Diagnostic epitope variability within Taenia solium 8 kDa antigen family: implications for cysticercosis immunodetection

Accuracy of immunological tests on serum and urine for diagnosis of Taenia solium neurocysticercosis: A systematic review

BACKGROUND

Taenia solium neurocysticercosis is a zoonotic neglected tropical disease, for which adequate diagnostic management is paramount, especially in patients with active cysts for whom improved and timely management could prove beneficial. Immunodiagnosis can potentially partially mitigate the necessity for neuroimaging, shortening the diagnostic -and treatment- pathway. An up-to-date review of immunological test performance is however lacking.

METHODOLOGY/PRINCIPAL FINDINGS

Searches were performed in PubMed, EMBASE, Web of Science, and Scopus (up to January 2024), with included records fitting the review scope, i.e. accuracy evaluation of an antibody-/or antigen-detecting immunological test, using serum or urine of humans confirmed via reference standard (i.e. neuroimaging or surgery/biopsy). Record data was assessed, with classification of descriptive data on cyst localization and stage according to a developed confidence scale, and with selection of tests evaluated on a sufficiently high sample size. A QUADAS-2 risk of bias assessment was performed. After screening, 169 records were included for data collection, with 53 records-corresponding to 123 tests- selected for analysis. Absence of data and large data heterogeneity complicated result interpretation. The lentil lectin-bound glycoprotein enzyme-linked immunoelectrotranfser blot seems to fulfill high accuracy standards regarding detection of parenchymal active multiple cysts; also antigen-detecting tests on serum and urine performed well, additionally in detection of extraparenchymal neurocysticercosis. A novel multi-antigen print immunoassay is highly promising, with sensitivity for detection of extraparenchymal and parenchymal active single and multiple cysts of 100.0%, and specificity of 98.5%. Point-of-care tests showed promising results, however require further evaluation in targeted resource-poor settings.

CONCLUSIONS/SIGNIFICANCE

The review highlights the importance of transparent and unambiguous data reporting. With promising immunological tests in development, the challenge before usage in targeted settings will be to perform large-scale evaluations whilst holding into account both optimized test performance and ease of use. Accessibility to validated tests and feasibility of implementation should also be considered.

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.

Comparison of different PCR amplification targets for molecular diagnosis of Strongyloides stercoralis

Molecular techniques are an alternative for the diagnosis of strongyloidiasis, produced by Strongyloides stercoralis. However, it is necessary to determine the best amplification target for the populations of this parasite present in a geographical area and standardize a polymerase chain reaction (PCR) protocol for its detection. The objectives of this work were the comparison of different PCR targets for molecular detection of S. stercoralis and the standardization of a PCR protocol for the selected target with the best diagnostic results. DNA extraction was performed from parasite larvae by saline precipitation. Three amplification targets of the genes encoding ribosomal RNA 18S (18S rDNA) and 5.8S (5.8S rDNA) and cytochrome oxidase 1 (COX1) of S. stercoralis were compared, and the PCR reaction conditions for the best target were standardized (concentration of reagents and template DNA, hybridization temperature, and number of cycles). The analytical sensitivity and specificity of the technique were determined. DNA extraction by saline precipitation made it possible to obtain DNA of high purity and integrity. The ideal target was the 5.8S rDNA, since the 18S rDNA yielded non-reproducible results and COX1 never amplified under any condition tested. The optimal conditions for the 5.8S rDNA-PCR were: 1.5 mM MgCl2, 100 μM dNTPs, 0.4 μM primers, and 0.75 U DNA polymerase, using 35 cycles and a hybridization temperature of 60 °C. The analytical sensitivity of the PCR was 1 attogram of DNA, and the specificity was 100%. Consequently, the 5.8S rDNA was shown to be highly sensitive and specific for the detection of S. stercoralis DNA.

Regulation of DNA methylation on key parasitism genes of Cysticercus cellulosae revealed by integrative epigenomic-transcriptomic analyses

Background

The life cycle of Taenia solium is characterized by different stages of development, requiring various kinds of hosts that can appropriately harbor the eggs (proglottids), the oncospheres, the larvae and the adults. Similar to other metazoan pathogens, T. solium undergoes transcriptional and developmental regulation via epigenetics during its complex lifecycle and host interactions.

Result

In the present study, we integrated whole-genome bisulfite sequencing and RNA-seq technologies to characterize the genome-wide DNA methylation and its effect on transcription of Cysticercus cellulosae of T. solium. We confirm that the T. solium genome in the cysticercus stage is epigenetically modified by DNA methylation in a pattern similar to that of other invertebrate genomes, i.e., sparsely or moderately methylated. We also observed an enrichment of non-CpG methylation in defined genetic elements of the T. solium genome. Furthermore, an integrative analysis of both the transcriptome and the DNA methylome indicated a strong correlation between these two datasets, suggesting that gene expression might be tightly regulated by DNA methylation. Importantly, our data suggested that DNA methylation might play an important role in repressing key parasitism-related genes, including genes encoding excretion-secretion proteins, thereby raising the possibility of targeting DNA methylation processes as a useful strategy in therapeutics of cysticercosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41065-021-00195-9.

Characterization and evaluation of three new recombinant antigens of Taenia solium for the immunodiagnosis of cysticercosis

Cysticerci of Taenia solium cause cysticercosis, with neurocysticercosis (NCC) as the major pathology. Sensible and specific recombinant antigens would be an source of antigen for immunodiagnosis. The objective of this work was the molecular characterization and evaluation, of three news recombinant antigens (TsF78, TsP43 and TsC28), obtained by screening of a Taenia solium cDNA library. The three cDNA were analysed by bioinformatic programs, subcloned and expresed. The purified proteins were evaluated in ELISA using cyst fluid as control. TsF78 is filamina, TsP43 a peroxidase and TsC28 collagen XV. The sensitivity and specificity of the recombinant proteins were; TsF78 93.8 % and 95.0 %, TsP62 91.7 % and 93.3 %, TsC28 85.4 % and 93.3 %, respectively, while the cyst fluid showed a sensitivity of 87.5 % and a specificity of 76.7 %. Given its high sensitivity and specificity, the recombinant proteins TsF78 and TsP62 could be used in the diagnosis of cysticercosis.

Characterization of a novel cathepsin L-like protease from Taenia solium metacestodes for the immunodiagnosis of porcine cysticercosis

Porcine cysticercosis is an endemic parasitic disease caused by infection with Taenia solium that is found predominantly in developing countries. In order to aid in the development of simple diagnostic approaches, identification and characterization of potential new antigens for immunodiagnostic purposes is desired. The cysteine protease family has previously been found to have important immunodiagnostic properties. These proteases are expressed as zymogens which contain a signal peptide, pro-peptide, and an active domain. Subsequent catalytic cleavage of the pro-peptide converts these zymogens into enzymes. With the use of bioinformatic tools we identified an active domain of a novel cathepsin L-like cysteine protease (TsolCL) in the T. solium genome. The TsolCL gene includes 705 nucleotides (nt) within a single intron and a 633 nt exonic sequence encoding an active protein of 211 amino acids. Sequence alignment and phylogenetic analysis suggest that the TsolCL gene is closely related to genes found in Echinoccocus granulosus and E. multiloculars. In addition, TsolCL was found to have a 61.9%-99.0% similarity to other cathepsin L proteins found in other helminths and mammals. We cloned, expressed, purified, and characterized the recombinant active TsolCL (27 kDa) using the baculovirus-insect cell expression system. TsolCL showed cysteine protease enzymatic activity with the capacity to hydrolyze the Z-Phe-Arg-AMC substrate as well as bovine serum albumin. However, TsolCL was not able to hydrolyze human immunoglobulin. In addition, TsolCL has cathepsin L conserved amino acid residues in the catalytic site (Gln8, Cys14, His159, Asn179 and Trp181) and the motif GCNGG. Using ELISA, TsolCL was able to distinguish circulating IgG antibodies between healthy animals and naturally infected pigs with cysticercosis, showing a moderate sensitivity of 83.33% (40/48; 95% CI: [69.8%-92.5 %]), and a specificity of 83.78% (31/37; 95% CI: [67.9%-93.8%]). In conclusion, a novel cathepsin L-like cysteine protease from a T. solium metacestode was expressed successfully in Baculovirus system and was evaluated as a candidate antigen to diagnose porcine cysticercosis using the ELISA immunoassay.

A gel-free proteomic analysis of Taenia solium and Taenia crassiceps cysticerci vesicular extracts

The taeniasis/cysticercosis complex is a zoonosis caused by the presence of the parasite Taenia solium in humans. It is considered a neglected disease that causes serious public health and economic problems in developing countries. In humans, the most common locations for the larval form are the skeletal muscles, ocular system, and the central nervous system, which is the most clinically important. Several glycoproteins of T. solium and Taenia crassiceps cysticerci have been characterized and studied for their use in the immunodiagnosis of neurocysticercosis and/or the development of synthetic or recombinant vaccines against cysticercosis. The aim of this study was to perform a gel-free shotgun proteomic analysis to identify saline vesicular extract (SVE) proteins of T. solium and T. crassiceps cysticerci. After solubilization of the SVE with and without surfactant reagent and in-solution digestion, the proteins were analyzed by LC-MS/MS. Use of a surfactant resulted in a significantly higher number of proteins that were able to be identified by LC-MS/MS. Novel proteins were identified in T. solium and T. crassiceps SVE. The qualitative analysis revealed a total of 79 proteins in the Taenia species: 29 in T. solium alone, 11 in T. crassiceps alone, and 39 in both. These results are an important contribution to support future investigations and for establishing a Taenia proteomic profile to study candidate biomarkers involved in the diagnosis or pathogenesis of neurocysticercosis.

Present status of laboratory diagnosis of human taeniosis/cysticercosis in Europe

Human cysticercosis (CC) is a parasitic zoonosis caused by the larval stage (cyst) of the Taenia solium. Cysts can establish in the human central nervous system (neurocysticercosis, NCC) and other organs and tissues; they also develop in pigs, the natural intermediate host. Human taeniosis may be caused by T. solium, Taenia saginata and Taenia asiatica tapeworms; these infections are usually asymptomatic, but show a significant relevance as they perpetuate the parasites’ life cycle, and, in the case of T. solium, they are the origin of (N)CC. In European Union (EU) member states and associated countries, the occurrence of autochthonous T. solium cases is debated, and imported cases have significantly increased lately; the status of T. asiatica has been never reported, whereas T. saginata is prevalent and causes an economic impact due to condemned carcasses. Based on their effects on the EU society, the specific diagnosis of these pathologies is relevant for their prevention and control. The aims of this study were to know the diagnostic tests used in European laboratories for human taeniosis/cysticercosis by means of a questionnaire, to determine potential gaps in their detection, and to obtain preliminary data on the number of diagnosed taeniosis/CC cases.

Taenia solium metacestode preparation in rural areas of sub-Saharan Africa: a source for diagnosis and research on cysticercosis

BACKGROUND

Taenia solium metacestodes/cysts obtained from pig carcasses constitute a primary source for diagnostic tools used for the detection of human cysticercosis. Data on T. solium cyst preparation in Africa is still scarce but required to establish independent reference laboratories.

OBJECTIVES

The aim of the present study is a) to present the likely yield of T. solium cyst material by the use of two different preparation methods in the field and b) to investigate its suitability for immunodiagnosis of human cysticercosis.

METHODS

In Zambia, Uganda and Tanzania 670 pigs were screened for T. solium infection. Cysts were prepared by 'shaking method' and 'washing method'. Generated crude antigens were applied in a standard western blot assay.

RESULTS

46 out of 670 pigs (6.9%) were found positive for T. solium (Zambia: 12/367, 3.3%; Uganda: 11/217, 5.1%; Tanzania 23/86, 26.7%). Mean values of 77.7 ml whole cysts, 61.8 ml scolices/membranes and 10.9 ml cyst fluid were obtained per pig. Suitability of collected material for the use as crude antigen and molecular diagnostic techniques was demonstrated.

CONCLUSION

This study clearly shows that T. solium cyst preparation in African settings by simple field methods constitutes an effective way to obtain high quality material as source for diagnostic tools and research purposes.

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.