Advances in Development of New Treatment for Leishmaniasis

Determination of key hub genes in Leishmaniasis as potential factors in diagnosis and treatment based on a bioinformatics study

Leishmaniasis is an infectious disease caused by protozoan parasites from different species of leishmania. The disease is transmitted by female sandflies that carry these parasites. In this study, datasets on leishmaniasis published in the GEO database were analyzed and summarized. The analysis in all three datasets (GSE43880, GSE55664, and GSE63931) used in this study has been performed on the skin wounds of patients infected with a clinical form of leishmania (Leishmania braziliensis), and biopsies have been taken from them. To identify differentially expressed genes (DEGs) between leishmaniasis patients and controls, the robust rank aggregation (RRA) procedure was applied. We performed gene functional annotation and protein-protein interaction (PPI) network analysis to demonstrate the putative functionalities of the DEGs. The study utilized Molecular Complex Detection (MCODE), Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) to detect molecular complexes within the protein-protein interaction (PPI) network and conduct analyses on the identified functional modules. The CytoHubba plugin's results were paired with RRA analysis to determine the hub genes. Finally, the interaction between miRNAs and hub genes was predicted. Based on the RRA integrated analysis, 407 DEGs were identified (263 up-regulated genes and 144 down-regulated genes). The top three modules were listed after creating the PPI network via the MCODE plug. Seven hub genes were found using the CytoHubba app and RRA: CXCL10, GBP1, GNLY, GZMA, GZMB, NKG7, and UBD. According to our enrichment analysis, these functional modules were primarily associated with immune pathways, cytokine activity/signaling pathways, and inflammation pathways. However, a UBD hub gene is interestingly involved in the ubiquitination pathways of pathogenesis. The mirNet database predicted the hub gene's interaction with miRNAs, and results revealed that several miRNAs, including mir-146a-5p, crucial in fighting pathogenesis. The key hub genes discovered in this work may be considered as potential biomarkers in diagnosis, development of agonists/antagonist, novel vaccine design, and will greatly contribute to clinical studies in the future.

Chitosan/collagen biomembrane loaded with 2,3-dihydrobenzofuran for the treatment of cutaneous Leishmaniasis

In this work, chitosan/collagen-based membranes loaded with 2,3-dihydrobenzofuran (2,3-DHB) were developed through a simple solvent-casting procedure for use in the treatment of cutaneous Leishmaniasis. The obtained membranes were characterized by elemental analysis, FTIR, TG, DSC, and XRD. Porosity, swelling, mechanical properties, hydrophilicity, and antioxidant activity were analyzed. In addition, assessment to the biocompatibility, through fibroblasts/keratinocytes and in vitro wound healing essays were performed. The obtained results show that the new 2,3-DHB loaded chitosan/collagen membrane presented high porosity and swelling capacity as well as maximum strength, hydrophilicity, and antioxidant activity higher in relation to the control. The tests of antileishmanial activity and the AFM images demonstrate great efficacy of inhibition growth of the parasite, superior to those from the standard therapeutic agent that is currently used: Amphotericin B. The new membranes are biocompatible and stimulated the proliferation of keratinocytes. SEM images clearly demonstrate that fibroblasts were able to adhere, maintained their characteristic morphology. The healing test evidenced that the membranes have adequate environment for promoting cell proliferation and growth. As the conventional treatments often use drugs with high toxicity, the as-developed new membranes proved to be excellent candidate to treat cutaneous Leishmaniasis and can be clearly indicated for further advanced studies in vivo.

Synthesis and in vitro evaluation shows disquaramide compounds are a promising class of anti-leishmanial drugs

An increasing number of treatment failures with current pharmaceutics, as well as a lack of a vaccine, demonstrates the need to develop new treatment options for leishmaniasis. Herein, we describe the synthesis and in vitro analysis of 24 disquaramide compounds targeting the Leishmania major parasite. Of the compounds that were evaluated, six of them ( 13 , 19 , 20 , 22 , 24 , and 26 ) were capable of significantly decreasing the number of parasites by up to 42% compared to the control by day four. This demonstrates that disquaramides either impair parasite replication or have leishmancidal effects. Additionally, none of the disquaramide compounds tested displayed host cell cytotoxicity. These experiments provide evidence that disquaramides have the potential to be effective anti-leishmanial therapeutics.

Intraperitoneal Administration of 17-DMAG as an Effective Treatment against Leishmania braziliensis Infection in BALB/c Mice: A Preclinical Study

BACKGROUND

Leishmaniasis is a significant global public health issue that is caused by parasites from Leishmania genus. With limited treatment options and rising drug resistance, there is a pressing need for new therapeutic approaches. Molecular chaperones, particularly Hsp90, play a crucial role in parasite biology and are emerging as promising targets for drug development.

OBJECTIVE

This study evaluates the efficacy of 17-DMAG in treating BALB/c mice from cutaneous leishmaniasis through in vitro and in vivo approaches.

MATERIALS AND METHODS

We assessed 17-DMAG's cytotoxic effect on bone marrow-derived macrophages (BMMΦ) and its effects against L. braziliensis promastigotes and intracellular amastigotes. Additionally, we tested the compound's efficacy in BALB/c mice infected with L. braziliensis via intraperitoneal administration to evaluate the reduction in lesion size and the decrease in parasite load in the ears and lymph nodes of infected animals.

RESULTS

17-DMAG showed selective toxicity [selective index = 432) towards Leishmania amastigotes, causing minimal damage to host cells. The treatment significantly reduced lesion sizes in mice and resulted in parasite clearance from ears and lymph nodes. It also diminished inflammatory responses and reduced the release of pro-inflammatory cytokines (IL-6, IFN-γ, TNF) and the regulatory cytokine IL-10, underscoring its dual leishmanicidal and anti-inflammatory properties.

CONCLUSIONS

Our findings confirm the potential of 17-DMAG as a viable treatment for cutaneous leishmaniasis and support further research into its mechanisms and potential applications against other infectious diseases.

Pharmacokinetics, Dose-Proportionality, and Tolerability of Intravenous Tanespimycin (17-AAG) in Single and Multiple Doses in Dogs: A Potential Novel Treatment for Canine Visceral Leishmaniasis

In the New World, dogs are considered the main reservoir of visceral leishmaniasis (VL). Due to inefficacies in existing treatments and the lack of an efficient vaccine, dog culling is one of the main strategies used to control disease, making the development of new therapeutic interventions mandatory. We previously showed that Tanespimycin (17-AAG), a Hsp90 inhibitor, demonstrated potential for use in leishmaniasis treatment. The present study aimed to test the safety of 17-AAG in dogs by evaluating plasma pharmacokinetics, dose-proportionality, and the tolerability of 17-AAG in response to a dose-escalation protocol and multiple administrations at a single dose in healthy dogs. Two protocols were used: Study A: four dogs received variable intravenous (IV) doses (50, 100, 150, 200, or 250 mg/m2) of 17-AAG or a placebo (n = 4/dose level), using a cross-over design with a 7-day "wash-out" period; Study B: nine dogs received three IV doses of 150 mg/m2 of 17-AAG administered at 48 h intervals. 17-AAG concentrations were determined by a validated high-performance liquid chromatographic (HPLC) method: linearity (R2 = 0.9964), intra-day precision with a coefficient of variation (CV) ≤ 8%, inter-day precision (CV ≤ 20%), and detection and quantification limits of 12.5 and 25 ng/mL, respectively. In Study A, 17-AAG was generally well tolerated. However, increased levels of liver enzymes-alanine aminotransferase (ALT), aspartate aminotransferase (AST), and gamma-glutamyl transferase (GGT)-and bloody diarrhea were observed in all four dogs receiving the highest dosage of 250 mg/m2. After single doses of 17-AAG (50-250 mg/m2), maximum plasma concentrations (Cmax) ranged between 1405 ± 686 and 9439 ± 991 ng/mL, and the area under the curve (AUC) plotting plasma concentration against time ranged between 1483 ± 694 and 11,902 ± 1962 AUC 0-8 h μg/mL × h, respectively. Cmax and AUC parameters were dose-proportionate between the 50 and 200 mg/m2 doses. Regarding Study B, 17-AAG was found to be well tolerated at multiple doses of 150 mg/m2. Increased levels of liver enzymes-ALT (28.57 ± 4.29 to 173.33 ± 49.56 U/L), AST (27.85 ± 3.80 to 248.20 ± 85.80 U/L), and GGT (1.60 ± 0.06 to 12.70 ± 0.50 U/L)-and bloody diarrhea were observed in only 3/9 of these dogs. After the administration of multiple doses, Cmax and AUC 0-48 h were 5254 ± 2784 μg/mL and 6850 ± 469 μg/mL × h in plasma and 736 ± 294 μg/mL and 7382 ± 1357 μg/mL × h in tissue transudate, respectively. In conclusion, our results demonstrate the potential of 17-AAG in the treatment of CVL, using a regimen of three doses at 150 mg/m2, since it presents the maintenance of high concentrations in subcutaneous interstitial fluid, low toxicity, and reversible hepatotoxicity.

Practical Synthesis of 6-Amino-1-hydroxy-2,1-benzoxaborolane: A Key Intermediate of DNDI-6148

Visceral leishmaniasis (VL), a parasitic, poverty-linked, neglected disease, is endemic across multiple regions of the world and fatal if untreated. There is an urgent need for a better and more affordable treatment for VL. DNDI-6148 is a promising drug candidate being evaluated for the treatment of VL; however, the current process for producing the key intermediate of DNDI-6148, 6-amino-1-hydroxy-2,1-benzoxaborolane, is expensive and difficult to scale up. Herein, we describe two practical approaches to synthesizing 6-amino-1-hydroxy-2,1-benzoxaborolane from inexpensive and readily available raw materials. Starting with 4-tolunitrile, the first approach is a five-step sequence involving a Hofmann rearrangement, resulting in an overall yield of 40%. The second approach utilizes 2-methyl-5-nitroaniline as the starting material and features borylation of aniline and continuous flow hydrogenation as the key steps, with an overall yield of 46%. Both routes bypass the nitration of 1-hydroxy-2,1-benzoxaborolane, which is challenging and expensive to scale. In particular, the second approach is more practical and scalable because of the mild operating conditions and facile isolation process.

Screening of traditional medicinal plant extracts and compounds identifies a potent anti-leishmanial diarylheptanoid from Siphonochilus aethiopicus

Available anti-leishmanial drugs are associated with toxic side effects, necessitating the search for safe and effective alternatives. This study is focused on identifying traditional medicinal plant natural products for anti-leishmanial potential and possible mechanism of action. Compounds S and T. cordifolia residual fraction (TC-5) presented the best anti-leishmanial activity (IC50: 0.446 and 1.028 mg/ml) against promastigotes at 48 h and less cytotoxicity to THP-1 macrophages. These test agents elicited increased expression of pro-inflammatory cytokines; TNFα and IL-12. In infected untreated macrophages, NO release was suppressed but was significantly (p < 0.05) increased in infected cells treated with compound S. Importantly, Compound S was found to interact with LdTopoIIdimer in silico, resulting in a likely reduced ability of nucleic acid (dsDNA)-remodelling and, as a result, parasite proliferation in vitro. Thereby, Compound S possesses anti-leishmanial activity and this effect occurs via a Th1-mediated pro-inflammatory response. An increase in NO release and its inhibitory effect on LdTopoII may also contribute to the anti-leishmanial effect of compound S. These results show the potential of this compound as a potential starting point for the discovery of novel anti-leishmanial leads.Communicated by Ramaswamy H. Sarma.

Antileishmanial and Antitrypanosomes Drugs for the Current Century

Human infections by trypanosomatids are widely distributed and prevalent in the tropical and subtropical regions. Diseases caused by Trypanosoma and Leishmania have variable clinical outcomes, ranging from self-healing to fatality, and are considered Neglected Tropical Diseases (NTD). In addition, animal trypanosomiases have a significant impact on animal health and production, apart from their potential role as reservoirs in zoonotic species. Control of these infections is progressing and, in some cases (such as human African trypanomiasis (HAT)), significant reductions have been achieved. In the absence of effective vaccination, chemotherapy is the most used control method. Unfortunately, the therapeutic arsenal is scarce, old, and of variable efficacy, and reports of resistance to most antiparasitic agents have been published. New drugs, formulations, or combinations are needed to successfully limit the spread and severity of these diseases within a One Health framework. In this Special Issue, contributions regarding the identification and validation of drug targets, underlying mechanisms of action and resistance, and potential new molecules are presented. These research contributions are complemented by an update revision of the current chemotherapy against African Trypanosoma species, and a critical review of the shortcomings of the prevailing model of drug discovery and development.

In vitro effect of alpha-bisabolol and its synthetic derivatives on macrophages, promastigotes, and amastigotes of Leishmania amazonensis and Leishmania infantum

Cutaneous and visceral leishmaniasis are public health problems in Africa, Asia, Europe, and America. The treatment has a high cost and toxicity. Thus, this work aims to evaluate the leishmanicidal activity of alpha-bisabolol and its three synthetic derivatives, P1, P2, and P3, on the promastigotes and amastigotes Leishmania infantum and L. amazonensis forms. Alpha-bisabolol showed the lowest IC50 with 3.43 for L. amazonensis promastigotes, while P1 was the most toxic for L. infantum with an IC50 of 9.10. The derivative P3 was better for the amastigote form, with an IC50 of 3.39 for L. amazonensis. All the compounds effectively decreased the intracellular load of amastigote and its ability to turn promastigote again. Thus, alpha-bisabolol and its three synthetic derivatives were effective in their leishmanicidal activity. Therefore, it can be an option for developing new treatments against leishmaniasis.

In Silico Exploration of the Trypanothione Reductase (TryR) of L. mexicana

Human leishmaniasis is a neglected tropical disease which affects nearly 1.5 million people every year, with Mexico being an important endemic region. One of the major defense mechanisms of these parasites is based in the polyamine metabolic pathway, as it provides the necessary compounds for its survival. Among the enzymes in this route, trypanothione reductase (TryR), an oxidoreductase enzyme, is crucial for the Leishmania genus' survival against oxidative stress. Thus, it poses as an attractive drug target, yet due to the size and features of its catalytic pocket, modeling techniques such as molecular docking focusing on that region is not convenient. Herein, we present a computational study using several structure-based approaches to assess the druggability of TryR from L. mexicana, the predominant Leishmania species in Mexico, beyond its catalytic site. Using this consensus methodology, three relevant pockets were found, of which the one we call σ-site promises to be the most favorable one. These findings may help the design of new drugs of trypanothione-related diseases.

Investigating the role of Sterol C24-Methyl transferase mutation on drug resistance in leishmaniasis and identifying potential inhibitors

Leishmaniasis is a fatal disease caused by the leishmania parasite. For the survival of the leishmania parasite, Sterol C24-Methyl Transferase (SMT) is essential which is an enzyme of the ergosterol pathway. SMT protein mutation is responsible for Amphotericin-B drug resistance in Leishmania, which is the main treatment for visceral leishmaniasis. Amphotericin-B resistance is caused by three mutated residues V131I, V321I and F72C. The underlying mechanisms and structural changes in SMT enzymes responsible for resistance due to mutation are still not well understood. In the current study, the potential mechanism of resistance due to these mutations and the structure variation of wild and mutant SMT proteins were investigated through molecular dynamics simulations and molecular docking analysis. The results showed that AmB established strong bonding interaction with wild SMT as compare to mutants SMT. The binding energy calculation showed that binding energy of AmB with mutants SMT increases as compare to the wild SMT. Further structural based virtual screening was carried out to design potential inhibitors for the mutant SMT. On the basis of structural-based virtual screening four inhibitors (SANC01057, SANC00882, SANC00414, SANC01047) were computationally identified as potential mutant SMT (F72C) inhibitors. This work provides valuable information for improved management of drug resistant Leishmaniasis.Communicated by Ramaswamy H. Sarma.

Leishmania mexicana centrin knockout parasites promote M1-polarizing metabolic changes

Leishmaniasis is a tropical disease prevalent in 90 countries. Presently, there is no approved vaccine for human use. We developed a live attenuated L. mexicana Cen-/-(LmexCen-/-) strain as a vaccine candidate that showed excellent efficacy, characterized by reduced Th2 and enhanced Th1 responses in C57BL/6 and BALB/c mice, respectively, compared to wild-type L. mexicana (LmexWT) infection. Toward understanding the immune mechanisms of protection, we applied untargeted mass spectrometric analysis to LmexCen-/- and LmexWT infections. Data showed enrichment of the pentose phosphate pathway (PPP) in ears immunized with LmexCen-/-versus naive and LmexWT infection. PPP promotes M1 polarization in macrophages, suggesting a switch to a pro-inflammatory phenotype following LmexCen-/- inoculation. Accordingly, PPP inhibition in macrophages infected with LmexCen-/- reduced the production of nitric oxide and interleukin (IL)-1β, hallmarks of classical activation. Overall, our study revealed the immune regulatory mechanisms that may be critical for the induction of protective immunity.

Promising natural products for the treatment of cutaneous leishmaniasis: A review of in vitro and in vivo studies

Although there are available treatments for cutaneous leishmaniasis (CL), the drugs used are far from ideal, toxic, and costly, in addition to the challenge faced by the development of resistance. Plants have been used as a source of natural compounds with antileishmanial action. However, few have reached the market and become phytomedicines with registration in regulatory agencies. Difficulties related to the extraction, purification, chemical identification, efficacy, safety, and production in sufficient quantity for clinical studies, hinder the emergence of new effective phytomedicines against leishmaniasis. Despite the difficulties reported, the major research centers in the world see that natural products are a trend concerning the treatment of leishmaniasis. The present work consists of a literature review of articles with in vivo studies, covering the period from January 2011 to December 2022, providing an overview of promising natural products for CL treatment. The papers show encouraging antileishmanial action of natural compounds with reduced parasite load and lesion size in animal models, suggesting new strategies for the treatment of the disease. The results reported in this review show advances in using natural products as safe and effective formulations, which can stimulate clinical studies to establish clinical therapy. In conclusion, the information in this review article serves as a preliminary basis for establishing a therapeutic protocol for future clinical trials that can validate the safety and efficacy of natural compounds, providing the development of affordable and safe phytomedicines for the treatment of CL.

Recent Advances in Chemotherapeutics for Leishmaniasis: Importance of the Cellular Biochemistry of the Parasite and Its Molecular Interaction with the Host

Leishmaniasis, a category 1 neglected protozoan disease caused by a kinetoplastid pathogen called Leishmania, is transmitted through dipteran insect vectors (phlebotomine, sand flies) in three main clinical forms: fatal visceral leishmaniasis, self-healing cutaneous leishmaniasis, and mucocutaneous leishmaniasis. Generic pentavalent antimonials have long been the drug of choice against leishmaniasis; however, their success is plagued with limitations such as drug resistance and severe side effects, which makes them redundant as frontline therapy for endemic visceral leishmaniasis. Alternative therapeutic regimens based on amphotericin B, miltefosine, and paromomycin have also been approved. Due to the unavailability of human vaccines, first-line chemotherapies such as pentavalent antimonials, pentamidine, and amphotericin B are the only options to treat infected individuals. The higher toxicity, adverse effects, and perceived cost of these pharmaceutics, coupled with the emergence of parasite resistance and disease relapse, makes it urgent to identify new, rationalized drug targets for the improvement in disease management and palliative care for patients. This has become an emergent need and more relevant due to the lack of information on validated molecular resistance markers for the monitoring and surveillance of changes in drug sensitivity and resistance. The present study reviewed the recent advances in chemotherapeutic regimens by targeting novel drugs using several strategies including bioinformatics to gain new insight into leishmaniasis. Leishmania has unique enzymes and biochemical pathways that are distinct from those of its mammalian hosts. In light of the limited number of available antileishmanial drugs, the identification of novel drug targets and studying the molecular and cellular aspects of these drugs in the parasite and its host is critical to design specific inhibitors targeting and controlling the parasite. The biochemical characterization of unique Leishmania-specific enzymes can be used as tools to read through possible drug targets. In this review, we discuss relevant metabolic pathways and novel drugs that are unique, essential, and linked to the survival of the parasite based on bioinformatics and cellular and biochemical analyses.

Autophagy in protists and their hosts: When, how and why?

Pathogenic protists are a group of organisms responsible for causing a variety of human diseases including malaria, sleeping sickness, Chagas disease, leishmaniasis, and toxoplasmosis, among others. These diseases, which affect more than one billion people globally, mainly the poorest populations, are characterized by severe chronic stages and the lack of effective antiparasitic treatment. Parasitic protists display complex life-cycles and go through different cellular transformations in order to adapt to the different hosts they live in. Autophagy, a highly conserved cellular degradation process, has emerged as a key mechanism required for these differentiation processes, as well as other functions that are crucial to parasite fitness. In contrast to yeasts and mammals, protist autophagy is characterized by a modest number of conserved autophagy-related proteins (ATGs) that, even though, can drive the autophagosome formation and degradation. In addition, during their intracellular cycle, the interaction of these pathogens with the host autophagy system plays a crucial role resulting in a beneficial or harmful effect that is important for the outcome of the infection. In this review, we summarize the current state of knowledge on autophagy and other related mechanisms in pathogenic protists and their hosts. We sought to emphasize when, how, and why this process takes place, and the effects it may have on the parasitic cycle. A better understanding of the significance of autophagy for the protist life-cycle will potentially be helpful to design novel anti-parasitic strategies.

In Vitro Anti-Leishmanial Activity of Glucosinolate Fraction from Alyssum linifolium Steph. ex Willd (Brassicaceae)

Objectives

The intracellular parasitic protozoan, Leishmania spp., causes several forms of diseases in humans. Cytotoxicity and emergence of new strains resistance to the current anti-leishmanial drugs have encouraged researchers to focus on new resources. Glucosinolates (GSL) are found mainly in the Brassicaceae family with potential cytotoxic and anti-parasitic properties. The present study reports in vitro antileishmanial activity of the GSL fraction from Alyssum linifolium seeds against Leishmania major.

Materials and Methods

The GSL fraction was prepared by ion-exchange and reversed-phase chromatography. For the assessment of antileishmanial activity, the promastigotes and amastigotes of L. major were treated with different concentrations of the fraction (75-625 μg/mL).

Results

The IC₅₀ was 245 µg/mL for anti-promastigote effect of the GSL fraction and 250 µg/mL for its anti-amastigote effect that had a significant difference (p<0.05) with both glucantime and amphotericin B. The selectivity index of the GSL fraction (15.8), to glucantime and amphotericin B, was greater than 10, indicating the selective effect of this fraction against L. major amastigotes. Glucoiberverin was the major constituent of the GSL fraction characterized using nuclear magnetic resonance and electron ionization-mass spectrometry spectra. Based on gas chromatography-mass spectrometry data, iberverin and iberverin nitrile, the hydrolysis constituents from glucoiberverin, included 76.91% of the total seed volatiles.

Conclusion

The results suggest that GSLs like glucoiberverin could be considered a new promising candidate for further studies on antileishmanial activity.

The novel treatments based on tissue engineering, cell therapy and nanotechnology for cutaneous leishmaniasis

Cutaneous leishmaniasis (CL) is a global public health issue. Conventional treatments have substantial costs, side effects, and parasite resistance. Due to easy application and inexpensive cost, topical treatment is the optimal approach for CL. It could be used alone or with systemic treatments. Electrospun fibers as drug release systems in treating skin lesions have various advantages such as adjustable drug release rate, maintaining appropriate humidity and temperature, gas exchange, plasticity at the lesion site, similarity with the skin extracellular matrix (ECM) and drug delivery with high efficiency. Hydrogels are valuable scaffolds in the treatment of skin lesions. The important features of hydrogels include preserving unstable drugs from degradation, absorption of wound secretions, high biocompatibility, improving the re-epithelialization of the wound and preventing the formation of scars. One of the issues in local drug delivery systems for the skin is the low permeability of drugs in the skin. Polymeric scaffolds that are designed as microneedle patches can penetrate the skin and overcome this challenge. Also, drug delivery using nanocarriers increases the effectiveness of drugs in lower and more tolerable doses and reduces the toxicity of drugs. The application of cell therapy in the treatment of parasitic and infectious diseases has been widely investigated. The complexity of leishmaniasis treatment requires identifying new treatment options like cell therapy to overcome the disease. Topics investigated in this study include drug delivery systems based on tissue engineering scaffolds, nanotechnology and cell therapy-based studies to reduce the complications of CL.

Exploring the role of secretory proteins in the human infectious diseases diagnosis and therapeutics

Secretory proteins are playing important role during the host-pathogen interaction to develop the infection or protection into the cell. Pathogens developing infectious disease to human being are taken up by host macrophages or number of immune cells, play an important role in physiological, developmental and immunological function. At the same time, infectious agents are also secreting various proteins to neutralize the resistance caused by host cells and also helping the pathogens to develop the infection. Secretory proteins (secretome) are only developed at the time of host-pathogen interaction, therefore they become very important to develop the targeted and potential therapeutic strategies. Pathogen specific secretory proteins released during interaction with host cell provide opportunity to develop point of care and rapid diagnostic kits. Proteins secreted by pathogens at the time of interaction with host cell have also been found as immunogenic in nature and numbers of vaccines have been developed to control the spread of human infectious diseases. This chapter highlights the importance of secretory proteins in the development of diagnostic and therapeutic strategies to fight against human infectious diseases.

Insights into the drug screening approaches in leishmaniasis

Leishmaniasis, a tropically neglected disease, is responsible for the high mortality and morbidity ratio in poverty-stricken areas. Currently, no vaccine is available for the complete cure of the disease. Current chemotherapeutic regimens face the limitations of drug resistance and toxicity concerns indicating a great need to develop better chemotherapeutic leads that are orally administrable, potent, non-toxic, and cost-effective. The anti-leishmanial drug discovery process accelerated the desire for large-scale drug screening assays and high-throughput screening (HTS) technology to identify new chemo-types that can be used as potential drug molecules to control infection. Using the HTS approach, about one million compounds can be screened daily within the shortest possible time for biological activity using automation tools, miniaturized assay formats, and large-scale data analysis. Classical and modern in vitro screening assays have led to the progression of active compounds further to ex vivo and in vivo studies. In the present review, we emphasized on the HTS approaches employed in the leishmanial drug discovery program. Recent in vitro screening assays are widely explored to discover new chemical scaffolds. Developing appropriate experimental animal models and their related techniques is necessary to understand the pathophysiological processes and disease host responses, paving the way for unraveling novel therapies against leishmaniasis.

Leishmanicidal and cytotoxic activity of essential oil from the fruit peel of Myrciaria floribunda (H. West ex Willd.) O. Berg: Molecular docking and molecular dynamics simulations of its major constituent onto Leishmania enzyme targets

Cutaneous Leishmaniasis (CL) is a neglected disease characterized by highest morbidity rates worldwide. The available treatment for CL has several limitations including serious side effects and resistance to the treatment. Herein we aimed to evaluate the activity of essential oil from the peel of Myrciaria floribunda fruits (MfEO) on Leishmania amazonensis. The cytotoxic potential of MfEO on host mammalian cells was evaluated by MTT. The in vitro leishmanicidal effects of MfEO were investigated on the promastigote and intracellular amastigote forms. The ultrastructural changes induced by MfEO were evaluated by Scanning Electron Microscopy (SEM). The molecular docking of the major compounds δ-Cadinene, γ-Cadinene, γ-Muurolene, α-Selinene, α-Muurolene and (E)-Caryophyllene onto the enzymes trypanothione reductase (TreR) and sterol 14-alpha demethylase (C14DM) were performed. Our results showed that MfEO presented moderate cytotoxicity for Vero cells and macrophages. The MfEO inhibited the growth of promastigote and the survival of intracellular amastigotes, in a dose- and time- dependent way. The MfEO presented high selectivity towards amastigote forms, being 44.1 times more toxic for this form than to macrophages. Molecular docking analysis showed that the major compounds of MfEO interact with Leishmania enzymes and that δ-Cadinene (δ-CAD) presented favorable affinity energy values over TreR and C14DM enzymes, when compared with the other major constituents. Molecular dynamics (MD) simulation studies revealed a stable binding of δ-CAD with lowest binding free energy values in MMGBSA assay. Our results suggested that δ-CAD may be a potent inhibitor of TreR and C14DM enzymes. Communicated by Ramaswamy H. Sarma.

Present and future: infectious tropical travel rashes and the impact of climate change

In this article, we discuss pertinent cutaneous findings with which patients may present after travel to tropical destinations. We address arthropod-borne infectious diseases such as cutaneous leishmaniasis, Chagas disease, cutaneous larva migrans, and myiasis. We discuss other relevant diseases with cutaneous signs such as monkey pox and severe acute respiratory syndrome coronavirus 2. We provide clinicians with information regarding the background, diagnosis, treatment, and prevention of these tropical rashes. In addition, we address the impact that climate change will have on the temporal and geographic incidence of these rashes. Viral, fungal, and vector-borne diseases have seen a geographic expansion into more northern latitudes. Among these are tick-borne Lyme disease, aquatic snail-related seabather's eruption, and atopic dermatitis. As these diseases spread, we believe that the updated information within this article is significant to the practicing physician in today's warming world.

Rationally Designed Minimal Bioactive Domains of AS-48 Bacteriocin Homologs Possess Potent Antileishmanial Properties

Leishmaniasis, a category I neglected tropical disease, is a group of diseases caused by the protozoan parasite Leishmania species with a wide range of clinical manifestations. Current treatment options can be highly toxic and expensive, with drug relapse and the emergence of resistance. Bacteriocins, antimicrobial peptides ribosomally produced by bacteria, are a relatively new avenue for potential antiprotozoal drugs. Particular interest has been focused on enterocin AS-48, with previously proven efficacy against protozoan species, including Leishmania spp. Sequential characterization of enterocin AS-48 has illustrated that antibacterial bioactivity is preserved in linearized, truncated forms; however, minimal domains of AS-48 bacteriocins have not yet been explored against protozoans. Using rational design techniques to improve membrane penetration activity, we designed peptide libraries using the minimal bioactive domain of AS-48 homologs. Stepwise changes to the charge (z), hydrophobicity (H), and hydrophobic dipole moment (μH) were achieved through lysine and tryptophan substitutions and the inversion of residues within the helical wheel, respectively. A total of 480 synthetic peptide variants were assessed for antileishmanial activity against Leishmania donovani. One hundred seventy-two peptide variants exhibited 50% inhibitory concentration (IC50) values below 20 μM against axenic amastigotes, with 60 peptide variants in the nanomolar range. Nine peptide variants exhibited potent activity against intracellular amastigotes with observed IC50 values of <4 μM and limited in vitro host cell toxicity, making them worthy of further drug development. Our work demonstrates that minimal bioactive domains of naturally existing bacteriocins can be synthetically engineered to increase membrane penetration against Leishmania spp. with minimal host cytotoxicity, holding the promise of novel, potent antileishmanial therapies. IMPORTANCE Leishmaniasis is a neglected tropical disease caused by protozoan parasites of the genus Leishmania. There are three primary clinical forms, cutaneous, mucocutaneous, and visceral, with visceral leishmaniasis being fatal if left untreated. Current drug treatments are less than ideal, especially in resource-limited areas, due to the difficult administration and treatment regimens as well as the high cost and the emergence of drug resistance. Identifying potent antileishmanial agents is of the utmost importance. We utilized rational design techniques to synthesize enterocin AS-48 and AS-48-like bacteriocin-based peptides and screened these peptides against L. donovani using a fluorescence-based phenotypic assay. Our results suggest that bacteriocins, specifically these rationally designed AS-48-like peptides, are promising leads for further development as antileishmanial drugs.

Sterol profiling of Leishmania parasites using a new HPLC-tandem mass spectrometry-based method and antifungal azoles as chemical probes reveals a key intermediate sterol that supports a branched ergosterol biosynthetic pathway

Human leishmaniasis is an infectious disease caused by Leishmania protozoan parasites. Current chemotherapeutic options against the deadly disease have significant limitations. The ergosterol biosynthetic pathway has been identified as a drug target in Leishmania. However, remarkable differences in the efficacy of antifungal azoles that inhibit ergosterol biosynthesis have been reported for the treatment of leishmaniasis. To better understand the sterol biosynthetic pathway in Leishmania and elucidate the mechanism underlying the differential efficacy of antifungal azoles, we developed a new LC-MS/MS method to study sterol profiles in promastigotes of three Leishmania species, including two L. donovani, one L. major and one L. tarentolae strains. A combination of distinct precursor ion masses and LC retention times allowed for specific detection of sixteen intermediate sterols between lanosterol and ergosterol using the newly developed LC-MS/MS method. Although both posaconazole and fluconazole are known inhibitors of fungal lanosterol 14α-demethylase (CYP51), only posaconazole led to a substantial accumulation of lanosterol in azole-treated L. donovani promastigotes. Furthermore, a key intermediate sterol accumulated by 40- and 7-fold when these parasites were treated with posaconazole and fluconazole, respectively, which was determined as 4α,14α-dimethylzymosterol by high resolution mass spectrometry and NMR spectroscopy. The identification of 4α,14α-dimethylzymosterol supports a branched ergosterol biosynthetic pathway in Leishmania, where lanosterol C4- and C14-demethylation reactions occur in parallel rather than sequentially. Our results suggest that selective inhibition of leishmanial CYP51 is insufficient to effectively prevent parasite growth and dual inhibitors of both CYP51 and the unknown sterol C4-demethylase may be required for optimal antiparasitic effect.

Anti-leishmanial physalins-Phytochemical investigation, in vitro evaluation against clinical and MIL-resistant L. tropica strains and in silico studies

Cutaneous leishmaniasis (CL) is a major health problem in over 98 countries of the world, including Pakistan. The current treatments are associated with a number of adverse effects and availability problem of drugs. Therefore, there is an urgent need of easily available and cost effective treatments of CL- in Pakistan. The bioassay-guided fractionation and purification of crude extract of Physalis minima has led to the isolation of a new aminophysalin B (1), and eight known physalins, physalin B (2), 5ß,6ß-epoxyphysalin B (3), 5α-ethoxy-6ß-hydroxy-5,6-dihydrophysalin B (4), physalin H (5), 5ß,6ß-epoxyphysalin C (6), and physalin G (7), K (8), and D (9). It is worth noting that compound 1 is the second member of aminophysalin series, whereas compound 6 was fully characterized for the first time. The structures of compounds 1-9 were elucidated by spectroscopic techniques Whereas, the structural assignments of compounds 1 and 8 were also supported by single-crystal X-ray diffraction studies. The anti-leishmanial activity of isolated physlains 1-9 was evaluated against Leishmania major and Leishmania tropica promastigotes. Compounds 2, 3, and 5-7 (IC50 = 9.59 ± 0.27-23.76 ± 1.10 μM) showed several-fold more potent activity against L. tropca than tested drug miltefosine (IC50 = 42.75 ± 1.03 μm) and pentamidine (IC50 = 27.20 ± 0.01 μM). Whereas compounds 2, 3 and 5 (IC50 = 3.04 ± 1.12-3.76 ± 0.85 μM) were found to be potent anti-leishmanial agents against L. major, several fold more active than tested standard miltefosine (IC50 = 25.55 ± 1.03 μM) and pentamidine (IC50 = 27.20 ± 0.015 μM). Compounds 4 (IC50 = 74.65 ± 0.81 μM) and 7 (IC50 = 39.44 ± 0.65 μM) also showed potent anti-leishmanial ativity against the miltefosine-unresponsive L. tropica strain (MIL resistant) (miltefosine IC50 = 169.55 ± 0.78 μM). Molecular docking and predictive binding studies indicated that these inhibitors may act via targeting important enzymes of various metabolic pathways of the parasites.

Current Applications of Plant-Based Drug Delivery Nano Systems for Leishmaniasis Treatment

Leishmania is a trypanosomatid that causes leishmaniasis. It is transmitted to vertebrate hosts during the blood meal of phlebotomine sandflies. The clinical manifestations of the disease are associated with several factors, such as the Leishmania species, virulence and pathogenicity, the host-parasite relationship, and the host's immune system. Although its causative agents have been known and studied for decades, there have been few advances in the chemotherapy of leishmaniasis. The urgency of more selective and less toxic alternatives for the treatment of leishmaniasis leads to research focused on the study of new pharmaceuticals, improvement of existing drugs, and new routes of drug administration. Natural resources of plant origin are promising sources of bioactive substances, and the use of ethnopharmacology and folk medicine leads to interest in studying new medications from phytocomplexes. However, the intrinsic low water solubility of plant derivatives is an obstacle to developing a therapeutic product. Nanotechnology could help overcome these obstacles by improving the availability of common substances in water. To contribute to this scenario, this article provides a review of nanocarriers developed for delivering plant-extracted compounds to treat clinical forms of leishmaniasis and critically analyzing them and pointing out the future perspectives for their application.

The Effect of BTK Inhibitor Ibrutinib on Leishmania infantum Infection In Vitro

PURPOSE

Leishmaniasis is a neglected infectious disease affecting millions of people worldwide. Visceral leishmaniasis (VL), caused by Leishmania infantum and Leishmania donovani, is one of the main clinical forms of the disease and fatal if not treated promptly and properly. Despite being available for the last 70 years, current drugs used in the treatment of leishmaniasis have serious problems as they have high toxicity, require long-term administration and cause serious side-effects, leading to the emergence of resistant and relapse cases. Therefore, there is an urgent need for the discovery of novel antileishmanial molecules and the development of new treatment regimens. The drug used for chemotherapy of B-cell malignancies, Ibrutinib, an inhibitor of Bruton's Tyrosine Kinase (BTK), can offer a new therapeutic perspective due to the functions of BTK on intracellular signaling mechanism of macrophages, which are the primary resident cell for Leishmania. Hence, the study aimed to evaluate ibrutinib as a potential anti-Leishmanial drug.

METHOD

In this study, we evaluated the antileishmanial effect of Ibrutinib by in vitro L. infantum infection model using macrophages, with cell viability assay, parasite rescue assay, real-time qPCR.

RESULTS

We showed that Ibrutinib was significantly more effective than the Glucantime against L. infantum. In addition, our data revealed that Ibrutinib inhibited parasite growth and load without impairing macrophage viability.

CONCLUSIONS

Consequently, due to its efficacy and safety, Ibrutinib may be a promising candidate for the treatment of VL caused by L. infantum as a host-targeted drug.

Quantum Biochemistry Screening and In Vitro Evaluation of Leishmania Metalloproteinase Inhibitors

Leishmanolysin, also known as major promastigote protease (PSP) or gp63, is the most abundant surface glycoprotein of Leishmania spp., and has been extensively studied and recognized as the main parasite virulence factor. Characterized as a metalloprotease, gp63 can be powerfully inactivated in the presence of a metal chelator. In this study, we first used the structural parameters of a 7-hydroxycoumarin derivative, L1 compound, to evaluate the theoretical-computational experiments against gp63, comparing it with an available metal chelator already described. The methodology followed was (i) analysis of the three-dimensional structure of gp63 as well as its active site, and searching the literature and molecular databases for possible inhibitors; (ii) molecular docking simulations and investigation of the interactions in the generated protein-ligand complexes; and (iii) the individual energy of the gp63 amino acids that interacted most with the ligands of interest was quantified by ab initio calculations using Molecular Fraction with Conjugated Caps (MFCC). MFCC still allowed the final quantum balance calculations of the protein interaction to be obtained with each inhibitor candidate binder. L1 obtained the best energy quantum balance result with -2 eV, followed by DETC (-1.4 eV), doxycycline (-1.3 eV), and 4-terpineol (-0.6 eV), and showed evidence of covalent binding in the enzyme active site. In vitro experiments confirmed L1 as highly effective against L. amazonensis parasites. The compound also exhibited a low cytotoxicity profile against mammalian RAW and 3T3 cells lines, presenting a selective index of 149.19 and 380.64 µM, respectively. L1 induced promastigote forms' death by necrosis and the ultrastructural analysis revealed disruption in membrane integrity. Furthermore, leakage of the contents and destruction of the parasite were confirmed by Spectroscopy Dispersion analysis. These results together suggested L1 has a potential effect against L. amazonensis, the etiologic agent of diffuse leishmaniasis, and the only one that currently does not have a satisfactory treatment.

Aurothiomalate-Based Drugs as Potentially Novel Agents Against Leishmania major: A Mini Review

PURPOSE

Leishmaniasis is a major public health problem worldwide in many parts of the world. Current anti-leishmanial drugs have only limited clinical efficacy. Aurothiomalate derivatives are useful for treating rheumatoid arthritis, but have emerged as a promising therapeutic candidate for leishmaniasis. This paper gives a review of the literature about the usefulness of aurothiomalate derivatives against leishmaniasis.

METHODS

In this study, we reviewed the proposed mechanisms of action of aurothiomalate and related compounds on the metabolism of L. major and collected data by searching relevant articles.

RESULTS

Aurothiomalate-based drugs could be effective against leishmaniasis through two direct and indirect mechanisms: first, cytotoxic effects on parasites via thiomalate's false substrate role in the citric acid cycle against malate; and second, immunosuppressive and anti-inflammatory effects of aurothiomalate derivatives with prostaglandin production inhibitory effects.

CONCLUSIONS

The current study documented that aurothiomalate-based drugs could be effective against leishmaniasis through two direct and indirect mechanisms of action. Gold thiomalate as a promising hit should be evaluated against L. major in vitro and in vivo conditions in the future.

Effect of Synergism of Thalidomide and Liposomal Amphotericin-B on Leishmania tropica and Leishmania donovani Promastigote

This study aims to find safe and effective anti-leishmaniasis drugs; thus, the synergism between thalidomide and liposomal amphotericin-B was tested as antileishmanial on L. tropica and L. donovani promastigote in vitro. IC50, IC90 were determined at the Log phase of thalidomide and were (10), (25) µg/ml for L. tropica and (12.5), (30( µg/ml for L. donovani, Moreover IC50, IC90 were determined at Log phase of Liposomal amphotericin-B and were (5), (20) µg/ml for L. tropica and (5), (25) µg/ml for L. donovani. Additionally, synergistic effect IC50 of the two drugs were determined when Liposomal amphotericin-B fixed it, and thalidomide concentrations changed was (2.5+0.5) µg/ml on L. tropica and (2.5+1) µg/ml on L. donovan. When thalidomide was fixed, and Liposomal amphotericin-B was changed, it was (2.5+2) µg/ml for both L. tropica and L.donovani. The synergistic effect on the morphology of both promastigotes forms was observed. Keywords. Leishmaniasis, thalidomide, liposomal amphotericin-B, synergistic.

Different Drugs, Same End: Ultrastructural Hallmarks of Autophagy in Pathogenic Protozoa

Protozoan parasites interact with a wide variety of organisms ranging from bacteria to humans, representing one of the most common causes of parasitic diseases and an important public health problem affecting hundreds of millions of people worldwide. The current treatment for these parasitic diseases remains unsatisfactory and, in some cases, very limited. Treatment limitations together with the increased resistance of the pathogens represent a challenge for the improvement of the patient’s quality of life. The continuous search for alternative preclinical drugs is mandatory, but the mechanisms of action of several of these compounds have not been described. Electron microscopy is a powerful tool for the identification of drug targets in almost all cellular models. Interestingly, ultrastructural analysis showed that several classes of antiparasitic compounds induced similar autophagic phenotypes in trypanosomatids, trichomonadids, and apicomplexan parasites as well as in Giardia intestinalis and Entamoeba spp. with the presence of an increased number of autophagosomes as well as remarkable endoplasmic reticulum profiles surrounding different organelles. Autophagy is a physiological process of eukaryotes that maintains homeostasis by the self-digestion of nonfunctional organelles and/or macromolecules, limiting redundant and damaged cellular components. Here, we focus on protozoan autophagy to subvert drug effects, discussing its importance for successful chemotherapy.

Natural compounds based chemotherapeutic against Chagas disease and leishmaniasis: mitochondrion as a strategic target

Over the past years, natural products have been explored in order to find biological active substances to treat various diseases. Regarding their potential action against parasites such as trypanosomatids, specially Trypanosoma cruzi and Leishmania spp., much advance has been achieved. Extracts and purified molecules of several species from genera Piper, Tanacetum, Porophyllum, and Copaifera have been widely investigated by our research group and exhibited interesting antitrypanosomal and antileishmanial activities. These natural compounds affected different structures in parasites, and we believe that the mitochondrion is a strategic target to induce parasite death. Considering that these trypanosomatids have a unique mitochondrion, this cellular target has been extensively studied aiming to find more selective drugs, since the current treatment of these neglected tropical diseases has some challenges such as high toxicity and prolonged treatment time. Here, we summarise some results obtained with natural products from our research group and we further highlighted some strategies that must be considered to finally develop an effective chemotherapeutic agent against these parasites.

In vitro leishmanicidal activity of two cholesterol derivatives

We evaluated the leishmanicidal activity of commercially available 5α-cholest-7-en-3β-ol [5α-chol], (+)-4-cholesten-3-one [(+)-4-chol] and the equimolar mixture of the two of them in promastigotes and amastigotes of two different strains of Leishmania mexicana (LCL) and (DCL). The leishmanicidal effectiveness of these sterols was determined by promastigote growth-kinetic experiments and promastigote viability using the propidium iodide staining procedure. The proliferation test was performed using the CFSE (5-Carboxyfluorescein N-succinimidyl ester) staining of parasites at different time points. To determine the leishmanicidal effectiveness of these sterols in amastigotes, we evaluated parasite killing inside of macrophages at different time points. The trypan blue exclusion test was used to determine cytotoxicity of sterols in uninfected macrophages. We included in all experiments a control group of parasites treated with 2% DMSO (Dimethyl Sulfoxide) and another one treated with the reference drug sodium stibogluconate (Sb). Our results showed that the equimolar mixture at 2000 times lower concentration presented similar leishmanicidal activity as Sb. This mixture was similarly effective at 100 times lower concentration than individual sterols tested separately indicating the existence of a synergistic effect against LCL and DCL parasites. The therapeutic index of the equimolar mixture was 10,000-16,000 times higher than the one recorded by Sb and was not cytotoxic to macrophages. Therefore, the equimolar mixture of 5α-Chol and (+)-4-chol may represent a potential alternative for the treatment of cutaneous leishmaniasis.

Centrin-deficient Leishmania mexicana confers protection against New World cutaneous leishmaniasis

Leishmaniasis is a neglected protozoan disease affecting over 12 million people globally with no approved vaccines for human use. New World cutaneous leishmaniasis (CL) caused by L. mexicana is characterized by the development of chronic non-healing skin lesions. Using the CRISPR/Cas9 technique, we have generated live attenuated centrin knockout L. mexicana (LmexCen^-/-) parasites. Centrin is a cytoskeletal protein important for cellular division in eukaryotes and, in Leishmania, is required only for intracellular amastigote replication. We have investigated the safety and immunogenicity characteristics of LmexCen^-/- parasites by evaluating their survival and the cytokine production in bone-marrow-derived macrophages (BMDMs) and dendritic cells (BMDCs) in vitro. Our data shows that LmexCen^-/- amastigotes present a growth defect, which results in significantly lower parasitic burdens and increased protective cytokine production in infected BMDMs and BMDCs, compared to the wild type (WT) parasites. We have also determined the safety and efficacy of LmexCen^-/- in vivo using experimental murine models of L. mexicana. We demonstrate that LmexCen^-/- parasites are safe and do not cause lesions in susceptible mouse models. Immunization with LmexCen^-/- is also efficacious against challenge with WT L. mexicana parasites in genetically different BALB/c and C57BL/6 mouse models. Vaccinated mice did not develop cutaneous lesions, displayed protective immunity, and showed significantly lower parasitic burdens at the infection site and draining lymph nodes compared to the control group. Overall, we demonstrate that LmexCen^-/- parasites are safe and efficacious against New World cutaneous leishmaniasis in pre-clinical models.

Nanotechnological approaches for pentamidine delivery

Pentamidine (PTM), which is a diamine that is widely known for its antimicrobial activity, is a very interesting drug whose mechanism of action is not fully understood. In recent years, PTM has been proposed as a novel potential drug candidate for the treatment of mental illnesses, myotonic dystrophy, diabetes, and tumors. Nevertheless, the systemic administration of PTM causes severe side effects, especially nephrotoxicity. In order to efficiently deliver PTM and reduce its side effects, several nanosystems that take advantage of the chemical characteristics of PTM, such as the presence of two positively charged amidine groups at physiological pH, have been proposed as useful delivery tools. Polymeric, lipidic, inorganic, and other types of nanocarriers have been reported in the literature for PTM delivery, and they are all in different development phases. The available approaches for the design of PTM nanoparticulate delivery systems are reported in this review, with a particular emphasis on formulation strategies and in vitro/in vivo applications. Furthermore, a critical view of the future developments of nanomedicine for PTM applications, based on recent repurposing studies, is provided. Created with BioRender.com.

In Vitro Antileishmanial and Antitrypanosomal Activities of Plicataloside Isolated from the Leaf Latex of Aloe rugosifolia Gilbert & Sebsebe (Asphodelaceae)

Trypanosomiasis and leishmaniasis are among the major neglected diseases that affect poor people, mainly in developing countries. In Ethiopia, the latex of Aloe rugosifolia Gilbert & Sebsebe is traditionally used for the treatment of protozoal diseases, among others. In this study, the in vitro antitrypanosomal activity of the leaf latex of A. rugosifolia was evaluated against Trypanosoma congolense field isolate using in vitro motility and in vivo infectivity tests. The latex was also tested against the promastigotes of Leishmania aethiopica and L. donovani clinical isolates using alamar blue assay. Preparative thin-layer chromatography of the latex afforded a naphthalene derivative identified as plicataloside (2,8-O,O-di-(β-D-glucopyranosyl)-1,2,8-trihydroxy-3-methyl-naphthalene) by means of spectroscopic techniques (HRESI-MS, ¹H, ¹³C-NMR). Results of the study demonstrated that at 4.0 mg/mL concentration plicataloside arrested mobility of trypanosomes within 30 min of incubation period. Furthermore, plicataloside completely eliminated subsequent infectivity in mice for 30 days at concentrations of 4.0 and 2.0 mg/mL. Plicataloside also displayed antileishmanial activity against the promastigotes of L. aethopica and L. donovani with IC₅₀ values 14.22 ± 0.41 µg/mL (27.66 ± 0.80 µM) and 18.86 ± 0.03 µg/mL (36.69 ± 0.06 µM), respectively. Thus, plicataloside may be used as a scaffold for the development of novel drugs effective against trypanosomiasis and leishmaniasis.

First-in-class pyrido[2,3-d]pyrimidine-2,4(1H,3H)-diones against leishmaniasis and tuberculosis: Rationale, in vitro, ex vivo studies and mechanistic insights

Pyrido[2,3-d]pyrimidine-2,4(1H,3H)-diones were synthesized, for the first time, from indole chalcones and 6-aminouracil, and their ability to inhibit leishmaniasis and tuberculosis (Tb) infections was evaluated. The in vitro antileishmanial activity against promastigotes of Leishmania donovani revealed exceptional activities of compounds 3, 12 and 13, with IC₅₀ values ranging from 10.23 ± 1.50 to 15.58 ± 1.67 µg/ml, which is better than the IC₅₀ value of the standard drug pentostam of 500 μg/ml. The selectivity of the compounds towards Leishmania parasites was evaluated via ex vivo studies in Swiss albino mice. The efficiency of these compounds against Tb infection was then evaluated using the in vitro anti-Tb microplate Alamar Blue assay. Five compounds, 3, 7, 8, 9 and 12, showed MIC₁₀₀ values against the Mycobacterium tuberculosis H₃₇ Rv strain at 25 µg/ml, and compound 20 yielded an MIC₁₀₀ value of 50 µg/ml. Molecular modelling of these compounds highlighted interactions with binding sites of dihydrofolate reductase, pteridine reductase and thymidylate kinase, thus establishing the rationale of their pharmacological activity against both pathogens, which is consistent with the in vitro results. From the above results, it is clear that compounds 3 and 12 are promising lead candidates for Leishmania and Mycobacterium infections and may be promising for coinfections.

Microwave Assisted Biology-Oriented Drug Synthesis (BIODS) of NewN, N′-Disubstituted Benzylamine Analogous of 4-Aminoantipyrine against Leishmaniasis -In VitroAssay and In silico-Predicted Molecular Interactions with Key Metabolic Targets

Biology-Oriented Drug Synthesis (BIODS) deals with the simple chemical transformations on the commercially available drugs in order to enhance their new and diversified pharmacological profile. It opens new avenues for the rapid development of drug candidates for neglected tropical diseases (NTDs). Leishmaniasis is one of the NTDs which spread by the bite of sandflies (plebotomine). It ranges from cutaneous self-healing leishmaniasis to life threatening visceral leishmaniasis, known as kala-azar. The current treatment options include the use of pentamidine, miltefosine, and amphotericin B drugs. Unfortunately, all currently available drugs are associated with adverse effects, such as severe nephron- and cardiotoxicity, pancreatitis, and hepatotoxicity. This warrants the development of new drugs against leishmaniasis. Moreover, emergence of resistance against the current medications further worsens the conditions. With this objective, new N, N'-disubstituted benzylamine derivatives of ampyrone (4-aminoantipyrine) were synthesized by using ultrasonication, and microwave assistance. All derivatives were found to be new, except 1, 4, and 11. All the compounds were evaluated for their anti-leishmanial activity, and cellular cytotoxicity. Among them, compounds 4, 5, 8, and 9 showed a significant anti-leishmanial activity in vitro, in comparison to standard drug, miltefosine (IC₅₀ = 25.78 ± 0.2 µM). These compounds were also docked against various metabolic enzymes to predict their interactions and mechanism of action, and were found to act via targeting important enzymes of various metabolic pathways.

Heterocyclic Diamines with Leishmanicidal Activity

Leishmaniasis is one of the world's most neglected diseases with a worldwide prevalence of 12 million people. There are no effective human vaccines for its prevention, and outdated drugs hamper treatment. Therefore, research aimed at developing new therapeutic tools to fight leishmaniasis remains a crucial goal today. With this purpose in mind, here, we present 10 new compounds made up by linking alkylated ethylenediamine units to pyridine or quinoline heterocycles with promising in vitro and in vivo efficacy against promastigote and amastigote forms of Leishmania infantum, Leishmania donovani, and Leishmania braziliensis species. Three compounds (2, 4, and 5) showed a selectivity index much higher in the amastigote form than the reference drug glucantime. These three derivatives affected the parasite infectivity rates; the result was lower parasite infectivity rates than glucantime tested at an IC₂₅ dose. In addition, these derivatives were substantially more active against the three Leishmania species tested than glucantime. The mechanism of action of these compounds has been studied, showing alterations in glucose catabolism and leading to greater levels of iron superoxide dismutase inhibition. These molecules could be potential candidates for leishmaniasis chemotherapy due to their effectiveness and their ready synthesis.

Chalcones identify cTXNPx as a potential antileishmanial drug target

With current drug treatments failing due to toxicity, low efficacy and resistance; leishmaniasis is a major global health challenge that desperately needs new validated drug targets. Inspired by activity of the natural chalcone 2’,6’-dihydroxy-4’-methoxychalcone (DMC), the nitro-analogue, 3-nitro-2’,4’,6’- trimethoxychalcone (NAT22, 1c) was identified as potent broad spectrum antileishmanial drug lead. Structural modification provided an alkyne containing chemical probe that labelled a protein within the parasite that was confirmed as cytosolic tryparedoxin peroxidase (cTXNPx). Crucially, labelling is observed in both promastigote and intramacrophage amastigote life forms, with no evidence of host macrophage toxicity. Incubation of the chalcone in the parasite leads to ROS accumulation and parasite death. Deletion of cTXNPx, by CRISPR-Cas9, dramatically impacts upon the parasite phenotype and reduces the antileishmanial activity of the chalcone analogue. Molecular docking studies with a homology model of in-silico cTXNPx suggest that the chalcone is able to bind in the putative active site hindering access to the crucial cysteine residue. Collectively, this work identifies cTXNPx as an important target for antileishmanial chalcones.

Leishmaniasis is an insect vector-borne parasitic disease. With >350 million people world wide considered at risk, 12 million people currently infected and an economic cost that can be estimated in terms of >3.3 million working life years lost, leishmaniasis is a major global health challenge. The disease is of particular importance in Brazil. Current treatment of leishmaniasis is difficult requiring a long, costly course of drug treatment using old drugs with poor safety indications requiring close medical supervision. Moreover, resistance to current antileishmanials is growing, emphasising a major need for new drug targets. In earlier work we had identified a naturally inspired chalcone which had promising antileishmanial activity but with no known mode of action. In this work we use an analogue of this molecule as an activity based probe to identify a protein target of the chalcone. This protein, cTXNPx, has a major role in protecting the parasite against attack by reactive oxygen species in the host cell. By inhibiting this protein the parasite can no longer survive in the host. Collectively this work validates cTXNPx as a drug target with the chalcone as a lead structure for future drug discovery programmes.

Identification of potential antileishmanial agents via structure-based molecular simulations

Leishmaniasis is a parasitic disease with frequent annual incidence. An important issue in chemotherapy is the emergence of resistance, toxicity and lack of cost-effectiveness within current drugs. Therefore, it is of utmost importance to design effective drugs against disease. Current contribution was devoted to the in-silico analysis of binding a few flavonoids/alkaloids to relevant leishmanial targets. Docking scores were used to prioritize acquired affinities and top ranked binders were subjected to subsequent 100-ns MD simulation in explicit water. Binding trajectories revealed the tightest interaction modes for two flavonoid molecules (acerosin and nevadensin) in the uracil DNA glycolase (UDG) active site. Acerosin showed less conformational changes whereas, nevadensin interacted stably during longer simulation time. Conserved interactions of Gln205 and His331 to acerosin indicated their dominant biological role in complex stability. No conserved residues were perceived for nevadensin interactions and a completely new and stable binding conformation could be retrieved after 12 ns simulation. Moreover; acerosin was subjected to DFT analysis for pairwise decomposition evaluations of interacted residues. Although primary mechanisms of action are yet to be discovered, UDG may be a promising target for developing antileishmanial flavonoids.

An overview of the fatty acid biosynthesis in the protozoan parasite Leishmania and its relevance as a drug target against leishmaniasis

Leishmaniasis is one of the fast-growing parasitic diseases worldwide. The treatment of this fatal disease presents a daunting challenge because of its adverse effects, necessity for long-term treatment regime, unavailability of functional drugs, emergence of drug resistance and the related expenditure. This calls for an urgent need for novel drugs and the evaluation of new targets. Proteins of the fatty acid biosynthetic pathway are validated as drug targets in pathogenic bacteria and certain viruses. Likewise, this pathway has been speculated as a suitable target against parasite infections. Fatty acid synthesis in parasites seems to be very complex and distinct from the counterpart mammalian host due to the presence of unique mechanisms for fatty acid biosynthesis and acquisition. In recent times, there have been few evidences of the existence of this pathway in the bloodstream form of some pathogens. The fatty acid biosynthesis thus presents a viable and attractive target for emerging therapeutics. Understanding the mechanisms underlying fatty acid metabolism is key to identifying a potential drug target. However, investigations in this direction are still limited and this article attempts to outline the existing knowledge, while highlighting the scope and relevance of the fatty acid biosynthetic pathway as a drug target. This review highlights the advances in the treatment of leishmaniasis, the importance of lipids in the pathogen, known facts about the fatty acid biosynthesis in Leishmania and how this pathway can be manipulated to combat leishmaniasis, suggesting novel drug targets.

Some Scaffolds as Anti-leishmanial Agents: An Review

Leishmaniasis is a parasitic infectious neglected tropical disease transmitted to humans by the parasites of Leishmania species. Mainly three types of leishmaniasis cases such as visceral (VL), cutaneous (CL) and mucocutaneous leishmaniasis are usually observed. In many western countries, almost 700,000 to 1million peoples are suffering from leishmaniasis and it is estimated that around 26000 to 65000 deaths occurs annually. For its treatment few drugs are available however none of them are ideal to treat leishmaniasis due to long treatment, discomfort mode of administration, risk of high level toxicity, high resistance against etc. Hence so many patients are unable to take complete treatment due to the high drug resistance. The present review will focus on antileishmanial activity of reported derivatives of betacarboline, chalcone, azole, quinoline, quinazoline, benzimidazole, benzadiazapine, thiaazoles, semicarbazone and hydontoin analogues. We believe that this present study will helpful to researcher to design new antileishmanial agents.

Efficacy of green synthesized silver nanoparticles via ginger rhizome extract against Leishmania major in vitro

INTRODUCTION

Leishmaniasis is a major public health problem that causes by parasite of the genus Leishmania. The pentavalent antimonial compounds that used for treatment are not safe or effective enough. The aim of the present study was preparation and evaluation of the efficacy of green synthesized silver nanoparticles against Leishmania major (L. major) in vitro.

METHODS

To synthesis silver (Ag) nanoparticles (NPs), ginger extract was added to the 0.2mM AgNO3 aqueous solution (1:20). Effects of different concentrations of Ag-NPs on the number of L. major promastigotes were investigated using counting assay. The MTT test was applied to determine the toxicity of Ag-NPs on promastigotes of L. major, as well as, macrophage cells. Then, to evaluate the anti-amastigotes effects of Ag-NPs, parasites within the macrophages were counted by light microscope. Furthermore, to determine the induced apoptosis and necrotic effects of Ag-NPs on promastigotes, flow cytometry method was employed using annexin staining.

RESULTS

The effect of Ag-NPs on promastigotes and amastigotes of L. major was effective and has a reverse relationship with its concentration. According to the results of anti-amastigote assay, the IC50 value of this nanoparticle was estimated 2.35 ppm after 72h. Also, Ag-NPs caused Programmed Cell Death (PCD) in promastigotes of L. major and showed 60.18% of apoptosis.

DISCUSSION

Based on the mentioned results, it can be concluded that Ag NPs has a beneficial effect on promastigote and amastigote forms of L. major in vitro. Hence, these nanoparticles could be applied as promising antileishmanial agents for treatment of Leishmania infections.

Exploring Innovative Leishmaniasis Treatment: Drug Targets from Pre-Clinical to Clinical Findings

Leishmaniasis is a group of tropical diseases caused by parasitic protozoa belonging to the genus Leishmania. The disease is categorized in cutaneous leishmaniasis (CL), mucocutaneous leishmaniasis (MCL), and visceral leishmaniasis (VL). The conventional treatment is complex and can present high toxicity and therapeutic failures. Thus, there is a continuing need to develop new treatments. In this review, we focus on the novel molecules described in the literature with potential leishmanicidal activity, categorizing them in pre-clinical (in vitro, in vivo), drug repurposing and clinical research.

Preclinical Studies in Anti-Trypanosomatidae Drug Development

The trypanosomatid parasites Trypanosoma brucei, Trypanosoma cruzi and Leishmania are the causative agents of human African trypanosomiasis, Chagas Disease and Leishmaniasis, respectively. These infections primarily affect poor, rural communities in the developing world, and are responsible for trapping sufferers and their families in a disease/poverty cycle. The development of new chemotherapies is a priority given that existing drug treatments are problematic. In our search for novel anti-trypanosomatid agents, we assess the growth-inhibitory properties of >450 compounds from in-house and/or "Pathogen Box" (PBox) libraries against L. infantum, L. amazonensis, L.braziliensis, T. cruzi and T. brucei and evaluate the toxicities of the most promising agents towards murine macrophages. Screens using the in-house series identified 17 structures with activity against and selective toward Leishmania: Compounds displayed 50% inhibitory concentrations between 0.09 and 25 μM and had selectivity index values >10. For the PBox library, ~20% of chemicals exhibited anti-parasitic properties including five structures whose activity against L. infantum had not been reported before. These five compounds displayed no toxicity towards murine macrophages over the range tested with three being active in an in vivo murine model of the cutaneous disease, with 100% survival of infected animals. Additionally, the oral combination of three of them in the in vivo Chagas disease murine model demonstrated full control of the parasitemia. Interestingly, phenotyping revealed that the reference strain responds differently to the five PBox-derived chemicals relative to parasites isolated from a dog. Together, our data identified one drug candidate that displays activity against Leishmania and other Trypanosomatidae in vitro and in vivo, while exhibiting low toxicity to cultured mammalian cells and low in vivo acute toxicity.

Dipeptidyl peptidase III as a DNA marker to investigate epidemiology and taxonomy of Old World Leishmania species

BACKGROUND

Dipeptidyl peptidase III (DPPIII) member of M49 peptidase family is a zinc-dependent metallopeptidase that cleaves dipeptides sequentially from the N-terminus of its substrates. In Leishmania, DPPIII, was reported with other peptidases to play a significant role in parasites' growth and survival. In a previous study, we used a coding sequence annotated as DPPIII to develop and evaluate a PCR assay that is specific to dermotropic Old World (OW) Leishmania species. Thus, our objective was to further assess use of this gene for Leishmania species identification and for phylogeny, and thus for diagnostic and molecular epidemiology studies of Old World Leishmania species.

METHODOLOGY

Orthologous DDPIII genes were searched in all Leishmania genomes and aligned to design PCR primers and identify relevant restriction enzymes. A PCR assays was developed and seventy-two Leishmania fragment sequences were analyzed using MEGA X genetics software to infer evolution and phylogenetic relationships of studied species and strains. A PCR-RFLP scheme was also designed and tested on 58 OW Leishmania strains belonging to 8 Leishmania species and evaluated on 75 human clinical skin samples.

FINDINGS

Sequence analysis showed 478 variable sites (302 being parsimony informative). Test of natural selection (dN-dS) (-0.164, SE = 0.013) inferred a negative selection, characteristic of essential genes, corroborating the DPPIII importance for parasite survival. Inter- and intra-specific genetic diversity was used to develop universal amplification of a 662bp fragment. Sequence analyses and phylogenies confirmed occurrence of 6 clusters congruent to L. major, L. tropica, L. aethiopica, L. arabica, L. turanica, L. tarentolae species, and one to the L. infantum and L. donovani species complex. A PCR-RFLP algorithm for Leishmania species identification was designed using double digestions with HaeIII and KpnI and with SacI and PvuII endonucleases. Overall, this PCR-RFLP yielded distinct profiles for each of the species L. major, L. tropica, L. aethiopica, L. arabica and L. turanica and the L. (Sauroleishmania) L. tarentolae. The species L. donovani, and L. infantum shared the same profile except for strains of Indian origin. When tested on clinical samples, the DPPIII PCR showed sensitivities of 82.22% when compared to direct examination and was able to identify 84.78% of the positive samples.

CONCLUSION

The study demonstrates that DPPIII gene is suitable to detect and identify Leishmania species and to complement other molecular methods for leishmaniases diagnosis and epidemiology. Thus, it can contribute to evidence-based disease control and surveillance.

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.

17-AAG-Induced Activation of the Autophagic Pathway in Leishmania Is Associated with Parasite Death

The heat shock protein 90 (Hsp90) is thought to be an excellent drug target against parasitic diseases. The leishmanicidal effect of an Hsp90 inhibitor, 17-N-allylamino-17-demethoxygeldanamycin (17-AAG), was previously demonstrated in both in vitro and in vivo models of cutaneous leishmaniasis. Parasite death was shown to occur in association with severe ultrastructural alterations in Leishmania, suggestive of autophagic activation. We hypothesized that 17-AAG treatment results in the abnormal activation of the autophagic pathway, leading to parasite death. To elucidate this process, experiments were performed using transgenic parasites with GFP-ATG8-labelled autophagosomes. Mutant parasites treated with 17-AAG exhibited autophagosomes that did not entrap cargo, such as glycosomes, or fuse with lysosomes. ATG5-knockout (Δatg5) parasites, which are incapable of forming autophagosomes, demonstrated lower sensitivity to 17-AAG-induced cell death when compared to wild-type (WT) Leishmania, further supporting the role of autophagy in 17-AAG-induced cell death. In addition, Hsp90 inhibition resulted in greater accumulation of ubiquitylated proteins in both WT- and Δatg5-treated parasites compared to controls, in the absence of proteasome overload. In conjunction with previously described ultrastructural alterations, herein we present evidence that treatment with 17-AAG causes abnormal activation of the autophagic pathway, resulting in the formation of immature autophagosomes and, consequently, incidental parasite death.