Biomarkers in Leishmaniasis: From Basic Research to Clinical Application

Leishmania is an intracellular protozoan parasite and the etiological agent of a vector-borne disease known as leishmaniasis. This neglected tropical disease exhibits high morbidity and mortality putting at risk people from multiple countries worldwide. It is endemic in 97 countries and 700,000–1 million new cases are estimated to occur each year. Leishmaniasis management is very challenging, the symptoms are non-pathognomonic (in both human and canine populations) and the treatments are associated with significant toxicity. Therefore, the need for detection in symptomatic and asymptomatic hosts is important to tackle the dissemination of infection, increasing the need for highly specific biomarkers. In this complex the available disease biomarkers will be addressed in a retrospective manner, focusing on their development from laboratory to their direct use in clinical settings

Web semântica na Europeana: uma abordagem do padrão EDM

Objective. The Semantic Web and Linked Data emphasize on the reuse and linking of richly described resources on the Web. This principles fits the purpose of the Europeana Data Model (EDM), which is to make use of existing resource information as well as to support their enrichment by establishing new relationships between them. The objective of this study is to describe the semantic relationships included in the elements of the EDM, as well as to highlight the advantages of using this model to represent and retrieve information digitized culture on the Web and thus encourage the adoption of semantic methodologies in Brazilian projects.Method. This is a qualitative research, based on a descriptive-document method, regarding the family of EDM documents. First we have identified the concepts and technologies of the Semantic Web and Linked Data, then we analyze the descriptive memoir of the data model of Europeana. We detail the principles and development of EDM, with an emphasis on the semantic elements that support specific functions in Europeana.Results. We have identified the possibilities of connecting data from different institutions in order to complement and enrich the information of the records about a particular cultural heritage object.Conclusions. This study showed that the semantic structure of the EDM constitutes a reference to be followed for publication of data of national Linked Open Data projects to ensure the increasing interconnection of data, to increase the speed of the circulation of the information between the interested parties and accelerate new discoveries.Objetivo. La Web Semántica y los Datos Enlazados hacen hincapié en la reutilización y la vinculación de los recursos ricamente descritos en la Web. Estos principios se ajustan al propósito del Modelo de Datos de Europeana (EDM) de utilizar la información de los recursos existentes y apoyar su enriquecimiento estableciendo nuevas relaciones entre ellos. Así, el objetivo de este estudio es describir las relaciones semánticas incrustadas en los elementos de la EDM, destacando las ventajas de la utilización de este modelo para la recuperación de información en la Web y, de este modo, fomentar la adopción de metodologías semánticas en los proyectos brasileños.Método. Se trata de una investigación cualitativa de carácter descriptivo-documental, basada en la familia documental EDM. En primer lugar, el estudio identificó los conceptos y tecnologías de la web semántica y los datos enlazados, y a continuación analizó el memorial descriptivo del modelo de datos de Europeana. Se detallaron los principios y el desarrollo del EDM, haciendo hincapié en los elementos semánticos que modelan y apoyan la funcionalidad de Europeana.Resultados. Como resultado, se identificaron las posibilidades de conectar datos de diferentes instituciones, con el fin de enriquecer la información de los registros de un determinado objeto del patrimonio cultural. Conclusiones. Este estudio demostró, a través de las relaciones semánticas, que la estructura semántica de EDM constituye una referencia a seguir para la publicación de datos de proyectos nacionales en Linked Open Data, con el fin de garantizar la creciente interconexión de los datos, aumentar la velocidad de circulación de la información entre las partes interesadas y acelerar nuevos descubrimientos.Objetivo. A Web Semântica e o Linked Data enfatizam a reutilização e a ligação de recursos ricamente descritos na Web. Estes princípios ajustam-se ao propósito do Modelo de Dados da Europeana (EDM) de utilizar informações de recursos existentes e apoiar o seu enriquecimento por meio do estabelecimento de novas relações entre eles. Assim, o objetivo deste estudo é descrever as relações semânticas inseridas nos elementos do EDM, destacando as vantagens de uso desse modelo para recuperação da informação na Web e, dessa forma, incentivar a adoção de metodologias semânticas em projetos brasileiros.Método. Trata-se de uma pesquisa de natureza qualitativa do tipo descritiva-documental, baseada na família de documentos do EDM. Primeiramente o estudo identificou os conceitos e tecnologias da Web Semântica e Linked Data, em seguida, analisou o memorial descritivo do modelo de dados da Europeana. O EDM foi detalhado em seus princípios e desenvolvimento, com ênfase nos elementos semânticos que modelam e apoiam a funcionalidade da Europeana.Resultados. Como resultado foram identificadas as possibilidades de conexão dos dados de diferentes instituições, de forma a enriquecer as informações dos registros de um determinado objeto do patrimônio cultural.Conclusões. Este estudo mostrou, por meio das relações semânticas, que a estrutura semântica do EDM constitui-se em uma referência a ser seguida para publicação de dados de projetos nacionais no Linked Open Data, para garantir a interconexão cada vez maior de dados, aumentar a velocidade da circulação da informação entre os interessados e acelerar novas descobertas.   

Towards chemical validation of Leishmania infantum ribose 5-phosphate isomerase as a drug target

Funding from the European Community's Seventh Framework Programme under grant agreements No. 602773 (Project KINDRED) was received for all partners in this work. This work also received funds from FCT - Fundação para a Ciência e a Tecnologia/Ministério da Ciência, Tecnologia e Ensino Superior through the Research Unit No. 4293 and project POCI-01-0145-FEDER-031013 (PTDC/SAUPAR/31013/2017 to NS); Individual funding from FCT through SFRH/BD/133485/2017 (to MS) and CEECIND/02362/2017 (to JT).Neglected tropical diseases caused by kinetoplastid parasites (Trypanosoma brucei, Trypanosoma cruzi and Leishmania spp.) place a significant health and economic burden on developing nations worldwide. Current therapies are largely out-dated, inadequate and facing mounting drug resistance from the causative parasites. Thus, there is an urgent need for drug discovery and development. Target-led drug discovery approaches have focused on the identification of parasite enzymes catalysing essential biochemical processes, which significantly differ from equivalent proteins found in humans, thereby providing potentially exploitable therapeutic windows. One such target is ribose 5-phosphate isomerase B (RpiB), an enzyme involved in the non-oxidative branch of the pentose phosphate pathway, which catalyses the inter-conversion of D-ribose 5-phosphate and D-ribulose 5-phosphate. Although protozoan RpiB has been the focus of numerous targeted studies, compounds capable of selectively inhibiting this parasite enzyme have not been identified. Here, we present the results of a fragment library screening against Leishmania infantum RpiB, performed using thermal shift analysis. Hit fragments were shown to be effective inhibitors of LiRpiB in activity assays, and several were capable of selectively inhibiting parasite growth in vitro. These results support the identification of LiRpiB as a validated therapeutic target. The X-ray crystal structure of apo LiRpiB was also solved, permitting docking studies to assess how hit fragments might interact with LiRpiB to inhibit its activity. Overall, this work will guide structure-based development of LiRpiB inhibitors as anti-leishmanial agents.PostprintPeer reviewe

Chroman-4-One Derivatives Targeting Pteridine Reductase 1 and Showing Anti-Parasitic Activity

Flavonoids have previously been identified as antiparasitic agents and pteridine reductase 1 (PTR1) inhibitors. Herein, we focus our attention on the chroman-4-one scaffold. Three chroman-4-one analogues (1-3) of previously published chromen-4-one derivatives were synthesized and biologically evaluated against parasitic enzymes (Trypanosoma brucei PTR1-TbPTR1 and Leishmania major-LmPTR1) and parasites (Trypanosoma brucei and Leishmania infantum). A crystal structure of TbPTR1 in complex with compound 1 and the first crystal structures of LmPTR1-flavanone complexes (compounds 1 and 3) were solved. The inhibitory activity of the chroman-4-one and chromen-4-one derivatives was explained by comparison of observed and predicted binding modes of the compounds. Compound 1 showed activity both against the targeted enzymes and the parasites with a selectivity index greater than 7 and a low toxicity. Our results provide a basis for further scaffold optimization and structure-based drug design aimed at the identification of potent anti-trypanosomatidic compounds targeting multiple PTR1 variants

Profiling of Flavonol Derivatives for the Development of Antitrypanosomatidic Drugs

Flavonoids represent a potential source of new antitrypanosomatidic leads. Starting from a library of natural products, we combined target-based screening on pteridine reductase 1 with phenotypic screening on Trypanosoma brucei for hit identification. Flavonols were identified as hits, and a library of 16 derivatives was synthesized. Twelve compounds showed EC50 values against T. brucei below 10 \u3bcM. Four X-ray crystal structures and docking studies explained the observed structure-activity relationships. Compound 2 (3,6-dihydroxy-2-(3-hydroxyphenyl)-4H-chromen-4-one) was selected for pharmacokinetic studies. Encapsulation of compound 2 in PLGA nanoparticles or cyclodextrins resulted in lower in vitro toxicity when compared to the free compound. Combination studies with methotrexate revealed that compound 13 (3-hydroxy-6-methoxy-2-(4-methoxyphenyl)-4H-chromen-4-one) has the highest synergistic effect at concentration of 1.3 \u3bcM, 11.7-fold dose reduction index and no toxicity toward host cells. Our results provide the basis for further chemical modifications aimed at identifying novel antitrypanosomatidic agents showing higher potency toward PTR1 and increased metabolic stability

Exploiting the 2-Amino-1,3,4-thiadiazole Scaffold To Inhibit <i>Trypanosoma brucei </i>Pteridine Reductase in Support of Early-Stage Drug Discovery

Pteridine reductase-1 (PTR1) is a promising drug target for the treatment of trypanosomiasis. We investigated the potential of a previously identified class of thiadiazole inhibitors of Leishmania major PTR1 for activity against Trypanosoma brucei (Tb). We solved crystal structures of several TbPTR1-inhibitor complexes to guide the structure-based design of new thiadiazole derivatives. Subsequent synthesis and enzyme- and cell-based assays confirm new, mid-micromolar inhibitors of TbPTR1 with low toxicity. In particular, compound 4m, a biphenyl-thiadiazole-2,5-diamine with IC50 = 16 μM, was able to potentiate the antitrypanosomal activity of the dihydrofolate reductase inhibitor methotrexate (MTX) with a 4.1-fold decrease of the EC50 value. In addition, the antiparasitic activity of the combination of 4m and MTX was reversed by addition of folic acid. By adopting an efficient hit discovery platform, we demonstrate, using the 2-amino-1,3,4-thiadiazole scaffold, how a promising tool for the development of anti-T. brucei agents can be obtained

Accelerating Drug Discovery Efforts for Trypanosomatidic Infections Using an Integrated Transnational Academic Drug Discovery Platform

According to the World Health Organization, more than 1 billion people are at risk of or are affected by neglected tropical diseases. Examples of such diseases include trypanosomiasis, which causes sleeping sickness; leishmaniasis; and Chagas disease, all of which are prevalent in Africa, South America, and India. Our aim within the New Medicines for Trypanosomatidic Infections project was to use (1) synthetic and natural product libraries, (2) screening, and (3) a preclinical absorption, distribution, metabolism, and excretion\u2013toxicity (ADME-Tox) profiling platform to identify compounds that can enter the trypanosomatidic drug discovery value chain. The synthetic compound libraries originated from multiple scaffolds with known antiparasitic activity and natural products from the Hypha Discovery MycoDiverse natural products library. Our focus was first to employ target-based screening to identify inhibitors of the protozoan Trypanosoma brucei pteridine reductase 1 (TbPTR1) and second to use a Trypanosoma brucei phenotypic assay that made use of the T. brucei brucei parasite to identify compounds that inhibited cell growth and caused death. Some of the compounds underwent structure-activity relationship expansion and, when appropriate, were evaluated in a preclinical ADME-Tox assay panel. This preclinical platform has led to the identification of lead-like compounds as well as validated hits in the trypanosomatidic drug discovery value chain