Design and synthesis of a new peptide derived from Fasciola gigantica cathepsin L1 with potential application in serodiagnosis of fascioliasis

Advances in diagnostic approaches to Fasciola infection in animals and humans: An overviews

Fasciolosis, caused by Fasciola hepatica and F. gigantica, is an impediment to the livestock industry’s expansion and has a massively negative socio-economic impact due to its widespread prevalence in livestock. It is a waterborne zoonosis affecting human populations in the countries where rural economies are associated with livestock rearing. Conventional diagnosis of Fasciola infection is done by detecting parasite eggs in the faeces of infected animals or by immunological methods. Accurate and quick immunodiagnosis of Fasciola infection in animals and humans is based on the detection of antibodies and specific antigens expressed in the prepatent stage of the parasite. Both molecular and serodiagnostic tests developed thus far have enhanced the reliability of Fasciola diagnosis in both man and animals but are not widely available in resource-poor nations. A pen-side diagnostic test based on a lateral flow assay or a DNA test like loop-mediated isothermal amplification (LAMP) would be simple, fast, and cost-effective, enabling clinicians to treat animals in a targeted manner and avoid the development of drug resistance to the limited flukicides. This review focuses on the recent advances made in the diagnosis of this parasite infection in animals and humans.

High relatedness of bioinformatic data and realistic experimental works on the potentials of Fasciola hepatica and F. gigantica cathepsin L1 as a diagnostic and vaccine antigen

Introduction

Fascioliasis is a parasitic foodborne disease caused by the liver flukes, Fasciola hepatica and F. gigantica. Such parasites cause serious illness in numerous domestic animals and also in humans. Following infection, the parasite secretes a variety of molecules that immediately interact with the host immunity to establish successful infection. These molecules include cathepsin L peptidase 1 (CatL1); the highly investigated diagnostic and vaccine antigens using various animal models. However, a few studies have analyzed the potentials of FhCatL1 as a diagnostic or vaccine antigen using bioinformatic tools and much less for FgCatL1. The present study provides inclusive and exclusive information on the physico-chemical, antigenic and immunogenic properties of F. hepatica cathepsin L1 (FhCatL1) protein using multiple bioinformatic analysis tools and several online web servers. Also, the validation of our employed available online servers was conducted against a huge collection of previously published studies focusing on the properties of FhCatL1as a diagnostic and vaccine antigen.

Methods

For this purpose, the secondary, tertiary, and quaternary structure of FhCatL1 protein were also predicted and analyzed using the SWISS-MODEL server. Validation of the modeled structures was performed by Ramachandran plots. The antigenic epitopes of the protein were predicted by IEDB server.

Results and discussion

Our findings revealed the low similarity of FhCatL1 with mammalian CatL1, lacking signal peptides or transmembrane domain, and the presence of 33 phosphorylation sites. Also, the containment of FhCatL1 for many topological, physico-chemical, immunological properties that favored its function of solubility and interaction with the immune components were reported. In addition, the earlier worldwide reports documented the high efficacy of FhCatL1 as a diagnostic and vaccine antigen in different animals. Altogether, FhCatL1 is considered an excellent candidate for using in commercialized diagnostic assays or vaccine products against fascioliasis in different animal species. Our assessment also included FgCatL1 and reported very similar findings and outputs to those of FhCatL1.

Fasciola hepatica Cathepsin L Zymogens: Immuno-Proteomic Evidence for Highly Immunogenic Zymogen-Specific Conformational Epitopes to Support Diagnostics Development

Fasciola hepatica, the common liver fluke and causative agent of zoonotic fasciolosis, impacts on food security with global economic losses of over $3.2 BN per annum through deterioration of animal health, productivity losses, and livestock death and is also re-emerging as a foodborne human disease. Cathepsin proteases present a major vaccine and diagnostic target of the F. hepatica excretory/secretory (ES) proteome, but utilization in diagnostics of the highly antigenic zymogen stage of these proteins is surprisingly yet to be fully exploited. Following an immuno-proteomic investigation of recombinant and native procathepsins ((r)FhpCL1), including mass spectrometric analyses (DOI: 10.6019/PXD030293), and using counterpart polyclonal antibodies to a recombinant mutant procathepsin L (anti-rFhΔpCL1), we have confirmed recombinant and native cathepsin L zymogens contain conserved, highly antigenic epitopes that are conformationally dependent. Furthermore, using diagnostic platforms, including pilot serum and fecal antigen capture enzyme-linked immunosorbent assay (ELISA) tests, the diagnostic capacities of cathepsin L zymogens were assessed and validated, offering promising efficacy as markers of infection and for monitoring treatment efficacy.

Serodiagnosis of Fasciola gigantica Infection in Buffaloes with Native Cathepsin-L Proteases and Recombinant Cathepsin L1-D

AIM

Serodiagnosis of Fasciola gigantica natural infection in buffaloes with recombinant cathepsin L1-D and native cathepsin-L protease antigens.

METHODS

The recombinant cat L1-D antigen was expressed in prokaryotic expression system and native cathepsin-L proteases were purified by alcoholic fractionation from adult F. gigantica flukes. Buffaloes (n  = 325) were screened for anti-Fasciola antibodies with the above antigens in immunoglobulin-G-enzyme linked immunosorbent assay (IgG-ELISA).

RESULTS

The recombinant cat L1-D antigen showed positive reactivity with 101/122 necropsy positive animals but 21/122 necropsy confirmed positive animals were negative in this ELISA (sensitivity 82.8%). However, 30/203 (14.8%) necropsy negative animals for Fasciola were seropositive with specificity of 85.2%. With native cat-L protease, 104/122 necropsy confirmed positive animals were ELISA positive but 18/122 necropsy positive animals were seronegative, thereby depicting the sensitivity of 85.2%. But ELISA with this antigen showed 27/203 (13.3%) necropsy negative animals as positive (specificity 86.7%).

CONCLUSIONS

Comparative evaluation of both the antigens showed that they are suitable for serodiagnosis of F. gigantica infection in buffalo herds.

Evaluation of a Commercial Enzyme-Linked Immunosorbent Assay Kit and In-House Fasciola gigantica Cysteine Proteinases-Based Enzyme-Linked Immunosorbent Assays for Diagnosis of Human Fascioliasis

Fascioliasis, caused by Fasciola hepatica and Fasciola gigantica infection, is a major food-borne trematodiasis in many places of the world, with the central region of Vietnam being reported as a highly endemic area. Stool examination for Fasciola eggs is not a sensitive method, and immunodiagnostic methods are preferable. We investigated various enzyme-linked immunosorbent assays (ELISAs) to evaluate their efficacy for fascioliasis diagnosis. Test sera used are primarily screened using an ELISA kit produced in Vietnam (VN kit; Viet Sinh Chemical Producing & Trading Co. Ltd., Ho Chi Minh City, Vietnam): Seropositive individuals having symptoms compatible with fascioliasis were regarded as clinically diagnosed fascioliasis cases. A commercial Fasciola IgG ELISA kit from Diagnostic Automation/Cortez Diagnostics, Inc. (USA kit; Woodland Hills, CA), which has been commonly used in Vietnam, was assessed and compared with in-house ELISA systems, including a cystatin-capture (CC) ELISA using crude worm extract (CWE) and an indirect ELISA using a synthetic peptide Ac-TPTCHWECQVGYNKTYDEE-NHMe designed from the F. gigantica cathepsin B (FgCB5) molecule. The USA kit was suitable for routine diagnosis after recalibration of the manufacturer's suggested cutoff point. Cystatin-capture ELISA with CWE provided good sensitivity and specificity with perfect agreement to the results of the USA kit. In dot-blot ELISA, recombinant FgCB5 reacted more strongly with human antisera than did other F. gigantica antigens tested. Enzyme-linked immunosorbent assay using the synthetic peptide fragment of the FgCB5 exhibited nearly 80% sensitivity and specificity, but the test results showed low agreement with CC-ELISA or the USA kit. In conclusion, the commercially available Fasciola IgG ELISA kit from the United States and the in-house CC ELISA using CWE are suitable for practical diagnosis for fascioliasis.