A 2.9 kDa Fasciola hepatica-recombinant protein based ELISA test for the detection of current-ovine fasciolosis trickle infected

Techniques for the diagnosis of Fasciola infections in animals: room for improvement

The common liver fluke, Fasciola hepatica, causes fascioliasis, a significant disease in mammals, including livestock, wildlife and humans, with a major socioeconomic impact worldwide. In spite of its impact, and some advances towards the development of vaccines and new therapeutic agents, limited attention has been paid to the need for practical and reliable methods for the diagnosis of infection or disease. Accurate diagnosis is central to effective control, particularly given an emerging problem with drug resistance in F. hepatica. Traditional coprological techniques have been widely used, but are often unreliable. Although there have been some advances in establishing immunologic techniques, these tools can suffer from a lack of diagnostic specificity and/or sensitivity. Nonetheless, antigen detection tests seem to have considerable potential, but have not yet been adequately evaluated in the field. Moreover, advanced nucleic acid-based methods appear to offer the most promise for the diagnosis of current infection. This chapter (i) provides a brief account of the biology and significance of F. hepatica/fascioliasis, (ii) describes key techniques currently in use, (iii) compares their advantages/disadvantages and (iv) reviews polymerase chain reaction-based methods for specific diagnosis and/or the genetic characterization of Fasciola species.

Evaluation and characterization of Fasciola hepatica tegument protein extract for serodiagnosis of human fascioliasis

Tegument protein extract from Fasciola hepatica adult flukes (FhTA) was obtained and assessed for its potential as a diagnostic agent for the serological detection of human fascioliasis using an indirect enzyme-linked immunosorbent assay (ELISA). In an analysis of sera from 45 patients infected with F. hepatica, sera from 41 patients with other parasitic infections, and sera from 33 healthy controls, the FhTA-ELISA showed sensitivity, specificity, and accuracy of 91.1%, 97.3%, and 95%, respectively. Specific IgG1 and IgG4 were the antibody isotypes mainly detected in sera from patients with fascioliasis. Polypeptides of 52, 38, 24 to 26, and 12 to 14 kDa were identified by Western blotting as the most immunoreactive components of the FhTA. A proteomic approach led us to identify enolase, aldolase, glutathione S-transferase, and fatty acid binding protein as the major immunoreactive components of the FhTA.

Fasciola hepatica saposin-like protein-2-based ELISA for the serodiagnosis of chronic human fascioliasis

An indirect enzyme-linked immunosorbent assay (ELISA) was developed and evaluated for its diagnostic ability to detect human IgG antibodies against Fasciola hepatica saposin-like protein-2. The assay was compared with an indirect ELISA with excretory-secretory products (FhES) from adult F. hepatica. In an analysis of the sera of 37 patients infected with F. hepatica, 40 patients with other parasitic infections, and 50 healthy controls, the sensitivity of both ELISA assays was 100%. However, the FhSAP2-based ELISA was more specific (95.6%) than the FhES-ELISA (91.9%). These results demonstrated that FhSAP2 can be used in the serodiagnosis of chronic human fascioliasis with the additional advantage of being relatively cheap and easy to produce. Studies are in progress to evaluate this FhSAP2-ELISA assay in a large-scale prevalence surveys in endemic areas.

Fasciola hepatica and Schistosoma mansoni: identification of common proteins by comparative proteomic analysis

It is not unusual to find common molecules among parasites of different species, genera, or phyla. When those molecules are antigenic, they may be used for developing drugs or vaccines that simultaneously target different species or genera of parasite. In the present study, we used a proteomic-based approach to identify proteins that are common to adult Fasciola hepatica and Schistosoma mansoni. Whole-worm extracts from each parasite were separated by 2-dimensional electrophoresis (2-DE), and digital images of both proteomes were superimposed using imaging software to identify proteins with identical isoelectric points and molecular weights. Protein identities were determined by mass spectrometry. Imaging and immunoblot analyses identified 28 immunoreactive proteins that are common to both parasites. Among these molecules are antioxidant proteins (thioredoxin and glutathione-S-transferase), glycolytic enzymes (glyceraldehyde 6-phosphate dehydrogenase and enolase), proteolytic enzymes (cathepsin-L and -D), inhibitors (Kunitz-type, Stefin-1), proteins with chaperone activity (heat shock protein 70 and fatty acid-binding protein), and structural proteins (calcium-binding protein, actin, and myosin). Some of the identified proteins could be used to develop drugs and vaccines against fascioliasis and schistosomiasis.

Standardisation of a coproantigen reduction test (CRT) protocol for the diagnosis of resistance to triclabendazole in Fasciola hepatica

A sheep trial was performed to standardise a coproantigen reduction test (CRT) protocol for the diagnosis of resistance to triclabendazole (TCBZ) in Fasciola hepatica). The CRT employs the BIO K201 Fasciola coproantigen ELISA (Bio-X Diagnostics, Jemelle, Belgium) to test for the presence of F. hepatica coproantigens in a faecal sample. If it is coproantigen-positive, the CRT protocol recommends that faecal samples are re-tested for coproantigens at 14 days post-treatment (dpt), with negative testing at this point indicating TCBZ success. Initial work aimed to confirm the sensitivity of the BIO K201 ELISA for Fasciola infection and investigate whether coproantigens represent a robust reduction marker of TCBZ efficacy. Thirty-eight, indoor-reared sheep were artificially infected with F. hepatica isolates known to be susceptible (Cullompton) and resistant (Sligo) to TCBZ action, respectively. Treatment was administered at 12 weeks post-infection (wpi), with 2 sheep groups, infected with each isolate, culled at 2 and 4 weeks post-treatment (wpt), respectively. Necropsy was performed to confirm treatment efficacy. Individual faecal samples were collected twice-weekly throughout the trial period. Additional work focused on the effect of temperature on faecal sample collection and storage. Faecal samples collected from sheep positive for F. hepatica infection were sub-sampled and left at room temperature. Individual sub-samples were tested by ELISA on consecutive days and these readings compared to the original test result on the day of collection. In addition, ELISA values were compared between faecal sub-samples prepared on the day of sampling and post storage at -20°C. Also, an immunocytochemical study was performed to determine the tissue site of origin of the coproantigen protein in the fluke. Results showed that the BIO K201 ELISA was sensitive for Fasciola coproantigens, with coproantigens detectable from 5 wpi onwards. The suitability of coproantigens as a diagnostic marker of TCBZ efficacy was supported by the absence and presence of coproantigens in TCBZ-treated Cullompton (TCBZ-susceptible) and Sligo (TCBZ-resistant) F. hepatica infections at 2 and 4 wpt, respectively. Study results suggest that low to moderate temperature has little, if any, impact on coproantigen stability in faecal samples, but that higher temperatures may have. Immunolabelling for the coproantigen showed that it was specific to the gastrodermal cells of both adult and juvenile flukes.

A recombinant-based ELISA evaluating the efficacy of netobimin and albendazole in ruminants with naturally acquired fascioliasis

The therapeutic efficacy of albendazole and netobimin in ruminants with naturally occurring fascioliasis was investigated using a recombinant-based ELISA. The variation in the IgG response against a 2.9-kDa recombinant protein (FhrAPS), termed efficacy index (EI) 1, and the egg-output changes, termed EI 2, were used to evaluate drug efficacy. The values of EI 1 ranged between 0% and 50% in sheep, and between 0% and 30% in cattle after treatment with albendazole and netobimin. Similar EI 2 values were observed in sheep receiving albendazole or netobimin, but the highest values were found in cattle treated with netobimin. The significant reduction in the IgG response to FhrAPS found in this study shows promise in terms of developing alternative methods for evaluating the efficacy of chemotherapy against Fasciola hepatica in grazing ruminants.

Immunodiagnosis of current fasciolosis in sheep naturally exposed to Fasciola hepatica by using a 2.9kDa recombinant protein

A 2.9 kDa recombinant-Fasciola hepatica protein (FhrAPS) was employed to estimate the prevalence of fasciolosis in sheep maintained under field conditions. For this purpose, 340 samples with known status in relation to fasciolosis by using a direct-ELISA and the coprological sedimentation were used. These samples were analysed by using an indirect-ELISA (iELISA) and the FhrAPS recombinant protein and excretory/secretory antigens (FhES) of this trematode. Current fasciolosis (CF) was named when results were positive to antigenemia and/or coprology. Out of 198 sheep with current fasciolosis, 68% were positive to the FhrAPS-ELISA test and 53% to the FhES. We observed 14% of the CF-neg sheep were positive to the FhrAPS, whereas this percentage was 52% with the FhES. A significant correlation between FhrAPS and current fasciolosis was obtained (r2=0.513, p=0.001). We concluded that the FhrAPS provides a more suitable antigen than FhES for developing field trials to know the prevalence of early and current fasciolosis.

Progress in the development of Fasciola hepatica vaccine using recombinant fatty acid binding protein with the adjuvant adaptation system ADAD

Fatty acid binding proteins (FABP) have been designed as a potential vaccine against fasciolosis. In this work, the immunoprophylaxis of the recombinant Fh15 FABP from F. hepatica (Fh15) in adjuvant/immunomodulator ADAD system was evaluated using mice and sheep challenged with F. hepatica. The ADAD system combines the Fh15 antigen with an immunomodulator (hydroalcoholic extract of Polypodium leucotomos; PAL) and/or an adjuvant (saponins of Quillaja saponaria; Qs) in a water/oil emulsion (30/70) with a non-mineral oil (Montanide). All the infected control mice died by 41-48 days post-infection. The mice vaccinated with ADAD only with PAL+Fh15 present a survival rate of 40-50% and those vaccinated with ADAD containing PAL+Qs+Fh15 had a survival rate of 50-62.5%. IgG1 antibodies were lower in surviving mice in comparison with non-surviving mice. The sheep vaccinated with ADAD PAL+Qs+Fh15 showed lower fluke recovery (43%), less hepatic lesions and higher post-infection daily weight gain than F. hepatica infected control animals. Thus, the ADAD system using recombinant fatty acid binding proteins from F. hepatica could be a good option to develop vaccines against F. hepatica.

THE USE OF MM3 MONOCLONAL ANTIBODIES FOR THE EARLY IMMUNODIAGNOSIS OF OVINE FASCIOLIASIS

This study reports a new capture ELISA (MM3-SERO) for the serodiagnosis of sheep fascioliasis, based on the use of the monoclonal antibody (mAb) MM3. Like our previously reported indirect ELISA method, based on the use of a FPLC-purified fraction (fraction IV) of the Fasciola hepatica excretion/secretion antigens (ESAs), this new test was able to detect animals infected with very small numbers of metacercariae (5-40) and showed no cross-reaction with sera from sheep infected with other parasites, i.e., Moniezia spp., Cysticercus tenuicollis, and Dicrocoelium dendriticum. In contrast with these 2 methods, some sera (mainly those obtained from animals infected with D. dendriticum) showed high reactivities in indirect ELISA with whole F. hepatica ESAs used as control. Interestingly, the MM3-SERO ELISA has a better signal-to-noise ratio than the fraction-IV ELISA, thus allowing detection of seroconversion in infected sheep on average 1 wk earlier (3.2 +/- 0.4 wk postinfection [PI] for MM3-SERO ELISA vs. 4.2 +/- 0.9 wk PI for fraction IV ELISA). Moreover, the antibody response detected with MM3-SERO ELISA was more uniform, with seroconversion always occurring at 4 wk PI in sheep with 1-2 flukes and at 3 wk PI in sheep with more than 2 flukes. The MM3-SERO ELISA was also used to evaluate the kinetics of antibody response against MM3-recognized antigens in sera from sheep experimentally infected with F. hepatica and then treated with triclabendazole. Our results showed that antibody levels dropped by about 25% during the 4-wk observation period following the flukicide treatment, whereas they remained invariably high in all sheep left untreated. We conclude that the MM3-SERO ELISA is a 100% sensitive and 100% specific test for the early serodiagnosis of sheep fascioliasis. Preliminary studies in our laboratory seem to indicate that this method may also be useful for the determination of anti-F. hepatica antibodies in serum and milk of other ruminants. A commercial version of MM3-SERO is currently available from BIO X Diagnostics (La Jemelle, Belgium).