Recent advances in leishmaniasis treatment

In vitro antileishmanial and antimalarial activity of selected plants of Nepal

Background:

Nepal is very rich in biodiversity, and no extensive effort has yet been carried out to screen plants that are used by traditional healers against parasitic diseases. The aim of this study was to evaluate the in vitro antileishmanial and antimalarial activity of crude methanolic or ethanolic extracts of 29 plant species that are currently used by local people of Nepal for treating different ailments.

Methods:

Crude extracts of leaves, twigs, aerial parts, and/or roots of the selected plants were evaluated for in vitro inhibitory activity against intracellular amastigotes of Leishmania infantum and against erythrocytic stages of Plasmodium falciparum. To determine the selectivity index (SI), cytotoxicity was assessed on MRC-5 cells in parallel.

Results:

Three plant species, namely Phragmites vallatoria and Ampelocissus tomentosa, for which no antiprotozoal activity has previously been reported, and Terminalia chebula revealed antiprotozoal activity. The extract of A. tomentosa exhibited moderate activity against L. infantum with an inhibitory concentration 50% (IC₅₀) of 13.2 ± 4.3 µg/ml and SI >3, while T. chebula exhibited fairly good antiplasmodial activity with IC₅₀ values of 4.5 ± 2.4 µg/ml and SI values >5.

Conclusion:

In countries like Nepal, where the current health system is unable to combat the burden of endemic parasitic diseases, evaluation of local plants as a potential source of the drug can help in expanding the treatment options. The extent of untapped resources available in these countries provides an opportunity for future bioprospecting.

Clinical Response with intralesional Amphotericin B in the treatment of old world cutaneous leishmaniasis: a preliminary report

Cutaneous leishmaniasis (CL) is a vector-borne tropical disease caused by a heterogeneous group of protozoan parasites that belong to the genus Leishmania. With an annual incidence of 1.5 million new cases, CL is a global health concern mainly in developing countries. The treatment options for CL are numerous but none is optimal. Pentavalent antimonials despite their side effects remain the preferred choice since decades. Alternate new treatment options are being explored to expand the therapeutic armamentarium of CL. In this study, we intend to describe our therapeutic experience with intralesional amphotericin B in the treatment of CL in a series of Indian patients, hitherto not commonly used in old world CL (OWCL). We also endeavour to review the literature on the use of amphotericin B in OWCL. Five consecutive patients diagnosed with cutaneous leishmansis at the out-patient department of Dermatology, Government Medical College, Jammu were treated with weekly injections of intralesional amphotericin B (2.5 mg/mL). Treatment response was assessed at each visit and the cases were followed up for 6 months. All the five patients responded well to the treatment and remained recurrence-free during follow-up. Intralesional amphotericin B was found to be safe and effective treatment for OWCL. Large randomized control trials need to be conducted to establish its efficacy.

Leishmania major Infection-Induced VEGF-A/VEGFR-2 Signaling Promotes Lymphangiogenesis That Controls Disease

Cutaneous leishmaniasis causes a spectrum of diseases from self-healing to severe nonhealing lesions. Defining the factors contributing to lesion resolution may help in developing new therapies for those patients with chronic disease. We found that infection with Leishmania major increases the expression of vascular endothelial growth factor-A and vascular endothelial growth factor receptor (VEGFR)-2 and is associated with significant changes in the blood and lymphatic vasculature at the site of infection. Ab blockade of VEGFR-2 during infection led to a reduction in lymphatic endothelial cell proliferation and simultaneously increased lesion size without altering the parasite burden. These data show that L. major infection initiates enhanced vascular endothelial growth factor-A/VEGFR-2 signaling and suggest that VEGFR-2-dependent lymphangiogenesis is a mechanism that restricts tissue inflammation in leishmaniasis.

Structure-guided discovery of thiazolidine-2,4-dione derivatives as a novel class of Leishmania major pteridine reductase 1 inhibitors

Leishmania major, as other protozoan parasites, plague human kind since pre-historic times but it remains a worldwide ailment for which the therapeutic arsenal remains scarce. Although L. major is pteridine- and purine-auxotroph, well-established folate biosynthesis inhibitors, such as methotrexate, have poor effect over the parasite survival. The lack of efficiency is related to an alternative biochemical pathway in which pteridine reductase 1 (PTR1) plays a major role. For this reason, this enzyme has been considered a promising target for anti-leishmanial drug development and several inhibitors that share the substrate scaffold have been reported. In order to design a novel class of PTR1 inhibitors, we employed the thiazolidinone ring as a bioisosteric replacement for pteridine/purine ring. Among seven novel thiazolidine-2,4-dione derivatives reported herein, 2d was identified as the most promising lead by thermal shift assays (ΔTm = 11 °C, p = 0,01). Kinetic assays reveal that 2d has IC50 = 44.67 ± 1.74 μM and shows a noncompetitive behavior. This information guided docking studies and molecular dynamics simulations (50 000 ps) that supports 2d putative binding profile (H-bonding to Ser-111 and Leu-66) and shall be useful to design more potent inhibitors.

(+)-Spectaline, a Piperidine Alkaloid from Senna spectabilis DC. Effective in Reducing the In Vitro Infection of Leishmania major

Senna spectabilisis known to have antimicrobial, laxative, antiulcerogenic, analgesic, and anti-inflammatory properties in folk medicine. Piperidine alkaloids extracted from various parts of this plant have been shown to have anticonvulsant (iso-6-spectaline), antinociceptive [(-)-spectaline] and lipid peroxidation [(+)-3-O-feruloylcassine, (-)-spectaline and (-)-3-O-acetylspectaline] activities. In our study, the ethyl acetate extract fromS. spectabilisexhibited antileishmanial activity via intracellular promastigote assay or leishmanicidal assay and was further fractionated by using bioassay-guided isolation approach. The antiprotozoal principle was isolated from the ethyl acetate portion through solvent fractionation and a few series of chromatographic processes. The isolated active compound 1 was identified as (+)-spectaline on the basis of its spectral analysis (MS, 1D & 2D NMR) with EC50value of 0.063 ± 0.005 µM for antileishmanial activity and selectivity index of 3.76.

Clinical and Parasitological Features of Patients with American Cutaneous Leishmaniasis that Did Not Respond to Treatment with Meglumine Antimoniate

BACKGROUND

American cutaneous leishmaniasis (ACL) is a complicated disease producing about 67.000 new cases per year. The severity of the disease depends on the parasite species; however in the vast majority of cases species confirmation is not feasible. WHO suggestion for ACL produced by Leishmania braziliensis, as first line treatment, are pentavalent antimonial derivatives (Glucantime or Sodium Stibogluconate) under systemic administration. According to different authors, pentavalent antimonial derivatives as treatment for ACL show a healing rate of about 75% and reasons for treatment failure are not well known.

METHODS

In order to characterise the clinical and parasitological features of patients with ACL that did not respond to Glucantime, a cross-sectional observational study was carried out in a cohort of 43 patients recruited in three of the Colombian Army National reference centers for complicated ACL. Clinical and paraclinical examination, and epidemiological and geographic information were recorded for each patient. Parasitological, histopathological and PCR infection confirmation were performed. Glucantime IC50 and in vitro infectivity for the isolated parasites were estimated.

RESULTS

Predominant infecting Leishmania species corresponds to L. braziliensis (95.4%) and 35% of the parasites isolated showed a significant decrease in in vitro Glucanatime susceptibility associated with previous administration of the medicament. Lesion size and in vitro infectivity of the parasite are negatively correlated with decline in Glucantime susceptibility (Spearman: r = (-)0,548 and r = (-)0,726; respectively).

CONCLUSION

A negative correlation between lesion size and parasite resistance is documented. L. braziliensis was found as the main parasite species associated to lesion of patients that underwent treatment failure or relapse. The indication of a second round of treatment in therapeutic failure of ACL, produced by L. braziliensis, with pentavalent antimonial derivatives is discussable.

Activity of a novel sulfonamide compound 2-nitro-N-(pyridin-2-ylmethyl)benzenesulfonamide against Leishmania donovani

New treatments for visceral leishmaniasis, caused by Leishmania donovani, are needed to overcome sustained toxicity, cost, and drug resistance. The aim of this study was to evaluate the therapeutic effects of 2-nitro-N-(pyridin-2-ylmethyl)benzenesulfonamide (2NB) against promastigote and amastigote forms of L. donovani and examine its effect in combination with amphotericin B (AmB) against AmB-resistant clinical isolates. Effects were assessed against extracellular promastigotes in vitro and intracellular amastigotes in L. donovani-infected macrophages. Levels of inducible nitric oxide and Th1 and Th2 cytokines were measured in infected 2NB-treated macrophages, and levels of reactive oxygen species and NO were measured in 2NB-treated macrophages. 2NB was active against promastigotes and intracellular amastigotes with 50% inhibitory concentration values of 38.5±1.5 µg/mL and 86.4±2.4 µg/mL, respectively. 2NB was not toxic to macrophages. Parasite titer was reduced by >85% in infected versus uninfected macrophages at a 2NB concentration of 120 µg/mL. The parasiticidal activity was associated with increased levels of Th1 cytokines, NO, and reactive oxygen species. Finally, 2NB increased the efficacy of AmB against AmB-resistant L. donovani. These results demonstrate 2NB to be an antileishmanial agent, opening up a new avenue for the development of alternative chemotherapies against visceral leishmaniasis.

In Vitro and In Vivo Activities of 2,3-Diarylsubstituted Quinoxaline Derivatives against Leishmania amazonensis

Leishmaniasis is endemic in 98 countries and territories worldwide. The therapies available for leishmaniasis have serious side effects, thus prompting the search for new therapies. The present study investigated the antileishmanial activities of 2,3-diarylsubstituted quinoxaline derivatives against Leishmania amazonensis The antiproliferative activities of 6,7-dichloro-2,3-diphenylquinoxaline (LSPN329) and 2,3-di-(4-methoxyphenyl)-quinoxaline (LSPN331) against promastigotes and intracellular amastigotes were assessed, and the cytotoxicities of LSPN329 and LSPN331 were determined. Morphological and ultrastructural alterations were examined by electron microscopy, and biochemical alterations, reflected by the mitochondrial membrane potential (ΔΨm), mitochondrial superoxide anion (O2·(-)) concentration, the intracellular ATP concentration, cell volume, the level of phosphatidylserine exposure on the cell membrane, cell membrane integrity, and lipid inclusions, were evaluated. In vivo antileishmanial activity was evaluated in a murine cutaneous leishmaniasis model. Compounds LSPN329 and LSPN331 showed significant selectivity for promastigotes and intracellular amastigotes and low cytotoxicity. In promastigotes, ultrastructural alterations were observed, including an increase in lipid inclusions, concentric membranes, and intense mitochondrial swelling, which were associated with hyperpolarization of ΔΨm, an increase in the O2·(-) concentration, decreased intracellular ATP levels, and a decrease in cell volume. Phosphatidylserine exposure and DNA fragmentation were not observed. The cellular membrane remained intact after treatment. Thus, the multifactorial response that was responsible for the cellular collapse of promastigotes was based on intense mitochondrial alterations. BALB/c mice treated with LSPN329 or LSPN331 showed a significant decrease in lesion thickness in the infected footpad. Therefore, the antileishmanial activity and mitochondrial mechanism of action of LSPN329 and LSPN331 and the decrease in lesion thickness in vivo brought about by LSPN329 and LSPN331 make them potential candidates for new drug development for the treatment of leishmaniasis.

Nerolidol: A Sesquiterpene Alcohol with Multi-Faceted Pharmacological and Biological Activities

Nerolidol (3,7,11-trimethyl-1,6,10-dodecatrien-3-ol) is a naturally occurring sesquiterpene alcohol that is present in various plants with a floral odor. It is synthesized as an intermediate in the production of (3E)-4,8-dimethy-1,3,7-nonatriene (DMNT), a herbivore-induced volatile that protects plants from herbivore damage. Chemically, nerolidol exists in two geometric isomers, a trans and a cis form. The usage of nerolidol is widespread across different industries. It has been widely used in cosmetics (e.g., shampoos and perfumes) and in non-cosmetic products (e.g., detergents and cleansers). In fact, U.S. Food and Drug Administration (FDA) has also permitted the use of nerolidol as a food flavoring agent. The fact that nerolidol is a common ingredient in many products has attracted researchers to explore more medicinal properties of nerolidol that may exert beneficial effect on human health. Therefore, the aim of this review is to compile and consolidate the data on the various pharmacological and biological activities displayed by nerolidol. Furthermore, this review also includes pharmacokinetic and toxicological studies of nerolidol. In summary, the various pharmacological and biological activities demonstrated in this review highlight the prospects of nerolidol as a promising chemical or drug candidate in the field of agriculture and medicine.

Cutaneous and mucocutaneous leishmaniasis: Differential diagnosis, diagnosis, histopathology, and management

The diagnosis of leishmaniasis can be challenging because it mimics both infectious and malignant conditions. A misdiagnosis may lead to an unfavorable outcome. Using culture, histologic, and/or polymerase chain reaction study results, a diagnosis of leishmaniasis can be established and treatment initiated. Appropriate management requires an accurate diagnosis, which often includes identification of the specific etiologic species. Different endemic areas have varying sensitivities to the same medication, even within individual species. Species identification may be of practical value, because infections with select species have a substantial risk of visceral involvement. In addition, HIV and otherwise immunocompromised patients with leishmaniasis have a propensity for diffuse cutaneous leishmaniasis. For most New World Leishmania species, parenteral antimonial drugs remain the first line of therapy, while Old World species are easily treated with physical modalities. Historically, live organism vaccination has been used and is effective in preventing leishmaniasis, but results in an inoculation scar and an incubation period that may last for years. A more effective method of vaccination would be welcome.

Mucosal leishmaniasis in Brazilian patients: two case reports with similar clinical presentation and different approaches

Mucosal leishmaniasis is a chronic infection that affects the upper respiratory tract and/or the oral mucosa caused by Leishmania protozoan parasites. We present two cases of oral leishmaniasis and discuss the different diagnostic strategies and treatment. In both cases, the patients were male, 60 and 94 years of age, and presented with lesions on the soft palate. In the first patient, the final diagnosis was made on the basis of histopathologic examination. In the second case, polymerase chain reaction and Montenegro skin test were necessary to confirm the diagnosis. The first patient was treated with meglumine antimoniate (Glucantime), and the lesions healed after 2 months. In the second case, the patient received treatment with liposomal amphotericin B but later died as a result of generalized infection. Mucosal leishmaniasis is a highly disfiguring disease. Early diagnosis is important to prevent a lethal outcome.

Oral Efficacy of Apigenin against Cutaneous Leishmaniasis: Involvement of Reactive Oxygen Species and Autophagy as a Mechanism of Action

Background

The treatment for leishmaniasis is currently based on pentavalent antimonials and amphotericin B; however, these drugs result in numerous adverse side effects. The lack of affordable therapy has necessitated the urgent development of new drugs that are efficacious, safe, and more accessible to patients. Natural products are a major source for the discovery of new and selective molecules for neglected diseases. In this paper, we evaluated the effect of apigenin on Leishmania amazonensis in vitro and in vivo and described the mechanism of action against intracellular amastigotes of L. amazonensis.

Methodology/Principal Finding

Apigenin reduced the infection index in a dose-dependent manner, with IC₅₀ values of 4.3 μM and a selectivity index of 18.2. Apigenin induced ROS production in the L. amazonensis-infected macrophage, and the effects were reversed by NAC and GSH. Additionally, apigenin induced an increase in the number of macrophages autophagosomes after the infection, surrounding the parasitophorous vacuole, suggestive of the involvement of host autophagy probably due to ROS generation induced by apigenin. Furthermore, apigenin treatment was also effective in vivo, demonstrating oral bioavailability and reduced parasitic loads without altering serological toxicity markers.

Conclusions/Significance

In conclusion, our study suggests that apigenin exhibits leishmanicidal effects against L. amazonensis-infected macrophages. ROS production, as part of the mechanism of action, could occur through the increase in host autophagy and thereby promoting parasite death. Furthermore, our data suggest that apigenin is effective in the treatment of L. amazonensis-infected BALB/c mice by oral administration, without altering serological toxicity markers. The selective in vitro activity of apigenin, together with excellent theoretical predictions of oral availability, clear decreases in parasite load and lesion size, and no observed compromises to the overall health of the infected mice encourage us to supports further studies of apigenin as a candidate for the chemotherapeutic treatment of leishmaniasis.

Leishmaniasis is an important neglected disease caused by protozoa of the genus Leishmania and affects more than 12 million people worldwide. Pentavalent antimonials and amphotericin B have been used for decades to treat leishmaniasis; however, these drugs result in numerous adverse side effects, have variable efficacy and are subject to parasite resistance. The lack of suitable therapy necessitates the development of novel antileishmanial compounds. In this study, we investigated the antileishmanial activity of apigenin in vitro and in vivo and described the mechanism of action against intracellular amastigotes of Leishmania amazonensis. Apigenin reduced the infection index in a dose-dependent manner and increased reactive oxygen species (ROS) generation. Additionally, apigenin induced an increase in the number of macrophages autophagosomes after the infection, surrounding the parasitophorous vacuole, suggestive of the involvement of host autophagy probably due to ROS generation induced by apigenin. Furthermore, treatment with apigenin was also effective in vivo, showing oral bioavailability and significantly reducing lesion sizes and parasite burden without altering serological toxicity markers.

Leptin augments protective immune responses in murine macrophages and enhances potential of miltefosine against experimental visceral leishmaniasis

Adverse side effects and drug resistance issues are the two most important drawbacks which influence the widespread use of existing antileishmanial drugs. Use of immune stimulating agent with standard antileishmanial might be helpful to minimize the toxic effect of drug, shorten the dose regimen and delay the emergence of resistance. In the present study, we explored the in vitro immunomodulatory potential of an immunomodulator, leptin with lower concentration of standard drug, miltefosine. The level of Th1/Th2 cytokines, production of nitric oxide and reactive oxygen species and phagocytic activity was assessed by ELISA, Griess reaction and flow cytometric analysis, respectively. Leptin at a concentration of 15μg/mL showed heightened level of Th1 cytokines and nitric oxide generation from murine macrophages (J-774A.1 cells). Leptin (15μg/mL) also reduces the effective concentration of miltefosine by 2-folds from 7.5μM to 3.7μM. When given in conjunction with lower concentration of miltefosine (4μM), leptin (15μg/mL) significantly (***p<0.001) elevated the level of IL-12 (7.7 fold), TNF-α (8.1 fold) and nitric oxide (6.6 fold) along with markedly (***p<0.001) suppressed level of IL-10 and TGF-β when compared with untreated infected macrophages. Leptin plus miltefosine also induces the phagocytic ability (**p<0.01) of macrophages in comparison to leptin alone and miltefosine alone treated groups. These finding illustrate that leptin activates host macrophages to generate protective immune response for the successful elimination of Leishmania parasite at lower concentration of miltefosine and has potential for further exploration in experimental animal model of visceral leishmaniasis (VL).

Development of 4-sulfated N-acetyl galactosamine anchored chitosan nanoparticles: A dual strategy for effective management of Leishmaniasis

The present investigation reports the modification of chitosan nanoparticles with a ligand 4-sulfated N-acetyl galactosamine (4-SO4GalNAc) for efficient chemotherapy in leishmaniasis (SCNPs) by using dual strategy of targeting. These (SCNPs) were loaded with amphotericin B (AmB) for specific delivery to infected macrophages. Developed AmB loaded SCNPs (AmB-SCNPs) had mean particle size of 333 ± 7 nm, and showed negative zeta potential (-13.9 ± 0.016 mV). Flow cytometric analysis revealed enhanced uptake of AmB-SCNPs in J774A.1, when compared to AmB loaded unmodified chitosan NPs (AmB-CNPs). AmB-SCNPs provide significantly higher localization of AmB in liver and spleen as compared to AmB-CNPs after i.v. administration. The study stipulates that 4-SO4GalNAc assures of targeting, resident macrophages. Highly significant anti-leishmanial activity (P<0.05 compared with AmB-CNPs) was observed with AmB-SCNPs, causing 75.30 ± 3.76% inhibition of splenic parasitic burdens. AmB-CNPs and plain AmB caused only 63.89 ± 3.44% and 47.56 ± 2.37% parasite inhibition, respectively, in Leishmania-infected hamsters (P<0.01 for AmB-SCNPs versus plain AmB and AmB-CNPs versus plain AmB).

Membrane-Active Small Molecules: Designs Inspired by Antimicrobial Peptides

Infectious diseases continue to be one of the major contributors to human morbidity. The rapid rate at which pathogenic microorganisms have developed resistance against frontline antimicrobials has compelled scientists to look for new alternatives. Given their vast antimicrobial repertoire, substantial research effort has been dedicated toward the development of antimicrobial peptides (AMPs) as alternative drugs. However, inherent limitations of AMPs have driven substantial efforts worldwide to develop synthetic mimics of AMPs. This review focuses on the progress that has been made toward the development of small molecules that emulate the properties of AMPs, both in terms of design and biological activity. Herein we provide an extensive discussion of the structural features of various designs and we examine biological properties that have been exploited. Furthermore, we raise a number of questions for which the field has yet to provide solutions and discuss possible future research directions that remain either unexploited or underexploited.

Leishmania tarentolae secreting the sand fly salivary antigen PpSP15 confers protection against Leishmania major infection in a susceptible BALB/c mice model

Cutaneous leishmaniasis is a zoonotic, vector-borne disease causing a major health problem in several countries. No vaccine is available and there are limitations associated with the current therapeutic regimens. Immune responses to sand fly saliva have been shown to protect against Leishmania infection. A cellular immune response to PpSP15, a protein from the sand fly Phlebotomus papatasi, was sufficient to control Leishmania major infection in mice. This work presents data supporting the vaccine potency of recombinant live non-pathogenic Leishmania (L.) tarentolae secreting PpSP15 in mice and its potential as a new vaccine strategy against L. major. We generated a recombinant L. tarentolae-PpSP15 strain delivered in the presence of CpG ODN and evaluated its immunogenicity and protective immunity against L. major infection in BALB/c mice. In parallel, different vaccination modalities using PpSP15 as the target antigen were compared. Humoral and cellular immune responses were evaluated before and at three and eight weeks after challenge. Footpad swelling and parasite load were assessed at eight and eleven weeks post-challenge. Our results show that vaccination with L. tarentolae-PpSP15 in combination with CpG as a prime-boost modality confers strong protection against L. major infection that was superior to other vaccination modalities used in this study. This approach represents a novel and promising vaccination strategy against Old World cutaneous leishmaniasis.

Antileishmanial Activity of Compounds Isolated from Sassafras albidum

Leishmaniasis is a neglected tropical disease caused by Leishmania parasitic protozoa, which currently lacks efficient treatment. Natural products have shown promise as a potential source for antiprotozoal drugs. This work focuses on the antileishmanial potential of Sassafras albidum (Lauraceae) bark extract. The crude bark extract of S. albidum showed excellent antileishmanial activity with an IC50 value less than 12.5 μg/mL against promastigotes of L. amazonensis. The chloroform stem bark extract of S. albidum was subjected to preparative column chromatography. Five compounds were isolated, purified by recrystallization, and identified as sesamin, spinescin, β-sitosterol, hexatriacontanal, and 1-triacontanol. Antileishmanial and cytotoxic screening were performed on these compounds. Sesamin exhibited the best activity against L. amazonensis with an IC50 of 15.8 μg/mL and was not cytotoxic to mouse macrophage cells ( CC50 > 100 μg/mL).

Molecular descriptors calculation as a tool in the analysis of the antileishmanial activity achieved by two series of diselenide derivatives. An insight into its potential action mechanism

A molecular modeling study has been carried out on two previously reported series of symmetric diselenide derivatives that show remarkable antileishmanial in vitro activity against Leishmania infantum intracellular amastigotes and in infected macrophages (THP-1 cells), in addition to showing favorable selectivity indices. Series 1 consists of compounds that can be considered as central scaffold constructed with a diaryl/dialkylaryl diselenide central nucleus, decorated with different substituents located on the aryl rings. Series 2 consists of compounds constructed over a diaryl diselenide central nucleus, decorated in 4 and 4' positions with an aryl or heteroaryl sulfonamide fragment, thus forming the diselenosulfonamide derivatives. With regard to the diselenosulfonamide derivatives (2 series), the activity can be related, as a first approximation, with (a) the ability to release bis(4-aminophenyl) diselenide, the common fragment which can be ultimately responsible for the activity of the compounds. (b) the anti-parasitic activity achieved by the sulfonamide pharmacophore present in the analyzed derivatives. The data that support this connection include the topography of the molecules, the conformational behavior of the compounds, which influences the bond order, as well as the accessibility of the hydrolysis point, and possibly the hydrophobicity and polarizability of the compounds.

Kaurenoic Acid Possesses Leishmanicidal Activity by Triggering a NLRP12/IL-1β/cNOS/NO Pathway

Leishmania amazonensis (L. amazonensis) infection can cause severe local and diffuse injuries in humans, a condition clinically known as American cutaneous leishmaniasis (ACL). Currently, the therapeutic approach for ACL is based on Glucantime, which shows high toxicity and poor effectiveness. Therefore, ACL remains a neglected disease with limited options for treatment. Herein, the in vitro antiprotozoal effect and mechanisms of the diterpene kaurenoic acid [ent-kaur-16-en-19-oic acid] (KA) against L. amazonensis were investigated. KA exhibited a direct antileishmanial effect on L. amazonensis promastigotes. Importantly, KA also reduced the intracellular number of amastigote forms and percentage of infected peritoneal macrophages of BALB/c mice. Mechanistically, KA treatment reestablished the production of nitric oxide (NO) in a constitutive NO synthase- (cNOS-) dependent manner, subverting the NO-depleting escape mechanism of L. amazonensis. Furthermore, KA induced increased production of IL-1β and expression of the inflammasome-activating component NLRP12. These findings demonstrate the leishmanicidal capability of KA against L. amazonensis in macrophage culture by triggering a NLRP12/IL-1β/cNOS/NO mechanism.

Advances in Development of New Treatment for Leishmaniasis

Leishmaniasis is a neglected infectious disease caused by several different species of protozoan parasites of the genus Leishmania. Current strategies to control this disease are mainly based on chemotherapy. Despite being available for the last 70 years, leishmanial chemotherapy has lack of efficiency, since its route of administration is difficult and it can cause serious side effects, which results in the emergence of resistant cases. The medical-scientific community is facing difficulties to overcome these problems with new suitable and efficient drugs, as well as the identification of new drug targets. The availability of the complete genome sequence of Leishmania has given the scientific community the possibility of large-scale analysis, which may lead to better understanding of parasite biology and consequent identification of novel drug targets. In this review we focus on how high-throughput analysis is helping us and other groups to identify novel targets for chemotherapeutic interventions. We further discuss recent data produced by our group regarding the use of the high-throughput techniques and how this helped us to identify and assess the potential of new identified targets.

Effect of Apigenin on Leishmania amazonensis Is Associated with Reactive Oxygen Species Production Followed by Mitochondrial Dysfunction

Leishmaniasis is an important neglected disease caused by protozoa of the genus Leishmania that affects more than 12 million people worldwide. Leishmaniasis treatment requires the administration of toxic and poorly tolerated drugs, and parasite resistance greatly reduces the efficacy of conventional medications. Apigenin (1), a naturally occurring plant flavone, has a wide range of reported biological effects. In this study, antileishmanial activity of 1 in vitro was investigated, and its mechanism of action against Leishmania amazonensis promastigotes was described. Treatment with 1 for 24 h resulted in concentration-dependent inhibition of cellular proliferation (IC50 = 23.7 μM) and increased reactive oxygen species (ROS) generation. Glutathione and N-acetyl-l-cysteine protected L. amazonensis from the effects of 1 and reduced ROS levels after the treatment. By contrast, oxidized glutathione did not reduce the levels of ROS caused by 1 by not preventing the proliferation inhibition. Apigenin 1 also induced an extensive swelling in parasite mitochondria, leading to an alteration of the mitochondrial membrane potential, rupture of the trans-Golgi network, and cytoplasmic vacuolization. These results demonstrate the leishmanicidal effect of 1 and suggest the involvement of ROS leading to mitochondrial collapse as part of the mechanism of action.

Syzygium cumini (L.) Skeels essential oil and its major constituent α-pinene exhibit anti-Leishmania activity through immunomodulation in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

Syzygium cumini (L.) Skeels (Myrtaceae), commonly known as "jambolão" in Brazil is widely used in folk medicine against leishmaniasis, inflammation, chronic diarrhea, and ulcers. It is one of the most commonly used plants for the treatment of diabetes worldwide. In previous studies, Syzygium cumini was shown to possess antihyperlipidemic and anti-allergic properties, and to exhibit good performance as an antimicrobial agent against bacteria, fungi, and protozoa parasites of the genus Leishmania and Trypanosoma. This study was aimed at evaluating the effects of S. cumini essential oil (ScEO) and its major component α-pinene on Leishmania (Leishmania) amazonensis, as well as their cytotoxicity and possible mechanisms of action.

MATERIALS AND METHODS

To evaluate the anti-proliferative effect on Leishmania, effects on promastigote and axenic amastigote forms were assessed using tetrazolium salt (MTT) assay. The intramacrophagic amastigotes were exposed to ScEO and α-pinene to determine the survival index. To gain insight into the mechanism of action involved in the effect on the samples, we evaluated the modulation of macrophage activation state by observing structural (phagocytic and lysosomal activities) and cellular (nitric oxide increase) changes. To assess the safety profile of ScEO and α-pinene, murine macrophages and human red blood cells were treated with ScEO and α-pinene and the selectivity index was calculated for each treatment.

RESULTS

α-Pinene was effective against Leishmania amazonensis promastigote forms, with a half-maximal inhibitory concentration (IC50) value of 19.7µg/mL. α-Pinene was more active (IC50 values of 16.1 and 15.6µg/mL against axenic and intracellular amastigotes, respectively) than ScEO (IC50 values of 43.9 and 38.1µg/mL against axenic and intracellular amastigotes, respectively). Our results showed that the anti-Leishmania effects were mediated by immunomodulatory activity, as evidenced by the observed increases in both phagocytic and lysosomal activity, and the elevated NO levels. ScEO and α-pinene exhibited low cytotoxicity against murine macrophages and human erythrocytes. The 50% cytotoxicity concentration (CC50) values for the macrophages in the MTT assay were 614.1 and 425.2µg/mL for ScEO and α-pinene, respectively, while the corresponding half-maximal hemolytic concentration (HC50) values were 874.3 and 233.3µg/mL.

CONCLUSIONS

Taken together, the results demonstrate that ScEO and its major constituent α-pinene have significant anti-Leishmania activity, modulated by macrophage activation, with acceptable levels of cytotoxicity in murine macrophages and human erythrocytes. Further work is warranted, involving more in-depth mechanistic studies and in vivo investigations.

Th1-biased immunomodulation and therapeutic potential of Artemisia annua in murine visceral leishmaniasis

Background

In the absence of vaccines and limitations of currently available chemotherapy, development of safe and efficacious drugs is urgently needed for visceral leishmaniasis (VL) that is fatal, if left untreated. Earlier we reported in vitro apoptotic antileishmanial activity of n-hexane fractions of Artemisia annua leaves (AAL) and seeds (AAS) against Leishmania donovani. In the present study, we investigated the immunostimulatory and therapeutic efficacy of AAL and AAS.

Methodology/Principal Findings

Ten-weeks post infection, BALB/c mice were orally administered AAL and AAS for ten consecutive days. Significant reduction in hepatic (86.67% and 89.12%) and splenic (95.45% and 95.84%) parasite burden with decrease in spleen weight was observed. AAL and AAS treated mice induced the strongest DTH response, as well as three-fold decrease in IgG1 and two-fold increase in IgG2a levels, as compared to infected controls. Cytometric bead array further affirmed the elicitation of Th1 immune response as indicated by increased levels of IFN-γ, and low levels of Th2 cytokines (IL-4 and IL-10) in serum as well as in culture supernatant of lymphocytes from treated mice. Lymphoproliferative response, IFN-γ producing CD4⁺ and CD8⁺ T lymphocytes and nitrite levels were significantly enhanced upon antigen recall in vitro. The co-expression of CD80 and CD86 on macrophages was significantly augmented. CD8⁺ T cells exhibited CD62L^low and CD44^hi phenotype, signifying induction of immunological memory in AAL and AAS treated groups. Serum enzyme markers were in the normal range indicating inertness against nephro- and hepato-toxicity.

Conclusions/Significance

Our results establish the two-prong antileishmanial efficacy of AAL and AAS for cure against L. donovani that is dependent on both the direct leishmanicidal action as well as switching-on of Th1-biased protective cell-mediated immunity with generation of memory. AAL and AAS could represent adjunct therapies for the treatment of leishmaniasis, either alone or in combination with other antileishmanial agents.

Visceral leishmaniasis (VL) is a fatal, vector-borne tropical disease that affects the poorest sections of the society. The currently available drugs are toxic, expensive and have severe side effects. The problem is further compounded by emergence of VL-HIV co-infection and occurence of PKDL after apparent cure. Thus, alternate therapeutic interventions are needed in the absence of vaccines and mounting drug resistance. VL is also characterized by severe depression of cell-mediated immunity that complicates the efficiency of chemotherapeutic drugs. Restoration of the dampened immune system coupled with antileishmanial effect would be a rational approach in the quest for antileishmanial drugs. Plant derived secondary metabolites have been recommended for the containment of antiparasitic disease including leishmaniasis that synergistically aid in lifting the immune suppression. We previously reported in vitro antileishmanial activity of n-hexane fractions of Artemisia annua leaves (AAL) and seeds (AAS) that was mediated by apoptosis. In this study, we found significant reduction in liver and spleen parasite burden of Leishmania donovani infected BALB/c mice upon oral administration of AAL and AAS with concomitant immunostimulation and induction of immunological memory. The immunotherapeutic potentiation by AAL and AAS with no adverse toxic effects validates their use for treatment of this debilitating disease.

l-Asparaginase as a new molecular target against leishmaniasis: insights into the mechanism of action and structure-based inhibitor design

l-Asparaginases belong to a family of amidohydrolases that catalyze the conversion of l-asparagine into l-aspartic acid and ammonia.

Nitroimidazo-oxazole compound DNDI-VL-2098: an orally effective preclinical drug candidate for the treatment of visceral leishmaniasis

OBJECTIVES

The objective of this study was to identify a nitroimidazo-oxazole lead molecule for the treatment of visceral leishmaniasis (VL).

METHODS

A library of 72 nitroimidazo-oxazoles was evaluated in vitro for their antileishmanial activity against luciferase-transfected DD8 amastigotes of Leishmania donovani. On the basis of their in vitro potency and pharmacokinetic properties, the promising compounds were tested in acute BALB/c mouse and chronic hamster models of VL via oral administration and efficacy was evaluated by microscopic counting of amastigotes after Giemsa staining. The best antileishmanial candidates (racemate DNDI-VL-2001) and its R enantiomer (DNDI-VL-2098) were evaluated in vitro against a range of Leishmania strains. These candidates were further studied in a hamster model using various dose regimens. Cytokine and inducible nitric oxide synthase estimations by real-time PCR and nitric oxide generation by Griess assay were also carried out for DNDI-VL-2098.

RESULTS

In vitro screening of nitroimidazo-oxazole compounds identified the racemate DNDI-VL-2001 (6-nitroimidazo-oxazole derivative) and its enantiomers as candidates for further evaluation in in vivo models of VL. DNDI-VL-2098 (IC50 of 0.03 μM for the DD8 strain) showed excellent in vivo activity in both mouse and hamster models, with an ED90 value of 3.7 and <25 mg/kg, respectively, and was also found to be very effective against high-grade infection in the hamster model. Our studies revealed that, along with leishmanicidal activity, DNDI-VL-2098 was also capable of inducing host-protective immune cells to suppress Leishmania parasites in hamsters.

CONCLUSIONS

These studies led to the identification of compound DNDI-VL-2098 as a preclinical candidate for further drug development as an oral treatment for VL.

N-butyl-[1-(4-methoxy)phenyl-9H-β-carboline]-3-carboxamide prevents cytokinesis in Leishmania amazonensis

Leishmaniasis, a complex of diseases caused by protozoa of the genus Leishmania, is endemic in 98 countries, affecting approximately 12 million people worldwide. Current treatments for leishmaniasis have many disadvantages, such as toxicity, high costs, and prolonged treatment, making the development of new treatment alternatives highly relevant. Several studies have verified the antileishmanial activity of β-carboline compounds. In the present study, we investigated the in vitro antileishmanial activity of N-butyl-[1-(4-methoxy)phenyl-9H-β-carboline]-3-carboxamide (β-CB) against Leishmania amazonensis. The compound was active against promastigote, axenic amastigote, and intracellular amastigote forms of L. amazonensis, exhibiting high selectivity for the parasite. Moreover, β-CB did not exhibit hemolytic or mutagenic potential. Promastigotes treated with the alkaloid presented rounding of the body cell, cell membrane projections, an increase in the number of promastigotes presenting two flagella, and parasites of abnormal phenotype, with three or more flagella and/or nuclei. Furthermore, we observed an increase in the subpopulation of cells in the G2/M stage of the cell cycle. Altogether, these results suggest that β-CB likely prevents cytokinesis, although it does not interfere with the duplication of cell structures. We also verified an increase in O2(·-) production and the accumulation of lipid storage bodies. Cell membrane integrity was maintained, in addition to the absence of phosphatidylserine externalization, DNA fragmentation, and autophagosomes. Although the possibility of an apoptotic process cannot be discarded, β-CB likely exerts its antileishmanial activity through a cytostatic effect, thus preventing cellular proliferation.

Terpenes increase the lipid dynamics in the Leishmania plasma membrane at concentrations similar to their IC50 values

Although many terpenes have shown antitumor, antibacterial, antifungal, and antiparasitic activity, the mechanism of action is not well established. Electron paramagnetic resonance (EPR) spectroscopy of the spin-labeled 5-doxyl stearic acid revealed remarkable fluidity increases in the plasma membrane of terpene-treated Leishmania amazonensis promastigotes. For an antiproliferative activity assay using 5×10⁶ parasites/mL, the sesquiterpene nerolidol and the monoterpenes (+)-limonene, α-terpineol and 1,8-cineole inhibited the growth of the parasites with IC₅₀ values of 0.008, 0.549, 0.678 and 4.697 mM, respectively. The IC₅₀ values of these terpenes increased as the parasite concentration used in the cytotoxicity assay increased, and this behavior was examined using a theoretical treatment of the experimental data. Cytotoxicity tests with the same parasite concentration as in the EPR experiments revealed a correlation between the IC₅₀ values of the terpenes and the concentrations at which they altered the membrane fluidity. In addition, the terpenes induced small amounts of cell lysis (4–9%) at their respective IC₅₀ values. For assays with high cell concentrations (2×10⁹ parasites/mL), the incorporation of terpene into the cell membrane was very fast, and the IC₅₀ values observed for 24 h and 5 min-incubation periods were not significantly different. Taken together, these results suggest that terpene cytotoxicity is associated with the attack on the plasma membrane of the parasite. The in vitro cytotoxicity of nerolidol was similar to that of miltefosine, and nerolidol has high hydrophobicity; thus, nerolidol might be used in drug delivery systems, such as lipid nanoparticles to treat leishmaniasis.

Coating doxorubicin-loaded nanocapsules with alginate enhances therapeutic efficacy against Leishmania in hamsters by inducing Th1-type immune responses

BACKGROUND AND PURPOSE

The aim of the present study was to evaluate the immunomodulatory and chemotherapeutic potential of alginate-(SA) coated nanocapsule (NCs) loaded with doxorubicin (SA-NCs-DOX) against visceral leishmaniasis in comparison with nano-emulsions containing doxorubicin (NE-DOX).

EXPERIMENTAL APPROACH

NE-DOX was prepared using low-energy emulsification methods. Stepwise addition of protamine sulphate and SA in a layer-by-layer manner was used to form SA-NCs-DOX. SA-NCs-DOX, NE-DOX and Free DOX were compared for their cytotoxicity against Leishmania donovani-infected macrophages in vitro and generation of T-cell responses in infected hamsters in vivo.

KEY RESULTS

Size and ζ potential of the NE-DOX and SA-NCs-DOX formulations were 310 ± 2.1 nm and (-)32.6 ± 2.1 mV, 342 ± 4.1 nm and (-)29.3 ± 1.2 mV respectively. SA-NCs-DOX was better (1.5 times) taken up by J774A.1 macrophages compared with NE-DOX. SA-NCs -DOX showed greater efficacy than NE-DOX against intramacrophagic amastigotes. SA-NCs-DOX treatment exhibited enhanced apoptotic efficiency than NE-DOX and free DOX as evident by cell cycle analysis, decrease in mitochondrial membrane potential, ROS and NO production. T-cell responses, when assessed through lymphoproliferative responses, NO production along with enhanced levels of iNOS, TNF-α, IFN-γ and IL-12 were found to be up-regulated after SA-NCs-DOX, compared with responses to NE-DOX in vivo. Parasitic burden was decreased in Leishmania-infected hamsters treated with SA-NCs-DOX, compared with NE-DOX.

CONCLUSIONS AND IMPLICATIONS

Our results provide insights into the development of an alternative approach to improved management of leishmaniasis through a combination of chemotherapy with stimulation of the innate immune system.

Cell death in amastigote forms of Leishmania amazonensis induced by parthenolide

Background

Leishmania amazonensis infection results in diverse clinical manifestations: cutaneous, mucocutaneous or visceral leishmaniasis. The arsenal of drugs available for treating Leishmania infections is limited. Therefore, new, effective, and less toxic leishmaniasis treatments are still needed. We verified cell death in amastigote forms of Leishmania amazonensis induced by the sesquiterpene lactone parthenolide.

Results

The tested compound was able to concentration-dependently affect axenic and intracellular amastigotes, with IC₅₀ values of 1.3 μM and 2.9 μM, respectively after 72 h incubation. No genotoxic effects were observed in a micronucleus test in mice. Parthenolide induced morphological and ultrastructural changes in axenic amastigotes, including a loss of membrane integrity, swelling of the mitochondrion, cytoplasmic vacuoles, and intense exocytic activity in the region of the flagellar pocket. These results led us to investigate the occurrence of autophagic vacuoles with monodansylcadaverine and the integrity of the plasma membrane and mitochondrial membrane potential using flow cytometry. In all of the tests, parthenolide had positive results.

Conclusions

Our results indicate that the antileishmanial action of parthenolide is associated with autophagic vacuole appearance, a reduction of fluidity, a loss of membrane integrity, and mitochondrial dysfunction. Considering the limited repertoire of existing antileishmanial compounds, the products derived from medicinal plants has been one the greatest advances to help develop new chemotherapeutic approaches.

Combination of liposomal CpG oligodeoxynucleotide 2006 and miltefosine induces strong cell-mediated immunity during experimental visceral leishmaniasis

Immuno-modulators in combination with antileishmanial drug miltefosine is a better therapeutic approach for treatment of Visceral Leishmaniasis (VL) as it not only reduces the dose of miltefosine but also shortens the treatment regimen. However, immunological mechanisms behind the perceived benefits of this combination therapy have not been investigated in detail. In the present study, we hypothesized that potential use of drugs that target the host in addition to the parasite might represent an alternative strategy for combination therapy. We investigated immune responses generated in Leishmania donovani infected animals (hamsters and mice) treated with combination of CpG-ODN-2006 and miltefosine at short dose regimen. Infected animals were administered CpG-ODN-2006 (0.4 mg/kg, single dose), as free and liposomal form, either alone or in combination with miltefosine for 5 consecutive days and parasite clearance was evaluated at day 4 and 7 post treatment. Animals that received liposomal CpG-ODN-2006 (lipo-CpG-ODN-2006) and sub-curative miltefosine (5 mg/kg) showed the best inhibition of parasite multiplication (∼97%) which was associated with a biased Th1 immune response in. Moreover, compared to all the other treated groups, we observed increased mRNA expression levels of pro-inflammatory cytokines (IFN-γ, TNF-α and IL-12) and significantly suppressed levels of Th2 cytokines (IL-10 and TGF-β) on day 4 post treatment in animals that underwent combination therapy with lipo-CpG-ODN-2006 and sub-curative miltefosine. Additionally, same therapy also induced heightened iNOS mRNA levels and NO generation, increased IgG2 antibody level and strong T-cell response in these hamsters compared with all the other treated groups. Collectively, our results suggest that combination of lipo-CpG-ODN-2006 and sub-curative miltefosine generates protective T-cell response in an animal model of visceral leishmaniasis which is characterized by strong Th1 biased immune response thereby underlining our hypothesis that combination therapy, at short dose regimen can be used as a novel way of treating visceral leishmaniasis.

Activity of anti-cancer protein kinase inhibitors against Leishmania spp

OBJECTIVES

There is an urgent need to develop new and effective treatments for poverty-related neglected diseases. In light of the time required to bring a new drug to market and the cost involved (10-15 years, >1 billion US$), one approach to identifying new treatments for diseases like leishmaniasis is to evaluate drugs that are already registered for the treatment of other diseases. This paper describes the anti-leishmanial activities of 10 FDA-approved protein kinase inhibitors already available for the treatment of human cancers.

METHODS

In vitro and in vivo models of Leishmania infection were used to evaluate the potency of selected protein kinase inhibitors.

RESULTS

Sunitinib, sorafenib and lapatinib were identified as active against Leishmania donovani amastigotes in cultured murine macrophages with IC(50) values of 1.1, 3.7 and 2.5 μM, respectively, a level of potency similar to that of miltefosine (IC(50) = 1.0 μM), and were not toxic to mammalian cells. In addition, some of the protein kinase inhibitors were active against L. donovani in the BALB/c mouse model of infection; dosing on days 7-11 with a 50 mg/kg oral dose of sunitinib, lapatinib or sorafenib reduced liver amastigote burdens by 41%, 36% and 30%, respectively, compared with untreated control mice. Although less efficacious, sorafenib was also active in vitro against intracellular amastigotes of the cutaneous disease-causing species Leishmania amazonensis, Leishmania major and Leishmania mexicana.

CONCLUSIONS

This study demonstrates in vivo anti-leishmanial activity of clinically used protein kinase inhibitors and provides further evidence of the potential of drug repurposing.

In SilicoStudy ofLeishmania donovaniα-βTubulin and Inhibitors

Leishmania donovaniis a parasite that causes visceral leishmaniasis, a severe form of leishmaniasis that affects vital organs. An important target for the treatment of this disease is the proteinα-βtubulin, which was modeled in this paper and proposed as a target for the treatment of visceral leishmaniasis. Two classes of compounds were studied, dinitroanilines and oxadiazoles. According to the docking results, dinitroanilines interact better with the L loop domain and oxadiazoles interact better with the colchicine domain.

Five-year retrospective Italian multicenter study of visceral leishmaniasis treatment

The treatment of visceral leishmaniasis (VL) is poorly standardized in Italy in spite of the existing evidence. All consecutive patients with VL admitted at 15 Italian centers as inpatients or outpatients between January 2004 and December 2008 were retrospectively considered; outcome data at 1 year after treatment were obtained for all but 1 patient. Demographic characteristics, underlying diseases, diagnostic procedures, treatment regimens and outcomes, as well as side effects were recorded. A confirmed diagnosis of VL was reported for 166 patients: 120 (72.3%) immunocompetent, 21 (12.6%) patients with immune deficiencies other than HIV infection, and 25 (15.1%) coinfected with HIV. Liposomal amphotericin B (L-AmB) was the drug almost universally used for treatment, administered to 153 (92.2%) patients. Thirty-seven different regimens, including L-AmB were used. The mean doses were 29.4 ± 7.9 mg/kg in immunocompetent patients, 32.9 ± 8.6 mg/kg in patients with non-HIV-related immunodeficiencies, and 40.8 ± 6.7 mg/kg in HIV-infected patients (P < 0.001). The mean numbers of infusion days were 7.8 ± 3.1 in immunocompetent patients, 9.6 ± 3.9 in non-HIV-immunodeficient patients, and 12.0 ± 3.4 in HIV-infected patients (P < 0.001). Mild and reversible adverse events were observed in 12.2% of cases. Responsive patients were 154 (93.3%). Successes were 98.4% among immunocompetent patients, 90.5% among non-HIV-immunodeficient patients, and 72.0% among HIV-infected patients. Among predictors of primary response to treatment, HIV infection and age held independent associations in the final multivariate models, whereas the doses and duration of L-AmB treatment were not significantly associated. Longer treatments and higher doses of L-AmB were not able to significantly modify treatment outcomes either in the immunocompetent or in the immunocompromised population.

Antileishmanial activity of diterpene acids in copaiba oil

Leishmaniasis is a neglected tropical disease. According to the World Health Organization, there are approximately 1.5-two million new cases of cutaneous leishmaniasis each year worldwide. Chemotherapy against leishmaniasis is based on pentavalent antimonials, which were developed more than a century ago. The goals of this study were to investigate the antileishmanial activity of diterpene acids in copaiba oil, as well as some possible targets of their action against Leishmania amazonensis. Methyl copalate and agathic, hydroxycopalic, kaurenoic, pinifolic and polyaltic acids isolated from Copaifera officinales oleoresins were utilised. Ultrastructural changes and the specific organelle targets of diterpenes were investigated with electron microscopy and flow cytometry, respectively. All compounds had some level of activity against L. amazonensis. Hydroxycopalic acid and methyl copalate demonstrated the most activity against promastigotes and had 50% inhibitory concentration (IC50) values of 2.5 and 6.0 µg/mL, respectively. However, pinifolic and kaurenoic acid demonstrated the most activity against axenic amastigote and had IC50 values of 3.5 and 4.0 µg/mL, respectively. Agathic, kaurenoic and pinifolic acid caused significant increases in plasma membrane permeability and mitochondrial membrane depolarisation of the protozoan. In conclusion, copaiba oil and its diterpene acids should be explored for the development of new antileishmanial drugs.

Developments in diagnosis and treatment of visceral leishmaniasis during the last decade and future prospects

Human visceral leishmaniasis (VL) continues to be a life-threatening neglected tropical disease, with close to 200 million people at risk of infection globally. Epidemics and resurgence of VL are associated with negligence by the policy makers, economic decline and population movements. Control of the disease is hampered by the lack of proficient vaccination, rapid diagnosis in a field setting and severe side effects of current drug therapies. The diagnosis of VL relied largely on invasive techniques of detecting parasites in splenic and bone marrow aspirates. rK39 and PCR, despite problems related to varying sensitivities and specificities and field adaptability, respectively, are considered the best options for VL diagnosis today. No single therapy of VL currently offers satisfactory efficacy along with safety. The field of VL research only recently shifted toward actively identifying new drugs for safe and affordable treatment. Oral miltefosine and safe AmBisome along with better use of amphotericin B have been rapidly implemented in the last decade. A combination therapy will substantially reduce the required dose and duration of drug administration and reduce the chance of the development of resistance. In addition, identification of asymptomatic cases, vector control and treatment of post-kala-azar dermal leishmaniasis would allow new perspectives in VL control and management.

Interactions of antiparasitic alkaloids with Leishmania protein targets: a molecular docking analysis

Background: Leishmaniasis is a collection of chronic diseases caused by protozoa of the genus Leishmania. Current antileishmanial chemotherapeutics have demonstrated adverse side effects and therefore R&D into new safer alternative treatments are needed. Methods: A molecular docking analysis has been carried out to assess possible Leishmania biochemical targets of antiparasitic alkaloids. A total of 209 antiparasitic alkaloids were docked with 24 Leishmania protein targets. Results: The strongest docking alkaloid ligands were flinderoles A and B and juliflorine with Leishmania major methionyl-tRNA synthetase; juliflorine, juliprosine, prosopilosidine and prosopilosine with Leishmania mexicana glycerol-3-phosphate dehydrogenase; and ancistrogriffithine A with L. major N-myristoyl transferase. Conclusion: This molecular docking study has provided evidence for what classes and structural types of alkaloids may be targeting specific Leishmania protein targets.

Lingual Leishmaniasis Presenting to Maxillofacial Surgery in UK with Successful Treatment with Miltefosine

Leishmaniasis is a disease that is caused by protozoa of the genus Leishmania, which is prevalent in tropical and subtropical areas. Clinical forms of leishmaniasis are particularly diverse representing a complex of diseases. We present a case of lingual Leishmaniasis in an immunocompetent man. The lesions were caused by Leishmania donovani/infantum species. The patient responded excellently to miltefosine treatment, with no reactivation during followup. To the authors' knowledge, it is the first such case of successful miltefosine treatment in this unusual variant of leishmaniasis occurring on the tongue.

Identification and characterization of the regions involved in the nuclear translocation of the heterodimeric leishmanial DNA topoisomerase IB

Leishmania donovani, the causative organism for visceral leishmaniasis, contains a unique heterodimeric DNA-topoisomerase IB (LdTopIB). LdTopIB is a heterodimer made up of a large subunit and a small subunit that must interact with each other to build an active enzyme able to solve the topological tensions on the DNA. As LdTopIB is located within the nucleus, one or more nuclear localization signals (NLS) should exist to ensure its nuclear translocation. In this report three novel NLS have been identified through a sequential deletion study of the genes encoding of both subunits fused to that encoding the green fluorescent protein (GFP). NLS1 is a highly basic sequence of 43 amino acids in the C-terminal extension of the large protomer. We found two well-defined sequences in the small protomer: NLS2 is a 10-amino acid motif located in the N-terminal extension of the protein; NLS3 consists of a complex region of 28 amino acids placed in the vicinity of the catalytic Tyr-222 included at the conserved SKINY signature within the C-terminal. Furthermore, by means of yeast cell viability assays, conducted with several LdTopIB chimeras lacking any of the NLS motives, we have revealed that both subunits are transported independently to the nucleus. There was no evidence of LdTopIB accumulation in mitochondria or association to the kinetoplast DNA network. The results rule out the former hypothesis, which attributes nucleocytoplasmic transport of LdTopIB entirely to the large subunit. The LdTopIB is localized to the nucleus only.

Strategies for the design of orally bioavailable antileishmanial treatments

Leishmaniasis is one of the six major tropical diseases targeted by the World Health Organization. The most serious, life-threatening form is visceral leishmaniasis (VL). No vaccine is yet available for human use and chemotherapy is the main mean of dealing with this disease. This review focuses on the development of drug delivery systems (DDS) for treatment of leishmaniasis. After an overview of the significance of leishmaniasis in 2013, current chemotherapy and its limitations are considered, leading to possible strategies to improve the treatment of VL: new drugs, combinations of existing drugs and DDS, particularly for oral administration. Nanostructured biomaterials such as lipid-based or polymeric nanoparticles have unique physicochemical properties, ultra-small and controllable size, large surface area to mass ratio and the possibility of surface modification which can be used to advantage for the oral administration of antileishmanial drugs. They can improve the rate of dissolution of poorly water-soluble drugs, increase intestinal residence time by bioadhesion and, especially when lipid additives are used, influence the route and efficiency of absorption. These recent advances in this very active field should lead to better management of this serious disease.