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

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.

Structural and Immunodiagnostic Characterization of Synthetic Antigen B Subunits From Echinococcus granulosus and Their Evaluation as Target Antigens for Cyst Viability Assessment

Background

Several tools have been proposed for serodiagnosis of cystic echinococcosis (CE), but none seems promising for cyst viability assessment. Antigens with stage-specific diagnostic value have been described, but few studies with well-characterized antigens and human serum samples have been performed. Antigen B (AgB) proteoforms hold promise as markers of viability, due to their differential stage-related expression and immunoreactivity.

Methods

Four AgB subunits (AgB1, AgB2, AgB3, AgB4) were synthesized and structurally characterized. Based on the preliminary evaluation of the subunits by western immunoblotting and enzyme-linked immunosorbent assay (ELISA), AgB1 and AgB2 were further tested in two ELISA setups and extensively validated on 422 human serum samples.

Results

All subunits showed a high degree of spontaneous oligomerization. Interacting residues within oligomers were identified, showing that both the N-terminal and C-terminal of each subunit are involved in homo-oligomer contact interfaces. No hetero-oligomer was identified. AgB1 and AgB2 ELISAs revealed different sensitivities relative to cyst stage. Of note, besides high specificity (97.2%), AgB1 revealed a higher sensitivity for active-transitional cysts (100% for CE1, 77.8% for CE2, 81.5% for CE3a, and 86.3% for CE3b) than for inactive cysts (41.7% for CE4 and 11.1% for CE5) and postsurgical patients (44%). Interestingly, 19 of 20 patients with spontaneously inactive cysts and 6 of 9 treated with albendazole >5 years earlier were negative on the AgB1 assay.

Conclusions

The structural characterization of subunits provides insights into the synthetic antigen conformation. The stage-related sensitivity of synthetic AgB1 holds promise as part of a multiantigen setting and deserves further longitudinal evaluation as marker of cyst viability.

Co-occurrence of swine cysticercosis due to Taenia solium and Taenia hydatigena in ethnic minority villages at the Thai-Myanmar border

As part of the international joint projects working towards the control of taeniosis/cysticercosis in Asia Pacific, epidemiological studies on Taenia solium cysticercosis have been carried out in high-incidence populations, such as minority groups in Thailand. To assess the epidemiology of cysticercotic infections in pigs in the hill-tribe minority villages (Karen) in Tak province, Thailand, we conducted serological screening and necropsies. The patterns of antibody response to T. solium antigens were then investigated using immunoblot assays. Of the 188 pig serum samples tested for antibody responses to partially purified low-molecular-weight antigens of T. solium cyst fluid, positive responses were detected in 37 samples (19.7%). Based on these results, 16 pigs (10 seropositive and 6 seronegative) were necropsied for investigation of cysticerci and intestinal parasites. All seropositive pigs were coinfected with both T. solium and Taenia hydatigena cysticerci, except one, which was infected with T. hydatigena alone. Three of the six seronegative pigs were confirmed to be infected with T. hydatigena. Pigs infected with T. solium showed much stronger antibody responses than those infected with T. hydatigena. Our results demonstrate the co-occurrence of two swine cysticercoses due to T. solium and T. hydatigena in the studied areas. This study also reveals the importance of direct confirmation of the presence of cysticerci by necropsy after serological screening. In addition to the prevalence of swine cysticercosis in these endemic areas, our findings also reveal potential implications for the development of serological diagnostic assays for swine cysticercosis.

The echinococcoses in Asia: The present situation

Human alveolar and cystic echinococcosis, caused by the accidental ingestion of eggs of the tapeworms Echinococcus multilocularis and Echinococcus granulosus sensu lato, respectively, are endemic in Asia. Various Echinococcus species are maintained in domesticated and/or wild mammals through predator-prey interactions. Molecular analysis is used to help differentiate infecting parasite species and genotypes, with the goal of better understanding parasite life cycles in order to aid in the planning and implementation of control programs. This paper discusses the various echinococcoses in Asia, with limited reference to neighboring areas, including parts of Central Asia, Russia, Europe and North America.

Needs of exploring the burden of recent onset seizures due to neurocysticercosis and challenges in southeast Asia focusing on scenario in Malaysia

Seizures due to neurocysticercosis (NCC) is a neglected human-to-human transmitted disorder and an emerging problem worldwide. A substantial portion of recent onset seizures is known to be attributed to NCC in Taenia solium (T. solium) endemic areas where populations which neither raise pigs nor eat pig meat are also at risk. High prevalence of NCC causing epilepsy has been reported in the underdeveloped areas of Southeast Asia (SEA) however, only fragmentary information on its incidence is available in countries like Malaysia. In Malaysia T. solium infection was previously thought to be infrequent due to Muslim population majority and the religious prohibition of consuming pork, but it is not totally absent. There is an evident lack of knowledge and awareness of the actual burden, routes of transmission, and the impact of NCC in this region. The problem is assumed to be more prevalent particularly in cities because of the frequent inflow of possibly T. solium infected individuals or carriers among those who migrate from neighboring endemic countries to Malaysia. The issue of imported cases that are likely to be emerging in Malaysia is highlighted here. An accurate quantification of regional burdens of epilepsy due to NCC in Malaysia is warranted considering the disease emergence in its neighboring countries. It is suggested that the importance of NCC be recognized through quantification of its burden, and also to collect epidemiological data for its subsequent elimination in line of World Health Organization's mission for control of cysticercosis as a neglected tropical disease. In this review the need as well as a strategy for neuro-care center screening of epilepsy cases, and various issues with possible explanations are discussed. It is also proposed that NCC be declared as a reportable disease which is one of the eradicable public health problems in SEA.

Cystic echinococcosis: Future perspectives of molecular epidemiology

Human cystic echinococcosis (CE) has been considered to be caused predominantly by Echinococcus granulosus sensu stricto (the dog-sheep strain). Molecular approaches on CE, however, have revealed that human cases are also commonly caused by another species, Echinococcus canadensis. All indices for classification and standardization of CE pathology including available images, epidemiology, diagnostics and treatment are currently based largely on a mixture of infections which include at least E. granulosus s.s. and E. canadensis. Involvement of other species of Echinococcus in CE including E. ortleppi or otherwise cryptic diversity demonstrated recently in Africa requires further elucidation. Molecular identification of the causative species in CE cases is essential for better understanding of pathogenesis and disease. This article stresses the importance of molecular species identification of human CE as a foundation for re-evaluation of evidence-based epidemiology.

Cysticercosis/taeniasis endemicity in Southeast Asia: Current status and control measures

The parasitic zoonoses cysticercosis/taeniasis is among the 17 major Neglected Tropical Diseases (NTDs) identified by the WHO as a focus for research and control. It is caused by a larval stage (cysticercus) infection of Taenia solium tapeworm in both humans and pigs. Cysticercosis occurs in many resource-poor countries, especially those with warm and mild climates in the regions of Latin America (LA), Asia and Sub-Saharan Africa (SSA). The prevalence of human cysticercosis is marked in those areas where individuals are traditionally keen to consume raw or insufficiently cooked pork and/or where the husbandry of pigs is improper. The worldwide burden of cysticercosis is unclear and notably, large-scale control initiatives are lacking in all regions. This review focuses on the current endemic status of cysticercosis caused by T. solium infection in both humans and pigs living in 13 Southeast Asian countries. We will also emphasize epidemiological data as well as prevention and control of human neurocysticercosis.

Serological validation of an alveolar echinococcosis rat model with a single hepatic lesion

Serology is important for the diagnosis and follow-up of human alveolar echinococcosis (AE). However, patient conditions are highly variable among those with AE, and antibody responses in serological follow-up have not been well-defined. We recently described a new AE rat model established by implantation of small AE tissue into a single arbitrary location in the liver; no metastasis and dissemination were observed. In the present study, we examined the serological characteristics in our rat model before and after surgical treatment. The results showed that antibody responses against crude antigens were increased at one month after transplantation and similar to those of other model animals. For the antigen Em18, antibody responses were slower in our rat model than in other animal models. After surgical resection, changes in antibody responses against Em18 were similar to those observed in human patients with AE. Because of the slow growth of lesions, establishment of a single hepatic lesion and patterns of antibody responses, our rat model may be useful for clarifying follow-up serodiagnoses in human AE and determining the mechanisms of multi-organ involvement by primary infection with oncospheres rather than metastasis.

Swine cysticercosis in the Karangasem district of Bali, Indonesia: An evaluation of serological screening methods

A serological assessment was undertaken on pigs from the Kubu and Abang sub-districts of Karangasem on the island of Bali, Indonesia, where earlier studies had detected patients with cysticercosis. Antigens purified from Taenia solium cyst fluid by cation-exchange chromatography were used to evaluate antibody responses in the pigs and the serological tests were also evaluated using sera from pigs experimentally infected with T. solium eggs. A total of 392 serum samples from naturally exposed pigs were tested using an ELISA that could be read based on both a colour change perceptible by the naked eye and an ELISA based on absorbance values. Twenty six (6.6%) pigs were found seropositive by the naked-eye ELISA and were categorized into three groups: strongly positive (absorbance values >0.8, n=6), moderately positive (absorbance values between 0.2 and 0.8, n=7), and weakly positive (absorbance values <0.2, n=13). Necropsies performed on 11 strongly and moderately positive pigs revealed that six strongly positive pigs were infected either solely with T. solium cysticerci (n=3), or co-infected with both T. solium and Taenia hydatigena (n=3). Four moderately positive pigs were infected solely with T. hydatigena. No cysticerci were found in one pig that was moderately positive by the naked-eye ELISA. Two experimentally infected pigs became antibody positive by 6 weeks post-infection, whereas eight control pigs remained negative. An additional 60 pigs slaughtered at authorized abattoirs on Bali were tested using the same ELISA. All 60 pigs were seronegative with no evidence of Taenia infection at necropsy. The results confirm the presence of porcine cysticercosis on Bali and, while the serological responses seen in T. solium infected animals were much stronger than those infected with T. hydatigena, the diagnostic antigens are clearly not species specific. Further studies are necessary to confirm if it is possible to draw a cut off line for differentiation of pig infected with T. solium from those infected with T. hydatigena.

Diagnostic Accuracy of Antigen 5-Based ELISAs for Human Cystic Echinococcosis

BACKGROUND

Clinical diagnosis and follow up of cystic echinococcosis (CE) are based on imaging complemented by serology. Several immunodiagnostic tests are commercially available, but the development of new tools is still needed to overcome the lack of standardization of the target antigen, generally consisting of a crude extract of Echinococcus granulosus hydatid cyst fluid. In a previous work, we described a chromatographic method for the preparation of a highly enriched Antigen 5 fraction from hydatid cyst fluid. The high reactivity of patient sera against this preparation prompted us to evaluate further this antigen for the serodiagnosis of CE on a larger cohort of samples.

METHODOLOGY/PRINCIPAL FINDINGS

A total of 327 sera from CE patients with heterogeneous conditions for cyst stage, cyst number, organ localization, drug therapy, and surgical intervention, together with 253 sera from healthy controls, were first analyzed by an ELISA based on the Ag5 preparation in two different experimental setups and, in parallel, by a commercial ELISA routinely used in clinical laboratories for CE serodiagnosis. The Ag5 ELISAs revealed different sensitivity (88.3% vs 95.3%) without significant differences in specificity (94.1% vs 92.5%), for the two setups, respectively. Moreover, possible relationships between the Ag5 ELISA absorbance results and clinical variables were investigated. Chi squared test, bivariate logistic regression and multiple regression analyses highlighted differences in the serology reactivity according to pharmacological treatment, cyst activity, and cyst number.

CONCLUSIONS/SIGNIFICANCE

The two Ag5 ELISAs revealed different performances depending on the setup. The good diagnostic sensitivity and the high reliability of the Ag5 preparation method make this antigen a promising candidate for the serodiagnosis of CE. Further studies will be needed to evaluate the ability of our test to provide useful information on specific CE clinical traits.

The present situation of echinococcoses in Mongolia

This review presents the historical and current situation of echinococcoses in Mongolia. Since the collapse of the Soviet Union in 1991, Mongolia's health surveillance infrastructure has been very poor, especially as it pertains to chronic diseases, including neglected zoonotic diseases (NZDs). Although there is anecdotal evidence of people dying from hepatic disease due to infection with the larval stage of Echinococcus spp., there are very few published reports. All confirmed cases of echinococcoses in Mongolia are from hospitals located in the capital city of Ulaanbaatar. Cases of cystic echinococcosis (CE), caused by either Echinococcus granulosus sensu stricto or Echinococcus canadensis are believed to be relatively common throughout Mongolia. In contrast, cases of alveolar echinococcosis (AE), caused by Echinococcus multilocularis, are believed to be rare. Recent wild-animal surveys have revealed that wolves (Canis lupus) are the major definitive hosts of E. canadensis, whereas both wolves and red foxes (Vulpes vulpes) are the primary definitive hosts of E. multilocularis. Although wild-animal surveys have begun to elucidate the transmission of Echinococcus spp. in Mongolia, there have yet to be large-scale studies conducted in domestic dogs and livestock. Therefore, further epidemiological studies, in addition to education-based control campaigns, are needed to help combat this NZD.

Recent advances and perspectives in molecular epidemiology of Taenia solium cysticercosis

Cysticercosis caused by accidental ingestion of eggs of Taenia solium is spreading all over the world through globalization and is one of the most neglected, neglected tropical diseases (NTDs) or neglected zoonotic diseases (NZDs). In the present study, the reason why T. solium cysticercosis has been neglected is discussed at first, and followed with an overview on the most recent advances and perspectives in molecular approaches for epidemiology of T. solium taeniasis/cysticercosis, since although taeniasis does not constitute recognized zoonoses, transmission and complete development are dependent on human definitive hosts. Main topics are discussions on (1) the two, Asian and Afro/American, genotypes of T. solium, (2) comparative analysis of mitochondrial (haploid) and nuclear (diploid) genes, and (3) the presence of hybrids of these two genotypes which indicates out-crossing of two genotypes in hermaphrodite tapeworms in Madagascar. Additional topics are on (4) the usefulness of phylogeographic analyses to discuss where the infection was acquired from, and (5) miscellaneous unsolved topics around these genetic diversity of T. solium.

The present situation and towards the prevention and control of neurocysticercosis on the tropical island, Bali, Indonesia

Neurocysticercosis (NCC), which is caused by accidental ingestion of eggs of the pork tapeworm, Taenia solium, was common in Bali, Indonesia until the early 1990s. However, improved education on hygiene and sanitation, a move to keeping pigs indoors, and improvement of economic and living conditions have substantially reduced the occurrence of NCC in Bali. Since 2011, T. solium tapeworm carriers (T. solium taeniasis) and heavily infected pigs and dogs have exclusively been detected from villages in mountainous regions of northeastern Bali where NCC and ocular cysticercosis (OCC) cases have also been identified. In response to this continued area of high infection, a one-day workshop was convened to discuss how to prevent and control this potentially lethal zoonotic parasitic infection in Bali. This review presents an overview of the current status of T. solium taeniasis and cysticercosis in Indonesia and proposes a strategy for the prevention and control of this zoonosis in Bali.

Unique MRI findings for differentiation of an early stage of hepatic alveolar echinococcosis

CT scan and ultrasonography images revealed two small uniformly low-density and hypoechoic lesions in the liver, respectively, 7 years after curative resection of rectal cancer, in a 74-year-old man. The area of the liver including the two lesions was segmentally resected. Two lesions were histopathologically confirmed as early but active stage alveolar echinococcosis (AE) caused by accidental ingestion of eggs of the fox tapeworm, Echinococcus multilocularis. This case is very unique and rare, since early stage hepatic AE cases have only accidentally been confirmed from cases in which malignant hepatic tumours were suspected, and because two independent AE lesions were detected. Abdominal MRI showed two isointense tumour lesions with small areas of high-signal intensity in their centres on T2-weighted images. MRI findings appear to reflect the macroscopic view and microscopic findings of early stage AE with active cyst in the centre of each hepatic lesion well.

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.

Taeniases and cysticercosis in Indonesia: past and present situations

The main aim of this study is to overview the past and present situations of human taeniases and cysticercosis in Indonesia and including future perspectives. Through joint projects from 1996, we have confirmed the occurrence ofTaenia saginata(beef tapeworm) in Bali, ofTaenia solium(pork tapeworm) mainly in Papua and sporadically in Bali, and ofTaenia asiaticain North Sumatra. These taeniases were caused through eating uncooked pork and pig viscera forT. soliumandT. asiatica, respectively, and beef forT. saginata. The distribution of these tapeworms in Indonesia is basically highly restricted by the traditional cultural and religious backgrounds in each island.T. saginatais relatively common in Bali although people consume pork ‘lawar’more than beef ‘lawar’. Taeniases due toT. saginataorT. asiaticaandT. soliumand cysticercosis due toT. soliumhave also been sporadically reported in some other islands. Among these species,T. soliumis exceptional since humans can be infected not only by larval stages (cysticerci) in pork but also by eggs released from human tapeworm carriers. Cysticercosis has been confirmed in Indonesia in humans, pigs and even dogs.