The Synthesis of 2'-Hydroxychalcones under Ball Mill Conditions and Their Biological Activities.

Chalcones are polyphenols that belong to the flavonoids family, known for their broad pharmacological properties. They have thus attracted the attention of chemists for their obtention and potential activities. In our study, a library of compounds from 2'-hydroxychalcone's family was first synthesized. A one-step mechanochemical synthesis via Claisen-Schmidt condensation reaction under ball mill conditions was studied, first in a model reaction between a 5'-fluoro-2'-hydroxyacetophenone and 3,4-dimethoxybenzaldehyde. The reaction was optimized in terms of catalysts, ratio of reagents, reaction time, and influence of additives. Among all assays, we retained the best one, which gave the highest yield of 96% when operating in the presence of 1 + 1 eq. of substituted benzaldehyde and 2 eq. of KOH under two grinding cycles of 30 min. Thus, this protocol was adopted for the synthesis of the selected library of 2'-hydroxychalcones derivatives. The biological activities of 17 compounds were then assessed against Plasmodium falciparum, Leishmania donovani parasite development, as well as IGR-39 melanoma cell lines by inhibiting their viability and proliferation. Compounds 6 and 11 are the most potent against L. donovani, exhibiting IC50 values of 2.33 µM and 2.82 µM, respectively, better than the reference drug Miltefosine (3.66 µM). Compound 15 presented the most interesting antimalarial activity against the 3D7 strain, with IC50 = 3.21 µM. Finally, chalcone 12 gave the best result against IGR-39 melanoma cell lines, with an IC50 value of 12 µM better than the reference drug Dacarbazine (IC50 = 25 µM).

Chemoselective Synthesis and Anti-Kinetoplastidal Properties of 2,6-Diaryl-4H-tetrahydro-thiopyran-4-one S-Oxides: Their Interplay in a Cascade of Redox Reactions from Diarylideneacetones.

2,6-Diaryl-4H-tetrahydro-thiopyran-4-ones and corresponding sulfoxide and sulfone derivatives were designed to lower the major toxicity of their parent anti-kinetoplatidal diarylideneacetones through a prodrug effect. Novel diastereoselective methodologies were developed and generalized from diarylideneacetones and 2,6-diaryl-4H-tetrahydro-thiopyran-4-ones to allow the introduction of a wide substitution profile and to prepare the related S-oxides. The in vitro biological activity and selectivity of diarylideneacetones, 2,6-diaryl-4H-tetrahydro-thiopyran-4-ones, and their S-sulfoxide and sulfone metabolites were evaluated against Trypanosoma brucei brucei, Trypanosoma cruzi, and various Leishmania species in comparison with their cytotoxicity against human fibroblasts hMRC-5. The data revealed that the sulfides, sulfoxides, and sulfones, in which the Michael acceptor sites are temporarily masked, are less toxic against mammal cells while the anti-trypanosomal potency was maintained against T. b. brucei, T. cruzi, L. infantum, and L. donovani, thus confirming the validity of the prodrug strategy. The mechanism of action is proposed to be due to the involvement of diarylideneacetones in cascades of redox reactions involving the trypanothione system. After Michael addition of the dithiol to the double bonds, resulting in an elongated polymer, the latter-upon S-oxidation, followed by syn-eliminations-fragments, under continuous release of reactive oxygen species and sulfenic/sulfonic species, causing the death of the trypanosomal parasites in the micromolar or submicromolar range with high selectivity indexes.

Mechanochemical Studies on Coupling of Hydrazines and Hydrazine Amides with Phenolic and Furanyl Aldehydes-Hydrazones with Antileishmanial and Antibacterial Activities.

Hydrazone compounds represent an important area of research that includes, among others, synthetic approaches and biological studies. A series of 17 hydrazones have been synthesized by mechanochemical means. The fragments chosen were phenolic and furanyl aldehydes coupled with 12 heterocyclic hydrazines or hydrazinamides. All compounds can be obtained quantitatively when operating on a planetary ball mill and a maximum reaction time of 180 min (6 cycles of 30 min each). Complete spectroscopic analyses of hydrazones revealed eight compounds (3-5, 8-11, 16) present in one geometric form, six compounds (1, 2, 13-15) present in two isomeric forms, and three compounds (6, 7, 12) where one rotation is restricted giving rise to two different forms. The single crystal X-ray structure of one of the hydrazones bearing the isoniazid fragment (8) indicates a crystal lattice consisting of two symmetry-independent molecules with different geometries. All compounds obtained were tested for anti-infectious and antibacterial activities. Four compounds (1, 3, 5 and 8) showed good activity against Mycobacterium tuberculosis, and one (7) was very potent against Staphylococcus aureus. Most interesting, this series of compounds displayed very promising antileishmanial activity. Among all, compound 9 exhibited an IC50 value of 0.3 µM on the Leishmania donovani intramacrophage amastigote in vitro model and a good selectivity index, better than miltefosine, making it worth evaluating in vivo.

Evaluation of two commercial kits and two laboratory-developed qPCR assays compared to LAMP for molecular diagnosis of malaria.

BACKGROUND: Malaria is an infectious disease considered as one of the biggest causes of mortality in endemic areas. This life-threatening disease needs to be quickly diagnosed and treated. The standard diagnostic tools recommended by the World Health Organization are thick blood smears microscopy and immuno-chromatographic rapid diagnostic tests. However, these methods lack sensitivity especially in cases of low parasitaemia and non-falciparum infections. Therefore, the need for more accurate and reliable diagnostic tools, such as real-time polymerase chain reaction based methods which have proven greater sensitivity particularly in the screening of malaria, is prominent. This study was conducted at the French National Malaria Reference Centre to assess sensitivity and specificity of two commercial malaria qPCR kits and two in-house developed qPCRs compared to LAMP. METHODS: 183 blood samples received for expertise at the FNMRC were included in this study and were subjected to four different qPCR methods: the Biosynex Ampliquick® Malaria test, the BioEvolution Plasmodium Typage test, the in-house HRM and the in-house TaqMan qPCRs. The specificity and sensitivity of each method and their confidence intervals were determined with the LAMP-based assay Alethia® Malaria as the reference for malaria diagnosis. The accuracy of species diagnosis of the Ampliquick® Malaria test and the two in-house qPCRs was also evaluated using the BioEvolution Plasmodium Typage test as the reference method for species identification. RESULTS: The main results showed that when compared to LAMP, a test with excellent diagnostic performances, the two in-house developed qPCRs were the most sensitive (sensitivity at 100% for the in-house TaqMan qPCR and 98.1% for the in-house HRM qPCR), followed by the two commercial kits: the Biosynex Ampliquick® Malaria test (sensitivity at 97.2%) and the BioEvolution Plasmodium Typage (sensitivity at 95.4%). Additionally, with the in-house qPCRs we were able to confirm a Plasmodium falciparum infection in microscopically negative samples that were not detected by commercial qPCR kits. This demonstrates that the var genes of P. falciparum used in these in-house qPCRs are more reliable targets than the 18S sRNA commonly used in most of the developed qPCR methods for malaria diagnosis. CONCLUSION: Overall, these results accentuate the role molecular methods could play in the screening of malaria. This may represent a helpful tool for other laboratories looking to implement molecular diagnosis methods in their routine analysis, which could be essential for the detection and treatment of malaria carriers and even for the eradication of this disease.

Biodereplication of Antiplasmodial Extracts: Application of the Amazonian Medicinal Plant Piper coruscans Kunth.

Improved methodological tools to hasten antimalarial drug discovery remain of interest, especially when considering natural products as a source of drug candidates. We propose a biodereplication method combining the classical dereplication approach with the early detection of potential antiplasmodial compounds in crude extracts. Heme binding is used as a surrogate of the antiplasmodial activity and is monitored by mass spectrometry in a biomimetic assay. Molecular networking and automated annotation of targeted mass through data mining were followed by mass-guided compound isolation by taking advantage of the versatility and finely tunable selectivity offered by centrifugal partition chromatography. This biodereplication workflow was applied to an ethanolic extract of the Amazonian medicinal plant Piper coruscans Kunth (Piperaceae) showing an IC50 of 1.36 µg/mL on the 3D7 Plasmodium falciparum strain. It resulted in the isolation of twelve compounds designated as potential antiplasmodial compounds by the biodereplication workflow. Two chalcones, aurentiacin (1) and cardamonin (3), with IC50 values of 2.25 and 5.5 µM, respectively, can be considered to bear the antiplasmodial activity of the extract, with the latter not relying on a heme-binding mechanism. This biodereplication method constitutes a rapid, efficient, and robust technique to identify potential antimalarial compounds in complex extracts such as plant extracts.

An adamantamine derivative as a drug candidate for the treatment of visceral leishmaniasis.

BACKGROUND: This study aimed to investigate compounds acting on the host cell machinery to impair parasite installation with the possible advantage of limiting drug resistance. The strategy therefore consisted of selecting compounds that are poorly active on the axenic parasite, but very active on the intramacrophage form of Leishmania. OBJECTIVES: To identify a drug candidate from focused screening of adamantamine derivatives that can inhibit the development of Leishmania infantum in macrophages. METHODS: In vitro screening was performed on a library of 142 adamantamine derivatives with axenic and intramacrophage forms of L. infantum, as well as cytotoxicity assays, allowing selection of the most promising compound. Absorption, distribution, metabolism and excretion (ADME) experiments, including pharmacokinetics and microsomal stability, were performed and finally the physicochemical stability of the compound was investigated to assess its suitability for further drug development. RESULTS: VP343 was identified first in vitro, with a CC50 value of 63.7 µM and an IC50 value of 0.32 µM for L. infantum intramacrophage amastigotes and then in vivo, with a 59% reduction of the liver parasite burden after oral administration at 10 mg/kg/day for 5 days. In addition, the ADME data were compatible with moving this compound further through the antileishmanial drug candidate pipeline. CONCLUSIONS: VP343 has the properties of a good drug candidate and merits further investigations.

Key role of the macrophage microtubule network in the intracellular lifestyle of Leishmania amazonensis.

We conducted a study to decipher the mechanism of the formation of the large communal Leishmania amazonensis-containing parasitophorous vacuole (PV) and found that the macrophage microtubule (MT) network dynamically orchestrates the intracellular lifestyle of this intracellular parasite. Physical disassembly of the MT network of macrophage-like RAW 264.7 cells or silencing of the dynein gene, encoding the MT-associated molecular motor that powers MT-dependent vacuolar movement, by siRNA resulted in most of the infected cells hosting only tight parasite-containing phagosome-like vacuoles randomly distributed throughout the cytoplasm, each insulating a single parasite. Only a minority of the infected cells hosted both isolated parasite-containing phagosome-like vacuoles and a small communal PV, insulating a maximum of two to three parasites. The tight parasite-containing phagosome-like vacuoles never matured, whereas the small PVs only matured to a small degree, shown by the absence or faint acquisition of host-cell endolysosomal characteristics. As a consequence, the parasites were unable to successfully complete promastigote-to-amastigote differentiation and died, regardless of the type of insulation.

Anti-protozoal and anti-fungal evaluation of 3,5-disubstituted 1,2-dioxolanes.

Endoperoxides are a class of compounds, which is well-known for their antimalarial properties, but few reports exist about 3,5-disubstituted 1,2-dioxolanes. After having designed a new synthetic route for the preparation of these substances, they were evaluated against 4 different agents of infectious diseases, protozoa (Plasmodium and Leishmania) and Fungi (Candida and Aspergillus). Whereas moderate antifungal activity was found for our products, potent antimalarial and antileishmanial activities were observed for a few compounds. The nature of the substituents linked to the endoperoxide ring seems to play an important role in the bioactivities.

In vitro antileishmanial potentialities of essential oils from Citrus limon and Pistacia lentiscus harvested in Tunisia.

Leishmaniasis is a tropical parasitic disease that affects up to 12 million people worldwide. Current chemotherapies have limitations such as toxicity, high cost, and parasite resistance. This work aims to select an essential oil (EssOil) isolated from the Tunisian flora as a new antileishmanial candidate. Two plants were chosen for their antileishmanial potential: Citrus limon (Citrus) and Pistacia lentiscus (Pistacia). Each of these plants was harvested from two different sites (area 1 and area 2). Extracted EssOils were characterized using GC-MS. Their antiparasitic activity against axenic and intracellular Leishmania major amastigotes and their cytotoxicity were assessed. Citrus EssOil from area 1 displayed an interesting activity against L. major intramacrophage amastigotes with IC50 value at 4.2 ± 1.3 µg/mL. Interestingly, this activity was close to that of miltefosine. Moderate activities against intracellular amastigote were observed for Pistacia EssOil from area 1 and Citrus EssOil from area 2. However, low cytotoxicity with high selectivity index was proved only for Citrus EssOil from area 1, revealing its safety for macrophages. This study also demonstrated for the first time the antileishmanial activity of EssOil extracted from Citrus limon leaves. The EssOil interesting activity could be related to the lipophilic properties of terpenes that were shown in literature to contribute to the disruption of parasite intracellular metabolic pathways.

Correlation study on methoxylation pattern of flavonoids and their heme-targeted antiplasmodial activity.

A library of 33 polymethoxylated flavones (PMF) was evaluated for heme-binding affinity by biomimetic MS assay and in vitro antiplasmodial activity on two strains of P. falciparum. Stability of heme adducts was discussed using the dissociation voltage at 50% (DV50). No correlation was observed between the methoxylation pattern and the antiparasitic activity, either for the 3D7 chloroquine-sensitive or for the W2 chloroquine-resistant P. falciparum strains. However, in each PMF family an increased DV50 was observed for the derivatives methoxylated in position 5. Measurement of intra-erythrocytic hemozoin formation of selected derivatives was performed and hemozoin concentration was inversely correlated with heme-binding affinity. Kaempferol showed no influence on hemozoin formation, reinforcing the hypothesis that this compound may exert in vitro antiplasmodial activity mostly through other pathways. Pentamethoxyquercetin has simultaneously demonstrated a significant biological activity and a strong interaction with heme, suggesting that inhibition of hemozoin formation is totally or partially responsible for its antiparasitic effect.

Synthesis and Antimalarial Activity of 1,4-Disubstituted Piperidine Derivatives.

In order to prepare, at low cost, new compounds active against Plasmodium falciparum, and with a less side-effects, we have designed and synthesized a library of 1,4-disubstituted piperidine derivatives from 4-aminopiperidine derivatives 6. The resulting compound library has been evaluated against chloroquine-sensitive (3D7) and chloroquine-resistant (W2) strains of P. falciparum. The most active molecules-compounds 12d (13.64 nM (3D7)), 13b (4.19 nM (3D7) and 13.30 nM (W2)), and 12a (11.6 nM (W2))-were comparable to chloroquine (22.38 nM (3D7) and 134.12 nM (W2)).

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

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

Plasmodium vivax severe imported malaria in two migrants in France.

BACKGROUND: With less than one severe case per year in average, Plasmodium vivax is very rarely associated with severe imported malaria in France. Two cases of P. vivax severe malaria occurred in patients with no evident co-morbidity. Interestingly, both cases did not occur at the primary infection but during relapses. CASE PRESENTATIONS: Patient 1: A 27-year old male, born in Afghanistan and living in France since 2012, was admitted on August 2015 to the Avicenne hospital because of abdominal pain, intense headache, fever and hypotension. The patient was haemodynamically unstable despite 5 L of filling solution. A thin blood film showed P. vivax trophozoites within the red blood cells. To take care of the septic shock, the patient was given rapid fluid resuscitation, norepinephrine (0.5 mg/h), and intravenous artesunate. Nested polymerase chain reactions of the SSUrRNA gene were negative for Plasmodium falciparum but positive for P. vivax. The patient became apyretic in less than 24H and the parasitaemia was negative at the same time. Patient 2: A 24-year old male, born in Pakistan and living in France, was admitted on August 2016 because of fever, abdominal pain, headache, myalgia, and nausea. The last travel of the patient in a malaria endemic area occurred in 2013. A thin blood film showed P. vivax trophozoites within the red blood cells. The patient was treated orally by dihydroartemisinin-piperaquine and recovered rapidly. Nine months later, the patient returned to the hospital with a relapse of P. vivax malaria. The malaria episode was uncomplicated and the patient recovered rapidly. Three months later, the patient came back again with a third episode of P. vivax malaria. Following a rapid haemodynamic deterioration, the patient was transferred to the intensive care unit of the hospital. In all the patient received 10 L of filling solution to manage the septic shock. After 5 days of hospitalization and a specific treatment, the patient was discharged in good clinical conditions. CONCLUSION: Clinicians should be aware of the potential severe complications associated with P. vivax in imported malaria, even though the primary infection is uncomplicated.

Synthesis, In Silico, and In Vitro Evaluation of Anti-Leishmanial Activity of Oxadiazoles and Indolizine Containing Compounds Flagged against Anti-Targets.

Due to the lack of approved vaccines against human leishmaniasis and the limitations of the current chemotherapy inducing side effects and drug resistance, development of new, effective chemotherapeutic agents is essential. This study describes the synthesis of a series of novel oxadiazoles and indolizine-containing compounds. The compounds were screened in silico using an EIIP/AQVN filter followed by ligand-based virtual screening and molecular docking to parasite arginase. Top hits were further screened versus human arginase and finally against an anti-target battery to tag their possible interactions with proteins essential for the metabolism and clearance of many substances. Eight candidate compounds were selected for further experimental testing. The results show measurable in vitro anti-leishmanial activity for three compounds. One compound with an IC50 value of 2.18 µM on Leishmania donovani intramacrophage amastigotes is clearly better positioned than the others as an interesting molecular template for further development of new anti-leishmanial agents.

In-vitro and in-vivo antileishmanial activity of inexpensive Amphotericin B formulations: Heated Amphotericin B and Amphotericin B-loaded microemulsion.

Amphotericin B (AmB) is effective against visceral leishmaniasis (VL), but the renal toxicity of the conventional form, mixed micelles with deoxycholate (M-AmB), is often dose-limiting, while the less toxic lipid-based formulations such as AmBisome® are very expensive. Two different strategies to improve the therapeutic index of AmB with inexpensive ingredients were evaluated on this work: (i) the heat treatment of the commercial formulation (H-AmB) and (ii) the preparation of an AmB-loaded microemulsion (ME-AmB). M-AmB was heated to 70 °C for 20 min. The resulting product was characterized by UV spectrophotometry and circular dichroism, showing super-aggregates formation. ME-AmB was prepared from phosphate buffer pH 7.4, Tween 80®, Lipoid S100® and Mygliol 812® with AmB at 5 mg/mL. The droplet size, measured by dynamic light scattering, was about 40 nm and transmission electron microscopy confirmed a spherical shape. Rheological analysis showed low viscosity and Newtonian behavior. All the formulations were active in vitro and in vivo against Leishmania donovani (LV9). A selectivity index (CC50 on RAW/IC50 on LV9) higher than 10 was observed for ME-AmB, H-AmB and AmBisome®. Furthermore, no important in vivo toxicity was observed for all the samples. The in-vivo efficacy of the formulations after IV administration was evaluated in Balb/C mice infected with LV9 (three doses of 1 mg/kg AmB) and no significant difference was observed between H-AmB, M-AmB, ME-AmB and AmBisome®. In conclusion, these two inexpensive alternative formulations for AmB showing good efficacy and selectivity for Leishmania donovani merit further investigation.

Antiplasmodial activity of selected medicinal plants used to treat malaria in Ghana.

The use of medicinal plants for the treatment of diseases including malaria is commonplace in Ghanaian traditional medicine, though the therapeutic claims for most plants remain unvalidated. Antiplasmodial activity of the aqueous extracts and successively obtained petroleum ether, ethyl acetate and methanol fractions of the whole Phyllanthus fraternus plant, the leaves of Tectona grandis, Terminalia ivorensis and Bambusa vulgaris, and roots of Senna siamea were studied against Plasmodium falciparum chloroquine-sensitive 3D7 and chloroquine-resistant W2 strains. The aqueous extracts were assessed against human umbilical vein endothelial cells (HUVECs) for cytotoxicity, and the organic solvent fractions against human O(+) erythrocytes for haemolytic effect. Both extracts and fractions demonstrated antiplasmodial activity to varied extents. The aqueous extract of T. ivorensis was the most active (3D7, IC50 0.64 ± 0.14; and W2, IC50 10.52 ± 3.55 µg/mL), and together with P. fraternus displayed cytotoxicity (CC50 6.25 ± 0.40 and 31.11 ± 3.31 µg/mL, respectively). The aqueous extracts were generally selective for 3D7 strain of P. falciparum (selectivity indexes (SIs) ≥3.48) but only that of S. siamea was selective for the W2 strain (SI > 2.1). The organic solvent fractions also displayed antiplasmodial activity with the methanol fractions of P. fraternus and T. grandis, and the fractions of B. vulgaris showing activity with IC50 below 1 µg/mL against P. falciparum 3D7 strain; some fractions showed haemolytic effect but with low to high selectivity indexes (SI ≥ 4). The results while justifying the traditional use of the plant materials in the treatment of malaria, however, suggest their cautious use.

In Silico Mining for Antimalarial Structure-Activity Knowledge and Discovery of Novel Antimalarial Curcuminoids.

Malaria is a parasitic tropical disease that kills around 600,000 patients every year. The emergence of resistant Plasmodium falciparum parasites to artemisinin-based combination therapies (ACTs) represents a significant public health threat, indicating the urgent need for new effective compounds to reverse ACT resistance and cure the disease. For this, extensive curation and homogenization of experimental anti-Plasmodium screening data from both in-house and ChEMBL sources were conducted. As a result, a coherent strategy was established that allowed compiling coherent training sets that associate compound structures to the respective antimalarial activity measurements. Seventeen of these training sets led to the successful generation of classification models discriminating whether a compound has a significant probability to be active under the specific conditions of the antimalarial test associated with each set. These models were used in consensus prediction of the most likely active from a series of curcuminoids available in-house. Positive predictions together with a few predicted as inactive were then submitted to experimental in vitro antimalarial testing. A large majority from predicted compounds showed antimalarial activity, but not those predicted as inactive, thus experimentally validating the in silico screening approach. The herein proposed consensus machine learning approach showed its potential to reduce the cost and duration of antimalarial drug discovery.

VFV as a New Effective CYP51 Structure-Derived Drug Candidate for Chagas Disease and Visceral Leishmaniasis.

Sterol 14α-demethylases (CYP51) are the enzymes essential for sterol biosynthesis. They serve as clinical targets for antifungal azoles and are considered as targets for treatment of human Trypanosomatidae infections. Recently, we have shown that VNI, a potent and selective inhibitor of trypanosomal CYP51 that we identified and structurally characterized in complex with the enzyme, can cure the acute and chronic forms of Chagas disease. The purpose of this work was to apply the CYP51 structure/function for further development of the VNI scaffold. As anticipated, VFV (R)-N-(1-(3,4'-difluorobiphenyl-4-yl)-2-(1H-imidazol-1-yl)ethyl)-4-(5-phenyl-1,3,4-oxadiazol-2-yl)benzamide, the derivative designed to fill the deepest portion of the CYP51 substrate-binding cavity, reveals a broader antiprotozoan spectrum of action. It has stronger antiparasitic activity in cellular experiments, cures the experimental Chagas disease with 100% efficacy, and suppresses visceral leishmaniasis by 89% (vs 60% for VNI). Oral bioavailability, low off-target activity, favorable pharmacokinetics and tissue distribution characterize VFV as a promising new drug candidate.

Synthesis of 5-isoxazol-3-yl-pyrimidine nucleosides as potential antileishmanial agents.

A simple and practical procedure for the preparation of C5-(isoxazol-3-yl)-pyrimidine nucleosides through 1,3-dipolar cycloaddition of the in situ formed C5-nitrile oxide substituted pyrimidine nucleosides with various terminal alkynes is presented. Compared with literature procedures, this new method has advantageous features such as readily available and inexpensive starting materials, simple procedure without using expensive transition metal catalyst, and broad scope of substrates. By employing this method, 30 nucleoside analogues were prepared in moderate yields. Biological studies on these C5-(isoxazol-3-yl)-pyrimidine nucleosides showed that most of them exhibited significant in vitro antileishmanial activity.

Effect of Phlebotomus papatasi on the fitness,infectivity and antimony-resistance phenotype of antimony-resistant Leishmania major Mon-25.

Leishmania major is responsible for zoonotic cutaneous leishmaniasis. Therapy is mainly based on the use of antimony-based drugs; however, treatment failures and illness relapses were reported. Although studies were developed to understand mechanisms of drug resistance, the interactions of resistant parasites with their reservoir hosts and vectors remain poorly understood. Here we compared the development of two L. major MON-25 trivalent antimony-resistant lines, selected by a stepwise in vitro Sb(III)-drug pressure, to their wild-type parent line in the natural vector Phlebotomus papatasi. The intensity of infection, parasite location and morphological forms were compared by microscopy. Parasite growth curves and IC50 values have been determined before and after the passage in Ph. papatasi. qPCR was used to assess the amplification rates of some antimony-resistance gene markers. In the digestive tract of sand flies, Sb(III)-resistant lines developed similar infection rates as the wild-type lines during the early-stage infections, but significant differences were observed during the late-stage of the infections. Thus, on day 7 p. i., resistant lines showed lower representation of heavy infections with colonization of the stomodeal valve and lower percentage of metacyclic promastigote forms in comparison to wild-type strains. Observed differences between both resistant lines suggest that the level of Sb(III)-resistance negatively correlates with the quality of the development in the vector. Nevertheless, both resistant lines developed mature infections with the presence of infective metacyclic forms in almost half of infected sandflies. The passage of parasites through the sand fly guts does not significantly influence their capacity to multiply in vitro. The IC50 values and molecular analysis of antimony-resistance genes showed that the resistant phenotype of Sb(III)-resistant parasites is maintained after passage through the sand fly. Sb(III)-resistant lines of L. major MON-25 were able to produce mature infections in Ph. papatasi suggesting a possible circulation in the field using this vector.