Production of Monoclonal Antibody Against Excretory-Secretory Antigen of Fasciola hepatica and Evaluation of Its Efficacy in the Diagnosis of Fascioliasis

Comparative evaluation of real-time PCR and ELISA for the detection of human fascioliasis

Fascioliasis is a zoonotic parasitic infection caused by Fasciola species in humans and animals. Despite significant advances in vaccination and new therapeutic agents, little attention has been paid to validating methods for the diagnosis of fascioliasis in humans. Serological techniques are convenient assays that significantly improves the diagnosis of Fasciola infection. However, a more sensitive method is required. The aim of this study was to compare the Real-Time PCR technique with the indirect-ELISA for the detection of Fasciola hepatica in human. Using a panel of sera from patients infected with Fasciola hepatica (n = 51), other parasitic infections (n = 7), and uninfected controls (n = 12), we optimized an ELISA which employs an excretory-secretory antigens from F. hepatica for the detection of human fascioliasis. After DNA extraction from the samples, molecular analysis was done using Real-Time PCR technique based on the Fasciola ribosomal ITS1 sequence. Of 70 patient serum samples, 44 (62.86%) samples were identified as positive F. hepatica infection using ELISA and Real-Time PCR assays. There was no cross-reaction with other parasitic diseases such as toxoplasmosis, leishmaniasis, taeniasis, hydatidosis, trichinosis, toxocariasis, and strongyloidiasis. The significant difference between the agreement and similarity of the results of patients with indirect ELISA and Real-Time PCR was 94.4% and 99.2%, respectively (Cohen's kappa ≥ 0.7; P = 0.02). Based on the Kappa agreement findings, the significant agreement between the results of ELISA and Real-Time PCR indicates the accuracy and reliability of these tests in the diagnosis of F. hepatica in humans.

Immunodiagnosis of cattle fascioliasis using a 27 kDa Fasciola gigantica antigen

Background and Aim:

Diagnosis of fascioliasis depends on clinical symptoms and routine laboratory tests. Recently, antibodies and circulating antigens of Fasciola were used for detecting active infections. Therefore, this study aimed to identify Fasciola gigantica antigens in the sera of infected cattle using Western blotting and enzyme-linked immunosorbent assay (ELISA) for an accurate diagnosis of cattle infected with F. gigantica.

Materials and Methods:

Serum samples were obtained from 108, 23, and 19 cattle infected with Fasciola gigantica, Paramphistomum cervi, and Strongylids, respectively, including 57 non-infected cattle that were used as healthy cattle for the study. Western blotting and ELISA were then used to detect circulating Fasciola antigens at 27 kDa.

Results:

The target epitope was detected in an F. gigantica adult-worm antigen preparation, excretory/secretory products, and serum from cattle infected with F. gigantica. However, it was absent in sera from P. cervi, Strongylids, and healthy cattle. The purified 27 kDa F. gigantica (FPA-27) antigen was also detected in cattle serum using ELISA with high degrees of sensitivity and specificity (94% and 82%, respectively), and the area under the receiver operating characteristic curve was 0.89 with a highly significant correlation of p<0.0001.

Conclusion:

The FPA-27 is proposed to be a promising candidate for the serodiagnosis of fascioliasis in cattle.

Monoclonal antibody against Fasciola gigantica glutathione peroxidase and their immunodiagnosis potential for fasciolosis

Glutathione peroxidases (GPx), major antioxidant enzymes, secreted by Fasciola spp., are important for the parasite evasion and protection against the host's immune responses. In the present study, a monoclonal antibody (MoAb) against recombinant F. gigantica glutathione peroxidase (rFgGPx) was produced by hybridoma technique using spleen cells from BALB/c mice immunized with rFgGPx. This MoAb (named 7B8) is IgG1 with κ light chains, and it reacted specifically with rFgGPx at a molecular weight 19 kDa as shown by immunoblotting, and reacted with the native FgGPx in the extracts of whole body (WB), metacercariae, newly excysted juveniles (NEJs), 4 week-old juveniles and adult F. gigantica as shown by indirect ELISA. It did not cross react with antigens in WB fractions from other adult trematodes, including Fischoederius cobboldi, Paramphistomum cervi, Setaria labiato-papillosa, Eurytrema pancreaticum, Gastrothylax crumenifer and Gigantocotyle explanatum. By immunolocalization, MoAb against rFgGPx reacted with the native protein in the tegument, vitelline cells, and eggs of adult F. gigantica. In addition, the sera from mice experimentally infected with F. gigantica were tested positive by this indirect sandwich ELISA. This result indicated that FgGPx is an abundantly expressed parasite protein that is secreted into the tegumental antigens (TA), therefore, FgGPx and its MoAb may be used for immunodiagnosis of both early and late fasciolosis gigantica in animals and humans.

Development and evaluation of a colloidal gold immunochromatographic assay based on recombinant protein CatL1D for serodiagnosis of sheep fasciolosis

Fasciolosis is a zoonotic parasitic disease that seriously endangers the development of animal husbandry and human health. In order to develop a rapid serological diagnostic method for fasciolosis in ruminants, the CatL1D and CatB4 genes of Fasciola hepatica were amplified by reverse transcription polymerase chain reaction (PCR) and cloned, respectively, and then the CatL-B fusion gene (MeCatL-B) was constructed by gene splicing by overlap extension PCR technique. The recombinant rCatL1D, rCatB4 and rMeCatL-B proteins were then prepared by prokaryotic expression, respectively, and the recombinant protein with high specificity and sensitivity was screened via indirect enzyme-linked immunosorbent assay. Using the selected recombinant protein rCatL1D as a diagnostic antigen, we developed a colloidal gold immunochromatographic assay (CGIA) for detecting F. hepatica-specific antibodies, and 426 serum samples of slaughtered sheep were used to evaluate the sensitivity and specificity of F. hepatica CGIA assay. The results showed that the sensitivity and specificity of rCatL1D protein (100%, 96.67%) were higher than those of rCatB4 (94.29%, 80%) and rMeCatL-B (91.43%, 90%). Compared with the gold standard post-mortem inspection, the specificity and sensitivity of the CGIA method was 100% and 97%, respectively, and the consistency rate between these two methods was 99.3%. These results confirmed that the CGIA method based on rCatL1D protein could be a promising approach for rapid diagnosis of sheep fasciolosis because of its high sensitivity and specificity.

Immunodiagnosis of Human Fascioliasis: An Update of Concepts and Performances of the Serological Assays

Human Fascioliasis (HF) is a foodborne neglected parasitic disease caused by Fasciola hepatica and Fasciola gigantica. New epidemiological data suggest that the endemic areas of the disease are expanding and HF is being reported from areas where it was previously not observed. Diagnosis of HF is challenging. Performances of parasitological approaches, based on the detection of parasite's egg in the stool, are not satisfactory. Currently serological methods for the diagnosis of HF are mainly based on detection of anti-Fasciola antibodies in serum. Although, there have been some improvement in the development of immunological diagnostic tests for the diagnosis of HF, yet these tests suffer from insufficiency in sensitivity or/and specificity. Detection of antigens, rather than antibodies, seems to be a suitable approach in the diagnosis of HF. Antigen can be detected in sera or stool of the fascioliasis patients. Circulating antigen in serum disappears within a short time and most of the circulating antigens are in immune complex forms which are not freely available to be detected. Therefore, antigenemia might not be an appropriate method for the diagnosis of HF. Detection of antigen in stool (coproantigens) seems to be a suitable alternative method for the diagnosis of HF. Recent data provided convincing evidence that detection of coproantigen improved and simplified the diagnosis of HF. The present review highlights the new achievements in designing and improvement of diagnostic approaches for the immunodiagnosis of HF. Moreover, current status of the available immunodiagnostic techniques for the diagnosis of HF, their strengths and weaknesses has been discussed.