Low Plasma Lipids Are Associated with Relapsing and Lethal Visceral Leishmaniasis in HIV-Infected Patients.

Visceral leishmaniasis (VL) results from protozoa Leishmania infantum and L. donovani infection. This study investigated whether host factors would explain the relapses. First, susceptibility to amphotericin B of L. infantum isolates was evaluated in vitro. Then, clinical data and the lipid profile of patients with relapsing and non-relapsing VL were assessed. Susceptibility to amphotericin B was similar between the isolates. CD4+ lymphocytes were reduced in both groups of patients in the first episode and with relapsing VL. Still, the strongest blood cell indicator associated with relapses was low total lymphocyte counts. Total plasma cholesterol, high-density lipoprotein, low-density lipoprotein, and, uniquely, triglycerides of the six individuals in the first episode and twenty-three with relapsing VL were lower in relapsing patients than those in the first episode. Deceased patients had extremely low low-density lipoprotein. After CD4+ decreases, lymphocyte CD8+ reduction is the final stage of immunological failure. The lower lipid concentrations appear to be secondary to the depletion of fat stores by inflammation-induced cachexia and fat exhaustion provoked by the co-occurrence of both diseases, which can finally lead to death.

Cellular infiltrate in cutaneous leishmaniasis lesions and therapeutic outcome

Abstract Background: The treatment of cutaneous leishmaniasis is a challenge. A better understanding of the in situ mechanisms involved in the evolution and cure of the disease is essential for the development of new therapies. Objective: Correlate histopathological and immunological characteristics of cutaneous leishmaniasis lesions with clinical outcome after different treatment regimens. Methods: The authors analyzed cellular infiltration and immunohistochemistry staining for CD4, CD8 and IL-17 in biopsy samples from 33 patients with cutaneous leishmaniasis before treatment. All patients were recruited in a randomized clinical trial at Corte de Pedra (Bahia-Brazil) and assigned to receive Glucantime®, Glucantime® + Oral Tamoxifen or Glucantime® + Topical Tamoxifen. Patients were followed for 2 to 6 months to define disease outcome. Results: A similar expression of CD4, CD8 and IL-17 was observed in lesion samples regardless of clinical outcome. In general, a higher amount of CD8 cells were observed compared with CD4 cells. An important observation was that all patients whose cellular infiltrate did not contain plasma cells were cured after treatment. Study limitations: Isolated quantification of TCD8 and IL-17 using immunohistochemistry is insufficient to analyze the role of these molecules in the immunopathogenesis of cutaneous leishmaniasis. In addition, the expansion of the immunohistochemistry panel would allow a more complete analysis of the immune response in situ. Conclusions: The absence of plasma cells in cutaneous leishmaniasis lesions was related to a favorable therapeutic outcome.

Cellular infiltrate in cutaneous leishmaniasis lesions and therapeutic outcome.

BACKGROUND: The treatment of cutaneous leishmaniasis is a challenge. A better understanding of the in situ mechanisms involved in the evolution and cure of the disease is essential for the development of new therapies. OBJECTIVE: Correlate histopathological and immunological characteristics of cutaneous leishmaniasis lesions with clinical outcome after different treatment regimens. METHODS: The authors analyzed cellular infiltration and immunohistochemistry staining for CD4, CD8 and IL-17 in biopsy samples from 33 patients with cutaneous leishmaniasis before treatment. All patients were recruited in a randomized clinical trial at Corte de Pedra (Bahia-Brazil) and assigned to receive Glucantime®, Glucantime® + Oral Tamoxifen or Glucantime® + Topical Tamoxifen. Patients were followed for 2 to 6 months to define disease outcome. RESULTS: A similar expression of CD4, CD8 and IL-17 was observed in lesion samples regardless of clinical outcome. In general, a higher amount of CD8 cells were observed compared with CD4 cells. An important observation was that all patients whose cellular infiltrate did not contain plasma cells were cured after treatment. STUDY LIMITATIONS: Isolated quantification of TCD8 and IL-17 using immunohistochemistry is insufficient to analyze the role of these molecules in the immunopathogenesis of cutaneous leishmaniasis. In addition, the expansion of the immunohistochemistry panel would allow a more complete analysis of the immune response in situ. CONCLUSIONS: The absence of plasma cells in cutaneous leishmaniasis lesions was related to a favorable therapeutic outcome.

Tamoxifen inhibits the biosynthesis of inositolphosphorylceramide in Leishmania.

Previous work from our group showed that tamoxifen, an oral drug that has been in use for the treatment of breast cancer for over 40 years, is active both in vitro and in vivo against several species of Leishmania, the etiological agent of leishmaniasis. Using a combination of metabolic labeling with [3H]-sphingosine and myo-[3H]-inositol, alkaline hydrolysis, HPTLC fractionations and mass spectrometry analyses, we observed a perturbation in the metabolism of inositolphosphorylceramides (IPCs) and phosphatidylinositols (PIs) after treatment of L. amazonensis promastigotes with tamoxifen, with a significant reduction in the biosynthesis of the major IPCs (composed of d16:1/18:0-IPC, t16:0/C18:0-IPC, d18:1/18:0-IPC and t16:0/20:0-IPC) and PIs (sn-1-O-(C18:0)alkyl -2-O-(C18:1)acylglycerol-3-HPO4-inositol and sn-1-O-(C18:0)acyl-2-O-(C18:1)acylglycerol-3-HPO4-inositol) species. Substrate saturation kinetics of myo-inositol uptake analyses indicated that inhibition of inositol transport or availability were not the main reasons for the reduced biosynthesis of IPC and PI observed in tamoxifen treated parasites. An in vitro enzymatic assay was used to show that tamoxifen was able to inhibit the Leishmania IPC synthase with an IC50 value of 8.48 µM (95% CI 7.68-9.37), suggesting that this enzyme is most likely one of the targets for this compound in the parasites.

Tamoxifen and meglumine antimoniate combined therapy in cutaneous leishmaniasis patients: a randomised trial.

OBJECTIVES: There is a clear need for new strategies of leishmaniasis treatment. This work was conducted to evaluate the efficacy of the co-administration of tamoxifen and meglumine antimoniate (SbV ) in a phase II pilot clinical trial in localised cutaneous leishmaniasis patients. METHODS: A randomised controlled pilot clinical trial was conducted to evaluate the efficacy and safety of oral (40 mg/day for 20 days) or topical tamoxifen (0.1% tamoxifen citrate for 20 days) combined with meglumine antimoniate (20 mg SbV /kg/day for 20 days) vs. a standard SbV protocol (20 mg/kg/day for 20 days) for the treatment of cutaneous leishmaniasis. Primary outcome was complete epithelisation of the lesion 6 months after the end of treatment. Secondary outcomes were lesion healing 2 months after the end of treatment and frequency and severity of adverse events. RESULTS: A total of 38 subjects were included in the trial, 15 were treated with standard SbV and 23 with the combination of tamoxifen and SbV . Of the patients treated with the co-administration scheme, 12 received tamoxifen orally and 11 were treated with topical tamoxifen. Tamoxifen administered by the oral or topical routes was well tolerated. Cure rates 6 months after the end of treatment per intention to treat were 40% in the group treated with the standard SbV scheme, and 36.4% and 58%, respectively, for groups treated with SbV plus topical or oral tamoxifen. CONCLUSIONS: In the doses and schemes used in this study, co-administration of oral tamoxifen and SbV resulted in higher cure rates in comparison with the standard scheme of treatment, although not to statistically significant levels.

Chemical Composition, Antiprotozoal and Cytotoxic Activities of Indole Alkaloids and Benzofuran Neolignan of Aristolochia cordigera.

This is a comparative study on the intraspecific chemical variability of Aristolochia cordigera species, collected in two different regions of Brazil, Biome Cerrado (semiarid) and Biome Amazônia (coastal). The use of GC-MS and statistical methods led to the identification of 56 compounds. A higher percentage of palmitone and germacrene-D in the hexanes extracts of the leaves of plants from these respective biomes was observed. Phytochemical studies on the extracts led to the isolation and identification of 19 known compounds, including lignans, neolignans, aristolochic acids, indole-ß-carboline, and indole alkaloids. In addition, two new indole alkaloids, 3,4-dihydro-hyrtiosulawesine and 6-O-(ß-glucopyranosyl)hyrtiosulawesine, were isolated and a new neolignan, cis-eupomatenoid-7, was obtained in a mixture with its known isomer eupomatenoid-7. Their structures were determined by spectroscopic methods, mainly by 1D- and 2D-NMR. The occurrence of indole alkaloids is being described for the first time in the Aristolochiaceae family. Moreover, the in vitro susceptibility of intracellular amastigote and promastigote forms of Leishmania amazonensis to the alkaloids and eupomatenoid-7 were evaluated. This neolignan exhibited low activity against promastigotes (IC50 = 46 µM), while the alkaloids did not show inhibitory activity. The new alkaloid 6-O-(ß-glucopyranosyl)hyrtiosulawesine exhibited activity in the low micromolar range against Plasmodium falciparum, with an IC50 value of 5 µM and a selectivity index higher than 50.

Leishmania is not prone to develop resistance to tamoxifen.

Tamoxifen, an antineoplastic agent, is active in vitro and in vivo against the parasitic protozoa Leishmania. As part of our efforts to unravel this drug's mechanisms of action against the parasite and understand how resistance could arise, we tried to select tamoxifen-resistant Leishmania amazonensis. Three different strategies to generate tamoxifen resistant mutants were used: stepwise increase in drug concentration applied to promastigote cultures, chemical mutagenesis followed by drug selection and treatment of infected mice followed by selection of amastigotes. For amastigote selection, we employed a method with direct plating of parasites recovered from lesions into semi-solid media. Tamoxifen resistant parasites were not rescued by any of these methods. Miltefosine was used as a control in selection experiments and both stepwise selection and chemical mutagenesis allowed successful isolation of miltefosine resistant mutants. These findings are consistent with a multi-target mode of action to explain tamoxifen's leishmanicidal properties. Considering that drug resistance is a major concern in anti-parasitic chemotherapy, these findings support the proposition of using tamoxifen as a partner in drug combination schemes for the treatment of leishmaniasis.

Antileishmanial activity of the estrogen receptor modulator raloxifene.

BACKGROUND: The treatment of leishmaniasis relies mostly on parenteral drugs with potentially serious adverse effects. Additionally, parasite resistance in the treatment of leishmaniasis has been demonstrated for the majority of drugs available, making the search for more effective and less toxic drugs and treatment regimens a priority for the control of leishmaniasis. The aims of this study were to evaluate the antileishmanial activity of raloxifene in vitro and in vivo and to investigate its mechanism of action against Leishmania amazonensis. METHODOLOGY/PRINCIPAL FINDINGS: Raloxifene was shown to possess antileishmanial activity in vitro against several species with EC50 values ranging from 30.2 to 38.0 µM against promastigotes and from 8.8 to 16.2 µM against intracellular amastigotes. Raloxifene's mechanism of action was investigated through transmission electron microscopy and labeling with propidium iodide, DiSBAC2(3), rhodamine 123 and monodansylcadaverine. Microscopic examinations showed that raloxifene treated parasites displayed autophagosomes and mitochondrial damage while the plasma membrane remained continuous. Nonetheless, plasma membrane potential was rapidly altered upon raloxifene treatment with initial hyperpolarization followed by depolarization. Loss of mitochondrial membrane potential was also verified. Treatment of L. amazonensis-infected BALB/c mice with raloxifene led to significant decrease in lesion size and parasite burden. CONCLUSIONS/SIGNIFICANCE: The results of this work extend the investigation of selective estrogen receptor modulators as potential candidates for leishmaniasis treatment. The antileishmanial activity of raloxifene was demonstrated in vitro and in vivo. Raloxifene produces functional disorder on the plasma membrane of L. amazonensis promastigotes and leads to functional and morphological disruption of mitochondria, which culminate in cell death.

Discovery of synthetic Leishmania inhibitors by screening of a 2-arylbenzothiophene library.

Tamoxifen has been shown to be active in vitro against Leishmania and effective in the treatment for leishmaniasis in murine models. Through the screening of a compound library of estrogen receptor modulator analogs, we identified the major characteristics required for antileishmanial activity. To overcome the difficulties presented by tamoxifen's propensity for E/Z isomerization, we used the 2-arylbenzothiophene compound BTP as a more stable alternative. Directed screening of a small compound library based on BTP led to active compounds against Leishmania. Subsequent structure-activity data for the synthetic 2-arylbenzothiophenes evaluated in this study indicate that optimal antileishmanial potency is dependent on the presence of two basic side chains. In addition, the primary structural features required for estrogen receptor binding, the phenols, are not required for inhibiting parasitic growth. Significantly, the most active antileishmanial benzothiophenes lack the pharmacophore for estrogen receptor activity and therefore address potential concerns about the undesirable effects of using selective estrogen receptor modulators in women and children with leishmaniasis. Three compounds selected from the screening have shown consistent activity against all species and stages of Leishmania in vitro although improvements in selectivity are needed. These compounds represent viable starting points for further optimization as antileishmanial agents.

The anticancer drug tamoxifen is active against Trypanosoma cruzi in vitro but ineffective in the treatment of the acute phase of Chagas disease in mice.

The activity of the antineoplastic drug tamoxifen was evaluated against Trypanosoma cruzi. In vitro activity was determined against epimastigote, trypomastigote and amastigote forms of CL14, Y and Y benznidazole resistant T. cruzi strains. Regardless of the strain used, the drug was active against all life-cycle stages of the parasite with a half maximal effective concentration ranging from 0.7-17.9 µM. Two experimental models of acute Chagas disease were used to evaluate the in vivo efficacy of treatment with tamoxifen. No differences in parasitemia and mortality were observed between control mock-treated and tamoxifen-treated mice.

Leishmania-specific surface antigens show sub-genus sequence variation and immune recognition.

BACKGROUND: A family of hydrophilic acylated surface (HASP) proteins, containing extensive and variant amino acid repeats, is expressed at the plasma membrane in infective extracellular (metacyclic) and intracellular (amastigote) stages of Old World Leishmania species. While HASPs are antigenic in the host and can induce protective immune responses, the biological functions of these Leishmania-specific proteins remain unresolved. Previous genome analysis has suggested that parasites of the sub-genus Leishmania (Viannia) have lost HASP genes from their genomes. METHODS/PRINCIPAL FINDINGS: We have used molecular and cellular methods to analyse HASP expression in New World Leishmania mexicana complex species and show that, unlike in L. major, these proteins are expressed predominantly following differentiation into amastigotes within macrophages. Further genome analysis has revealed that the L. (Viannia) species, L. (V.) braziliensis, does express HASP-like proteins of low amino acid similarity but with similar biochemical characteristics, from genes present on a region of chromosome 23 that is syntenic with the HASP/SHERP locus in Old World Leishmania species and the L. (L.) mexicana complex. A related gene is also present in Leptomonas seymouri and this may represent the ancestral copy of these Leishmania-genus specific sequences. The L. braziliensis HASP-like proteins (named the orthologous (o) HASPs) are predominantly expressed on the plasma membrane in amastigotes and are recognised by immune sera taken from 4 out of 6 leishmaniasis patients tested in an endemic region of Brazil. Analysis of the repetitive domains of the oHASPs has shown considerable genetic variation in parasite isolates taken from the same patients, suggesting that antigenic change may play a role in immune recognition of this protein family. CONCLUSIONS/SIGNIFICANCE: These findings confirm that antigenic hydrophilic acylated proteins are expressed from genes in the same chromosomal region in species across the genus Leishmania. These proteins are surface-exposed on amastigotes (although L. (L.) major parasites also express HASPB on the metacyclic plasma membrane). The central repetitive domains of the HASPs are highly variant in their amino acid sequences, both within and between species, consistent with a role in immune recognition in the host.

In vitro sensitivity of Leishmania (Viannia) braziliensis and Leishmania (Leishmania) amazonensis Brazilian isolates to meglumine antimoniate and amphotericin B.

Resistance of Leishmania parasites to specific chemotherapy has become a well-documented problem in the Indian subcontinent in recent years but only a few studies have focused on the susceptibility of American Leishmania isolates. Our susceptibility assays to meglumine antimoniate were performed against intracellular amastigotes after standardizing an in vitro model of macrophage infection appropriate for Leishmania (Viannia) braziliensis isolates. For the determination of promastigote susceptibility to amphotericin B, we developed a simplified MTT-test. The sensitivity in vitro to meglumine antimoniate and amphotericin B of 13 isolates obtained from Brazilian patients was determined. L. (V.) braziliensis isolates were more susceptible to meglumine antimoniate than Leishmania (Leishmania) amazonensis. EC(50), EC(90) and activity indexes (calculated over the sensitivity of reference strains), suggested that all isolates tested were susceptible in vitro to meglumine antimoniate, and did not show association with the clinical outcomes. Isolates were also uniformly susceptible in vitro to amphotericin B.

Inhibitory activity of limonene against Leishmania parasites in vitro and in vivo.

Limonene is a monoterpene that has antitumoral, antibiotic and antiprotozoal activity. In this study we demonstrate the activity of limonene against Leishmania species in vitro and in vivo. Limonene killed Leishmania amazonensis promastigotes and amastigotes with 50% inhibitory concentrations of 252.0+/-49.0 and 147.0+/-46.0 microM, respectively. Limonene was also effective against Leishmania major, Leishmania braziliensis and Leishmania chagasi promastigotes. The treatment of L. amazonensis-infected macrophages with 300 microM limonene resulted in 78% reduction in infection rates. L. amazonensis-infected mice treated topically or intrarectally with limonene had significant reduction of lesion sizes. A significant decrease in the parasite load was shown in the lesions treated topically with limonene by histopathological examination. The intrarectal treatment was highly effective in decreasing the parasite burden, healing established lesions and suppressing the dissemination of ulcers. Limonene presents low toxicity in humans and has been shown to be effective as an agent for enhancing the percutaneous permeation of drugs. Our results suggest that limonene should be tested in different experimental models of infection by Leishmania.

Tamoxifen as a potential antileishmanial agent: efficacy in the treatment of Leishmania braziliensis and Leishmania chagasi infections.

OBJECTIVES: The aim of this study was to evaluate the efficacy of tamoxifen in vivo in experimental models of cutaneous (CL) and visceral leishmaniasis (VL) caused by Leishmania braziliensis and Leishmania chagasi, respectively. METHODS: Drug activity was assessed against intracellular amastigotes by treating infected macrophage cultures and evaluating the number of infected cells. In vivo efficacy of tamoxifen was tested in L. braziliensis-infected BALB/c mice and in L. chagasi-infected hamsters. Treatment with 20 mg/kg/day tamoxifen was administered for 15 days by the intraperitoneal route. Efficacy was evaluated through measurements of lesion size, parasite burden at the lesion site or liver and spleen and survival rate. RESULTS: Tamoxifen killed L. braziliensis and L. chagasi intracellular amastigotes with 50% inhibitory concentrations (IC(50)) of 1.9 +/- 0.2 and 2.4 +/- 0.3 microM, respectively. Treatment of L. braziliensis-infected mice with tamoxifen resulted in significant reductions in lesion size and 99% decrease in parasite burden, compared with mock-treated controls. L. chagasi-infected hamsters treated with tamoxifen showed significant reductions in liver parasite load expressed as Leishman-Donovan units and 95% to 98% reduction in spleen parasite burden. All animals treated with tamoxifen survived while 100% of the mock-treated animals had died by 11 weeks after the interruption of treatment. CONCLUSIONS: Tamoxifen is effective in the treatment of CL and VL in rodent models.

Tamoxifen is effective in the treatment of Leishmania amazonensis infections in mice.

BACKGROUND: Chemotherapy is still a critical issue in the management of leishmaniasis. Until recently, pentavalent antimonials, amphotericin B or pentamidine compounded the classical arsenal of treatment. All these drugs are toxic and have to be administered by the parenteral route. Tamoxifen has been used as an antiestrogen in the treatment and prevention of breast cancer for many years. Its safety and pharmacological profiles are well established in humans. We have shown that tamoxifen is active as an antileishmanial compound in vitro, and in this paper we analyzed the efficacy of tamoxifen for the treatment of mice infected with Leishmania amazonensis, an etiological agent of localized cutaneous leishmaniasis and the main cause of diffuse cutaneous leishmaniasis in South America. METHODOLOGY/PRINCIPAL FINDINGS: BALB/c mice were infected with L. amazonensis promastigotes. Five weeks post-infection, treatment with 15 daily intraperitoneal injections of 20 mg/kg tamoxifen was administered. Lesion and ulcer sizes were recorded and parasite burden quantified by limiting dilution. A significant decrease in lesion size and ulcer development was noted in mice treated with tamoxifen as compared to control untreated animals. Parasite burden in the inoculation site at the end of treatment was reduced from 10(8.5+/-0.7) in control untreated animals to 10(5.0+/-0.0) in tamoxifen-treated mice. Parasite load was also reduced in the draining lymph nodes. The reduction in parasite number was sustained: 6 weeks after the end of treatment, 10(15.5+/-0.5) parasites were quantified from untreated animals, as opposed to 10(5.1+/-0.1) parasites detected in treated mice. CONCLUSIONS/SIGNIFICANCE: Treatment of BALB/c mice infected with L. amazonensis for 15 days with tamoxifen resulted in significant decrease in lesion size and parasite burden. BALB/c mice infected with L. amazonensis represents a model of extreme susceptibility, and the striking and sustained reduction in the number of parasites in treated animals supports the proposal of further testing of this drug in other models of leishmaniasis.

Tamoxifen is effective against Leishmania and induces a rapid alkalinization of parasitophorous vacuoles harbouring Leishmania (Leishmania) amazonensis amastigotes.

OBJECTIVES: This study was performed to investigate the activity of tamoxifen, an antioestrogen widely used in the treatment of breast cancer, against Leishmania. METHODS: Drug activity was assessed in vitro against axenically grown promastigotes and amastigotes through cell counting or by measuring the cleavage of MTT, and against intracellular amastigotes by treating infected macrophage cultures and evaluating the number of intracellular parasites. Intravacuolar pH changes induced inside parasitophorous vacuoles of Leishmania (Leishmania) amazonensis-infected macrophages were evaluated using the fluorescent probes SNAFL-calcein and Acridine Orange. RESULTS: Tamoxifen killed L. (L.) amazonensis promastigotes and amastigotes with 50% inhibitory concentrations (IC50) of 16.4 +/- 0.2 and 11.1 +/- 0.2 microM, respectively. The drug was also effective against Leishmania (Viannia) braziliensis, Leishmania (Leishmania) major, Leishmania (Leishmania) chagasi and Leishmania (Leishmania) donovani with IC(50) values ranging from 9.0 to 20.2 microM. Tamoxifen induced a rapid and long-lasting alkalinization of the vacuolar environment. We also provide evidence that tamoxifen is more effective against promastigotes and amastigotes at pH 7.5 when compared with cultures at pH 4.5. CONCLUSIONS: Tamoxifen effectively kills several Leishmania species and its activity against the parasite is increased by a modulation of the host cell intravacuolar pH induced by the drug.

Characterisation of a new Leishmania META gene and genomic analysis of the META cluster.

The META1 gene of Leishmania is upregulated in metacyclic promastigotes and encodes a 12 kDa virulence-related protein, conserved in all Leishmania species analysed. In this study, the genomic region adjacent to the Leishmania amazonensis META1 gene was characterised and compared to the Leishmania major META1 locus as well as to syntenic loci identified in Trypanosoma brucei and Trypanosoma cruzi. Three new genes expressed with increased abundance of steady state mRNA in L. amazonensis promastigotes were identified, two of which are upregulated in stationary phase promastigotes, sharing the pattern of expression previously described for the META1 mRNA. One of these new genes, named META2, encodes a polypeptide of 444 amino acid residues with a repetitive structure showing three repeats of the META domain (defined as a small domain family found in the Leishmania META1 protein and in bacterial proteins hypothetically secreted and/or implicated in motility) and a carboxyl-terminal region similar to several putative calpain-like proteins of Trypanosoma and Leishmania.

Specificity of a ribosomal DNA derived oligonucleotide probe in the diagnosis of cutaneous or mucocutaneous leishmaniasis

Detection of parasites in clinical lesions is essential for a conclusive diagnosis of cutaneous or mucocutaneous leishmaniasis. Biopsies of experimentally infected animals were used to test a ribosomal DNA (rDNA) derived oligonucleotide (S3) as a diagnostic tool for leishmaniasis, Leishmania amazonensis were detected by that probe in dot blot assays containing RNA from experimentally induced BALB/c footpad lesions. RNA from a macrophage rich lesion induced by BCG infection yielded negative results. Specificity of S3 in differential diagnosis was also experimentally evidenced by the negative hybridization with nucleic acids of other infectious agents causing cutaneous lesions such Fonsecaea pedrosoi, Cladosporium carrionii, Phialophora verrucosa, Sporotrix schenkii, Histoplasma capsulatum and Paracoccidioides brasiliensis. In addition, comparison of S3 and 18S rDNA sequences of Mycobacterium tuberculosis, atypical mycobacteria, M. leprae and Treponema pallidum revealed a low degree of similarity. These data indicated that S3 can identify Leishmania species ande exclude the presence of other pathogens, which lead to misdiagnosis, in hybridization tests.

Molecular biology applied to parasitology: the ribosomal cistron as a tool in taxonomic and phylogenetic studies and as model for gene expression analysis

The singular sequence organization of ribosomal RNA encoding genes, consisting in the presence of highly conserved segments immersed in neutral evolving sequences, allowed its utilization as a tool for taxonomic and phylogenetic studies. In this communication a review of some contributions to related studies on Trypanosomatidae family organisms is presented. The desription of restriction maps for these genes led to the consequent description of probes useful for proper identification of the parasites. Better conditions for detection of parasites in samples from patients or from insect host vectors in endemic areas were established. On the other side, studies on basic concerns such as the regulation of gene expression, led to the determination of the promoter region for RNA Pol I of Trypanosoma cruzi. Sequence comparison with other trypanosomatid promoters did not show any consensus. However, the presence of elements in both promoter region and sequences upstream to the promoter indicated a possible transcription regulatory role for these elements. Transfection experiments showed that no enhancer activity is present.