Echinococcosis is a serious helminthic zoonosis with a great impact on human health and livestock husbandry. However, the clinically used drugs (benzimidazoles) have a low cure rate, so alternative drugs are urgently needed. Currently, drug screenings for echinococcosis are mainly phenotype-based, and the efficiency of identifying active compounds is very low. With a pharmacophore model generated from the structures of active amino alcohols, we performed a virtual screening to discover novel compounds with anti-echinococcal activity. Sixty-two compounds from the virtual screening were tested on Echinococcus multilocularis protoscoleces, and 10 of these compounds were found to be active. After further evaluation of their cytotoxicity, S6 was selected along with two active amino alcohols for in vivo pharmacodynamic and pharmacokinetic studies. At the two tested doses (50 and 25 mg/kg), S6 inhibited the growth of E. multilocularis in mice (14.43 and 9.53%), but no significant difference between the treatment groups and control group was observed. Treatment with BTB4 and HT3 was shown to be ineffective. During the 28 days of treatment, the death of mice in the mebendazole, HT3, and BTB4 groups indicated their toxicity. The plasma concentration of S6 administered by both methods was very low, with the C max being only 1 ng/ml after oral administration and below the detection limit after intramuscular administration. In addition, the plasma concentrations of BTB4 and HT3 in vitro did not reach high enough levels to kill the parasites. The toxicities of these two amino alcohols indicated that they are not suitable for further development as anti-echinococcal drugs. However, further attempts should be made to increase the bioavailability of S6 and modify its structure. In this study, we demonstrate that pharmacophore-based virtual screenings with high drug identification efficiency could be used to find novel drugs for treating echinococcosis.

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Background/Aims: This study aims to predict the pro-angiogenic functions of monocytic-type myeloid-derived suppressor cells (M-MDSCs) derived from mice infected with Echinococcus granulosus. Methods: M-MDSCs were collected from Balb/c mice infected with E. granulosus and normal mice (control) and cultured in vitro. Human umbilical vein endothelial cells (HUVECs) were stimulated with the cell supernatant, and angiogenesis was investigated and analysed by the Angiogenesis module of the software NIH Image J. RNA was extracted from fresh isolated M-MDSCs and analysed with miRNA microarray; differentially expressed miRNAs and their potential functions were analysed through several bioinformatics tools. Finally, quantitative PCR was used to confirm the results of microarray analysis. Results: M-MDSCs from mice infected with E. granulosus could promote the formation of tubes from HUVECs in vitro. Moreover, vascular endothelial growth factor (VEGF) showed significantly high expression, whereas soluble fms-like tyrosine kinase-1 (sFlt-1) showed low expression at the transcriptional level in M-MDSCs from mice infected with E. granulosus. Microarray analysis of miRNAs showed that 28 miRNAs were differentially expressed in M-MDSCs from the two experimental mice groups, and 272 target genes were predicted using the microRNA databases TargetScan, PITA and microRNAorg. These target genes were mainly involved in the biological processes of intracellular protein transport, protein targeting to the lysosome and protein transport, and mainly located in the cytoplasm, neuronal cell body and membrane. Moreover, they were mainly involved in the molecular functions of protein binding, metal ion binding and SH3 domain binding. Further, the differentially expressed miRNAs were mainly enriched in the endocytosis, Wnt and axon guidance pathways, as well as the MAPK, focal adhesion, PI3K-Akt, cAMP, mTOR and TGF-β signalling pathways, which are linked to immunoregulation and angiogenesis based on the results of bioinformatics analysis with DIANA-miRPath 3.0. In addition, the expression of eight miRNAs was randomly verified by quantitative PCR independently in three mice infected with E. granulosus and three normal mice. Conclusion: M-MDSCs have a potential angiogenic role during E. granulosus infection, and miRNAs may play a role in the immune response and angiogenesis functions of M-MDSCs through regulation of the identified signalling pathways.

The aim of this study was to first evaluate the proangiogenic activity of polymorphonuclear myeloid-derived suppressor cells (PMN-MDSC) in mice infected with Echinococcus granulosus. PMN-MDSCs derived from experimentally infected mice were collected and cultured in vitro, and their effect on angiogenesis was investigated using a human umbilical vein endothelial cell (HUVEC) tube-formation assay stimulated with the supernatant by microscope and the Angiogenesis module of the software NIH Image J. In addition, the expression levels of several functional factors related to proangiogenic activity were analyzed. The results showed that vascular endothelial growth factor (VEGF) was increased in the serum from infected mice, and the PMN-MDSCs expressed VEGF directly. The culture supernatant from PMN-MDSCs significantly promoted HUVECs to form tubes. VEGF mRNA was higher and soluble fms-like tyrosine kinase-1 levels were lower, in PMN-MDSCs from infected mice than in those from control mice. In conclusion, host angiogenesis in mice infected with E. granulosus appeared to be promoted by PMN-MDSCs. Other specific angiogenic factors derived from PMN-MDSCs and parasites in the microenvironment of infection foci should be clarified in further studies, in order to provide more information for the prophylaxis and treatment of echinococcosis.

Echinococcosis, which causes a high disease burden and is of great public health significance, is caused by the larval stage of Echinococcus species. It has been suggested that tubulin is the target of benzimidazoles, the only drugs for the treatment of echinococcosis. This study evaluated the characteristics of tubulins from Echinococcus granulosus. The full-length cDNAs of E. granulosus α- and β-tubulin isoforms were cloned by reverse transcription PCR from protoscolex RNA. Then, these two tubulin isoforms (α9 and β4) were recombinantly expressed as insoluble inclusion bodies in Escherichia coli. Nickel affinity chromatography was used to purify and refold the contents of these inclusion bodies as active proteins. The polymerization of tubulins was monitored by UV spectrophotometry (A350) and confirmed by confocal microscopy and transmission electron microscopy (TEM). Nucleotide sequence analysis revealed that E. granulosus 1356 bp α9-tubulin and 1332 bp β4-tubulin encode corresponding proteins of 451 and 443 amino acids. The average yields of α9- and β4-tubulin were 2.0–3.0 mg/L and 3.5–5.0 mg/L of culture, respectively. Moreover, recombinant α9- and β4-tubulin were capable of polymerizing into microtubule-like structures under appropriate conditions in vitro. These recombinant tubulins could be helpful for screening anti-Echinococcus compounds targeting the tubulins of E. granulosus.