Analysis on the reactivity of five subunits of antigen B family in serodiagnosis of echinococcosis

Stage-Specific Immune Responses to AgB T-Peptides in Patients with Cystic Echinococcosis

Background: The identification of parasite- and stage-specific antigens is crucial for the development of new diagnostic tests for cystic echinococcosis (CE). We previously analysed the interleukin (IL)-4 response to T-specific peptides corresponding to the immunogenic regions of the five antigen B (AgB) subunits, demonstrating that AgB1 is the most immunogenic protein and that the response to all AgB peptides is associated with viable cysts. However, the response in patients with CE3a (WHO-IWGE) cystic stage was not evaluated and no other immunological factors besides IL-4 were included in the analysis. Methods: Four study groups were defined: "CE3a group" (transitional cysts), "CE3b group" (active cysts), "CE4/CE5 group" (inactive cysts), and "NO CE-group" encompassing patients with non-CE cysts (controls). Whole blood was stimulated in vitro with the five different T-specific peptide pools corresponding to the five AgB subunits and with a pool containing all five peptides' pools (total pool). IL-4 and other immunological markers were evaluated by ELISA and a multiplex assay, respectively. Results: Twenty-four patients with CE (CE3a-group n = 3; CE3b-group n = 6; CE4/CE5-group n = 15) and 14 subjects with non-CE cysts were enrolled. IL-4 levels in response to AgB1 and AgB3 pools were significantly increased in CE compared to NO CE groups (p = 0.0201, p = 0.0041). Within the CE patients, the highest IL-4 median level was observed in response to the AgB total pool, the AgB3 and AgB4 pools, followed by the AgB1 pool. Moreover, the IL-4 levels in response to the AgB1 pool were found to be significantly higher in the CE3b group compared to the CE4/CE5 group (p = 0.0070), while no differences were found for the CE3a group. As for other cytokines, we found higher IL-7 levels in response to the AgB4 pool in the CE4/CE5 group compared to the CE3b group (p = 0.0012), higher IL-2 levels in response to the AgB1 pool and AgB total pool in CE3b patients compared to controls (p = 0.0016), and higher IL-13 levels in response to the AgB total pool in patients with CE3b and CE4/CE5 cysts compared to NO CE (p = 0.0016; p = 0.0009). Conclusions: These results contribute to a better knowledge of the immune interplay in the presence of CE and may be useful for further exploring the use of recombinant proteins/peptides in cytokine release assays for the diagnosis and follow-up of CE.

A comparative analysis of ultrasound and serology for the diagnosis and post-treatment monitoring of cystic echinococcosis in experimentally infected sheep

Cystic echinococcosis (CE) is one of the most significant zoonotic diseases globally, affecting both humans and livestocks. The aim of this study was to compare the efficacy of ultrasound (US) and serological methods as early diagnostic markers for both post-infection and post-treatment follow-up of CE in experimentally infected sheep. An hydatid cyst fluid was aspirated and 20,000 viable protoscoleces were administered orally to a dog. After 50 days, all adult parasites were collected. The eggs were extracted and used for the experimental infection of 14 lambs (11 experimental and 3 control). Blood samples were collected and US imaging were performed weekly. Partially purified hydatid cyst fluid (PPHCF) and recombinant paramyosin (EgPmy5) antigens were prepared. The sensitivity of PPHCFA (95 %) was observed to be higher than that of rEgPmy5 (70 %), yet the cross-reaction rates with other helminth infections were 95 % and 20 %, respectively. The cysts first time were imaged at the 8 month after infection by US. Albendazole (7.5 mg/kg) treatment was initiated in the eighth month of the experimental infection. Six sheep were treated with albendazole every 30 days for a period of three months. In two sheep which died on the 8th and 10th day of the treatment, it was observed that the tension in the cyst membrane had disappeared due to a reduction in fluid and fibrosis in the cysts in the liver. Following a three-month treatment, the majority of cysts in the liver had reduced in size to approximately that of a pinhead, and the overall number of cysts had decreased in comparison with the control sheep. After a six-month treatment the presence of fibrotic, pinhead-sized cysts devoid of fluid was observed in the liver. Seropositivity was detected in a sheep with PPHCFA and another sheep with rEgPmy5 from the seventh day of experimental infection and remained detectable till death. In conclusion, albendazole can induce deformation in hydatid cysts as early as the first week of treatment and PPHCF antigen can be used for serological monitoring of the sheep population.

Serosurvey of Cystic Echinococcosis and Related Risk Factors for Infection in Fars Province, Southern Iran: A Population-Based Study

Cystic echinococcosis (CE) is a common zoonotic infection in all provinces of Iran, especially in areas where people live on agriculture and animal husbandry. The current cross-sectional population-based study is aimed at determining the seroprevalence of CE in Kavar County, Fars province, southern Iran. Blood samples were collected from 1500 individuals (749 males and 751 females). Anti-hydatid cyst antibodies were detected, using a recombinant B8/1 antigen of Echinococcus graunlosus in an ELISA system. Multivariate logistic regression analysis was used to find out the independent risk factor for CE seropositivity. Anti-hydatid cyst antibodies were detected in the sera of 131 out of 1500 participants, corresponding to a seroprevalence rate of 8.73%. With a statistically significant difference (p < 0.05), the seroprevalence of hydatid cyst in males and females was 5% and 7%, respectively. Differences in the seropositivity of hydatid cysts were also statistically significant by occupation (p < 0.05). The seroprevalence of hydatid cyst was significantly higher in the age group of 35-45 years than in other age groups (p < 0.05). Multivariate logistic regression showed that only age was associated with seropositivity to CE (OR = 2.23, 95% CI: 1.33-3.72). Moreover, there was a statistically significant association between seropositivity to hydatid cysts and underlying diseases such as hypertension (p = 0.049) and fatty liver (p = 0.048). The findings of this study indicate that the seroprevalence rate of CE is relatively high in the Fars province, southern Iran, and this high rate of infection is mainly linked to people's jobs and lifestyles.

Evaluation of a novel Echinococcus granulosus recombinant fusion B-EpC1 antigen for the diagnosis of human cystic echinococcosis using indirect ELISA in comparison with a commercial diagnostic ELISA kit

Cystic echinococcosis (CE) is a zoonotic parasitic disease caused by the metacestode of Echinococcus granulosus sensu lato (s.l.). A large proportion of the patients are asymptomatic at the early and late stages of the disease. CE diagnosis is mainly based on imaging techniques. Laboratory diagnosis including antibody-antigen (recombinant or fusion recombinant) can be used for the diagnosis and follow up of CE and alveolar echinococcosis (AE), but need optimization and standardization. This study aimed to evaluate the efficacy of a recombinant B-EpC1 (rB-EpC1) fusion antigen comprising B1, B2, B4, and EpC1 antigens of E. granulosus using indirect ELISA in comparison with a commercial ELISA kit for the serodiagnosis of CE. The recombinant protein was expressed in the expression host, E. coli BL21, and purified. This recombinant antigen was then evaluated by indirect ELISA and compared to the commercial CE diagnostic kit (Vircell, Spain). The study samples included 124 human sera consisting of 62 sera of patients with CE, and 62 sera of individuals without clinical evidences of CE and specific anti-CE antibodies in routine indirect ELISA. The diagnostic sensitivity and specificity of the indirect rB-EpC1-ELISA test for detection of specific anti-hydatid cyst antibodies in human CE were 95.2% and 96.8%, respectively. Also, the diagnostic sensitivity and specificity of the commercial ELISA test were 96.8% in this study. Initial evaluation of the recombinant fusion antigen (B-EpC1) was promising for the detection of CE by ELISA in clinical settings. Standardization and evaluation of recombinant fusion protein require further studies.

Evaluation of two heterologous recombinant antigens for the serological diagnosis of human polycystic echinococcosis

Polycystic echinococcosis (PE) is a zoonosis endemic in the Neotropical region of the Americas. It is caused by the larval stage of the cestode Echinococcus vogeli, which develops as harmful cysts that slowly grow in the liver, lungs and other organs of humans and other host species. Human PE diagnosis is usually based on clinical and epidemiological aspects and imaging techniques, often requiring confirmation by immunological assays. The currently available serological tests for detecting antibodies against Echinococcus spp. are mostly based on complex, variable and poorly characterized mixtures of native parasite antigens, which impairs specificity and/or sensitivity. In this scenario, the evaluation of well-characterized alternative antigens is urgently needed for the improvement of PE diagnosis. Here, two subunits (AgB8/1 and AgB8/2) of the major secretory antigen from Echinococcus granulosus (antigen B (AgB)), of diagnostic value for cystic echinococcosis, were validated for PE diagnosis. These antigens, produced as pure recombinant proteins (rAgB8/1 and rAgB8/2) in Escherichia coli, allowed detecting specific immunoglobulin G antibodies in sera from PE patients in an enzyme-linked immunosorbent assay, with sensitivities of 83.72% and 81.40%, respectively, and specificities of 83.12% and 80.09%, respectively. The use of recombinant proteins overcomes difficulties to obtain parasite material and reduced non-specific reactions and costs. Our results demonstrated reproducibility and accuracy high enough to be considered valid according to the acceptance criteria for Food and Drug Administration assay validation. This qualifies rAgB8/1 and rAgB8/2 as potential substitutes for the currently used parasite crude or partially purified antigens.

Comparison of the multi-epitope recombinant antigen DIPOL and hydatid fluid for the diagnosis of patients with cystic echinococcosis

The use of serological tests containing multiple immunodominant antigens rather than single antigens have the potential to improve the diagnostic performance in Cystic Echinococcoses (CE) as a complement tool to clear the inconclusive imaging data. Here, we comparatively evaluated the diagnostic value of Hydatid Fluid (HF) and the recently described recombinant multi-epitope antigen DIPOL in IgG-ELISA in a clinically defined cohort of CE patients. The serum samples from 149 CE patients were collected just before surgical or Percutaneous- Aspiration- Injection- Reaspiration (PAIR) procedures. Additionally, serum samples of patients with other parasitic infections (n=49) and healthy individuals (n=21) were also included in the study as controls. To investigate the association between the genotype of the parasite and DIPOL, cyst materials from 20 CE patients were sequenced. In terms of overall sensitivity, HF was higher than DIPOL (82.55%,78.52%, respectively). However, while the sensitivity of HF was higher than DIPOL in patients with active and transitional cysts (83.3%, 75.4%, respectively), sensitivity of DIPOL in inactive cysts was higher compared to HF (95.6%, 78.3%, respectively). The sensitivity of DIPOL depending on cyst stage was statistically significant (P= 0.041). In terms of specificity, DIPOL was found to be better than HF (97.71%, 91.43%, respectively). By genotyping, the majority of 20 patients showed G1 genotype (80%). All patients harboring G3 and G1/G3 cyst genotypes were positive with both antigens, while 87.5% of patients with G1 genotype were seropositive with HF and 75% with DIPOL. The overall sensitivity and high specificity of DIPOL suggest that this recombinant protein containing immunodominant epitopes is a potential substitute for the HF by serological tests for the diagnosis of CE.

Promising proteins detected by Western blot from Echinococcus granulosus protoscoleces for predicting early post-surgical outcomes in CE-affected Tunisian children

BACKGROUND

Cystic echinococcosis (CE) affects predominantly young patients in highly endemic areas. Improved serological methods are needed for the follow-up of CE cases, especially given the high rates of post-surgical relapse that require detection as soon as possible.

METHODS

We designed a study to investigate the value of antigenic proteins extracted from Echinococcus granulosus (E. granulosus) protoscoleces, and of recombinant B2t and 2B2t proteins, for assessing the efficacy of surgical treatment carried out on CE-affected children. This study was performed on 278 plasma samples collected from 59 Tunisian children surgically treated for CE and monitored for 3 years post-surgery. The patients were classified according to post-surgical outcomes into a "non-relapsed" (NRCE) and a "relapsed" (RCE) group. We performed in-house ELISAs to measure anti-B2t and anti-2B2t IgG and immunoblotting for the detection of IgG against SDS-PAGE-resolved E. granulosus protoscoleces-specific antigens. The Wilcoxon test was applied to assess anti-B2t and anti-2B2t IgG levels. We applied the Cochran Q test to compare the distribution of immunoblotting antigenic bands between 1-month and 1-year post-surgery.

RESULTS

The probability of being "relapse-free" when a decrease in antibody titers occurred between 1 month and 1 year post-surgery was 81% and 75%, respectively, for anti-B2t and anti-2B2t IgG. We identified five protoscolex protein bands of 20, 26/27, 30, 40 and 46 kDa as highly immunoreactive by immunoblot for both RCE and NRCE patients at 1 month post-surgery, and significantly lower immunoreactivity after 1 year (p < 10^-4) for NRCE compared to RCE patients. The proteins at 26/27 and 40 kDa displayed the best performance in predicting the outcome, with an 84% probability of being relapse-free when the reactivity against the 40 kDa antigen, the doublet at 26/27 kDa, or both was absent or disappeared between 1 month and 1 year post-surgery, and a 93% probability of being relapsed when both bands remained reactive or increased in intensity between the two time points.

CONCLUSIONS

The B2t protein could be useful for the prediction of CE early post-surgical outcomes. The proteins of E. granulosus protoscoleces, especially the doublet P26/27 and P40, could be promising predictive biomarkers for the post-surgical follow-up of CE cases as well.

Serodiagnosis of human cystic echinococcosis based on recombinant antigens B8/1 and B8/2 of Echinococcus granulosus

BACKGROUND

Cystic echinococcosis (CE) is a widespread parasitic disease caused by the larval stage of Echinococcus granulosus. Since current methods for the diagnosis of CE are not efficient enough, rapid, and reliable tests are required for the acceleration of CE diagnosis. The present study aimed to produce recombinant B8/1 and B8/2 antigens of E. granulosus and evaluate their sensitivities and specificities separately and simultaneously for the diagnosis of CE.

METHODS

The recombinant B8/1 and B8/2 antigens were produced and used in an ELISA system for the diagnosis of CE. The sera specimens including 30 sera from pathologically confirmed CE patients, 30 from other non-CE patients, and 30 from healthy controls, were evaluated by the ELISA, using AgB8/1 and AgB8/2.

RESULTS

The results showed a sensitivity of 93.33%, 90%, and 96.7% for AgB8/1, AgB8/2, and their combination, respectively. The specificities were 91.7%, 93.33%, and 93.33% for AgB8/1, AgB8/2, and their combination, respectively.

CONCLUSION

Simultaneous usage of AgB8/1 and AgB8/2 increased the test sensitivity for the diagnosis of CE. Furthermore, the specificity of AgB8/1 and AgB8/2 combination was more than AgB8/1 and equal to AgB8/2 alone. The findings revealed that the simultaneous usage of AgB8/1 and AgB8/2 could be a suitable approach for the diagnosis of CE.

A Comparative Study of Different Immunoassays to Detect Specific Antibodies to Echinococcus Spp. in Human Sera

Human echinococcosis, one of the most serious of parasitic zoonoses, is caused by the larval stages of taeniid cestodes of the genus Echinococcus. The study aimed to assess the reliability of the detection of specific antibodies to E. multilocularis and E. granulosus s.l. in human sera and to compare their diagnostic potential for their utilization in the practice. In the study, the somatic antigen of E. multilocularis (AgEm), antigen B (AgB), and the hydatid fluid antigen of E. granulosus and two commercial ELISA kits – Echinococcus granulosus (Bordier Affinity Products, Crissier, Switzerland) and NovaLisa^TMEchinococcus IgG (NovaTec Immunodiagnostica, Germany) – were compared. Sera of patients with alveolar and cystic echinococcosis, and with different parasitic/other infections were used to evaluate the sensitivity, specificity and cross-reactivity of in-house and commercial ELISA methods. AgEm presented the highest values regarding the diagnostic indicators, showing 100 % specificity and 90.0 % sensitivity. The tests for serological diagnostics of cystic echinococcosis were less sensitive and specific. The Echinococcus granulosus kit had 83.8 % specificity and 88.2 % sensitivity, while AgB and AgHF showed 85.0 % and 86.3 % specificity, and 76.5 % and 100 % sensitivity, respectively. NovaLisa^TMEchinococcus IgG proved to have 95.7 % specificity and 77.8 % sensitivity. The results point out that the combination of different serological tests and approaches in accordance with clinical and imaging findings is still essential to prove the correct diagnosis in suspected patients.

Human cystic echinococcosis: Serological diagnosis by indirect hemagglutination test, enzyme-linked immunosorbent assay, immunoelectrophoresis, and immunoblotting in surgically confirmed patients versus cases diagnosed by imaging techniques

INTRODUCTION

Human cystic echinococcosis (CE) diagnosis is based on imaging findings and serology. Serology is the first-line test followed by imaging tests.

MATERIALS AND METHODS

A total of 268 serum samples from CE patients were included in this study. The serodiagnosis was made simultaneously by indirect hemagglutination assay (IHA), enzyme-linked immunosorbent assay (ELISA), immunoblotting test (IB), and immunoelectrophoresis (IEP).

RESULTS

In serum samples belonging to surgically confirmed CE patients, we observed a percentage of positivity of 83.7% [77.2%-89.0%] and 80.7% [73.9%-86.4%] for IHA and IgG-ELISA, respectively. IgG-IB was associated with a higher positivity rate than IEP with 81.3% [74.6%-86.9%] and 62.0% [54.2%-69.5%], respectively. IHA and ELISA results were analyzed using cut-off generated by receiver operating curves. The best diagnostic performances were achieved by IHA (cut-off ≥1/128) and ELISA (>1.16 index). Sensitivities reported in patients with suggestive imaging findings and positive Echinococcus IB were 86.2% [78.0%-92.2%], 72.5% [62.8%-80.9%], 49.0% [39.0%-59.1%] for IHA, IgG-ELISA, and IEP, respectively. All tests gave false negative results in the confirmed CE group. Overall, 18.6% of negative results were obtained by IgG-IB test. Cross-reactivities with non-hydatid serum samples were observed in all tests. Only one patient carrying Taenia saginata serum cross-reacted with 8/12 kDa band by IB. We observed specificity at 73% [63.2%-81.4%], 87% [78.8%-92.9%], 99% [94.6%-100.0%], and 99% [94.6%-100.0%] with IHA, IgG-ELISA, IEP, and IgG-IB, respectively. Serology was less sensitive (74%) in lung cysts. Sensitivity was better in liver cysts, especially by IgG-IB (96%).

Survey of echinococcoses in southeastern Qinghai Province, China, and serodiagnostic insights of recombinant Echinococcus granulosus antigen B isoforms

Background

Echinococcoses, caused by metacestodes of Echinococcus granulosus (cystic echinococcosis; CE) and E. multilocularis (alveolar echinococcosis; AE), represent major emerging parasitic diseases. These enzootic helminthiases invoke significant public health concerns and social burdens in endemic areas. The diseases are prevalent in the Qinghai-Tibetan Plateau, China, while community-based epidemiological studies have been scarcely reported. We surveyed echinococcosis patients in the southeastern Qinghai Province, China, to better understand the concurrent epidemiological situation in this area.

Methods

During July and August of 2013 and 2014, we screened echinococcosis patients at Yushu and Golog Prefectures, Qinghai Province, China, in a diagnostic campaign. A total of 2856 people (male:female ratio, 1:1.12; mean age, 34.6 years; age range, 6–88 years) were ultrasonographically examined for the presence of hepatic echinococcal cysts. We also collected serum samples from patients and analyzed antibody reactivity against recombinant forms of diverse E. granulosus antigen Bs (rEgAgB1-5) by enzyme-linked immunosorbent assay.

Results

We detected 134 patients whose imaging scans were compatible with CE (115 cases) and AE (20 patients). One patient might have been infected with both CE and AE. The overall incidence was 4.7% (CE, 4.0%; AE, 0.7%). A large proportion (67.5%) of CE patients was diagnosed at active and transitional CE1-CE3 stages in their late 30s. The AE cases were generally detected at advanced stage in patients at early 20s (60%). Analysis of the receiver operating characteristic curve and Youden’s index indicated that rEgAgB2 was the most promising biomarker, followed by rEgAgB3 and rEgAgB1. Overall, sensitivity and specificity of rEgAgB1-3 were 84.5–92.7% and 91.9–94.6%, respectively. rEgAgB4 and 5 showed low sensitivity with high cross-reactivity.

Conclusions

Our results strongly suggest that disability-adjusted life years related to echinococcoses in Qinghai-Tibetan areas might be more serious than previously considered. Control and prevention strategy against CE and AE are highly required in these areas. In addition to ultrasonography, serological tests might provide supportive data. However, serological data should be carefully interpreted for differential diagnosis, especially in areas where both CE and AE are co-endemic.

Electronic supplementary material

The online version of this article (10.1186/s13071-019-3569-6) contains supplementary material, which is available to authorized users.

Expression and purification of truncated recombinant B8/1 protein of Echinococcus granulosus for diagnosis of hydatid infection in human

Hydatidosis is one of the most important diseases common between animals and human beings. Caused by Echinococcus granulosus tapeworm, the disease has a global epidemic. The serological diagnostic tests that are now utilized to confirm the imaging approaches have some drawbacks such as low sensitivity and cross-reaction with the serum of the patients infected with other parasites. The application of recombinant and synthetic antigens has proven improvement in the functionality of serological diagnostic tests. The purpose of this study was to demonstrate the expression and purification of truncated recombinant B8/1 (trB8/1) antigen and its application in ELISA for diagnosis of hydatid infection in human. The tEgB8/1 was colonized in the expression vector pET28b (+) and expressed in different strains of E. coli. This protein was purified by Ni²⁺-NTA chromatography. The antigenicity of the protein was evaluated by Western blotting and ELISA. In the test, 50 positive serum samples from hydatid infected patients, 50 samples from healthy people, and 30 serum samples from patients with other parasitic diseases were used to determine the sensitivity and the specificity of this antigen. The measured sensitivity and specificity of this antigen were identified to be 75.75% and 96.38% respectively. The P value of <0.0001 by using ROC curve, confirmed that this antigen is able to differentiate between healthy and hydatid-infected individuals. Considering the excellent specificity of this antigen and in order to enhance the sensitivity, it is recommended to use a combination of this antigen with other antigens (e.g., EgB8/2-8/5).

Multi-Epitope Fusion Protein Eg mefAg-1 as a Serodiagnostic Candidate for Cystic Echinococcosis in Sheep

Cystic echinococcosis (CE) in sheep is a hazardous zoonotic parasitic disease that is caused by Echinococcus granulosus (Eg). At present, serological test is an important diagnostic method for Eg infection in domestic animals. Here, a fusion protein Eg mefAg-1 harboring 8 dominant B-cell epitopes of Eg such as antigen B, tetraspanin 1, tetraspanin 6, reticulon and Eg95 was produced in E. coli and evaluated for CE in sheep by indirect ELISA. Eg mefAg-1 showed in ELISA a high sensitivity (93.41%) and specificity (99.31%), with a coincidence rate of 97.02%. Overall, it is suggested that the Eg mefAg-1 could be a potential antigen candidate for CE serodiagnosis in sheep.

Evaluation of the recombinant antigens B2t and 2B2t, compared with hydatid fluid, in IgG-ELISA and immunostrips for the diagnosis and follow up of CE patients

Cystic echinococcosis (CE) is one of the most widespread helminthic zoonoses and is caused by the tapeworm Echinococcus granulosus complex. CE diagnosis and monitoring primarily rely on imaging techniques, complemented by serology. This is usually approached by the detection of IgG antibodies against hydatid fluid (HF), but the use of this heterogeneous antigenic mixture results in a variable percentage of false positive and negative results, and has shown to be useless for follow-up due to the long persistence of anti-HF antibodies in cured patients. To improve test performances and standardization, a number of recombinant antigens mainly derived from HF have been described, among them the B2t and 2B2t antigens. The performance of these antigens in the diagnosis and follow up of patients with CE has been so far evaluated on a limited number of samples. Here, we evaluated the performances of tests based on B2t and 2B2t recombinant antigens compared to HF in IgG-ELISA and immunochromatography (IC) for the diagnosis and follow-up of patients with CE in a retrospective cohort study. A total of 721 serum samples were collected: 587 from 253 patients with CE diagnosed by ultrasonography (US), 42 from patients with alveolar echinococcosis and 92 from healthy donors from Salamanca (Spain). The highest overall sensitivity was obtained with HF in ELISA (85.5%), followed by IC containing HF and 2B2t-HF (83.0% and 78.2%, respectively). The lowest sensitivity was obtained with B2t and 2B2t in ELISA (51.8%). The highest specificity was obtained with IC containing 2B2t-HF (100%), and the lowest with HF-ELISA (78.0%). The lowest cross-reactivity with sera from patients with alveolar echinococcosis was detected with the recombinant antigens in ELISA (9.5% - 16.7%) and the highest with the HF-IC (64.3%). The results of B2t and 2B2t-ELISA were influenced by cyst stage, as classified by US according to the WHO-Informal Working Group on Echinococcosis (WHO-IWGE), with low sensitivity for inactive (CE4 and CE5) cysts, and by the drug treatment, with higher sensitivity in patients after drug treatment compared with patients not subjected to drug treatment. The two recombinant antigens in ELISA provided promising results for monitoring patients in follow-up, although their use is limited to patients with positive serology against them at the beginning of the follow-up. Potential biological reasons behind the low sensitivity of the recombinant antigens and possible strategies to enhance the performance of CE serology are discussed.

Cystic echinococcosis (CE) is a helminthic zoonosis caused by Echinococcus granulosus sensu lato. CE diagnosis and monitoring is of paramount importance for the clinical management of patients and primarily rely on imaging techniques, complemented by serology. CE serology is usually based on the detection of antibodies against hydatid fluid (HF), but the use of this heterogeneous antigenic mixture shows several drawbacks, including false positive and negative results, unsatisfied predictive values, and long persistence of detectable antibody levels in cured patients. As an alternative, to improve test performances and standardization, several recombinant antigens have been described, but these have been so far evaluated only on a limited number of samples. Here, two recombinant antigens derived from one of the immunodominant HF antigens (antigen B2) have been tested in enzyme-linked immunosorbent assay (ELISA) and in immunochromatographic strips (IC) against 721 serum samples. Although more specific than the HF, the recombinant antigens in ELISA showed low sensitivity for patients with inactive (CE4 and CE5) cysts and for patients not subjected to drug treatment. This limited their use for follow-up, although promising, to those patients with positive serology at the beginning of the follow-up period. These results will aid in the future development of a serological test with enhanced performance in the diagnosis and follow-up of patients with CE.

Design and construction of a new recombinant fusion protein (2b2t+EPC1) and its assessment for serodiagnosis of cystic echinococcosis

The immunodiagnostic tests for cystic echinococcosis (CE) are mostly serological tests based on ELISA that use hydatid cyst antigens for primary screening because of its simple preparation and availability. The challenge to develop new serological methods (as compared to those based on the hydatid cyst fluid antigens) to meet the gold standard remains. Appropriate sources of antigenic material are necessary for application to improve the efficacy of immunodiagnostic tests at a population level. In the current study, a fusion protein containing the coding sequence of antigen B2t and two sequences of EPC1 antigen with some modifications was reconstructed. Using bioinformatics tools, these sequences were joined together by applying the sequence of a rigid α-helix-forming linker to obtain an appropriate structure of a fusion protein. Synthetic recombinant fusion protein was expressed using pET28a as a vector and evaluated by indirect ELISA test for sera from patients with hepatic CE and other parasitic infections. The sensitivity of the fusion protein was lower (88.46%) than the available ELISA kit (96.15%). However, the differences in sensitivity were not statistically significant as compared to the recombinant fusion peptide with the commercial kit (p = 0.269). The specificity of the recombinant fusion protein (95.45%) was not significantly lower than the commercial kit (96.59%; p = 1.000). Moreover, surprisingly there was no difference in the cross-reactivity values of performance between the recombinant-ELISA and commercial kit. The positive and negative predictive values of the recombinant antigen were achieved as 92% and 93.33%, respectively, while for the commercial kit, they were obtained as 94.33% and 97.70%, respectively. In conclusion, as an early evaluation of these antigens the performance of our recombinant fusion protein in ELISA is relatively promising. Although, it seemed that this peptide with specific antigenic epitopes might be more appropriate for the serological evaluation of CE by use of bioinformatics tools, our findings showed that cross-reactions and a negative reaction could occur in clinical performance. This fusion protein may have utility for diagnosis in humans, but further evaluation is needed using the WHO ultrasound classification for CE.

A T-cell diagnostic test for cystic echinococcosis based on Antigen B peptides

Cystic echinococcosis (CE) immunodiagnosis is still imperfect. We recently set-up a whole-blood test based on the interleukin (IL)-4 response to the native Antigen B (AgB) of Echinococcus granulosus. However, AgB is encoded by a multigene family coding for five putative subunits. Therefore, the aims of this study were to analyse the IL-4 response to peptides spanning the immunodominant regions of the five AgB subunits and to evaluate the accuracy of this assay for CE diagnosis. Peptides corresponding to each subunit were combined into five pools. A pool containing all peptides was also used (total pool). IL-4 evaluated by enzyme-linked immunosorbent assay was significantly higher in patients with CE compared to those without (NO-CE subjects) when whole-blood was stimulated with AgB1 and with the total pool. Moreover, IL-4 levels in response to the total pool were significantly increased in patients with active cysts. Receiver Operator Curve analysis identified a cut-off point of 0.59 pg/mL predicting active cysts diagnosis with 71% sensitivity and 82% specificity in serology-positive CE patients. These data, if confirmed in a larger cohort, offer the opportunity to develop new diagnostic tools for CE based on a standardized source of AgB as the peptides.

Screening of antigenic vesicular fluid proteins of Echinococcus multilocularis as potential viability biomarkers to monitor drug response in alveolar echinococcosis patients

PURPOSE

The only drugs available to treat alveolar echinococcosis (AE) are mostly parasitostatic and in many cases prescribed for life. Decision criteria for discontinuation rely on the absence of parasitic viability. The aim of the present study is to search for candidate proteins that may exhibit good potential as biomarkers for viability.

EXPERIMENTAL DESIGN

Sixteen serum samples (five healthy controls, 11 patients with AE), are used. AE-patients are classified into three groups "Cured" (n = 2), "ABZ-responders" (n = 4) and "ABZ-nonresponders" (n = 5). Immunoreactive proteins from vesicular fluid (VF) are identified and quantified by LC-MS/MS analysis after immunoprecipitation (IP) using all 16 serum samples.

RESULTS

Shotgun analysis of VF lead to the identification of 107 E. multilocularis proteins. Comparative proteomics reveal nine proteins more abundant in IP eluates from ABZ-nonresponder patients (cathepsin b, prosaposin a preprotein, actin modulator protein, fucosidase alpha L1 tissue, gluthatione-S-tranferase, beta galactosidase, elongation factor 2, H17g protein tegumental antigen, and NiemannPick C2 protein).

CONCLUSIONS AND CLINICAL RELEVANCE

Detection of antibodies against these proteins by ELISA could be helpful to monitor the course of alveolar echinococcosis under albendazole (ABZ) treatment.

Laboratory Diagnosis of Echinococcus spp. in Human Patients and Infected Animals

Among the species composing the genus Echinococcus, four species are of human clinical interest. The most prevalent species are Echinococcus granulosus and Echinococcus multilocularis, followed by Echinococcus vogeli and Echinococcus oligarthrus. The first two species cause cystic echinococcosis (CE) and alveolar echinococcosis (AE) respectively. Both diseases have a complex clinical management, in which laboratory diagnosis could be an adjunctive to the imaging techniques. To date, several approaches have been described for the laboratory diagnosis and followup of CE and AE, including antibody, antigen and cytokine detection. All of these approaches are far from being optimal as adjunctive diagnosis particularly for CE, since they do not reach enough sensitivity and/or specificity. A combination of several methods (e.g., antibody and antigen detection) or of several (recombinant) antigens could improve the performance of the adjunctive laboratory methods, although the complexity of echinococcosis and heterogeneity of clinical cases make necessary a deep understanding of the host-parasite relationships and the parasite phenotype at different developmental stages to reach the best diagnostic tool and to make it accepted in clinical practice. Standardization approaches and a deep understanding of the performance of each of the available antigens in the diagnosis of echinococcosis for the different clinical pictures are also needed. The detection of the parasite in definitive hosts is also reviewed in this chapter. Finally, the different methods for the detection of parasite DNA in different analytes and matrices are also reviewed.

Characterisation of Antigen B Protein Species Present in the Hydatid Cyst Fluid of Echinococcus canadensis G7 Genotype

The larva of cestodes belonging to the Echinococcus granulosus sensu lato (s.l.) complex causes cystic echinococcosis (CE). It is a globally distributed zoonosis with significant economic and public health impact. The most immunogenic and specific Echinococcus-genus antigen for human CE diagnosis is antigen B (AgB), an abundant lipoprotein of the hydatid cyst fluid (HF). The AgB protein moiety (apolipoprotein) is encoded by five genes (AgB1-AgB5), which generate mature 8 kDa proteins (AgB8/1-AgB8/5). These genes seem to be differentially expressed among Echinococcus species. Since AgB immunogenicity lies on its protein moiety, differences in AgB expression within E. granulosus s.l. complex might have diagnostic and epidemiological relevance for discriminating the contribution of distinct species to human CE. Interestingly, AgB2 was proposed as a pseudogene in E. canadensis, which is the second most common cause of human CE, but proteomic studies for verifying it have not been performed yet. Herein, we analysed the protein and lipid composition of AgB obtained from fertile HF of swine origin (E. canadensis G7 genotype). AgB apolipoproteins were identified and quantified using mass spectrometry tools. Results showed that AgB8/1 was the major protein component, representing 71% of total AgB apolipoproteins, followed by AgB8/4 (15.5%), AgB8/3 (13.2%) and AgB8/5 (0.3%). AgB8/2 was not detected. As a methodological control, a parallel analysis detected all AgB apolipoproteins in bovine fertile HF (G1/3/5 genotypes). Overall, E. canadensis AgB comprised mostly AgB8/1 together with a heterogeneous mixture of lipids, and AgB8/2 was not detected despite using high sensitivity proteomic techniques. This endorses genomic data supporting that AgB2 behaves as a pseudogene in G7 genotype. Since recombinant AgB8/2 has been found to be diagnostically valuable for human CE, our findings indicate that its use as antigen in immunoassays could contribute to false negative results in areas where E. canadensis circulates. Furthermore, the presence of anti-AgB8/2 antibodies in serum may represent a useful parameter to rule out E. canadensis infection when human CE is diagnosed.

Cystic echinococcosis (CE), a worldwide-spread zoonosis, affects livestock mammals and humans with significant economic and public health impact. It is caused by the infection with the larva of cestodes belonging to Echinococcus granulosus complex, a series of parasite species with preference for different hosts. Among them, Echinococcus canadensis larva uses mainly camels, goats and pigs as hosts. Species/genotypes belonging to E. canadensis are considered the second most common cause of human CE, but its contribution may be underestimated since causes asymptomatic or more benign infections than other E. granulosus complex species. The most relevant antigen for CE diagnosis is a lipoprotein called antigen B (AgB). AgB antigenicity is linked to its protein moiety that is encoded by several genes. One of these genes, AgB2, seems to be differentially expressed within E. granulosus complex. Using high sensitivity proteomic tools we analysed the composition of AgB obtained from E. canadensis larva, detecting the protein products of all AgB genes, except AgB2. Since AgB subunits have been widely used as antigens in immunoassays for human CE diagnosis, our results indicate that using AgB2 protein product in these assays may lead to false-negative results, particularly in geographical areas where E. canadensis species/genotypes circulate.

Diagnosis of cystic echinococcosis in buffaloes by native 8 kDa antigen using latex agglutination test (LAT)

The dog tapeworm Echinococcusgranulosus is the causative agent of cystic hydatid disease in domestic/wild herbivores animals and man. Accurate immunodiagnosis of the infection requires highly specific and sensitive antigens. The aim of this study was to develop and evaluate immunoassays with principles of precipitation, agglutination for the identification of buffaloes infected with hydatid cyst which would allow the monitoring of animals from endemic areas and identifying infected animals prior to slaughter. The immunoassays were developed and validated using hydatid specific, non-cross reactive low molecular weight 8 kDa hydatid cyst fluid protein. Sera used for the assay validations were obtained from 200 buffaloes infected naturally with hydatid cyst and 200 non-infected buffaloes. The diagnostic sensitivity with latex agglutination test was 98.67 %. It should be useful for the conformation of hydatid cyst infected individual sheep.

Analysis on Gene Expression Profile in Oncospheres and Early Stage Metacestodes from Echinococcus multilocularis

Alveolar echinococcosis is a worldwide zoonosis of great public health concern. Analysis of genome data for Echinococcus multilocularis has identified antigen families that can be used in diagnostic assays and vaccine development. However, little gene expression data is available for antigens of the egg and early larval stages. To address this information gap, we used a Next-Generation Sequencing approach to investigate three different stages (non-activated and activated oncospheres, and early stage metacestodes) of E. multilocularis (Nemuro strain). Transcriptome data analysis revealed that some diagnostic antigen gp50 isoforms and the antigen Eg95 family dominated in activated oncospheres, and the antigen B family dominated in early stage metacestodes. Furthermore, heat shock proteins and antigen II/3 are constantly expressed in the three stages. The expression pattern of various known antigens in E. multilocularis may give fundamental information for choosing candidate genes used in diagnosis and vaccine development.

Immunodiagnosis of human hydatid disease: Where do we stand?

Cystic echinococcosis (CE) is a zoonotic parasitic infection caused by the larval stage of Echinococcus granulosus. Diagnosis of CE mainly relies on a combination of serological testing along with imaging approaches. A variety of serological methods, mainly based on hydatid cyst fluid, antigen B (AgB) and antigen 5, have been developed and used for immunodiagnosis of CE, yet their performances are not satisfactory. Although utilizing of recombinant or synthetic antigens, improved the performance of serological tests, it has not applicably overcome the problem of low sensitivity and cross reactivity, seen in the diagnosis of CE. Performances of immunodiagnostic tests based on AgB subunits are promising. The 8 kDa subunit of AgB is the most studied antigen in native, synthetic or recombinant form for diagnosis of CE. From the 5 subunits of AgB, antigen B8/1 and B8/2 provided the highest diagnostic sensitivity and specificity. Moreover, detecting of specific antibodies of IgG subclasses has improved the efficacy of immunodiagnostic tests. Among the IgG subclasses, both IgG2 and IgG4 are considered as good markers for diagnosis and IgG4 as a suitable marker for follow up of the patients. In this review an overview of immunodiagnostic methods, related antigens and their performances in the diagnosis of CE are given. The paper highlights pitfall and challenges in the serological diagnosis of CE. Moreover, limitation of currently available immunodiagnostic tests and the most recent development in the designing and application of serological assays for diagnosis of CE in human are addressed.

Serological Diagnosis and Follow-Up of Human Cystic Echinococcosis: A New Hope for the Future?

Cystic echinococcosis (CE) is an important helminthic zoonotic disease caused by the Echinococcus granulosus complex. In humans, CE is a chronic disease driven by the growth of echinococcal cysts in different organs. Prognosis of this disease depends on multiple factors, including location, number, size, and stage of the cysts, making CE a disease of complex management. CE is usually asymptomatic for years and attracts limited attention from funding organizations and health authorities. For this reason, only experts' recommendations are available but no evidence-based conclusions have been drawn for CE clinical management. One of those pitfalls refers to the lack of evidence to support the use of serological tools for the diagnosis and follow-up of CE patients. In this respect, crude antigens are used to detect specific antibodies in patients, giving rise to false positive results. The advent of molecular techniques allowing the production of recombinant proteins has provided a number of candidate antigens that could overcome the problems associated with the use of crude parasite extracts in the serological assays. In this review, we present the last advances in this field, proposing the use of serology to support cyst stage-specific diagnosis and follow-up.

An easy and efficient method for native and immunoreactive Echinococcus granulosus antigen 5 enrichment from hydatid cyst fluid

Background

Currently, the serodiagnosis of cystic echinococcosis relies mostly on crude Echinococcus granulosus hydatid cyst fluid as the antigen. Consequently, available immunodiagnostic tests lack standardization of the target antigen and, in turn, this is reflected on poor sensitivity and specificity of the serological diagnosis.

Methodology/Principal Findings

Here, a chromatographic method enabling the generation of highly enriched Antigen 5 (Ag5) is described. The procedure is very easy, efficient and reproducible, since different hydatid cyst fluid (HCF) sources produced very similar chromatograms, notwithstanding the clearly evident and extreme heterogeneity of the starting material. In addition, the performance of the antigen preparation in immunological assays was preliminarily assessed by western immunoblotting and ELISA on a limited panel of cystic echinococcosis patients and healthy controls. Following western immunoblotting and ELISA experiments, a high reactivity of patient sera was seen, with unambiguous and highly specific results.

Conclusions/Significance

The methods and results reported open interesting perspectives for the development of sensitive diagnostic tools to enable the timely and unambiguous detection of cystic echinococcosis antibodies in patient sera.

Cystic echinococcoses in Mongolia: molecular identification, serology and risk factors

Background

Cystic echinococcosis (CE) is a globally distributed cestode zoonosis that causes hepatic cysts. Although Echinococcus granulosus sensu stricto (s.s.) is the major causative agent of CE worldwide, recent molecular epidemiological studies have revealed that E. canadensis is common in countries where camels are present. One such country is Mongolia.

Methodology/Principal Findings

Forty-three human hepatic CE cases that were confirmed histopathologically at the National Center of Pathology (NCP) in Ulaanbaatar (UB) were identified by analysis of mitochondrial cox 1 gene as being caused by either E. canadensis (n = 31, 72.1%) or E. granulosus s.s. (n = 12, 27.9%). The majority of the E. canadensis cases were strain G6/7 (29/31, 93.5%). Twenty three haplotypes were identified. Sixteen of 39 CE cases with data on age, sex and province of residence were citizens of UB (41.0%), with 13 of the 16 cases from UB caused by E. canadensis (G6/7) (81.3%). Among these 13 cases, nine were children (69.2%). All pediatric cases (n  =  18) were due to E. canadensis with 17 of the 18 cases (94.4%) due to strain G6/7. Serum samples were available for 31 of the 43 CE cases, with 22 (71.0%) samples positive by ELISA to recombinant Antigen B8/1 (rAgB). Nine of 10 CE cases caused by E. granulosus s.s. (90.0%) and 13 of 20 CE cases by E. canadensis (G6/7) (65.0%) were seropositive. The one CE case caused by E. canadensis (G10) was seronegative. CE cases caused by E. granulosus s.s. showed higher absorbance values (median value 1.131) than those caused by E. canadensis (G6/7) (median value 0.106) (p  =  0.0137).

Conclusion/Significance

The main species/strains in the study population were E. canadenis and E. granulossus s.s. with E. canadensis the predominant species identified in children. The reason why E. canadensis appears to be so common in children is unknown.

Cystic echinococcosis (CE) is a parasitic zoonosis with a cosmopolitan distribution. Molecular analysis was carried out on 43 hepatic CE cysts from 43 cases confirmed histopathologically at the NCP, Mongolia. Molecular analysis revealed two species, Echinococcus canadensis and Echinococcus granulosus s.s. Twenty three haplotypes of the cox1 gene were identified. All pediatric cases (n = 18) were by E. canadensis. Sixteen of 39 CE cases with data on age, sex and province of residence were from UB (41.0%), and 13 of these 16 cases were caused by E. canadensis (81.3%). Among the 13 cases from UB, nine were children (69.2%). A total of 31 serum samples from these 43 cases were analyzed for antibody response to rAgB with 22 (71.0%) samples positive by ELISA to rAgB. Thirteen of 20 E. canadensis (G6/7) (65%) and nine of 10 E. granulosus s.s. (90%) were seropositive. CE cases by E. granulosus s.s. showed a higher absorbance value than cases by E. canadensis (p  =  0.0137). This is the first study to evaluate age distribution of and antibody responses to rAgB in CE cases caused by the two species in Mongolia. It remains unknown why E. canadensis appears to be more common in pediatric cases.

Management of serology negative human hepatic hydatidosis (caused by Echinococcus granulosus) in a young woman from Bangladesh in a resource-rich setting: A case report

Human cystic echinococcosis (hydatidosis) is a parasitic zoonosis with almost complete worldwide distribution. Echinococcus granulosus, the dog tapeworm, causes hydatidosis which accounts for 95% of human echinococcosis. Although this tapeworm is found in dogs as a definitive host and a number of intermediate hosts, humans are often infected from close contact with infected dogs. Humans are not part of the parasitic lifecycle and serve as accidental hosts. Hydatidosis is an important consideration in the differential diagnosis of hepatic cysts in individuals from endemic areas. Clinicians should be aware of the long incubation period, the high frequency of negative serological tests, and the possibility of intraoperative evaluations of the cyst aspirate being non-diagnostic. We describe a case of serology negative hydatidosis that came to medical attention as an incidental finding in a young woman from Bangladesh. The patient underwent imaging and was then started on albendazole. After several weeks of albendazole, the cyst was punctured, aspirated, injected with hypertonic saline, re-aspirated, and then fully excised. Diagnosis was confirmed by microscopic evaluation of the cyst aspirate. Serological tests for hydatidosis may be negative in patients with early disease and thus should not be used to rule out this disease. Consideration of this diagnosis allows clinicians to avoid the catastrophic spillage of cystic contents risking an anaphylactic reaction, which might prove fatal. Despite World Health Organization hydatidosis staging being based on ultrasound, radiologists in resource-rich setting may prefer MRI in the management and staging of cystic echinococcosis.

Nothing is perfect! Trouble-shooting in immunological and molecular studies of cestode infections

This personal review focuses on ways to approach and overcome some of the more common issues encountered while studying cestode zoonoses. The information presented here is based on the author's own experiences with immunological and molecular approaches for the detection of these parasites. There are many incongruities between immunological and molecular studies due to biased work. Nothing is perfect. Indirect approaches using either immunological, or even molecular tools, are limited without confirmation from direct evidence of infection. The dilemma of whether developing countries should develop their own diagnostic tests or rely on commercially available kits is also discussed.

Proteomic characterization of larval and adult developmental stages in Echinococcus granulosus reveals novel insight into host-parasite interactions

Cystic hydatid disease is an important zoonosis caused by Echinococcus granulosus infection. The expression profiles of its parasitic life stages and host-Echinococcus interactions remain to be elucidated. Here, we identified 157 adult and 1588 protoscolex proteins (1610 in all), including 1290 novel identifications. Paramyosins and an antigen B (AgB) were the dominant adult proteins. Dog proteins (30) identified in adults indicated diminished local inflammation caused by adult infection. The protoscolex expresses proteins that have been reported to be antigens in other parasites, such as 6-phosphofructokinase and calcineurin B. Pathway analyses suggested that E. granulosus uses both aerobic and anaerobic carbohydrate metabolisms to generate ATP. E. granulosus expresses proteins involved in synthesis and metabolism of lipids or steroids. At least 339 of 390 sheep proteins identified in protoscolex were novel identifications not seen in previous analyses. IgGs and lambda light chains were the most abundant antibody species. Sheep proteins were enriched for detoxification pathways, implying that host detoxification effects play a central role during host-parasite interactions. Our study provides valuable data on E. granulosus expression characteristics, allowing novel insights into the molecular mechanisms involved in host-parasite interactions.

BIOLOGICAL SIGNIFICANCE

In this study, the Echinococcus granulosus adult worm proteome was analyzed for the first time. The protein identification of E. granulosus protoscoleces was extended dramatically. We also identified the most abundant host proteins co-purified with Echinococcus. The results provide useful information pertaining to the molecular mechanisms behind host-Echinococcus interaction and Echinococcus biology. This data also increases the potential for identifying vaccine candidates and new therapeutic targets, and may aid in the development of protein probes for selective and sensitive diagnosis of echinococcosis infection. In addition, the data collected here represents a valuable proteomic resource for subsequent genome annotation.