Treatment of murine visceral leishmaniasis using an 8-hydroxyquinoline-containing polymeric micelle system

Development of a topical treatment for tegumentary leishmaniasis using 8-hydroxyquinoline

In the context of neglected diseases, tegumentary leishmaniasis (TL) presents an emerging and re-emerging character in the national territory and in the world. The treatment of TL has limitations, such as intravenous administration route, high toxicity, and high treatment costs. Thus, several researchers work on new therapeutic strategies to improve the effectiveness of the treatment of leishmaniasis. In this light, the present study used a topical formulation, containing 8-hydroquinoline (8-HQN), for the treatment of Balb/c mice infected with L. amazonensis. After the treatment, the mean diameter of the lesion was measured, as well as the parasite load in organs and immunological parameters associated with the treatment. The results showed that the animals treated with 8-HQN 5%, when compared to controls, showed a reduction in the mean diameter of the lesion and in the parasite load. The animals treated with the ointment showed a type 1 cellular immune response profile associated with the production of cytokines such as INF-γ and TNF-α. In addition, the treatment did not demonstrate toxicity to mice. Therefore, the topical formulation containing 8-HQN 5% is a promising candidate in the topical treatment and could be considered, in the future, as an alternative for the treatment of TL.

Treatment using vanillin-derived synthetic molecules incorporated into polymeric micelles is effective against infection caused by Leishmania amazonensis species

Treatment against leishmaniasis presents problems, mainly due to the toxicity of the drugs, high cost, and the emergence of resistant strains. A previous study showed that two vanillin-derived synthetic molecules, 3s [4-(2-hydroxy-3-(4-octyl-1H-1,2,3-triazol-1-yl)propoxy)-3-methoxybenzaldehyde] and 3t [4-(3-(4-decyl-1H-1,2,3-triazol-1-yl)-2-hydroxypropoxy)-3-methoxybenzaldehyde], presented antileishmanial activity against Leishmania infantum, L. amazonensis, and L. braziliensis species. In the present work, 3s and 3t were evaluated to treat L. amazonensis-infected mice. Molecules were used pure or incorporated into Poloxamer 407-based micelles. In addition, amphotericin B (AmpB) and its liposomal formulation, Ambisome®, were used as control. Animals received the treatment and, one and 30 days after, they were euthanized to evaluate immunological, parasitological, and biochemical parameters. Results showed that the micellar compositions (3s/Mic and 3t/Mic) induced significant reductions in the lesion mean diameter and parasite load in the infected tissue and distinct organs, as well as a specific and significant antileishmanial Th1-type immune response, which was based on significantly higher levels of IFN-γ, IL-12, nitrite, and IgG2a isotype antibodies. Drug controls showed also antileishmanial action; although 3s/Mic and 3t/Mic have presented better and more significant parasitological and immunological data, which were based on significantly higher IFN-γ production and lower parasite burden in treated animals. In addition, significantly lower levels of urea, creatinine, alanine transaminase, and aspartate transaminase were found in mice treated with 3s/Mic and 3t/Mic, when compared to the others. In conclusion, results suggest that 3s/Mic and 3t/Mic could be considered as therapeutic candidates to treat against L. amazonensis infection.

New synthetic molecules incorporated into polymeric micelles used for treatment against visceral leishmaniasis

Treatment against visceral leishmaniasis (VL) presents problems, mainly related to drug toxicity, high cost and/or by emergence of resistant strains. In the present study, two vanillin synthetic derivatives, 3 s [4-(2-hydroxy-3-(4-octyl-1H-1,2,3-triazol-1-yl)propoxy)-3-methoxybenzaldehyde] and 3 t [4-(3-(4-decyl-1H-1,2,3-triazol-1-yl)-2-hydroxypropoxy)-3-methoxybenzaldehyde], were evaluated as therapeutic candidates in a murine model against Leishmania infantum infection. Molecules were used pure (3 s and 3 t) or incorporated into Poloxamer 407-based micelles (3 s/M and 3 t/M) in the infected animals, which also received amphotericin B (AmpB) or Ambisome® as control. Results showed that 3 s/M and 3 t/M compositions induced a Th1-type immune response in treated animals, with higher levels of IFN-γ, IL-2, TNF-α, IL-12, nitrite, and IgG2a antibodies. Animals presented also low toxicity and significant reductions in the parasite load in their spleens, livers, bone marrows and draining lymph nodes, as compared as control groups mice, with the evaluations performed one and 30 days after the application of the therapeutics. In conclusion, preliminary data suggest that 3 s/M and 3 t/M could be considered for future studies as therapeutic agents against VL.

Immunization with recombinant LiHyp1 protein plus adjuvant is protective against tegumentary leishmaniasis

Tegumentary leishmaniasis (TL) is the main clinical manifestation of leishmaniasis, and it can cause the infected hosts to self-healing cutaneous lesions until mutilating scars in mucosal membranes, particularly in the nose and throat. The treatment against disease presents problems, and the diagnosis is hampered by variable sensitivity and/or specificity of the tests. In this context, the development of prophylactic vaccines could be considered as a strategy to control the disease. Previously, we showed that the recombinant LiHyp1 protein plus adjuvant protected mice from infection with Leishmania infantum, which causes visceral leishmaniasis. In the present study, we tested whether rLiHyp1 could induce protection against infection with L. amazonensis, a parasite species able to cause TL. We immunized BALB/c mice with rLiHyp1 plus saponin (rLiHyp1/S) or incorporated in micelles (rLiHyp1/M) as adjuvants and performed parasitological and immunological evaluations before and after infection. Results showed that after in vitro stimulation from spleen cell cultures using rLiHyp1 or a Leishmania antigenic extract (SLA), rLiHyp1/S and rLiHyp1/M groups developed a Th1-type immune response, which was characterized by high levels of IFN-γ, IL-2, TNF-α and IL-12 cytokines, nitrite, and IgG2a isotype antibodies when compared to values found in the control (saline, saponin, micelles alone) groups, which showed higher levels of anti-SLA IL-4, IL-10, and IgG1 antibodies before and after challenge. In addition, mice receiving rLiHyp1/S or rLiHyp1/M presented significant reductions in the lesion average diameter and parasite load in the infected tissue and internal organs. Blood samples were collected from healthy subjects and TL patients to obtain PBMC cultures, which were in vitro stimulated with rLiHyp1 or SLA, and results showed higher lymphoproliferation and IFN-γ production after stimulus using rLiHyp1, as compared to values found using SLA. These results suggest that rLiHyp1 plus adjuvant was protective against experimental TL and could also be considered for future studies as a vaccine candidate against human disease.

Therapeutic Activity of a Topical Formulation Containing 8-Hydroxyquinoline for Cutaneous Leishmaniasis

Cutaneous leishmaniasis exhibits a wide spectrum of clinical manifestations; however, only a limited number of drugs are available and include Glucantime® and amphotericin B, which induce unacceptable side effects in patients, limiting their use. Thus, there is an urgent demand to develop a treatment for leishmaniasis. Recently, it was demonstrated that 8-hydroxyquinoline (8-HQ) showed significant leishmanicidal effects in vitro and in vivo. Based on that, this work aimed to develop a topical formulation containing 8-HQ and assess its activity in experimental cutaneous leishmaniasis. 8-HQ was formulated using a Beeler base at 1 and 2% and showed an emulsion size with a D50 of 25 and 51.3 µm, respectively, with a shear-thinning rheological behaviour. The creams were able to permeate artificial Strat-M membranes and excised porcine skin without causing any morphological changes in the porcine skin or murine skin tested. In BALB/c mice infected with L. (L.) amazonensis, topical treatment with creams containing 1 or 2% of 8-HQ was found to reduce the parasite burden and lesion size compared to infected controls with comparable efficacy to Glucantime® (50 mg/kg) administered at the site of the cutaneous lesion. In the histological section of the skin from infected controls, a diffuse inflammatory infiltrate with many heavily infected macrophages that were associated with areas of necrosis was observed. On the other hand, animals treated with both creams showed only moderate inflammatory infiltrate, characterised by few infected macrophages, while tissue necrosis was not observed. These histological characteristics in topically treated animals were associated with an increase in the amount of IFN-γ and a reduction in IL-4 levels. The topical use of 8-HQ was active in decreasing tissue parasitism and should therefore be considered an interesting alternative directed to the treatment of leishmaniasis, considering that this type of treatment is non-invasive, painless, and, importantly, does not require hospitalisation, improving patient compliance by allowing the treatment to be conducted.

Efficacy of an Immunotherapy Combining Immunogenic Chimeric Protein Plus Adjuvant and Amphotericin B against Murine Visceral Leishmaniasis

Visceral leishmaniasis (VL) in the Americas is a chronic systemic disease caused by infection with Leishmania infantum parasites. The toxicity of antileishmanial drugs, long treatment course and limited efficacy are significant concerns that hamper adequate treatment against the disease. Studies have shown the promise of an immunotherapeutics approach, combining antileishmanial drugs to reduce the parasitism and vaccine immunogens to activate the host immune system. In the current study, we developed an immunotherapy using a recombinant T cell epitope-based chimeric protein, ChimT, previously shown to be protective against Leishmania infantum, with the adjuvant monophosphoryl lipid A (MPLA) and amphotericin B (AmpB) as the antileishmanial drug. BALB/c mice were infected with L. infantum stationary promastigotes and later they received saline or were treated with AmpB, MPLA, ChimT/Amp, ChimT/MPLA or ChimT/MPLA/AmpB. The combination of ChimT/MPLA/AmpB significantly reduced the parasite load in mouse organs (p < 0.05) and induced a Th1-type immune response, which was characterized by higher ratios of anti-ChimT and anti-parasite IgG2a:IgG1 antibodies, increased IFN-γ mRNA and IFN-γ and IL-12 cytokines and accompanied by lower levels of IL-4 and IL-10 cytokines, when compared to other treatments and controls (all p < 0.05). Organ toxicity was also lower with the ChimT/MPLA/AmpB immunotherapy, suggesting that the inclusion of the vaccine and adjuvant ameliorated the toxicity of AmpB to some degree. In addition, the ChimT vaccine alone stimulated in vitro murine macrophages to significantly kill three different internalized species of Leishmania parasites and to produce Th1-type cytokines into the culture supernatants. To conclude, our data suggest that the combination of ChimT/MPLA/AmpB could be considered for further studies as an immunotherapy for L. infantum infection.

High Selectivity of 8-Hydroxyquinoline on Leishmania (Leishmania) and Leishmania (Viannia) Species Correlates with a Potent Therapeutic Activity In Vivo

Leishmaniasis is a neglected disease caused by protozoa of the genus Leishmania, which causes different clinical manifestations. Drugs currently used in the treatment such as pentavalent antimonial and amphotericin B cause severe side effects in patients, and parasite resistance has been reported. Thus, it is necessary and urgent to characterize new and effective alternative drugs to replace the current chemotherapy of leishmaniasis. In this regard, it has been experimentally demonstrated that quinoline derivatives present significative pharmacological and parasitic properties. Thus, the aim of this work was to demonstrate the leishmanicidal activity of 8-hydroxyquinoline (8-HQ) in vitro and in vivo. The leishmanicidal activity (in vitro) of 8-HQ was assayed on promastigote and intracellular amastigote forms of L. (L.) amazonensis, L. (L.) infantum chagasi, L. (V.) guyanensis L. (V.) naiffi, L. (V.) lainsoni, and L. (V.) shawi. Additionally, the levels of nitric oxide and hydrogen peroxide were analyzed. The therapeutic potential of 8-HQ was analyzed in BALB/c mice infected with a strain of L. (L.) amazonensis that causes anergic cutaneous diffuse leishmaniasis. In vitro data showed that at 24 and 72 h, 8-HQ eliminated promastigote and intracellular amastigote forms of all studied species and this effect may be potentialized by nitric oxide. Furthermore, 8-HQ was more selective than miltefosine. Infected animals treated with 8-HQ by the intralesional route dramatically reduced the number of tissue parasites in the skin, and it was associated with an increase in IFN-γ and decrease in IL-4, which correlated with a reduction in inflammatory reaction in the skin. These results strongly support the idea that 8-HQ is an alternative molecule that can be employed in the treatment of leishmaniasis, given its selectivity and multispectral action in parasites from the Leishmania genus.

Parasitological and immunological evaluation of a quinoline derivative salt incorporated into a polymeric micelle formulation against Leishmania infantum infection

Leishmaniasis is a parasitic disease caused by Leishmania protozoa, which presents a large spectrum of clinical manifestations. In the present study, a quinoline derivative salt named N-(2-((7-chloroquinolin-4-yl)amino)ethyl)-N-(prop-2-yn-1-yl)prop-2-yn-1-aminium chloride or QDS3 was in vitro and in vivo tested against L. infantum by means of its incorporation in Poloxamer 407-based polymeric micelles (QDS3/M). The in vitro antileishmanial activity of QDS3 and QDS3/M was investigated in L. infantum promastigotes, axenic amastigotes and infected macrophages. BALB/c mice were infected with L. infantum, and parasitological parameters were evaluated 1 and 15 days post-treatment by determining the parasite load by a limiting dilution assay, besides a quantitative PCR (qPCR) method. Immunological response was assessed based on production of cellular cytokines, as well as by quantification of nitrite levels and specific antibodies. In vitro results showed that QDS3 free or in micelles presented effective antileishmanial action against both parasite stages, being more effective in amastigotes. In vivo data showed that treatment using QDS3 or QDS3/M reduced the parasite load in the livers, spleens, draining lymph nodes (dLN) and bone marrows of the treated animals, 1 and 15 days after treatment, when compared to values found in the control groups. Additionally, treated mice developed a polarized Th1-type immune response, with higher levels of IL-12, IFN-γ, GM-CSF and nitrite, besides high production of specific IgG2a antibodies, when compared to the controls. Parasitological and immunological data obtained using the micellar composition were better than the others. In conclusion, QDS3, mainly when applied in a delivery adjuvant system, could be considered for future studies as therapeutic candidate against VL.

Flau-A, a naphthoquinone derivative, is a promising therapeutic candidate against visceral leishmaniasis: A preliminary study

Visceral leishmaniasis (VL) is a neglected tropical disease found in tropical and subtropical regions in the world. The therapeutics used for the treatment against disease presents problems, mainly related to drug toxicity, route of administration, high cost and/or by emergence of resistant strains. In this context, the search for alternative antileishmanial candidates is desirable. Recently, a naphthoquinone derivative namely 2-(2,3,4-tri-O-acetyl-6-deoxy-β-L-galactopyranosyloxy)-1,4-naphthoquinone or Flau-A showed an effective in vitro biological action against Leishmania infantum. In the present study, the efficacy of this naphthoquinone derivative was evaluated in an in vivo infection model. BALB/c mice (n = 12 per group) were infected and later received saline or were treated with empty micelles (B/Mic), free Flau-A or it incorporated in Poloxamer 407-based micelles (Flau-A/Mic). The products were administered subcutaneously in the infected animals, which were then euthanized one (n = 6 per group) and 15 (n = 6 per group) days post-therapy, when immunological and parasitological evaluations were performed. Results showed that animals treated with Flau-A or Flau-A/Mic produced significantly higher levels of antileishmanial IFN-γ, IL-12, TNF-α, GM-CSF, nitrite and IgG2a isotype antibody, when compared to data found in the control (saline and B/Mic) groups; which showed significantly higher levels of parasite-specific IL-4, IL-10 and IgG1 antibody. In addition, animals receiving free Flau-A or Flau-A/Mic presented also significant reductions in the parasite load in their spleens, livers, bone marrows and draining lymph nodes, when compared to the controls. A low hepatic and renal toxicity was also found. Overall, Flau-A/Mic showed better immunological and parasitological results, when compared to the use of free molecule. In conclusion, preliminary data suggest that this composition could be considered in future studies as promising therapeutic candidate against VL.

Immunomodulatory role of Th17 pathway in experimental visceral leishmaniasis

Visceral leishmaniasis (VL) or Kala-azar is a vector borne protozoan infection caused by Leishmania donovani in the Indian subcontinent mainly India, Nepal and Bangladesh. It is a major public health problem in these countries mostly affecting the socio-economically poor population. Leishmaniasis ranks the third most important disease after malaria and filariasis but is still considered as one of the neglected tropical diseases of the world. For development of better therapeutic agents and effective vaccine against VL, there is a need to understand host immunological changes that play a vital role during course of infection. Therefore, we investigated the role of Th17 pathway in Balb/c mice during Leishmania donovani infection and treatment with amphotericin B. Mice were divided in four groups i.e. Control, Infected, Uninfected treated and Infected treated. The cytokine levels were estimated in the spleen of Balb/c mice on days 1, 3, 7, 14, 17, 21, 28, 35, 45 and 60 post infection and during course of treatment. The mRNA levels of the Th17 pathway during active Leishmania donovani infection and after treatment were determined by real time polymerase chain reaction (RT-PCR) and protein levels by flow cytometry and ELISA. Results of our study revealed that active infection was associated with low levels of Th17 cytokines IL-17, IL-22 and IL-23 and elevated levels of IL-6, IL-1β and TGF-β. Amphotericin B treatment restored production of pro-inflammatory cytokines IL-17 and IL-22. The levels of transcription factor RORγt were found to correlate with the levels of IL-17 during infection and also after chemotherapy whereas STAT3 levels were elevated during infection and vice versa after treatment. The findings of this study suggest that Th17 cytokines IL-17 and IL-22 are associated with protection against VL infection and development of any interventions or chemotherapeutic agents targeting Th17 pathway could be an important approach for VL treatment.

Nanotechnology-aided diagnosis, treatment and prevention of leishmaniasis

Leishmaniasis is a prevalent parasitic infection belonging to neglected tropical diseases. It is caused by Leishmania protozoan parasites transmitted by sandflies and it is responsible for increased morbidity/mortality especially in low- and middle-income countries. The lack of cheap, portable, easy to use diagnostic tools exhibiting high efficiency and specificity impede the early diagnosis of the disease. Furthermore, the typical anti-leishmanial agents are cytotoxic, characterized by low patient compliance and require long-term regimen and usually hospitalization. In addition, due to the intracellular nature of the disease, the existing treatments exhibit low bioavailability resulting in low therapeutic efficacy. The above, combined with the common development of resistance against the anti-leishmanial agents, denote the urgent need for novel therapeutic strategies. Furthermore, the lack of effective prophylactic vaccines hinders the control of the disease. The development of nanoparticle-based biosensors and nanocarrier-aided treatment and vaccination strategies could advance the diagnosis, therapy and prevention of leishmaniasis. The present review intends to highlight the various nanotechnology-based approaches pursued until now to improve the detection of Leishmania species in biological samples, decrease the side effects and increase the efficacy of anti-leishmanial drugs, and induce enhanced immune responses, specifically focusing on the outcome of their preclinical and clinical evaluation.

Green Approach: ''A Forwarding Step for Curing Leishmaniasis-A Neglected Tropical Disease''

The present review focuses on a dreaded vector-mediated leishmaniasis, with the existing therapeutic approaches including a variety of drugs along with their limitations, the treatment with natural compounds, and different types of metal/metal oxide nanoparticles (NPs). As evidenced, various metallic NPs, comprising silver, silver oxide, gold, zinc oxide, titanium, lead oxide, etc., played a curative role to treat leishmaniasis, are also presented. Keeping in view the advance success of vaccines against the prevalent dreaded diseases in the past and the present scenario, efforts are also being made to develop vaccines based on these NP formulations.

Acarbose presents in vitro and in vivo antileishmanial activity against Leishmania infantum and is a promising therapeutic candidate against visceral leishmaniasis

Treatment against visceral leishmaniasis (VL) is mainly hampered by drug toxicity, long treatment regimens and/or high costs. Thus, the identification of novel and low-cost antileishmanial agents is urgent. Acarbose (ACA) is a specific inhibitor of glucosidase-like proteins, which has been used for treating diabetes. In the present study, we show that this molecule also presents in vitro and in vivo specific antileishmanial activity against Leishmania infantum. Results showed an in vitro direct action against L. infantum promastigotes and amastigotes, and low toxicity to mammalian cells. In addition, in vivo experiments performed using free ACA or incorporated in a Pluronic^® F127-based polymeric micelle system called ACA/Mic proved effective for the treatment of L. infantum-infected BALB/c mice. Treated animals presented significant reductions in the parasite load in their spleens, livers, bone marrows and draining lymph nodes when compared to the controls, as well as the development of antileishmanial Th1-type humoral and cellular responses based on high levels of IFN-γ, IL-12, TNF-α, GM-CSF, nitrite and IgG2a isotype antibodies. In addition, ACA or ACA-treated animals suffered from low organ toxicity. Treatment with ACA/Mic outperformed treatments using either Miltefosine or free ACA based on parasitological and immunological evaluations performed one and 15 days post-therapy. In conclusion, data suggest that the ACA/Mic is a potential therapeutic agent against L. infantum and merits further consideration for VL treatment.

In vitro and in vivo antileishmanial activity of β-acetyl-digitoxin, a cardenolide of Digitalis lanata potentially useful to treat visceral leishmaniasis

Current treatments of visceral leishmaniasis face limitations due to drug side effects and/or high cost, along with the emergence of parasite resistance. Novel and low-cost antileishmanial agents are therefore required. We report herein the antileishmanial activity of β-acetyl-digitoxin (b-AD), a cardenolide isolated from Digitalis lanata leaves, assayed in vitro and in vivo against Leishmania infantum. Results showed direct action of b-AD against parasites, as well as efficacy for the treatment of Leishmania-infected macrophages. In vivo experiments using b-AD-containing Pluronic^® F127 polymeric micelles (b-AD/Mic) to treat L. infantum-infected mice showed that this composition reduced the parasite load in distinct organs in more significant levels. It also induced the development of anti-parasite Th1-type immunity, attested by high levels of IFN-γ, IL-12, TNF-α, GM-CSF, nitrite and specific IgG2a antibodies, in addition to low IL-4 and IL-10 contents, along with higher IFN-γ-producing CD4⁺ and CD8⁺ T-cell frequency. Furthermore, low toxicity was found in the organs of the treated animals. Comparing the therapeutic effect between the treatments, b-AD/Mic was the most effective in protecting animals against infection, when compared to the other groups including miltefosine used as a drug control. Data found 15 days after treatment were similar to those obtained one day post-therapy. In conclusion, the results obtained suggest that b-AD/Mic is a promising antileishmanial agent and deserves further studies to investigate its potential to treat visceral leishmaniasis.

Application of Poloxamers for the Development of Drug Delivery System to Treat Leishmaniasis: A Review

Leishmaniasis is a neglected tropical disease affecting more than 1.5 million people annually, with an annual mortality of over 20.000. The drugs used for its treatment are toxic, expensive, require extended treatment times and present variable efficacy. The disease severity and therapy limitations suggest the need for new antileishmanial agents. In this context, in order to identify new options for treatment, a number of studies based on nanotechnological strategies have been carried out. Poloxamers are triblock copolymers very often utilized for nanotherapeutic solutions, resulting in products with better solubility, higher stability, superior therapeutic efficacy and less toxicity. This review will discuss the physicochemical properties of the copolymers, as well as describe the use of poloxamers for the development of therapeutic formulations to treat leishmaniasis.

Ivermectin presents effective and selective antileishmanial activity in vitro and in vivo against Leishmania infantum and is therapeutic against visceral leishmaniasis

Treatment for visceral leishmaniasis (VL) is hindered mainly by the toxicity and/or high cost of therapeutic drugs. In addition, parasite resistance has been registered. Thus, there is an urgent need for the identification of novel, effective and low-cost antileishmanial agents. Since drug discovery is a long and expensive process, drug repositioning for treatment of leishmaniasis should be considered. In the present study, Ivermectin (IVE), a broad-spectrum drug used for treatment of parasitic diseases, was evaluated in vitro and in vivo against Leishmania infantum species. Results in vitro showed that IVE presented 50% Leishmania and macrophage inhibitory concentrations (IC₅₀ and CC₅₀, respectively) of 3.64 ± 0.48 μM and 427.50 ± 17.60 μM, respectively, with a selectivity index (SI) of 117.45; whereas Amphotericin B (AmpB), which was used as control, showed IC₅₀ and CC₅₀ values of 0.12 ± 0.05 μM and 1.06 ± 0.23 μM, respectively, with a corresponding SI of 8.90. Treatment with IVE effectively reduced the infection percentage and parasite burden in infected and treated macrophages and displayed a prophylactic activity by inhibiting macrophage infection with pre-treated parasites. Furthermore, preliminary studies suggested that IVE targets the parasite's mitochondria. Activity of IVE in its free format or incorporated into Pluronic® F127-based polymeric micelles (IVE/Mic) was also evaluated in vivo as a treating drug for L. infantum-infected BALB/c mice. Miltefosine was used as a control. Results showed that Miltefosine, IVE and IVE/Mic-treated animals presented significant reductions in the parasite load in their spleens, livers, bone marrows and draining lymph nodes, as well as development of an antileishmanial Th1-type immune response one and 15 days after treatment. Notably, IVE/Mic showed a better parasitological and immunological response in comparison to other alternative treatments. In conclusion, results suggest that IVE/Mic could be considered in future studies as a therapeutic alternative to treat VL.

Digitoxigenin presents an effective and selective antileishmanial action against Leishmania infantum and is a potential therapeutic agent for visceral leishmaniasis

Treatment for visceral leishmaniasis (VL) is hampered mainly by drug toxicity, their high cost, and parasite resistance. Drug development is a long and pricey process, and therefore, drug repositioning may be an alternative worth pursuing. Cardenolides are used to treat cardiac diseases, especially those obtained from Digitalis species. In the present study, cardenolide digitoxigenin (DIGI) obtained from a methanolic extract of Digitalis lanata leaves was tested for its antileishmanial activity against Leishmania infantum species. Results showed that 50% Leishmania and murine macrophage inhibitory concentrations (IC₅₀ and CC₅₀, respectively) were of 6.9 ± 1.5 and 295.3 ± 14.5 μg/mL, respectively. With amphotericin B (AmpB) deoxycholate, used as a control drug, values of 0.13 ± 0.02 and 0.79 ± 0.12 μg/mL, respectively, were observed. Selectivity index (SI) values were of 42.8 and 6.1 for DIGI and AmpB, respectively. Preliminary studies suggested that the mechanism of action for DIGI is to cause alterations in the mitochondrial membrane potential, to increase the levels of reactive oxygen species and induce accumulation of lipid bodies in the parasites. DIGI was incorporated into Pluronic® F127-based polymeric micelles, and the formula (DIGI/Mic) was used to treat L. infantum–infected mice. Miltefosine was used as a control drug. Results showed that animals treated with either miltefosine, DIGI, or DIGI/Mic presented significant reductions in the parasite load in their spleens, livers, bone marrows, and draining lymph nodes, as well as the development of a specific Th1-type response, when compared with the controls. Results obtained 1 day after treatment were corroborated with data corresponding to 15 days after therapy. Importantly, treatment with DIGI/Mic induced better parasitological and immunological responses when compared with miltefosine- and DIGI-treated mice. In conclusion, DIGI/Mic has the potential to be used as a therapeutic agent to protect against L. infantum infection, and it is therefore worth of consideration in future studies addressing VL treatment.

Nano- and Microformulations to Advance Therapies for Visceral Leishmaniasis

Visceral leishmaniasis (VL) is a deadly, vector-borne, neglected tropical disease endemic to arid parts of the world and is caused by a protozoan parasite of the genus Leishmania. Chemotherapy is the primary treatment for this systemic disease, and multiple potent therapies exist against this intracellular parasite. However, several factors, such as systemic toxicity, high costs, arduous treatment regimen, and rising drug resistance, are barriers for effective therapy against VL. Material-based platforms have the potential to revolutionize chemotherapy for leishmaniasis by imparting a better pharmacokinetic profile and creating patient-friendly routes of administration, while also lowering the risk for drug resistance. This review highlights promising drug delivery strategies and novel therapies that have been evaluated in preclinical models, demonstrating the potential to advance chemotherapy for VL.

Parasitological and immunological evaluation of a novel chemotherapeutic agent against visceral leishmaniasis

AIMS

Treatment for visceral leishmaniasis (VL) is hampered by the toxicity and/or high cost of drugs, as well as by emergence of parasite resistance. Therefore, there is an urgent need for new antileishmanial agents.

METHODS AND RESULTS

In this study, the antileishmanial activity of a diprenylated flavonoid called 5,7,3,4'-tetrahydroxy-6,8-diprenylisoflavone (CMt) was tested against Leishmania infantum and L amazonensis species. Results showed that CMt presented selectivity index (SI) of 70.0 and 165.0 against L infantum and L amazonensis promastigotes, respectively, and of 181.9 and 397.8 against respective axenic amastigotes. Amphotericin B (AmpB) showed lower SI values of 9.1 and 11.1 against L infantum and L amazonensis promastigotes, respectively, and of 12.5 and 14.3 against amastigotes, respectively. CMt was effective in the treatment of infected macrophages and caused alterations in the parasite mitochondria. L infantum-infected mice treated with miltefosine, CMt alone or incorporated in polymeric micelles (CMt/Mic) presented significant reductions in the parasite load in distinct organs, when compared to the control groups. An antileishmanial Th1-type cellular and humoral immune response were developed one and 15 days after treatment, with CMt/Mic-treated mice presenting a better protective response.

CONCLUSION

Our data suggest that CMt/Mic could be evaluated as a chemotherapeutic agent against VL.

Liposomal Formulation of ChimeraT, a Multiple T-Cell Epitope-Containing Recombinant Protein, Is a Candidate Vaccine for Human Visceral Leishmaniasis

Background: Leishmaniases are neglected diseases caused by infection with Leishmania parasites and there are no human vaccines in use routinely. The purpose of this study was to examine the immunogenicity of ChimeraT, a novel synthetic recombinant vaccine against visceral leishmaniasis (VL), incorporated into a human-compatible liposome formulation. Methods: BALB/c mice were immunized subcutaneously with ChimeraT/liposome vaccine, ChimeraT/saponin adjuvant, or ChimeraT/saline and immune responses examined in vitro and in vivo. Results: Immunization with the ChimeraT/liposome formulation induced a polarized Th1-type response and significant protection against L. infantum infection. ChimeraT/liposome vaccine stimulated significantly high levels of interferon (IFN)-γ, interleukin (IL)-12, and granulocyte macrophage-colony stimulating factor (GM-CSF) cytokines by both CD4 and CD8 T-cells, with correspondingly lower levels of IL-4 and IL-10 cytokines. Induced antibodies were predominantly IgG2a isotype, and homologous antigen-stimulated spleen cells produced significant nitrite as a proxy for nitric oxide (NO). Furthermore, we examined a small number of treated VL patients and found higher levels of circulating anti-ChimeraT protein IgG2 antibodies, compared to IgG1 levels. Conclusions: Overall, the liposomal formulation of ChimeraT induced a protective Th1-type immune response and thus could be considered in future studies as a vaccine candidate against human VL.

A clioquinol-containing Pluronic® F127 polymeric micelle system is effective in the treatment of visceral leishmaniasis in a murine model

A clioquinol (ICHQ)-containing Pluronic^® F127 polymeric micelle system (ICHQ/Mic) was recently shown to be effective against Leishmania amazonensis infection in a murine model. In the present study, ICHQ/Mic was tested against L. infantum infection. BALB/c mice (n = 12 per group) were infected with L. infantum stationary promastigotes through subcutaneous injection and, 45 days after challenge, received saline or were treated via the subcutaneous route with empty micelles, ICHQ or ICHQ/Mic. In addition, animals were treated with miltefosine by the oral route, as a drug control. Half of the animals were euthanized 1 and 15 days after treatment, aiming to evaluate two endpoints after therapy, when parasitological and immunological parameters were investigated. Results showed that the treatment using miltefosine, ICHQ or ICHQ/Mic induced significantly higher anti-parasite IFN-γ, IL-12, GM-CSF, nitrite and IgG2a isotype antibody levels, which were associated with low IL-4 and IL-10 production. In addition, a higher frequency of IFN-γ and TNF-α-producing CD4⁺ and CD8⁺ T-cells was found in these animals. The parasite load was evaluated in distinct organs, and results showed that the treatment using miltefosine, ICHQ or ICHQ/Mic induced significant reductions in organic parasitism in the treated and infected mice. A comparison between the treatments suggested that ICHQ/Mic was the most effective in inducing a highly polarized Th1-type response, as well as reducing the parasite load in significant levels in the treated and infected animals. Data obtained 15 days after treatment suggested maintenance of the immunological and parasitological responses. In conclusion, ICHQ/Mic could be considered in future studies for the treatment of visceral leishmaniasis.

Nitroxoline: a potent antimicrobial agent against multidrug resistant Enterobacteriaceae

Antimicrobial resistance has become a prime global concern. An ability of the microbes to produce enzymes to destroy antimicrobial drugs is one of the well-known mechanisms underlying the resistance. 8-Hydroxyquinoline (8HQ) and derivatives were reported to exert diverse biological effects such as antimicrobial, antioxidant and antineurodegenerative activities. Herein, 8HQ (1), nitroxoline (NQ, 2) and 7-Br-8HQ (3) were investigated for antimicrobial activity against Enterobacteriaceae including extended spectrum β-lactamase (ESBL)-producing and carbapenemase-producing strains as well as the effect of metal ions. These compounds (1-3) displayed the great antimicrobial activity against fifty-eight bacterial isolates of Escherichiacoli, Providenciarettgeri and Klebsiellapneumoniae, in which NQ (2) exerted the highest antimicrobial activity with a MIC₅₀ of 42.04 μM (8 µg/mL) and MBC₅₀ of 168.28 μM (32 µg/mL). The MIC values of NQ (2) and 7-Br-8HQ (3) were significantly increased in the presence of Cu²⁺ and Fe³⁺. This finding reveals that NQ could be an effective compound to be further developed as an antimicrobial agent for combating Enterobacteriaceae infections.

Innovative Solutions for the Control of Leishmaniases: Nanoscale Drug Delivery Systems

Background:

Leishmania are sandfly-transmitted protozoan parasites that harbour within the macrophages of a mammalian host and cause leishmaniasis, a serious zoonotic disease that threatens the lives of millions worldwide. Its numerous forms (cutaneous, mucocutaneous, and visceral) are currently treated with a sparse arsenal of drugs, specifically antimonials, amphotericin B, miltefosine, and paromomycin, for which drug resistance and clinical failure are rampant. Medicine is presently trending towards nanotechnology to aid in the successful delivery of drugs. Vehicles such as lipid-based nanocarriers, polymer-based nanoparticles, and metal ions and oxides have been previously demonstrated to improve bioavailability of drugs and decrease toxicity for the patient. These cutting-edge solutions can be combined with existing active molecules, as well as novel drugs or plant extracts with promising antileishmanial activity.

Conclusion:

This review explores the current evidence for the treatment of leishmaniases using nanoscale drug delivery systems (specifically lipid-, polymer- and metal-based systems) and encourages further development of the aforementioned nanotechnologies for treatment of Leishmania.

A chloroquinoline derivate presents effective in vitro and in vivo antileishmanial activity against Leishmania species that cause tegumentary and visceral leishmaniasis

The identification of new therapeutics to treat leishmaniasis is desirable, since available drugs are toxic and present high cost and/or poor availability. Therefore, the discovery of safer, more effective and selective pharmaceutical options is of utmost importance. Efforts towards the development of new candidates based on molecule analogs with known biological functions have been an interesting and cost-effective strategy. In this context, quinoline derivatives have proven to be effective biological activities against distinct diseases. In the present study, a new chloroquinoline derivate, AM1009, was in vitro tested against two Leishmania species that cause leishmaniasis. The present study analyzed the necessary inhibitory concentration to preclude 50% of the Leishmania promastigotes and axenic amastigotes (EC₅₀ value), as well as the inhibitory concentrations to preclude 50% of the murine macrophages and human red blood cells (CC₅₀ and RBC₅₀ values, respectively). In addition, the treatment of infected macrophages and the inhibition of infection using pre-treated parasites were also investigated, as was the mechanism of action of the molecule in L. amazonensis. To investigate the in vivo therapeutic effect, BALB/c mice were infected with L. amazonensis and later treated with AM1009. Parasitological and immunological parameters were also evaluated. Clioquinol, a known antileishmanial quinoline derivate, and amphotericin B (AmpB), were used as molecule and drug controls, respectively. Results in both in vitro and in vivo experiments showed a better and more selective action of AM1009 to kill the in vitro parasites, as well as in treating infected mice, when compared to results obtained using clioquinol or AmpB. AM1009-treated animals presented significantly lower average lesion diameter and parasite burden in the infected tissue and organs evaluated in this study, as well as a more polarized antileishmanial Th1 immune response and low renal and hepatic toxicity. This result suggests that AM1009 should be considered a possible therapeutic target to be evaluated in future studies for treatment against leishmaniasis.

Potential of Pluronics® P-123 and F-127 as nanocarriers of anti-Leishmania chemotherapy

Leishmaniasis is a neglected disease and drugs approved for its treatment often lead to abandonment, failure of therapy and even death. Photodynamic therapy (PDT) has been shown to be a promising, non-invasive and selective for a target region without requiring high-cost technology. Usually, it is employed a photosensitizing agent (PS) incorporated into nanoparticles (NP). Pluronics^® P-123 and F-127 micelles are very interesting aqueous NP promoting efficient and selective delivery and less adverse effects. This study aimed to detect the activity of Pluronics^® P-123 and F-127 themselves since there is a scarcity of data on these NP activities without drugs incorporation. This study evaluated, in vitro, the activity of Pluronics^® against promastigotes and amastigotes of Leishmania amazonensis and also their cytotoxicities. Additionally, the determination of the mitochondria membrane potential in promastigotes, internalization of these Pluronics^® in the parasite membrane and macrophages and its stability in the culture medium was evaluated. Results showed that Pluronics^® did not cause significant damage to human red cells and promastigotes. The P-123 and F-127 inhibited the survival rate of L. amazonensis amastigotes, and also presented loss of mitochondrial membrane potential on promastigotes. The Pluronics^® showed low cytotoxic activity on J774A.1 macrophages, while only P-123 showed moderate cytotoxicity for BALB/c macrophages. The stability of P-123 and F-127 in culture medium was maintained for ten days. In conclusion, the NP studied can be used for incorporating potent leishmanicidal chemotherapy, due to their selectivity towards macrophages, being a promising system for the treatment of cutaneous leishmaniasis.

In vitro and in vivo antileishmanial activity of a fluoroquinoline derivate against Leishmania infantum and Leishmania amazonensis species

New therapeutics against leishmaniasis are desirable, since the current drugs applied against this disease complex presents problems, such as the toxicity, high cost and/or parasite resistance. In the present study, a new fluoroquinoline derivate, namely 7-chloro-N-(4-fluorophenethyl)quinolin-4-amine or GF1061, was evaluated regarding to its in vitro antileishmanial action against Leishmania infantum and L. amazonensis species, as well as by its toxicity in mammalian cells and efficacy in the treatment of infected macrophages. The mechanism of action of this molecule in L. amazonensis and the therapeutic efficacy in infected BALB/c mice were also evaluated. Results showed that GF1061 was effective against both parasite species, showing selectivity index (SI) of 38.7 and 42.7 against L. infantum and L. amazonensis promastigotes, respectively, and of 45.0 and 48.9 against the amastigotes, respectively. Amphotericin B (AmpB), used as control, showed SI values of 6.6 and 8.8 against L. infantum and L. amazonensis promastigotes, respectively, and of 2.2 and 2.7 against the amastigotes, respectively. The molecule was effective in treat infected macrophages, as well as it induced alterations in the mitochondrial membrane potential, increase in the reactive oxygen species production, and in the cell integrity of the parasites. Regarding to the in vivo experiments, BALB/c mice (n = 8 per group) were subcutaneously infected with 10⁶L. amazonensis stationary promastigotes and, 60 days post-infection, they received saline or were treated during 10 days, once a day, with AmpB (1 mg/kg body weight) or GF1061 (5 mg/kg body weight). One day after the treatment, the infected tissue, spleen, liver, and draining lymph node (dLN) of the animals were collected, and the parasite load was evaluated. GF1061-treated mice, as compared to the saline and AmpB groups, showed significant reductions in the parasitism in the infected tissue (66% and 62%, respectively), liver (69% and 44%, respectively), spleen (71% and 38%, respectively), and dLN (72% and 48%, respectively). In conclusion, results suggested that GF1061 may be considered as a possible therapeutic target to be evaluated against leishmaniasis in other mammalian hosts.

Nanoparticulate drug delivery systems for the treatment of neglected tropical protozoan diseases

Neglected Tropical Diseases (NTDs) comprise of a group of seventeen infectious conditions endemic in many developing countries. Among these diseases are three of protozoan origin, namely leishmaniasis, Chagas disease, and African trypanosomiasis, caused by the parasites Leishmania spp., Trypanosoma cruzi, and Trypanosoma brucei respectively. These diseases have their own unique challenges which are associated with the development of effective prevention and treatment methods. Collectively, these parasitic diseases cause more deaths worldwide than all other NTDs combined. Moreover, many current therapies for these diseases are limited in their efficacy, possessing harmful or potentially fatal side effects at therapeutic doses. It is therefore imperative that new treatment strategies for these parasitic diseases are developed. Nanoparticulate drug delivery systems have emerged as a promising area of research in the therapy and prevention of NTDs. These delivery systems provide novel mechanisms for targeted drug delivery within the host, maximizing therapeutic effects while minimizing systemic side effects. Currently approved drugs may also be repackaged using these delivery systems, allowing for their potential use in NTDs of protozoan origin. Current research on these novel delivery systems has provided insight into possible indications, with evidence demonstrating their improved ability to specifically target pathogens, penetrate barriers within the host, and reduce toxicity with lower dose regimens. In this review, we will examine current research on these delivery systems, focusing on applications in the treatment of leishmaniasis, Chagas disease, and African trypanosomiasis. Nanoparticulate systems present a unique therapeutic alternative through the repositioning of existing medications and directed drug delivery.

Antileishmanial Activity, Cytotoxicity and Mechanism of Action of Clioquinol Against Leishmania infantum and Leishmania amazonensis Species

In this study, a quinoline derivate, clioquinol (5-chloro-7-iodoquinolin-8-ol), was evaluated against Leishmania amazonensis and Leishmania infantum promastigotes and amastigotes. The cytotoxicity in murine macrophages and human red blood cells, as well as the efficacy in treating infected macrophages and the inhibition of infection using pre-treated parasites were also evaluated. Results showed that clioquinol inhibited L. amazonensis and L. infantum promastigotes with effective concentration 50% (EC₅₀ ) values of 2.55 ± 0.25 and 1.44 ± 0.35 μg/mL, respectively, and of 1.88 ± 0.13 and 0.98 ± 0.17 μg/mL against axenic amastigotes, respectively. The cytotoxic EC₅₀ concentrations of clioquinol in murine macrophages and human red blood cells were, respectively, 255 ± 23 and 489 ± 20 μg/mL. With these results, the selectivity index was calculated, showing values of 99.9 and 177.1 against promastigotes, respectively, and of 135.6 and 260.1 against axenic amastigotes, respectively. Significant reductions in the percentage of infected macrophages after treatment using clioquinol were also observed, as well as when parasites were pre-treated with clioquinol and used to infect murine macrophages. The mechanism of action of clioquinol was investigated in L. amazonensis, and results revealed morphological and biochemical alterations in the clioquinol-treated parasites, including reduction in cell volume, loss of mitochondrial membrane potential, increase in the ROS production and rupture of the plasma membrane. The externalization of phosphatidylserine (PS) at the cell surface was evaluated in treated parasites that had been doubly labelled with annexin and propidium iodide (PI). The results showed no significant difference for PS exposure when compared to the untreated control, although a significant increase in the PI/annexin V-labelled cell population was found in the treated parasites. Results suggest that clioquinol induces a discontinuity of the parasite membrane, possibly related to a characteristic event of cell death caused by necrosis. This study demonstrates, for the first time, the antileishmanial activity of clioquinol against two relevant Leishmania species and suggests that the mitochondria of the parasites may be a possible biological target leading to parasite necrosis. Our findings suggest that clioquinol may have a potential application in treatment of leishmaniasis and further studies should be performed in infected mammalian hosts.

Comparing the therapeutic efficacy of different amphotericin B-carrying delivery systems against visceral leishmaniasis

Amphotericin B (Amp) has been well-successfully used to treat against Leishmania infection, although high toxicity has been found in patients. In the present study, Amp was administered in Leishmania infantum-infected BALB/c mice by three distinct delivery systems aiming to compare their efficacy against challenge infection, as well as their side effects in a murine visceral leishmaniasis (VL) model. This product was administered in a Poloxamer P407 (Pluronic^® F127)-based polymeric micelle system (Amp/M), in the Ambisome^® formulation (Lip-Amp) or in a free format (free Amp). Glucantime^® (Gluc) was used as a comparative drug. Aiming to evaluate different endpoints of the treatments, the efficacy of the compounds was investigated one and 15-days after the therapeutic regimens, determining the parasite load by a limiting dilution assay and a quantitative PCR (qPCR) technique, as well as evaluating the immune response generated in the infected and treated animals. In the results, Amp/M or Lip-Amp-treated mice presented the best outcomes, since significant parasite load reductions were found in the evaluated organs, as well as a parasite-specific Th1 immune response was observed in the animals. In addition, no hepatic or renal damage was found in these mice. On the other hand, free Amp or Gluc induced toxicity in the animals, which was associated with a low Th1 immune response. Comparatively, Amp/M was the most effective drug in our experimental model, and results showed that the Amp-carrying system could be considered as a future alternative in studies against VL.

Antileishmanial activity of a naphthoquinone derivate against promastigote and amastigote stages of Leishmania infantum and Leishmania amazonensis and its mechanism of action against L. amazonensis species

Leishmaniasis has become a significant public health issue in several countries in the world. New products have been identified to treat against the disease; however, toxicity and/or high cost is a limitation. The present work evaluated the antileishmanial activity of a new naphthoquinone derivate, Flau-A [2-(2,3,4-tri-O-acetyl-6-deoxy-β-L-galactopyranosyloxy)-1,4-naphthoquinone], against promastigote and amastigote-like stages of Leishmania amazonensis and L. infantum. In addition, the cytotoxicity in murine macrophages and human red cells was also investigated. The mechanism of action of Flau-A was assessed in L. amazonensis as well as its efficacy in treating infected macrophages and inhibiting infection of pretreated parasites. Results showed that Flau-A was effective against promastigotes and amastigote-like forms of both parasite species, as well as showed low toxicity in mammalian cells. Results also highlighted the morphological and biochemical alterations induced by Flau-A in L. amazonensis, including loss of mitochondrial membrane potential, as well as increased reactive oxygen species production, cell shrinkage, and alteration of the plasma membrane integrity. The present study demonstrates for the first time the antileishmanial activity of Flau-A against two Leishmania species and suggests that the mitochondria of the parasites may be the main target organelle. Data shown here encourages the use of this molecule in new studies concerning treatment against Leishmania infection in mammalian hosts.

Nanostructured delivery systems with improved leishmanicidal activity: a critical review

Leishmaniasis is a vector-borne zoonotic disease caused by protozoan parasites of the genus Leishmania, which are responsible for numerous clinical manifestations, such as cutaneous, visceral, and mucocutaneous leishmaniasis, depending on the site of infection for particular species. These complexities threaten 350 million people in 98 countries worldwide. Amastigotes living within macrophage phagolysosomes are the principal target of antileishmanial treatment, but these are not an easy target as drugs must overcome major structural barriers. Furthermore, limitations on current therapy are related to efficacy, toxicity, and cost, as well as the length of treatment, which can increase parasitic resistance. Nanotechnology has emerged as an attractive alternative as conventional drugs delivered by nanosized carriers have improved bioavailability and reduced toxicity, together with other characteristics that help to relieve the burden of this disease. The significance of using colloidal carriers loaded with active agents derives from the physiological uptake route of intravenous administered nanosystems (the phagocyte system). Nanosystems are thus able to promote a high drug concentration in intracellular mononuclear phagocyte system (MPS)-infected cells. Moreover, the versatility of nanometric drug delivery systems for the deliberate transport of a range of molecules plays a pivotal role in the design of therapeutic strategies against leishmaniasis. This review discusses studies on nanocarriers that have greatly contributed to improving the efficacy of antileishmaniasis drugs, presenting a critical review and some suggestions for improving drug delivery.