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

Recombinant Fasciola hepatica Fatty Acid Binding Protein as a Novel Anti-Inflammatory Biotherapeutic Drug in an Acute Gram-Negative Nonhuman Primate Sepsis Model

Due to their phylogenetic proximity to humans, nonhuman primates (NHPs) are considered an adequate choice for a basic and preclinical model of sepsis. Gram-negative bacteria are the primary causative of sepsis. During infection, bacteria continuously release the potent toxin lipopolysaccharide (LPS) into the bloodstream, which triggers an uncontrolled systemic inflammatory response leading to death. Our previous research has demonstrated in vitro and in vivo using a mouse model of septic shock that Fh15, a recombinant variant of the Fasciola hepatica fatty acid binding protein, acts as an antagonist of Toll-like receptor 4 (TLR4) suppressing the LPS-induced proinflammatory cytokine storm. The present communication is a proof-of concept study aimed to demonstrate that a low-dose of Fh15 suppresses the cytokine storm and other inflammatory markers during the early phase of sepsis induced in rhesus macaques by intravenous (i.v.) infusion with lethal doses of live Escherichia coli. Fh15 was administered as an isotonic infusion 30 min prior to the bacterial infusion. Among the novel findings reported in this communication, Fh15 (i) significantly prevented bacteremia, suppressed LPS levels in plasma, and the production of C-reactive protein and procalcitonin, which are key signatures of inflammation and bacterial infection, respectively; (ii) reduced the production of proinflammatory cytokines; and (iii) increased innate immune cell populations in blood, which suggests a role in promoting a prolonged steady state in rhesus macaques even in the presence of inflammatory stimuli. This report is the first to demonstrate that a F. hepatica-derived molecule possesses potential as an anti-inflammatory drug against sepsis in an NHP model.

IMPORTANCE Sepsis caused by Gram-negative bacteria affects 1.7 million adults annually in the United States and is one of the most important causes of death at intensive care units. Although the effective use of antibiotics has resulted in improved prognosis of sepsis, the pathological and deathly effects have been attributed to the persistent inflammatory cascade. There is a present need to develop anti-inflammatory agents that can suppress or neutralize the inflammatory responses and prevent the lethal consequences of sepsis. We demonstrated here that a small molecule of 14.5 kDa can suppress the bacteremia, endotoxemia, and many other inflammatory markers in an acute Gram-negative sepsis rhesus macaque model. These results reinforce the notion that Fh15 constitutes an excellent candidate for drug development against sepsis.

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.

Promising Technologies in the Field of Helminth Vaccines

Helminths contribute a larger global burden of disease than both malaria and tuberculosis. These eukaryotes have caused human infections since before our earliest recorded history (i.e.: earlier than 1200 B.C. for Schistosoma spp.). Despite the prevalence and importance of these infections, helminths are considered a neglected tropical disease for which there are no vaccines approved for human use. Similar to other parasites, helminths are complex organisms which employ a plethora of features such as: complex life cycles, chronic infections, and antigenic mimicry to name a few, making them difficult to target by conventional vaccine strategies. With novel vaccine strategies such as viral vectors and genetic elements, numerous constructs are being defined for a wide range of helminth parasites; however, it has yet to be discussed which of these approaches may be the most effective. With human trials being conducted, and a pipeline of potential anti-helminthic antigens, greater understanding of helminth vaccine-induced immunity is necessary for the development of potent vaccine platforms and their optimal design. This review outlines the conventional and the most promising approaches in clinical and preclinical helminth vaccinology.

Recent Advances and Methodological Considerations on Vaccine Candidates for Human Schistosomiasis

Schistosomiasis remains a neglected tropical disease of major public health concern with high levels of morbidity in various parts of the world. Although considerable efforts in implementing mass drug administration programs utilizing praziquantel have been deployed, schistosomiasis is still not contained. A vaccine may therefore be an essential part of multifaceted prevention control efforts. In the 1990s, a joint United Nations committee promoting parasite vaccines shortlisted promising candidates including for schistosomiasis discussed below. After examining the complexity of immune responses in human hosts infected with schistosomes, we review and discuss the antigen design and preclinical and clinical development of the four leading vaccine candidates: Sm-TSP-2 in Phase 1b/2b, Sm14 in Phase 2a/2b, Sm-p80 in Phase 1 preparation, and Sh28GST in Phase 3. Our assessment of currently leading vaccine candidates revealed some methodological issues that preclude a fair comparison between candidates and the rationale to advance in clinical development. These include (1) variability in animal models - in particular non-human primate studies - and predictive values of each for protection in humans; (2) lack of consensus on the assessment of parasitological and immunological parameters; (3) absence of reliable surrogate markers of protection; (4) lack of well-designed parasitological and immunological natural history studies in the context of mass drug administration with praziquantel. The controlled human infection model - while promising and unique - requires validation against efficacy outcomes in endemic settings. Further research is also needed on the impact of advanced adjuvants targeting specific parts of the innate immune system that may induce potent, protective and durable immune responses with the ultimate goal of achieving meaningful worm reduction.

Antigen-specific response of CD4+ T cells and hepatic lymph node cells to Fasciola hepatica-derived molecules at the early and late stage of the infection in sheep

The immunomodulatory capacity of F. hepatica antigens is probably one of the main reasons for the development of a driven non-protective Th2 immune response. In this study, we analysed the cellular response of hepatic lymph node cells and CD4⁺ T cells in terms of proliferative response, efficiency of antigen presentation and cytokine production, to F. hepatica-derived molecules, at early and late stages of the infection. Thirty-one sheep were allocated into five groups and were slaughtered at 16 dpi and 23 wpi. In order to analyse antigen-specific response, the following F. hepatica recombinant molecules were used: rFhCL1, rFhCL2, rFhCL3, rFhCB1, rFhCB2, rFhCB3, rFhStf-1, rFhStf-2, rFhStf-3 and rFhKT1. A cell proliferation assay using hepatic lymph node cells and an antigen presentation cell assay using CD4⁺ T cells were performed. At 16 dpi, all molecules but rFhStf-2 and rFhKT1 elicited a significant cell proliferative response on hepatic lymph node cells of infected animals. At both early and late stage of the infection, antigen presentation of rFhCB3 and rFhCL2 resulted in higher stimulation index of CD4⁺ T cells which was IL-2 mediated, although no statistically significant when compared to uninfected animals. Significant cytokine production (IL-4, IL-10 and IFN-γ) was conditioned by the antigen-specific cell stimulation. No CD4⁺ T cell exhaustion was detected in infected sheep at the chronic stage of the infection. This study addressed antigen-specific response to F. hepatica-derived molecules that are involved in key aspects of the parasite survival within the host.

Current Status for Controlling the Overlooked Caprine Fasciolosis

Simple Summary

Retaining sustainable agricultural systems is essential to feed the expanding population. Helminth parasite infections impact livestock production values and yields, including infections in goats, which are often overlooked. There is a requirement to collate caprine-specific knowledge surrounding fasciolosis, caused by Fasciola hepatica and Fasciola gigantica (liver flukes). Current liver fluke control methods include drug application and pasture management. This review aims to outline goat-specific fasciolosis vaccine development and the potential for alternative control methods.

Abstract

The disease fasciolosis is caused by the liver flukes Fasciola hepatica and F. gigantica, which infect a wide range of mammals and production livestock, including goats. These flatworm parasites are globally distributed and predicted to cost the livestock industry a now conservative USD 3 billion per year in treatment and lowered on-farm productivity. Infection poses a risk to animal welfare and results in lowered fertility rates and reduced production yields of meat, milk and wool. This zoonotic disease is estimated to infect over 600 million animals and up to 2.4 million humans. Current and future control is threatened with the global emergence of flukes resistant to anthelmintics. Drug resistance calls for immediate on-farm parasite management to ensure treatments are effective and re-infection rates are kept low, while a sustainable long-term control method, such as a vaccine, is being developed. Despite the recent expansion of the goat industry, particularly in developing countries, there are limited studies on goat-focused vaccine control studies and the effectiveness of drug treatments. There is a requirement to collate caprine-specific fasciolosis knowledge. This review will present the current status of liver fluke caprine infections and potential control methods for application in goat farming.

Goat γδ T cells

Goats are important food animals and are disseminated globally because of their high adaptability to varying environmental conditions and feeding regimes that provide them with a comparative advantage. Productivity is impacted by infectious diseases; this then contributes to societal poverty, food insecurity, and international trade restrictions. Since γδ T cells have been shown to have vital roles in immune responses in other mammals we reviewed the literature regarding what is known about their functions, distribution in tissues and organs and their responses to a variety of infections in goats. It has been shown that caprine γδ T cells produce interferon-γ and IL-17, are found in a variety of lymphoid and nonlymphoid tissues and constitute a significant population of blood mononuclear cells. Their representation in tissues and their functional responses may be altered concomitant with infection. This review summarizes caprine γδ T cell responses to Brucella melitensis, Fasciola hepatica, Mycobacterium avium paratuberculosis, caprine arthritis encephalitis virus (CAEV), and Schistosoma bovis in infected or vaccinated goats. Caprine γδ T cells have also been evaluated in goats infected with M. caprae, Ehrilichia ruminantium, Haemonchus contortus and peste des petits ruminants (PPR) virus but found to have an unknown or limited response or role in either protective immunity or immunopathogenesis in those cases.

Re-evaluation of Quillaia extract (E 999) as a food additive and safety of the proposed extension of use

The EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS) provides a scientific opinion on Quillaia extract (E 999) when used as a food additive and the evaluation of the safety of its proposed extension of use as a food additive in flavourings. The Scientific Committee for Food (SCF) in 1978 established an acceptable daily intake (ADI) of 0-5 mg spray-dried extract/kg body weight (bw) per day for E 999. The Joint FAO/WHO Expert Committee on Food Additives (JECFA) established in its latest evaluation a group ADI of 0-1 mg/kg bw per day, expressed as quillaia saponins, for Quillaia extract for Type 1 and Type 2. The Panel considered it likely that intact Quillaia extract saponins are absorbed to a low extent, are hydrolysed in the gastrointestinal (GI) tract and that the aglycone is absorbed only to a limited extent. The Panel considered that the genotoxicity data available did not indicate a concern for genotoxicity. Taking into account the available toxicological database, various no observed adverse effect levels (NOAELs) relevant for the derivation of an ADI were identified. The Panel considered that the 2-year study in rats was the most robust and that the NOAEL of 1,500 mg Quillaia extract/kg bw per day could be used to derive the ADI for E 999. Considering that the adverse effects reported were due to the presence of saponins in the extract, that saponins were present in Quillaia extract Type 1 (around 20%) and using an uncertainty factor of 100, the Panel derived a ADI of 3 mg saponins/kg bw per day for E 999. None of the exposure estimates for the different population groups of the refined brand-loyal scenario exceeded the ADI of 3 mg saponins/kg bw per day. The proposed extension of use also would not result in an exceedance of this ADI for the refined scenario. The Panel proposed some recommendations for the European Commission to consider, in particular revising the EU specifications for E 999 in order to differentiate the extracts of Quillaia according to the saponins content and to include other parameters to better characterise the food additive.

Fasciola and fasciolosis in ruminants in Europe: Identifying research needs

Fasciola hepatica is a trematode parasite with a global distribution, which is responsible for considerable disease and production losses in a range of food producing species. It is also identified by WHO as a re-emerging neglected tropical disease associated with endemic and epidemic outbreaks of disease in human populations. In Europe, F. hepatica is mostly associated with disease in sheep, cattle and goats. This study reviews the most recent advances in our understanding of the transmission, diagnosis, epidemiology and the economic impact of fasciolosis. We also focus on the impact of the spread of resistance to anthelmintics used to control F. hepatica and consider how vaccines might be developed and applied in the context of the immune-modulation driven by the parasite. Several major research gaps are identified which, when addressed, will contribute to providing focussed and where possible, bespoke, advice for farmers on how to integrate stock management and diagnosis with vaccination and/or targeted treatment to more effectively control the parasite in the face of increasing the prevalence of infection and spread of anthelmintic resistance that are likely to be exacerbated by climate change.

Activity of cholinesterases, pyruvate kinase and adenosine deaminase in rats experimentally infected by Fasciola hepatica: Influences of these enzymes on inflammatory response and pathological findings

The aim of this study was to investigate acetylcholinesterase (AChE) in total blood and liver tissue; butyrylcholinesterase (BChE) in serum and liver tissue; adenosine deaminase (ADA) in serum and liver tissue; and pyruvate kinase (PK) in liver tissue of rats experimentally infected by Fasciola hepatica. Animals were divided into two groups with 12 animals each, as follows: group A (uninfected) and group B (infected). Samples were collected at 20 (A1 and B1;n=6 each) and 150 (A2 and B2; n=6 each) days post-infection (PI). Infected animals showed an increase in AChE activity in whole blood and a decrease in AChE activity in liver homogenates (P<0.05) at 20 and 150 days PI. BChE and PK activities were decreased (P<0.05) in serum and liver homogenates of infected animals at 150 days PI. ADA activity was decreased in serum at 20 and 150 days PI, while in liver homogenates it was only decreased at 150 days PI (P<0.05). Aspartate aminotransferase and alanine aminotransferase activities in serum were increased (P<0.05), while concentrations of total protein and albumin were decreased (P<0.05) when compared to control. The histological analysis revealed fibrous perihepatitis and necrosis. Therefore, we conclude that the liver fluke is associated with cholinergic and purinergic dysfunctions, which in turn may influence the pathogenesis of the disease.

Oxidative stress associated with pathological lesions in the liver of rats experimentally infected by Fasciola hepatica

The aim of this study was to analyze the antioxidant status and oxidative profile in serum and liver of rats experimentally infected with Fasciola hepatica and its relationship with pathological findings. Twenty-four rats were divided into two groups: group A consisted of 12 healthy rats and group B of 12 rats infected orally with 20 metacercaria of F. hepatica. At days 20 and 150 post-infection (PI), blood and liver samples of six animals from each group were collected. The protein oxidation (AOPP technique: advanced oxidation protein products) and antioxidants (FRAP technique: ferric reducing antioxidant power) levels were measured in serum and liver. Furthermore, nitrite/nitrate (NOx) levels and lipid peroxidation (TBARS technique: thiobarbituric acid reactive substances) were measured in liver. AOPP and FRAP levels were increased (P < 0.05) in serum and liver of infected animals in acute and chronic infection when compared with healthy animals. The same occurred with TBARS and NOx levels in the liver (P < 0.05). Histopathology revealed periportal fibrous hepatitis, composed of an abundant inflammatory infiltrate in portal spaces on infected animals, as well as bile duct hyperplasia. The results found seem to be related to the host free radical production demonstrated in serum samples and liver due to the parasite infection.

Development of the Brazilian Anti Schistosomiasis Vaccine Based on the Recombinant Fatty Acid Binding Protein Sm14 Plus GLA-SE Adjuvant

Data herein reported and discussed refer to vaccination with the recombinant fatty acid binding protein (FABP) family member of the schistosomes, called Sm14. This antigen was discovered and developed under a Brazilian platform led by the Oswaldo Cruz Foundation, from the Health Ministry in Brazil, and was assessed for safety and immunogenicity in healthy volunteers. This paper reviews past and recent outcomes of developmental phases of the Sm14-based anti schistosomiasis vaccine addressed to, ultimately, impact transmission of the second most prevalent parasitic endemic disease worldwide.

Fasciola hepatica fatty acid binding protein inhibits TLR4 activation and suppresses the inflammatory cytokines induced by lipopolysaccharide in vitro and in vivo

TLR4, the innate immunity receptor for bacterial endotoxins, plays a pivotal role in the induction of inflammatory responses. There is a need to develop molecules that block either activation through TLR4 or the downstream signaling pathways to inhibit the storm of inflammation typically elicited by bacterial LPS, which is a major cause of the high mortality associated with bacterial sepsis. We report in this article that a single i.p. injection of 15 μg fatty acid binding protein from Fasciola hepatica (Fh12) 1 h before exposure to LPS suppressed significantly the expression of serum inflammatory cytokines in a model of septic shock using C57BL/6 mice. Because macrophages are a good source of IL-12p70 and TNF-α, and are critical in driving adaptive immunity, we investigated the effect of Fh12 on the function of mouse bone marrow-derived macrophages (bmMΦs). Although Fh12 alone did not induce cytokine expression, it significantly suppressed the expression of IL-12, TNF-α, IL-6, and IL-1β cytokines, as well as inducible NO synthase-2 in bmMΦs, and also impaired the phagocytic capacity of bmMΦs. Fh12 had a limited effect on the expression of inflammatory cytokines induced in response to other TLR ligands. One mechanism used by Fh12 to exert its anti-inflammatory effect is binding to the CD14 coreceptor. Moreover, it suppresses phosphorylation of ERK, p38, and JNK. The potent anti-inflammatory properties of Fh12 demonstrated in this study open doors to further studies directed at exploring the potential of this molecule as a new class of drug against septic shock or other inflammatory diseases.

Fasciola hepatica fatty acid binding protein induces the alternative activation of human macrophages

The liver fluke Fasciola hepatica is a highly evolved parasite that uses sophisticated mechanisms to evade the host immune response. The immunosuppressive capabilities of the parasite have been associated with antigens secreted through the parasite's tegument, called excretory-secretory products (ESPs). Proteomic studies have identified the fatty acid binding protein (FABP) as one of molecules present in the parasite ESPs. Although FABP has been investigated for potential use in the development of vaccines against fascioliasis, its direct interaction with cells of immune system has not been studied. In this study, FABP was purified in native form from soluble extracts of F. hepatica adult flukes using a combination of molecular sieving chromatography and preparative isoelectric focusing. The immunological effect of the purified protein, termed Fh12, was assayed in vitro using monocyte-derived macrophages (MDM) obtained from healthy human donors. Results from the assay indicate that Fh12 produced a significantly increased arginase expression and activity and induced the expression of chitinase-3-like protein (CHI3L1). The assay also showed that Fh12 downregulated the production of nitric oxide (NO) and the expression of nitric oxide synthase (NOS2). This indicates that Fh12 induced the production of alternatively activated macrophages (AAMϕ). The results also demonstrated the ability of Fh12 to downregulate the secretion of the proinflammatory and inflammatory cytokines tumor necrosis factor alpha (TNF-α), interleukin-12 (IL-12), and IL-1βB, even after stimulation with lipopolysaccharide (LPS), as well as its ability to stimulate the overexpression of IL-10. These results suggest a potent anti-inflammatory role for Fh12, which could occur via targeting of Toll-like receptor 4 (TLR4).

Liver fluke vaccines in ruminants: strategies, progress and future opportunities

The development of a vaccine for Fasciola spp. in livestock is a challenge and would be advanced by harnessing our knowledge of acquired immune mechanisms expressed by resistant livestock against fluke infection. Antibody-dependent cell-mediated cytotoxicity directed to the surface tegument of juvenile/immature flukes is a host immune effector mechanism, suggesting that antigens on the surface of young flukes may represent prime candidates for a fluke vaccine. A Type 1 immune response shortly after fluke infection is associated with resistance to infection in resistant sheep, indicating that vaccine formulations should attempt to induce Type 1 responses to enhance vaccine efficacy. In cattle or sheep, an optimal fluke vaccine would need to reduce mean fluke burdens in a herd below the threshold of 30-54 flukes to ensure sustainable production benefits. Fluke infection intensity data suggest that vaccine efficacy of approximately 80% is required to reduce fluke burdens below this threshold in most countries. With the increased global prevalence of triclabendazole-resistant Fasciolahepatica, it may be commercially feasible in the short term to introduce a fluke vaccine of reasonable efficacy that will provide economic benefits for producers in regions where chemical control of new drug-resistant fluke infections is not viable. Commercial partnerships will be needed to fast-track new candidate vaccines using acceptable adjuvants in relevant production animals, obviating the need to evaluate vaccine antigens in rodent models.

Cathepsin L1 mimotopes with adjuvant Quil A induces a Th1/Th2 immune response and confers significant protection against Fasciola hepatica infection in goats

Thirty goats were randomly allocated in five groups of six animals each, for immunization with 1 × 10(14) phage particles of clones 11, 13, and 13 with Quil A adjuvant and wild-type M13KE phage at the beginning and 4 weeks later. The control group received phosphate-buffered saline. All groups were challenged with 200 metacercariae at week 6 and slaughtered 14 weeks later. The mean worm burdens after challenge were reduced by 46.91% and 79.53% in goats vaccinated with clones 13 and 13 with Quil A (P < 0.05), respectively; no effect was observed in animals immunized with clone 11 and M13KE phage. Animals receiving clones 11, 13, and 13 with Quil A showed a significant reduction in eggs output. Vaccinated animals produced parasite-specific total IgG antibody which were boosted after challenge with metacercariae of F. hepatica. Furthermore, levels of anti-phage total IgG increased rapidly within 2 weeks of the first vaccination and were always significantly higher in all vaccinated goats than in the infected control group. The fluke burden of goats immunized with clones 13 and 13 with Quil A was significantly correlated with IgG2 and total IgG. Goats vaccinated with phage clones produced significantly high titres of IgG1 and IgG2 antibodies indicating a mixed Th1/Th2 response. These data indicate that cathepsin L1 mimotopes has a potential as a vaccine candidate against Fasciola hepatica, whose efficacy will be evaluated in other host species, including those of veterinary importance.

Early hepatic and peritoneal changes and immune response in goats vaccinated with a recombinant glutathione transferase sigma class and challenged with Fasciola hepatica

Changes and local immune response were evaluated in the peritoneal cell populations, duodenal lamina propria and liver from goats immunized with recombinant glutathione transferase sigma class (rFhGST-S1) during early stages of infection with Fasciola hepatica. Group 1 (n=7) was unimmunized and uninfected; group 2 (n=10) was immunized with adjuvant Quil A and infected; group 3 (n=10) was immunised with rFhGST-S1 and infected. Three goats from each group were killed at 7-9 days post-infection (dpi) to evaluate early changes and immune response. The remaining goats were killed at 15 weeks post-infection (wpi). rFhGST-S1 vaccination induced variable response: three goats showed low fluke burden at 15 wpi and two goats showed low hepatic damage at early infection stages. This response was associated to a severe infiltrate of eosinophils in peritoneal fluid and hepatic necrotic foci, high iNOS expression in peritoneal cells and abundant infiltrate of eosinophils surrounding hepatic migrating flukes. T lymphocyte subsets were found in the vicinity of necrotic areas but they were absent in the vicinity of migrating larvae. No significant variation for T cell subsets, except for CD4 and γδ T lymphocytes, that were higher in the Quil A group compared to the rFhGST-S1 group. Expression of IL4 and IFN-γ in the hepatic inflammatory infiltrates was very occasional.

Early and late peritoneal and hepatic changes in goats immunized with recombinant cathepsin L1 and infected with Fasciola hepatica

The aim of the present study was to study peritoneal and hepatic changes during early [7-9 days postinfection (dpi)] and late [15 weeks postinfection (wpi)] infection of goats immunized with recombinant F. hepatica pro cathepsin L1 (rCL1) in Quil A and challenged with Fasciola hepatica. Despite finding no significant reduction in fluke burdens between the control and immunized group, at 15 dpi the rCL1-vaccinated group showed significantly higher weight gain and reduced severity of hepatic lesions compared with the control group that received only Quil A. In the rCL1-vaccinated group, two of three goats sacrificed at 7-9 dpi had little hepatic damage and had a higher percentage of peritoneal eosinophils and elevated induced nitric oxide synthase (iNOS) expression in peritoneal cells than the goats from the control group. Moreover, while these two goats showed a heavy infiltration of eosinophils surrounding migrating flukes, the remaining animals examined at 7-9 dpi had no inflammatory infiltration surrounding migrating flukes. Two out of seven goats in the rCL1-vaccinated group had low fluke burdens and little hepatic damage at 15 wpi, suggesting an effective protective response in some of the vaccinated goats. This protective response did not correlate with peripheral eosinophilia or with serum titres of anti-rCL1 immunoglobulin (Ig) G. The results of the present work suggest that an eosinophil-mediated immune response plays a crucial role in the early effective host response against F. hepatica in goats. Adjuvants designed to increase cell-mediated immunity should be tested in future vaccine trials against F. hepatica.