Frequency of drug resistance gene amplification in clinical leishmania strains

Ein Update zur Leishmaniose des Hundes: Diagnostik, Therapie und Monitoring

Aufgrund von steigenden Importzahlen von Hunden aus dem Ausland, zunehmendem Reiseverkehr sowie den Veränderungen klimatischer Bedingungen in Europa gewinnen Infektionen mit Leishmania (L.) infantum bei Hunden in Deutschland zunehmend an Bedeutung. Daher sollten auch Hunde aus dem Ausland, die keine klinischen Symptome zeigen, direkt nach Import sowie erneut 6 Monate später auf vektorübertragene Infektionserreger getestet werden. Bei Hunden mit klinischer Symptomatik, die hinweisend auf eine Leishmaniose sind, werden direkte und indirekte Nachweisverfahren sowie eine hämatologische und biochemische Untersuchung unter Einbezug von Serumeiweißelektrophorese sowie Bestimmung des C-reaktiven Proteins empfohlen. Als Leitfaden für die Therapie sowie das Monitoring stehen die LeishVet-Guidelines zur Verfügung. Es stehen leishmanizide und leishmaniostatische Wirkstoffe zur Verfügung, die in first-line, second-line und third-line unterschieden werden. Zur Anpassung der Allopurinol-Dosierung wird der Stufenplan empfohlen. Aufgrund der Veränderung der klimatischen Bedingungen kommt es zu einer Ausbreitung der Habitate von Sandmücken, die als Vektoren der Leishmaniose bekannt sind. Als weitere Infektionsquellen sind Deckakte, transplazentare Infektionen, Bisswunden und Bluttransfusionen beschrieben. Leishmania infantum hat zoonotisches Potential und ist daher auch in Hinblick auf den „One-Health“-Gedanken bedeutend.

Using Q-methodology to understand the perspectives and practical experiences of dermatologists about treatment difficulties of cutaneous leishmaniasis

Background

During the outbreak of cutaneous leishmaniasis in the Kurdistan Region of Iraq that started in 2015, the course of the disease and the treatment were not consistent with the available literature. Physicians, particularly dermatologists, faced challenges with treating the cutaneous leishmaniasis lesions with high rates of treatment failure and resistance to treatment. We used Q-methodology to understand the range and diversities of opinions and the practical experiences of dermatologists about the treatment difficulties of cutaneous leishmaniasis.

Methods

This Q-methodology study was carried out in Erbil, Kurdistan Region of Iraq, and involved 37 dermatologists. A set of 40 statements related to different aspects of difficulties and uncertainties of treating cutaneous leishmaniasis was prepared. The dermatologists were requested to distribute the 40 statements into a scaled grid of nine piles from least agree to most agree. We applied by-person factor analysis using PQMethod 2.35 for the data analysis.

Results

The analysis revealed two different viewpoints about the treatment of cutaneous leishmaniasis and a consensus viewpoint. The first viewpoint emphasized the use of sodium stibogluconate-based combination therapy, concerns with treatment failure, and lack of compliance with the treatment. The second viewpoint emphasized the lack of standard treatment and advances in the treatment of cutaneous leishmaniasis. There was a consensus between both groups of respondents about many aspects of the treatment of cutaneous leishmaniasis, including considering sodium stibogluconate the first drug of choice for cutaneous leishmaniasis treatment.

Conclusions

This study revealed a diversity of viewpoints and uncertainties about the effectiveness of the available treatment modalities and treatment difficulties and failure. Interrupted supply and poor quality of the available drugs and lack of a standard and advanced treatment are the main problems facing the treatment of cutaneous leishmaniasis. More research is required to determine the best treatment modalities for the different types of cutaneous leishmaniasis. There is a need for the development of treatment guidelines specific to the Iraqi context with a particular focus on the treatment of the resistant and atypical cases of cutaneous leishmaniasis.

Targeting pteridine reductase 1 and dihydrofolate reductase: the old is a new trend for leishmaniasis drug discovery

Leishmaniasis is one of the major neglected tropical diseases in the world and it is considered endemic in 88 countries. This disease is transmitted by a Leishmania spp. infected sandfly and it may lead to cutaneous or systemic manifestations. The preconized treatment has low efficacy and there are cases of resistance to some drugs. Therefore, the search for new efficient molecular targets that can lead to the preparation of new drugs must be pursued. This review aims to evaluate both Leishmania enzymes PTR1 and DHFR-TS as potential drug targets, highlight their inhibitors and to discuss critically the use of chemoinformatics to elucidate interactions and propose new molecules against these enzymes.

Effectiveness of the sesquiterpene (-)-α-bisabolol in dogs with naturally acquired canine leishmaniosis: an exploratory clinical trial

The use of natural products is a promising approach for treating visceral leishmaniosis. (-)-α-Bisabolol is a sesquiterpene that have been proved active in vivo on Leishmania infantum-infected mice without showing toxicity. A single-centre, parallel-group, randomized, exploratory study was designed to assess its efficacy in a canine leishmaniosis model involving naturally infected dogs. In this clinical trial, 12 dogs were allocated into two groups and were treated with either meglumine antimoniate (100 mg/kg) through subcutaneous route or (-)-α-bisabolol (30 mg/kg) through oral route for two treatment series of 30 days, separated by a 30-day interval. A 4-month follow-up period was established as well. Parasite loads in bone marrow, lymph node and blood were estimated through quantitative PCR. Antibody titres were determined through immunofluorescence antibody test and cytokine expression values were estimated through real-time reverse transcription-PCR. Treatment safety was assessed through the evaluation of weight, gastrointestinal alterations and hematological and biochemical parameters in blood. Analyses were performed before and after treatment, and after a 4-months follow-up period. Treatment with the sesquiterpene was effective at decreasing parasite loads and increasing gamma-interferon expression level. Dogs treated with (-)-α-bisabolol did not show any toxicity sign. These results were better than those obtained using the reference drug, meglumine antimoniate. The natural compound seemed to induce a Th1 immune response that led to parasitological and clinical improvement without showing any safety issue, suggesting a high potential for the treatment of canine and human visceral leishmaniosis.

Genome wide comparison of Ethiopian Leishmania donovani strains reveals differences potentially related to parasite survival

Leishmania donovani is the main cause of visceral leishmaniasis (VL) in East Africa. Differences between northern Ethiopia/Sudan (NE) and southern Ethiopia (SE) in ecology, vectors, and patient sensitivity to drug treatment have been described, however the relationship between differences in parasite genotype between these two foci and phenotype is unknown. Whole genomic sequencing (WGS) was carried out for 41 L. donovani strains and clones from VL and VL/HIV co-infected patients in NE (n = 28) and SE (n = 13). Chromosome aneuploidy was observed in all parasites examined with each isolate exhibiting a unique karyotype. Differences in chromosome ploidy or karyotype were not correlated with the geographic origin of the parasites. However, correlation between single nucleotide polymorphism (SNP) and geographic origin was seen for 38/41 isolates, separating the NE and SE parasites into two large groups. SNP restricted to NE and SE groups were associated with genes involved in viability and parasite resistance to drugs. Unique copy number variation (CNV) were also associated with NE and SE parasites, respectively. One striking example is the folate transporter (FT) family genes (LdBPK_100390, LdBPK_100400 and LdBPK_100410) on chromosome 10 that are single copy in all 13 SE isolates, but either double copy or higher in 39/41 NE isolates (copy number 2-4). High copy number (= 4) was also found for one Sudanese strain examined. This was confirmed by quantitative polymerase chain reaction for LdBPK_100400, the L. donovani FT1 transporter homolog. Good correlation (p = 0.005) between FT copy number and resistance to methotrexate (0.5 mg/ml MTX) was also observed with the haploid SE strains examined showing higher viability than the NE strains at this concentration. Our results emphasize the advantages of whole genome analysis to shed light on vital parasite processes in Leishmania.

Treatment Outcome of the Drug-resistant Zoonotic Cutaneous Leishmaniasis by Glucantime

BACKGROUND

Resistance of Leishmania species to antimonial drugs has increased. Hence, in the present study Leishmania major isolates were collected from patients with resistance phenotype and the presence/absence of resistance to Glucantime was investigated.

MATERIALS AND METHODS

Samples were taken from 10 cutaneous leishmaniasis (CL) patients who had not responded to chemotherapy with Glucantime. Nested polymerase chain reaction (PCR) was performed to identify the isolated species. Stationary phase promastigotes were added to the grown, adhesive J774 macrophages. Values obtained from standard strain were compared with the test cultures after exposure to the medicine. In vivo, the effects of Glucantime were assessed by comparing the sizes and the parasite burden of the lesions on mouse model.

RESULTS

The results of amplified band on agarose gel demonstrated all samples were L. major. After exposure to medicine, a reduction of intracellular amastigotes to half was detected. In vivo, the parasite was eliminated in 90% of mice with lesions caused by both isolates of patients and standard L. major, and their lesions became smaller significantly.

CONCLUSION

Pentavalent antimonial (SbV) salts are the main component of chemotherapy against leishmaniasis. However, the medicine has been found ineffective. In the present study, isolates from patients with no response to treatment had no significant difference from the standard L. major strain (as the sensitive strain). Therefore, in patients with resistance phenotype to Glucantime, the parasites did not actually have intrinsic resistance, i.e., environmental and host factors prevented the successful treatment of the disease.

Geographical Distribution of MDR1 Expression in Leishmania Isolates, from Greece and Cyprus, Measured by the Rhodamine-123 Efflux Potential of the Isolates, Using Flow Cytometry

Leishmaniasis, a neglected vector-borne disease caused by the protozoan parasite Leishmania, is encountered in 98 countries causing serious concerns to public health. The most alarming is the development of parasite drug resistance, a phenomenon increasingly encountered in the field rendering chemotherapy ineffective. Although resistance to drugs is a complex phenomenon, the rate of efflux of the fluorescent dye Rhodamine-123 from the parasite body, using flow cytometry, is an indication of the isolate's ability to efflux the drug, thus avoiding death. The rate of efflux measured 275 Leishmania strains, isolated from patients and dogs from Greece and Cyprus, was measured and mapped to study the geographical distribution of the multidrug resistance (MDR) gene expression as an indication of the drug resistance of the parasite. The map showed that out of the seven prefectures, where dogs presented high efflux rates, five also had patients with high efflux rates. In one, out of the 59 prefectures studied, the highest number of isolates with efflux slope α > 1, in both human and dog isolates, was found; a fact which may suggest that spread of drug resistance is taking place. The virulence of the Leishmania strains, assessed after infecting human macrophages of the THP-1 cell line, fluctuated from 1% to 59.3% with only 2.5% of the isolates showing infectivity > 50%. The most virulent strains were isolated from Attica and Crete.

P-glycoprotein A Gene Expression in Glucantime-Resistant and Sensitive Leishmania major (MRHO/IR/75/ER)

BACKGROUND

Leishmaniasis is a parasitic disease caused by different species of Leishmania parasites with a wide range of clinical manifestations. Antimonial compounds such as meglumine antimoniate (glucantime) are the first line drugs for the treatment of leishmaniasis. However, according to reports of the drug resistance of parasites, the efficacy of antimonial compounds is low. The ATP-binding cassette (ABC) proteins are present in all organisms and mediate the transport of vital elements through biological membranes. One of the important mechanisms of resistance in Leishmania parasites is the overexpression of ABC efflux pumps. P-glycoprotein A (pgpA) is a related gene for ABC transporter in Leishmania species. The aim of this study was to compare the pgpA expression in laboratory-induced resistant L. major (MRHO/IR/75/ER) and sensitive parasites.

METHODS

RNA extraction of promastigotes of sensitive and resistant clones was performed and total RNA was reverse transcribed. The real-time quantitative polymerase chain reaction (PCR) was used to assess RNA expression profiles and the expression levels were calculated using 2(-ΔCt) method.

RESULTS

The mean expression level of pgpA mRNA was 2.70 ± 0.51 in in sensitive Leishmania clone and 6.08 ± 1.50 in resistant Leishmania clone (P = 0.021).

CONCLUSION

The expression of pgpA gene in resistant strains of L. major was almost fivefold higher than those in susceptible strains. Therefore, this can be used in field isolates, i.e. overexpression of the gene can prove resistance in wild type field isolates.

Heterogeneity of molecular resistance patterns in antimony-resistant field isolates of Leishmania species from the western Mediterranean area

Antimonials remain the first-line treatment for the various manifestations of leishmaniasis in most areas where the disease is endemic, and increasing cases of therapeutic failure associated with parasite resistance have been reported. In this study, we assessed the molecular status of 47 clinical isolates of Leishmania causing visceral and cutaneous leishmaniasis from Algeria, Tunisia, and southern France. In total, we examined 14 genes that have been shown to exhibit significant variations in DNA amplification, mRNA levels, or protein expression with respect to resistance to antimonials. The gene status of each clinical isolate was assessed via qPCR and qRT-PCR. We then compared the molecular pattern against the phenotype determined via an in vitro sensitivity test of the clinical isolates against meglumine antimoniate, which is considered the reference technique. Our results demonstrate significant DNA amplification and/or RNA overexpression in 56% of the clinical isolates with the resistant phenotype. All clinical isolates that exhibited significant overexpression of at least 2 genes displayed a resistant phenotype. Among the 14 genes investigated, 10 genes displayed either significant amplification or overexpression in at least 1 clinical isolate; these genes are involved in several metabolic pathways. Moreover, various gene associations were observed depending on the clinical isolates, supporting the multifactorial nature of Leishmania resistance. Molecular resistance features were found in the 3 Leishmania species investigated (Leishmania infantum, Leishmania major, and Leishmania killicki). To our knowledge, this is the first report of the involvement of molecular resistance genes in field isolates of Leishmania major and Leishmania killicki with the resistance phenotype.

Frequency of MDR1-related p-gp overexpression in Greek Leishmania isolates

In this work, we investigated Greek Leishmania isolates (n = 70) for their individual MDR1-gene-related p-gp (belonging to the ABC-B subfamily of permeases) expression levels by means of flow cytometric analysis of Rhodamine 123 extrusion kinetics. Of all used isolates, 5.71% express this drug-extruding ABC-transporter at alarming levels and are distributed widely over the country. Some 33% of all examined isolates originated on the island of Crete though none of the strains showed vastly elevated p-gp extrusion activity, indicating a reasonable implementation of anti-leishmanial compounds in this part of the country. Compared to isolates obtained from canine tissue, human Leishmania isolates were superior both in size and in subcellular differentiation in flow cytometry. Furthermore, a specific t test confirmed verapamil hydrochloride to be a highly potent p-gp reversal agent with p < 0.0001. In a second test series, the loading of Leishmania with Rhodamine 123 was moreover reduced when occurring under influence of verapamil hydrochloride, a known p-gp reversal agent, indicating an ATP-dependant influx of the fluorescent dye and therewith the drug itself. In a final, third experiment series, it was shown that Sb(V) does not act upon the promastigote form of Leishmania.

Application of the NucliSENS easyMAG system for nucleic acid extraction: optimization of DNA extraction for molecular diagnosis of parasitic and fungal diseases

During the last 20 years, molecular biology techniques have propelled the diagnosis of parasitic diseases into a new era, as regards assay speed, sensitivity, and parasite characterization. However, DNA extraction remains a critical step and should be adapted for diagnostic and epidemiological studies. The aim of this report was to document the constraints associated with DNA extraction for the diagnosis of parasitic diseases and illustrate the adaptation of an automated extraction system, NucliSENS easyMAG, to these constraints, with a critical analysis of system performance. Proteinase K digestion of samples is unnecessary with the exception of solid tissue preparation. Mechanically grinding samples prior to cell lysis enhances the DNA extraction rate of fungal cells. The effect of host-derived nucleic acids on the extraction efficiency of parasite DNA varies with sample host cell density. The optimal cell number for precise parasite quantification ranges from 10 to 100,000 cells. Using the NucliSENS easyMAG technique, the co-extraction of inhibitors is reduced, with an exception for whole blood, which requires supplementary extraction steps to eliminate inhibitors.

Role of efflux pumps and intracellular thiols in natural antimony resistant isolates of Leishmania donovani

BACKGROUND

In view of the recent upsurge in the phenomenon of therapeutic failure, drug resistance in Leishmania, developed under natural field conditions, has become a great concern yet little understood. Accordingly, the study of determinants of antimony resistance is urgently warranted. Efflux transporters have been reported in Leishmania but their role in clinical resistance is still unknown. The present study was designed to elucidate the mechanism of natural antimony resistance in L. donovani field isolates by analyzing the functionality of efflux pump(s) and expression profiles of known genes involved in transport and thiol based redox metabolism.

METHODOLOGY/PRINCIPAL FINDINGS

We selected 7 clinical isolates (2 sensitive and 5 resistant) in addition to laboratory sensitive reference and SbIII resistant mutant strains for the present study. Functional characterization using flow cytometry identified efflux pumps that transported substrates of both P-gp and MRPA and were inhibited by the calmodulin antagonist trifluoperazine. For the first time, verapamil sensitive efflux pumps for rhodamine 123 were observed in L. donovani that were differentially active in resistant isolates. RT-PCR confirmed the over-expression of MRPA in isolates with high resistance index only. Resistant isolates also exhibited consistent down regulation of AQP1 and elevated intracellular thiol levels which were accompanied with increased expression of ODC and TR genes. Interestingly, γ-GCS is not implicated in clinical resistance in L. donovani isolates.

CONCLUSIONS/SIGNIFICANCE

Here we demonstrate for the first time, the role of P-gp type plasma membrane efflux transporter(s) in antimony resistance in L. donovani field isolates. Further, decreased levels of AQP1 and elevated thiols levels have emerged as biomarkers for clinical resistance.

Drug resistance in natural isolates of Leishmania donovani s.l. promastigotes is dependent of Pgp170 expression

Resistance of pathogens to drugs is a growing concern regarding many diseases. Parasites like Leishmania, Plasmodium and Entamoeba histolytica; and neoplastic cells, present the multidrug-resistant phenotype rendering chemotherapy ineffective. The acquired resistance of Leishmania to antimony has generated intense research on the mechanisms involved but the question has not yet been resolved. To test the hypothesis that drug efflux in Leishmania, as measured by flow cytometry using the fluorescent dye Rhodamine-123, is largely dependent on the number of efflux pumps an isolate can express, the amount of Pgp 170 molecules was assessed in ten field isolates (5 “resistant” and 5 “susceptible”) using: Western Blotting, Confocal and Transmission Electron Microscopy, and proteomics. Their survival after exposure to three antileishmanial drugs, in vitro, was evaluated and clinical data were compared to the in vitro results. All isolates were resistant to Glucantime but susceptible to Miltefosine, whilst Amphotericin B was more effective on the “susceptible” isolates. The MDR gene, expressing the transmembrane efflux pump Pgp 170, appears to play a key role in the phenomenon of drug resistance. When “susceptible” versus “resistant” parasites were compared, it was shown that the higher the number of Pgp 170 molecules the higher the Rhodamine-123 efflux from the parasite body and, when exposed to the drug, the number of efflux pumps increased. However, the rate of this increase was not linear and it is possible that there is a maximum number of Pgp 170 molecules an isolate can express. Nevertheless, the phenomenon is a complex one and other factors and proteins are involved in which the HSP-70 group proteins, detected in the “resistant” isolates, may play a significant role.

Gene duplication as a mechanism of genomic adaptation to a changing environment

A subject of extensive study in evolutionary theory has been the issue of how neutral, redundant copies can be maintained in the genome for long periods of time. Concurrently, examples of adaptive gene duplications to various environmental conditions in different species have been described. At this point, it is too early to tell whether or not a substantial fraction of gene copies have initially achieved fixation by positive selection for increased dosage. Nevertheless, enough examples have accumulated in the literature that such a possibility should be considered. Here, I review the recent examples of adaptive gene duplications and make an attempt to draw generalizations on what types of genes may be particularly prone to be selected for under certain environmental conditions. The identification of copy-number variation in ecological field studies of species adapting to stressful or novel environmental conditions may improve our understanding of gene duplications as a mechanism of adaptation and its relevance to the long-term persistence of gene duplications.

Antimony resistance in leishmania, focusing on experimental research

Leishmaniases are parasitic diseases that spread in many countries with a prevalence of 12 million cases. There are few available treatments and antimonials are still of major importance in the therapeutic strategies used in most endemic regions. However, resistance toward these compounds has recently emerged in areas where the replacement of these drugs is mainly limited by the cost of alternative molecules. In this paper, we reviewed the studies carried out on antimonial resistance in Leishmania. Several common limitations of these works are presented before prevalent approaches to evidence antimonial resistance are related. Afterwards, phenotypic determination of resistance is described, then confronted to clinical outcome. Finally, we detail molecular mechanisms and targets involved in resistance and already identified in vitro within selected mutant strains or in clinical isolates.