Development of cathepsin-L cysteine proteinase based Dot-enzyme-linked immunosorbent assay for the diagnosis of Fasciola gigantica infection in buffaloes

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.

Dot-ELISA based on recombinant Hypodermin C of Przhevalskiana silenus for field diagnosis of goat warble fly infestation

Goat warble fly infestation (GWFI) is an economically important myiasis caused by larvae of Przhevalskiana silenus (Diptera, Oestridae), prevalent in countries of the Mediterranean Basin and Indian subcontinent. GWFI is characterized by the presence of subcutaneous warbles at the lumbar and sacral region of dorsum in the infested animal. The early larval instars (L1 and L2) remain inaccessible to physical detection due to their small size and subcutaneous presence thus causing hindrance in the diagnosis. The objective of present study was to develop a field applicable early diagnostic intervention for GWFI monitoring and prophylactic management for effective control of the disease. Recombinant Hypodermin C (rHyC) antigen of P. silenus was expressed in Escherichia coli. The purified protein was used for optimizing dot-ELISA in a checkerboard titration using goat warble fly infested serum as known positive. The optimized assay was further tested for lower temperature (18°C) and incubation time (30 min). The optimized assay was assessed for inter-rater reliability and field samples. The optimized conditions require 188 ng of protein/dot, 1:800 dilution of serum sample, 1:4000 dilution of anti-goat IgG conjugate and 5% skim milk powder in phosphate buffer saline as blocking buffer. The assay was found to have a diagnostic sensitivity and specificity of 97.3% and 95.8%, respectively. The inter-rater reliability of dot ELISA with rHyC indirect ELISA was found to be almost perfect with a Cohen's kappa index of 0.973. Further testing at ambient temperature (18°C) and shorter incubation steps (30 min) supported suitability of the assay for field diagnosis of GWFI. The present study provides the first report of a sensitive and specific dot-ELISA for early diagnosis of GWFI which is rapid and cost effective. The test may provide an effective field applicable tool for sustainable control of GWFI.

Fasciolosis in India: An overview

Fasciolosis in ruminants is a relentless constraint in the livestock industry across the world. Immuno-prophylactic vaccines against fasciolosis may not come up in near future, rendering the control of this scourge with chemotherapy and snail population control. With the alarming threats of anti-fasciolid drug resistance reported from certain parts of the world; the control of fasciolosis should be directed towards the development of rapid and reliable diagnostic tools to execute the specific and discrete treatment. Understanding the epidemiology of Fasciola, its genomics and proteomics, host-parasite interplay, and advances in drug design research is vital for improving animal health that would ultimately succour to meet the ever-increasing demand for food. Due to possible differences in immune response depending on the species of the host and parasite, immuno-prophylactic studies in India should aim at achieving protective efficacy in buffalo against F. gigantica as workers from other countries concentrate primarily on vaccination of cattle and sheep against F. hepatica. This manuscript focused on the research that has been carried out in India for understanding the epidemiology, genetic diversity, immuno-diagnosis, and possible control measure in terms of immuno-prophylaxis and drug designing against tropical fasciolosis caused by Fasciola gigantica.

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.

Diagnostic potential of low molecular weight excretory secretory proteins of Paramphistomum epiclitum for caprine amphistomosis

In the present study, the 75% alcoholic fractionation of excretory-secretory (ES) antigen isolated from 200 to 300 live P. epiclitum was assessed for its diagnostic potential for the detection of caprine amphistomosis by using antibody detection enzyme immunoassay. Prior to enzyme immunoassay, 75% alcoholic fractionation of excretory-secretory (ES) antigen was subjected to SDS- PAGE and western blot analysis for the presence of immunoreactive polypeptides. SDS-PAGE analysis of ES antigen resolved a total 7 polypeptides bands of size 56, 27, 25, 22.5, 12, 11 and 10 kDa. Western blot analysis revealed only two immunoreactive polypeptides (11 kDa and 12 kDa) when polypeptides resolved in SDS-PAGE were probed with known positive pooled serum. None of the polypeptides showed reactions with pooled known negative serum. The working dilutions of antigen, sera and conjugates were determined by checkerboard titration for employing ELISA and cut-off O.D. was calculated 0.616 by using the mean absorbance value of 11 negative kid sera. The sensitivity and specificity of ELISA was found to be 100% and 86.76%, respectively. As per kappa value estimation, the strength of agreement was found to be good. Antibodies to 75% alcoholic fractionation of ES antigen was detected in 20% goats (n = 160) of either sex, although faecal examination detected 10.6% goats to be infected with amphistomosis. The study confirmed that 75% alcoholic fractionation of ES antigen of P. epiclitum based ELISA had good value for serodiagnosis of caprine amphistomosis.

Standardization of recombinant Ancylostoma caninum cysteine protease 2 (rAcCP2) based indirect ELISA for serodiagnosis of hookworm infection in dogs

Diagnosis of hookworm infection in dogs during pre-patentency or in pregnant bitches harbouring encysted larvae in tissues can be achieved by employing serological tests using proteins derived from somatic or excretorysecretory products of adult or larvae of Ancylostoma caninum. In the present study, cathepsin-B protease (AcCP2) of A. caninum, which helps in development of parasitism and nutrient digestion, was used to develop an indirect ELISA for detection of specific antibodies to A. caninum in dogs. The rAcCP2 (approx. 59.0 kDa) was cloned, expressed and purified under denaturing conditions. Serum samples of 20 known A. caninum positive and 15 known negative dogs were used for the standardization of indirect ELISA. The sensitivity and specificity of the assay was determined by using sera samples from 123 dogs (48 positive for A. caninum eggs in faeces and 75 faecal negative). Out of the 48 A. caninum faecal positive sera, 46 were tested positive (OD > 0.306) by indirect ELISA; whereas, 14 out of 75 faecal negative samples were also tested positive (OD > 0.306) by indirect ELISA. Based on the results, the sensitivity and specificity of rAcCP2 based indirect ELISA was calculated to be 95.8% and 84.3%, respectively. No cross-reactions were observed with serum from dogs naturally infected with B. canis vogeli, B. gibsoni, E. canis, Dirofilaria immitis and Toxocara canis. The results of the present study indicate that indirect ELISA with rAcCP2 protein might be appropriate in large scale epidemiological screening and for serological diagnosis of A. caninum infection in dogs.

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

Fascioliasis is a global parasitic disease that affects domestic animals and causes considerable economic losses in the process of domestic animal breeding in endemic regions. The cause of the disease involves a liver trematode of the genus Fasciola, which secretes materials into a host's body (mainly proteins) in order to protect it from the host's immune system. These materials can be involved in the migration, growth, and nutrition of the parasite. Among the expressive proteins of Fasciola, proteases have been introduced as the appropriate targets for diagnosis, treatment, and vaccination against parasites. Cathepsin L (CL) is a member of cysteine proteases; it is widely expressed in the Fasciola species. The aim of this study was to evaluate two synthetic peptides from F. gigantica CL1 for improving serological diagnosis of the Fasciola infection. Therefore, the potential diagnostic value of the surface epitopes of CL1 was assessed using ELISA. In the current study, bioinformatics tools were applied to select two appropriate epitopes of Fasciola Cathepsin L1 as synthetic antigens. Their diagnostic values were evaluated by two methods of indirect ELISA and dot blot analysis. The findings revealed that the first peptide at a dilution ratio of 1:400 and the second peptide at a dilution ratio of 1:100 had the best results and the best concentration of antigens was introduced at 4 μg/ml. Moreover, 191 sera samples were analyzed by both peptides by using the ELISA method, including fascioliasis sera, other parasitic sera and negative sera. The sensitivity of the peptides 1-ELISA and peptide 2-ELISA for the diagnosis of the various cases was 100%. The specificity of the first peptide was 87.3% and its efficacy was determined to be 93.65%. The specificity and the efficacy of the second peptide were 79% and 89.5%, respectively. The positive predictive values of the first and second peptides were obtained to be 86.27% and 79.27% respectively, and the negative predictive values of both peptides was calculated as 100%. In conclusion, the results of this study indicated that the peptide 1 from CL1 may be used as an appropriate antigen for the diagnosis of fascioliasis if the findings are backed up by using other serodiagnostic methods for checking serological cross-reactivity linked to other parasites.

Seroprevalence of Fasciolagigantica infection in bovines using cysteine proteinase dot enzyme-linked immunosorbent assay

Aim:

The objective of the present study was to know the seroprevalence status of Fasciola gigantica infection in cattle and buffaloes using cysteine proteinase (CP) antigen in dot enzyme-linked immunosorbent assay (ELISA) format under field conditions.

Materials and Methods:

As per the standard protocol, the sera were collected from the blood of 112 cattle and 38 buffaloes of coastal areas of Navsari district, South Gujarat, India. The indirect ELISA was performed on the strip of nitrocellulose paper blotted with 1 µl of CP antigen, to detect F. gigantica seropositive animals.

Results:

The native CP of F. gigantica revealed a single visible band on 10% sodium dodecyl sulfate-polyacrylamide gel electrophoresis. There was no any noted cross-reaction between the selected antigen and sera of Gastrothylax crumenifer-infected animals in ELISA. Out of 150 screened bovines, the sera of 47 (31.33%) were found to be reactive in dot-ELISA, with a prevalence rate of 31.25% and 31.58% in cattle and buffaloes, respectively. The seropositive bovines with heavy, moderate, and light level of infection were 44.68%, 34.04%, and 21.28%, respectively (p<0.05 between heavy and light; p>0.05 between moderate and heavy or light). The share of F. gigantica seropositive and negative animals was 31% and 69%, respectively. The optical density at 450 nm of pooled sera of seropositive bovines with heavy, moderate, and light reactivity in plate-ELISA was significantly higher with field or reference ­negative sera.

Conclusion:

The CP-based dot-ELISA can be useful for field veterinarians for quick and timely isolation of the animals requiring urgent flukicide therapy.

Molecular and immunological characterization of cathepsin L-like cysteine protease of Paragonimus pseudoheterotremus

Cathepsin L is a cysteine protease belonging to the papain family. In parasitic trematodes, cathepsin L plays essential roles in parasite survival and host-parasite interactions. In this study, cathepsin L of the lung fluke Paragonimus pseudoheterotremus (PpsCatL) was identified and its molecular biological and immunological features characterized. A sequence analysis of PpsCatL showed that the gene encodes a 325-amino-acid protein that is most similar to P. westermani cathepsin L. The in silico three-dimensional structure suggests that PpsCatL is a pro-enzyme that becomes active when the propeptide is cleaved. A recombinant pro-PpsCatL lacking the signal peptide (rPpsCatL), with a molecular weight of 35 kDa, was expressed in E. coli and reacted with P. pseudoheterotremus-infected rat sera. The native protein was detected in crude worm antigens and excretory-secretory products and was localized in the cecum and in the lamellae along the intestinal tract of the adult parasite. Enzymatic activity of rPpsCatL showed that the protein could cleave the fluorogenic substrate Z-Phe-Arg-AMC after autocatalysis but was inhibited with E64. The immunodiagnostic potential of the recombinant protein was evaluated with an enzyme-linked immunosorbent assay (ELISA) and suggested that rPpsCatL can detect paragonimiasis with high sensitivity and specificity (100 and 95.6 %, respectively). This supports the further development of an rPpsCatL-ELISA as an immunodiagnostic tool.

Serological and coprological analyses for the diagnosis of Fasciolagigantica infections in bovine hosts from Sargodha, Pakistan

A serological and coprological survey of fasciolosis was conducted in bovine hosts from the Sargodha district, Pakistan using excretory–secretory (ES) antigens of Fasciola gigantica from cattle and buffaloes. Livers, faecal and blood samples of 146 cattle and 184 buffaloes were collected from slaughterhouses and examined for the presence of any Fasciola in bile ducts and ova in faeces. Serum was separated. ES antigens were prepared by incubating adult Fasciola in phosphate-buffered saline for 6–8 h and then filtering using a 0.22-μm syringe filter. Checkerboard titration was performed and optimum concentrations of antigen and serum were determined. Sero-prevalence was found to be 50.00 and 38.35% in buffalo and cattle, respectively. Using liver examination as the gold standard, enzyme-linked immunosorbent assay (ELISA) sensitivity was found to be 100% in both buffalo and cattle as compared with that of coprological examination in buffalo (61.79%) and cattle (54.54%). This indigenous ELISA was also highly specific, with values of 96.84 and 98.90% in buffalo and cattle, respectively. Positive predictive values were calculated as 96.74 and 98.21% in buffalo and cattle, respectively, while negative predictive values were 100%. For the validation of indigenous ELISA in field surveys, faecal and blood samples were collected from six sub-districts (tehsils) in the district of Sargodha. Sera were screened for the presence of anti-fasciola antibodies using both the indigenous and commercial ELISA kits. While both kits were equally sensitive, the indigenous ELISA was found to be more specific. The highest prevalence of fasciolosis was found in December, as ascertained using both serological and coprological examination. Significant differences were found in prevalences of fasciolosis in different sub-districts and age groups, together with feeding and watering systems.

Comparison between in-house indirect ELISA and Dot-ELISA for the diagnosis of Fasciola gigantica in cattle

This survey was done to investigate the efficacy of the in-house indirect ELISA (iELISA) and Dot-ELISA methods Prepared from excretion-secretory (ES Ag) and Crude (Cr Ag) antigens of Fasciola for sero-diagnosis of Fasciola gigantica in cattle. The liver specimens of slaughtered cattle were collected and their liver examined macroscopically and microscopically for infestation to fasciolosis. Sera from two groups of cattle, one infected with fasciolosis (n = 60) and the other non-infected with fasciolosis (n = 60), were used in the iELISA and Dot-ELISA test; grouping based on histopathology results. Except specificity, other parameters such as, sensitivity, accuracy, positive and negative predictive values of both Dot-ELISA and iELISA done with ES Ag were better than those of tests performed with Cr Ag. Interestingly, the reliability of two methods was very good similar to one another.

Expression of the Tpanxb1 gene from Taenia pisiformis and its potential diagnostic value by dot-ELISA

Cysticercosis, caused by the larvae of Taenia pisiformis, is a common disease in rabbits that results in economic losses. To date, there has been limited information available on the early detection of infection by this parasite. This study describes a dot-ELISA method based on an autologous antigen annexin B1 (Tpanxb1). Its potential for serodiagnosis of rabbit cysticercosis was also evaluated. Western blot analysis revealed that the recombinant Tpanxb1 (rTpanxb1) protein could be specifically recognized by rabbit anti-sera. In serum trials, the antibodies could be detected by dot-ELISA using rTpanxb1 at 14 days post-infection. The positive response was present for up to 49 days post-infection. Based on the necropsy results of 169 rabbit samples, the relative sensitivity and specificity of the dot-ELISA were 94.55% and 92.86%, respectively. This study provides a foundation for studying the immunological function of annexin and its application to control Taenia cestodes.

Expression and immunolocalisation of TpFABP as a candidate antigen for the serodiagnosis of rabbit Taenia pisiformis cysticercosis

The larval stage of Taenia pisiformis, also known as Cysticercus pisiformis, is the causative agent of cysticercosis and the cause of severe health problems in rabbits that negatively impacts on husbandry production. To date, there is no fast detection method to identify early infections in rabbits. In the present study, a new dot-ELISA-based on an endogenous antigen fatty acid-binding protein (FABP) was developed for the detection of cysticercosis, and its potential was then evaluated using test serum samples. Immunolocalisation showed that T. pisiformis FABP (TpFABP) localised to the parenchyma of the bladder wall of the cysticercus and perinuclear cytoplasm of parenchyma of the adult parasite. After cloning and expression, recombinant TpFABP (rTpFABP) protein was used for serodiagnosis of T. pisiformis infection in rabbits by dot-ELISA. The antibody was detected 14 days post-infection in rabbits experimentally infected with T. pisiformis. Based on the necropsy results, the sensitivity and specificity of 169 serum samples tested by rTpFABP dot-ELISA were found to be 98.2% (54/55) and 92.1% (105/114), respectively. These data suggest that the dot-ELISA developed in this study has potential for detection of T. pisiformis infection in rabbits.

Characterisation and analysis of thioredoxin peroxidase as a potential antigen for the serodiagnosis of sarcoptic mange in rabbits by dot-ELISA

BACKGROUND

Scabies caused by Sarcoptes scabiei is a widespread but a neglected tropical zoonosis. In this study, we characterised a S. scabiei thioredoxin peroxidase (SsTPx) and evaluated a recombinant SsTPx as a diagnostic antigen in rabbits.

METHODS

The open reading frame of the gene encoding SsTPx-2 was amplified and the recombinant protein was expressed in Escherichia coli cells and purified. SsTPx was localized in mite tissue by immunolocalisation using the purified recombinant protein. Serodiagnosis assays were carried out in 203 New Zealand White rabbit serum samples by dot-ELISA.

RESULT

The open reading frame (489 bp) of the gene encodes an 18.11 kDa protein, which showed highly homology to that of Psoroptes cuniculi (98.77% identity) and belongs to the 2-Cys family of peroxiredoxins. SsTPx was mainly distributed in muscle tissues of mites, integument of the epidermis and the anterior end of S. scabiei. Although SsTPx cross-reactivity with psoroptic mites was observed, the SsTPx dot-ELISA showed excellent diagnostic ability, with 95.3% sensitivity and 93.8% specificity in mange-infected and uninfected groups.

CONCLUSIONS

This study showed that the purified SsTPx is a highly sensitive antigen for the diagnosis of mange infection by dot-ELISA. This technique is a rapid and convenient method that can be used worldwide for the clinical diagnosis of sarcoptic mange in rabbits, and is especially useful in developing regions.