Identification and Mode of Action of a Plant Natural Product Targeting Human Fungal Pathogens.

<i>Candida albicans</i> is a major cause of fungal diseases in humans, and its resistance to available drugs is of concern. In an attempt to identify novel antifungal agents, we initiated a small-scale screening of a library of 199 natural plant compounds (i.e., natural products [NPs]). <i>In vitro</i> susceptibility profiling experiments identified 33 NPs with activity against <i>C. albicans</i> (MIC <sub>50</sub> s ≤ 32 μg/ml). Among the selected NPs, the sterol alkaloid tomatidine was further investigated. Tomatidine originates from the tomato ( <i>Solanum lycopersicum</i> ) and exhibited high levels of fungistatic activity against <i>Candida</i> species (MIC <sub>50</sub> s ≤ 1 μg/ml) but no cytotoxicity against mammalian cells. Genome-wide transcriptional analysis of tomatidine-treated <i>C. albicans</i> cells revealed a major alteration (upregulation) in the expression of ergosterol genes, suggesting that the ergosterol pathway is targeted by this NP. Consistent with this transcriptional response, analysis of the sterol content of tomatidine-treated cells showed not only inhibition of Erg6 (C-24 sterol methyltransferase) activity but also of Erg4 (C-24 sterol reductase) activity. A forward genetic approach in <i>Saccharomyces cerevisiae</i> coupled with whole-genome sequencing identified 2 nonsynonymous mutations in <i>ERG6</i> (amino acids D249G and G132D) responsible for tomatidine resistance. Our results therefore unambiguously identified Erg6, a C-24 sterol methyltransferase absent in mammals, to be the main direct target of tomatidine. We tested the <i>in vivo</i> efficacy of tomatidine in a mouse model of <i>C. albicans</i> systemic infection. Treatment with a nanocrystal pharmacological formulation successfully decreased the fungal burden in infected kidneys compared to the fungal burden achieved by the use of placebo and thus confirmed the potential of tomatidine as a therapeutic agent

The Global Health System: Actors, Norms, and Expectations in Transition

In the first in a series of four articles highlighting the changing nature of global health institutions, Nicole Szlezák and colleagues outline the origin and aim of the series

Caracterização dos macrófagos presentes nas lesões cutâneas da hanseníase: estudo por monoclonais

As lesões cutâneas de 16 pacientes com hanseníase foram estudadas por imunofluorescência com anticorpos monoclonais anti-monócitos (OKM1 e anti-MO) e anti-Ia (OKIa). Foi avaliada a atividade de fosfatase ácida utilizando-se naftol AS-B1 fosfato como substrato. Os macrófagos parecem constituir uma população heterogênea em relação aos antigenos estudados neste trabalho e quanto a atividade enzimática. Em todas as formas estudadas um grande número de células eram OKIa positivas

Pathogen-Specific Epitopes as Epidemiological Tools for Defining the Magnitude of Mycobacterium leprae Transmission in Areas Endemic for Leprosy

During recent years, comparative genomic analysis has allowed the identification of Mycobacterium leprae-specific genes with potential application for the diagnosis of leprosy. In a previous study, 58 synthetic peptides derived from these sequences were tested for their ability to induce production of IFN-γ in PBMC from endemic controls (EC) with unknown exposure to M. leprae, household contacts of leprosy patients and patients, indicating the potential of these synthetic peptides for the diagnosis of sub- or preclinical forms of leprosy. In the present study, the patterns of IFN-γ release of the individuals exposed or non-exposed to M. leprae were compared using an Artificial Neural Network algorithm, and the most promising M. leprae peptides for the identification of exposed people were selected. This subset of M. leprae-specific peptides allowed the differentiation of groups of individuals from sites hyperendemic for leprosy versus those from areas with lower level detection rates. A progressive reduction in the IFN-γ levels in response to the peptides was seen when contacts of multibacillary (MB) patients were compared to other less exposed groups, suggesting a down modulation of IFN-γ production with an increase in bacillary load or exposure to M. leprae. The data generated indicate that an IFN-γ assay based on these peptides applied individually or as a pool can be used as a new tool for predicting the magnitude of M. leprae transmission in a given population