Scholarly article on topic 'Diagnosis of Fasciola infection by SDS–PAGE eluted excretory secretory (ES) protein fractions using dot-ELISA'

Diagnosis of Fasciola infection by SDS–PAGE eluted excretory secretory (ES) protein fractions using dot-ELISA Academic research paper on "Veterinary science"

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Abstract of research paper on Veterinary science, author of scientific article — M.A. Sabry, E.S. Taher, N. Farag Allah, A.M. Mahgoub

Abstract Fascioliasis is now recognized as an emerging zoonotic disease in Egypt. Diagnosis in suspected patients still needs some degree of accuracy. In the present study, three Fasciola gigantica execratory secretory (ES) protein bands of molecular weight (MW) ranging from 14 to 20kDa, 25 to 32kDa and 45 to 65kDa were eluted after fractionation of the parasite antigen using SDS–PAGE. The extracted kDa protein bands were concentrated and evaluated in diagnosis of Fasciola infection. Moreover the level of their cross reaction with other parasitic infections in infected and suspected patients of known parasite eggs/gram stool was evaluated using the dot-ELISA technique. Protein bands in the range of 14–20kDa and that of 25–32kDa were markedly specific and sensitive in diagnosis of different levels of anti-Fasciola antibodies (Ab) in sera of infected cases. These two groups of bands were able to exclude cross-reaction between anti-Fasciola Ab and other parasites recorded in stool of selected patients suffering from Schistosoma mansoni, Ascaris, and Giardia, either in single or mixed conditions with Fasciola eggs. While that of 45–65kDa appeared less specific than the other previously mentioned bands. Protein bands in the range of 25–32kDa appeared more sensitive than the other protein bands in detection of anti-Fasciola Ab at higher serum dilutions. The Dot-ELISA technique was proved to be more economic and easy in application. The dotted very small amount of antigens can be stored in a freezer and used at request in diagnosis of large numbers of samples.

Academic research paper on topic "Diagnosis of Fasciola infection by SDS–PAGE eluted excretory secretory (ES) protein fractions using dot-ELISA"

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Cairo University International Journal of Veterinary Science and Medicine

www.vet.cu.edu.eg www.sciencedirect.com

Full Length Article

Diagnosis of Fasciola infection by SDS-PAGE q^m

eluted excretory secretory (ES) protein fractions using dot-ELISA

M.A. Sabry a'*, E.S. Taher b, N. Farag Allah b, A.M. Mahgoub c

a Department of Zoonoses, Faculty of Veterinary Medicine, Egypt b Department of Parasitology, Research Institute of Ophthalmology, Egypt c Department of Parasitology, Faculty of Medicine, Cairo University, Egypt

Received 6 September 2014; revised 18 October 2014; accepted 18 October 2014 Available online 2 December 2014

KEYWORDS

F. gigantica;

Human-antigenic fraction;

Dot-ELISA;

Egypt;

Abstract Fascioliasis is now recognized as an emerging zoonotic disease in Egypt. Diagnosis in suspected patients still needs some degree of accuracy. In the present study, three Fasciola gigantica execratory secretory (ES) protein bands of molecular weight (MW) ranging from 14 to 20 kDa, 25 to 32 kDa and 45 to 65 kDa were eluted after fractionation of the parasite antigen using SDS-PAGE. The extracted kDa protein bands were concentrated and evaluated in diagnosis of Fasciola infection. Moreover the level of their cross reaction with other parasitic infections in infected and suspected patients of known parasite eggs/gram stool was evaluated using the dot-ELISA technique. Protein bands in the range of 14-20 kDa and that of 25-32 kDa were markedly specific and sensitive in diagnosis of different levels of anti-Fasciola antibodies (Ab) in sera of infected cases. These two groups of bands were able to exclude cross-reaction between anti-Fasciola Ab and other parasites recorded in stool of selected patients suffering from Schistosoma mansoni, Ascaris, and Giardia, either in single or mixed conditions with Fasciola eggs. While that of 45-65 kDa appeared less specific than the other previously mentioned bands. Protein bands in the range of 25-32 kDa appeared more sensitive than the other protein bands in detection of anti-Fasciola Ab at higher serum dilutions. The Dot-ELISA technique was proved to be more economic and easy in application. The dotted very small amount of antigens can be stored in a freezer and used at request in diagnosis of large numbers of samples.

© 2014 Production and hosting by Elsevier B.V. on behalf of Faculty of Veterinary Medicine, Cairo University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/

licenses/by-nc-nd/3.0/).

1. Introduction

* Corresponding author.

Peer review under responsibility of Faculty of Veterinary Medicine, Cairo University.

Several previous studies were done to induce early accurate diagnosis of Fasciola infection with special interest to exclusion of the cross reacted parasites using different serological techniques. In these studies, different Fasciola antigens (Ag) were

http://dx.doi.Org/10.1016/j.ijvsm.2014.10.002

2314-4599 © 2014 Production and hosting by Elsevier B.V. on behalf of Faculty of Veterinary Medicine, Cairo University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

used including crude worm Ag [1], excretory secretory (ES) Ag [2] and egg antigens [3]. Each author clarified some advantages and disadvantages for his technique.

It was commonly understood that the ELISA technique is a sensitive and simple method for semi-quantitative determination of antibodies [4]. Specificity of ELISA in exclusion of cross reacted parasites depended mainly on the degree of specificity and purity of the used Ag as well as history of the tested sera [2].

More rapid, economic, direct and visually read, improved ELISA technique for the diagnosis of parasitic diseases as mic-roenzyme-linked immunosorbent assay (dot-ELISA) was described by Rokni et al. [5]. This technique for diagnosis of bovine fascioliasis was used by Latchumikanthan et al. [6]. They cleared that nano-gram quantities of parasite antigen dotted onto a very small piece of nitrocellulose membranes were considered enough to obtain a marked direct and accurate diagnosis for the parasite directly.

Fractionated Fasciola hepatica ES Ag using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was done as described by Morphew et al. [7] and the selected protein bands of 16, 26-28, 35-36 and 56-58 kDa as specific bands were used for the diagnosis of Fasciola infection in sheep with different degrees of specificity. At the same time Kamel et al. [8] determined that the most specific protein band in F. hepatica ES Ag is that of 14-38 kDa band and the most specific one is that of 27 kDa.

In the present study, Fasciola gigantica ES Ag was fractionated using SDS-PAGE. Gel pieces containing the most common Fasciola protein bands were cut out; their antigenic contents were eluted and concentrated. The value of each fraction in diagnosis of Fasciola infection and exclusion of cross reaction with other infections was evaluated using the dot-ELISA technique versus sera collected from cases of known parasitic infection history as well as rabbit hyperimmune sera and negative sera as a control.

2. Materials and methods

2.1. Antigen preparation

2.1.1. F. gigantica excretory secretory antigen (E/S Ag) F. gigantica ES Ag was prepared from living flukes collected from freshly condemned buffalo's livers according to Rivera Marrero et al. [9]. The clean active worms were incubated (40 worms per 100 ml) for 3 h at 37 0C in PBS (7.4 pH). The supernatant was separated after centrifugation at 5000 rpm at 4 0C for 1 h. Their protein content was increased by removal of excess PBS using poly ethylene glycol in molecular porous membrane tubing 6-8 MW cutoff (Spectrum Medical Inc., Los Angeles, CA 900060). After determination of their protein content by the method of Lowry et al. [10], the antigen was allocated into 1 ml vial and stored at —20 0C until use.

2.2. Production and separation of specific selected F. gigantica protein bands

2.2.1. Fractionation of F. gigantica E/S Ag using SDS-PAGE F. gigantica ES Ag was fractionated using SDS-PAGE according to Laemmli et al. [11] in 10% polyacrylamide gel slabs in Tris-glycine buffer, pH 8.3 (Sigma Chemical Co.). Low and high MW standards were employed (Sigma SDS-100B). Gel

strips containing the standard and part of F. gigantica fractionated Ag were cut out, fixed and stained with Coomassie-blue stain according to the method of Tsai et al. [12]. These strips were retained back to its original position for determination of the site of the selected protein bands.

2.2.2. Isolation of selected protein fraction from SDS-PAGE by electro elution

Continuous 10% gels (1.5 mm thickness) were isolated with 1 mg/ml of F. gigantica ES proteins. Individual slots in the same gel were used to electrophorese the molecular weight (MW) standards. Once the gel ran its full length, strips with the MW standards were cut and stained with Coomassie blue to determine the region where the antigens of interest would be according to the associated approximate MW. As shown in Fig. 1, three zones in the gel at the levels of 45-65 kDa (A), 25-32 kDa (B) and 14-20 kDa (C), were cut out horizontally across the whole gel. Each gel strip was transferred separately to elution tube membrane 6-8 MW cut off (Spectrum Medical Inc., Los Angeles, CA 900060). The tube was filled with PBS (pH 7.4) and kept in Bio-Rad elution unit at 10 V, 100 ml overnight at 4 0C. The gel material was removed and the volume was reduced using poly ethylene glycol in molecular porous membrane tubing 6-8 MW cut off according to Katrak et al.

[13]. The protein content of the eluted concentrated materials was determined and kept in 1 ml vial at —70 0C till use.

2.3. Other antigens used for testing serum specificity

In order to test the specificity of the target antigens, the same sera were tested versus some selected antigens including hydatid cyst fluid antigen (HCFAg), S. mansoni crude Ag and Toxocara canis crude Ag. HCFAg was prepared from fertile HC extracted from freshly slaughtered camel lungs (slaughtered at Cairo abattoir) according to Osman et al.

[14]. The fluid was clarified by centrifugation at 5000 rpm for 15 min at 4 0C, dialyzed against 5 mM Tris-HCl (pH 7.4) for 48 h at 4 0C, after determination of their protein content by the method of Lowry et al. [10]. The antigen was allocated into

Figure 1 Gel electrophoresis showing the three selected protein bands before elution. A level at 45-65 kDa, B level at 25-32 kDa, C level at 14-20 kDa, MW. MW = Low M. W. protein standard; E.S. = fractionated F. gigantica excretory secretory antigen.

1 ml vial and stored at —20 0C until use. T. canis crude antigen was extracted from the anterior part of the worms extracted from the intestine of naturally infected dogs following the protocol briefly described by Sabry et al. [15]. S. mansoni whole worm crude antigen was prepared from lyophilized worms obtained from the Schistosoma Biological Materials Supply Program, Theodore Bilharz Research Institute, Giza, Egypt, according to Joseph et al. [16]. The protein content was evaluated and stored as before.

2.4. Dot-ELISA technique

The technique described by Shaheen et al. [17], one microliter (1 il) of the antigen (1.0 mg protein/ml) in PBS-T (pH 7.4) was dotted on 6 mm diameter nitrocellulose membrane disks, after drying at 56 0C for 10-15 min, it placed into flat bottom of polystyrene 96 wells ELISA plate. Non-specific binding sites were blocked using 3% BSA-PBS-T. After 3 time wash using PBS-T, disks were used immediately or stored at —20 0C. For testing, 20 il of diluted sera was applied on top of the dotted antigens in the wells in duplicates. The plates were incubated at room temperature for 1 h. After 3 time wash, 20 il of horseradish peroxidase conjugated goat anti-human IgG (Sigma) and goat anti-rabbit IgG (Sigma) diluted at 1:1000, was added and incubated for 30 min at room temperature. After 3-5 time washing, 50 il of freshly prepared 4-chloro 1-naphthol 340 ig/ml substrate buffer with 0.03% hydrogen peroxide solution was added. After color development, (within 15 min) the disks were washed and air-dried. The intensity of the blue-purple color was judged by the naked eye and evaluated in comparison with the reference control and tested sera at 1:100 serum dilutions. Sensitivity was calculated as the number of true positive/(True positive + False negative), while specificity calculated as the number of true negative/(False positive + True negative) [18].

2.5. Selected serum samples

A total of 63 selected serum samples from patients of known parasitic infection history and 4 experimentally infected F. gigantica rabbits, as well as 10 healthy people and 4 control rabbits' sera were selected for evaluation of the eluted antigens.

The examined sera were assigned into 8 groups including; G-1 as 10 serum samples from patients harboring Fasciola eggs only in their stool and still positive for 3 successive examinations (1-3 egg/gram), G-2 as 20 S. mansoni infected patients. G-3 as 20 samples from virus hepatitis infected patients, G-4 as 3 serum samples from x-ray proved hydatid cyst infected patients, G-5 as 10 samples from diarrheic patients harboring Giardia trophozoites and cysts in their stool, G-6 as 4 serum samples from experimentally infected rabbits by F. gigantica 70 days post infection proved to have immature fluke in their liver (by personal communication from Sabry et al. [19]). G-7 as 10 serum samples collected from healthy non-infected people as well as 4 healthy non-infected rabbits' sera (G-8) as a control.

3. Results

Checkerboard titration before the dot-ELISA technique determined the optimum concentration for the test to be 20-30 ig of tested antigen per dot which was enough to detect specific

antibodies of the target antigen, at 1:100 serum dilutions for 1 h and 1:1000 conjugate for 30 min at room temperature. These were found to be optimum for marked differentiation between positive and negative serum samples by the naked eye.

In the present work, testing 3 protein band groups extracted from fractionated F. gigantica ES antigens at molecular weight (MW) ranges of 45-65 kDa, 25-32 kDa and 14-20 kDa (Fig 1) cleared marked specificity (100%) toward detection of anti Fasciola antibodies (Ab) in all tested sera. At the same time they did not react falsely with Ab in other selected sera of patients infected with hydatid cysts and Giardia. The fractions at the level of 14-20 kDa reacted with 2 patients infected with hepatitis C virus (HCV). The fractions at the level of 45-65 kDa reacted also versus 2 S. mansoni infected sera as well as 3 HCV infected sera using the dot-ELISA technique (Table 1).

Treatment of the same serum samples versus their original parasite antigens revealed positive reaction for 6 and 2 HCV infected sera versus S. mansoni and HFAgs reducing the specificity to 70% and 90% respectively. Moreover 2 Giardia infected sera were positive reacting versus S. mansoni Ag also (Table 1). Moreover; none of all the tested antigens produced any type of reaction when tested versus the control non-infected people and rabbit sera (Table 1).

The obtained results evidenced marked superiority in specificity of the two F. gigantica ES fractionated eluted protein band groups of MW 14-20 kDa and 25-32 kDa than that of 45-65 kDa in detection of anti-Fasciola Ab and that did not cross react with any of the tested serum samples from patients infected with other parasites.

The sensitivity of these two protein band groups (1420 kDa, and 25-32 kDa) in detection of low level of anti-Fasciola Ab by serial dilutions of the known Fasciola infected patients' and rabbits' sera is demonstrated in Table 2. Moreover; inspecting the conditions of HCV infected cases that cross reacted with these fractions at low serum dilution using dot-ELISA technique.

The results emphasized that both MW protein band groups (14-20 kDa, and 25-32 kDa) were successful in detection of anti-Fasciola Ab in different tested sera till 1:250 dilution.

By increasing the serum dilution to 1:500; the selected protein bands of MW 25-32 kDa appeared to be more sensitive (100%) than the other (14-20) kDa MW groups (80% sensitivity) in sera of Fasciola infected patients. The same phenomenon was still true using dot-ELISA test by increasing the serum dilutions to 1:1000. The eluted Ag of 25-30 kDa MW still proved high sensitivity (100%). The sensitivity of both band groups decreased to 60% and 90% for the dots carrying 14-20 kDa and 25-32 kDa respectively after treatment by the same Fasciola infected sera (Table 2).

On screening the sensitivity of these 2 MW (14-20 kDa, and 25-30 kDa) eluted protein bands versus rabbit hyperimmune sera, both groups still reacted sensitively with the 4 tested rabbits' sera till dilution of 1:500. By increasing the dilution to 1:1000 the protein bands in the range of 25-32 kDa appeared to be more sensitive (100%) than the other one (14-20 kDa) which gave lower sensitivity (only 50%) as shown in Table 2.

Two serum samples of HCV infected patients showed positive reaction versus the dots containing 14-20 kDa fractions only till 1:250 serum dilutions. This cross reaction disappeared by increasing the serum dilution to 1:500 or more. At the same time none of the tested band groups reacted versus the tested non-infected control samples (Table 2).

Table 1 Specificity of F. gigantica ES antigen in diagnosis of Fasciola infection using the dot-ELISA technique at (1:100) serum dilution.

Antigens used in dot-ELISA Number and history of tested patients serum samples

(G-1) Fasciola (G-2) S. mansoni (G-3) Hepatitis (G-4) Hydatid (G-5) Giardia (G-6) Fasciola

infected infected C infected infected infected infected

patients patients patients patients patients rabbits

(n = 10) (n = 20) (n = 20) (n = 3) (n = 10) (n = 4)

F. gigantica No. of +Ve* 10 0.0 2 0.0 0.0 4

14-20 kDa Specificity % 100 100 90 100 100 100

F. gigantica No. of +Ve* 10 0.0 0.0 0.0 0.0 4

25-32 kDa Specificity % 100 100 100 100 100 100

F. gigantica No. of +Ve* 10 2 3 0.0 0.0 4

45-65 kDa Specificity % 100 90 85 100 100 100

S. mansoni crude Ag No. of +Ve* 0.0 20 6 0.0 2 0.0

Specificity % 100 100 70 100 80 100

Hydatid fluid Ag No. of +Ve* 0.0 0.0 2 3 0.0 0.0

Specificity % 100 100 90 100 100 100

T. canis crude Ag No. of +Ve* 0.0 0.0 0.0 0.0 0.0 0.0

Specificity % 100 100 100 100 100 100

(G-7) Sera of healthy people (n = 10) and (G-8) sera of 4 non-infected rabbits. Both groups did not show any reaction versus the tested antigens No. of +Ve = number of positive samples.

Table 2 Sensitivity of F. gigantica ES antigen fractions in diagnosis of Fasciola infection using the dot-ELISA technique.

Dilution of Antigenic fractions used Fasciola Fasciola Hepatitis C Control non infected

the tested sera in dot-ELISA infected infected infected People (n = 10) Rabbits (n = 4)

patients rabbits (n = 20)

(n = 10) (n = 4)

1:100 serum dilution F. gigantica 14-20 kDa No. + Ve* 10 4 2 0 0

% 100 100 90 100 100

F. gigantica 25-32 kDa No. + Ve* 10 4 0 0 0

% 100 100 100 100 100

1:250 serum dilution F. gigantica 14-20 kDa No. + Ve* 10 4 2 0 0

% 100 100 90 100 100

F. gigantica 25-32 kDa No. + Ve* 10 4 0 0 0

% 100 100 100 100 100

1:500 serum dilution F. gigantica 14-20 kDa No. + Ve* 8 4 0 0 0

% 80 100 100 100 100

F. gigantica 25-32 kDa No. + Ve* 10 4 0 0 0

% 100 100 100 100 100

1:1000 serum dilution F. gigantica 14-20 kDa No. + Ve* 6 2 0 0 0

% 60 50 100 100 100

F. gigantica 25-32 kDa No. + Ve* 9 4 0 0 0

% 90 100 100 100 100

* No. of +Ve = number of positive samples.

For conclusion, both selected purified F. gigantica E/S fractionated eluted protein band (s) groups of MW range of 25-32 kDa and 14-20 kDa succeeded in accurate diagnosis of fascioliasis and exclusion of cross reacted antibodies of other parasites. The protein band (s) groups of MW range of 25-30 kDa appeared more sensitive than the other ones.

4. Discussion

Cross-reaction between Fasciola species and other parasites is still a questionable point creating some difficulties in the accurate evaluation of the infection status of suspected cases using some serological techniques, especially at the level of field collected polyclonal sera Rokni et al. [5].

Accuracy of these techniques was affected markedly by the degree of purity and specificity of the used antigens. More accurate results can be obtained using Enzyme Linked Immune Transfer Blot (EITB) but this technique is usually non-practical for current field application in comparison with the ELISA technique [20].

According to Valero et al. [4], ELISA is a sensitive serolog-ical test able to analyze many samples simultaneously but it needs some sophisticated equipment. The new modified dot-ELISA was more economic, more suitable for accurate diagnosis using very few amounts of reagents especially in case of small amounts of valuable purified antigen, and very convenient for field study where the results can be read visually [5].

The present study evaluated the efficacy of 3 selected groups of F. gigantica SDS-PAGE fractionated ES antigen

corresponding to MW ranges of 45-65 kDa, 25-30 kDa and 14-20 kDa in diagnosis of Fasciola infection after concentration of the eluted fractions using the dot-ELISA technique. Selection of these antigens depended on previously published work on F. hepatica [21] and [22] and F. gigantica [23] and [6] all over the world.

At the same time, crude antigens of some parasites such as S. mansoni, hydatid cysts and T. canis as well as sera of F. gigantica experimentally infected rabbits were used simultaneously in the technique as references for detection of the cross reacted antibodies in tested sera.

The three tested fractions proved high specificity in detection of anti-Fasciola Ab in the examined sera at 1:100 serum dilution, while fraction of (14-20 kDa) showed 90% specificity versus HCV infected patients. Moreover; the fraction at MW of 45-65 showed 90% and 85% specificity versus S. mansoni and HCV infected patients. These data proved superiority of fractions at the MW of 25-32 kDa as they did not cross react with any of the previously mentioned cases, followed by that of 14-20 kDa. Specificity of these two purified Fasciola band antigens appeared in the same MW range previously described by Intapan et al. [23] and by Escalante et al. [24] using the EITB technique.

The decreased specificity of the band groups at 14-20 versus HCV infected sera in comparison with that of 25-32 kDa may reflect a degree of cross reactivity or may be as a result of the presence of true infection in the incubation period. For these reasons the second part of the present study focused on more characterization to the diagnostic value of the two specific F. gigantica band groups (25-30 kDa and 14-20 kDa MW) from the aspect of sensitivity toward the present antibodies in the cross reacted cases.

The protein MW bands of 25-32 kDa appeared more sensitive in detecting low levels of anti-Fasciola Ab than that of 1420 kDa. This sensitivity still even (100%) by increasing the serum dilution till 1:500 in sera of Fasciola infected patients decreased to 90% sensitivity at 1:1000 dilutions. At the same time sensitivity of the other fractions (14-20 kDa) decreased to 80% and 60% at increasing the serum dilution to 1:500 and 1:1000 respectively, high sensitivity versus natural infected rabbit sera in-comparison with that collected from other patients. This may be attributed to the nature of infection in the tested patients in relation to the level of anti-Fasciola Ab in their sera.

Failure of the selected Ag in detection of Fasciola infection in some cases may be related to the presence of low antibody titer which is usually associated with chronic infection. Superiority of Fasciola Ag fractions in the range of (25-32) kDa in accurate diagnosis was proved previously by several authors as Farghaly et al. [1] for (23-28 kDa) [23] and [8] for 27 kDa using the EITB technique.

In the authors' opinion, the increase in the sensitivity of the tested fractions versus HCV infected sera in the present study proved that the previous falsely reacted cases reflected a degree of cross reactions than the presence of true unapparent Fasci-ola or mixed infection.

At the same time some authors clarified the role of other kDa in diagnosis of fascioliasis as 17 kDa, 16 kDa [21] and 14.4 kDa [25]. All of these fractions were in the range of the second selected group of bands (14-20 kDa) of the present study.

For conclusion, F. gigantica antigens (25-32 kDa and 1420 kDa) proved their ability to induce accurate diagnosis of infected and suspected cases as well as they are able to exclude cross reaction with cross reacted parasites in the tested serum samples.

It is worthy to mention that the new approach adopted in the present study facilitates commercial use of purified specific antigens in induction of accurate diagnostic test (dot-ELISA) more easily in comparison with EITB especially as it can be read visually.

References

[1] Farghaly AM, Nada SMM, Emam WA, Mattar MA, Mohamed SMA, Sharaf EM, El- Gamal RL. Role of fast-ELISA and western blot in diagnosis of human fascioliasis using crude adult worm and excretory/secretory Fasciola antigens. Parasitologists United J 2009;2(1):55-65.

[2] Demerdash ZA, Diab TM, Aly IR, Mohamed SH, Mahmoud FS, Zoheiry MK, Mansour WA, Attia ME, El-Bassiouny AE. Diagnostic efficacy of monoclonal antibody based sandwich enzyme linked immunosorbent assay (ELISA) for detection of Fasciola gigantica excretory/secretory antigens in both serum and stool. Parasit Vectors 2011;4:176.

[3] Figueroa-Santiago O, Delgado B, Espino AM. Fasciola hepatica saposin-like protein-2-based ELISA for the serodiagnosis of chronic human fascioliasis. Diagn Microbiol Infect Dis 2011;70:355-61.

[4] Valero MA, Periago MV, Peerez-Crespo I, Rodriguez E, Perteguer MJ, Garate T, Gonzalez-Barbera EM, Mas-Coma S. Assessing the validity of an ELISA test for the serological diagnosis of human fascioliasis in different epidemiological situations. Trop Med Int Health 2012;17(5):630-6.

[5] Rokni MB, Samani A, Massoud J, Babaei Nasr M. Evaluation of dot-ELISA method using excretory-secretory antigens of Fasciola hepatica in laboratory diagnosis of human fasciolosis. Iran J Parasitol 2006;1(1):26-30.

[6] Latchumikanthan A, Soundararajan C, DhinakarrajG, Abdul Basith S. Purification and characterization of excretory/ secretory antigens of Fasciola gigantica. Tamilnadu J Vet Anim Sci Jan-Feb 2012;8(1):14-8.

[7] Morphew RM, Wright HA, Lacourse EJ, Woods DJ, Brophy PM. Comparative proteomics of excretory-secretory proteins released by the liver fluke Fasciola hepatica in sheep host bile and during in vitro culture ex host. Mol Cell Proteomics 2007;6:963-72.

[8] Kamel HH, Saad GA, Sarhan RM. Dot-Blot immunoassay of Fasciola gigantica infection using 27 kDa and adult worm regurge antigens in Egyptian patients. Korean J Parasitol Apr 2013;51(2):177-82.

[9] Rivera Marrero CA, Santiago N, Hillyer GV. Evaluation of immunodiagnostic antigens in the excretory-secretory products of Fasciola hepatica. J Parasitol 1988;74(4):645-52.

[10] Lowry OH, Rosenbrough NJ, Farr AL, Randall RJ. Protein measurement with the folin-phenol reagent. J Biol Chem 1951;193:265-75.

[11] Laemmli UK. Cleavage of structural proteins during the assembly of the head of Bacteriophage T4. Nature 1970;227:680-5.

[12] Tsai CM, Frasch CE. A sensitive silver stain for detecting lipopolysaccharides in polyacrylamide gels. Anal Biochem 1982;119:115-9.

[13] Katrak K, Mahon BP, Jones WC, Brautigam S, Mills KH. Preparative separation of foreign antigens for highly efficient presentation of T cells in vitro. J Immunol Methods 1992;156:247-54.

[14] Osman MZ. Assessment of role of different hydatid vaccines in protection against animal hydatidosis. PhD Thesis, Dept. of Parasitology, Faculty of Medicine, Cairo University, Egypt; 2006.

[15] Sabry MA. Epidemiological studies on toxocariasis in animals and man. PhD Thesis, Dept. of Zoonoses, Faculty of Veterinary Medicine, Giza, Egypt; 1999.

[16] Joseph S, Jones FM, Kimani G, Mwatha JK, Kamau T, Kazibwe F, Kemijumbi J, Kabatereine NB, Booth M, Kariuki HC, Ouma JH, Vennervald BJ, Dunne DW. Cytokine production in whole blood cultures from a fishing community in an area of high endemicity for Schistosoma mansoni in Uganda: The differential effect of parasite worm and egg antigens. Infect Immune 2004;72:728-34.

[17] Shaheen HI, Kamal AK, Farid Z, Mansour N, Boctor F, Woody NJ. Dot-Enzyme-linked immunosorbent assay (Dot-ELISA) for the rapid diagnosis of human fascioliasis. J Parasitol 1989;75(4):549-52.

[18] Attallah AM, el-Masry SA, Rizk H, Ismail H, el-Bendary M, Handoussa AE, el Shazly AM, Arafa MA. Fast-Dot ELISA using urine, a rapid and dependable field assay for diagnosis of schistosomiasis. J Egypt Soc Parasitol Apr 1997;27(1):279-89.

[19] Sabry AH, Mséabed EM, Abd El-Wahed MK. Role of Artesunate and Ivermectin used as monotherapeutic agents or in-combination with Triclabendazole against immature Fasciola gigantica worms. Egypt J Med Sci Dec 2012;31(2):585-99.

[20] Mas-Coma S, Valero MA, Bargues MD. Fasciola, lymnaeids and human fascioliasis, with a global overview on disease

transmission, epidemiology, evolutionary genetics, molecular epidemiology and control. Adv Parasitol 2009;69:141-6.

[21] Gorman T, Concha V, Fredes F, Ferrera A, Valdes A, Alcaino H. Detección de antígenos de interés diagnostico en infecciones animales por Fasciola hepatica. Parasitologia al Dia 1994;18:26-32.

[22] De Almeida, MAM, Ferreira B, Planchart S, Terashima A, Maco V, Marcos L, Gotuzzo E, Sánchez E, Náquira C, Scorza JV, Incani RN. Preliminary antigenic characterisation of an adult worm vomit preparation of Fasciola hepatica by infected human sera. Rev Inst Med Trop Sao Paulo Jan-Feb 2007;49(1):31-5.

[23] Intapan PM, Maleewong W, Nateeworanart S, Wongkham C, Pipitgool V, Sukolapong V, Sangmaneedet S. Immunodiagnosis of human fascioliasis using an antigen of Fasciola gigantica adult worm with the molecular mass of 27 kDa by a dot-ELISA. Southeast Asian J Trop Med Public Health 2003;34:713-7.

[24] Escalante H, Davelois K, Ortiz P, Rodríguez H, Díaz E, Jara C. Estandarización de la tecnica de western blot para el diagnostico de la fasciolosis humana utilizando antigenos de excrecion-secrecion de fasciola hepatica 2011;28(3):454-61.

[25] Allam G, Bauomy IR, Hemyeda ZM, Sakran TF. Evaluation of a 14.5 kDa-Fasciola gigantica fatty acid binding protein as a diagnostic antigen for human fascioliasis. Parasitol Res 2012;110:1863-71.