed to its invasion history outside its native range in Europe.

Pathological changes in cattle naturally infected by Calicophoron daubneyi adult flukes

Local host response and parasite distribution were studied in the forestomachs, abomasum, duodenum and regional lymph nodes of cattle suffering from bovine paramphistomosis. The parasites were found attached, by its ventral sucker, to small conical papillae of the rumen and reticulum. Affected papillae, showed morphological changes denoted by very narrow stalks and expanded heads. Histologically, these changes were characterized by epithelial acanthosis-hyperkeratosis of the epithelium. Infiltration of inflammatory cells was often related with the epithelial changes, although it was also found in the duodenal mucosa and submucosa. These cells were arranged as aggregates or follicles but sparse infiltration of eosinophils, globule leukocytes, mast cells or macrophages was also observed in the lamina propria. Tissue damage and inflammatory reaction were more severe in the ruminal atrium, where the largest number of flukes and affected papillae were observed. In contrast, lesions in the ruminal dorsal sac were absent or mild. Statistical correlation between lesion severity and parasite burden was confirmed.

Fasciola hepatica vaccine: we may not be there yet but we're on the right road

Major advances have been made in identifying potential vaccine molecules for the control of fasciolosis in livestock but we have yet to reach the level of efficacy required for commercialisation. The pathogenesis of fasciolosis is associated with liver damage that is inflicted by migrating and feeding immature flukes as well as host inflammatory immune responses to parasite-secreted molecules and tissue damage alarm signals. Immune suppression/modulation by the parasites prevents the development of protective immune responses as evidenced by the lack of immunity observed in naturally and experimentally infected animals. In our opinion, future efforts need to focus on understanding how parasites invade and penetrate the tissues of their hosts and how they potentiate and control the ensuing immune responses, particularly in the first days of infection. Emerging 'omics' data employed in an unbiased approach are helping us understand liver fluke biology and, in parallel with new immunological data, to identify molecules that are essential to parasite development and accessible to vaccine-induced immune responses.

Immunopathological study of parasitic cholangitis in cetaceans

This paper describes the immunophenotype of cellular inflammatory infiltrates in chronic cholangitis in six common dolphins (Delphinus delphis), four striped dolphins (Stenella coeruleoalba), three Atlantic spotted dolphins (Stenella frontalis) and one pygmy sperm whale (Kogia Breviceps) found stranded along the coasts of the Canary Islands (Spain). A panel of 5 antibodies previously tested in dolphins (anti-CD3, -IgG, -MHC class II, -S100 protein and -lysozyme) were used. The present work also reports cross reactivity with dolphin antigens of two antibodies not used to date in dolphins (anti-mouse iNOS and anti-mouse Foxp3). The most common type of cholangitis found was chronic granulomatous cholangitis, associated with the presence of the parasite Campula spp., or its eggs in bile ducts. The cellular composition of the hepatic inflammatory infiltrate associated to chronic parasitic cholangitis was closely similar to that found in the cortex of control lymph nodes, including the presence of S100(+) and MHC class II(+) dendritic-like cells in lymphoid follicles and interfollicular areas. Only occasional macrophages expressed iNOS, whereas Foxp3(+) lymphocytes were not found in any of the lesions described in the different types of cholangitis.

Evaluation of local immune response to Fasciola hepatica experimental infection in the liver and hepatic lymph nodes of goats immunized with Sm14 vaccine antigen

Protection against Fasciola hepatica in goats immunized with a synthetic recombinant antigen from Schistosoma mansoni fatty acid-binding protein 14 (rSm14) was investigated by assessing worm burdens, serum levels of hepatic enzymes, faecal egg count and hepatic damage, which was evaluated using gross and microscopic morphometric observation. The nature of the local immune response was assessed by examining the distribution of CD2+, CD4+, CD8+ and γ´+ T lymphocytes along with IgG+, IL-4+ and IFN-γ+ cells in the liver and hepatic lymph nodes (HLN). The goats used consisted of group 1 (unimmunized and uninfected), group 2 [infected control - immunized with Quillaia A (Quil A)] and group 3 (immunized with rSm14 in Quil A and infected), each containing seven animals. Immunization with rSm14 in Quil A adjuvant induced a reduction in gross hepatic lesions of 56.6% (p < 0.001) and reduced hepatic and HLN infiltration of CD2+, CD4+, CD8+ and γ´+ T lymphocytes as well as IL-4+ and IFN-γ+ cells (p < 0.05). This is the first report of caprine immunization against F. hepatica using a complete rSm14 molecule derived from S. mansoni. Immunization reduced hepatic damage and local inflammatory infiltration into the liver and HLN. However, considering that Quil A is not the preferential/first choice adjuvant for Sm14 immunization, further studies will be undertaken using the monophosphoryl lipid A-based family of adjuvants during clinical trials to facilitate anti-Fasciolavaccine development.

Evaluation of hepatic damage and local immune response in goats immunized with native glutathione S-transferase of Fasciola hepatica

Worm burden, hepatic damage and local cellular and humoral immune responses were assessed in goats immunized with glutathione-S-transferase and challenged with Fasciola hepatica. Infected but unimmunized and uninfected control groups were also studied. Hepatic damage was evaluated grossly and microscopically. Local immune response was evaluated by (1) microscopical examination of hepatic lymph nodes (HLNs); (2) analysis of the distribution of CD2(+), CD4(+), CD8(+), T-cell receptor gammadelta(+) lymphocytes and immunoglobulin (Ig) G(+) plasma cells; and (3) investigation of the distribution of cells expressing interleukin (IL)-4 and interferon (IFN)-gamma in the hepatic inflammatory infiltrates and HLNs. Immunized animals did not have significant reduction in fluke number, but there was significant (P<0.05) reduction of fluke size relative to the control groups. The lesions in the two infected groups were similar and consisted of fibrous perihepatitis and white tortuous tracts, mainly involving the left hepatic lobe. Microscopical lesions were similar in both infected groups and were typical of chronic fascioliosis. These included portal fibrosis, inflammatory infiltration with plasma cells, formation of lymphoid follicles, accumulation of haemosiderin-laden macrophages and granulomatous foci. Both infected groups had a marked local immune response characterized by infiltration of CD2(+), CD4(+) and CD8(+) T lymphocytes, and IgG(+) plasma cells in hepatic lesions and in HLNs. There was no expression of IL-4 or INF-gamma by cells in the hepatic inflammatory infiltrate, but expression of INF-gamma in HLNs was much lower than that of IL-4, suggesting an immune response dominated by T helper 2 cells.

Evaluation of hepatic changes and local and systemic immune responses in goats immunized with recombinant Peroxiredoxin (Prx) and challenged with Fasciola hepatica

Protection against Fasciola hepatica in goats immunized with Peroxiredoxin (Prx) was assessed. The experimental trial consisted of three groups of seven animals; group 1 were unimmunized and uninfected, group 2 were immunized with adjuvant only and group 3 were immunized with recombinant Prx in adjuvant (immunized and infected). Immunization with Prx in Quil A adjuvant, group 3, induced a reduction in fluke burden of 33.04% when compared to adjuvant control, group 2, although this difference was not significant. The hepatic gross and microscopical morphometric study revealed lower damage in the Prx-immunized compared to group 2 (p<0.05). Furthermore, immunohistochemical studies revealed that the Prx-immunized group exhibited reduced infiltration of CD4(+), CD8(+), IFN-gamma(+) and TCR(+) (p<0.05); and CD2(+) and IL-4(+) (p<0.001) in hepatic lesions. Levels of anti-Prx serum IgG in group 3 showed a significant increase at the 4th week after challenge infection compared with group 2 (p<0.0001). This is the first report of ruminant immunization with recombinant Prx of F. hepatica. The study shows that this vaccine significantly reduces hepatic damage and encourages further studies to improve the vaccine efficacy.

Study of the local immune response to Fasciola hepatica in the liver and hepatic lymph nodes of goats immunised with a peptide of the Sm14 antigen

The nature of the local immune response was assessed studying the distribution of CD2(+), CD4(+), CD8(+), gammadelta(+) T lymphocytes, IgM(+) B cells, IL-4(+) and IFN-gamma(+) cells in the liver and hepatic lymph nodes (HLN) of goats immunised with a synthetic peptide of the Sm14 antigen from Schistosoma mansoni and challenged with Fasciola hepatica. A morphometric study of HLN was also carried out in order to evaluate the hyperplasia of lymphoid follicles. Despite the decrease in fluke burdens found in the immunised group (45.9%) respect to the infected control group, this difference was not statistically significant due to the high individual variability. In liver, a significant increase of CD2(+), CD4(+), CD8(+), gammadelta(+) T lymphocytes was found in the infected groups respect to the uninfected control and in the infected control respect to the immunised group. HLN showed a significant enlargement due to the hyperplasia of lymphoid follicles and infiltration of CD2(+), CD4(+), CD8(+), gammadelta(+) T lymphocytes in both infected groups respect to the uninfected control, with no significant differences between the infected control and immunised group. IFN-gamma(+) lymphoid cells was absent or very occasional in HLN where the number of IL-4(+) cells was higher than that of IFN-gamma, suggesting a polarized Th2 response in immunised and in infected control group.

Characterization of local immune response against lungworms in naturally infected sheep

This study describes the immunohistochemical and histochemical phenotypes of inflammatory cells in sheep lungs infected with lungworms. A total of 20 naturally infected sheep lungs were used. Protostrongylus spp., Muellerius capillaris, Neostrongylus linearis, and Cystocaulus ocreatus were the chief organisms determined from such lesions, which were of a chronic nature. All the lungs had many developmental stages of the parasites and a similar inflammatory response, which included numerous mast cells, eosinophils, T cells, B cells, dendritic cells, and macrophages. In the bronchial and interstitial tissues, the inflammatory cells were dominated by MHCII, CD1, CD4, CD5, CD14, CD21, IgM, and CD172a positive cells, whereas CD2 and WC1 positive cells were detected less. The data provided additional evidence that subsets of inflammatory cells were included within ovine lungs infected with lungworms; however, understanding the entire immune-response process and development of resistance to lungworms in sheep remain to be clearly elucidated.

A study of the liver of goats immunized with a synthetic peptide of the Sm14 antigen and challenged with Fasciola hepatica

A synthetic peptide of the Sm14 antigen of Schistosoma mansoni was used to immunize goats against experimental challenge with Fasciola hepatica. The goats used consisted of: group 1 (unimmunized and uninfected [controls]); group 2 (unimmunized and infected); group 3 (immunized and infected). Compared with group 2, the animals of group 3 showed at necropsy a reduction in hepatic worm burden; however, because of variability in the two groups this reduction was not statistically significant. A gross morphometric study of the hepatic changes revealed a correlation between lesions and worm burdens in group 3. No significant differences in damaged areas were found between groups 2 and 3, except that group 2 had more severe bile duct hyperplasia. A striking hepatic inflammatory infiltration of CD3+ T lymphocytes and IgG+ plasma cells was found in both groups 2 and 3, especially the latter.

Neuropathological survey of fallen stock: active surveillance reveals high prevalence of encephalitic listeriosis in small ruminants

This paper describes the prevalence of brain lesions in the Swiss fallen stock population of small ruminants. 3075 whole brains (75% sheep, 25% goats) were collected as part of a year-long active survey of transmissible spongiform encephalopathies (TSEs) in small ruminants conducted by the Swiss authorities between July 2004 and July 2005. All fallen stock brains were systematically examined by histopathology to obtain reliable data on histologically identifiable brain lesions. Lesions were found in an unexpectedly high number of animals (8.1% of all examined brains). A wide spectrum of diseases was detected showing that this approach provides an excellent opportunity to screen for the prevalence of neurological diseases. Encephalitic listeriosis was by far the most frequent cause of CNS lesions in both species and its prevalence was unexpectedly high when compared to notified confirmed cases. In conclusion, the prevalence of listeriosis as estimated by passive surveillance based on the notification of clinical suspects has been underestimated in the past.

Immunohistochemical study of the local immune response in lambs experimentally infected with Dicrocoelium dendriticum (Digenea)

Phenotypic expression of inflammatory cells in liver and hepatic lymph nodes (HLN) has been examined in lambs experimentally infected with Dicrocoelium dendriticum using immunohistochemical techniques. Thirty-two lambs, 12 infected with 1,000 D. dendriticum metacercariae, 12 with 3,000, and 8 controls were used. Half the lambs in each group were slaughtered on days 60 and 180 post-infection (p.i.), respectively. Primary antibodies (Abs) against T cell epitopes (CD3+, CD4+, CD8+ and WC1+ gammadelta), B cell epitopes (CD79alphacy+, CD45R+), immunoglobulin (IgG)-bearing plasma cells, macrophages (CD14+, VPM32+) and major histocompatibility complex (MHC) class IIbeta antigen were used. T lymphocytes (CD3+, CD4+ and CD8+) and B lymphocytes (CD79alphacy+ and CD45R+) with diffuse pattern or forming lymphoid aggregates and follicles surrounded the septal bile ducts (SBD) and inter-lobular bile ducts, whereas the WC1 gammadelta T cells were scattered. Numerous IgG+ plasma cells were observed around SBD. CD14 and VPM32+ macrophages intermingled with lymphocytes were immunostained by the anti-MHC class IIbeta. This Ab also reacted with lymphoid cells. Likewise, increased positive immunostaining for all Abs used was observed in the HLN of infected lambs. There was no qualitative difference regarding the phenotype expression of inflammatory cells between the lambs infected with D. dendriticum. The humoral and cell-mediated local immune responses observed were similar in the two groups of lambs infected with different doses.