Evaluation of the sensitivity and specificity of GST-tagged recombinant antigens 2B2t, Ag5t and DIPOL in ELISA for the diagnosis and follow up of patients with cystic echinococcosis

Ultrasound diagnosis of cystic echinococcosis: updates and implications for clinical management

The diagnosis of cystic echinococcosis (CE) is based on imaging. Detection of a focal lesion with morphological characteristics of Echinococcus granulosus sensu lato metacestode is the starting point for the diagnostic workup. In organs explorable with ultrasound (US), this is the method of choice for both aetiological diagnosis of CE and staging of the CE cyst. Staging in terms of lesion morphology is also needed when serology is added to the diagnostic workflow when imaging alone is inconclusive. Finally, staging guides the clinical management of uncomplicated CE, especially in the liver. This commentary provides an overview of the most up-to-date evidence backing the above-mentioned role of US in the diagnosis and clinical management of CE. Finally, we outline future perspectives for the improvement of CE diagnosis.

'No cyst, no echinococcosis': a scoping review update on the diagnosis of cystic echinococcosis after the issue of the WHO-IWGE Expert Consensus and current perspectives

PURPOSE OF REVIEW

In 2010, the WHO-Informal Working Group on Echinococcosis (IWGE) published an Expert Consensus on the diagnosis and treatment of echinococcal infections. We provide an update on the diagnosis of cystic echinococcosis through a scoping review of the literature published after the release of the WHO-IWGE document.

RECENT FINDINGS

Ultrasound accurately and reliably depicts the pathognomonic signs of cystic echinococcosis (CE) stages compared with other imaging techniques. Among these, T2-wighted MRI is to be preferred to computed tomography, which has poor performance for the etiological diagnosis of CE. A negative serology cannot exclude the diagnosis of CE, while a positive serology, applied after the visualization of a CE-compatible lesion, may confirm a CE diagnosis. Serology alone must not be used to define 'CE' nor as 'screening' tool for infection. Other imaging and laboratory techniques did not show clinically applicable performances.

SUMMARY

In the absence of a focal lesion compatible with a CE cyst, no diagnosis of CE should be attempted. There is urgent need to achieve univocal CE case definitions and consensus diagnostic algorithm, as well as standardization of diagnostic methods and issue of a Target Product Profile of CE diagnostics, as advocated by the WHO in the 2021-2030 roadmap for neglected tropical diseases (NTDs).

Characterization of the B-Cell Epitopes of Echinococcus granulosus Histones H4 and H2A Recognized by Sera From Patients With Liver Cysts

Cystic echinococcosis (CE) is a zoonotic disease worldwide distributed, caused by the cestode Echinococcus granulosus sensu lato (E. granulosus), with an incidence rate of 50/100,000 person/year and a high prevalence in humans of 5-10%. Serology has variable sensitivity and specificity and low predictive values. Antigens used are from the hydatid fluid and recombinant antigens have not demonstrated superiority over hydatid fluid. A cell line called EGPE was obtained from E. granulosus sensu lato G1 strain from bovine liver. Serum from CE patients recognizes protein extracts from EGPE cells with higher sensitivity than protein extracts from hydatid fluid. In the present study, EGPE cell protein extracts and supernatants from cell colonies were eluted from a protein G affinity column performed with sera from 11 CE patients. LC-MS/MS proteomic analysis of the eluted proteins identified four E. granulosus histones: one histone H4 in the cell extract and supernatant, one histone H2A only in the cell extract, and two histones H2A only in the supernatant. This differential distribution of histones could reflect different parasite viability stages regarding their role in gene transcription and silencing and could interact with host cells. Bioinformatics tools characterized the linear and conformational epitopes involved in antibody recognition. The three-dimensional structure of each histone was obtained by molecular modeling and validated by molecular dynamics simulation and PCR confirmed the presence of the epitopes in the parasite genome. The three histones H2A were very different and had a less conserved sequence than the histone H4. Comparison of the histones of E. granulosus with those of other organisms showed exclusive regions for E. granulosus. Since histones play a role in the host-parasite relationship they could be good candidates to improve the predictive value of serology in CE.

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.

Multiple-bead assay for the differential serodiagnosis of neglected human cestodiases: Neurocysticercosis and cystic echinococcosis

BACKGROUND

Neurocysticercosis (NCC), and cystic echinococcosis (CE) are two neglected diseases caused by cestodes, co-endemic in many areas of the world. Imaging studies and serological tests are used in the diagnosis of both parasitic diseases, but cross-reactions may confound the results of the latter. The novel multiplex bead-based assay with recombinant antigens has been reported to increases the diagnostic accuracy of serological techniques.

METHODOLOGY

We set-up an immunoassay based on the multiplex bead-based platform (MBA), using the rT24H (against Cysticercus cellulosae, causing cysticercosis) and r2B2t (against Echinococcus granulosus sensu lato, causing CE) recombinant antigens, for simultaneous and differential diagnosis of these infections. The antigens were tested on 356 sera from 151 patients with CE, 126 patients with NCC, and 79 individuals negative for both diseases. Specificity was calculated including sera from healthy donors, other neurological diseases and the respective NCC or CE sera counterpart. The diagnostic accuracy of this assay was compared with two commercial ELISA tests, Novalisa and Ridascreen, widely used in the routine diagnosis of cysticercosis and CE, respectively.

MAIN FINDINGS

For the diagnosis of NCC, sensitivity ranged from 57.94-63.49% for the rT24H-MBA, and 40.48-46.03% for Novalisa ELISA depending on exclusion or inclusion of sera having equivocal results on ELISA from the analysis; specificities ranged from 90.87-91.30% and 70.43-76.96%, respectively. AUC values of the ROC curve were 0.783 (rT24H) and 0.619 (Novalisa) (p-value < 0.001). For the diagnosis of CE, the sensitivity of the r2B2t-MBA ranged from 68.87-69.77% and of Ridascreen ELISA from 50.00-57.62%; specificities from 92.47-92.68% and from 74.15-80.98%, respectively. AUC values were 0.717 and 0.760, respectively.

CONCLUSIONS/SIGNIFICANCE

Overall, the recombinant antigens tested with the bead-based technology showed better diagnostic accuracy than the commercial assays, particularly for the diagnosis of NCC. The possibility of testing the same serum sample simultaneously for the presence of antibodies against both antigens is an added value particularly in seroprevalence studies for cysticercosis linked to control programs in endemic areas where these two parasites coexist.