Validation of a human-serum-based in vitro growth method for drug screening on juvenile development stages of Schistosoma mansoni

Abstract

Background Schistosomiasis affects over 200 million people worldwide but only praziquantel is available for treatment and control. Drug discovery is often based on phenotypic drug screening, involving different parasite stages retrieved from infected mice. Aiming to reduce animal use, we validated an in vitro growth method for juvenile Schistosoma mansoni for the purpose of drug sensitivity assays. Methodology/Principal findings We compared inter–batch variability of serum, worm size and organ development, gender distribution, and drug sensitivity between in vitro and in vivo grown worms over different life stages. In vitro developed S. mansoni in Hybridoma medium supplemented with 20% human serum were similar in size as in vivo worms until 28 days of incubation (males 1.4 ± 0.2 mm, females 1.1 ± 0.5 mm long). qPCR analysis revealed similar gender distribution both on newly transformed schistosomula and worms grown for 21 days. Worms developed in vitro and in vivo were similarly sensitive to praziquantel from 7 to 35 days of development with the exception of 21 days of development, where a slightly lower activity was observed for the in vitro grown worms (IC50: 0.54 μM in vitro, 0.14 μM in vivo 72 hours post-incubation). The evaluation of five additional drugs revealed a similar sensitivity at the 72 hours evaluation time point, with the exception of mefloquine, where we observed a 10-fold lower sensitivity on in vitro developed schistosomes when compared to in vivo grown (IC50: 4.43 μM in vitro, 0.48 μM in vivo). Conclusion A large number of juvenile S. mansoni worms can be grown in vitro, which show similar drug sensitivity, gender distribution, size and morphology as the worms recovered from rodents, supporting the use of this method in drug screening efforts.

Docking-Based Virtual Screening Enables Prioritizing Protein Kinase Inhibitors With In Vitro Phenotypic Activity Against Schistosoma mansoni

“…Schistosomiasis treatment relies mainly on PZQ, which despite having high potency against all species of Schistosoma spp., can present very low efficacy against some life stages of the worm such as 3 to 4-week old larva (Doenhoff et al, 2008), slowing down the eradication of schistosomiasis in endemic areas requiring repeated mass treatments in the same population (Fenwick and Webster, 2006;Melman et al, 2009;Crellen et al, 2016;da Silva et al, 2017). In the context of in vitro drug screening, a more recent publication showed that juvenile stages developed in vitro and in vivo have similar sensitivity to PZQ when treated in vitro (Buchter et al, 2021), which gives support to the methodology used here. Based on that, candidate lead compounds that show efficacy against schistosomula and/or at least one adult worm sex can be explored to support schistosomiasis treatment, while those that target only the larval stages can be developed for use in combination with PZQ.…”

The Transcriptome of Schistosoma mansoni Developing Eggs Reveals Key Mediators in Pathogenesis and Life Cycle Propagation

“…This is consistent with the low percentage (ranging from 10% to 15%) of IVLE that hatch fully viable and infectious miracidia ( 24 ). Recent improvements in culture conditions offer novel and informative approaches to sustain and study in vitro and ex vivo parasite development, including sexual differentiation and fecundity ( 48 – 50 ).…”

The transcriptome of Schistosoma mansoni developing eggs reveals key mediators in pathogenesis and life cycle propagation

“…This is consistent with the low percentage (ranging from 10% to 15%) of IVLE that hatch fully viable and infectious miracidia (Mann et al, 2011). Recent improvements on culture conditions offer novel and informative approaches to sustain and study in vitro and ex vivo parasite development, including sexual differentiation and fecundity (Wang et al, 2019;Anisuzzaman et al, 2021;Buchter et al, 2021).…”