A dataset of proteins associated with Trypanosoma cruzi LYT1 mRNAs.

Post-transcriptional gene regulation in Trypanosoma cruzi, the etiological agent of Chagas disease, plays a critical role in ensuring that the parasite successfully completes its life cycle in both of its obligate hosts: insect vector and mammals. This regulation is basically governed by RNA binding proteins (RBPs) through their interactions with cis-elements located in the UTRs of their mRNA targets. LYT1 gene, coding for a virulence factor of T. cruzi, is expressed into two isoforms: kLYT1 and mLYT1, which play different functions according to their cellular location and parasite life-cycle stages. Whereas kLYT1 exhibits a regulatory role during the epimastigote-to-metacyclic trypomastigote stage transition, mLYT1 acts as a pore-forming protein, relevant for host cell invasion and parasite intracellular survival. Considering the LYT1 biological relevance and the fact that this is a protein exclusive of T. cruzi, the protein and its mechanisms regulating the alternative gene expression products are promising targets for therapeutic intervention. In this work, an experimental approach consisting of pull-downs assays followed by proteomic analyzes was carried out to identify the proteins interacting with the different LYT1 mRNAs. The dataset presented here was obtained through three biological replicates using all the different UTRs characterized in the LYT1 mRNAs (i.e., 5´UTR kLYT1, 5´UTR mLYT1, and I and II-type 3´UTRs) as baits, and protein extracts from epimastigotes and trypomastigotes of the 058 PUJ (DTU I) strain. Bound proteins were analyzed by liquid chromatography coupled to mass spectrometry (LC/MS). As a control of non-specificity, the same protein extracts were incubated with Leishmania braziliensis rRNA and the bound proteins also identified by LC/MS. In all, 1,557 proteins were identified, 313 of them were found in at least two replicates and 18 proteins were exclusively associated with the LYT1 baits. Of these, six proteins have motifs related to RNA binding, and seven remain annotated as hypothetical proteins. Remarkably, three of these hypothetical proteins also contain nucleic acid binding motifs. This knowledge, beside expanding the known T. cruzi proteome, gains insight into putative regulatory proteins responsible for alternative LYT1 mRNAs processing. Raw mass spectrometry data are available via MassIVE proteome Xchange with identifier PXD027371.

Variability of the Pr77 sequence of L1Tc retrotransposon among six T. cruzi strains belonging to different discrete typing units (DTUs).

All trypanosomatid genomes are colonized by non-LTR retrotransposons which exhibit a highly conserved 77-nt sequence at their 5' ends, known as the Pr77-hallmark (Pr77). The wide distribution of Pr77 is expected to be related to the gene regulation processes in these organisms as it has promoter and HDV-like ribozyme activities at the DNA and RNA levels, respectively. The identification of Pr77 hallmark-bearing retrotransposons and the study of the associations of mobile elements with relevant genes have been analyzed in the genomes of six strains of Trypanosoma cruzi belonging to different discrete typing units (DTUs) and with different geographical origins and host/vectors. The genomes have been sequenced, assembled and annotated. BUSCO analyses indicated a good quality for the assemblies that were used in comparative analyses. The results show differences among the six genomes in the copy number of genes related to virulence processes, the abundance of retrotransposons bearing the Pr77 sequence and the presence of the Pr77 hallmarks not associated with retroelements. The analyses also show frequent associations of Pr77-bearing retrotransposons and single Pr77 hallmarks with genes coding for trans-sialidases, RHS, MASP or hypothetical proteins, showing variable proportion depending on the type of retroelement, gene class and parasite strain. These differences in the genomic distribution of active retroelements and other Pr77-containing elements have shaped the genome architecture of these six strains and might be contributing to the phenotypic variability existing among them.

Inoculation of the Leishmania infantum HSP70-II Null Mutant Induces Long-Term Protection against L. amazonensis Infection in BALB/c Mice.

Leishmania amazonensis parasites are etiological agents of cutaneous leishmaniasis in the New World. BALB/c mice are highly susceptible to L. amazonensis challenge due to their inability to mount parasite-dependent IFN-γ-mediated responses. Here, we analyzed the capacity of a single administration of the LiΔHSP70-II genetically-modified attenuated L. infantum line in preventing cutaneous leishmaniasis in mice challenged with L. amazonensis virulent parasites. In previous studies, this live attenuated vaccine has demonstrated to induce long-protection against murine leishmaniasis due to Old World Leishmania species. Vaccinated mice showed a reduction in the disease evolution due to L. amazonensis challenge, namely reduction in cutaneous lesions and parasite burdens. In contrast to control animals, after the challenge, protected mice showed anti-Leishmania IgG2a circulating antibodies accompanied to the induction of Leishmania-driven specific IFN-γ systemic response. An analysis performed in the lymph node draining the site of infection revealed an increase of the parasite-specific IFN-ϒ production by CD4+ and CD8+ T cells and a decrease in the secretion of IL-10 against leishmanial antigens. Since the immunity caused by the inoculation of this live vaccine generates protection against different forms of murine leishmaniasis, we postulate LiΔHSP70-II as a candidate for the development of human vaccines.

Leishmania infantum transfected with toxic plasmid induces protection in mice infected with wild type L. infantum or L. amazonensis.

Leishmania infantum infection may cause visceral leishmaniasis (VL), a fatal disease having worldwide distribution, that may be silent or asymptomatic. The latter indicates that immunity is naturally developed in some individuals, and, therefore, a vaccine against VL would be possible. Molecular mechanisms of gene expression are being understood in Leishmania, and this knowledge may be useful for vaccine development. The aim of this study was developing an attenuated strain by regulating the expression of toxic proteins in a stage specific manner. For that purpose, the 3' UTR of an amastin gene, known by its increased expression in the amastigote phase, was selected for direct the expression of exogenous proteins. This construct (pFL-AMA), firstly, was proved effective for the expression of mCherry specifically in the intracellular form of L. infantum, as demonstrated by fluorescence microscopy, flow cytometry and Western blotting. Afterwards, mCherry coding sequence was replaced, in the pFL-AMA plasmid, by either egg avidin or the active form of bovine trypsin. Viability of transfected parasites was evaluated in promastigote axenic cultures and in in vitro infection of macrophages. Both lines of transfected parasites showed a limited capacity to multiply inside macrophages. BALB/c mice were inoculated intraperitoneally (i.p.) with a single dose consisting of 2 × 106L. infantum promastigotes transfected with plasmids bearing the toxic genes. After 10 weeks post-inoculation, no parasites were recovered by limiting dilution in either liver or spleen, but a specific immunological response was detected. The immunization with transfected parasites induced cellular and humoral immune responses with activation of TCD4+, TCD8+ and B cells, having a TH1-type response with increased levels of pro-inflammatory cytokines such as IFN-γ, TNF-α and IL-6. In parallel groups of mice, a challenge consisting on 1 × 106 virulent parasites of either L. infantum (inoculated i.p.) or L. amazonensis subcutaneously (s.c.) was performed. Vaccinated mice, challenged with L. infantum, showed lower parasite burdens in liver, spleen and bone marrow than infected mice with WT L. infantum (non-vaccinated); similarly, vaccinated mice developed smaller footpad inflammation than control group. These data support this strategy as an efficient immunization system aimed to the development of vaccines against different forms of leishmaniasis.

Trypanosoma cruzi Ikiakarora (TcIII) Draft Genome Sequence.

Trypanosoma cruzi shows a genetic diversity that has been associated with the variability of clinical manifestations, geographical distribution, and preferential parasite-vector interactions. In an effort to better understand this genetic variability, here, the draft genome of T. cruzi strain Ikiakarora (discrete typing unit TcIII), which has been associated with the sylvatic cycle, is reported.

Draft Genome Sequence of the Trypanosoma cruzi B. M. López Strain (TcIa), Isolated from a Colombian Patient.

Trypanosoma cruzi parasite strains are classified into six lineages (discrete typing units TcI to TcVI). The broad genetic diversity of T. cruzi strains has an influence on the development of the host response and pathogenesis, as well as drug susceptibility. Here, the draft genome of the T. cruzi B. M. López strain (TcIa) is reported.

Molecular Characterization of Tc964, A Novel Antigenic Protein from Trypanosoma cruzi.

The Tc964 protein was initially identified by its presence in the interactome associated with the LYT1 mRNAs, which code for a virulence factor of Trypanosoma cruzi. Tc964 is annotated in the T. cruzi genome as a hypothetical protein. According to phylogenetic analysis, the protein is conserved in the different genera of the Trypanosomatidae family; however, recognizable orthologues were not identified in other groups of organisms. Therefore, as a first step, an in-depth molecular characterization of the Tc946 protein was carried out. Based on structural predictions and molecular dynamics studies, the Tc964 protein would belong to a particular class of GTPases. Subcellular fractionation analysis indicated that Tc964 is a nucleocytoplasmic protein. Additionally, the protein was expressed as a recombinant protein in order to analyze its antigenicity with sera from Chagas disease (CD) patients. Tc964 was found to be antigenic, and B-cell epitopes were mapped by the use of synthetic peptides. In parallel, the Leishmania major homologue (Lm964) was also expressed as recombinant protein and used for a preliminary evaluation of antigen cross-reactivity in CD patients. Interestingly, Tc964 was recognized by sera from Chronic CD (CCD) patients at different stages of disease severity, but no reactivity against this protein was observed when sera from Colombian patients with cutaneous leishmaniasis were analyzed. Therefore, Tc964 would be adequate for CD diagnosis in areas where both infections (CD and leishmaniasis) coexist, even though additional assays using larger collections of sera are needed in order to confirm its usefulness for differential serodiagnosis.

Subcutaneous Immunization of Leishmania HSP70-II Null Mutant Line Reduces the Severity of the Experimental Visceral Leishmaniasis in BALB/c Mice.

Leishmania infantum parasites cause a severe form of visceral leishmaniasis in human and viscerocutaneous leishmaniasis in dogs. Recently, we reported that immunization with an attenuated L. infantum cell line, lacking the hsp70-II gene, protects against the development of murine cutaneous leishmaniasis. In this work, we analyzed the vaccine potential of this cell line towards the long-term protection against murine visceral leishmaniasis. This model shows an organ-dependent evolution of the disease. The infection can resolve in the liver but chronically affect spleen and bone marrow. Twelve weeks after subcutaneous administration of attenuated L. infantum, Bagg Albino (BALB/c) mice were challenged with infective L. infantum parasites expressing the luciferase-encoding gene. Combining in vivo bioimaging techniques with limiting dilution experiments, we report that, in the initial phase of the disease, vaccinated animals presented lower parasite loads than unvaccinated animals. A reduction of the severity of liver damage was also detected. Protection was associated with the induction of rapid parasite-specific IFN-γ production by CD4+ and CD8+ T cells. However, the vaccine was unable to control the chronic phase of the disease, since we did not find differences in the parasite burdens nor in the immune response at that time point.

Proteins interacting with Leishmania major PUF1: A proteomic dataset.

Leishmania parasites must deal with stressful environmental conditions (thermal, nutritional and oxidative) along their digenetic life cycles. This requires drastic changes in gene expression, which in this parasite occurs mainly through post-transcriptional mechanisms involving RNA binding proteins (RBPs). PUF proteins, a class of RBPs existing in most eukaryotic organisms, might play too an essential role modulating the fate of mRNAs and regulating gene expression in Leishmania parasites. A proteomic approach to identify putative protein partners (interactome) of the Leishmania major PUF1 protein was performed. The PUF1 interactome was characterized by co-immunoprecipitation using L. major cellular extracts and an anti-LiPUF1 antibody, and a subsequent analysis of the co-immunoprecipitated proteins by mass-spectrometry, identifying 90 LmPUF1 candidate partners. Remarkably, many of the identified proteins are other RBPs and/or putative P bodies and mRNA-exporting machinery components. Raw mass spectrometry data are available via ProteomeXchange with identifier PXD022581.

Characterization of the mRNA untranslated regions [UTR] of the Trypanosoma cruzi LYT1 isoforms derived by alternative trans-splicing / Caracterización de las regiones no traducidas ARN [UTR] de las isoformas de Trypanosoma cruzi LYT1 derivadas de un trans-empalme alternativo / Caracterização das regiões não-traduzidas do RNA [UTR] das isoformas de Trypanosoma cruzi LYT1 derivadas de uma junção trans-alternativa

Abstract In trypanosomatids, gene expression is mainly regulated at posttranscriptional level, through mechanisms based on the interaction between RNA Binding Proteins [RBPs] and motifs present in the untranslated regions [UTRs] of the mRNAs, which altogether form ribonucleoproteic complexes [RNP] that define the fate of the mRNA. The pre-mRNA derived from the LYT1 gene of Trypanosoma cruzi, is processed by alternative trans-splicing, resulting in different mRNAs which code for the isoforms mLYTl and kLYTl, proteins having differential expression, cellular location and function. The aim of this study was to characterize the 5' and 3' UTRs of the LYT1 mRNAs as the initial step towards the objective of identification of the RBPs responsible for their differential expression. The presence of the two types of 5' UTRs were confirmed in two T. cruzi isolates belonging to the DTU I, thus, corroborating the occurrence of alternative trans-splicing also in the LYT1 gene of this T. cruzi DTU. In addition, for the first time, was unscovered the existence of two types of LYT1 mRNAs transcripts, differing in length by 116 nts, that are generated by alternative polyadenylation. Furthermore, an in-silico analysis of the experimentally obtained UTRs, and ten additional LYT1 sequences retrieved from TritrypDB and GenBank databases, together with a thoroughly search of structural motifs, showed a remarkable conservation of relevant structural motifs previously associated with RNA metabolism in the different UTRs; these elements might be involved in the differential stage-specific expression of each LYT1 isoform.

Resumen En los trypanosomátidos, la expresión génica se regula principalmente en el nivel post-transcripcional mediante mecanismos basados en la interacción entre las proteínas de unión del ARN [RBP] y las figuras presentes en las regiones no traducidas [UTR] de las ARN, que en conjunto forman complejos ribonucleoproteicos [RNP] que definen el destino de la ARN. El pre-ARN derivado del gen LYT1 del Trypanosoma cruzi es procesado por trans-empalme alternativo, dando como resultado diferentes ARN que codifican las isoformas mLYTl y kLYTl, proteínas con expresión diferencial, localización celular y función. El objetivo de este estudio fue caracterizar los 5' y 3' UTR de las ARN LYT1 como el paso inicial hacia la identificación de los RPB responsables de la expresión diferencial. Se confirmó la presencia de los dos tipos de 5' UTR en dos aislantes del T. cruzi pertenecientes al DTU I; de esta forma también se comprobó la ocurrencia del trans-empalme alternativo en el gen LYT1 de este T. cruzi DTU. Además, por primera vez, se pudo demostrar la existencia de dos tipos de transcripciones de ARN LYT1, que difieren en longitud por 116 nts, y son generadas por poliadenilación alternativa. Adicionalmente, se realizó un análisis in-silico de la UTR obtenida experimentalmente, y otras diez secuencias LYT1 recuperadas de las bases de datos TritrypDB y GenBank, junto con una búsqueda exhaustiva de figuras estructuradas, mostrando una notable conservación de los figuras estructurales asociadas con el metabolismo del ARN en los diferentes UTR; estos elementos podrían estar implicados en la expresión diferenciada de la etapa específica de cada isoforma LYT1.

Resumo Nos tripanossomatídeos, a expressão génica é regulada principalmente a nível pós-transcricional mediante mecanismos baseados na interação entre as proteínas de união do RNA [RBPs] e as fugiras presentes nas regiões não-traduzidas [UTRs] do RNA. O pré-RNA derivado do gene LYT1 do Trypanosoma cruzí é processado por uma junção trans-alternativa, resultando em diferentes RNA que codificam as isoformas mLYTl e kLYTl, proteínas com expressão, localização celular e função diferenciadas. O objetivo de este estudo foi caracterizar as 5' e 3' UTRs dos RNAs LYT1 como sendo o passo inicial na identificação das RBPs responsáveis pela expressão diferenciada. A presença dos dois tipos de 5' UTRs foi confirmada em dois isolados de T. cruzí pertencentes ao DTU I; corroborando assim com a ocorrência da junção trans-alternativa no gene LYT1 de este T. crují DTU. Adicionalmente, se demonstrou pela primeira vez a existência de dois tipos de transcrições de RNA LYT1, que se diferenciam em comprimento por 116 nts, e são geradas por poliadenização alternativa. Além disso, realizou-se uma análise in-sílico da UTR obtida experimentalmente e outras dez sequencias LYT1 recuperadas das bases de dados TritrypDB e GenBank, junto com uma busca exaustiva de figuras estruturadas, mostrando uma notável conservação das figuras estruturais associadas com o metabolismo do RNA nas diferentes UTRs. Estes elementos poderiam estar envolvidos na expressão estágio-específica diferenciada de cada isoforma LYT1.

Vaccine candidates against leishmania under current research.

INTRODUCTION: The search for vaccines to prevent human leishmaniasis is an active field of investigation aimed to prevent the devastating effects of this family of diseases on human health. The design and commercialization of several vaccines against canine leishmaniasis is a hopeful advance toward the achievement of a human vaccine. AREAS COVERED: This review includes a summary of the most relevant immunological aspects accompanying leishmaniasis in natural hosts as well as a description of the latest advances in the multiple strategies that are being followed to develop leishmanial prophylactic vaccines. We have combined citations of the latest specialized reviews with research articles presenting the most recent results. EXPERT COMMENTARY: Achieving safe, effective, durable and low-cost prophylactic vaccines against leishmaniasis is still a major challenge. These vaccines should control not only parasite progression, but also the accompanying pathology, which results from an imbalanced interaction between the infectious agent and the human host immune system. Different strategies for development of vaccines are currently under investigation. They range from the use of live non-pathogenic vectors to the employment of subunit vaccines combined with adjuvants and/or delivery systems inducing cell-mediated immunity.

Vaccination with a Leishmania infantum HSP70-II null mutant confers long-term protective immunity against Leishmania major infection in two mice models.

BACKGROUND: The immunization with genetically attenuated Leishmania cell lines has been associated to the induction of memory and effector T cell responses against Leishmania able to control subsequent challenges. A Leishmania infantum null mutant for the HSP70-II genes has been described, possessing a non-virulent phenotype. METHODOLOGY/PRINCIPAL FINDINGS: The L. infantum attenuated parasites (LiΔHSP70-II) were inoculated in BALB/c (intravenously and subcutaneously) and C57BL/6 (subcutaneously) mice. An asymptomatic infection was generated and parasites diminished progressively to become undetectable in most of the analyzed organs. However, inoculation resulted in the long-term induction of parasite specific IFN-γ responses able to control the disease caused by a challenge of L. major infective promastigotes. BALB/c susceptible mice showed very low lesion development and a drastic decrease in parasite burdens in the lymph nodes draining the site of infection and internal organs. C57BL/6 mice did not show clinical manifestation of disease, correlated to the rapid migration of Leishmania specific IFN-γ producing T cells to the site of infection. CONCLUSION/SIGNIFICANCE: Inoculation of the LiΔHSP70-II attenuated line activates mammalian immune system for inducing moderate pro-inflammatory responses. These responses are able to confer long-term protection in mice against the infection of L. major virulent parasites.

Transcriptionally Driven DNA Replication Program of the Human Parasite Leishmania major.

Faithful inheritance of eukaryotic genomes requires the orchestrated activation of multiple DNA replication origins (ORIs). Although origin firing is mechanistically conserved, how origins are specified and selected for activation varies across different model systems. Here, we provide a complete analysis of the nucleosomal landscape and replication program of the human parasite Leishmania major, building on a better evolutionary understanding of replication organization in Eukarya. We found that active transcription is a driving force for the nucleosomal organization of the L. major genome and that both the spatial and the temporal program of DNA replication can be explained as associated to RNA polymerase kinetics. This simple scenario likely provides flexibility and robustness to deal with the environmental changes that impose alterations in the genetic programs during parasitic life cycle stages. Our findings also suggest that coupling replication initiation to transcription elongation could be an ancient solution used by eukaryotic cells for origin maintenance.

Valores del médico y su carácter: proyecto VADEMECA. Evaluación de los valores del futuro médico / Physician values and character: VADEMECA project. Assesment of the values of the future physician

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Gimatecan and other camptothecin derivatives poison Leishmania DNA-topoisomerase IB leading to a strong leishmanicidal effect.

The aim of this work is the in vitro and ex vivo assessment of the leishmanicidal activity of camptothecin and three analogues used in cancer therapy: topotecan (Hycantim®), gimatecan (ST1481) and the pro-drug irinotecan (Camptosar®) as well as its active metabolite SN-38 against Leishmania infantum. The activity of camptothecin and its derivatives was studied on extracellular L. infantum infrared-emitting promastigotes and on an ex vivo murine model of infected splenocytes with L. infantum fluorescent amastigotes. In situ formation of SDS/KCl precipitable DNA-protein complexes in Leishmania promastigotes indicated that these drugs are DNA topoisomerase IB poisons. The inhibitory potency of camptothecin derivatives on recombinant L. infantum topoisomerase IB was assessed in vitro showing that gimatecan is the most active compound preventing the relaxation of supercoiled DNA at submicromolar concentrations. Cleavage equilibrium assays in Leishmania topoisomerase IB show that gimatecan changes the equilibrium towards cleavage at much lower concentrations than the other camptothecin derivatives and that this effect persists over time. Gimatecan and camptothecin were the most powerful compounds preventing cell growth of free-living L. infantum promastigotes within the same concentration range. All these compounds killed L. infantum splenocyte-infecting amastigotes within the nanomolar range. The amastigote form showed higher sensitivity to topoisomerase IB poisons (with high therapeutic selectivity indexes) than free-living promastigotes. All the compounds assayed poisoned L. infantum DNA topoisomerase IB leading to a strong leishmanicidal effect. Camptothecin derivatives are suitable for reducing the parasitic burden of ex vivo infected splenocytes. The selectivity index of gimatecan makes it a promising drug against this neglected disease.

Appraisal of a Leishmania major strain stably expressing mCherry fluorescent protein for both in vitro and in vivo studies of potential drugs and vaccine against cutaneous leishmaniasis.

BACKGROUND: Leishmania major cutaneous leishmaniasis is an infectious zoonotic disease. It is produced by a digenetic parasite, which resides in the phagolysosomal compartment of different mammalian macrophage populations. There is an urgent need to develop new therapies (drugs) against this neglected disease that hits developing countries. The main goal of this work is to establish an easier and cheaper tool of choice for real-time monitoring of the establishment and progression of this pathology either in BALB/c mice or in vitro assays. To validate this new technique we vaccinated mice with an attenuated Δhsp70-II strain of Leishmania to assess protection against this disease. METHODOLOGY: We engineered a transgenic L. major strain expressing the mCherry red-fluorescent protein for real-time monitoring of the parasitic load. This is achieved via measurement of fluorescence emission, allowing a weekly record of the footpads over eight weeks after the inoculation of BALB/c mice. RESULTS: In vitro results show a linear correlation between the number of parasites and fluorescence emission over a range of four logs. The minimum number of parasites (amastigote isolated from lesion) detected by their fluorescent phenotype was 10,000. The effect of antileishmanial drugs against mCherry+L. major infecting peritoneal macrophages were evaluated by direct assay of fluorescence emission, with IC(50) values of 0.12, 0.56 and 9.20 µM for amphotericin B, miltefosine and paromomycin, respectively. An experimental vaccination trial based on the protection conferred by an attenuated Δhsp70-II mutant of Leishmania was used to validate the suitability of this technique in vivo. CONCLUSIONS: A Leishmania major strain expressing mCherry red-fluorescent protein enables the monitoring of parasitic load via measurement of fluorescence emission. This approach allows a simpler, faster, non-invasive and cost-effective technique to assess the clinical progression of the infection after drug or vaccine therapy.

Indotecan (LMP400) and AM13-55: two novel indenoisoquinolines show potential for treating visceral leishmaniasis.

Visceral leishmaniasis is an emerging neglected tropical disease (NTD) caused by the protozoan Leishmania infantum in the countries bordering the Mediterranean Basin. Currently there is no effective vaccine against this disease, and the therapeutic approach is based on toxic derivatives of Sb(V). Therefore, the discovery of new therapeutic targets and the development of drugs designed to inhibit them comprise an extremely important approach to fighting this disease. DNA topoisomerases (Top) have been identified as promising targets for therapy against leishmaniasis. These enzymes are involved in solving topological problems generated during replication, transcription, and recombination of DNA. Being unlike that of the mammalian host, type IB DNA topoisomerase (TopIB) from Leishmania spp. is a unique bisubunit protein, which makes it very interesting as a selective drug target. In the present investigation, we studied the effect of two TopIB poisons with indenoisoquinoline structure, indotecan and AM13-55, on a murine BALB/c model of infected splenocytes with L. infantum, comparing their effectiveness with that of the clinically tested leishmanicidal drug paromomycin. Both compounds have high selectivity indexes compared with uninfected splenocytes. SDS-KCl-precipitable DNA-protein complexes in Leishmania promastigotes and in vitro cleaving assays confirmed that these drugs are Top poisons. The inhibitory potency of both indenoisoquinolines on L. infantum recombinant TopIB was assessed in vitro, with results showing that indotecan was the most active compound, preventing the relaxation of supercoiled DNA. Experimental infections in susceptible BALB/c mice treated with 2.5 mg/kg body weight/day once every other day for a total of 15 days showed that indotecan cleared more than 80% of the parasite burden of the spleen and liver, indicating promising activity against visceral leishmaniasis.

Secuencia parcial del genoma del maxicírculo de Leishmania braziliensis, comparación con otros tripanosomátidos / Maxicircle genome partial sequence of Leishmania braziliensis: assembling and comparison with other trypanosomatids / Seqüência do genoma parcial do maxicirculo de Leishmania braziliensis: montagem e comparação com outros tripanossomatídeos

Objetivo. Con el fin de aportar nueva información relevante para estudios de genotipificación y filogenética del género Leishmania, en este estudio se determinó y comparó la secuencia del maxicírculo de Leishmania braziliensis, cepa MHOM-BR-75-M2904, con las secuencias del maxicírculo reportadas para otras especies de tripanosomátidos. Materiales y métodos. La búsqueda de las secuencias del maxicírculo se realizó en las bases de datos de secuencias no ensambladas del GeneDB versión 2.1, así como en el GenBank, utilizando los genes ND8 y RPS12 de L. braziliensis como sonda inicial. Estas secuencias se ensamblaron y se compararon con sus homólogas en otros tripanosomátidos mediante el uso de herramientas bioinformáticas como LALIGN y ClustalW2. El tamaño total del maxicírculo se determinó mediante ensayos de Southern blot. Resultados. Se ensamblaron dos fragmentos del maxicírculo de L. braziliensis de 6535 y 4257 nucleótidos, cuyos genes presentaron elevada sintenia y similitud en sus secuencias con los previamente reportados en otras especies de Leishmania. Similitud que se extiende incluso a los patrones de edición de estas moléculas. Conclusiones. A pesar de ser L. braziliensis la especie más divergente del género Leishmania en cuanto a su genoma nuclear, el marxicírculo presenta una elevada conservación. Resultado que sugiere que el patrón de edición presente en las diferentes especies de Leishmania hasta ahora estudiadas se conserva también en el subgénero Viannia, lo que indica una elevada conservación en la edición de los transcritos mitocondriales a nivel de género.

Objective. With the aim to provide new insights for genotyping and phylogenetic studies of the Leishmania genus, in this study the sequence of the maxicircle in Leishmania braziliensis, strain MHOM-BR-75-M2904, was determined and compared with those reported in other trypanosomatids species. Materials and methods. Searches for maxicircle sequences were performed in the unassembled sequences of GeneDB database version 2.1, as well as in the GenBank, using the ND8 and RPS12 genes of L. braziliensis as the initial probes. These sequences were assembled and compared with the homologous sequences of trypanosomatids using the bioinformatics tools LALIGN and ClustalW2. The size of maxicircle was determined by Southern blot assays. Results. Two maxicircle fragments of 6535 and 4257 nucleotides were assembled. The sequences of these genes showed high synteny and similarity with the sequences in other Leishmania species. This similarity even was extended to the editing patterns of these molecules. Conclusions. Although L. braziliensis is the most divergent species of the Leishmania genus in their nuclear genome, the maxicicircle has a high conservation. This result suggests that the pattern of editing present in the different Leishmania species studied has been conserved also in the subgenus Viannia. These results indicate a high conservation in the editing of mitochondrial transcripts at the genus level.

Objetivo. Com o fim de contribuir nova informação relevante para estudos de genotipagem e filogenética do género Leishmania, neste estudo determinou-se a sequência do maxicirculo de Leishmania braziliensis, cepa MHOM-BR-75-M2904, comparandosecom as seqüências do maxicirculo reportadas para outras espécies de tripanossomatídeos. Materiais e Métodos. A busca das seqüências do maxicirculo foi realizada nas bases de dados para seqüências não alinhadas no GeneDB versão 2.1, assim como no GeneBank, utilizando o genes ND8 e RPS12 de L. braziliensis como sonda inicial. Essas seqüências foram alinhadas e comparadas com as suas homologas em outros tripanossomatídeos, mediante o uso de ferramentas bioinformáticas como L-ALIGN e ClustalW2. O tamanho total do maxicirculo foi determinado mediante ensaios de Southern blot. Resultados. Foram alinhados dois fragmentos do maxicirculo de L. braziliensis de 6535 e 4257 nucleotídeos, cujos genes apresentaram elevada sintenia e similaridade nas suas seqüências com os genes previamente reportados nas outras espécies de Leishmania. A similaridade vista estende-se, inclusive, aos padrões de edição para estas moléculas. Conclusões. Apesar de L. braziliensis ser a espécie mais divergente do gênero Leishmania, no que se refere ao seu genoma nuclear, o maxicirculo apresenta uma alta conservação. Esse resultado sugere que o padrão de edição apresentado nas espécies de Leishmania até agora estudadas, é conservado também no subgênero Viannia, o que indica uma alta conservação na edição dos transcritos mitocôndriais ao nível de gênero.

Immunogenicity of HSP-70, KMP-11 and PFR-2 leishmanial antigens in the experimental model of canine visceral leishmaniasis.

Zoonotic visceral leishmaniasis (ZVL) is a parasitic disease caused by Leishmania infantum/L. chagasi that is emerging as an important medical and veterinary problem. Dogs are the domestic reservoir for this parasite and, therefore, the main target for controlling the transmission to humans. In the present work, we have evaluated the immunogenicity of the Leishmania infantum heat shock protein (HSP)-70, paraflagellar rod protein (PFR)-2 and kinetoplastida membrane protein (KMP)-11 recombinant proteins in dogs experimentally infected with the parasite. We have shown that peripheral blood mononuclear cells (PBMC) from experimentally infected dogs proliferated in response to these recombinant antigens and against the soluble leishmanial antigen (SLA). We have also quantified the mRNA expression level of the cytokines induced in PBMC upon stimulation with the HSP-70, PFR-2 and KMP-11 proteins. These recombinant proteins induced an up-regulation of IFN-gamma. HSP-70 and PFR-2 also produced an increase of the TNF-alpha transcripts abundance. No measurable induction of IL-10 was observed and low levels of IL-4 mRNA were produced in response to the three mentioned recombinant antigens. Serum levels of specific antibodies against HSP-70, PFR-2 and KMP-11 recombinant proteins were also determined in these animals. Our study showed that HSP-70, KMP-11 and PFR-2 proteins are recognized by infected canines. Furthermore, these antigens produce a Th1-type immune response, suggesting that they may be involved in protection. The identification as vaccine candidates of Leishmania antigens that elicit appropriate immune responses in the canine model is a key step in the rational approach to generate a vaccine for canine visceral leishmaniasis.

Molecular and functional characterization of adenylate kinase 2 gene from Leishmania donovani.

ATP-regenerating enzymes may have an important role in maintaining ATP levels in mitochondria-like kinetoplast organelle and glycosomes in parasitic protozoa. Adenylate kinase (AK) (ATP:AMP phosphotransferase) catalyses the reversible transfer of the gamma-phosphate group from ATP to AMP, releasing two molecules of ADP. This study describes cloning and functional characterization of the gene encoding AK2 from a genomic library of Leishmania donovani and also its expression in leishmania promastigote cultures. AK2 was localized on an approximately 1.9-Mb chromosomal band as a single copy gene. L. donovani AK2 gene is expressed as a single 1.9-kb mRNA transcript that is developmentally regulated and accumulated during the early log phase. The overexpression of L. donovani AKgene in Escherichia coli yielded a 26-kDa polypeptide that could be refolded to a functional protein with AK activity. The recombinant protein was purified to apparent homogeneity. Kinetic analysis of purified L. donovani AK showed hyperbolic behaviour for both ATP and AMP, with Km values of 104 and 74 microM, respectively. The maximum enzyme activity (Vmax) was 0.18 micromol.min(-1).mg(-1) protein. P1,P5-(bis adenosine)-5'-pentaphosphate (Ap5A), the specific inhibitor of AK, competitively inhibited activity of the recombinant enzymes with estimated Ki values of 190 nM and 160 nM for ATP and AMP, respectively. Ap5A also inhibited the growth of L. donovani promastigotes in vitro which could be only partially reversed by the addition of ADP. Thus, presence of a highly regulated AK2, which may have role in maintenance of ADP/ATP levels in L. donovani, has been demonstrated.