Serologic diagnosis of human Taenia solium cysticercosis by using recombinant and synthetic antigens in QuickELISA™

Production and evaluation of a new set of recombinant antigens for the serological diagnosis of human cysticercosis

Human cysticercosis caused by Taenia soliun (T. soliun) is endemic in certain areas of Latin America, Asia and Sub-Saharan Africa. Neurocysticercosis (NCC) is mainly diagnosed by neuroimaging, which, in most cases, is unavailable in endemic areas. Due to their high sensitivity and specificity, serological tests such as enzyme-linked immunosorbent assay (ELISA) and Western blot (WB) based on the glycosylated fraction of the cyst CS50 are widely used for the detection of the anti-cysticercus IgG antibodies despite their significant cost and the need of cysticercus material. Given their cost-effectivess and simplicity, immunoassays based on recombinant proteins could provide new alternatives for human cysticercosis diagnosis: such tests would be aimed at screening those people living in remote areas who need further examination. To date, however, no test using recombinant antigens is commercially available. Herein, five recombinant proteins (R14, R18, R93.1, R914.1, and R915.2) were produced, three of which (R93.1, R914.1, and R915.2) were newly identified from the cyst fluid. Evaluation of the diagnostic performance of these recombinant antigens by ELISA was done using sera from 200 epileptic and non-epileptic individuals in comparison with the WB-CS50 as the reference serological method. Recombinant proteins-based ELISA showed a level of diagnostic performance that is inferior than the reference serological method, but similar to that of the native antigen ELISA for human cysticercosis (commonly used for screening). Further optimization of expression conditions is still needed in order to improve proteins solubility and enhance diagnostic performance for human cysticercosis detection. However, this preliminary evaluation of the recombinant antigens has shown their potential valuable use for screening cysticercosis in patients with epilepsy attending dispensaries in remote areas. Future studies should be conducted to evaluate our recombinant antigens in a large group of patients with different stages of NCC, and in correlation with imaging findings.

Multiantigen print immunoassay (MAPIA) for the diagnosis of neurocysticercosis: a single-center diagnostic optimization and accuracy study in Lima, Peru

Neurocysticercosis (NCC) is the most common helminthic infection of the human central nervous system. The antibody detection assay of choice is the enzyme-linked immunoelectrotransfer blot assay using lentil-lectin purified parasite antigens (LLGP-EITB, Western blot), an immunoassay with exceptional performance in clinical samples. However, its use is mainly restricted to a few research laboratories because the assay is labor-intensive and requires sophisticated equipment, expertise, and large amounts of parasite material for preparation of reagents. We report a new immunoprint assay (MAPIA) that overcomes most of these barriers. We initially compared the performance of five different antigen combinations in a subset of defined samples in the MAPIA format. After selecting the best-performing assay format (a combination of rGP50 + rT24H + sTs14 antigens), 148 archived serum samples were tested, including 40 from individuals with parenchymal NCC, 40 with subarachnoid NCC, and 68 healthy controls with no evidence of neurologic disease. MAPIA using three antigens (rGP50 + rT24H + sTs14) was highly sensitive and specific for detecting antibodies in NCC. It detected 39 out of 40 (97.5%) parenchymal NCC cases and 40/40 (100%) subarachnoid cases and was negative in 67 out of 68 (98.53%) negative samples. MAPIA using three recombinant and synthetic antigens is a simple and economical tool with a performance equivalent to the LLGP-EITB assay for the detection of specific antibodies to NCC. The MAPIA overcomes existing barriers to adoption of the EITG LLGP and is a candidate for worldwide use.

Triplex ELISA for Assessing Durability of Taenia solium Seropositivity after Neurocysticercosis Cure

Neurocysticercosis prevalence estimates often are based on serosurveys. However, assessments of Taenia solium seropositivity durability in patients with various neurocysticercosis types are lacking. We optimized a triplex serologic ELISA by using synthetic GP50, T24H, and Ts18var3 antigens for T. solium. We used that assay to test sequential serologic responses over several years after neurocysticercosis cure in 46 patients, 9 each with parenchymal or ventricular neurocysticercosis and 28 with subarachnoid disease. Triplex results were concordant with 98% of positive and 100% of negative enzyme-linked immunoelectrotransfer blots. Eight years after neurocysticercosis cure, 11.1% of patients with parenchymal, 47.3% with subarachnoid, and 41.7% with ventricular disease were still seropositive. Median time to seroreversion after cure in this cohort in a T. solium nonendemic area was 2 years for parenchymal disease, 4 years for ventricular disease, and 8 years for subarachnoid disease. Our findings can inform epidemiologic models that rely on serosurveys to estimate disease burden.

A recombinant monoclonal-based Taenia antigen assay that reflects disease activity in extra-parenchymal neurocysticercosis

BACKGROUND

Antigen tests for diagnosis and disease monitoring in some types of neurocysticercosis (NCC) are useful but access to testing has been limited by availability of proprietary reagents and/or kits.

METHODS/PRINCIPAL FINDINGS

Three previously identified IgM-secreting hybridomas whose IgM products demonstrated specificity to Taenia solium underwent variable heavy and light chain sequencing and isotype conversion to mouse IgG. Screening of these recombinantly expressed IgG anti-Ts hybridomas, identified one (TsG10) with the highest affinity to crude Taenia antigen. TsG10 was then used as a capture antibody in a sandwich antigen detection immunoassay in combination with either a high titer polyclonal anti-Ts antibody or with biotinylated TsG10 (termed TsG10*bt). Using serum, plasma, and CSF samples from patients with active NCC and those from NCC-uninfected patients, ROC curve analyses demonstrated that the TsG10-TsG10-*bt assay achieved a 98% sensitivity and 100% specificity in detecting samples known to be antigen positive and outperformed the polyclonal based assay (sensitivity of 93% with 100% specificity). By comparing levels of Ts antigen (Ag) in paired CSF (n = 10) or plasma/serum (n = 19) samples from well-characterized patients with extra-parenchymal NCC early in infection and at the time of definitive cure, all but 2 (1 from CSF and 1 from plasma) became undetectable. There was a high degree of correlation (r = 0.98) between the Ag levels detected by this new assay and levels found by a commercial assay. Pilot studies indicate that this antigen can be detected in the urine of patients with active NCC.

CONCLUSIONS/SIGNIFICANCE

A newly developed recombinant monoclonal antibody-based Ts Ag detection immunoassay is extremely sensitive in the detection of extra-parenchymal NCC and can be used to monitor the success of treatment in the CSF, serum/plasma and urine. The ability to produce recombinant TsG10 at scale should enable use of this antigen detection immunoassay wherever NCC is endemic.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov Identifiers: NCT00001205 - & NCT00001645.

CDC-supported epilepsy surveillance and epidemiologic studies: A review of progress since 1994

To report progress, to identify gaps, and to plan epilepsy surveillance and research activities more effectively, the Centers for Disease Control and Prevention (CDC) Epilepsy Program has summarized findings from selected CDC-supported surveillance and epidemiologic studies about epilepsy from 1994 through 2019. We identified publications supported by CDC funding and publications conducted by the CDC Epilepsy Program alone or with partners. We included only epilepsy surveillance and epidemiologic studies focusing on epilepsy burden, epilepsy-related outcomes, and healthcare utilization. We describe the findings of these studies in the following order: 1)prevalence; 2)incidence; 3)epilepsy-related outcomes by selected demographic characteristics; 4)cysticercosis or neurocysticercosis (NCC); 5)traumatic brain injury (TBI); 6)comorbidity; 7)mortality; 8)access to care; 9)quality of care; and 10) cost. We have characterized these findings in relation to the scope of the first three domains of the 2012 Institute of Medicine report on epilepsy and its relevant first four recommendations. From 1994 through 2019, 76 publications on epilepsy-related epidemiologic and surveillance studies were identified. Over the past 25 years, CDC has expanded community, state, and national surveillance on epilepsy and supported epidemiologic studies by using multiple assessment methods and validated case-ascertainment criteria to identify epilepsy burden, epilepsy-related outcomes, and healthcare utilization in the general population or in population subgroups. Among identified research opportunities, studies on epilepsy incidence and risk factors, mortality, and cost are considered as important surveillance gaps. Other remaining gaps and suggested surveillance strategies are also proposed. Findings from this review may help epilepsy researchers and other stakeholders reference and prioritize future activities for epidemiologic and surveillance studies in epilepsy.

Feasibility of a point-of-care test based on quantum dots with a mobile phone reader for detection of antibody responses

We developed a novel and portable fluorescent sensor that integrates a lateral flow assay with a quantum dot (Qdots) label and a mobile phone reader for detection of specific antibodies in human serum. We evaluated the utility of this assay to test for antibodies to the Taenia solium rT24H antigen. It was a retrospective study by examining 112 positive human sera from patients with neurocysticercosis (NCC) including samples from patients with single viable cyst (n = 18), two or more viable cysts (n = 71), and subarachnoid (racemose) cysts (n = 23). These samples were collected from previous study subjects in Lima, Peru under an approved study protocol in Peru. The sera were made anonymous under a protocol approved by the CDC Institutional Review Board. Definitive diagnosis of the subject was established by computed-tomography and/or magnetic resonance imaging. To test the specificity of the assay, we evaluated a panel of serum samples obtained from patients with other infections (n = 24), and serum samples from persons in the United States and Egypt who had not traveled outside their country, and therefore are presumed negative for cysticercosis (n = 128). The assay specificity in the negative panel was 99% (95–100%) while assay sensitivity was 89% (79–95%) in NCC patients with two or more viable cysts. Our assay has performance characteristics similar to those of traditional platforms for the detection of NCC and shows promise as a mobile phone reader-based point-of-care test for antibody detection.

Point-of-care (POC) assays are important tools in control and elimination of parasitic diseases such as lymphatic filariasis, malaria, and leishmaniasis. Most POC assays use immunochromatographic and lateral flow assay principles with gold nanoparticles as a reporter. Assays based on gold nanoparticles usually provide qualitative or semi-quantitative results and have relatively low sensitivity. However, other reporter alternatives are available, including quantum dots (Qdots), up-converting phosphor nanoparticles, and superparamagnetic particles. We developed a Qdots-based test in a lateral flow assay format with a mobile phone reader to detect antibody responses, using neurocysticercosis (NCC) as a disease model, and found that the performance is similar to the traditional platform for detecting antibody responses in subjects with NCC. The incorporation of the mobile phone reader offers the advantage of portability and adaptability for use in areas where laboratories are not immediately accessible. This novel POC assay with mobile phone reader is a feasible option for antibody responses detection.

Progress on the development of rapid diagnostic tests for foodborne neglected zoonotic helminthiases: A systematic review

BACKGROUND

Foodborne Neglected Zoonotic Helminths (FNZH) are parasites of both economic and public health importance. They include Taenia solium, Echinococcus granulosus sensu lato, Echinococcus multilocularis and Foodborne trematodes (FBT). FNZH are earmarked for major interventions for control, elimination and eradication. This systematic review highlights the progress towards development of rapid tests for the diagnosis of FNZH since 2010 when they were listed as neglected tropical diseases.

METHODOLOGY

A systematic search was conducted in three databases, World of Science, Embase and PubMed using the same search phrase. The search produced 480 hits. Three studies from back referencing were included. Only 22 of these met the inclusion criteria. Data was extracted from these and presented qualitatively.

RESULTS

Twenty-five rapid diagnostic tests were found to have been developed since 2010, eight for diagnosis of T. solium infections, eight for echinococcosis and nine for FBT infections. The rapid tests for diagnosing T. solium infections included six antibody detecting and two antigen detecting tests. They constitute a combination among them, with some tests providing qualitative, others quantitative results. Similarly, seven out of the eight rapid tests developed for Echinococcus infections were antibody detecting tests save for one loop mediated isothermal amplification test. All of them were qualitative tests. For FBT infections, nine rapid tests were described; two antibody and one nucleic acid detecting test for diagnosis of Fascioliasis; three nucleic acid detecting tests for Opisthorchiasis; one antibody detecting test for Paragonimiasis; and for Clonorchiasis, one antibody and one nucleic acid detecting test. The FBT infection rapid tests were all qualitative in nature. Most of these tests have not undergone field evaluation in endemic areas where they will be used most.

CONCLUSION

This review describes the development and evaluation of rapid diagnostic tests, while highlighting the need for in depth validations of the tools to determine how well they can perform in endemic areas.

Laboratory Diagnosis of Neurocysticercosis (Taenia solium)

Neurocysticercosis accounts for approximately 30% of all epilepsy cases in most developing countries. The immunodiagnosis of cysticercosis is complex and strongly influenced by the course of infection, the disease burden, the cyst location, and the immune response of the host. The main approach to immunodiagnosis should thus be to evaluate whether the serological results are consistent with the diagnosis suggested by imaging. Antibody detection is performed using lentil lectin-purified parasite antigens in an enzyme-linked immunoelectrotransfer blot format, while antigen detection uses a monoclonal antibody-based enzyme-linked immunosorbent assay (ELISA). Promising new assay configurations have been developed for the detection of both antibody and antigen, including assays based on synthetic or recombinant antigens that may reduce costs and improve assay reproducibility and multiplex bead-based assays that may provide simultaneous quantitative results for several target antigens or antibodies.

Evaluating the Recombinant T24H Enzyme-Linked Immunoelectrotransfer Blot Assay for the Diagnosis of Neurocysticercosis in a Panel of Samples from a Large Community-Based Randomized Control Trial in 60 Villages in Burkina Faso

Current guidelines for the diagnosis of neurocysticercosis (NCC) recommend the use of the lentil lectin-bound glycoprotein enzyme-linked immunoelectrotransfer blot assay (LLGP-EITB) as the reference standard for serological testing. In response to the drawbacks involved with the use of the LLGP-EITB, a recombinant T24H antigen (rT24H) EITB assay was developed, with promising results. However, the test has yet to be evaluated among individuals from sub-Saharan Africa (SSA). The aim of the present study was to investigate the performance of the rT24H EITB assay for the detection of NCC cases in a panel of serum samples (N = 366, of which 173 patients presented with epileptic seizures and/or severe chronic headaches, and 193 matched manifestation-free participants) collected as part of a large community-based trial in Burkina Faso. A perfect agreement between the rT24H EITB and the native gp24 (and its homodimer, gp42) LLGP-EITB was found (kappa value of 1.0). Furthermore, among patients with the neurological manifestations of interest who underwent a computed tomography scan, the rT24H EITB and native antigen LLGP-EITB had a comparable ability to correctly identify NCC cases with multiple viable (rT24H: sensitivity: 80.0%), single viable (66.7%), and calcified/degenerating cysts only (25.0%), albeit for multiple viable and calcified cysts, the rT24H estimated sensitivity seemed lower, but more uncertain, than previously reported. The rT24H EITB specificity was high (98.2%) and in line with previous studies. This study confirms the value of the recombinant rT24H EITB as an alternative to the native antigen LLGP-EITB for the diagnosis of NCC in a SSA community setting.

Low sensitivity and frequent cross-reactions in commercially available antibody detection ELISA assays for Taenia solium cysticercosis

OBJECTIVE

To evaluate the diagnostic performance of two commercially available ELISA kits, Novalisa^® and Ridascreen^® , for the detection of antibodies to Taenia solium, compared to serological diagnosis of neurocysticercosis (NCC) by LLGP-EITB (electro-immunotransfer blot assay using lentil-lectin purified glycoprotein antigens).

METHODS

Archive serum samples from patients with viable NCC (n = 45) or resolved, calcified NCC (n = 45), as well as sera from patients with other cestode parasites (hymenolepiasis, n = 45 and cystic hydatid disease, n = 45), were evaluated for cysticercosis antibody detection using two ELISA kits, Novalisa^® and Ridascreen^® . All NCC samples had previously tested positive, and all samples from heterologous infections were negative on LLGP-EITB for cysticercosis. Positive rates were calculated by kit and sample group and compared between the two kits.

RESULTS

Compared to LLGP-EITB, the sensitivity of both ELISA assays to detect specific antibodies in patients with viable NCC was low (44.4% and 22.2%), and for calcified NCC, it was only 6.7% and 4.5%. Sera from patients with cystic hydatid disease were highly cross-reactive in both ELISA assays (38/45, 84.4%; and 25/45, 55.6%). Sera from patients with hymenolepiasis cross-reacted in five cases in one of the assays (11.1%) and in only one sample with the second assay (2.2%).

CONCLUSIONS

The performance of Novalisa^® and Ridascreen^® was poor. Antibody ELISA detection cannot be recommended for the diagnosis of neurocysticercosis.

Comparison of T24H-his, GST-T24H and GST-Ts8B2 recombinant antigens in western blot, ELISA and multiplex bead-based assay for diagnosis of neurocysticercosis

Background

Currently, the reference standard assay for the serodiagnosis of neurocysticercosis (NCC) is the lentil lectin-bound glycoproteins/enzyme-linked immunoelectrotransfer blot (LLGP-EITB). The main disadvantage of this technique is the complexity of obtaining and purifying the LLGP extract. This could be solved by replacement with highly specific recombinant antigens from Taenia solium. Based on previous studies, we selected and produced the recombinant Ts8B2 and T24H proteins and applied them to three diagnostic techniques: western blot (WB), enzyme-linked immunosorbent assay (ELISA) and the multiplex bead-based assay (MBA).

Methods

The Ts8B2 and T24H cDNA sequences were expressed in a prokaryotic system and the corresponding expression products purified; three recombinant proteins were further characterized: T24H-his, GST-T24H and GST-Ts8B2. The proteins on WB, ELISA and MBA were tested against 149 sera from patients with NCC confirmed by brain imaging, 40 sera from patients with other parasitic diseases, and 131 sera from US. individuals without evidence of neurocysticercosis (clinical/serological/brain imaging). The sensitivity and specificity of each antigen by WB were calculated by counting the number of true positive, false positive, true negative and false negative results. Using the receiver operating characteristic (ROC) curves, the cut-off values for the ELISA and MBA were established as well as the sensitivity and specificity of each assay.

Results

All three antigens showed a high sensitivity on WB in active NCC cases with two or more viable cysts and low sensitivity for cases with single viable cyst or calcified lesions and inactive NCC. WB showed the highest specificity and sensitivity out of the three diagnostic techniques. The recombinant T24H-his was the best diagnostic reagent in WB (100% sensitivity, 99.4% specificity), exhibiting similar results to the LLGP-EITB, against the same panel of NCC sera. The GST-T24H antigen worked better than the others in ELISA and MBA protocols (88.3 and 96.1% sensitivity, respectively and 96.5% specificity).

Conclusions

The sensitivity and specificity that we obtained were similar to results from a previous study using a similar recombinant antigen (rT24H), suggesting that recombinant antigens may be good alternatives to crude extracts in a variety of diagnostic techniques. Furthermore, these antigens can be applied in the development of point-of-care tests which would be useful in NCC field studies.

GP50 as a promising early diagnostic antigen for Taenia multiceps infection in goats by indirect ELISA

Background

Coenurosis is caused by coenurus, the metacestode of Taenia multiceps, which mainly parasitizes the brain and spinal cord of cattle, sheep and goats. To date, no widely-approved methods are available to identify early coenurus infection.

Methods

In this study, we identified a full-length cDNA that encodes GP50 (TmGP50) from the transcriptome of T. multiceps, and then cloned and expressed in E. coli. The native proteins in adult stage and coenurus were located via immunofluorescence assays, while the potential of recombinant TmGP50 protein (rTmGP50) for indirect ELISA-based serodiagnostics was assessed using native goat sera. In addition, we orally infected 20 goats with mature T. multiceps eggs. Praziquantel (10%) was given to 10 of the goats 45 days post-infection (p.i.). Blood samples were collected for 17 weeks p.i. from the 20 goats and anti-rTmGP50 antibodies were evaluated using the indirect ELISA established here.

Results

The TmGP50 contains an 897 bp open reading frame, in which signal sequence resides in 1 ~ 48 sites and mature polypeptide consists of 282 amino acid residues. Immunofluorescence staining showed that native TmGP50 was localized to the microthrix and parenchymatous zone of the adult parasite and coenurus, and the coenurus cystic wall. The indirect ELISA based on rTmGP50 exhibited a sensitivity of 95.0% and a specificity of 92.6% when detecting GP50 antibodies in sera of naturally infected goats and sheep. In goats experimentally infected with T. multiceps, anti-TmGP50 antibody was detectable from 2 to 17 weeks p.i. in the control group, while the antibody fell below the cut-off value about 3 weeks after praziquantel treatment.

Conclusion

Our results indicate that recombinant TmGP50 is a suitable early diagnostic antigen for coenurus infection in goats.

Taenia solium Taeniasis and Cysticercosis in Southeast Asia

Human taeniasis/cysticercosis caused by the pork tapeworm Taenia solium has been identified as a potentially eradicable disease by the International Task Force for Disease Eradication of the World Health Organization. In southeast Asia, T. solium taeniasis/cysticercosis is considered one of the major neglected tropical diseases afflicting the region. In the last few decades, a considerable effort has been invested toward establishing the epidemiology and burden of disease in several southeast Asian countries. Moreover, further evidence is emerging as to understanding the dynamics of disease transmission and cultural, political, and socioeconomic factors influencing the success of control and eradication efforts within the region. However, despite major collaborations by several champion groups, advances have been slow and little remains known about the complete epidemiology of taeniasis/cysticercosis and the barriers to programmatic success. This review article aims to address the above issues with a further focus on the challenges to control and eradicate taeniasis/cysticercosis within the southeast Asia region.

Differential antigenic protein recovery from Taenia solium cyst tissues using several detergents

Human and porcine cysticercosis is caused by the larval stage of the flatworm Taenia solium (Cestoda). The protein extracts of T. solium cysts are complex mixtures including cyst's and host proteins. Little is known about the influence of using different detergents in the efficiency of solubilization-extraction of these proteins, including relevant antigens. Here, we describe the use of CHAPS, ASB-14 and Triton X-100, alone or in combination in the extraction buffers, as a strategy to notably increase the recovery of proteins that are usually left aside in insoluble fractions of cysts. Using buffer with CHAPS alone, 315 protein spots were detected through 2D-PAGE. A total of 255 and 258 spots were detected using buffers with Triton X-100 or ASB-14, respectively. More protein spots were detected when detergents were combined, i.e., 2% CHAPS, 1% Triton X-100 and 1% ASB-14 allowed detection of up to 368 spots. Our results indicated that insoluble fractions of T. solium cysts were rich in antigens, including several glycoproteins that were sensitive to metaperiodate treatment. Host proteins, a common component in protein extracts of cysts, were present in larger amounts in soluble than insoluble fractions of cysts proteins. Finally, antigens present in the insoluble fraction were more appropriate as a source of antigens for diagnostic procedures.

Worm Infections in Children

• On the basis of research evidence, worm infections are important global child health conditions causing chronic disability that lasts from childhood into adulthood (Table 1). (2)(3) Evidence Quality: B • On the basis of research evidence, the major worm infections found in developing countries include ascariasis, trichuriasis, hookworm infection, and schistosomiasis; toxocariasis, enterobiasis, and cysticercosis are also found in poor regions of North America and Europe. (4)(9)(13) Evidence Quality: B • On the basis of expert consensus, children and adolescents are often vulnerable to acquiring large numbers of worms, ie, high-intensity infections (Fig 1)(21)(22)(23) Evidence Quality: D • On the basis of expert consensus and research evidence, moderate and heavy worm burdens cause increased morbidity because of growth and intellectual stunting in children and adolescents. Many of these effects may result from helminth-induced malnutrition. (21)(22)(23) Evidence Quality: C • On the basis of expert consensus and research evidence, worm infections are also commonly associated with eosinophilia. (48) (49) Evidence Quality: B • On the basis of research evidence as well as consensus, helminthes can cause inflammation in the lung (asthma), gastrointestinal tract (enteritis and colitis), liver (hepatitis and fibrosis), and urogenital tract. (7)(21)(22)(23)(27)(28)(40)(41)(43) Evidence Quality: B • On the basis of research evidence, microscopy techniques for diagnosis of worm infections in children often exhibit suboptimal sensitivities and specificities, necessitating new or improved diagnostic modalities such as polymerase chain reaction. (54)(55) Evidence Quality: A • On the basis of research evidence and expert consensus, mass drug administration (“preventive chemotherapy”) has becomea standard practice for ministries of health in low- and middle-income countries to control intestinal helminth infections and schistosomiasis. (67)(68) Evidence Quality: B.

Taenia solium metacestode fasciclin-like protein is reactive with sera of chronic neurocysticercosis

OBJECTIVES

Neurocysticercosis (NC), an infection of the central nervous system with Taenia solium metacestodes (TsM), invokes a formidable neurological disease. A bundle of antigens is applicable for serodiagnosis of active cases, while they demonstrate fairly low reactivity against sera of chronic NC. Identification of sensitive biomarkers for chronic NC is critical for appropriate management of patients.

METHODS

Proteome analysis revealed several isoforms of 65- and 83-kDa TsM fasciclin-like proteins (TsMFas) to be highly reactive with sera of chronic NC. A cDNA encoding one of the 83-kDa TsMFas (TsMFas1) was isolated from a cDNA library. We expressed a recombinant protein (rTsMFas1) and evaluated its diagnostic potential employing sera from chronic NC (n = 80), tissue-invasive cestodiases (n = 169) and trematodiases (n = 80) and those of normal controls (n = 50).

RESULTS

Secretory TsMFas1 was composed of 766 amino acid polypeptide and harboured fasciclin and fasciclin-superfamily domains. The protein was constitutively expressed in metacestode and adult stages, with preferential locality in the scolex. Bacterially expressed rTsMFas1 exhibited 78.8% sensitivity (63/80 cases) and 93% specificity (278/299 samples) in diagnosing chronic NC. Some cross-reactivity was observed with sera of cystic echinococcosis (10/56, 17.8%) and sparganosis (4/50, 8%). Positive and negative predictive values were 75% and 95.5%, respectively.

CONCLUSION

TsM fasciclin-like protein may be useful for differential diagnosis of chronic NC in clinical settings, especially where both NC and other infectious cerebral granulomatoses are prevalent.

Recombinant protein- and synthetic peptide-based immunoblot test for diagnosis of neurocysticercosis

One of the most well-characterized tests for diagnosing neurocysticercosis (NCC) is the enzyme-linked immunoelectrotransfer blot (EITB) assay developed at the CDC, which uses lentil lectin-bound glycoproteins (LLGP) extracted from Taenia solium cysticerci. Although the test is very reliable, the purification process for the LLGP antigens has been difficult to transfer to other laboratories because of the need for expensive equipment and technical expertise. To develop a simpler assay, we previously purified and cloned the diagnostic glycoproteins in the LLGP fraction. In this study, we evaluated three representative recombinant or synthetic antigens from the LLGP fraction, individually and in different combinations, using an immunoblot assay (recombinant EITB). Using a panel of 249 confirmed NCC-positive and 401 negative blood serum samples, the sensitivity of the recombinant EITB assay was determined to be 99% and the specificity was 99% for diagnosing NCC. We also tested a panel of 239 confirmed NCC-positive serum samples in Lima, Peru, and found similar results. Overall, our data show that the performance characteristics of the recombinant EITB assay are comparable to those of the LLGP-EITB assay. This new recombinant- and synthetic antigen-based assay is sustainable and can be easily transferred to other laboratories in the United States and throughout the world.

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.

Diagnostic criteria for neurocysticercosis, revisited

Diagnosis of neurocysticercosis (NCC) can be a challenge. Clinical manifestations are non-specific, most neuroimaging findings are non-pathognomonic, and some serologic tests have low sensitivity or specificity. A set of diagnostic criteria was proposed in 2001 to avoid the over diagnosis of NCC that occurs in epidemiologic surveys, and to help clinicians evaluating patients with suspected NCC. The set included four stratified categories of criteria, including: (1) absolute: histological demonstration of cysticerci, cystic lesions showing the scolex on neuroimaging studies, and direct visualization of subretinal parasites by fundoscopic examination; (2) major: lesions highly suggestive of NCC on neuroimaging studies, positive serum enzyme-linked immunoelectrotransfer blot (EITB) for the detection of anticysticercal antibodies, resolution of intracranial cystic lesions after cysticidal drug therapy, and spontaneous resolution of single enhancing lesions; (3) minor: lesions compatible with NCC on neuroimaging studies, suggestive clinical manifestations, positive cerebrospinal fluid (CSF) ELISA for detection of anticysticercal antibodies or cysticercal antigens, and cysticercosis outside the nervous system; and (4) epidemiological: evidence of a household contact with Taenia solium infection, individuals coming from or living in cysticercosis endemic areas, and history of travel to disease-endemic areas. Interpretation of these criteria permits two degrees of diagnostic certainty: (1) definitive diagnosis, in patients who have one absolute criterion or in those who have two major plus one minor and one epidemiological criteria; and (2) probable diagnosis, in patients who have one major plus two minor criteria, in those who have one major plus one minor and one epidemiological criteria, and in those who have three minor plus one epidemiological criteria. After 10 years of usage, this set has been proved useful in both, field studies, and hospital settings. Recent advances in neuroimaging and immune diagnostic methods have enhanced its accuracy for the diagnosis of NCC.

Immunological and molecular diagnosis of cysticercosis

Cysticercosis, the infection with the larval stage of Taenia solium, is a cause of neurological symptoms including seizures, affecting the quality of life of patients and their families. Diagnosis focuses on brain imaging and serological tests are mostly used as confirmatory tools. Most cases, however, occur in poor endemic areas, where both kinds of diagnostic tools are poorly available. Development of point of care diagnostic tests is one of the most important priorities for cysticercosis researches today. The ideal point of care test would require detection of viable cysticercosis and hopefully identify cases with severe or progressive forms of neurocysticercosis, leading to referral of the patient for specialized medical attention. This manuscript describes the evolution of the serological diagnosis of cysticercosis over time, and the characteristics of the most common currently available tools, their advantages and disadvantages, and their potential use in future diagnostic tests.

Serodiagnosis of human neurocysticercosis using antigenic components of Taenia solium metacestodes derived from the unbound fraction from jacalin affinity chromatography

The aim of the present study was to analyse Taenia solium metacestode antigens that were derived from the unbound fraction of jacalin affinity chromatography and subsequent tert-octylphenoxy poly (oxyethylene) ethanol Triton X-114 (TX-114) partitioning in the diagnosis of human neurocysticercosis (NCC). Immunoassays were designed to detect T. solium-specific IgG antibodies by ELISA and immunoblot. Serum samples were collected from 132 individuals who were categorised as follows: 40 had NCC, 62 presented Taenia spp or other parasitic diseases and 30 were healthy individuals. The jacalin-unbound (J unbound ) fraction presented higher sensitivity and specificity rates than the jacalin-bound fraction and only this fraction was subjected to subsequent TX-114 partitioning, resulting in detergent (DJ unbound ) and aqueous (AJ unbound ) fractions. The ELISA sensitivity and specificity were 85% and 84.8% for J unbound , 92.5% and 93.5% for DJ unbound and 82.5% and 82.6% for AJ unbound . By immunoblot, the DJ unbound fraction showed 100% sensitivity and specificity and only serum samples from patients with NCC recognised the 50-70 kDa T. solium-specific components. We conclude that the DJ unbound fraction can serve as a useful tool for the differential immunodiagnosis of NCC by immunoblot.

Immunodiagnosis of CNS parasitic infections

The nature of many parasitic infections of the central nervous system (CNS) requires immunodiagnosis to confirm presumptive diagnoses. The CNS is the primary site of parasite infection for some parasitic organisms and for others, neurological infection occurs only in immunocompromised hosts. Still other parasites cause ectopic infections of the CNS and occur very rarely. This review concentrates on laboratory diagnosis of diseases that are caused by parasites with a primary predilection for the CNS. Emphasis is placed on laboratory diagnostic methods that are used and suitable for clinical diagnosis, rather than a comprehensive review of all the experimental methods that have been reported in the literature. Immunodiagnosis is not appropriate for the diagnosis of all parasitic infections of the CNS; in those cases, alternative diagnostic methods are presented, but not discussed in detail. In some instances potential new antigens or methods are presented, particularly if adoption of these methods is expected in the near future.