Chemotherapy in the treatment and control of leishmaniasis

Neglected tropical diseases: survey and geometry of randomised evidence

OBJECTIVE

To assess the quantity and distribution of evidence from randomised controlled trials for the treatment of the major neglected tropical diseases and to identify gaps in the evidence with network analysis.

DESIGN

Systematic review and network analysis.

DATA SOURCES

Cochrane Central Register of Controlled Trials and PubMed from inception to 31 August 2011.

STUDY SELECTION

Randomised controlled trials that examined treatment of 16 neglected tropical diseases or complications thereof published in English, French, Spanish, Portuguese, German, or Dutch.

RESULTS

We identified 971 eligible randomised trials. Leishmaniasis (184 trials, 23,039 participants) and geohelminth infections; 160 trials, 46,887 participants) were the most studied, while dracunculiasis (nine trials, 798 participants) and Buruli ulcer (five trials, 337 participants) were least studied. Relative to its global burden of disease, lymphatic filariasis had the fewest trials and participants. Only 11% of trials were industry funded. Either a single trial or trials with fewer than 100 participants comprised the randomised evidence for first or second line treatments for Buruli ulcer, human African trypanosomiasis, American trypanosomiasis, cysticercosis, rabies, echinococcosis, New World cutaneous leishmaniasis, and each of the foodborne trematode infections. Among the 10 disease categories with more than 40 trials, five lacked sufficient head to head comparisons between first or second line treatments.

CONCLUSIONS

There is considerable variation in the amount of evidence from randomised controlled trials for each of the 16 major neglected tropical diseases. Even in diseases with substantial evidence, such as leishmaniasis and geohelminth infections, some recommended treatments have limited supporting data and lack head to head comparisons.

In vitro phototoxicity of ultradeformable liposomes containing chloroaluminum phthalocyanine against New World Leishmania species

The use of photodynamic therapy (PDT) against cutaneous leishmaniasis (CL) based on chloroaluminum phthalocyanine (ClAlPc) is a promissory alternative therapy. The main purpose of this article was to assess the internalization and in vitro phototoxic activities of ClAlPc encapsulated in ultradeformable liposomes (UDL-ClAlPc) in Leishmania parasites and mammalian cells. Cell internalization was determined by fluorescence microscopy, cell and parasite damage by standard MTT or direct microscopic analysis and a phototoxic index (PI) was calculated as the compound activity (IC(50)) at 0 J/cm(2)/IC(50) at 17 J/cm(2). Liposomal and free ClAlPc were internalized by infected and non-infected THP-1 cells and co-localized in the mitochondria. Treatment of UDL-ClAlPc was almost 10 times more photoactive than free ClAlPc on THP-1 cells and promastigotes and intracellular amastigotes of Leishmania chagasi and Leishmania panamensis. Liposomal compounds were active on non-irradiated and irradiated cells however PI higher than 50 were calculated. PI for amphotericin B referential drug were lower than 1.2. Empty liposomes tested at the same lipid concentration of active ClPcAl-liposomes were non-toxic. Upon photodynamic treatment a nonselective-parasite activity against intracellular amastigotes were observed and loss of membrane integrity resulting in a release of parasites was detected. Further studies oriented to evaluate both the state of infection after PDT and the effectiveness of UDL as delivery vehicles of ClAlPc in CL experimental models are required.

Review of the current treatments for leishmaniases

Leishmaniases are vector-borne zoonotic diseases that are prevalent in tropical and subtropical areas in the world, with two million new cases occurring yearly. Visceral and tegumentary forms of leishmaniasis are known. The latter form may present as localized cutaneous or mucosal forms, disseminated, diffuse forms, or leishmaniasis recidiva cutis. Visceral leishmaniasis is caused by parasites of the species Leishmania (Leishmania) donovani and L. (L.) infantum, and tegumentary leishmaniasis is caused by 15 other species, with distinct distributions in the Old and New World. The varied clinical manifestations, the multitude of Leishmania species, and the increasing incidence of HIV coinfection make the diagnosis and treatment of leishmaniases complex. Since there are no solid data relating clinical manifestations, treatment outcomes and Leishmania species the decision regarding the best therapeutic option is almost entirely based on clinical manifestations. Because most of the literature is focused on leishmaniasis in the Old World, in this review we present data on the treatment of New World leishmaniasis in more detail. Ranked therapeutic options, clinical trials, and also observations, even with a restricted number of subjects, on treatment outcome of visceral and different forms of tegumentary leishmaniasis, are presented. Treatment for leishmaniasis in HIV-coinfected patients is addressed as well. Some of these data strongly suggest that the differences in the outcome of the treatment are related to the Leishmania species. Therefore, although it is not possible at most points of care to identify the species causing the infection - a process that requires a well equipped laboratory - the infecting species should be identified whenever possible. More recent approaches, such as the use of immunomodulators and immunotherapy, and the lines for development of new candidate drugs are mentioned.

An image-based high-content screening assay for compounds targeting intracellular Leishmania donovani amastigotes in human macrophages

Leishmaniasis is a tropical disease threatening 350 million people from endemic regions. The available drugs for treatment are inadequate, with limitations such as serious side effects, parasite resistance or high cost. Driven by this need for new drugs, we developed a high-content, high-throughput image-based screening assay targeting the intracellular amastigote stage of different species of Leishmania in infected human macrophages. The in vitro infection protocol was adapted to a 384-well-plate format, enabling acquisition of a large amount of readouts by automated confocal microscopy. The reading method was based on DNA staining and required the development of a customized algorithm to analyze the images, which enabled the use of non-modified parasites. The automated analysis generated parameters used to quantify compound activity, including infection ratio as well as the number of intracellular amastigote parasites and yielded cytotoxicity information based on the number of host cells. Comparison of this assay with one that used the promastigote form to screen 26,500 compounds showed that 50% of the hits selected against the intracellular amastigote were not selected in the promastigote screening. These data corroborate the idea that the intracellular amastigote form of the parasite is the most appropriate to be used in primary screening assay for Leishmania.

Molecular mechanisms of drug resistance in natural Leishmania populations vary with genetic background

The evolution of drug-resistance in pathogens is a major global health threat. Elucidating the molecular basis of pathogen drug-resistance has been the focus of many studies but rarely is it known whether a drug-resistance mechanism identified is universal for the studied pathogen; it has seldom been clarified whether drug-resistance mechanisms vary with the pathogen's genotype. Nevertheless this is of critical importance in gaining an understanding of the complexity of this global threat and in underpinning epidemiological surveillance of pathogen drug resistance in the field. This study aimed to assess the molecular and phenotypic heterogeneity that emerges in natural parasite populations under drug treatment pressure. We studied lines of the protozoan parasite Leishmania (L.) donovani with differential susceptibility to antimonial drugs; the lines being derived from clinical isolates belonging to two distinct genetic populations that circulate in the leishmaniasis endemic region of Nepal. Parasite pathways known to be affected by antimonial drugs were characterised on five experimental levels in the lines of the two populations. Characterisation of DNA sequence, gene expression, protein expression and thiol levels revealed a number of molecular features that mark antimonial-resistant parasites in only one of the two populations studied. A final series of in vitro stress phenotyping experiments confirmed this heterogeneity amongst drug-resistant parasites from the two populations. These data provide evidence that the molecular changes associated with antimonial-resistance in natural Leishmania populations depend on the genetic background of the Leishmania population, which has resulted in a divergent set of resistance markers in the Leishmania populations. This heterogeneity of parasite adaptations provides severe challenges for the control of drug resistance in the field and the design of molecular surveillance tools for widespread applicability.

Drug resistance is a serious problem that strikes at the core of infectious disease control. The mechanisms developed by pathogens to become resistant against existing drug treatments have been studied for many years but these studies have frequently scrutinized a few lines of the pathogen and rarely is it known whether the mechanisms identified occur in all pathogen populations present in endemic regions. In this study we assessed the diversity amongst drug-resistant parasites which emerged under treatment pressure in a natural parasite population. An extensive molecular and phenotypic characterisation of a collection of Leishmania donovani parasites isolated from leishmaniasis patients revealed that the parasites which are resistant to treatment have heterogeneous characters. The results provide evidence that how a parasite develops resistance under treatment pressure depends upon its genetic background. These findings provide key insights into the challenge that drug resistance poses for the control of infectious diseases like leishmaniasis.

Visceral leishmaniasis treatment: What do we have, what do we need and how to deliver it?

Leishmaniasis is one of the most neglected tropical disease in terms of drug discovery and development. Most antileishmanial drugs are highly toxic, present resistance issues or require hospitalization, being therefore not adequate to the field. Recently improvements have been achieved by combination therapy, reducing the time and cost of treatment. Nonetheless, new drugs are still urgently needed. In this review, we describe the current visceral leishmaniasis (VL) treatments and their limitations. We also discuss the new strategies in the drug discovery field including the development and implementation of high-throughput screening (HTS) assays and the joint efforts of international teams to deliver clinical candidates.

Leishmaniasis chemotherapy--challenges and opportunities

Although there have been significant advances in the treatment of visceral leishmaniasis (VL), there remain challenges to ensure that treatments effective in India are also effective in other regions of the world and to identify treatment for post kala-azar dermal leishmaniasis as well as the opportunity to develop a safe oral short-course treatment. At the same time, there have been few advances for the treatment of simple or complex forms of cutaneous leishmaniasis (CL), other than topical paromomycin formulations. The main challenge for CL is to ensure that this disease is on the research and development agenda, so that new drugs are evaluated or compounds are screened in appropriate models, and that the standardization of quality of clinical trials is guaranteed. Problems also remain in the treatment of HIV/leishmaniasis co-infected patients. We are some way from having the ideal treatments for VL and CL and drug research and development for these diseases must remain focused.

Clinical pleiomorphism in human leishmaniases, with special mention of asymptomatic infection

This review gives an update of current knowledge on the clinical pleiomorphism of Leishmania, with a special emphasis on the case of asymptomatic carriage. The first part describes the numerous unusual expressions of the disease that occur besides the classic (visceral, cutaneous, and mucocutaneous) forms of leishmaniases. The second part deals with progress in the understanding of disease outcome in humans, and the possible future approaches to improve our knowledge in the field. The third part highlights the role of the too often neglected asymptomatic carrier compartment. This group could be key to understanding infraspecific differences in virulence and pathogenicity of the parasite, as well as identifying the genetic determinants involved in the expression of the disease.

Management of trypanosomiasis and leishmaniasis

BACKGROUND

The current treatments for human African trypanosomiasis (HAT), Chagas disease and leishmaniasis (collectively referred to as the kinetoplastid diseases) are far from ideal but, for some, there has been significant recent progress. For HAT the only advances in treatment over the past two decades have been the introduction of an eflornithine/nifurtimox co-administration and a shorter regime of the old standard melarsoprol.

SOURCES OF DATA

PubMed.

AREAS OF AGREEMENT

There is a need for new safe, oral drugs for cost-effective treatment of patients and use in control programmes for all the trypanosomatid diseases.

AREAS OF CONTROVERSY

Cutaneous leishmaniasis is not on the agenda and treatments are lagging behind.

GROWING POINTS

There are three compounds in development for the treatment of the CNS stage of HAT: fexinidazole, currently due to entry into phase II clinical studies, a benzoxaborole (SCYX-7158) in phase I trials and a diamidine derivative (CPD-0802), in advanced pre-clinical development. For Chagas disease, two anti-fungal triazoles are now in clinical trial. In addition, clinical studies with benznidazole, a drug previously recommended only for acute stage treatment, are close to completion to determine the effectiveness in the treatment of early chronic and indeterminate Chagas disease. For visceral leishmaniasis new formulations, therapeutic switching, in particular AmBisome, and the potential for combinations of established drugs have significantly improved the opportunities for the treatment in the Indian subcontinent, but not in East Africa.

AREAS TIMELY FOR DEVELOPING RESEARCH

Improved diagnostic tools are needed to support treatment, for test of cure in clinical trials and for monitoring/surveillance of populations in control programmes.

Potential utility of hyperbaric oxygen therapy and propolis in enhancing the leishmanicidal activity of glucantime

In this study we investigated the efficacy of hyperbaric oxygen (HBO) therapy, alone or combined with the pentavalent antimonial glucantime on Leishmania amazonensis infection. In parallel, the effect of Brazilian red propolis gel (propain) alone or combined with glucantime on L. amazonensis infection was evaluated. The inhibition of the infection in macrophages treated with glucantime in combination with HBO exposition was greater than that of macrophages treated with glucantime alone or HBO alone. The susceptible mouse strain BALB/c infected in the shaved rump with L. amazonensis treated with glucantime and exposed to HBO showed: time points in the course of the disease in which lesions were smaller than those of mice treated with glucantime alone and revascularization of the skin in the lesion site; interferon-gamma (IFN-g) levels were not elevated in lymph node cells from these animals. Propain alone was not efficient against lesions, although less exudative lesions were observed in animals treated with propain alone or combined with glucantime. These results reveal the potential value of HBO and red propolis in combination with glucantime for treating cutaneous leishmaniasis and encourage further studies on the effect of more aggressive HBO, propolis and glucantime therapies on different mouse models of leishmaniasis.

Uptake of the antileishmania drug tafenoquine follows a sterol-dependent diffusion process in Leishmania

OBJECTIVES

The present study was designed to elucidate the mechanism of tafenoquine uptake in Leishmania and its sterol dependence.

METHODS

Because tafenoquine is a fluorescent compound, spectrofluorimetric analysis allowed us to monitor its uptake by Leishmania promastigotes and intracellular amastigotes, and to evaluate the effect of temperature, energy and H+ gradient on drug entry. The influence of sterols on tafenoquine uptake in Leishmania parasites was determined in experiments using sterol-depleting agents such as methyl-β-cyclodextrin or cholesterol oxidase.

RESULTS

Tafenoquine exhibited fast entry kinetics into Leishmania in an energy-independent, but pH- and temperature-dependent, non-saturable process. Furthermore, sterol depletion decreased tafenoquine uptake.

CONCLUSIONS

These findings suggest that Leishmania takes up tafenoquine by a diffusion process and that decreases in membrane sterol content may induce a decrease in drug uptake.

Who is a typical patient with visceral leishmaniasis? Characterizing the demographic and nutritional profile of patients in Brazil, East Africa, and South Asia

Drug-dosing recommendations for visceral leishmaniasis (VL) treatment are based on the patients' weight or age. A current lack of demographic and anthropometric data on patients hinders (1) the ability of health providers to properly prepare for patient management, (2) an informed drug procurement for disease control, and (3) the design of clinical trials and development of new drug therapies in the different endemic areas. We present information about the age, gender, weight, and height of 29,570 consecutive VL patients presenting to 20 locations in six geographic endemic regions of Brazil, East Africa, Nepal, and India between 1997 and 2009. Our compilation shows substantial heterogeneity in the types of patients seeking care for VL at the clinics within the different locations. This suggests that drug development, procurement, and perhaps even treatment protocols, such as the use of the potentially teratogenic drug miltefosine, may require distinct strategies in these geographic settings.

Intracellular targeting specificity of novel phthalocyanines assessed in a host-parasite model for developing potential photodynamic medicine

Photodynamic therapy, unlikely to elicit drug-resistance, deserves attention as a strategy to counter this outstanding problem common to the chemotherapy of all diseases. Previously, we have broadened the applicability of this modality to photodynamic vaccination by exploiting the unusual properties of the trypanosomatid protozoa, Leishmania, i.e., their innate ability of homing to the phagolysosomes of the antigen-presenting cells and their selective photolysis therein, using transgenic mutants endogenously inducible for porphyrin accumulation. Here, we extended the utility of this host-parasite model for in vitro photodynamic therapy and vaccination by exploring exogenously supplied photosensitizers. Seventeen novel phthalocyanines (Pcs) were screened in vitro for their photolytic activity against cultured Leishmania. Pcs rendered cationic and soluble (csPcs) for cellular uptake were phototoxic to both parasite and host cells, i.e., macrophages and dendritic cells. The csPcs that targeted to mitochondria were more photolytic than those restricted to the endocytic compartments. Treatment of infected cells with endocytic csPcs resulted in their accumulation in Leishmania-containing phagolysosomes, indicative of reaching their target for photodynamic therapy, although their parasite versus host specificity is limited to a narrow range of csPc concentrations. In contrast, Leishmania pre-loaded with csPc were selectively photolyzed intracellularly, leaving host cells viable. Pre-illumination of such csPc-loaded Leishmania did not hinder their infectivity, but ensured their intracellular lysis. Ovalbumin (OVA) so delivered by photo-inactivated OVA transfectants to mouse macrophages and dendritic cells were co-presented with MHC Class I molecules by these antigen presenting cells to activate OVA epitope-specific CD8+T cells. The in vitro evidence presented here demonstrates for the first time not only the potential of endocytic csPcs for effective photodynamic therapy against Leishmania but also their utility in photo-inactivation of Leishmania to produce a safe carrier to express and deliver a defined antigen with enhanced cell-mediated immunity.

Study of parasite kinetics with antileishmanial drugs using real-time quantitative PCR in Indian visceral leishmaniasis

OBJECTIVES

This study describes parasite kinetics in the blood of visceral leishmaniasis patients treated with liposomal amphotericin B (L-AmB) or a preformed fat emulsion of amphotericin B (ApL) using real-time quantitative PCR (qPCR).

METHODS

Forty-six patients were treated with a single dose (15 mg/kg of body weight) of either L-AmB (n = 13) or ApL (n = 33). qPCR was used to estimate parasite kinetics by detection of Leishmania donovani DNA using kinetoplast DNA-specific primers in peripheral blood samples using an absolute quantification method.

RESULTS

The mean parasite load decreased from baseline (day 0) values of 894.07 and 980.48 to 71.72 and 211.52 parasite genomes/mL at day 7 in L-AmB and ApL groups, respectively, and at day 30 these further declined to 8.30 and 133.98 parasite genomes/mL, respectively. At day 30 post-treatment evaluation, the decline in parasite load was significantly greater (P = 0.024) with L-AmB compared with ApL. Four of 33 patients in the ApL group failed treatment (1 primary failure and 3 relapses) with the presence of parasites, whereas all patients in the L-AmB group were cured at 6 month follow-up.

CONCLUSIONS

qPCR can be a tool to measure parasite dynamics accurately and provide a marker to measure the efficacy of various drugs. It can be used as a test of cure, allowing us to do away with invasive and risky methods such as splenic or bone marrow aspiration.

Direct diagnosis of Leishmania species on serosity materials punctured from cutaneous leishmaniasis patients using PCR-RFLP

This study was aimed at identifying the Leishmania species using serosity materials punctured from skin lesions of cutaneous leishmaniasis (CL) patients by using internal transcribed spacer1 (ITS1) polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP). We used the PCR-RFLP on 60 parasitological confirmed CL patients who referred to leishmaniasis laboratory from the School of Public Health, Tehran University of Medical Sciences. The PCR-RFLP could correctly detect 51 Leishmania species of the 60 confirmed positive specimens, where all the other 10 parasitological (microscopy and culture) negative samples that were prepared from other bacterial- and fungal-infected lesions had negative results. The results also revealed that Leishmania major was the dominant species (53.3%). This study suggests that the PCR-RFLP assay with serosity materials punctured from CL patients using Hae III enzyme is useful for the rapid identification of Leishmania species.

Drug combinations for visceral leishmaniasis

PURPOSE OF REVIEW

Several attempts have been made to combine drugs for treating visceral leishmaniasis, but only recently have effective drugs become available and combinations been tested systematically.

RECENT FINDINGS

Sequential treatments with liposomal amphotericin B followed by miltefosine or paromomycin (as short as 7 days), as well as the concomitant administration of miltefosine and paromomycin (for 10 days) are very effective in India (>95%). Sodium stibogluconate plus paromomycin for 17 days is more than 90% effective in East Africa. The shortened combination regimens are cost-effective in India. No combination has been tested so far in Brazil, Nepal and Bangladesh, although studies may be expected in the near future. No cost-effectiveness analysis has been done as yet outside India.

SUMMARY

There is evidence of high efficacy and benefits with sequential and co-administration treatments in India. More studies are needed in other endemic areas. Introducing combinations and scaling up their use will be challenging. Experience acquired with malaria may be useful. Proper monitoring of use and effects (efficacy and safety) will be required. Currently there are no options for fixed-dose combination treatments for leishmaniasis.

Renal involvement in leishmaniasis: a review of the literature

Leishmaniasis, an infectious disease endemic in tropical, Asian and southern European countries, is caused by obligate intramacrophage protozoa and is transmitted through the bite of infected female sandflies. More than 20 leishmanial species are responsible for four main clinical syndromes: cutaneous leishmaniasis; mucocutaneous leishmaniasis; visceral leishmaniasis, also known as kala-azar, and post-kala-azar dermal leishmaniasis. Visceral leishmaniasis can present with varying clinical features and the kidney can also be involved. Both glomerular and tubular function can be altered and patients can develop proteinuria, haematuria, abnormalities in urinary concentration and acidification and acute and chronic renal insufficiency. Not only the disease itself but also the therapy administered might be responsible for the renal involvement in kala-azar. Indeed, some of the agents with efficiency against visceral leishmaniasis, such as pentavalent antimonial drugs, amphotericin B, pentamidine, miltefosine, paromomycin and simataquine, may be associated with a high risk of renal toxicity. In this article, the literature on renal involvement in visceral leishmaniasis is reviewed.

Structures, targets and recent approaches in anti-leishmanial drug discovery and development

Recent years have seen a significant improvement in available treatment options for leishmaniasis. Two new drugs, miltefosine and paromomycin, have been registered for the treatment of visceral leishmaniasis (VL) in India since 2002. Combination therapy is now explored in clinical trials as a new treatment approach for VL to reduce the length of treatment and potentially prevent selection of resistant parasites. However there is still a need for new drugs due to safety, resistance, stability and cost issues with existing therapies. The search for topical treatments for cutaneous leishmaniasis (CL) is ongoing. This review gives a brief overview of recent developments and approaches in anti-leishmanial drug discovery and development.

Metabolomics to unveil and understand phenotypic diversity between pathogen populations

Leishmaniasis is a debilitating disease caused by the parasite Leishmania. There is extensive clinical polymorphism, including variable responsiveness to treatment. We study Leishmania donovani parasites isolated from visceral leishmaniasis patients in Nepal that responded differently to antimonial treatment due to differing intrinsic drug sensitivity of the parasites. Here, we present a proof-of-principle study in which we applied a metabolomics pipeline specifically developed for L. donovani to characterize the global metabolic differences between antimonial-sensitive and antimonial-resistant L. donovani isolates. Clones of drug-sensitive and drug-resistant parasite isolates from clinical samples were cultured in vitro and harvested for metabolomics analysis. The relative abundance of 340 metabolites was determined by ZIC-HILIC chromatography coupled to LTQ-Orbitrap mass spectrometry. Our measurements cover approximately 20% of the predicted core metabolome of Leishmania and additionally detected a large number of lipids. Drug-sensitive and drug-resistant parasites showed distinct metabolic profiles, and unsupervised clustering and principal component analysis clearly distinguished the two phenotypes. For 100 metabolites, the detected intensity differed more than three-fold between the 2 phenotypes. Many of these were in specific areas of lipid metabolism, suggesting that the membrane composition of the drug-resistant parasites is extensively modified. Untargeted metabolomics has been applied on clinical Leishmania isolates to uncover major metabolic differences between drug-sensitive and drug-resistant isolates. The identified major differences provide novel insights into the mechanisms involved in resistance to antimonial drugs, and facilitate investigations using targeted approaches to unravel the key changes mediating drug resistance.

[Therapy of leishmaniasis in France: consensus on proposed guidelines]

Because it relies on potentially toxic, difficult-to-handle, or expensive compounds the therapy of leishmaniasis is still a complex issue in 2010, especially for visceral leishmaniasis in immuno-suppressed subjects, or in patients with cutaneous and mucosal involvement. This induces a wide diversity of observed therapeutic practices, some being sub-optimal. The Société de Pathologie Exotique organised a meeting dedicated to the therapy of leishmaniasis in France that led to the first consensus on therapeutic guidelines. Liposomal amphotericin B is the first-line option for visceral leishmaniasis both in immunocompetent, and immunosuppressed patients (cumulated doses of 20 mg/kg and 30-40 mg/kg, respectively). Secondary prophylaxis with either liposomal amphotericin B, pentamidine or meglumine antimoniate is proposed to patients with heavy immunosuppression until immunity has been restored for at least 6 months. While the efficacy of new topical formulations of paromomycin is being tested, patients with Old World cutaneous leishmaniasis may be left untreated, or be administered a combination of superficial cryotherapy plus intralesional antimony, or even--in complex situations--receive systemic therapy. The efficacy of a short course of pentamidine (L. guyanensis/L. panamensis) and a 20-day schedule of meglumine antimoniate (L. braziliensis) is solidly established. However, in well-defined situations, local therapy of New World cutaneous leishmaniasis is now considered acceptable.

Antileishmanial and antitrypanosomal activities of the 8-aminoquinoline tafenoquine

The 8-aminoquinoline tafenoquine showed significant in vitro activity against Leishmania species, including L. donovani amastigotes in macrophages, with 50% inhibitory concentrations (IC(50)s) between 0.1 and 4.0 μM for both pentavalent antimony (SbV)-sensitive and SbV-resistant strains and by oral administration in BALB/c mice, with 50% effective dose (ED(50)) values of 1.2 to 3.5 mg/kg for 5 days. Tafenoquine was less active against intracellular Trypanosoma cruzi amastigotes, with an IC(50) of 21.9 μM.

Frequency of drug resistance gene amplification in clinical leishmania strains

Experimental studies about Leishmania resistance to metal and antifolates have pointed out that gene amplification is one of the main mechanisms of drug detoxification. Amplified genes code for adenosine triphosphate-dependent transporters (multidrug resistance and P-glycoproteins P), enzymes involved in trypanothione pathway, particularly gamma glutamyl cysteine synthase, and others involved in folates metabolism, such as dihydrofolate reductase and pterine reductase. The aim of this study was to detect and quantify the amplification of these genes in clinical strains of visceral leishmaniasis agents: Leishmania infantum, L. donovani, and L. archibaldi. Relative quantification experiments by means of real-time polymerase chain reaction showed that multidrug resistance gene amplification is the more frequent event. For P-glycoproteins P and dihydrofolate reductase genes, level of amplification was comparable to the level observed after in vitro selection of resistant clones. Gene amplification is therefore a common phenomenon in wild strains concurring to Leishmania genomic plasticity. This finding, which corroborates results of experimental studies, supports a better understanding of metal resistance selection and spreading in endemic areas.

Monitoring the efficacy of antimicrobial photodynamic therapy in a murine model of cutaneous leishmaniasis using L. major expressing GFP

A murine model of cutaneous leishmaniasis with green fluorescent protein positive (GFP+) L. major enables the monitoring of parasitic load via measurements of GFP fluorescence intensity, allowing for a faster and more efficient way of monitoring the clinical outcome of photodynamic therapy (PDT). This model may provide new insights on the phototoxic aspects in PDT. Although PDT regimens may be somewhat different in humans, it is expected that the developed model will facilitate the optimization and clinical translation of PDT as a therapy for cutaneous leishmaniasis and the eventual development of topical PDT treatments for other granulomatous infections.

Inhibition of receptor tyrosine kinases restores immunocompetence and improves immune-dependent chemotherapy against experimental leishmaniasis in mice

Receptor tyrosine kinases are involved in multiple cellular processes, and drugs that inhibit their action are used in the clinic to treat several types of cancer. However, the value of receptor tyrosine kinase inhibitors (RTKIs) for treating infectious disease has yet to be explored. Here, we have shown in mice that administration of the broad-spectrum RTKI sunitinib maleate (Sm) blocked the vascular remodeling and progressive splenomegaly associated with experimental visceral leishmaniasis. Furthermore, Sm treatment restored the integrity of the splenic microarchitecture. Although restoration of splenic architecture was accompanied by an increase in the frequency of IFN-gamma+CD4+ T cells, Sm treatment alone was insufficient to cause a reduction in tissue parasite burden. However, preconditioning by short-term Sm treatment proved to be successful as an adjunct therapy, increasing the frequency of IFN-gamma+ and IFN-gamma+TNF+CD4+ T cells, enhancing NO production by splenic macrophages, and providing dose-sparing effects when combined with a first-line immune-dependent anti-leishmanial drug. We propose, therefore, that RTKIs may prove clinically useful as agents to restore immune competence before the administration of chemo- or immunotherapeutic drugs in the treatment of visceral leishmaniasis or other diseases involving lymphoid tissue remodeling, including cancer.

Differentiation of Leishmania (Viannia) panamensis and Leishmania (V.) guyanensis using BccI for hsp70 PCR-RFLP

Leishmania panamensis and Leishmania guyanensis are two species of the subgenus Viannia that are genetically very similar. Both parasites are usually associated with cutaneous leishmaniasis, but also have the potential to cause the mucocutaneous form of the disease. In addition, the study of foci and consequently the identification of vectors and probable reservoirs involved in transmission require a correct differentiation between both species, which is important at epidemiological level. We explored the possibility of identifying these species by using restriction fragment length polymorphisms (RFLP) in the gene coding for heat-shock protein 70 (hsp70). Previously, an hsp70 PCR-RFLP assay proved to be very effective in differentiating other Leishmania species when HaeIII is used as restriction enzyme. Based on hsp70 sequences analysis, BccI was found to generate species-specific fragments that can easily be recognized by agarose gel electrophoresis. Using the analysis of biopsies, scrapings, and parasite isolates previously grouped in a cluster comprising both L. panamensis and L. guyanensis, we showed that our approach allowed differentiation of both entities. This offers the possibility not only for identification of parasites in biological samples, but also to apply molecular epidemiology in certain countries of the New World, where several Leishmania species could coexist.

Water-soluble polymer-drug conjugates for combination chemotherapy against visceral leishmaniasis

There is a need for new safe, effective and short-course treatments for leishmaniasis; one strategy is to use combination chemotherapy. Polymer–drug conjugates have shown promise for the delivery of anti-leishmanial agents such as amphotericin B. In this paper, we report on the preparation and biological evaluation of polymer–drug conjugates of N-(2-hydroxypropyl)methacrylamide (HPMA), amphotericin B and alendronic acid. The combinatorial polymer–drug conjugates were effective anti-leishmanial agents in vitro and in vivo, but offered no advantage over the single poly(HPMA)–amphotericin B conjugates.

Clinical risk factors for therapeutic failure in kala-azar patients treated with pentavalent antimonials in Nepal

Drug-related factors and parasite resistance have been implicated in the failure of pentavalent antimonials (Sb(v)) in the Indian subcontinent; however, little information is available on host-related factors. Parasitologically confirmed kala-azar patients, treatment naïve to Sb(v), were prospectively recruited at a referral hospital in Nepal and were treated under supervision with 30 doses of quality-assured sodium stibogluconate (SSG) 20mg/kg/day and followed for 12 months to assess cure. Analysis of risk factors for treatment failure was assessed in those receiving >or=25 doses and completing 12 months of follow-up. One hundred and ninety-eight cases were treated with SSG and the overall cure rate was 77.3% (153/198). Of the 181 cases who received >or=25 doses, 12-month follow-up data were obtained in 169, comprising 153 patients (90.5%) with definite cure and 16 (9.5%) treatment failures. In the final logistic regression model, increased failure to SSG was significantly associated with fever for >or=12 weeks [odds ratio (OR)=7.4], living in districts bordering the high SSG resistance zone in Bihar (OR=6.1), interruption of treatment (OR=4.3) and ambulatory treatment (OR=10.2). Early diagnosis and supervised treatment is of paramount importance to prevent treatment failures within the control programme.

Neglected tropical diseases in sub-saharan Africa: review of their prevalence, distribution, and disease burden

The neglected tropical diseases (NTDs) are the most common conditions affecting the poorest 500 million people living in sub-Saharan Africa (SSA), and together produce a burden of disease that may be equivalent to up to one-half of SSA's malaria disease burden and more than double that caused by tuberculosis. Approximately 85% of the NTD disease burden results from helminth infections. Hookworm infection occurs in almost half of SSA's poorest people, including 40-50 million school-aged children and 7 million pregnant women in whom it is a leading cause of anemia. Schistosomiasis is the second most prevalent NTD after hookworm (192 million cases), accounting for 93% of the world's number of cases and possibly associated with increased horizontal transmission of HIV/AIDS. Lymphatic filariasis (46-51 million cases) and onchocerciasis (37 million cases) are also widespread in SSA, each disease representing a significant cause of disability and reduction in the region's agricultural productivity. There is a dearth of information on Africa's non-helminth NTDs. The protozoan infections, human African trypanosomiasis and visceral leishmaniasis, affect almost 100,000 people, primarily in areas of conflict in SSA where they cause high mortality, and where trachoma is the most prevalent bacterial NTD (30 million cases). However, there are little or no data on some very important protozoan infections, e.g., amebiasis and toxoplasmosis; bacterial infections, e.g., typhoid fever and non-typhoidal salmonellosis, the tick-borne bacterial zoonoses, and non-tuberculosis mycobaterial infections; and arboviral infections. Thus, the overall burden of Africa's NTDs may be severely underestimated. A full assessment is an important step for disease control priorities, particularly in Nigeria and the Democratic Republic of Congo, where the greatest number of NTDs may occur.

Optimization of topical photodynamic therapy with 3,7-bis(di-n-butylamino)phenothiazin-5-ium bromide for cutaneous leishmaniasis

BACKGROUND AND OBJECTIVE

Photodynamic therapy (PDT) has evolved as a promising therapeutic measure for the treatment of cutaneous leishmaniasis (CL). In particular, phenothiazine compounds have demonstrated efficacy for PDT of CL. The objective of our present study is to define the use of a new specific phenothiazine photosensitizer, 3,7-bis(di-n-butylamino)phenothiazin-5-ium bromide (PPA904) applied topically as a cream to treat CL.

MATERIALS AND METHODS

To establish the optimal conditions for this treatment, we compared two different ways to improve current regimens of PDT with PPA904 cream (500 microM of PPA904 in Unguentum M) by changing the duration of topical application, and by administration of several consecutive PDT procedures. An initial regimen recommended by the manufacturer (Photopharmica Co. Ltd., Leeds, UK) was maintained as a control: the cream was applied topically for 30 minutes at a final concentration of PPA904 at 500 microM, and the designated treatment area was irradiated with a broad band light source of 665+/-15 nm at a fluence of 50 J/cm(2) (50 mW/cm(2)).

RESULTS

The best curative PPA904-PDT regimen was achieved under the conditions of a longer duration of topical application time (90 minutes) and several (three) consecutive treatments with 4-day intervals between treatments. The mechanisms responsible for such improvements (kinetics of drug penetration, depth of necrosis of the CL lesions after PDT, and daily changes in the parasitic load after PDT) are discussed in the present study.

CONCLUSION

Topical PPA904-PDT, implemented as described above, is a promising treatment for CL, and clinical studies will be initiated to establish efficacy in humans.

[Cutaneous leishmaniasis in rheumatoid arthritis]

INTRODUCTION

Cutaneous leishmaniasis is a protozoal infection. Its prevalence is increasing, especially in immunocompromised subjects.

CASE REPORTS

We report four patients with rheumatoid arthritis, treated with methotrexate and prednisone who developed cutaneous leishmaniasis. Clinical outcome was favorable after institution of antimony therapy in three cases despite the continuation of methotrexate and prednisone. One patient failed to respond to therapy.

DISCUSSION

The frequency of cutaneous leishmaniasis is increasing especially in immunocompromised subjects. In our patients, rheumatoid arthritis, corticosteroid therapy and methotrexate were predisposing factors of cutaneous leishmaniasis.

[Epidemiology of Leishmania (L.) infantum, L. major and L. killicki in Tunisia: results and analysis of the identification of 226 human and canine isolates]

The epidemiological situation of leishmaniasis in Tunisia is characterised by the co-existence in a very limited territory (165,000 km2, Sahara included), of 4 clinical forms: the infantile visceral leishmaniasis (VL) and 3 cutaneous leishmaniasis (CL) forms (sporadic, zoonotic and chronic). In addition to the useful epidemiological data, identification of the causative parasitic species is essential to determine the geographic distribution of each form and to select appropriate therapeutic procedure and suitable control measures. 226 Leishmania isolates, 135 human's coming from 59 VL cases and 76 CL cases and 91 canine's were identified by the isoenzyme electrophoresis reference technique. Results confirm the endemicity of the 4 forms mentioned above. The sporadic CL, confined to the North of the country is principally caused by L. infantum MON-24 (72.2%). VL which has reached the southern ridge in the central area of Tunisia, in the governorate of Kairouan (36 typed isolates), presents an unusual high proportion of L. infantum MON-24. In fact, this zymodeme, rather dermotropic is responsible for 47.2% of the cases vs 13% in the other regions of the country where L. infantum MON-1 remains predominant with 78.3% of typed isolates, the difference being statistically significant (P < 0.01). A third zymodeme, L. infantum MON-80 is sporadically pointed out during VL or in sporadic CL. Despite the high number of canine isolates (n=91) coming from 6 governorates, only the zymodeme L. infantum MON-1 was identified, letting hypothetic the reservoir of the 2 other zymodemes of the species identified in humans. Those absences may be related to cross infections, with a low sensitivity to L. infantum MON-24 leading to a selection of MON-1 at the time of culture passages. Hence it is important to develop molecular tools of direct identification on initial biological samples without going through cultures. Zoonotic CL remains the predominant cutaneous form in the central and southern area of Tunisia. However L. killicki, agent of the chronic CL, is confirming its presence out of its original focus of Tataouine in the southern-east of the country in both zoonotic CL and VL areas.

[Immigration and HIV Infection. An approximation to parasitic and viral infections]

Highly-active antiretroviral therapy is effective in reducing opportunistic infections in industrialized countries. However, opportunistic parasitic infections remain the leading cause of HIV-related mortality in developing countries. These infections can also affect HIV-positive immigrants residing in Spain, as well as HIV-infected patients traveling to low-income countries. In addition, immigrants often have viral infections caused by herpesvirus, papillomavirus and polyomavirus, which are closely related to risk behaviors and commercial sex. The present article reviews the characteristics of parasitic and viral infections in patients with HIV infection with the aim of improving understanding of this vulnerable population group.

Sitamaquine sensitivity in Leishmania species is not mediated by drug accumulation in acidocalcisomes

Sitamaquine (WR6026), an 8-aminoquinoline derivative, is a new antileishmanial oral drug. As a lipophilic weak base, it rapidly accumulates in acidic compartments, represented mainly by acidocalcisomes. In this work, we show that the antileishmanial action of sitamaquine is unrelated to its level of accumulation in these acidic vesicles. We have observed significant differences in sitamaquine sensitivity and accumulation between Leishmania species and strains, and interestingly, there is no correlation between them. However, there is a relationship between the levels of accumulation of sitamaquine and acidotropic probes, acidocalcisomes size, and polyphosphate levels. The Leishmania major AP3delta-null mutant line, in which acidocalcisomes are devoid of their usual polyphosphate and proton content, is unable to accumulate sitamaquine; however, both the parental strain and the AP3delta-null mutants showed similar sensitivities to sitamaquine. Our findings provide clear evidence that the antileishmanial action of sitamaquine is unrelated to its accumulation in acidocalcisomes.

Acute renal failure due to visceral leishmaniasis by Leishmania infantum successfully treated with a single high dose of liposomal amphotericin B

We report a visceral leishmaniasis case in an immunocompetent immigrant with acute renal failure. Parasites were demonstrated in bone marrow, peripheral blood, and kidney samples. A collapsing focal segmental glomerulosclerosis was documented, which was successfully treated with a single infusion of 10 mg/kg liposomal amphotericin B.