Efficacy of Miltefosine in the Treatment of Visceral Leishmaniasis in India After a Decade of Use

Transcriptome profiling identifies genes/pathways associated with experimental resistance to paromomycin in Leishmania donovani

Widespread resistance towards antimony and reports of relapses following miltefosine treatment has severely affected the management of visceral leishmaniasis (VL) in the Indian subcontinent. Paromomycin (PMM), an aminoglycoside antibiotic, has been licensed for VL treatment in India in 2007. Although its use is still restricted in the field, unraveling the molecular mechanism of resistance towards PMM is the key to preserve the drug. In this study, PMM resistant lines were selected up to 100 μM of PMM in three distinct field isolates of Leishmania donovani at promastigote stage. The resistance induced at promastigote level was also evident in amastigotes which showed 6 fold decreases in PMM susceptibility. Comparative transcriptome profiling of PMM resistant (PMM-R) and the corresponding PMM sensitive (PMM-S) parasites revealed modulated expression of 500 genes (1.5 fold cut off) in PMM-R parasites. Selected genes were validated for their modulated expression by quantitative real-time PCR. Functional classification and pathway analysis of modulated genes indicated probable adaptations in drug resistant lines which included a) reduced oxidative phosphorylation; b) increased glycosomal succinate fermentation and substrate level phosphorylation; c) dependency on lipids and amino acids for energy generation; d) reduced DNA synthesis and increased DNA damage repair and e) decreased protein synthesis and degradation. Interestingly, PMM-R parasites showed a marked increase in PMM susceptibility in presence of verapamil and amlodipine, antagonists of Ca2+ channel that are also modulators of ABC transporters. Moreover, infection of macrophages by PMM-R parasites led to modulated nitric oxide (NO) levels while reactive oxygen species (ROS) level remained unaltered. The present study highlights the putative mechanisms of PMM resistance in Leishmania.

Post-kala-azar dermal leishmaniasis in the Indian subcontinent: A threat to the South-East Asia Region Kala-azar Elimination Programme

Background

The South-East Asia Region Kala-azar Elimination Programme (KAEP) is expected to enter the consolidation phase in 2017, which focuses on case detection, vector control, and identifying potential sources of infection. Post-kala-azar dermal leishmaniasis (PKDL) is thought to play a role in the recurrence of visceral leishmaniasis (VL)/kala-azar outbreaks, and control of PKDL is among the priorities of the KAEP.

Methodology and principal finding

We reviewed the literature with regard to PKDL in Asia and interpreted the findings in relation to current intervention methods in the KAEP in order to make recommendations. There is a considerable knowledge gap regarding the pathophysiology of VL and PKDL, especially the underlying immune responses. Risk factors (of which previous VL treatments may be most important) are poorly understood and need to be better defined. The role of PKDL patients in transmission is largely unknown, and there is insufficient information about the importance of duration, distribution and severity of the rash, time of onset, and self-healing. Current intervention methods focus on active case detection and treatment of all PKDL cases with miltefosine while there is increasing drug resistance. The prevention of PKDL by improved VL treatment currently receives insufficient attention.

Conclusion and significance

PKDL is a heterogeneous and dynamic condition, and patients differ with regard to time of onset after VL, chronicity, and distribution and appearance of the rash, as well as immune responses (including tendency to self-heal), all of which may vary over time. It is essential to fully describe the pathophysiology in order to make informed decisions on the most cost-effective approach. Emphasis should be on early detection of those who contribute to transmission and those who are in need of treatment, for whom short-course, effective, and safe drug regimens should be available. The prevention of PKDL should be emphasised by innovative and improved treatment for VL, which may include immunomodulation.

Efficacy and Safety of Liposomal Amphotericin B for Visceral Leishmaniasis in Children and Adolescents at a Tertiary Care Center in Bihar, India

Liposomal amphotericin B is being used increasingly to reduce the burden of kala-azar from the Indian subcontinent. There are studies which have evaluated efficacy and safety of liposomal amphotericin B for visceral leishmaniasis in all age groups. However, the only study that specifically addressed treatment of childhood visceral leishmaniasis did not include all ages or document renal and liver function. We, therefore, felt it was important to reassess the efficacy and safety of single dose liposomal amphotericin B in children and adolescents. A total of 100 parasitologically confirmed visceral leishmaniasis patients aged < 15 years were included in this study. Participants consisted of 65 males and 35 females. All of them had come from the endemic region of Bihar. They were administered one dose intravenous infusion of liposomal amphptericin B at 10 mg/kg body weight. Efficacy was assessed as initial and final cure at 1 and 6 months, respectively, and safety of all participants who were recruited in the study. The initial and final cure rate by per protocol analysis was 100% and 97.9%, respectively. Chills and rigors were the most commonly occurring adverse events (AEs). All the AEs were mild in intensity, and none of the patients experienced any serious AEs. No patients developed nephrotoxicity. Our finding indicates that liposomal amphotericin B at 10 mg/kg body weight is safe and effective in children. Results of our study support the use of single dose liposomal amphotericin B in all age group populations for elimination of kala-azar from the Indian subcontinent.

Leishmania and other intracellular pathogens: selectivity, drug distribution and PK-PD

New drugs and treatments for diseases caused by intracellular pathogens, such as leishmaniasis and the Leishmania species, have proved to be some of the most difficult to discover and develop. The focus of discovery research has been on the identification of potent and selective compounds that inhibit target enzymes (or other essential molecules) or are active against the causative pathogen in phenotypic in vitro assays. Although these discovery paradigms remain an essential part of the early stages of the drug R & D pathway, over the past two decades additional emphasis has been given to the challenges needed to ensure that the potential anti-infective drugs distribute to infected tissues, reach the target pathogen within the host cell and exert the appropriate pharmacodynamic effect at these sites. This review will focus on how these challenges are being met in relation to Leishmania and the leishmaniases with lessons learned from drug R & D for other intracellular pathogens.

Miltefosine Resistant Field Isolate From Indian Kala-Azar Patient Shows Similar Phenotype in Experimental Infection

Emergence of resistance to drugs used to treat the Indian Kala-azar patients makes control strategy shattered. In this bleak situation, Miltefosine (MIL) was introduced to treat mainly antimonial unresponsive cases. Within years, resistance to MIL has been reported. While checking the MIL sensitivity of the recent KA clinical isolates (n = 26), we came across one isolate which showed four times more EC₅₀ for MIL than that of MIL-Sensitive (MIL-S) isolates and considered as putative MIL-Resistant (MIL-R). The expressions of LdMT and LdRos3 genes of this isolate were found down regulated. Th1/Th2 cytokines, ROS and NO, FACS dot plots and mitochondrial trans membrane potential measurement were performed. In vivo hamster model with this MIL-R isolate showed much lesser reduction in liver weight (17.5%) compared to average reduction in liver weight (40.2%) of the animals infected with MIL-S isolates. The splenic and hepatic stamps smears of MIL-R infected hamsters revealed the retention of parasite load of about 51.45%. The splenocytes of these animals failed to proliferate anti leishmanial T-cells and lack of cell mediated immunity hampered recovery. Thus, these phenotypic expressions of experimental model may be considered similar to that of the MIL unresponsive patients. This is first such kind of report.

Mitochondria and lipid raft-located FOF1-ATP synthase as major therapeutic targets in the antileishmanial and anticancer activities of ether lipid edelfosine

Background

Leishmaniasis is the world’s second deadliest parasitic disease after malaria, and current treatment of the different forms of this disease is far from satisfactory. Alkylphospholipid analogs (APLs) are a family of anticancer drugs that show antileishmanial activity, including the first oral drug (miltefosine) for leishmaniasis and drugs in preclinical/clinical oncology trials, but their precise mechanism of action remains to be elucidated.

Methodology/Principal findings

Here we show that the tumor cell apoptosis-inducer edelfosine was the most effective APL, as compared to miltefosine, perifosine and erucylphosphocholine, in killing Leishmania spp. promastigotes and amastigotes as well as tumor cells, as assessed by DNA breakdown determined by flow cytometry. In studies using animal models, we found that orally-administered edelfosine showed a potent in vivo antileishmanial activity and diminished macrophage pro-inflammatory responses. Edelfosine was also able to kill Leishmania axenic amastigotes. Edelfosine was taken up by host macrophages and killed intracellular Leishmania amastigotes in infected macrophages. Edelfosine accumulated in tumor cell mitochondria and Leishmania kinetoplast-mitochondrion, and led to mitochondrial transmembrane potential disruption, and to the successive breakdown of parasite mitochondrial and nuclear DNA. Ectopic expression of Bcl-X_L inhibited edelfosine-induced cell death in both Leishmania parasites and tumor cells. We found that the cytotoxic activity of edelfosine against Leishmania parasites and tumor cells was associated with a dramatic recruitment of F_OF₁-ATP synthase into lipid rafts following edelfosine treatment in both parasites and cancer cells. Raft disruption and specific F_OF₁-ATP synthase inhibition hindered edelfosine-induced cell death in both Leishmania parasites and tumor cells. Genetic deletion of F_OF₁-ATP synthase led to edelfosine drug resistance in Saccharomyces cerevisiae yeast.

Conclusions/Significance

The present study shows that the antileishmanial and anticancer actions of edelfosine share some common signaling processes, with mitochondria and raft-located F_OF₁-ATP synthase being critical in the killing process, thus identifying novel druggable targets for the treatment of leishmaniasis.

Leishmaniasis is a major health problem worldwide, and can result in loss of human life or a lifelong stigma because of bodily scars. According to World Health Organization, leishmaniasis is considered as an emerging and uncontrolled disease, and its current treatment is far from ideal, with only a few drugs available that could lead to drug resistance or cause serious side-effects. Here, we have found that mitochondria and raft-located F_OF₁-ATPase synthase are efficient druggable targets, through which an ether lipid named edelfosine exerts its antileishmanial action. Edelfosine effectively kills Leishmania spp. promastigotes and amastigotes. Our experimental animal models demonstrate that oral administration of edelfosine exerts a potent antileishmanial activity, while inhibits macrophage pro-inflammatory responses. Our results show that both Leishmania and tumor cells share mitochondria and raft-located F_OF₁-ATPase synthase as major druggable targets in leishmaniasis and cancer therapy. These data, showing a potent antileishmanial activity of edelfosine and unveiling its mechanism of action, together with the inhibition of the inflammatory responses elicited by macrophages, suggest that the ether lipid edelfosine is a promising oral drug for leishmaniasis, and highlight mitochondria and lipid raft-located F_OF₁-ATP synthase as major therapeutic targets for the treatment of this disease.

Increased miltefosine tolerance in clinical isolates of Leishmania donovani is associated with reduced drug accumulation, increased infectivity and resistance to oxidative stress

BACKGROUND

Miltefosine (MIL) is an oral antileishmanial drug used for treatment of visceral leishmaniasis (VL) in the Indian subcontinent. Recent reports indicate a significant decline in its efficacy with a high rate of relapse in VL as well as post kala-azar dermal leishmaniasis (PKDL). We investigated the parasitic factors apparently involved in miltefosine unresponsiveness in clinical isolates of Leishmania donovani.

METHODOLOGY

L. donovani isolated from patients of VL and PKDL at pretreatment stage (LdPreTx, n = 9), patients that relapsed after MIL treatment (LdRelapse, n = 7) and parasites made experimentally resistant to MIL (LdM30) were included in this study. MIL uptake was estimated using liquid chromatography coupled mass spectrometry. Reactive oxygen species and intracellular thiol content were measured fluorometrically. Q-PCR was used to assess the differential expression of genes associated with MIL resistance.

RESULTS

LdRelapse parasites exhibited higher IC50 both at promastigote level (7.92 ± 1.30 μM) and at intracellular amastigote level (11.35 ± 6.48 μM) when compared with LdPreTx parasites (3.27 ± 1.52 μM) and (3.85 ± 3.11 μM), respectively. The percent infectivity (72 hrs post infection) of LdRelapse parasites was significantly higher (80.71 ± 5.67%, P<0.001) in comparison to LdPreTx (60.44 ± 2.80%). MIL accumulation was significantly lower in LdRelapse parasites (1.7 fold, P<0.001) and in LdM30 parasites (2.4 fold, P<0.001) when compared with LdPreTx parasites. MIL induced ROS levels were significantly lower (p<0.05) in macrophages infected with LdRelapse while intracellular thiol content were significantly higher in LdRelapse compared to LdPreTx, indicating a better tolerance for oxidative stress in LdRelapse isolates. Genes associated with oxidative stress, metabolic processes and transporters showed modulated expression in LdRelapse and LdM30 parasites in comparison with LdPreTx parasites.

CONCLUSION

The present study highlights the parasitic factors and pathways responsible for miltefosine unresponsiveness in VL and PKDL.

Safety and efficacy of short course combination regimens with AmBisome, miltefosine and paromomycin for the treatment of visceral leishmaniasis (VL) in Bangladesh

Background

AmBisome therapy for VL has an excellent efficacy and safety profile and has been adopted as a first-line regimen in Bangladesh. Second-line treatment options are limited and should preferably be given in short course combinations in order to prevent the development of resistant strains. Combination regimens including AmBisome, paromomycin and miltefosine have proved to be safe and effective in the treatment of VL in India. In the present study, the safety and efficacy of these same combinations were assessed in field conditions in Bangladesh.

Methods

The safety and efficacy of three combination regimens: a 5 mg/kg single dose of AmBisome + 7 subsequent days of miltefosine (2.5 mg/kg/day), a 5 mg/kg single dose of AmBisome + 10 subsequent days of paromomycin (15 mg/kg/day) and 10 days of paromomycin (15 mg/kg/day) + miltefosine (2.5 mg/kg/day), were compared with a standard regimen of AmBisome 15 mg/kg given in 5 mg/kg doses on days 1, 3 and 5. This was a phase III open label, individually randomized clinical trial. Patients from 5 to 60 years with uncomplicated primary VL were recruited from the Community Based Medical College Bangladesh (CBMC,B) and the Upazila Health Complexes of Trishal, Bhaluka and Fulbaria (all located in Mymensingh district), and randomly assigned to one of the treatments. The objective was to assess safety and definitive cure at 6 months after treatment.

Results

601 patients recruited between July 2010 and September 2013 received either AmBisome monotherapy (n = 158), AmBisome + paromomycin (n = 159), AmBisome + miltefosine (n = 142) or paromomycin + miltefosine (n = 142). At 6 months post- treatment, final cure rates for the intention-to-treat population were 98.1% (95%CI 96.0–100) for AmBisome monotherapy, 99.4% (95%CI 98.2–100) for the AmBisome + paromomycin arm, 94.4% (95%CI 90.6–98.2) for the AmBisome + miltefosine arm, and 97.9% (95%CI 95.5–100) for paromomycin + miltefosine arm. There were 12 serious adverse events in the study in 11 patients that included 3 non-study drug related deaths. There were no relapses or PKDL up to 6 months follow-up. All treatments were well tolerated with no unexpected side effects. Adverse events were most frequent during treatment with miltefosine + paromomycin, three serious adverse events related to the treatment occurred in this arm, all of which resolved.

Conclusion

None of the combinations were inferior to AmBisome in both the intention-to-treat and per-protocol populations. All the combinations demonstrated excellent overall efficacy, were well tolerated and safe, and could be deployed under field conditions in Bangladesh. The trial was conducted by the International Centre for Diarrhoeal Disease Research (ICDDR,B) and the Shaheed Suhrawardy Medical College (ShSMC), Dhaka, in collaboration with the trial sites and sponsored by the Drugs for Neglected Diseases initiative (DNDi).

Trial registration

ClinicalTrials.gov NCT01122771

Treatment is one of the key strategies for visceral leishmaniasis control and elimination. Historically a number of monotherapy drugs for VL treatment were used in Bangladesh, including pentavalent antimonials, amphotericin B deoxycholate (AmB), and miltefosine (MF). With the limited number of drugs available, it was necessary to preserve existing drugs and also to develop shorter and safer treatment regimens. At the time the study was initiated, miltefosine monotherapy was a recommended first-line treatment in Bangladesh. The present study aimed to provide safety and efficacy data for three short-course combination regimens including AmBisome, miltefosine and paromomycin when rolled out in field conditions in Bangladesh, and to compare these to AmBisome monotherapy. All combinations proved non-inferior to AmBisome monotherapy and were safe and well tolerated. This study was implemented in field conditions at Upazila level with treatment provided by government doctors, providing further evidence for scaling up new regimens in national program contexts within the public health sector.

To evaluate efficacy and safety of amphotericin B in two different doses in the treatment of post kala-azar dermal leishmaniasis (PKDL)

Background

Post kala-azar dermal leishmaniasis (PKDL) is a skin disorder that usually occurs among patients with a past history of visceral leishmaniasis (VL). Cases are also reported without a history of VL. There is no satisfactory treatment regimen available at present. We aimed to compare the efficacy and safety of amphotericin B in two different doses (0.5mg/kg vs 1mg/kg) in a prospective randomized trial in 50 PKDL patients.

Methods

In this open label study 50 patients with PKDL, aged between 5–60 years were randomized in two groups. Group A received amphotericin B in the dose of 0.5 mg/kg in 5% dextrose, daily for 20 infusions for 3 courses at an interval of 15 days between each course and Group B received amphotericin B in the dose of 1mg/kg in 5% dextrose on alternate days, 20 infusions for 3 courses an interval of 15 days between each course and followed up for one year.

Results

A total of 50 patients were enrolled, 25 in each of group A and group B. Two patients lost to follow up and three patients withdrew consent due to adverse events. The initial cure rate was 92% in group A and 88% in group B by intention to treat analysis and final cure rate by per protocol analysis was 95.65% and 95.45% in group A and group B respectively. Two patients each from either group relapsed. Nephrotoxicity was the most common adverse event occurring in both the groups.

Conclusion

The lower dose appears to have fewer adverse events however, nephrotoxicity remains a problem in both regimens. The 0.5mg/kg regimen may be considered instead of the higher dosage however safer treatments remain critical for PKDL treatment.

Laboratory confirmed miltefosine resistant cases of visceral leishmaniasis from India

BACKGROUND

Miltefosine unresponsive and relapse cases of visceral leishmaniasis (VL) are increasingly being reported. However, there has been no laboratory confirmed reports of miltefosine resistance in VL. Here, we report two laboratory confirmed cases of VL from India.

METHODS

Two patients with VL were referred to us with suspected VL. The first patient was a native of the VL endemic state of Bihar, but residing in Delhi, a VL non-endemic area. He was treated with broad-spectrum antibiotics and antipyretics but was unresponsive to treatment. The second patient was from Jharkhand state in eastern India (adjoining Bihar), another endemic state for VL. He was refractory to anti-leishmanial treatment, which included administration of miltefosine. Following investigation, both patients were serologically positive for VL, and blood buffy coat from both patients grew Leishmania donovani. The isolates derived from both cases were characterized for their drug susceptibility, genetically characterised, and SNPs typed for LdMT and LdROS gene expression. Both patients were successfully treated with amphotericin B.

RESULTS

The in vitro drug susceptibility assays carried out on both isolates showed good IC₅₀ values to amphotericin B (0.1 ± 0.0004 μg/ml and 0.07 ± 0.0019 μg/ml). One isolate was refractory to Sb^III with an IC₅₀ of > 200 μM while the second isolate was sensitive to Sb^III with an IC₅₀ of 36.70 ± 3.2 μM. However, in both the isolates, IC₅₀ against miltefosine was more than 10-fold higher (> 100 μM) than the standard strain DD8 (6.8 ± 0.1181 μM). Furthermore, genetic analyses demonstrated single nucleotide polymorphisms (SNPs) (₃₅₄Tyr↔Phe and ₁₀₇₈Phe↔Tyr) in the LdMT gene of the parasites.

CONCLUSIONS

Here, we document two laboratory confirmed cases of miltefosine resistant VL from India. Our finding highlights the urgent need to establish control measures to prevent the spread of these strains. We also propose that LdMT gene mutation analysis could be used as a molecular marker of miltefosine resistance in L. donovani.

Chemotherapy of leishmaniasis: present challenges

Cutaneous and visceral leishmaniasis are amongst the most devastating infectious diseases of our time, affecting millions of people worldwide. The treatment of these serious diseases rely on a few chemotherapeutic agents, most of which are of parenteral use and induce severe side-effects. Furthermore, rates of treatment failure are high and have been linked to drug resistance in some areas. Here, we reviewed data on current chemotherapy practice in leishmaniasis. Drug resistance and mechanisms of resistance are described as well as the prospects for applying drug combinations for leishmaniasis chemotherapy. It is clear that efforts for discovering new drugs applicable to leishmaniasis chemotherapy are essential. The main aspects on the various steps of drug discovery in the field are discussed.

Experience with miltefosine for persistent or relapsing visceral leishmaniasis in solid organ transplant recipients: A case series from Spain

The incidence of visceral leishmaniasis (VL) after solid organ transplantation (SOT) is increasing. The optimal therapy for post-transplant VL remains unclear, as relapses after liposomal amphotericin B (L-AmB) are common. Miltefosine has been shown to be effective for treating VL in immunocompetent patients, although data in the specific population of SOT recipients are lacking. In the setting of an outbreak of leishmaniasis occurring in Southwest Madrid, we reviewed our experience in 6 SOT recipients with persistent or relapsing VL who received a 28-day course of miltefosine (2.5 mg/kg/day) as salvage therapy. All patients had been treated previously with L-AmB as first-line therapy. The incident episode of VL occurred at a median of 14 months after transplantation. Two patients experienced persistent infection and the remaining 4 had a relapse after a median interval of 168 days since the completion of the course of L-AmB. All the patients had an apparent initial clinical improvement with miltefosine. However, VL relapsed in 3 of them (after a median interval of 46 days), which required retreatment with L-AmB-based regimens. Miltefosine therapy was followed by a prolonged secondary prophylaxis with L-AmB in the only 2 cases with sustained clinical response and ongoing immunosuppression. No adverse effects associated with miltefosine were observed. Albeit limited, our experience suggests that miltefosine monotherapy likely has a limited utility to obtain a long-lasting clinical response in complicated (persistent or relapsing) forms of post-transplant VL, although its role in association with L-AmB-based secondary prophylaxis may merit further investigation.

Exploiting Knowledge on Leishmania Drug Resistance to Support the Quest for New Drugs

New drugs are needed to control leishmaniasis and efforts are currently on-going to counter the neglect of this disease. We discuss here the utility and the impact of associating drug resistance (DR) studies to drug discovery pipelines. We use as paradigm currently used drugs, antimonials and miltefosine, and complement our reflection by interviewing three experts in the field. We suggest DR studies to be involved at two different stages of drug development: (i) the efficiency of novel compounds should be confirmed on sets of strains including recent clinical isolates with DR; (ii) experimental DR should be generated to promising compounds at an early stage of their development, to further optimize them and monitor clinical trials.

Genetic markers for antimony resistant clinical isolates differentiation from Indian Kala-azar

Visceral Leishmaniasis or Kala-azar is caused by the protozoan parasites belonging to the Genus Leishmania. Once thought eradicated from the Indian subcontinent, the disease came back with drug resistance to almost all prevalent drugs. Molecular epidemiological studies revealed the polymorphic nature of the population of the main player of the disease, Leishmania donovani and involvement of other species (L. tropica) and other genus (Leptomonas) with the disease. This makes control measures almost futile. It also strongly demands the characterization of each and every isolate mandatory which is not done. In this background, the present study has been carried out to assess the genetic attributes of each clinical isolates (n=26) of KA and PKDL patients from India and Bangladesh. All the isolates were characterized through Restriction Fragment Length Polymorphism (RFLP) analysis to ascertain their species identity. 46.2% of the isolates were found to be Sodium Stibogluconate (SSG) resistant by amastigote-macrophage model. When the clinical isolates were subjected to Single Stranded Conformation Polymorphism (SSCP) of Internal Transcribed Spacer 1 (ITS1), Internal Transcribed Spacer 2 (ITS2) and some anonymous markers, the drug resistant Leishmania isolates of SSG can be distinguished from the sensitive isolates distinctly. This study showed for the first time, the genetic markers for SSG drug resistance of Indian Kala-azar clinical isolates.

A mitochondrial HSP70 (HSPA9B) is linked to miltefosine resistance and stress response in Leishmania donovani

Background

Protozoan parasites of the genus Leishmania are responsible for leishmaniasis, a neglected tropical disease affecting millions worldwide. Visceral leishmaniasis (VL), caused by Leishmania donovani, is the most severe form of leishmaniasis with high rates of mortality if left untreated. Current treatments include pentavalent antimonials and amphotericin B. However, high toxicity and emergence of resistance hinder the success of these options. Miltefosine (HePC) is the first oral treatment available for leishmaniasis. While treatment with HePC has proven effective, higher tolerance to the drug has been observed, and experimental resistance is easily developed in an in vitro environment. Several studies, including ours, have revealed that HePC resistance has a multi-factorial origin and this work aims to shed light on this complex mechanism.

Methods

2D-DIGE quantitative proteomics comparing the soluble proteomes of sensitive and HePC resistant L. donovani lines identified a protein of interest tentatively involved in drug resistance. To test this link, we employed a gain-of-function approach followed by mutagenesis analysis. Functional studies were complemented with flow cytometry to measure HePC incorporation and cell death.

Results

We identified a mitochondrial HSP70 (HSPA9B) downregulated in HePC-resistant L. donovani promastigotes. The overexpression of HSPA9B in WT lines confers an increased sensitivity to HePC, regardless of whether the expression is ectopic or integrative. Moreover, the increased sensitivity to HePC is specific to the HSPA9B overexpression since dominant negative mutant lines were able to restore HePC susceptibility to WT values. Interestingly, the augmented susceptibility to HePC did not correlate with an increased HePC uptake. Leishmania donovani promastigotes overexpressing HSPA9B were subjected to different environmental stimuli. Our data suggest that HSPA9B is capable of protecting cells from stressful conditions such as low pH and high temperature. This phenotype was further corroborated in axenic amastigotes overexpressing HSPA9B.

Conclusions

The results from this study provide evidence to support the involvement of a mitochondrial HSP70 (HSPA9B) in experimental HePC resistance, a mechanism that is not yet fully understood, and reveal potential fundamental roles of HSPA9B in the biology of Leishmania. Overall, our findings are relevant for current and future antileishmanial chemotherapy strategies.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-016-1904-8) contains supplementary material, which is available to authorized users.

Diagnosis and Treatment of Leishmaniasis: Clinical Practice Guidelines by the Infectious Diseases Society of America (IDSA) and the American Society of Tropical Medicine and Hygiene (ASTMH)

It is important to realize that leishmaniasis guidelines cannot always account for individual variation among patients. They are not intended to supplant physician judgment with respect to particular patients or special clinical situations. The IDSA and ASTMH consider adherence to these guidelines to be voluntary, with the ultimate determinations regarding their application to be made by the physician in the light of each patient's individual circumstances.

Progress in the Mathematical Modelling of Visceral Leishmaniasis

The leishmaniases comprise a complex of diseases characterized by clinical outcomes that range from self-limiting to chronic, and disfiguring and stigmatizing to life threatening. Diagnostic methods, treatments, and vector and reservoir control options exist, but deciding the most effective interventions requires a quantitative understanding of the population level infection and disease dynamics. The effectiveness of any set of interventions has to be determined within the context of operational conditions, including economic and political commitment. Mathematical models are the best available tools for studying quantitative systems crossing disciplinary spheres (biology, medicine, economics) within environmental and societal constraints. In 2005, the World Health Assembly and government health ministers of India, Nepal, and Bangladesh signed a Memorandum of Understanding to eliminate the life threatening form of leishmaniasis, visceral leishmaniasis (VL), on the Indian subcontinent by 2015 through a combination of early case detection, improved treatments, and vector control. The elimination target is <1 case/10,000 population at the district or subdistrict level compared to the current 20/10,000 in the regions of highest transmission. Towards this goal, this chapter focuses on mathematical models of VL, and the biology driving those models, to enable realistic predictions of the best combination of interventions. Several key issues will be discussed which have affected previous modelling of VL and the direction future modelling may take. Current understanding of the natural history of disease, immunity (and loss of immunity), and stages of infection and their durations are considered particularly for humans, and also for dogs. Asymptomatic and clinical infection are discussed in the context of their relative roles in Leishmania transmission, as well as key components of the parasite-sandfly-vector interaction and intervention strategies including diagnosis, treatment and vector control. Gaps in current biological knowledge and potential avenues to improve model structures and mathematical predictions are identified. Underpinning the marriage between biology and mathematical modelling, the content of this chapter represents the first step towards developing the next generation of models for VL.

Elimination of visceral leishmaniasis on the Indian subcontinent

Visceral leishmaniasis is a serious public health problem on the Indian subcontinent, causing high morbidity and mortality. The governments in the region launched a visceral leishmaniasis elimination initiative in 2005. We review knowledge gaps and research priorities. Key challenges include low coverage of health services for those most at risk, drug resistance, the absence of a vaccine, and the complex biology of the sandfly-human host transmission cycle. Vector control is an essential component, but innovation in this field is insufficient. Substantial progress has been made in the area of diagnostic, therapeutic, and vaccine development, but there are still many hurdles to overcome. For visceral leishmaniasis elimination to become a reality, effective deployment of these existing and new tools is essential. A strong commitment at community level is imperative, and appropriate diagnostic and treatment services as well as effective epidemiological surveillance need to be ensured.

Plasticity of the Leishmania genome leading to gene copy number variations and drug resistance

Leishmania has a plastic genome, and drug pressure can select for gene copy number variation (CNV). CNVs can apply either to whole chromosomes, leading to aneuploidy, or to specific genomic regions. For the latter, the amplification of chromosomal regions occurs at the level of homologous direct or inverted repeated sequences leading to extrachromosomal circular or linear amplified DNAs. This ability of Leishmania to respond to drug pressure by CNVs has led to the development of genomic screens such as Cos-Seq, which has the potential of expediting the discovery of drug targets for novel promising drug candidates.

Pharmacovigilance of Miltefosine in Treatment of Visceral Leishmaniasis in Endemic Areas of Bihar, India

Miltefosine, the only oral drug for visceral leishmaniasis (VL), is being used as the first-line drug under the VL elimination program in the Indian subcontinent. Miltefosine is an oral drug which was used as a topical application for skin metastasis of breast cancer. It was found to be effective against Leishmania donovani The main adverse events (AE) reported previously with miltefosine use includes diarrhea, vomiting, and dehydration. Other AEs include, raised serum alanine transaminase/aspartate aminotransferase and renal parameters such as creatinine. In this study, we report AEs in a large patient cohort of VL treated with miltefosine. The purpose of this pharmacovigilance study was to assess adverse drug reactions (ADRs)/AE of miltefosine treatment under unrestricted condition in the field setup. Patients were followed up to 6 months for therapeutic effectiveness. Outcomes of a larger data set of patients treated with this regimen from April 2012 to March 2015 were recorded. In the present study, 646 patients of VL were given miltefosine. Majority of the study subjects (58%) were male. Relapse occurred in 7% during follow-up period. Main causes of death were VL-pulmonary tuberculosis coinfection, extreme diarrhea, and acute pancreatitis which were reported in 1.7% subjects. Of 553 (85.6%) patients completing full course of treatment, 463 (83.7%) showed ADR with miltefosine during the study period. About 2.3% were suffering severe ADR, 51% from moderate, and the rest had mild ADR. The initial and final cure rate was 97.4% and 85.6%, respectively.

Characterization of a Novel Endoplasmic Reticulum Protein Involved in Tubercidin Resistance in Leishmania major

BACKGROUND

Tubercidin (TUB) is a toxic adenosine analog with potential antiparasitic activity against Leishmania, with mechanism of action and resistance that are not completely understood. For understanding the mechanisms of action and identifying the potential metabolic pathways affected by this drug, we employed in this study an overexpression/selection approach using TUB for the identification of potential targets, as well as, drug resistance genes in L. major. Although, TUB is toxic to the mammalian host, these findings can provide evidences for a rational drug design based on purine pathway against leishmaniasis.

METHODOLOGY/PRINCIPAL FINDINGS

After transfection of a cosmid genomic library into L. major Friedlin (LmjF) parasites and application of the overexpression/selection method, we identified two cosmids (cosTUB1 and cosTU2) containing two different loci capable of conferring significant levels of TUB resistance. In the cosTUB1 contained a gene encoding NUPM1-like protein, which has been previously described as associated with TUB resistance in L. amazonensis. In the cosTUB2 we identified and characterized a gene encoding a 63 kDa protein that we denoted as tubercidin-resistance protein (TRP). Functional analysis revealed that the transfectants were less susceptible to TUB than LmjF parasites or those transfected with the control vector. In addition, the trp mRNA and protein levels in cosTUB2 transfectants were higher than LmjF. TRP immunolocalization revealed that it was co-localized to the endoplasmic reticulum (ER), a cellular compartment with many functions. In silico predictions indicated that TRP contains only a hypothetical transmembrane domain. Thus, it is likely that TRP is a lumen protein involved in multidrug efflux transport that may be involved in the purine metabolic pathway.

CONCLUSIONS/SIGNIFICANCE

This study demonstrated for the first time that TRP is associated with TUB resistance in Leishmania. The next challenge is to determine how TRP mediates TUB resistance and whether purine metabolism is affected by this protein in the parasite. Finally, these findings may be helpful for the development of alternative anti-leishmanial drugs that target purine pathway.

Nitrotriazole-based acetamides and propanamides with broad spectrum antitrypanosomal activity

3-Nitro-1H-1,2,4-triazole-based acetamides bearing a biphenyl- or a phenoxyphenyl moiety have shown remarkable antichagasic activity both in vitro and in an acute murine model, as well as substantial in vitro antileishmanial activity but lacked activity against human African trypanosomiasis. We have shown now that by inserting a methylene group in the linkage to obtain the corresponding propanamides, both antichagasic and in particular anti-human African trypanosomiasis potency was increased. Therefore, IC50 values at low nM concentrations against both T. cruzi and T. b. rhodesiense, along with huge selectivity indices were obtained. Although several propanamides were active against Leishmania donovani, they were slightly less potent than their corresponding acetamides. There was a good correlation between lipophilicity (clogP value) and trypanocidal activity, for all new compounds. Type I nitroreductase, an enzyme absent from the human host, played a role in the activation of the new compounds, which may function as prodrugs. Antichagasic activity in vivo was also demonstrated with representative propanamides.

Transmission Dynamics of Visceral Leishmaniasis in the Indian Subcontinent - A Systematic Literature Review

Background

As Bangladesh, India and Nepal progress towards visceral leishmaniasis (VL) elimination, it is important to understand the role of asymptomatic Leishmania infection (ALI), VL treatment relapse and post kala-azar dermal leishmaniasis (PKDL) in transmission.

Methodology/ Principal Finding

We reviewed evidence systematically on ALI, relapse and PKDL. We searched multiple databases to include studies on burden, risk factors, biomarkers, natural history, and infectiveness of ALI, PKDL and relapse. After screening 292 papers, 98 were included covering the years 1942 through 2016. ALI, PKDL and relapse studies lacked a reference standard and appropriate biomarker. The prevalence of ALI was 4–17-fold that of VL. The risk of ALI was higher in VL case contacts. Most infections remained asymptomatic or resolved spontaneously. The proportion of ALI that progressed to VL disease within a year was 1.5–23%, and was higher amongst those with high antibody titres. The natural history of PKDL showed variability; 3.8–28.6% had no past history of VL treatment. The infectiveness of PKDL was 32–53%. The risk of VL relapse was higher with HIV co-infection. Modelling studies predicted a range of scenarios. One model predicted VL elimination was unlikely in the long term with early diagnosis. Another model estimated that ALI contributed to 82% of the overall transmission, VL to 10% and PKDL to 8%. Another model predicted that VL cases were the main driver for transmission. Different models predicted VL elimination if the sandfly density was reduced by 67% by killing the sandfly or by 79% by reducing their breeding sites, or with 4–6y of optimal IRS or 10y of sub-optimal IRS and only in low endemic setting.

Conclusion/ Significance

There is a need for xenodiagnostic and longitudinal studies to understand the potential of ALI and PKDL as reservoirs of infection.

The role of asymptomatic Leishmania infection (ALI), PKDL and VL relapse in transmission is unclear as VL elimination is achieved in the Indian subcontinent. ALI, PKDL and relapse studies lacked a reference standard and appropriate biomarker. ALI was 4–17-fold more prevalent than VL. The risk of ALI was higher in VL case contacts. Most infections remained asymptomatic or resolved spontaneously. The natural history of PKDL showed variability. Twenty nine percent had no past history of VL treatment. The risk of VL relapse was higher with HIV co-infection. Modelling studies predicted different effects. Early diagnosis was unlikely to eliminate VL in the long term. ALI was predicted to contribute to 82% of the overall transmission, VL to 10% and PKDL to 8%. Another model predicted that VL cases were the main driver for transmission. VL elimination was predicted if the sandfly density was reduced by 67% by killing the sandfly or by 79% by reducing their breeding sites, or with 4–6y of optimal IRS or 10y of sub-optimal IRS and only in low endemic setting. There is a need for more studies to fully understand the potential of ALI and PKDL as reservoirs of infection.

Antitrypanosomal activity of 5-nitro-2-aminothiazole-based compounds

A small series of 5-nitro-2-aminothiazole-based amides containing arylpiperazine-, biphenyl- or aryloxyphenyl groups in their core were synthesized and evaluated as antitrypanosomatid agents. All tested compounds were active or moderately active against Trypanosoma cruzi amastigotes in infected L6 cells and Trypanosoma brucei brucei, four of eleven compounds were moderately active against Leishmania donovani axenic parasites while none were deemed active against T. brucei rhodesiense. For the most active/moderately active compounds a moderate selectivity against each parasite was observed. There was good correlation between lipophilicity (clogP value) and antileishmanial activity or toxicity against L6 cells. Similarly, good correlation existed between clogP values and IC50 values against T. cruzi in structurally related subgroups of compounds. Three compounds were more potent as antichagasic agents than benznidazole but were not activated by the type I nitrorectusase (NTR).

Drug resistance in eukaryotic microorganisms

Eukaryotic microbial pathogens are major contributors to illness and death globally. Although much of their impact can be controlled by drug therapy as with prokaryotic microorganisms, the emergence of drug resistance has threatened these treatment efforts. Here, we discuss the challenges posed by eukaryotic microbial pathogens and how these are similar to, or differ from, the challenges of prokaryotic antibiotic resistance. The therapies used for several major eukaryotic microorganisms are then detailed, and the mechanisms that they have evolved to overcome these therapies are described. The rapid emergence of resistance and the restricted pipeline of new drug therapies pose considerable risks to global health and are particularly acute in the developing world. Nonetheless, we detail how the integration of new technology, biological understanding, epidemiology and evolutionary analysis can help sustain existing therapies, anticipate the emergence of resistance or optimize the deployment of new therapies.

Serial use of pentamidine and miltefosine for treating Leishmania infantum-HIV coinfection

Liposomal amphotericin B (LAmb) may fail to heal Leishmania infantum visceral leishmaniasis (VL) in the immunodeficient host. There are currently no guidelines on how to treat such patients and efficacy of miltefosine monotherapy seems limited in this indication. We present 2 cases of patients with VL and AIDS for which LAmb had to be interrupted (one because of toxicity, one because of treatment failure) and who were treated effectively with pentamidine followed by miltefosine.

Genomic Appraisal of the Multifactorial Basis for In Vitro Acquisition of Miltefosine Resistance in Leishmania donovani

Protozoan parasites of the Leishmania donovani complex are the causative agents of visceral leishmaniasis (VL), the most severe form of leishmaniasis, with high rates of mortality if left untreated. Leishmania parasites are transmitted to humans through the bite of infected female sandflies (Diptera: Phlebotominae), and approximately 500,000 new cases of VL are reported each year. In the absence of a safe human vaccine, chemotherapy, along with vector control, is the sole tool with which to fight the disease. Miltefosine (hexadecylphosphatidylcholine [HePC]), an antitumoral drug, is the only successful oral treatment for VL. In the current study, we describe the phenotypic traits of L. donovani clonal lines that have acquired resistance to HePC. We performed whole-genome and RNA sequencing of these resistant lines to provide an inclusive overview of the multifactorial acquisition of experimental HePC resistance, circumventing the challenge of identifying changes in membrane-bound proteins faced by proteomics. This analysis was complemented by assessment of the in vitro infectivity of HePC-resistant parasites. Our work underscores the importance of complementary "omics" to acquire the most comprehensive insight for multifaceted processes, such as HePC resistance.

Visceral leishmaniasis: a forgotten epidemic

Visceral leishmaniasis (VL or kala-azar) is most endemic in Asia and Africa and commonly affects young children. It is usually caused by Leishmania donovani or Leishmania infantum that are transmitted by Phlebotomine sand flies. Transmission may be anthroponotic or zoonotic or both, depending on the endemic area. Clinical features include fever, hepatosplenomegaly, weight loss and pancytopenia. Younger age, malnutrition and immunosuppression (HIV infection, use of immunosuppressive drugs) are risk factors. Many infections remain asymptomatic. Diagnosis is made by demonstration of the Leishmania parasite in aspirates of lymph node, bone marrow or spleen. Serological tests such as rK39 strip test are widely used but the sensitivity varies. qPCR is useful to detect low numbers of parasites and to monitor treatment. Treatment is with AmBisome monotherapy in most areas but with drug combinations elsewhere. HIV co-infected patients are most difficult to treat and often relapse. Control efforts focus on case finding, availability of diagnostic tools, reservoir control and protection from sand flies (insecticides, bed nets). There is no human vaccine.

Genomic and Molecular Characterization of Miltefosine Resistance in Leishmania infantum Strains with Either Natural or Acquired Resistance through Experimental Selection of Intracellular Amastigotes

During the last decade miltefosine (MIL) has been used as first-line treatment for visceral leishmaniasis in endemic areas with antimonial resistance, but a decline in clinical effectiveness is now being reported. While only two MIL-resistant Leishmania infantum strains from HIV co-infected patients have been documented, phenotypic MIL-resistance for L. donovani has not yet been identified in the laboratory. Hence, a better understanding of the factors contributing to increased MIL-treatment failure is necessary. Given the paucity of defined MIL-resistant L. donovani clinical isolates, this study used an experimental amastigote-selected MIL-resistant L. infantum isolate (LEM3323). In-depth exploration of the MIL-resistant phenotype was performed by coupling genomic with phenotypic data to gain insight into gene function and the mutant phenotype. A naturally MIL-resistant L. infantum clinical isolate (LEM5159) was included to compare both datasets. Phenotypically, resistance was evaluated by determining intracellular amastigote susceptibility in vitro and actual MIL-uptake. Genomic analysis provided supportive evidence that the resistance selection model on intracellular amastigotes can be a good proxy for the in vivo field situation since both resistant strains showed mutations in the same inward transporter system responsible for the acquired MIL-resistant phenotype. In line with previous literature findings in promastigotes, our data confirm a defective import machinery through inactivation of the LiMT/LiRos3 protein complex as the main mechanism for MIL-resistance also in intracellular amastigotes. Whole genome sequencing analysis of LEM3323 revealed a 2 base pair deletion in the LiMT gene that led to the formation an early stop codon and a truncation of the LiMT protein. Interestingly, LEM5159 revealed mutations in both the LiMT and LiRos3 genes, resulting in an aberrant expression of the LiMT protein. To verify that these mutations were indeed accountable for the acquired resistance, transfection experiments were performed to re-establish MIL-susceptibility. In LEM3323, susceptibility was restored upon expression of a LiMT wild-type gene, whereas the MIL-susceptibility of LEM5159 could be reversed after expression of the LiRos3 wild-type gene. The aberrant expression profile of the LiMT protein could be restored upon rescue of the LiRos3 gene both in the LEM5159 clinical isolate and a ΔLiRos3 strain, showing that expression of LdMT is dependent on LdRos3 expression. The present findings clearly corroborate the pivotal role of the LiMT/LiRos3 complex in resistance towards MIL.

Recent developments and future prospects in the treatment of visceral leishmaniasis

Limited therapeutic options in visceral leishmaniasis (VL) make the treatment of this neglected disease very challenging. In addition to this, long treatment duration and toxic adverse effects make it even more difficult. With no effective vaccine available to date, treatment of VL is based only on chemotherapy. In the Indian subcontinent, a single dose of liposomal amphotericin B (L-AmB) and multidrug therapy (L-AmB + miltefosine, L-AmB + paromomycin [PM], or miltefosine + PM) are the treatments of choice for VL. In East Africa, however, combination therapy of pentavalent antimonials (Sb(v)) and PM remains the treatment of choice, and in the Mediterranean region and South America, L-AmB is the recommended drug. Fexinidazole and PA-824 are new promising drugs which have shown encouraging results in preclinical studies.

Evidence of a drug-specific impact of experimentally selected paromomycin and miltefosine resistance on parasite fitness in Leishmania infantum

OBJECTIVES

Although miltefosine and paromomycin were only recently introduced to treat visceral leishmaniasis, increasing numbers of miltefosine treatment failures and occasional primary resistance to both drugs have been reported. Understanding alterations in parasite behaviour linked to drug resistance is essential to assess the propensity for emergence and spread of resistant strains, particularly since a positive effect on fitness has been reported for antimony-resistant parasites. This laboratory study compared the fitness of a drug-susceptible parent WT clinical Leishmania infantum isolate (MHOM/FR/96/LEM3323) and derived miltefosine and paromomycin drug-resistant lines that were experimentally selected at the intracellular amastigote level.

METHODS

Parasite fitness of WT, paromomycin-resistant and miltefosine-resistant strains, in vitro and in vivo parasite growth, metacyclogenesis, infectivity and macrophage stress responses were comparatively evaluated.

RESULTS

No significant differences in promastigote fitness were noted between the WT and paromomycin-resistant strain, while clear benefits could be demonstrated for paromomycin-resistant amastigotes in terms of enhanced in vitro and in vivo growth potential and intracellular stress response. The miltefosine-resistant phenotype showed incomplete promastigote metacyclogenesis, decreased intracellular growth and weakened stress response, revealing a reduced fitness compared with WT parent parasites.

CONCLUSIONS

The rapid selection and fitness advantages of paromomycin-resistant amastigotes endorse the current use of paromomycin in combination therapy. Although a reduced fitness of miltefosine-resistant strains may explain the difficulty of miltefosine resistance selection in vitro, the growing number of miltefosine treatment failures in the field still requires further exploratory research.

Evolutionary genomics of epidemic visceral leishmaniasis in the Indian subcontinent

Leishmania donovani causes visceral leishmaniasis (VL), the second most deadly vector-borne parasitic disease. A recent epidemic in the Indian subcontinent (ISC) caused up to 80% of global VL and over 30,000 deaths per year. Resistance against antimonial drugs has probably been a contributing factor in the persistence of this epidemic. Here we use whole genome sequences from 204 clinical isolates to track the evolution and epidemiology of L. donovani from the ISC. We identify independent radiations that have emerged since a bottleneck coincident with 1960s DDT spraying campaigns. A genetically distinct population frequently resistant to antimonials has a two base-pair insertion in the aquaglyceroporin gene LdAQP1 that prevents the transport of trivalent antimonials. We find evidence of genetic exchange between ISC populations, and show that the mutation in LdAQP1 has spread by recombination. Our results reveal the complexity of L. donovani evolution in the ISC in response to drug treatment.

DOI:http://dx.doi.org/10.7554/eLife.12613.001

The parasite Leishmania donovani causes a disease called visceral leishmaniasis that affects many of the world's poorest people. Around half a million new cases develop every year, but health authorities lack safe and effective drugs to treat them. Up to 80% of these cases occur in the Indian subcontinent, where devastating epidemics have occurred in the last decades.

One reason these epidemics continue to occur is that the parasites develop genetic mutations allowing them to adapt to and resist the drugs used to kill them. As there are few existing drugs that can kill L. donovani, it is crucial to understand how drug resistance emerges and spreads among parasite populations.

Imamura, Downing, Van den Broeck et al. have now investigated the history of visceral leishmaniasis epidemics by characterising the complete genetic sequence – or genome – of 204 L. donovani parasite samples. This revealed that the majority of parasites in the Indian subcontinent first appeared in the nineteenth century, matching the first historical records of visceral leishmaniasis epidemics.

The genomes show that most of the parasites are genetically similar and can be clustered into several closely related groups. These groups first appeared in the 1960s following the end of a regional campaign to eradicate malaria. The most common parasite group is particularly resistant to drugs called antimonials, which were the main treatment for leishmaniasis until recently. These parasites have a small genetic change that scrambles most of a protein known to be involved in the uptake of antimonials.

Parasites may also be able to develop resistance to drugs through additional mechanisms that allow them to produce many copies of the same gene. These mechanisms could allow the parasites to rapidly adapt to new drugs or changes in the populations it infects. The work of Imamura et al. looks only at parasites isolated from patients then grown in the laboratory, so further research is now needed to explore how variable the Leishmania genome is in both of the parasite’s hosts: humans and sandflies.

Imamura et al.’s study reveals how L. donovani has spread throughout the Indian subcontinent in fine detail. The genome data can be used to create simple molecular tools that could form an "early warning system" to track the success of disease control programs and to determine how well the current drugs are working.

DOI:http://dx.doi.org/10.7554/eLife.12613.002

Current challenges in treatment options for visceral leishmaniasis in India: a public health perspective

Visceral leishmaniasis (VL) is a serious parasitic disease causing considerable mortality and major disability in the Indian subcontinent. It is most neglected tropical disease, particularly in terms of new drug development for the lack of financial returns. An elimination campaign has been running in India since 2005 that aim to reduce the incidence of VL to below 1 per 10,000 people at sub-district level. One of the major components in this endeavor is reducing transmission through early case detection followed by complete treatment. Substantial progress has been made during the recent years in the area of VL treatment, and the VL elimination initiatives have already saved many lives by deploying them effectively in the endemic areas. However, many challenges remain to be overcome including availability of drugs, cost of treatment (drugs and hospitalization), efficacy, adverse effects, and growing parasite resistance. Therefore, better emphasis on implementation research is urgently needed to determine how best to deliver existing interventions with available anti-leishmanial drugs. It is essential that the new treatment options become truly accessible, not simply available in endemic areas so that they may promote healing and save lives. In this review, we highlight the recent advancement and challenges in current treatment options for VL in disease endemic area, and discuss the possible strategies to improve the therapeutic outcome.

Visceral leishmaniasis: Revisiting current treatments and approaches for future discoveries

The current treatments for visceral leishmaniasis are old and toxic with limited routes of administration. The emergence of drug-resistant Leishmania threatens the efficacy of the existing reservoir of antileishmanials, leading to an urgent need to develop new treatments. It is particularly important to review and understand how the current treatments act against Leishmania in order to identify valid drug targets or essential pathways for next-generation antileishmanials. It is equally important to adapt newly emerging biotechnologies to facilitate the current research on the development of novel antileishmanials in an efficient fashion. This review covers the basic background of the current visceral leishmaniasis treatments with an emphasis on the modes of action. It briefly discusses the role of the immune system in aiding the chemotherapy of leishmaniasis, describes potential new antileishmanial drug targets and pathways, and introduces recent progress on the utilization of high-throughput phenotypic screening assays to identify novel antileishmanial compounds.

In vitro selection of miltefosine resistance in promastigotes of Leishmania donovani from Nepal: genomic and metabolomic characterization

In this study, we followed the genomic, lipidomic and metabolomic changes associated with the selection of miltefosine (MIL) resistance in two clinically derived Leishmania donovani strains with different inherent resistance to antimonial drugs (antimony sensitive strain Sb-S; and antimony resistant Sb-R). MIL-R was easily induced in both strains using the promastigote-stage, but a significant increase in MIL-R in the intracellular amastigote compared to the corresponding wild-type did not occur until promastigotes had adapted to 12.2 μM MIL. A variety of common and strain-specific genetic changes were discovered in MIL-adapted parasites, including deletions at the LdMT transporter gene, single-base mutations and changes in somy. The most obvious lipid changes in MIL-R promastigotes occurred to phosphatidylcholines and lysophosphatidylcholines and results indicate that the Kennedy pathway is involved in MIL resistance. The inherent Sb resistance of the parasite had an impact on the changes that occurred in MIL-R parasites, with more genetic changes occurring in Sb-R compared with Sb-S parasites. Initial interpretation of the changes identified in this study does not support synergies with Sb-R in the mechanisms of MIL resistance, though this requires an enhanced understanding of the parasite's biochemical pathways and how they are genetically regulated to be verified fully.

Oleanolic acid (OA) as an antileishmanial agent: Biological evaluation and in silico mechanistic insights

Although a worldwide health problem, leishmaniasis is considered a highly neglected disease, lacking efficient and low toxic treatment. The efforts for new drug development are based on alternatives such as new uses for well-known drugs, in silico and synthetic studies and naturally derived compounds. Oleanolic acid (OA) is a pentacyclic triterpenoid widely distributed throughout the Plantae kingdom that displays several pharmacological activities. OA showed potent leishmancidal effects in different Leishmania species, both against promastigotes (IC(50 L. braziliensis) 30.47 ± 6.35 μM; IC(50 L. amazonensis) 40.46 ± 14.21 μM; IC(50 L. infantum) 65.93 ± 15.12 μM) and amastigotes (IC(50 L. braziliensis) 68.75 ± 16.55 μM; IC(50 L. amazonensis) 38.45 ± 12.05 μM; IC(50 L. infantum) 64.08 ± 23.52 μM), with low cytotoxicity against mouse peritoneal macrophages (CC(50) 235.80 ± 36.95 μM). Moreover, in silico studies performed to evaluate OA molecular properties and to elucidate the possible mechanism of action over the Leishmania enzyme sterol 14α-demethylase (CYP51) suggested that OA interacts efficiently with CYP51 and could inhibit the ergosterol synthesis pathway. Collectively, these data indicate that OA is a good candidate as leading compound for the development of a new leishmaniasis treatment.

Clinico-epidemiological analysis of Post kala-azar dermal leishmaniasis (PKDL) cases in India over last two decades: a hospital based retrospective study

Background

Patients with Post kala-azar dermal leishmaniasis (PKDL) are considered a reservoir of Leishmania donovani. It is imperative to identify and treat them early for control of visceral leishmaniasis (VL), a current priority in the Indian subcontinent. We explored trends in clinico-epidemiological features of PKDL cases over last two decades, for improving management of the disease.

Methods

Clinically suspected cases were diagnosed with rK39 strip test followed by parasitological confirmation by microscopy and/or PCR/qPCR in skin tissue/slit aspirates. Patients were treated with antimonials till 2008 and subsequently with miltefosine.

Results

The study indicated higher incidence of PKDL cases in areas of high endemicity for VL, with 20 % cases reporting no history of VL. Approximately 26 % cases of PKDL were initially misdiagnosed at primary health centers. Duration between onset of PKDL and diagnosis was above 12 months in 80 % cases. Diagnostic sensitivity was 32-36 % with microscopy and 96–100 % with PCR/qPCR. Compliance to treatment was over 85 % with miltefosine while 15 % with antimonials. Relapse rate with miltefosine was up to 13.2 %.

Conclusions

PKDL patients tend to delay reporting and are often misdiagnosed. Confirmatory diagnosis using minimally invasive skin slit aspirate samples would help overcome such issues. There was a paradigm shift in compliance with miltefosine; however, increasing relapse rate indicated the need for newer therapies with oral formulations.

Decline in Clinical Efficacy of Oral Miltefosine in Treatment of Post Kala-azar Dermal Leishmaniasis (PKDL) in India

Background

Recent studies have shown significant decline in the final cure rate after miltefosine treatment in visceral leishmaniasis. This study evaluates the efficacy of miltefosine in the treatment of post kala-azar dermal leishmaniasis (PKDL) patients recruited over a period of 5 years with 18 months of follow-up.

Methodology

In this study 86 confirmed cases of PKDL were treated with two different dosage regimens of miltefosine (Regimen I- 50mg twice daily for 90 days and Regimen II- 50 mg thrice for 60 days) and the clinical outcome assessed monthly. Cure/relapse was ascertained by clinical and histopathological examination, and measuring parasite burden by quantitative real-time PCR. In vitro susceptibility of parasites towards miltefosine was estimated at both promastigote and amastigote stages.

Results

Seventy three of eighty six patients completed the treatment and achieved clinical cure. Approximately 4% (3/73) patients relapsed by the end of 12 months follow-up, while a total of 15% (11/73) relapsed by the end of 18 months. Relapse rate was significantly higher in regimen II (31%) compared to regimen I (10.5%)(P<0.005). Parasite load at the pre-treatment stage was significantly higher (P<0.005) in cases that relapsed compared to the cases that remained cured. In vitro susceptibility towards miltefosine of parasites isolated after relapse was significantly lower (>2 fold) in comparison with the pre-treatment isolates (P<0.005).

Conclusion

Relapse rate in PKDL following miltefosine treatment has increased substantially, indicating the need of introducing alternate drugs/ combination therapy with miltefosine.

Increasing resistance to antimonials has paved the way for the oral drug miltefosine for PKDL treatment. Recent studies show a significant decline in the final cure rate of VL after miltefosine treatment in the Indian subcontinent. This is the first study to evaluate the efficacy of miltefosine treatment in a large number of PKDL cases with 18 months follow-up. PKDL cases that completed miltefosine treatment responded well and showed initial cure; however, with 18 months of follow up period, the final cure rate was only about 85%. Treatment regimen based on high dosage over short duration resulted in high relapse rate. We observed that the parasites isolated from the cases that relapsed were more tolerant to miltefosine (>2 fold) compared to the isolates from pre-treatment stage. Estimation of parasite load at pre-treatment stage indicated that the patients with higher initial parasitic burden were at a higher risk of relapse. The declining efficacy of monotherapy with miltefosine warrants the need of alternate regimens for treatment of PKDL.

3-Nitrotriazole-based piperazides as potent antitrypanosomal agents

Novel linear 3-nitro-1H-1,2,4-triazole-based piperazides were synthesized and evaluated as antitrypanosomal agents. In addition, some bisarylpiperazine-ethanones which were formed as by-products were also screened for antiparasitic activity. Most 3-nitrotriazole-based derivatives were potent and selective against Trypanosoma cruzi parasites, but only one displayed these desired properties against Trypanosoma brucei rhodesiense. Moreover, two 3-nitrotriazole-based chlorophenylpiperazides were moderately and selectively active against Leishmania donovani. Although the bisarylpiperazine-ethanones were active or moderately active against T. cruzi, none of them demonstrated an acceptable selectivity. In general, 3-nitrotriazole-based piperazides were less toxic to host L6 cells than the previously evaluated 3-nitrotriazole-based piperazines and seven of 13 were 1.54- to 31.2-fold more potent antichagasic agents than the reference drug benznidazole. Selected compounds showed good ADMET characteristics. One potent in vitro antichagasic compound (3) was tested in an acute murine model and demonstrated antichagasic activity after a 10-day treatment of 15 mg/kg/day. However, neither compound 3 nor benznidazole showed a statistically significant P value compared to control due to high variability in parasite burden among the untreated animals. Working as prodrugs, 3-nitrotriazole-based piperazides were excellent substrates of trypanosomal type I nitroreductases and constitute a novel class of potentially effective and more affordable antitrypanosomal agents.