Identification of Myoferlin, a Potential Serodiagnostic Antigen of Clonorchiasis, via Immunoproteomic Analysis of Sera From Different Infection Periods and Excretory-Secretory Products of Clonorchis sinensis

A point-of-care testing assay for clonorchiasis using a EuNPs-CsTR1 fluorescent probe-based immunoassay

Clonorchis sinensis is one of the most important fish-borne zoonotic parasitic worms in humans, and is distributed in several countries with more than 15 million people infected globally. However, the lack of a point-of-care testing (POCT) method is still the critical barrier to effectively prevent clonorchiasis. With the application of novel fluorescent nanomaterials, the development of on-site testing methods with high signal enhancement can provide a simple, precise and inexpensive tool for disease detection. In this study, Eu-(III) nanoparticles (EuNPs) were used as indicative probes, combined with C. sinensis tandem repeat sequence 1 (CSTR1) antigen to capture specific antibodies. Afterward, the complex binds to mouse anti-human IgG immobilized on the test line (T-line) producing a fluorescent signal under UV light. The EuNPs-fluorescent immunoassay (EuNPs-FIA) was successfully constructed, allowing sample detection within 10 min. It enabled both qualitative determination with the naked eye under UV light and quantitative detection by scanning the fluorescence intensity on the test line and control line (C-line). A total of 133 clinical human sera (74 negative, 59 clonorchiasis, confirmed by conventional Kato-Katz (KK) methods and PCR via testing fecal samples corresponding to each serum sample) were used in this study. For qualitative analysis, the cut-off value of fluorescence for positive serum was 31.57 by testing 74 known negative human samples. The assay had no cross-reaction with other 9 parasite-infected sera, and could recognize the mixed infection sera of C. sinensis and other parasites. The sensitivity and specificity of EuNPs-FIA were both 100% compared with KK smear method. Taking advantage of its high precision and user-friendly procedure, the established EuNPs-FIA provides a powerful tool for the diagnosis and epidemiological survey of clonorchiasis.

A novel Trichinella spiralis serine proteinase disrupted gut epithelial barrier and mediated larval invasion through binding to RACK1 and activating MAPK/ERK1/2 pathway

BACKGROUND

Gut epithelium is the first natural barrier against Trichinella spiralis larval invasion, but the mechanism by which larval penetration of gut epithelium is not completely elucidated. Previous studies showed that proteases secreted by T. spiralis intestinal infective larvae (IIL) degraded tight junctions (TJs) proteins of gut epithelium and mediated larval invasion. A new T. spiralis serine proteinase (TsSPc) was identified in the IIL surface proteins and ES proteins, rTsSPc bound to the intestinal epithelial cell (IECs) and promoted larval invasion of IECs. The aim of this study was to characterize the interacted proteins of TsSPc and IECs, and to investigate the molecular mechanisms of TsSPc mediating larval invasion of gut mucosa.

METHODOLOGY/PRINCIPAL FINDING

IIFT results showed natural TsSPc was detected in infected murine intestine at 6, 12 hours post infection (hpi) and 3 dpi. The results of GST pull-down, mass spectrometry (MS) and Co-IP indicated that rTsSPc bound and interacted specifically with receptor for activated protein C kinase 1 (RACK1) in Caco-2 cells. rTsSPc did not directly hydrolyze the TJs proteins. qPCR and Western blot showed that rTsSPc up-regulated RACK1 expression, activated MAPK/ERK1/2 pathway, reduced the expression levels of gut TJs (occludin and claudin-1) and adherent protein E-cad, increased the paracellular permeability and damaged the integrity of intestinal epithelial barrier. Moreover, the RACK1 inhibitor HO and ERK1/2 pathway inhibitor PD98059 abolished the rTsSPc activating ERK1/2 pathway, they also inhibited and abrogated the rTsSPc down-regulating expression of occludin, claudin-1 and E-cad in Caco-2 monolayer and infected murine intestine, impeded larval invasion and improved intestinal epithelial integrity and barrier function, reduced intestinal worm burdens and alleviated intestinal inflammation.

CONCLUSIONS

rTsSPc bound to RACK1 receptor in gut epithelium, activated MAPK/ERK1/2 pathway, decreased the expression of gut epithelial TJs proteins and disrupted the epithelial integrity, consequently mediated T. spiralis larval invasion of gut epithelium. The results are valuable to understand T. spiralis invasion mechanism, and TsSPc might be regarded as a vaccine target against T. spiralis invasion and infection.

Diagnosis of Human Trematode Infections

Digenetic trematodes form a major group of human parasites, affecting a large number of humans, especially in endemic foci. Over 100 species have been reported infecting humans, including blood, lung, liver and intestinal parasites. Traditionally, trematode infections have been diagnosed by parasitological methods based on the detection and the identification of eggs in different clinical samples. However, this is complicated due to the morphological similarity between eggs of different trematode species and other factors such as lack of sensitivity or ectopic locations of the parasites. Moreover, the problem is currently aggravated by migratory flows, international travel, international trade of foods and changes in alimentary habits. Although efforts have been made for the development of immunological and molecular techniques, the detection of eggs through parasitological techniques remains as the gold standard for the diagnosis of trematodiases. In the present chapter, we review the current status of knowledge on diagnostic techniques used when examining feces, urine, and sputum and also analyze the most relevant characteristics used to identify eggs with a quick key for the identification of eggs.

A rapid and visual detection assay for Clonorchis sinensis based on recombinase polymerase amplification and lateral flow dipstick

BACKGROUND

Fish-borne zoonotic clonorchiasis, caused by Clonorchis sinensis, is an emerging public health problem in several countries with more than 15 million people infected globally. However, a lack of accurate point-of-care (POC) diagnostic tests in resource-limited areas is still a critical barrier to effective treatment and control of clonorchiasis. The development of the recombinase polymerase amplification(RPA) assay, a POC diagnostic test based on the amplification of pathogen DNA, has provided a new, simple and inexpensive tool for disease detection with high sensitivity and specificity.

METHODS

A novel RPA method was developed based on specific primers and probes, and combined with the dipstick, to allow for the rapid and intuitive detection of C. sinensis through the amplification of the mitochondrial cytochrome c oxidase subunit 1 (COX1) gene. The lower limit of detection for the combined RPA/lateral flow dipstick (RPA-LFD) assay was evaluated using dilutions of the target DNA sequence. Cross-reactivity was evaluated using genomic DNA from 10 additional control parasites. Forty human clinical stool samples were tested to verify its performance.

RESULTS

The evaluated primers designed from the C. sinensis COX1 region can be used to detect adult worms, metacercariae, and eggs at 39 °C within 20 min, and the results can be visually observed using the LFD. The detection limit of pathogen genomic DNA was as low as 10 fg, and the number of metacercaria(e) in fish and egg(s) in faeces were both as low as one. This improved the sensitivity of low-infection detection tremendously. The test is species-specific, and no other related control parasites were detected. In human stool samples with eggs per gram (EPG) > 50, the RPA-LFD assay was performed consistent with conventional Kato-Katz (KK) and PCR methods.

CONCLUSION

The established RPA-LFD assay provides a powerful tool for the diagnosis and epidemiological survey of C. sinensis from human and animal samples, and has important implications for the effective control of clonorchiasis.