Drugs against leishmaniasis: a synergy of technology and partnerships

A novel approach to design chimeric multi epitope vaccine against Leishmania exploiting infected host cell proteome

Leishmaniasis is a major infectious disease having high mortality which could be attributed to lack of a suitable vaccine candidate. We propose a novel approach to design multiepitope vaccine to leishmaniasis exploiting specific membrane proteome from infected macrophage from host. The MHC-I, MHC-II and BC epitopes predicted for unique proteins from the infected macrophages and Leishmania and a MEV designed in various combinations (1a-1m). The epitope arrangements 1a, 1k, 1l, and 1 m showed a strong antigenicity profile and immune response. The molecular dynamics simulation indicate the 1k, 1l, and 1 m constructs have strong affinity toward TLR-2, TLR-3, and TLR-4. Overall the structural and immunogenicity profile suggests 1k is top candidate. Further, a computational model system with TLR-2, TLR-3, TLR-4, BCR, MHC-I and MHC-II was generated for 1k construct to understand the MEV interactions with immune components. Dihedral distribution and distance was enumerated to understand the movement of immune components towards 1k. The results indicate 1k has strong affinity for the immune response molecules especially TLR-3, BCR and MHC-II are coming in close contact with the MEV through the simulation. The study suggests that designed multi-epitope vaccine 1k has potential to induce proper immune response but warrants further studies.

Microwave Assisted Biology-Oriented Drug Synthesis (BIODS) of NewN, N′-Disubstituted Benzylamine Analogous of 4-Aminoantipyrine against Leishmaniasis -In VitroAssay and In silico-Predicted Molecular Interactions with Key Metabolic Targets

Biology-Oriented Drug Synthesis (BIODS) deals with the simple chemical transformations on the commercially available drugs in order to enhance their new and diversified pharmacological profile. It opens new avenues for the rapid development of drug candidates for neglected tropical diseases (NTDs). Leishmaniasis is one of the NTDs which spread by the bite of sandflies (plebotomine). It ranges from cutaneous self-healing leishmaniasis to life threatening visceral leishmaniasis, known as kala-azar. The current treatment options include the use of pentamidine, miltefosine, and amphotericin B drugs. Unfortunately, all currently available drugs are associated with adverse effects, such as severe nephron- and cardiotoxicity, pancreatitis, and hepatotoxicity. This warrants the development of new drugs against leishmaniasis. Moreover, emergence of resistance against the current medications further worsens the conditions. With this objective, new N, N'-disubstituted benzylamine derivatives of ampyrone (4-aminoantipyrine) were synthesized by using ultrasonication, and microwave assistance. All derivatives were found to be new, except 1, 4, and 11. All the compounds were evaluated for their anti-leishmanial activity, and cellular cytotoxicity. Among them, compounds 4, 5, 8, and 9 showed a significant anti-leishmanial activity in vitro, in comparison to standard drug, miltefosine (IC₅₀ = 25.78 ± 0.2 µM). These compounds were also docked against various metabolic enzymes to predict their interactions and mechanism of action, and were found to act via targeting important enzymes of various metabolic pathways.

In silico Metabolic Pathway Analysis Identifying Target Against Leishmaniasis - A Kinetic Modeling Approach

The protozoan Leishmania donovani, from trypanosomatids family is a deadly human pathogen responsible for causing Visceral Leishmaniasis. Unavailability of proper treatment in the developing countries has served as a major threat to the people. The absence of vaccines has made treatment possibilities to rely solely over chemotherapy. Also, reduced drug efficacy due to emerging resistant strains magnifies the threat. Despite years of formulations for an effective drug therapy, complexity of the disease is also unfortunately increasing. Absence of potential drug targets has worsened the scenario. Therefore exploring new therapeutic approach is a priority for the scientific community to combat the disease. One of the most reliable ways to alter the adversities of the infection is finding new biological targets for designing potential drugs. An era of computational biology allows identifying targets, assisting experimental studies. It includes sorting the parasite’s metabolic pathways that pins out proteins essential for its survival. We have directed our study towards a computational methodology for determining targets against L. donovani from the “purine salvage” pathway. This is a mainstay pathway towards the maintenance of purine amounts in the parasitic pool of nutrients proving to be mandatory for its survival. This study represents an integration of metabolic pathway and Protein-Protein Interactions analysis. It consists of incorporating the available experimental data to the theoretical methods with a prospective to develop a kinetic model of Purine salvage pathway. Simulation data revealed the time course mechanism of the enzymes involved in the synthesis of the metabolites. Modeling of the metabolic pathway helped in marking of crucial enzymes. Additionally, the PPI analysis of the pathway assisted in building a static interaction network for the proteins. Topological analysis of the PPI network through centrality measures (MCC and Closeness) detected targets found common with Dynamic Modeling. Therefore our analysis reveals the enzymes ADSL (Adenylosuccinate lyase) and IMPDH (Inosine-5′-monophosphate dehydrogenase) to be important having a central role in the modeled network based on PPI and kinetic modeling techniques. Further the available three dimensional structure of the enzyme “ADSL” aided towards the search for potential inhibitors against the protein. Hence, the study presented the significance of integrating methods to identify key proteins which might be putative targets against the treatment of Visceral Leishmaniasis and their potential inhibitors.

Synthesis and Antileishmanial Activity of 1,2,4,5-Tetraoxanes against Leishmania donovani

A chemically diverse range of novel tetraoxanes was synthesized and evaluated in vitro against intramacrophage amastigote forms of Leishmania donovani. All 15 tested tetraoxanes displayed activity, with IC₅₀ values ranging from 2 to 45 µm. The most active tetraoxane, compound LC140, exhibited an IC₅₀ value of 2.52 ± 0.65 µm on L. donovani intramacrophage amastigotes, with a selectivity index of 13.5. This compound reduced the liver parasite burden of L. donovani-infected mice by 37% after an intraperitoneal treatment at 10 mg/kg/day for five consecutive days, whereas miltefosine, an antileishmanial drug in use, reduced it by 66%. These results provide a relevant basis for the development of further tetraoxanes as effective, safe, and cheap drugs against leishmaniasis.

Antileishmanial Potential of Propolis Essential Oil and Its Synergistic Combination With Amphotericin B

The antileishmanial activity of Tunisian propolis essential oil (EO) and its combination with amphotericin B was investigated against 2 local clinical strains of Leishmania: Leishmania major and Leishmania infantum. The cytotoxic potential of this EO was evaluated against macrophage Raw264.7. Combination of propolis EO and amphotericin B was investigated using the checkerboard method. The propolis sample was collected from the region of Beni Khalled, a Tunisian city located west of Cape Bon (Nabeul). Its location is particular since it is near to sea with a steppe climate and the predominance of citrus trees. The EO was obtained by Clevenger-type apparatus. Its chemical composition was identified using gas chromatography with flame ionization detector and gas chromatography-mass spectrometry analysis. Our results demonstrate that Tunisian propolis EO exhibit good antileishmanial activity against L. major and L. infantum promastigotes (IC50 = 5.29 ± 0.31 and 3.67 ± 0.52 µg/mL, respectively) and amastigotes (IC50 = 7.38 ± 0.45 and 4.96 ± 0.24 µg/mL, respectively). Moreover, it reduced significantly the parasite proliferation on a dose-dependent response (95%) with low cytotoxicity (selectivity index = 16.18 and 23.33, respectively). Its combination with amphotericin B showed a synergistic potential (fractional inhibitory concentration = 0.37). Interestingly, the data suggest that propolis EO was involved in macrophage activation by hyperproduction of NO. A total of 51 compounds were identified in the propolis EO. The major compound identified was α-pinene (36.7% ± 2.36%) followed by α-cedrol (6.7% ± 0.10%), totarol (6.6% ± 0.09%), and dehydroabietane (5.2% ± 0.10%). Our findings suggest that Tunisian propolis might constitute a promising source for antileishmanial molecules.

Antileishmanial activity of Melampodium divaricatum and Casearia sylvestris essential oils on Leishmania amazonensis

Leishmaniasis is a disease that affects millions of people and it is an important public health problem. The drugs currently used for the treatment of leishmaniasis present undesirable side effects and low efficacy. In this study, we evaluated the in vitro activity of Melampodium divaricatum (MD-EO) and Casearia sylvestris (CS-EO) essential oils (EO) against promastigote and amastigote forms of Leishmania amazonensis. Sesquiterpenes E-caryophyllene (56.0%), germacrene D (12.7%) and bicyclogermacrene (9.2%) were identified as the main components of MD-EO, whereas E-caryophyllene (22.2%), germacrene D (19.6%) and bicyclogermacrene (12.2%) were the main constituents of CS-EO. CS-EO and E-caryophyllene were active against promastigote forms of L. amazonensis (IC50 24.2, 29.8 and 49.9 µg/mL, respectively). However, MD-EO, CS-EO and E-caryophyllene were more active against amastigote forms, with IC50 values of 10.7, 14.0, and 10.7 µg/mL, respectively. E-caryophyllene presented lower cytotoxicity against macrophages J774-A1 (CC50 of 62.1 µg/mL) than the EO. The EOs and E-caryophyllene should be further studied for the development of new antileishmanial drugs.

Potential therapeutic targets and the role of technology in developing novel antileishmanial drugs

Leishmaniasis is the most prevalent pathogenic disease in many countries around the world, but there are few drugs available to treat it. Most antileishmanial drugs available are highly toxic, have resistance issues or require hospitalization for their use; therefore, they are not suitable for use in most of the affected countries. Over the past decade, the completion of the genomes of many human pathogens, including that of Leishmania spp., has opened new doors for target identification and validation. Here, we focus on the potential drug targets that can be used for the treatment of leishmaniasis and bring to light how recent technological advances, such as structure-based drug design, structural genomics, and molecular dynamics (MD), can be used to our advantage to develop potent and affordable antileishmanial drugs.

Triazolopyrimidine compounds containing first-row transition metals and their activity against the neglected infectious Chagas disease and leishmaniasis

Leishmaniasis and Chagas disease remain a significant global problem. Current treatments have serious disadvantage due to cost, toxicity, long therapy duration and resistance. In the last years increasing interest has arisen in drug development to fight both diseases. Recently, metal-based drugs have revealed as promising drugs in a variety of therapeutic areas. Herein we describe six newly synthesized transition metal complexes with a bioactive molecule 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine (dmtp). All of them have been characterized by X-ray, spectroscopic and thermal methods. In vitro and in vivo studies (murine model) on the antiproliferative activity of these complexes against Leishmania spp. (Leishmania infantum, Leishmania braziliensis) and Trypanosoma cruzi have been carried out. Our results reveal a strong potential of three of the assayed compounds as antiparasitic agents against the above-mentioned infectious diseases.

Chemical composition, leishmanicidal and cytotoxic activities of the essential oils from Mangifera indica L. var. Rosa and Espada

The essential oils from Mangifera indica var. Rosa and Espada latex were obtained by hydrodistillation and analyzed using GC-FID and GC-MS. Twenty-seven components were identified. The main compound in the essential oil from M. indica var. Espada (EOMiE) was terpinolene (73.6%). The essential oil of M. indica var. Rosa (EOMiR) was characterized by high amounts of β-pinene (40.7%) and terpinolene (28.3%). In the test for leishmanicidal activity against promastigotes forms of L. amazonensis, EOMiR and EOMiE showed IC₅₀ (72 h) of 39.1 and 23.0 μg/mL, respectively. In macrophages, EOMiR and EOMiE showed CC₅₀ of 142.84 and 158.65 μg/mL, respectively. However, both were more specific to the parasite than macrophages, with values of selectivity index of 6.91 for EOMiE and 3.66 for EOMiR. The essential oils were evaluated for their cytotoxicity against the human tumor cells HEp-2, HT-29, NCI-H292, and HL-60. The EOMiR and EOMiE were most effective against the HL-60, with IC₅₀ values of 12.3 and 3.6 μg/mL, respectively. The results demonstrated that the essential oils of M. indica can destroy L. amazonensis and inhibit tumor cell growth. These findings contribute to the knowledge of the Brazilian biodiversity as a source of potential therapeutic agents.

Immunotherapy and targeted therapies in treatment of visceral leishmaniasis: current status and future prospects

Visceral leishmaniasis (VL) is a vector-borne chronic infectious disease caused by the protozoan parasite Leishmania donovani or Leishmania infantum. VL is a serious public health problem, causing high morbidity and mortality in the developing world with an estimated 0.2-0.4 million new cases each year. In the absence of a vaccine, chemotherapy remains the favored option for disease control, but is limited by a narrow therapeutic index, significant toxicities, and frequently acquired resistance. Improved understanding of VL pathogenesis offers the development and deployment of immune based treatment options either alone or in combination with chemotherapy. Modulations of host immune response include the inhibition of molecular pathways that are crucial for parasite growth and maintenance; and stimulation of host effectors immune responses that restore the impaired effector functions. In this review, we highlight the challenges in treatment of VL with a particular emphasis on immunotherapy and targeted therapies to improve clinical outcomes.

Progress in the treatment of a neglected infectious disease: visceral leishmaniasis

Visceral leishmaniasis (kala-azar) is a disseminated intracellular protozoal infection. Most cases (90%) occur in the rural regions of five countries: India, Sudan, Nepal, Bangladesh and Brazil. As with other infectious diseases embedded in high-level poverty, developing and/or delivering new treatments for visceral leishmaniasis had been painfully slow or nonexistent. However, despite persistent unresolved obstacles (e.g., drug affordability), renewed interest in visceral leishmaniasis and numerous successful treatment trials have combined to turn a therapeutic corner in the past 5 years, yielding new alternatives to conventional pentavalent antimony. Advances include the use of low-cost generic pentavalent antimony, rediscovery of amphotericin B, short-course regimens via lipid formulations of amphotericin B, retesting injectible paromyomycin and, of clear-cut importance, identifying miltefosine (Impavido, Zentaris) as the first effective oral therapy for this neglected disease.

Plants with anti-Leishmania activity: Integrative review from 2000 to 2011

The search for more effective new drugs to treat Leishmaniasis is undoubtedly relevant. Our objective in this study was to investigate research publications addressing plants with anti-Leishmaniasis activity. An integrative review of the literature from 2000 to 2011 was carried out in the databases such as Latin-American and Caribbean Health Sciences (LILACS), Scientific Electronic Library Online (SciELO), and Medical Literature Analysis and Retrieval System Online (MEDLINE). In the initial search, 150 articles were found, with 25 based in LILACS, 68 in SciELO, and 46 in MEDLINE. From these data, after reading the abstracts that were available online, we excluded 12 from LILACS, 39 from SciELO, and 28 from MEDLINE for presenting article duplications. This left 61 articles to be read; however, only 18 of them answered the research questions and determined the final sample of this review. The results showed that research involving the search for new drugs against Leishmaniasis should be intensified, especially for the amastigote form, and studies with in vivo tests could become a great strategy for successfully finding new treatments for Leishmaniasis. It is believed that it is extremely important and urgent to conduct more trials in search of new effective drugs against Leishmaniasis that possess minimal adverse effects and that are easily accessible to the public.

Quantification of Leishmania infantum kinetoplast DNA for monitoring the response to meglumine antimoniate therapy in visceral leishmaniasis

Meglumine antimoniate (Glucantime) remains the therapeutic cornerstone of visceral leishmaniasis (VL). Twenty-one VL patients were treated with Glucantime, extending for 1 week after defervescence. For monitoring the response, Leishmania infantum kinetoplast DNA loads were evaluated using real-time polymerase chain reaction (PCR) assay in the blood. The maximum duration of treatment was 14 days. The loads before treatment ranged from 8 to 1,300,000 parasites/mL (mean = 73,095 parasites/mL), and the mean values on days 3, 7, 14, 28, and 90 were 4,902, 506, 6.33, 0.26, and 0.14, respectively. The loads decline to < 1 parasite/mL for 16 (76%) and 20 (95%) patients on days 14 and 28, respectively, and they decline for all patients by day 90. Results showed a dramatic decrease of the parasite loads, although complete clearance was not accomplished at the end of treatment. Only one relapse (4.5%) was observed. The parasite load can also serve as a dependable index for monitoring the response to Glucantime.

In vitro leishmanicidal activity of imidazole- or pyrazole-based benzo[g]phthalazine derivatives against Leishmania infantum and Leishmania braziliensis species

OBJECTIVES

To evaluate the in vitro leishmanicidal activity of imidazole-based (1-4) and pyrazole-based (5-6) benzo[g]phthalazine derivatives against Leishmania infantum and Leishmania braziliensis.

METHODS

The in vitro activity of compounds 1-6 was assayed on extracellular promastigote and axenic amastigote forms, and on intracellular amastigote forms of the parasites. Infectivity and cytotoxicity tests were performed on J774.2 macrophage cells using meglumine antimoniate (Glucantime) as the reference drug. The mechanisms of action were analysed by iron superoxide dismutase (Fe-SOD) and copper/zinc superoxide dismutase (CuZn-SOD) inhibition, metabolite excretion and transmission electronic microscopy (TEM).

RESULTS

Compounds 1-6 were more active and less toxic than meglumine antimoniate. Data on infection rates and amastigote mean numbers showed that 2, 4 and 6 were more active than 1, 3 and 5 in both L. infantum and L. braziliensis. The inhibitory effect of these compounds on the antioxidant enzyme Fe-SOD of promastigote forms of the parasites was remarkable, whereas inhibition of human CuZn-SOD was negligible. The ultrastructural alterations observed in treated promastigote forms confirmed the greater cell damage caused by the most active compounds 2, 4 and 6. The modifications observed by (1)H-NMR in the nature and amounts of catabolites excreted by the parasites after treatment with 1-6 suggested that the catabolic mechanisms could depend on the structure of the side chains linked to the benzo[g]phthalazine moiety.

CONCLUSIONS

All the compounds assayed were active in vitro against the two Leishmania species and were less toxic against mammalian cells than the reference drug, but the monosubstituted compounds were significantly more effective and less toxic than their disubstituted counterparts.

Evaluation of antileishmanial, cytotoxic and antioxidant activities of essential oils extracted from plants issued from the leishmaniasis-endemic region of Sned (Tunisia)

In this study, we tested 10 essential oils (EOs) extracted from 10 plants issued from Sned region (Tunisia) to evaluate both their leishmanicidal effects against Leishmania major and L. infantum, and their cytotoxicity against murine macrophage cell line RAW 264.7 (ATCC, TIB-71). The antioxidant activity was also monitored by the DDPH method, while the chemical composition of active EO was assessed by GC-MS analysis. The results showed that the EOs obtained from Thymus hirtus sp. algeriensis (rich on monoterpenoids, especially linalool at 17.62% and camphor at 13.82%) is significantly active against both L. major and L. infantum, whereas Ruta chalepensis EO (rich on 2-undecanone at 84.28%) is only active against L. infantum. Both oil extracts showed low cytotoxicity towards murine macrophages. The characteristic ratios (IC₈₀ Raw264.7 cells/IC₅₀ L. infantum and IC₈₀ Raw264.7 cells/IC₅₀ L. major) were, respectively, 2.7 and 1.57 for T. hirtus sp. algeriensis, and 1.34 and 0.19 for R. chalepensis. However, when measuring the antioxidant effects (DDPH method), the two latter EOs presented a moderate 2,2-diphenyl-2-picrylhydrazyl hydrate scavenging effects compared to EOs from Eucaliptus globulus, Pinus halepensis, Pituranthos tortuosus, Rosmarinus officinalis, Tetraclinis articulata or to BHT.

Leishmanicidal activity of saponins isolated from the leaves of Eclipta prostrata and Gymnema sylvestre

Objective:

To evaluate the leishmanicidal activity of saponin, dasyscyphin C of Eclipta prostrata and sapogenin, gymnemagenol from Gymnema sylvestre leaves under in vitro conditions.

Materials and Methods:

Dasyscyphin C/Gymnemagenol were dissolved in phosphate buffered saline (PBS) and diluted with liquid medium to obtain concentrations ranging from 1000 to 15 μg /ml. The leishmanicidal activity against leishmanial parasites, Leishmania major, Leishmania aethiopica and Leishmania tropica promastigotes was studied by the MTS assay.

Result:

The Dasyscyphin C isolated from E. prostrata showed good leishmanicidal activity at 1000μg/ml concentration, with the IC₅₀ value of 450μg/ml against L. major promastigote and the percentage of parasitic death was 73; whereas, gymnemagenol of G. sylvestre showed only 52% parasitic death at 1000 μg/ml concentration. The other Leishmania species, L. aethiopica and L. tropica promastigotes, were less sensitive to the saponins of E. prostrata and G. sylvestre.

Conclusion:

From this study, it can be concluded that the dasyscyphin C of E. prostrata has significant leishmanicidal activity against L. major promastigote.

Identification and characterization of genes involved in leishmania pathogenesis: the potential for drug target selection

Identifying and characterizing Leishmania donovani genes and the proteins they encode for their role in pathogenesis can reveal the value of this approach for finding new drug targets. Effective drug targets are likely to be proteins differentially expressed or required in the amastigote life cycle stage found in the patient. Several examples and their potential for chemotherapeutic disruption are presented. A pathway nearly ubiquitous in living cells targeted by anticancer drugs, the ubiquitin system, is examined. New findings in ubiquitin and ubiquitin-like modifiers in Leishmania show how disruption of those pathways could point to additional drug targets. The programmed cell death pathway, now recognized among protozoan parasites, is reviewed for some of its components and evidence that suggests they could be targeted for antiparasitic drug therapy. Finally, the endoplasmic reticulum quality control system is involved in secretion of many virulence factors. How disruptions in this pathway reduce virulence as evidence for potential drug targets is presented.

Trypanocidal properties, structure-activity relationship and computational studies of quinoxaline 1,4-di-N-oxide derivatives

Pyrazole and propenone quinoxaline derivatives were tested against intracellular forms of Leishmania peruviana and Trypanosoma cruzi. Both series were tested for toxicity against proliferative and non-proliferative cells. The pyrazole quinoxaline series was quite inactive against T. cruzi; however, the compound 2,6-dimethyl-3-f-quinoxaline 1,4-dioxide was found to inhibit 50% of Leishmania growth at 8.9 μM, with no impact against proliferative kidney cells and with low toxicity against THP-1 cells and murine macrophages. The compounds belonging to the propenone quinoxaline series were moderately active against T. cruzi. Among these compounds, two were particularly interesting, (2E)-1-(7-fluoro-3-methyl-quinoxalin-2-yl)-3-(3,4,5-trimethoxy-phenyl)-propenone and (2E)-3-(3,4,5-trimethoxy-phenyl)-1-(3,6,7-trimethyl-quinoxalin-2-yl)-propenone. The former possessed selective activity against proliferative cells (cancer and parasites) and was inactive against murine peritoneal macrophages; the latter was active against Leishmania and inactive against the other tested cells. Furthermore, insilico studies showed that both series respected Lipinski's rules and that they confirmed a linear correlation between trypanocidal activities and LogP. Docking studies revealed that compounds of the second series could interact with the poly (ADP-ribose) polymerase protein of Trypanosoma cruzi.

Current diagnosis and treatment of visceral leishmaniasis

Human visceral leishmaniasis (VL), a potentially fatal disease, is most prevalent in the Indian subcontinent, East Africa and South America. Definite diagnosis and effective treatment are the primary needs for the control of VL. Diagnosis of VL has typically relied on microscopic examination of bone marrow/splenic aspirate, but serology and molecular methods are now better alternatives. The conventional drugs for treatment of VL have limitations including unresponsiveness, relapse, specific toxicities and parenteral administration lasting for long durations. Moreover, they are less effective in HIV-VL-coinfected patients. Registration of miltefosine and paromomycin, and preferential pricing of AmBisome has offered more choices for monotherapy and combination therapy for VL. Combination therapy will increase treatment efficacy and prevent the development of resistance. In addition, active case finding and vector control strategies will also have a positive impact in the control of VL. This article critically addresses the currently available diagnostic and treatment regimens for the control of VL.

A curative immune profile one week after treatment of Indian kala-azar patients predicts success with a short-course liposomal amphotericin B therapy

Background

The present pilot study investigating the minimum dose for short-course single and double-dose treatment of kala-azar with an apparently new liposomal formulation of amphotericin B, Fungisome, led to identification of immunological components for early detection of success and/or failure to cure.

Methods

Patients were treated with 5, 7.5 (single-dose) and 10 mg/kg body weight (5 mg/kg double-dose) of Fungisome. Immunological investigations involving plasma cytokines and antigen-specific lymphoproliferation and cytokine responses from PBMCs were carried out before, 1 week after Fungisome treatment, at the time of relapse, and again after conventional amphotericin B treatment.

Results

At 1-month follow-up all the patients showed 100% initial cure. However, total doses of 5, 7.5 and 10 mg/kg Fungisome showed 60%, 50% and 90% cure, respectively, at 6-months posttreatment. Patients successfully cured demonstrated downregulation of IL-12 and IL-10 in plasma, and two-fold or more elevation of IFN-γ, IL-12 and TNF, and significant down-regulation of IL-10 and TGF-β in culture supernatants 1-week posttreatment irrespective of drug-dose. A differential immune profile, involving insignificant decline in IL-10 and IL-12 in plasma and negligible elevation of IFN-γ, IL-12 and TNF, and persistence of IL-10, despite decline in TGF-β in culture supernatants, in apparently cured individuals, corresponded with relapse within 6-months of treatment.

Conclusion

Immunological investigations revealed significant curative and non-curative immunomodulation 1-week posttreatment, correlating with successful cure and relapse, respectively. Although immune-correlation was dose-independent, almost consistent curative response in patients treated with the highest dose 10 mg/kg reflected a definitive impact of the higher-dose on the immune response.

Trial registration name and number

Clinical Trials Registry - India (CTRI) CTRI/2009/091/000764

Visceral leishmaniasis (VL) is a potentially fatal disease without treatment, characterized by prolonged fever, enlargement of spleen and liver, anaemia and weight loss. Treatment for VL is difficult, as it requires prolonged and painful application of toxic drugs with adverse side effects. It is therefore important to develop alternative satisfactory therapies for VL. Herein, we report the efficacy of a new liposomal formulation of amphotericin-B, Fungisome, and the immunological changes that take place 1-week after treatment. Patients treated with 5 and 7.5 mg/kg (single-dose) and 10 mg/kg (5 mg/kg double-dose) of Fungisome showed 60%, 50% and 90% successful cure at 6-month posttreatment, respectively. Successfully cured patients showed reduced IL-12 and IL-10 levels in the plasma and two-fold or more increase in Th1 type-cytokines IFN-γ, IL-12 and TNF, and down-regulation of immunosuppressive factors IL-10 and TGF-β in the culture supernatants, 1-week after treatment independent of drug-dose. Insignificant decrease of plasma IL-12 and IL-10, negligible increase of Th1-cytokines, and persistence of IL-10, despite decrease in TGF-β in culture supernatants, correlated with relapse within 6-months of treatment. These interesting results pave the way for further testing of this drug as a new alternative in the chemotherapy of leishmaniasis.

Antileishmanial high-throughput drug screening reveals drug candidates with new scaffolds

Drugs currently available for leishmaniasis treatment often show parasite resistance, highly toxic side effects and prohibitive costs commonly incompatible with patients from the tropical endemic countries. In this sense, there is an urgent need for new drugs as a treatment solution for this neglected disease. Here we show the development and implementation of an automated high-throughput viability screening assay for the discovery of new drugs against Leishmania. Assay validation was done with Leishmania promastigote forms, including the screening of 4,000 compounds with known pharmacological properties. In an attempt to find new compounds with leishmanicidal properties, 26,500 structurally diverse chemical compounds were screened. A cut-off of 70% growth inhibition in the primary screening led to the identification of 567 active compounds. Cellular toxicity and selectivity were responsible for the exclusion of 78% of the pre-selected compounds. The activity of the remaining 124 compounds was confirmed against the intramacrophagic amastigote form of the parasite. In vitro microsomal stability and cytochrome P450 (CYP) inhibition of the two most active compounds from this screening effort were assessed to obtain preliminary information on their metabolism in the host. The HTS approach employed here resulted in the discovery of two new antileishmanial compounds, bringing promising candidates to the leishmaniasis drug discovery pipeline.

Every year, more than 2 million people worldwide suffer from leishmaniasis, a neglected tropical disease present in 88 countries. The disease is caused by the single-celled protozoan parasite species of the genus Leishmania, which is transmitted to humans by the bite of the sandfly. The disease manifests itself in a broad range of symptoms, and its most virulent form, named visceral leishmaniasis, is lethal if not treated. Most of the few available treatments for leishmaniasis were developed decades ago and are often toxic, sometimes even leading to the patient's death. Furthermore, the parasite is developing resistance to available drugs, making the discovery and development of new antileishmanials an urgent need. To tackle this problem, the authors of this study employed the use of high-throughput technologies to screen a large library of small, synthetic molecules for their ability to interfere with the viability of Leishmania parasites. This study resulted in the discovery of two novel compounds with leishmanicidal properties and promising drug-like properties, bringing new candidates to the leishmaniasis drug discovery pipeline.

Screening of antileishmanial activity from marine sponge extracts collected off the Tunisian coast

The present study reports on the in vitro antileishmanial activity of two Ircinidae (Dictyoceratida, Demospongiae, Porifera) Ircinia spinosula and Sarcotragus sp. Sampled from the east coast of Tunisia. The ethyl acetate, dichloromethane, and aqueous extracts were tested against Leishmania major promastigotes. The anti-proliferative activity was checked using different extracts concentration during 72 h. We found that the IC50 (sub-inhibitory concentration) values ranged from 1.39 to 264.67 mug/ml. The most active extract was that from sarcotragus sp dichloromethane extract. Microscopic observations showed that the extracts promoted cellular alterations and induce enlargement of the nucleus and modification of the parasite shape. These promising results in relation with in vitro antileishmanial activity open the way for complementary investigation in order to purify and identify active molecules.

Alterations to the structure of Leishmania major induced by N-arylisoquinolines correlate with compound accumulation and disposition

Naphthylisoquinoline alkaloids equipped with a N,C-hetero-‘biaryl’ axis, and, in particular, simplified synthetic analogues thereof, kill intracellular Leishmania major at concentrations in the low submicromolar range, while being significantly less toxic to their major host cell, the macrophage, at the same concentrations. To further investigate their mechanism of action we evaluated the morphological and ultrastructural changes induced by specific N-arylisoquinolines in L. major, and the correlation of these changes with compound accumulation and disposition by the parasite. After 24 h of treatment with the synthetic arylisoquinolinium salts 3 or 4, dramatic structural changes and cell death were observed. Furthermore, the auto-fluorescent derivative salt 3 accumulates continually in intracellular compartments. Our results thus suggest that the leishmanicidal effect of arylisoquinolinium salts may involve their ability to accumulate and precipitate in intracellular organelles, form a huge vacuole and eventually promote cell lysis.

Anti-leishmanial and structure-activity relationship of ring substituted 3-phenyl-1-(1,4-di-N-oxide quinoxalin-2-yl)-2-propen-1-one derivatives

A series of ring substituted 3-phenyl-1-(1,4-di-N-oxide quinoxalin-2-yl)-2-propen-1-one derivatives were synthesized and tested for in vitro leishmanicidal activity against amastigotes of Leishmania amazonensis in axenical cultures and murine infected macrophages. Structure-activity relationships demonstrated the importance of a radical methoxy at position R3', R4' and R5'. (2E)-3-(3,4,5-trimethoxy-phenyl)-1-(3,6,7-trimethyl-1,4-dioxy-quinoxalin-2-yl)-propenone was the most active. Cytotoxicity on macrophages revealed that this product was almost six times more active than toxic.

Effect of Brazilian copaiba oils on Leishmania amazonensis

ETHNOPHARMACOLOGICAL RELEVANCE

Copaiba oil has been used in folk medicine since the 19th century. The use of copaiba oils to treat leishmaniasis is cited in several ethnopharmacological studies. Nevertheless, the potential antileishmania of copaiba oils had not been studied.

AIM OF THE STUDY

Eight different kinds of Brazilian copaiba oils were screened for antileishmanial activity.

MATERIALS AND METHODS

The antiproliferative effect of copaiba oil on promastigote and amastigote axenic were determined. To determine the survival index peritoneal macrophage were infected with promastigotes of Leishmania amazonensis and treated with copaiba oil. The cytotoxic effect of copaiba oil was assessed on macrophage strain J774G8 by assay of sulforhodamine B.

RESULTS

Copaiba oils showed variable levels of activity against promastigote forms with IC(50) values in the range between 5 and 22microg/mL. The most active oil was that from Copaifera reticulata (collected in Pará State, Brazil) with IC(50) values of 5, 15, and 20microg/mL for promastigote, axenic amastigote and intracellular amastigote forms, respectively. Amphotericin B showed IC(50) of 0.058 and 0.231microg/mL against promastigote and amastigote forms, respectively. Cytotoxicity assay showed that this copaiba oil obtained from Copaifera reticulata showed low cytotoxicity against J774G8 macrophages.

CONCLUSION

Copaiba oils showed significant activity against the parasite Leishmania amazonensis.

Antiparasitic, antineuroinflammatory, and cytotoxic polyketides from the marine sponge Plakortis angulospiculatus collected in Brazil

Investigation of the bioactive crude extract from the sponge Plakortis angulospiculatus from Brazil led to the isolation of plakortenone ( 1) as a new polyketide, along with five known polyketides ( 2- 6) previously isolated from other Plakortis sponges. The known polyketides were tested in antileishmanial, antitrypanosomal, antineuroinflammatory, and cytotoxicity assays. The results show that plakortide P ( 3) is a potent antiparasitic compound, against both Leishmania chagasi and Trypanosona cruzi, and exhibited antineuroinflammatory activity. The known polyketides 2- 6 were tested for cytotoxicity against four human cancer cell lines, but displayed only moderate cytotoxic activity.

In vitro antileishmanial activity of Adana propolis samples on Leishmania tropica: a preliminary study

Propolis (bee glue) is a natural resinous hive product, collected from various plant sources. It has attracted much attention as a useful substance applied in medicine due to its pharmacological activities. It was aimed to investigate the in vitro effects of an ethanolic extract of Adana propolis samples on the growth of Leishmania tropica. Parasite cells were treated with five concentrations (25, 50, 100, 50, 500, and 750 microg/ml) of the propolis. The number of promastigotes in each concentration was calculated using a hemocytometer slide at 24, 48, and 72 h after being harvested. In the experiments, it was determined that the concentrations up to 100 mug/ml of the propolis did not exhibit antileishmanial activity against the parasites cells. At these concentrations, there was no changes in terms of morphologically. In addition, there was no statistically significant difference in terms of cell count between control and these three groups (p > 0.05). However, in culture media containing the propolis samples at 250, 500, and 750-microg/ml concentrations, statistically significant differences in cell counts were observed, as compared to the control group (p < 0.05). Our results demonstrate that ethanolic extracts of Adana propolis samples reduce the proliferation of L. tropica parasites significantly.

Evaluation of the leishmanicidal activity of plants used by Peruvian Chayahuita ethnic group

AIM OF THE STUDY

A total of 27 ethanolic plant extracts from 27 species were screened for leishmanicidal activity in vitro against Leishmania amazonensis. Most of the selected species (19) are traditionally used by the Chayahuitas, an Amazonian Peruvian ethnic group, to treat skin affections and/or leishmaniasis.

MATERIAL AND METHODS

A colorimetric method based on the reduction of tetrazolium salt (MTT) was used to measure the viability of Leishmania amazonensis promastigote and amastigote stages.

RESULTS AND CONCLUSIONS

Only the leaves of two species of the Piperaceae family (Piper hispidum Sw., and Piper strigosum Trel.) showed good leishmanicidal activities (IC(50)<10 microg/ml against amastigotes). Roots of Tabernaemontana sananho Ruiz & Pav. (Apocynaceae), together with bark of Vismia tomentosa Ruiz & Pav. (Clusiaceae), fruits of Solanum straminifolium var straminifolium Jacq. (Solanaceae), and stems of Zamia lindenii Regel ex André (Cycadaceae) showed low activity against amastigote stage (IC(50) around 50 microg/ml). Of those only Tabernaemontana sananho displayed also good activity on promastigotes (IC(50)<10 microg/ml). Results are discussed herein, in relation with the traditional use of the plants and compared with other data from the relevant literature.

Structural Evidence of the Similarity of Sb(OH)3 and As(OH)3 with Glycerol: Implications for Their Uptake

Recent experimental results suggest that As(III) and Sb(III) transport in prokaryotes and eukaryotes might be facilitated by aquaglyceroporins. GlpF, the glycerol facilitator in Escherichia coli was the first to be identified as a trivalent metalloid transporter. Quantum calculations have been performed to study the possible existence of common structural properties between As(OH) 3 and Sb(OH) 3 and glycerol. Because the mechanism of substrate migration is primarily related to the successive formation of hydrogen bonds between the substrate and the hydrophilic part of the channel wall, this study has focused on the structural, thermodynamic, and electrostatic comparison of the main As(III) and Sb(III) compounds present in aqueous solution at physiological pH values, As(OH) 3 and Sb(OH) 3, with the glycerol conformation closest to the structures of these As- and Sb-containing compounds. This particular glycerol conformation has then been compared to three known experimental conformations of glycerol present in the protein channel. Besides their stoichiometry and electroneutral condition, As(OH) 3 and Sb(OH) 3 show very strong similarities to both each other and the studied conformation of the glycerol molecule: Namely, they show a similar charge distribution and a slightly smaller volume than glycerol. Their smaller size can be an additional advantage for the transit through the narrowest region of the GlpF channel. However, the metalloid hydroxyl groups lack the flexibility of glycerol, which probably helps this molecule to adapt its conformation to the topology of the GlpF channel.

Spirolactone iridoids might be responsible for the antileishmanial activity of a Peruvian traditional remedy made with Himatanthus sucuuba (Apocynaceae)

Extracts of seven medicinal plants used specifically against cutaneous leishmaniasis in the Madre de Dios region of Peru were evaluated in vitro against promastigote and axenic amastigote forms of Leishmania amazonensis. One of them showed interesting leishmanicidal activities (IC(50)=5 microg/ml in amastigotes). Bio-guided isolation of the stem bark's ethanol extract of Himatanthus sucuuba (Spruce ex Müll. Arg.) Woodson (Apocynaceae) afforded the spirolactone iridoids isoplumericin and plumericin. The latter showed a reduction of macrophage infection similar to that of the reference drug Amphotericin B (IC(50)=0.9 and 1 microM, respectively). These findings validate the traditional use of Himatanthus sucuuba in the treatment of cutaneous leishmaniasis (Uta) in Peru.

Prodrugs for the treatment of neglected diseases

Recently, World Health Organization (WHO) and Medicins San Frontieres (MSF) proposed a classification of diseases as global, neglected and extremely neglected. Global diseases, such as cancer, cardiovascular and mental (CNS) diseases represent the targets of the majority of the R&D efforts of pharmaceutical companies. Neglected diseases affect millions of people in the world yet existing drug therapy is limited and often inappropriate. Furthermore, extremely neglected diseases affect people living under miserable conditions who barely have access to the bare necessities for survival. Most of these diseases are excluded from the goals of the R&D programs in the pharmaceutical industry and therefore fall outside the pharmaceutical market. About 14 million people,mainly in developing countries, die each year from infectious diseases. From 1975 to 1999,1393 new drugs were approved yet only 1% were for the treatment of neglected diseases[3]. These numbers have not changed until now, so in those countries there is an urgent need for the design and synthesis of new drugs and in this area the prodrug approach is a very interesting field. It provides, among other effects, activity improvements and toxicity decreases for current and new drugs, improving market availability. It is worth noting that it is essential in drug design to save time and money, and prodrug approaches can be considered of high interest in this respect. The present review covers 20 years of research on the design of prodrugs for the treatment of neglected and extremely neglected diseases such as Chagas' disease (American trypanosomiasis), sleeping sickness (African trypanosomiasis), malaria, sickle cell disease, tuberculosis, leishmaniasis and schistosomiasis.

Use of click chemistry to define the substrate specificity of Leishmania beta-1,2-mannosyltransferases

Leishmania spp. are human pathogens that utilize a novel beta-1,2-mannan as their major carbohydrate reserve material. We describe a new approach that combines traditional substrate-modification methods and "click chemistry" to assemble a library of modified substrates that were used to qualitatively define the substrate tolerance of the Leishmania beta-1,2-mannosyltransferases responsible for beta-1,2-mannan biosynthesis. The library was assembled by using the highly selective copper(I)-catalysed cycloaddition reaction of azides and alkynes to couple an assortment of azide- and alkyne-functionalized small molecules with complementary alkyne- and azide-functionalized mannose derivatives. All mannose derivatives with alpha-orientated substituents on the anomeric carbon were found to act as substrates when incubated with a Leishmania mexicana particulate fraction containing GDP-mannose. In contrast, 6-substituted mannose derivatives were not substrates. Representative products formed from the library compounds were analysed by mass spectrometry, methylation linkage analysis and beta-mannosidase digestions and showed extension with up to four beta-1,2-linked mannosyl residues. This work provides insights into the substrate specificity of this new class of glycosyltransferases that can be applied to the development of highly specific tools and inhibitors for their study.

Aziridine-2,3-dicarboxylates, peptidomimetic cysteine protease inhibitors with antileishmanial activity

Chemotherapy of leishmaniasis is mainly based on antimonials. However, they are extremely toxic and cause serious side effects, and there is a worldwide increasing frequency of chemoresistance to antimonials. These issues emphasize the urgent need for affordable alternative drugs against leishmaniasis. Leishmania cysteine proteases are essential for parasite growth, differentiation, pathogenicity, and virulence and are thus attractive targets for combating leishmaniasis. Herein we demonstrate that the cysteine protease inhibitors aziridine-2,3-dicarboxylates 13b and 13e impaired promastigote growth at mid-micromolar concentrations and decreased the infection rate of peritoneal macrophages at concentrations 8- to 13-fold lower than those needed to inhibit parasite replication. Simultaneous treatment of infected cells with compound 13b and gamma interferon resulted in an even further reduction of the concentration needed for a significant decrease in macrophage infection rate. Notably, treatment with the compounds alone modulated the cytokine secretion of infected macrophages, with increased levels of interleukin-12 and tumor necrosis factor alpha. Furthermore, the decreased infection rate in the presence of compound 13b correlated with increased nitric oxide production by macrophages. Importantly, at the concentrations used herein, compounds 13b and 13e were not toxic against fibroblasts, macrophages, or dendritic cells. Together, these results suggest that the aziridine-2,3-dicarboxylates 13b and 13e are potential antileishmanial lead compounds with low toxicity against host cells and selective antiparasitic effects.

Arylanthranilodinitriles: A new biaryl class of antileishmanial agents

A series of anthranilodinitrile-based biaryls were synthesized and evaluated in vitro against extracellular promastigotes and intracellular amastigotes of Leishmania donovani. Among various screened compounds, a biaryl with trifluoromethyl group 5f showed 83% inhibition against promastigotes and 70% inhibition against amastigotes of L. donovani at 8 and 20microg/mL concentrations, respectively.

Progressive peak clustering in GC-MS Metabolomic experiments applied to Leishmania parasites

MOTIVATION

A common problem in the emerging field of metabolomics is the consolidation of signal lists derived from metabolic profiling of different cell/tissue/fluid states where a number of replicate experiments was collected on each state.

RESULTS

We describe an approach for the consolidation of peak lists based on hierarchical clustering, first within each set of replicate experiments and then between the sets of replicate experiments. The problems of finding the dendrogram tree cutoff which gives the optimal number of peak clusters and the effect of different clustering methods were addressed. When applied to gas chromatography-mass spectrometry metabolic profiling data acquired on Leishmania mexicana, this approach resulted in robust data matrices which completely separated the wild-type and two mutant parasite lines based on their metabolic profile.

Characterisation of a Leishmania mexicana knockout lacking guanosine diphosphate-mannose pyrophosphorylase

In eukaryotes, the enzyme GDP-mannose pyrophosphorylase (GDP-MP) is essential for the formation of GDP-mannose, the donor of activated mannose for all glycosylation reactions. Unlike other eukaryotes, where deletion of GDP-mannose pyrophosphorylase is lethal, deletion of this gene in Leishmania mexicana has no effect on viability, but leads to the generation of avirulent parasites. In this study, we show that the null mutants have a perturbed morphology and cytokinesis, retarded growth and increased adherence to the substratum where they form large colonies. The null mutants attach avidly to mouse macrophages, but unlike the wild type organisms, they do not bind to the complement receptor 3 and are slow to induce phagocytosis. Once internalised, they localise to the phagolysosome, but in contrast to wild type organisms which transform into the intracellular amastigote and establish in the macrophage, they are cleared by 24 h in culture and by 5 h in vivo. The null mutants are hypersensitive to human but not mouse complement and to temperature and acidic pH. Surprisingly, in view of the lack of several known host-protective antigens, injection of the mutant parasites into BALB/c mice confers significant and long lasting protection against infection, suggesting that these temperature sensitive mutants are an attractive candidate for a live attenuated vaccine.

Antileishmanial activity, cytotoxicity and QSAR analysis of synthetic dihydrobenzofuran lignans and related benzofurans

A series of synthetic dihydrobenzofuran lignans and related benzofurans were evaluated for their cytotoxicity in a screening panel consisting of various human tumour cell lines, and for their antiprotozoal activity against L. donovani (axenic amastigotes), chloroquine resistant Plasmodium falciparum (strain K1), Trypanosoma brucei rhodesiense and T. cruzi, and for cytotoxicity on L6 cells. No promising cytotoxicities against human tumour cell lines were observed for newly synthesised compounds, but the dimerisation product of some lipophylic esters of caffeic acid, such as compound 2g, showed a high activity against chloroquine-resistant P. falciparum (strain K1) (IC50 0.43 microg/mL) and L. donovani (axenic amastigotes) (IC50 0.12 microg/mL), which was confirmed in an infected macrophage assay (IC50 0.19 microg/mL). QSAR models for the cytotoxic and antileishmanial activity were generated using Quasar receptor surface modelling.

Synthesis, antimalarial, antileishmanial, and antimicrobial activities of some 8-quinolinamine analogues

In the present communication, newly synthesized 8-quinolinamines (25-27) related to previously reported 2-tert-butylprimaquine (2) were evaluated for their in vitro antimalarial activity against chloroquine sensitive and resistant Plasmodium falciparum strains, in vivo antimalarial activity against P. berghei infected mice, in vitro antileishmanial activity against Leishmania donovani, in vitro antimicrobial activity against various fungi and bacteria, and cytotoxicity in a panel of mammalian cell lines. No promising cytotoxicities were observed for compounds reported herein. Analogue 25 was found to exhibit curative antimalarial activity at a dose of 25 mg/kg/dayx4 in a P. berghei infected mice model, and produced suppressive activity at a lower dose of 10 mg/kg/dayx4. In vitro antileishmanial activities (IC50 and IC90) comparable to standard drug pentamidine were exhibited by all synthesized 8-quinolinamines 25-27. At the same time, promising antibacterial and antifungal activities were also observed for synthesized compounds against a panel consisting of several bacteria and fungi.

Insight into the self-association of key enzymes from pathogenic species

Self-association of protein monomers to higher-order oligomers plays an important role in a plethora of biological phenomena. The classical biophysical technique of analytical ultracentrifugation is a key method used to measure protein oligomerisation. Recent advances in sedimentation data analysis have enabled the effects of diffusion to be deconvoluted from sample heterogeneity, permitting the direct identification of oligomeric species in self-associating systems. Two such systems are described and reviewed in this study. First, we examine the enzyme dihydrodipicolinate synthase (DHDPS), which crystallises as a tetramer. Wild-type DHDPS plays a critical role in lysine biosynthesis in microbes and is therefore an important antibiotic target. To confirm the state of association of DHDPS in solution, we employed sedimentation velocity and sedimentation equilibrium studies in an analytical ultracentrifuge to show that DHDPS exists in a slow dimer-tetramer equilibrium with a dissociation constant of 76 nM. Second, we review works describing the hexamerisation of GDP-mannose pyrophosphorylase (GDP-MP), an enzyme that plays a critical role in mannose metabolism in Leishmania species. Although the structure of the GDP-MP hexamer has not yet been determined, we describe a three-dimensional model of the hexamer based largely on homology with the uridyltransferase enzyme, Glmu. GDP-MP is a novel drug target for the treatment of leishmaniasis, a devastating parasitic disease that infects more than 12 million people worldwide. Given that both GDP-MP and DHDPS are only active in their oligomeric states, we propose that inhibition of the self-association of critical enzymes in disease is an emerging paradigm for therapeutic intervention.

Antimony-induced cardiomyopathy in guinea-pig and protection by L-carnitine

Antimony (Sb) is the mainstay for the treatment of Leishmaniasis. It has serious, often lethal, cardiovascular side effects. The objective of this study was to examine the effects of Sb treatment upon the electrocardiogram (ECG), myocyte contractility (assessed by monitoring sarcomere length during field stimulation), whole-cell action potential (AP) and calcium current (I(Ca)) of the guinea-pig and to evaluate L-carnitine as a cardioprotective agent. Guinea-pigs received daily injections of either saline, Sb(V), Sb(III), L-carnitine or L-carnitine with Sb(III). Eight lead ECGs were recorded under halothane anaesthesia every 4 days. At the end of each treatment regime, animals were killed and ventricular myocytes were enzymatically isolated. Treatment with Sb(V) for 26 days prolonged the QT interval of the ECG. Treatment with Sb(III) was lethal within 2 days for approximately 50% of the animals. The survivors showed ECG alterations similar to those described in man: T wave flattening and/or inversion, depression of the ST segment, and elongation of RR and QT intervals. Their ventricular myocytes showed impaired contraction responses to changes in stimulus frequency, elongated AP and reduced I(Ca). Combined treatment with L-carnitine and Sb(III) delayed mortality. Prior treatment with L-carnitine followed by combined treatment with L-carnitine and Sb(III) reduced mortality to <10% over 12 days and these animals showed normal ECG. Their myocytes showed normal contractility and AP. It is concluded that L-carnitine has a preventive cardioprotective role against antimony-induced cardiomyopathy. The mechanism of action of L-carnitine may be to counter oxidative stress caused by Sb(III).

Genes and Susceptibility to Leishmaniasis

Leishmania are digenetic protozoa which inhabit two highly specific hosts, the sandfly where they grow as motile, flagellated promastigotes in the gut, and the mammalian macrophage where they grow intracellularly as non-flagellated amastigotes. Leishmaniasis is the outcome of an evolutionary 'arms race' between the host's immune system and the parasite's evasion mechanisms which ensure survival and transmission in the population. The spectrum of disease manifestations and severity reflects the interaction between the genome of the host and that of the parasite, and the pathology is caused by a combination of host and parasite molecules. This chapter examines the genetic basis of host susceptibility to disease in humans and animal models. It describes the genetic tools used to map and identify susceptibility genes, and the lessons learned from murine and human cutaneous leishmaniasis.