Comparative analysis of stage specific gene regulation of apicomplexan parasites: Plasmodium falciparum and Toxoplasma gondii

In Vitro Biological Activity of Natural Products from the Endophytic Fungus Paraboeremia selaginellae against Toxoplasma gondii

Toxoplasma gondii is an apicomplexan pathogen able to infect a wide range of warm-blooded animals, including humans, leading to toxoplasmosis. Current treatments for toxoplasmosis are associated with severe side-effects and a lack efficacy to eradicate chronic infection. Thus, there is an urgent need for developing novel, highly efficient agents against toxoplasmosis with low toxicity. For decades, natural products have been a useful source of novel bioactive compounds for the treatment of infectious pathogens. In the present study, we isolated eight natural products from the crude extract of the endophytic fungus Paraboeremia selaginellae obtained from the leaves of the plant Philodendron monstera. The natural products were tested for inhibiting Toxoplasma gondii proliferation, and their cytotoxicity was evaluated in different human cell lines. Six natural products showed antitoxoplasma activity with low or no cytotoxicity in human cell lines. Together, these findings indicate that biphenyl ethers, bioxanthracenes, and 5S,6S-phomalactone from P. selaginellae are potential candidates for novel anti-toxoplasma drugs.

A synthetic promoter for multi-stage expression to probe complementary functions of Plasmodium adhesins

Gene expression of malaria parasites is mediated by the apicomplexan Apetala2 (ApiAP2) transcription factor family. Different ApiAP2s control gene expression at distinct stages in the complex life cycle of the parasite, ensuring timely expression of stage-specific genes. ApiAP2s recognize short cis-regulatory elements that are enriched in the upstream/promoter region of their target genes. This should, in principle, allow the generation of 'synthetic' promoters that drive gene expression at desired stages of the Plasmodium life cycle. Here we test this concept by combining cis-regulatory elements of two genes expressed successively within the mosquito part of the life cycle. Our tailored 'synthetic' promoters, named Spooki 1.0 and Spooki 2.0, activate gene expression in early and late mosquito stages, as shown by the expression of a fluorescent reporter. We used these promoters to address the specific functionality of two related adhesins that are exclusively expressed either during the early or late mosquito stage. By modifying the expression profile of both adhesins in absence of their counterpart we were able to test for complementary functions in gliding and invasion. We discuss the possible advantages and drawbacks of our approach.This article has an associated First Person interview with the first author of the paper.

mRNA export in the apicomplexan parasite Toxoplasma gondii: emerging divergent components of a crucial pathway

Control of gene expression is crucial for parasite survival and is the result of a series of processes that are regulated to permit fine-tuning of gene expression in response to biological changes during the life-cycle of apicomplexan parasites. Control of mRNA nuclear export is a key process in eukaryotic cells but is poorly understood in apicomplexan parasites. Here, we review recent knowledge regarding this process with an emphasis on T. gondii. We describe the presence of divergent orthologs and discuss structural and functional differences in export factors between apicomplexans and other eukaryotic lineages. Undoubtedly, the use of the CRISPR/Cas9 system in high throughput screenings associated with the discovery of mRNA nuclear export complexes by proteomic analysis will contribute to identify these divergent factors. Ligand-based or structure-based strategies may be applied to investigate the potential use of these proteins as targets for new antiprotozoal agents.

Proteases as regulators of pathogenesis: examples from the Apicomplexa

The diverse functional roles that proteases play in basic biological processes make them essential for virtually all organisms. Not surprisingly, proteolysis is also a critical process required for many aspects of pathogenesis. In particular, obligate intracellular parasites must precisely coordinate proteolytic events during their highly regulated life cycle inside multiple host cell environments. Advances in chemical, proteomic and genetic tools that can be applied to parasite biology have led to an increased understanding of the complex events centrally regulated by proteases. In this review, we outline recent advances in our knowledge of specific proteolytic enzymes in two medically relevant apicomplexan parasites: Plasmodium falciparum and Toxoplasma gondii. Efforts over the last decade have begun to provide a map of key proteotolyic events that are essential for both parasite survival and propagation inside host cells. These advances in our molecular understanding of proteolytic events involved in parasite pathogenesis provide a foundation for the validation of new networks and enzyme targets that could be exploited for therapeutic purposes. This article is part of a Special Issue entitled: Proteolysis 50 years after the discovery of lysosome.

Artemisinin reduces the level of antibodies to gliadin in schizophrenia

OBJECTIVE

To investigate if adjunctive artemisinin, an anti-malarial compound with in vivo activity against Toxoplasma gondii, reduces symptoms or antibodies in schizophrenia.

METHOD

N=66 outpatients with schizophrenia were randomized to receive 100mg of artemisinin twice a day or placebo for 10 weeks after a 2 week placebo run-in in addition to their usual psychiatric medications. Symptoms were assessed biweekly. Antibodies to toxoplasma and to gliadin, a food antigen, were assessed at the beginning and end of the trial.

RESULTS

A total of 57 participants (26 in the artemisinin arm and 31 in the placebo arm) completed the 12 weeks of the trial. The medication was well tolerated and there were no significant side effects associated with the treatment regimen. There was no significant difference in the change of positive, negative, general, or total PANSS symptoms between groups for all of the randomized patients or for just the completers. However, individuals in the artemisinin arm but not in the placebo arm had significant decreases in the levels of antibodies to gliadin (p<.0005, p>.2, respectively by paired t-test). Neither group had significant changes in antibodies to T. gondii.

CONCLUSIONS

The study did not demonstrate clinical benefit of adjunctive artemisinin for schizophrenia symptoms. The finding of reduced levels of antibodies to gliadin in the artemisinin group merits further study.