Drug inhibition of HDAC3 and epigenetic control of differentiation in Apicomplexa parasites

Plasmodium and Toxoplasma are parasites of major medical importance that belong to the Apicomplexa phylum of protozoa. These parasites transform into various stages during their life cycle and express a specific set of proteins at each stage. Although little is yet known of how gene expression is controlled in Apicomplexa, histone modifications, particularly acetylation, are emerging as key regulators of parasite differentiation and stage conversion. We investigated the anti-Apicomplexa effect of FR235222, a histone deacetylase inhibitor (HDACi). We show that FR235222 is active against a variety of Apicomplexa genera, including Plasmodium and Toxoplasma, and is more potent than other HDACi's such as trichostatin A and the clinically relevant compound pyrimethamine. We identify T. gondii HDAC3 (TgHDAC3) as the target of FR235222 in Toxoplasma tachyzoites and demonstrate the crucial role of the conserved and Apicomplexa HDAC-specific residue TgHDAC3 T99 in the inhibitory activity of the drug. We also show that FR235222 induces differentiation of the tachyzoite (replicative) into the bradyzoite (nonreplicative) stage. Additionally, via its anti-TgHDAC3 activity, FR235222 influences the expression of ∼370 genes, a third of which are stage-specifically expressed. These results identify FR235222 as a potent HDACi of Apicomplexa, and establish HDAC3 as a central regulator of gene expression and stage conversion in Toxoplasma and, likely, other Apicomplexa

Ex vivo activity of the ACT new components pyronaridine and piperaquine in comparison with conventional ACT drugs against isolates of Plasmodium falciparum

<p>Abstract</p> <p>Background</p> <p>The aim of the present work was to assess i) <it>ex vivo </it>activity of pyronaridine (PND) and piperaquine (PPQ), as new components of artemisinin-based combination therapy (ACT), to define susceptibility baseline, ii) their activities compared to other partner drugs, namely monodesethylamodiaquine (MDAQ), lumefantrine (LMF), mefloquine (MQ), artesunate (AS) and dihydroartemisinin (DHA) against 181 <it>Plasmodium falciparum </it>isolates from African countries, India and Thailand, and iii) <it>in vitro </it>cross-resistance with other quinoline drugs, chloroquine (CQ) or quinine (QN).</p> <p>Methods</p> <p>The susceptibility of the 181 <it>P. falciparum </it>isolates to the nine anti-malarial drugs was assessed using the standard 42-hours ³H-hypoxanthine uptake inhibition method.</p> <p>Results</p> <p>The IC₅₀values for PND ranged from 0.55 to 80.0 nM (geometric mean = 19.9 nM) and from 11.8 to 217.3 nM for PPQ (geometric mean = 66.8 nM). A significant positive correlation was shown between responses to PPQ and PND responses (<it>rho </it>= 0.46) and between PPQ and MDAQ (<it>rho </it>= 0.30). No significant correlation was shown between PPQ IC₅₀and responses to other anti-malarial drugs. A significant positive correlation was shown between responses to PND and MDAQ (<it>rho </it>= 0.37), PND and LMF (<it>rho </it>= 0.28), PND and QN (<it>rho </it>= 0.24), PND and AS (<it>rho </it>= 0.19), PND and DHA (<it>rho </it>= 0.18) and PND and CQ (<it>rho </it>= 0.16). All these coefficients of correlation are too low to suggest cross-resistance between PPQ or PND and the other drugs.</p> <p>Conclusions</p> <p>In this study, the excellent anti-malarial activity of PPQ and PND was confirmed. The absence of cross-resistance with quinolines and artemisinin derivatives is consistent with the efficacy of the combinations of PPQ and DHA or PND and AS in areas where parasites are resistant to conventional anti-malarial drugs.</p

LES HISTONES DEACETYLASES DE TOXOPLASMA GONDII : IMPLICATION DANS LA PHYSIOLOGIE DES APICOMPLEXES ET EVALUATION EN TANT QUE NOUVELLES CIBLES THERAPEUTIQUES

Histone modifications are major tools in the control of gene expression in Toxoplasma gondii and histone acetylation is directly involved in interconversion, a phenomenon which leads to parasite differentiation. We used an HDAC inhibitor, FR235222 as a tool to clarify the implication of histone acetylation in T. gondii. The sequencing of a mutagenised strain resistant to FR235222 allowed us to identify HDAC3 as the target enzyme of FR235222. The specific interaction domain between HDAC3 and FR235222 is conserved in all Apicomplexan parasite and is absent in other microorganisms and in human which explains the specificity of this compound against T. gondii and Plasmodium sp. FR235222 treated tachyzoites present hyperacetylated histone H4 and one third of those DNA region are coding for specific proteins belonging to the bradyzoite or sporozoite stage with an overexpression of these genes under FR235222 treatment. Antiparasitic activity of different HDACi was evaluated on the tachyzoite stage and on the cystic stage of the parasite, which appears to be the most important in human pathology. On tachyzoites, HDACi belonging to the tetrapeptide cyclic (TC) family exhibit the highest antiparasitic activity with an EC50 of 10 nM. Ex vivo T. gondii cysts treated with FR235222 or apicidine (another TC) were not able to infect mice when inoculated after 7 days of in vitro treatment. In conclusion, FR235222 inhibits specifically TgHDAC3 and displays a specific antiparasitic effect against Apicomplexan. Interfering on the natural course of the parasite cycle induces tachyzoites death in vitro and suppresses the infective power of the cysts in vivo. This work opens a new and promising therapeutic strategy in the field of Apicomplexan related diseases.Les modifications d'histones chez T. gondii représentent un des mécanismes majeurs pour contrôler la transcription des gènes et l'acétylation de certaines histones est impliquée dans le phénomène de différenciation parasitaire qu'est l'interconversion. Nous avons utilisé un inhibiteur d'histones déacétylases, FR235222, comme outil afin de clarifier l'implication de l'acétylation des histones chez T. gondii. Le séquençage d'un mutant résistant à la FR235222 a permis d'identifier TgHDAC3 comme cible préférentielle de cet iHDAC. Le domaine d'interaction est spécifique de la famille des Apicomplexa ce qui explique la sélectivité de cette molécule pour T. gondii et d'autres Apicomplexes dont Plasmodium sp. Sur tachyzoïtes traités, FR235222 augmente le taux d'acétylation des histones de certains gènes dont 1/3 est spécifique des stades sporozoïtes ou bradyzoïtes avec une surexpression de ces gènes après traitement par FR235222. L'activité antiparasitaire de différents iHDAC a été testée parallèlement sur les deux stades importants en pathologie humaine: le tachyzoïte et le kyste. Sur le tachyzoïte, seuls les tétrapeptides cycliques présentent une forte activité antiparasitaire avec des EC50 d'environ 10 nM. Les kystes ex-vivo traités avec FR235222, sont non infectants: absence de toxoplasmose chez la souris ré-inoculée avec ces kystes. En conclusion, FR235222 présente une activité dirigée contre l'HDAC3 de T. gondii et une spécificité envers les Apicomplexes. En interférant avec le cycle naturel du parasite, cette molécule induit la mort des tachyzoïtes in vitro et supprime le pouvoir infectant des kystes in vivo. Ce travail ouvre une voie prometteuse dans la stratégie thérapeutique des pathologies à Apicomplexes

Mise au point d une PCR en temps réel pour le diagnostic de kératites à Acanthamoeba spp

La kératite amibienne est une pathologie rare due à des amibes libres appartenant le plus souvent au genre Acanthamoeba. Son diagnostic clinique est difficile en raison de l absence de signes spécifiques. De sa précocité dépend une prise en charge adaptée précoce et un meilleur pronostic. Ceci souligne l importance de développer de nouveaux outils de diagnostic rapides et sensibles. Objectif : Améliorer le diagnostic des KA dans notre laboratoire, en mettant au point une PCR multiplex en temps réel permettant d amplifier simultanément la cible et la béta-globine humaine, qui informe sur la qualité du prélèvement. Matériel et méthode : Des cultures axéniques d A. polyphaga ont été utilisées pour l optimisation et la détermination des paramètres analytiques (spécificité, inhibiteurs potentiels, variabilités intra et inter essais). Deux prétraitements ont été comparés ainsi que deux méthodes d extraction. Ensuite, notre PCR a été évaluée sur une série prospective de grattages cornéens. Résultats : La sensibilité de notre technique, en associant un prétraitement par choc thermique et une extraction manuelle, est d une seule forme isolée par échantillon. Aucune amplification non spécifique n a été observée avec les 12 microorganismes bactériens ou fongiques extraits. Aucun des 14 collyres testés n est un inhibiteur total de l une ou l autre des PCR. Sur les 38 grattages, 7 n ont pas pu être interprétés du fait d une quantité insuffisante de prélèvements et 4 ont été considérés comme de vrais positifs. Conclusion : Notre PCR multiplex est un nouvel outil fiable, rapide et sensible qui permet, en une seule réaction, d amplifier la cible et d informer sur la qualité du prélèvement.GRENOBLE1-BU Médecine pharm. (385162101) / SudocSudocFranceF

Profile of GenMark’s ePlex® blood culture identification fungal pathogen panel

International audienceFungemia presents high morbi-mortality and thus rapid microbiological diagnosis may contribute to appropriate patient management. In the last decade, kits based on molecular technologies have become available and health care institutes are increasingly facing critical investment choices. Although all these tools aim to achieve rapid fungal detection and species identification, they display different inherent characteristics. Areas covered: Considering technologies allowing detection and identification of fungal species in a sepsis context, the market proposes either tests on positive blood culture or tests on patient's whole blood. In this review, the authors describe and compare the ePlex® Blood Culture Identification Fungal Pathogen (BCID-FP) test, a fully automated one-step single-use cartridge assay that has been designed to detect identify frequent or rare but emerging, fungal species, from positive blood culture. A comparison with the competing kits is provided. Expert commentaries: The ePlex BCID-FP test provides a diversified and rather relevant panel. Its easy-to-use cartridges allow flexible use around the clock. Nevertheless, prospective clinical studies assessing the time-to-result benefit on antifungal stewardship and on hospital length of stay are not available yet. New tools aim to benefit clinicians and patients, but they should be accompanied by supervision of result interpretation and adaptation of antifungal stewardship

Histone Deacetylases and Their Inhibition in Candida Species

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Can We Improve Antifungal Susceptibility Testing?

International audienceSystemic antifungal agents are increasingly used for prevention or treatment of invasive fungal infections, whose prognosis remains poor. At the same time, emergence of resistant or even multi-resistant strains is of concern as the antifungal arsenal is limited. Antifungal susceptibility testing (AFST) is therefore of key importance for patient management and antifungal stewardship. Current AFST methods, including reference and commercial types, are based on growth inhibition in the presence of an antifungal, in liquid or solid media. They usually enable Minimal Inhibitory Concentrations (MIC) to be determined with direct clinical application. However, they are limited by a high turnaround time (TAT). Several innovative methods are currently under development to improve AFST. Techniques based on MALDI-TOF are promising with short TAT, but still need extensive clinical validation. Flow cytometry and computed imaging techniques detecting cellular responses to antifungal stress other than growth inhibition are also of interest. Finally, molecular detection of mutations associated with antifungal resistance is an intriguing alternative to standard AFST, already used in routine microbiology labs for detection of azole resistance in Aspergillus and even directly from samples. It is still restricted to known mutations. The development of Next Generation Sequencing (NGS) and whole-genome approaches may overcome this limitation in the near future. While promising approaches are under development, they are not perfect and the ideal AFST technique (user-friendly, reproducible, low-cost, fast and accurate) still needs to be set up routinely in clinical laboratories

What are the respective host and parasite contributions to toxoplasmosis?

The toxoplasmosis pathogenesis mechanism is complex because parasite and host specificities are interrelated. Advances in fundamental research (including strain genotyping, analyzing the progeny from crosses of different strains and exploring the implication of epigenetic effects on the parasite) have contributed greatly to our current knowledge of this mechanism. At the same time new data on the clinical characteristics of the disease have come to light. For example, highly virulent strains have been isolated recently in immunocompetent patients, and some studies suggest that toxoplasmosis also might be implicated in brain disorders. These recent tools and discoveries are likely to cast new light on the pathogenicity of Toxoplasma parasites and provide the key to understanding this unique form of parasitism