Genetic Diversity and Population Structure of Leishmania infantum in Morocco as Revealed by Multilocus Sequence Typing (MLST) Approach

Leishmania infantum is endemic in Morocco, and it causes both visceral (VL) and cutaneous leishmaniasis (CL). In this study, the multilocus sequence typing (MLST) approach was used to investigate the phylogeny and population structure of Leishmania infantum strains isolated from CL and VL patients and the canine reservoir in different leishmaniasis endemic foci in Morocco. For this purpose, eight loci (pgm, alat, me, fh, g6pd, pgd, gpi and cytb) were amplified in 40 samples, out of which 31 were successfully sequenced. The genetic diversity analysis detected a high degree of intraspecific genetic variability among the studied strains. The phylogenetic and the haplotype analyses showed that most of the strains from the same geographical areas clustered together. The recombination among Leishmania infantum strains was revealed through a splits tree analysis and the number of recombination events. Moreover, the assessment of the gene flow between Leishmania infantum and Leishmania tropica through phylogenetic analysis and haplotype diversity in two endemic foci where the two species were sympatric showed no genetic exchange between the two species.

Enzymatic and Molecular Characterization of Anti-Leishmania Molecules That Differently Target Leishmania and Mammalian eIF4A Proteins, LieIF4A and eIF4AMus

Previous investigations of the Leishmania infantum eIF4A-like protein (LieIF4A) as a potential drug target delivered cholestanol derivatives inhibitors. Here, we investigated the mode of action of cholesterol derivatives as a novel scaffold structure of LieIF4A inhibitors on the RNA-dependent ATPase activity of LieIF4A and its mammalian ortholog (eIF4AI). We compared their biochemical effects on RNA-dependent ATPase activities of both proteins and investigated if rocaglamide, a known inhibitor of eIF4A, could affect LieIF4A as well. Kinetic measurements were conducted at different concentrations of ATP, of the compound and in the presence of saturating whole yeast RNA concentrations. Kinetic analyses showed different ATP binding affinities for the two enzymes as well as different sensitivities to 7-α-aminocholesterol and rocaglamide. The 7-α-aminocholesterol inhibited LieIF4A with a higher binding affinity relative to cholestanol analogs. Cholesterol, another tested sterol, had no effect on the ATPase activity of LieIF4A or eIF4AI. The 7-α-aminocholesterol demonstrated an anti-Leishmania activity on L. infantum promastigotes. Additionally, docking simulations explained the importance of the double bond between C5 and C6 in 7-α-aminocholesterol and the amino group in the C7 position. In conclusion, Leishmania and mammalian eIF4A proteins appeared to interact differently with effectors, thus making LieIF4A a potential drug against leishmaniases.

Multilocus sequence analysis provides new insight into population structure and genetic diversity of Leishmania tropica in Morocco

Cutaneous leishmaniasis (CL) is one of the most neglected tropical diseases, caused by different Leishmania species. Despite its high incidence in Morocco, CL due to Leishmania tropica is poorly understood in terms of its epidemiological status and population structure. In this study, we used multilocus sequence typing (MLST) in order to explore the genetic heterogeneity of L. tropica strains. Samples (N = 48) were collected from CL patients in two localities in Morocco (Foum Jamaa in the Azilal province and Imintanoute in Chichaoua province). PCR-sequencing of 18 strains was carried out for six housekeeping genes (cytb, me, fh, g6pd, pgd and gpi), Genetic diversity indices showed a high population genetic differentiation between and among populations. There was no shared haplotypes between the two localities studied. Our results reveal a considerable degree of differentiation through the relatively high FST value (> 0.4) and remarkable intraspecific polymorphism (S = 29). Imintanoute strains have more polymorphisms (S = 22) than the Foum Jamaa strains despite their small sample size. These results provide crucial background information of epidemiology in Imintanoute which raises questions about animal involvement in L. tropica transmission cycle.

[Ballistic trauma of the face: A new scourge in Tunisia]

INTRODUCTION

Ballistic trauma of the face has aroused growing interest since the proliferation of conflicts in the world and particularly in the fight against terrorism. Their polymorphous and disfiguring character, their particular evolution and prognosis due to the ballistic aetiology, differentiate them from classic maxillofacial trauma. Tunisia did not escape this scourge after the revolution of 2011, and must therefore face the challenge of ballistic trauma in general and of the face in particular.

MATERIALS AND METHODS

We conducted a descriptive retrospective study on 30 patients who were victims of ballistic trauma of the face in the otolaryngology and maxillofacial surgery and ophthalmology departments of the Main Military Hospital of Tunis during the period from January 2011 to April 2018. Our objective was to assess the prevalence of these traumas in Tunisia after the revolution, and to assess their clinical and therapeutic aspects.

RESULTS

Our results showed a clear upward trend in these traumas, mainly caused by the opposition of our armed forces to the terrorist threat. The discussion of our results was therefore descriptive, comparing them to the literature.

CONCLUSION

Currently, it is imperative to develop a strategy for precise and effective management of ballistic trauma of the face due to the increase of armed conflicts, attacks and terrorist acts. Likewise, technological advances to develop soldier protection systems must be implemented.

The In Silico Identification of Potential Members of the Ded1/DDX3 Subfamily of DEAD-Box RNA Helicases from the Protozoan Parasite Leishmania infantum and Their Analyses in Yeast

DEAD-box RNA helicases are ubiquitous proteins found in all kingdoms of life and that are associated with all processes involving RNA. Their central roles in biology make these proteins potential targets for therapeutic or prophylactic drugs. The Ded1/DDX3 subfamily of DEAD-box proteins is of particular interest because of their important role(s) in translation. In this paper, we identified and aligned the protein sequences of 28 different DEAD-box proteins from the kinetoplast-protozoan parasite Leishmania infantum, which is the cause of the visceral form of leishmaniasis that is often lethal if left untreated, and compared them with the consensus sequence derived from DEAD-box proteins in general, and from the Ded1/DDX3 subfamily in particular, from a wide variety of other organisms. We identified three potential homologs of the Ded1/DDX3 subfamily and the equivalent proteins from the related protozoan parasite Trypanosoma brucei, which is the causative agent of sleeping sickness. We subsequently tested these proteins for their ability to complement a yeast strain deleted for the essential DED1 gene. We found that the DEAD-box proteins from Trypanosomatids are highly divergent from other eukaryotes, and consequently they are suitable targets for protein-specific drugs.

A DFT study of Janus structure of S and Se in HfSSe layered as a promising candidate for electronic devices

The transition-metal dichalcogenides are presently being intensively researched because of their unique optoelectronic properties. Further, the success of TMDs in all areas of science without exception has opened the street to find other two-dimensional materials. Based on density functional theory, we study the vibrational and electronic properties of the mixed-phase of S and Se in HfSSe system, i.e, HfSSe monolayer and HfSSe/HfSSe bilayer. In this framework, our systems are full dynamically stable, which shown by their phonon dispersion. Also, we found that the HfSSe (heterolayer) monolayer is an indirect semiconductor (0.63 eV with BLYP), while the HfSSe (alternating) monolayer is a direct semiconductor (0.753 eV with BLYP). Our AA, AB, AA', and AB' of HfSSe/HfSSe (heterolayer) bilayer are indirect band gaps in a range 0.361-0.830 eV, which are promising candidates for electronic devices as field-effect transistors, photodetectors, and other optoelectronics. Nevertheless, HfSSe/HfSSe (alternating) bilayer is a direct bandgap semiconductor with a value of 0.671 eV, when vdW is used.

Infection of Human Neutrophils With Leishmania infantum or Leishmania major Strains Triggers Activation and Differential Cytokines Release

Leishmaniases are neglected diseases, caused by intracellular protozoan parasites of the Leishmania (L.) genus. Although the principal host cells of the parasites are macrophages, neutrophils are the first cells rapidly recruited to the site of parasites inoculation, where they play an important role in the early recognition and elimination of the parasites. The nature of early interactions between neutrophils and Leishmania could influence the outcome of infection. Herein we aimed to evaluate whether different Leishmania strains, responsible for distinct clinical manifestations, could influence ex vivo functional activity of neutrophils. Human polymorphonuclear leukocytes were isolated from 14 healthy volunteers and the ex vivo infection of these cells was done with two L. infantum and one L. major strains. Infection parameters were determined and neutrophils activation was assessed by oxidative burst, degranulation, DNA release and apoptosis; cytokine production was measured by a multiplex flow cytometry analysis. Intracellular amastigotes were rescued to determine Leishmania strains survival. The results showed that L. infantum and L. major promastigotes similarly infected the neutrophils. Oxidative burst, neutrophil elastase, myeloperoxidase activity and apoptosis were significantly increased in infected neutrophils but with no differences between strains. The L. infantum-infected neutrophils induced more DNA release than those infected by L. major. Furthermore, Leishmania strains induced high amounts of IL-8 and stimulated the production of IL-1β, TNF-α, and TGF-β by human neutrophils. We observed that only one strain promoted IL-6 release by these neutrophils. The production of TNF-α was also differently induced by the parasites strains. All these results demonstrate that L. infantum and L. major strains were able to induce globally a similar ex vivo activation and apoptosis of neutrophils; however, they differentially triggered cytokines release from these cells. In addition, rescue of intracellular parasites indicated different survival rates further emphasizing on the influence of parasite strains within a species on the fate of infection.

Leishmania infantum LeIF and its recombinant polypeptides induce the maturation of dendritic cells in vitro: An insight for dendritic cells based vaccine

We previously showed that recombinant Leishmania infantum eukaryotic initiation factor (LieIF) was able to induce the secretion of cytokines IL-12, IL-10 and TNF-α by human monocytes. In this study, we explored in vitro the potential of LieIF to induce phenotypic maturation and functional differentiation of murine bone-marrow derived dendritic cells (BM-DCs). Moreover, in order to identify potential immunnomodulatory regions of LieIF, eight recombinant overlapping protein fragments covering the whole amino acid sequence of protein, were constructed and assessed in vitro for their ability to induce maturation of BM-DCs. Our data showed that LieIF and some of its recombinant polypeptides were able to induce elevated expression of CD40, CD80 and CD86 co-stimulatory molecules with concurrent IL-12 production. Moreover, we used an in vivo experimental model of cutaneous leishmaniasis consisted of susceptible Leishmania major-infected BALB/c mice and we demonstrated that LieIF-pulsed-BM-DCs adoptively transferred in mice were capable to confer protection against a high dose parasite challenge. This study further describes the immunomodulatory properties of LieIF and its polypeptides bringing relevant information for their exploitation as candidate molecules for vaccine development against leishmaniasis.

The steroid derivative 6-aminocholestanol inhibits the DEAD-box helicase eIF4A (LieIF4A) from the Trypanosomatid parasite Leishmania by perturbing the RNA and ATP binding sites

The antifungal agent 6-aminocholestanol targets the production of ergosterol, which is the principle sterol in many fungi and protozoans; ergosterol serves many of the same roles as cholesterol in animals. We found that it also is an effective inhibitor of the translation-initiation factor eIF4AI from mouse (eIF4AI_Mus) and the Trypanosomatid parasite Leishmania (LieIF4A). The eIF4A proteins belong to the DEAD-box family of RNA helicases, which are ATP-dependent RNA-binding proteins and RNA-dependent ATPases. DEAD-box proteins contain a commonly-shared core structure consisting of two linked domains with structural homology to that of recombinant protein A (RecA) and that contain conserved motifs that are involved in RNA and ATP binding, and in the enzymatic activity. The compound inhibits both the ATPase and helicase activities by perturbing ATP and RNA binding, and it is capable of binding other proteins containing nucleic acid-binding sites as well. We undertook kinetic analyses and found that the Leishmania LieIF4A protein binds 6-aminocholestanol with a higher apparent affinity than for ATP, although multiple binding sites were probably involved. Competition experiments with the individual RecA-like domains indicate that the primary binding sites are on RecA-like domain 1, and they include a cavity that we previously identified by molecular modeling of LieIF4A that involve conserved RNA-binding motifs. The compound affects the mammalian and Leishmania proteins differently, which indicates the binding sites and affinities are not the same. Thus, it is possible to develop drugs that target DEAD-box proteins from different organisms even when they are implicated in the same biological process.

Identification of novel leishmanicidal molecules by virtual and biochemical screenings targeting Leishmania eukaryotic translation initiation factor 4A

Leishmaniases are neglected parasitic diseases in spite of the major burden they inflict on public health. The identification of novel drugs and targets constitutes a research priority. For that purpose we used Leishmania infantum initiation factor 4A (LieIF), an essential translation initiation factor that belongs to the DEAD-box proteins family, as a potential drug target. We modeled its structure and identified two potential binding sites. A virtual screening of a diverse chemical library was performed for both sites. The results were analyzed with an in-house version of the Self-Organizing Maps algorithm combined with multiple filters, which led to the selection of 305 molecules. Effects of these molecules on the ATPase activity of LieIF permitted the identification of a promising hit (208) having a half maximal inhibitory concentration (IC50) of 150 ± 15 μM for 1 μM of protein. Ten chemical analogues of compound 208 were identified and two additional inhibitors were selected (20 and 48). These compounds inhibited the mammalian eIF4I with IC50 values within the same range. All three hits affected the viability of the extra-cellular form of L. infantum parasites with IC50 values at low micromolar concentrations. These molecules showed non-significant toxicity toward THP-1 macrophages. Furthermore, their anti-leishmanial activity was validated with experimental assays on L. infantum intramacrophage amastigotes showing IC50 values lower than 4.2 μM. Selected compounds exhibited selectivity indexes between 19 to 38, which reflects their potential as promising anti-Leishmania molecules.

Leishmania infantum 5'-Methylthioadenosine Phosphorylase presents relevant structural divergence to constitute a potential drug target

BACKGROUND

The 5'-methylthioadenosine phosphorylase (MTAP), an enzyme involved in purine and polyamine metabolism and in the methionine salvage pathway, is considered as a potential drug target against cancer and trypanosomiasis. In fact, Trypanosoma and Leishmania parasites lack de novo purine pathways and rely on purine salvage pathways to meet their requirements. Herein, we propose the first comprehensive bioinformatic and structural characterization of the putative Leishmania infantum MTAP (LiMTAP), using a comparative computational approach.

RESULTS

Sequence analysis showed that LiMTAP shared higher identity rates with the Trypanosoma brucei (TbMTAP) and the human (huMTAP) homologs as compared to the human purine nucleoside phosphorylase (huPNP). Motifs search using MEME identified more common patterns and higher relatedness of the parasite proteins to the huMTAP than to the huPNP. The 3D structures of LiMTAP and TbMTAP were predicted by homology modeling and compared to the crystal structure of the huMTAP. These models presented conserved secondary structures compared to the huMTAP, with a similar topology corresponding to the Rossmann fold. This confirmed that both LiMTAP and TbMTAP are members of the NP-I family. In comparison to the huMTAP, the 3D model of LiMTAP showed an additional α-helix, at the C terminal extremity. One peptide located in this specific region was used to generate a specific antibody to LiMTAP. In comparison with the active site (AS) of huMTAP, the parasite ASs presented significant differences in the shape and the electrostatic potentials (EPs). Molecular docking of 5'-methylthioadenosine (MTA) and 5'-hydroxyethylthio-adenosine (HETA) on the ASs on the three proteins predicted differential binding modes and interactions when comparing the parasite proteins to the human orthologue.

CONCLUSIONS

This study highlighted significant structural peculiarities, corresponding to functionally relevant sequence divergence in LiMTAP, making of it a potential drug target against Leishmania.

Leishmania eukaryotic initiation factor (LeIF) inhibits parasite growth in murine macrophages

The leishmaniases constitute neglected global public health problems that require adequate control measures, prophylactic clinical vaccines and effective and non-toxic drug treatments. In this study, we explored the potential of Leishmania infantum eukaryotic initiation factor (LieIF), an exosomal protein, as a novel anti-infective therapeutic molecule. More specifically, we assessed the efficacy of recombinant LieIF, in combination with recombinant IFN-γ, in eliminating intracellular L. donovani parasites in an in vitro macrophage model. J774A.1 macrophages were initially treated with LieIF/IFN-γ prior to in vitro infection with L. donovani stationary phase promastigotes (pre-infection treatment), and resistance to infection was observed 72 h after infection. J774A.1 macrophages were also treated with LieIF/IFN-γ after L. donovani infection (post-infection treatment), and resistance to infection was also observed at both time points tested (19 h and 72 h) after infection. To elucidate the LieIF/IFN-γ-induced mechanism(s) that mediate the reduction of intracellular parasite growth, we examined the generation of potent microbicidal molecules, such as nitric oxide (NO) and reactive oxygen species (ROS), within infected macrophages. Furthermore, macrophages pre-treated with LieIF/IFN-γ showed a clear up-regulation in macrophage inflammatory protein 1α (MIP-1α) as well as tumor necrosis factor alpha (TNF-α) expression. However, significant different protein levels were not detected. In addition, macrophages pre-treated with LieIF/IFN-γ combined with anti-TNF-α monoclonal antibody produced significantly lower amounts of ROS. These data suggest that during the pre-treatment state, LieIF induces intramacrophage parasite growth inhibition through the production of TNF-α, which induces microbicidal activity by stimulating NO and ROS production. The mechanisms of NO and ROS production when macrophages are treated with LieIF after infection are probably different. Overall, these results indicate that LieIF is a good candidate for use as an anti-leishmanial molecule.

The Mating Competence of Geographically Diverse Leishmania major Strains in Their Natural and Unnatural Sand Fly Vectors

Invertebrate stages of Leishmania are capable of genetic exchange during their extracellular growth and development in the sand fly vector. Here we explore two variables: the ability of diverse L. major strains from across its natural range to undergo mating in pairwise tests; and the timing of the appearance of hybrids and their developmental stage associations within both natural (Phlebotomus duboscqi) and unnatural (Lutzomyia longipalpis) sand fly vectors. Following co-infection of flies with parental lines bearing independent drug markers, doubly-drug resistant hybrid progeny were selected, from which 96 clonal lines were analyzed for DNA content and genotyped for parent alleles at 4–6 unlinked nuclear loci as well as the maxicircle DNA. As seen previously, the majority of hybrids showed ‘2n’ DNA contents, but with a significant number of ‘3n’ and one ‘4n’ offspring. In the natural vector, 97% of the nuclear loci showed both parental alleles; however, 3% (4/150) showed only one parental allele. In the unnatural vector, the frequency of uniparental inheritance rose to 10% (27/275). We attribute this to loss of heterozygosity after mating, most likely arising from aneuploidy which is both common and temporally variable in Leishmania. As seen previously, only uniparental inheritance of maxicircle kDNA was observed. Hybrids were recovered at similar efficiencies in all pairwise crosses tested, suggesting that L. major lacks detectable ‘mating types’ that limit free genetic exchange. In the natural vector, comparisons of the timing of hybrid formation with the presence of developmental stages suggest nectomonads as the most likely sexually competent stage, with hybrids emerging well before the first appearance of metacyclic promastigotes. These studies provide an important perspective on the prevalence of genetic exchange in natural populations of L. major and a guide for experimental studies to understand the biology of mating.

Leishmania are pathogenic protozoa characterized by substantial diversity in the sand fly species that can transmit them, in the mammalian species that can serve as their reservoir hosts, and in the disease forms and severity of the clinical outcomes they can produce in humans. The possibility that this diversity has arisen, at least in part, by a process involving genetic exchange was recently given experimental support by the recovery of hybrid parasites from sand flies co-infected with two strains of Leishmania major. Here, we demonstrate the sexual competency of L. major strains originating across the full geographic range of this parasite species, and in both natural and unnatural sand fly vectors. Our genotype analyses of a large number of hybrid clones confirmed that they inherited both parental alleles at the majority of chromosomal marker loci analyzed, consistent with a meiotic process, while kinetoplast DNA was inherited from only one parent. Surprisingly, a few nuclear loci were sometimes inherited from only one parent, suggesting loss of heterozygosity. The early timing of hybrid recovery suggests that nectomonad promastigotes are the most likely mating competent stage of the parasite. These studies provide the strongest evidence to date that sex is a component of the natural reproductive strategy of L. major.

Bioinformatic characterizations and prediction of K+ and Na+ ion channels effector toxins

BACKGROUND

K+ and Na+ channel toxins constitute a large set of polypeptides, which interact with their ion channel targets. These polypeptides are classified in two different structural groups. Recently a new structural group called birtoxin-like appeared to contain both types of toxins has been described. We hypothesized that peptides of this group may contain two conserved structural motifs in K+ and/or Na+ channels scorpion toxins, allowing these birtoxin-like peptides to be active on K+ and/or Na+ channels.

RESULTS

Four multilevel motifs, overrepresented and specific to each group of K+ and/or Na+ ion channel toxins have been identified, using GIBBS and MEME and based on a training dataset of 79 sequences judged as representative of K+ and Na+ toxins.Unexpectedly birtoxin-like peptides appeared to present a new structural motif distinct from those present in K+ and Na+ channels Toxins. This result, supported by previous experimental data, suggests that birtoxin-like peptides may exert their activity on different sites than those targeted by classic K+ or Na+ toxins.Searching, the nr database with these newly identified motifs using MAST, retrieved several sequences (116 with e-value < 1) from various scorpion species (test dataset). The filtering process left 30 new and highly likely ion channel effectors.Phylogenetic analysis was used to classify the newly found sequences. Alternatively, classification tree analysis, using CART algorithm adjusted with the training dataset, using the motifs and their 2D structure as explanatory variables, provided a model for prediction of the activity of the new sequences.

CONCLUSION

The phylogenetic results were in perfect agreement with those obtained by the CART algorithm.Our results may be used as criteria for a new classification of scorpion toxins based on functional motifs.

[A variant of DDRT-PCR using anchored mini-exon primers for identification of differentially expressed sequences in Leishmania infantum]

Leishmania infantum (L.i) is responsible for visceral (VL) or cutaneous (CL) leishmaniasis. Previous studies done in Honduras by differential display reverse transcriptase-polymerase chain reaction (DDRT-PCR) failed to demonstrate differences in expression profiles among L. infantum VL and CL parasites. For purpose of comparing expression among L. infantum isolates in Tunisia, a variant of this technique adapted from a commercial kit was developed involving pairs of random and anchored mini-exon primers for isolation and identification of differentially displayed cDNAs. To assess the efficiency of this variant, 34 pairs were applied to 2 consecutive dilutions of cDNAs from promastigotes at end of in vitro exponential growth of 2 visceral (LV50) and cutaneous (DREP14) isolates from Tunisia, thus increasing chance for observing differences among the cDNAs. Profiles were compared and analyzed as regards number and phenotype of bands displayed in 4 types of highly similar amplification profiles among the 2 cDNAs; 26 primer pair combinations generated in total 6.8% differentially displayed bands that had variable intensities or were present/absent, in comparable proportions in the 2 isolates. Analysis further demonstrated differences in amplification efficiency of some primers, emphasizing on qualitative and quantitative impact of relative proximity of the priming sites. Nine present/absent bands were cloned, sequenced and analyzed in silico. Mismatches at priming sites seem to underlie amplification of such bands. Only five products could be referred to annotated gene. Among the genes identified, we list histone H4, largely known to be differentially expressed among L.i stages, and "NTF2-like" for which overexpression in one cDNA was here confirmed. To conclude, the variant developed could be used further in Leishmania expression analysis with appropriate cautions about false positives.

[Differentiation among cutaneous Leishmania species upon amplification of a sequence of dipeptidyl peptidase III encoding gene]

Leishmaniasis are a group of vector-born, parasitic diseases caused by protozoan of the Leishmania genus, that includes visceral or cutaneous forms. Cutaneous leishmaniasis (CL) refers to a group of diseases because of the variability of clinical manifestations, caused by a large number of Leishmania species. In Tunisia, three different forms of CL are encountered, having different causal agents L. infantum, L. major and L. tropica. For the purpose of this study, we assessed the potential of polymorphic sites in dipeptidyl peptidase III (DPP III) encoding gene to differentiate among Leishmania species encountered in Tunisia. A pair of forward and reverse primers amplifying a 664 bp DPP III sequence were designed in regions including 2 mutations in the forward primer and 1 in the reverse, and were used to amplify DNA from diverse species of Leishmania parasites including L. infantum, L. major, L. tropica, L. donovani, L. chagasi, L. arabica, L. aethiopica and L. tarentolae. Amplification was positive for all tested Leishmania species except for L. infantum, L. chagasi, L. archibaldi, L. donovani and L. tarentolae. In case of cutaneous Leishmania species encountered in Tunisia, amplification was positive for both L. tropica and L. major and negative in case of L. infantum. This ability to differentiate L. infantum from L. tropica/L. major constitutes a first step in the taxonomy of cutaneous species prevalent in Tunisia.

Leishmania infantum LeIF protein is an ATP-dependent RNA helicase and an eIF4A-like factor that inhibits translation in yeast

LeIF, a Leishmania protein similar to the eukaryotic initiation factor eIF4A, which is a prototype of the DEAD box protein family, was originally described as a Th1-type natural adjuvant and as an antigen that induces an IL12-mediated Th1 response in the peripheral blood mononuclear cells of leishmaniasis patients. This study aims to characterize this protein by comparative biochemical and genetic analysis with eIF4A in order to assess its potential as a target for drug development. We show that a His-tagged, recombinant, LeIF protein of Leishmania infantum, which was purified from Escherichia coli, is both an RNA-dependent ATPase and an ATP-dependent RNA helicase in vitro, as described previously for other members of the DEAD box helicase protein family. In vivo experiments show that the LeIF gene cannot complement the deletion of the essential TIF1 and TIF2 genes in the yeast Saccharomyces cerevisiae that encode eIF4A. In contrast, expression of LeIF inhibits yeast growth when endogenous eIF4A is expressed off only one of its two encoding genes. Furthermore, in vitro binding assays show that LeIF interacts with yeast eIF4G. These results show an unproductive interaction of LeIF with translation initiation factors in yeast. Furthermore, the 25 amino terminal residues were shown to enhance the ability of LeIF to interfere with the translation machinery in yeast.

Molecular analyses of Old World Leishmania RAPD markers and development of a PCR assay selective for parasites of the L. donovani species Complex

Three amplicons, appearing in a species-specific manner on the electrophoregrams of RAPD reactions that were obtained with primer OPA1, OPA1-800, OPA1- 900, and OPA1-1200, are analyzed in this study. The study revealed that each of these products is composed of one Leishmania DNA band, taxonomically conserved among the different Old World species studied. Subsequently, only the electrophoretic position of the RAPD products can be considered species-specific. In addition, sequence data, genomic organization, and chromosomal location have proved that these fragments are different and physically independent. However, they possess common features related to the presence of different kinds of short DNA repeats, more particularly microsatellites and a CCCTTC motive, corresponding to the 3' half of the OPA1 primer. These results suggest that the OPA1 primer has initiated amplification from different priming sites, having a species-specific location. This corresponds to sequence micro-heterogeneity of DNA fragments present within the different species and leading eventually to a selective amplification of different RAPD products. This characteristic has been used to develop an original selective PCR test based on the sequence of the OPA1-800 product, in which only DNAs from the L. donovani species complex are amplified. Restriction site polymorphisms and sequence variations are identified within the PCR fragment amplified from these parasite DNAs. In fact, the OPA1-800 fragment proved to be a useful DNA marker either as a DNA probe or as a target for PCR-based assays. This tool can therefore be recommended for the control of Old World Leishmania parasites, such as species discrimination, molecular tracking of isolates, or study of polymorphisms within the L. donovani species complex. Moreover, the molecular bases underlying the amplification of the RAPD fragments studied correspond to mechanisms already described. Although they do not account for the amplification of all Leishmania RAPD products, such mechanisms stress some of the pitfalls of the technique, which need to be taken into consideration. We have identified at least misleading observations of DNA bands amplified in a species-specific manner, in spite of their presence in the genome of the other taxa, and relatedness between bands within the amplification profiles. Therefore, recommendations for careful interpretation of RAPD data in population genetics or phylogenetic analyses are reiterated. Molecular analyses are essential to validate conclusions.