Molecular Characterisation and Functions of Fis1 and PDCD6 Genes from Echinococcus granulosus

Silencing TUBB3 Expression Destroys the Tegument and Flame Cells of Echinococcus multilocularis Protoscoleces

Alveolar echinococcosis (AE), caused by infection with the larvae of Echinococcus multilocularis, is a neglected tropical disease and zoonosis that causes remarkable morbidity in humans and has economic importance in the livestock industry worldwide. The growth of this parasite resembles the invasion and proliferation of malignant tumours. Microtubules, especially the β-tubulin subunit in the exposed end, are the targets of many antitumour drugs. However, the role of TUBB3, which is the most studied isotype in solid tumours and is also a marker of biological aggressiveness associated with the modulation of tumour metastatic abilities in the growth and development of platyhelminths, is unknown. In this study, protoscoleces (PSCs) are cultivated in monophasic medium in vitro. Using electroporated short interfering RNA (siRNA), EmTUBB3 knockdown was performed with two EmTUBB3-specific siRNAs (siRNA-1 and siRNA-2). qRT–PCR was performed to detect the expression of TUBB3. PSCs viability and the evagination rate and number of body contractions were quantified under a light microscope. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to observe the ultra-morphological changes of the parasites. After siRNA interference, the EmTUBB3 expression in E. multilocularis PSCs was significantly reduced. Reduced viability, a decreased evagination rate and a decreased number of body contractions were also documented. In particular, shrinkage and roughness of the tegument were observed. Ultrastructural changes included marked damage to flame cells, cracked cilia structures enclosed in the cell body and ruptured microtubule structures. EmTUBB3 possibly plays a crucial role in tegument and flame cell integrity in E. multilocularis PSCs. Novel drugs targeting this specific beta-tubulin isotype in E. multilocularis are potential methods for disease control and deserve further attention.

Molecular and Functional Characterization of Inhibitor of Apoptosis Proteins (IAP, BIRP) in Echinococcus granulosus

The larval stage of Echinococcus granulosus sensu lato, resulting in cystic echinococcosis, a parasitic zoonosis, causes huge economic losses to the livestock industry and poses a threat to public health. Inhibitor of apoptosis proteins (IAPs) is a class of endogenous anti-apoptotic family, which plays a significant functional role in the regulation of organism’s development. Herein, to explore potential functions of IAPs in E. granulosus, two members of IAPs from E. granulosus (Eg-IAP and Eg-BIRP) were cloned, expressed, and molecularly characterized. Eg-IAP and Eg-BIRP encoded putative 331 and 168 residue proteins, respectively. Bioinformatic analysis showed that both proteins contained a type II BIR domain-the essential functional domain of IAPs. Fluorescence immunohistochemistry revealed that both proteins were ubiquitously localized in all life-cycle stages of E. granulosus. Our fluorescent quantitative PCR (RT-qPCR) results revealed relatively higher transcription levels of two Eg-IAPs in protoscoleces (PSCs) compared to the 18-day strobilated worms. We further used different concentrations of LCL161, a Smac-mimetic pan-IAPs inhibitor, to induce the apoptosis in PSCs in vitro, and revealed that the survival rate of PSCs and transcription levels of both genes were negatively correlated with the concentration of LCL161. While the results of light microscopy, transmission electron microscopy (TEM), and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay also showed a higher apoptotic rate in PSCs with the increasing concentrations of LCL161. Taken together, our findings provide the reasonable evidence that both Eg-IAP and Eg-BIRP have potential implication in critical anti-apoptotic roles during the development of E. granulosus.

Cloning, expression, characterization, and immunological properties of citrate synthase from Echinococcus granulosus

The larval stages of the tapeworm Echinococcus granulosus (Cestoda: Taeniidae) are the causative agent of cystic echinococcosis, one of the most important parasitic zoonoses worldwide. E. granulosus has a complete pathway for the tricarboxylic acid cycle (TCA), in which citrate synthase (CS) is the key enzyme. Here, we cloned and expressed CS from E. granulosus (Eg-CS) and report its molecular characterization. The localization of this protein during different developmental stages and mRNA expression patterns during H₂O₂ treatment were determined. We found that Eg-CS is a highly conserved protein, consisting of 466 amino acids. In western blotting assays, recombinant Eg-CS (rEg-CS) reacted with E. granulosus-positive sheep sera and anti-rEg-CS rabbit sera, indicating that Eg-CS has good antigenicity and immunoreactivity. Localization studies, performed using immunohistochemistry, showed that Eg-CS is ubiquitously expressed in the larva, germinal layer, and adult worm sections of E. granulosus. Eg-CS mRNA expression levels increased following H₂O₂ exposure. In conclusion, citrate synthase might be involved in the metabolic process in E. granulosus. An assessment of the serodiagnostic potential of rEg-CS based on indirect ELISA showed that, although sensitivity (93.55%) and specificity (80.49%) are high, cross-reactivity with other parasites precludes its use as a diagnostic antigen.