Leishmania major MAPK4 intercepts and redirects CD40 signaling promoting infection.

The parasite Leishmania resides as amastigotes within the macrophage parasitophorous vacuoles inflicting the disease Leishmaniasis. Leishmania selectively modulates mitogen-activated protein kinase (MAPK) phosphorylation subverting CD40-triggered anti-leishmanial functions of macrophages. The mechanism of any pathogen-derived molecule induced host MAPK modulation remains poorly understood. Herein, we show that of the fifteen MAPKs, LmjMAPK4 expression is higher in virulent L. major. LmjMAPK4- detected in parasitophorous vacuoles and cytoplasm- binds MEK-1/2, but not MKK-3/6. Lentivirally-overexpressed LmjMAPK4 augments CD40-activated MEK-1/2-ERK-1/2-MKP-1, but inhibits MKK3/6-p38MAPK-MKP-3, phosphorylation. A rationally-identified LmjMAPK4 inhibitor reinstates CD40-activated host-protective anti-leishmanial functions in L. major-infected susceptible BALB/c mice. These results identify LmjMAPK4 as a MAPK modulator at the host-pathogen interface and establish a pathogen-intercepted host receptor signaling as a scientific rationale for identifying drug targets.

In silico study and in vitro antileishmanial and antitrypanosomal evaluation of azopyrazoles and azopyrimidines.

Hydrazones 1-6, azo-pyrazoles 7-9 and azo-pyrimidines 10-15 are compounds that exhibit antibacterial activity. The mode of action and structures of these derivatives have been previously confirmed as antibacterial. In this investigation, biological screening and molecular docking studies were performed for derivatives 1-15, with compounds 2, 7, 8, 14 and 15 yielding the best energy scores (from -20.7986 to -10.5302 kcal/mol). Drug-likeness and in silico ADME prediction for the most potent derivatives, 2, 7, 8, 14 and 15, were predicted (from 84.46 to 96.85%). The latter compounds showed good recorded physicochemical properties and pharmacokinetics. Compound 8 demonstrated the strongest inhibition, which was similar to the positive control (eflornithine) against Trypanosoma brucei brucei (WT), with an EC50 of 25.12 and 22.52µM, respectively. Moreover, compound 14 exhibited the best activity against Leishmania mexicana promastigotes and Leishmania major promastigotes (EC50 =46.85; 40.78µM, respectively).

Designing Antitrypanosomal and Antileishmanial BODIPY Derivatives: A Computational and In Vitro Assessment.

Leishmaniasis and Human African trypanosomiasis pose significant public health threats in resource-limited regions, accentuated by the drawbacks of the current antiprotozoal treatments and the lack of approved vaccines. Considering the demand for novel therapeutic drugs, a series of BODIPY derivatives with several functionalizations at the meso, 2 and/or 6 positions of the core were synthesized and characterized. The in vitro activity against Trypanosoma brucei and Leishmania major parasites was carried out alongside a human healthy cell line (MRC-5) to establish selectivity indices (SIs). Notably, the meso-substituted BODIPY, with 1-dimethylaminonaphthalene (1b) and anthracene moiety (1c), were the most active against L. major, displaying IC50 = 4.84 and 5.41 µM, with a 16 and 18-fold selectivity over MRC-5 cells, respectively. In contrast, the mono-formylated analogues 2b and 2c exhibited the highest toxicity (IC50 = 2.84 and 6.17 µM, respectively) and selectivity (SI = 24 and 11, respectively) against T. brucei. Further insights on the activity of these compounds were gathered from molecular docking studies. The results suggest that these BODIPYs act as competitive inhibitors targeting the NADPH/NADP+ linkage site of the pteridine reductase (PR) enzyme. Additionally, these findings unveil a range of quasi-degenerate binding complexes formed between the PRs and the investigated BODIPY derivatives. These results suggest a potential correlation between the anti-parasitic activity and the presence of multiple configurations that block the same site of the enzyme.

Leishmania Ribosomal Protein (RP) paralogous genes compensate each other's expression maintaining protein native levels.

In the protozoan parasite Leishmania, most genes encoding for ribosomal proteins (RPs) are present as two or more copies in the genome. However, their untranslated regions (UTRs) are predominantly divergent and might be associated with a distinct regulation of the expression of paralogous genes. Herein, we investigated the expression profiles of two RPs (S16 and L13a) encoded by duplicated genes in Leishmania major. The genes encoding for the S16 protein possess identical coding sequences (CDSs) and divergent UTRs, whereas the CDSs of L13a diverge by two amino acids and by their UTRs. Using CRISPR/Cas9 genome editing, we generated knockout (Δ) and endogenously tagged transfectants for each paralog of L13a and S16 genes. Combining tagged and Δ cell lines we found evidence of differential expression of both RPS16 and RPL13a isoforms throughout parasite development, with one isoform consistently more abundant than its respective copy. In addition, compensatory expression was observed for each paralog upon deletion of the corresponding isoform, suggesting functional conservation between these proteins. This differential expression pattern relates to post-translational processes, given compensation occurs at the level of the protein, with no alterations detected at transcript level. Ribosomal profiles for RPL13a indicate a standard behavior for these paralogues suggestive of interaction with heavy RNA-protein complexes, as already reported for other RPs in trypanosomatids. We identified paralog-specific bound to their 3'UTRs which may be influential in regulating paralog expression. In support, we identified conserved cis-elements within the 3'UTRs of RPS16 and RPL13a; cis-elements exclusive to the UTR of the more abundant paralog or to the less abundant ones were identified.

Investigating the effect of parasites (toxoplasma gondii RH strain, Leishmania major (MRHO/IR/75/ER), and hydatid cyst) antigens on Alzheimer's disease: An in vivo evaluation.

This study aimed to investigate the effects of parasite antigens on Alzheimer's symptoms in animal model. Alzheimer's model was induced in Wistar rats using Amyloid-beta peptide, and treated with parasite crude antigens from T. gondii RH strain, L. major (MRHO/IR/75/ER), and HC. Spectrophotometry and real-time PCR were used to evaluate the oxidative stress levels, antioxidant enzyme activity, and gene expression of NLRP3, IL-8, IL-1ß, and Caspase-1. Histological assays were performed to investigate structural changes in the hippocampus. Apoptosis was analyzed using an Annexin V Apoptosis by Flow cytometer. The levels of total oxidant, antioxidant, and SOD increased in the Alzheimer's group compared with the control group, but these factors were lower in the L. major group. The apoptosis in the treated groups was lower compared to the Alzheimer's group. IL-8 expression was significantly higher in all Alzheimer's groups, but decreased in the HC and L. major treated group compared to Alzheimer's. IL-1ß and Caspase-1 expression were similarly increased in all groups compared with the control group, but decreased in the antigen-treated groups compared with Alzheimer's. NLRP3 expression was increased in all groups compared with the control group, with lower expression in HC group, but significantly decreased in L. major group compared with Alzheimer's. In histological results, only L. major group could play a therapeutic role in pathological damage of the hippocampus. The results showed that parasite antigens, specifically L. major antigens, may have neuroprotective effects that reduce oxidative stress, apoptosis, and histopathological changes in response to AD in animal model.

Circadian Regulation of Leishmania Parasite Internalisation in Macrophages and Downstream Cellular Events.

Leishmania spp. parasites use macrophages as a host cell during infection. As a result, macrophages have a dual role: clearing the parasite as well as acting as host cells. Recently, studies have shown that macrophages harbour circadian clocks, which affect many of their functions such as phagocytosis, receptor expression and cytokine release. Interestingly, Leishmania major infection in hosts was also shown to be under circadian control. Therefore, we decided to investigate what underlies the rhythms of L. major infection within macrophages. Using a culture model of infection of bone marrow-derived macrophages with L. major promastigotes, we show that the parasites are internalised into macrophages with a 24-h variation dependent on a functional circadian clock in the cells. This was associated with a variation in the number of parasites per macrophage. The cell surface expression of parasite receptors was not controlled by the cells' circadian clock. In contrast, the expression of the components of the endocytic pathway, EEA1 and LC3b, varied according to the time of infection. This was paralleled by variations in parasite-induced ROS production as well as cytokine tumour necrosis factor α. In summary, we have uncovered a time-dependent regulation of the internalisation of L. major promastigotes in macrophages, controlled by the circadian clock in these cells, as well as subsequent cellular events in the endocytic pathway, intracellular signalling and cytokine production.

Preparation and characterization of artemether-loaded niosomes in Leishmania major-induced cutaneous leishmaniasis.

Cutaneous leishmaniasis is the most prevalent form of leishmaniasis worldwide. Although various anti-leishmanial regimens have been considered, due to the lack of efficacy or occurrence of adverse reactions, design and development of novel topical delivery systems would be essential. This study aimed to prepare artemether (ART)-loaded niosomes and evaluate their anti-leishmanial effects against Leishmania major. ART-loaded niosomes were prepared through the thin-film hydration technique and characterized in terms of particle size, zeta potential, morphology, differential scanning calorimetry, drug loading, and drug release. Furthermore, anti-leishmanial effect of the preparation was assessed in vitro and in vivo. The prepared ART-loaded niosomes were spherical with an average diameter of about 100 and 300 nm with high encapsulation efficiencies of > 99%. The results of in vitro cytotoxicity revealed that ART-loaded niosomes had significantly higher anti-leishmanial activity, lower general toxicity, and higher selectivity index (SI). Half-maximal inhibitory concentration (IC50) values of ART, ART-loaded niosomes, and liposomal amphotericin B were 39.09, 15.12, and 20 µg/mL, respectively. Also, according to the in vivo study results, ART-loaded niosomes with an average size of 300 nm showed the highest anti-leishmanial effects in animal studies. ART-loaded niosomes would be promising topical drug delivery system for the management of cutaneous leishmaniasis.

Transcriptional signatures in human macrophage-like cells infected by Leishmania infantum, Leishmania major and Leishmania tropica.

BACKGROUND: In the Mediterranean basin, three Leishmania species have been identified: L. infantum, L. major and L. tropica, causing zoonotic visceral leishmaniasis (VL), zoonotic cutaneous leishmaniasis (CL) and anthroponotic CL, respectively. Despite animal models and genomic/transcriptomic studies provided important insights, the pathogenic determinants modulating the development of VL and CL are still poorly understood. This work aimed to identify host transcriptional signatures shared by cells infected with L. infantum, L. major, and L. tropica, as well as specific transcriptional signatures elicited by parasites causing VL (i.e., L. infantum) and parasites involved in CL (i.e., L. major, L. tropica). METHODOLOGY/PRINCIPAL FINDINGS: U937 cells differentiated into macrophage-like cells were infected with L. infantum, L. major and L. tropica for 24h and 48h, and total RNA was extracted. RNA sequencing, performed on an Illumina NovaSeq 6000 platform, was used to evaluate the transcriptional signatures of infected cells with respect to non-infected cells at both time points. The EdgeR package was used to identify differentially expressed genes (fold change > 2 and FDR-adjusted p-values < 0.05). Then, functional enrichment analysis was employed to identify the enriched ontology terms in which these genes are involved. At 24h post-infection, a common signature of 463 dysregulated genes shared among all infection conditions was recognized, while at 48h post-infection the common signature was reduced to 120 genes. Aside from a common transcriptional response, we evidenced different upregulated functional pathways characterizing L. infantum-infected cells, such as VEGFA-VEGFR2 and NFE2L2-related pathways, indicating vascular remodeling and reduction of oxidative stress as potentially important factors for visceralization. CONCLUSIONS: The identification of pathways elicited by parasites causing VL or CL could lead to new therapeutic strategies for leishmaniasis, combining the canonical anti-leishmania compounds with host-directed therapy.

Neutrophil extracellular traps formation: effect of Leishmania major promastigotes and salivary gland homogenates of Phlebotomus papatasi in human neutrophil culture.

BACKGROUND: Leishmaniasis as a neglected tropical disease (NTD) is caused by the inoculation of Leishmania parasites via the bite of phlebotomine sand flies. After an infected bite, a series of innate and adaptive immune responses occurs, among which neutrophils can be mentioned as the initiators. Among the multiple functions of these fighting cells, neutrophil extracellular traps (NETs) were studied in the presence of Leishmania major promastigotes and salivary gland homogenates (SGH) of Phlebotomus papatasi alone, and in combination to mimic natural conditions of transmission. MATERIAL & METHODS: The effect of L. major and SGH on NETs formation was studied in three different groups: neutrophils + SGH (NS), neutrophils + L. major (NL), neutrophils + L. major + SGH (NLS) along with negative and positive controls in 2, 4 and 6 h post-incubation. Different microscopic methods were used to visualize NETs comprising: fluorescence microscopy by Acridine Orange/ Ethidium Bromide staining, optical microscopy by Giemsa staining and scanning electron microscopy. In addition, the expression level of three different genes NE, MPO and MMP9 was evaluated by Real-Time PCR. RESULTS: All three microscopical methods revealed similar results, as in NS group, chromatin extrusion as a sign of NETosis, was not very evident in each three time points; but, in NL and especially NLS group, more NETosis was observed and the interaction between neutrophils and promastigotes in NL and also with saliva in NLS group, gradually increased over times. Real-time reveals that, the expression of MPO, NE and MMP9 genes increased during 2 and 4 h after exposure, and then decreased at 6 h in most groups. CONCLUSION: Hence, it was determined that the simultaneous presence of parasite and saliva in NLS group has a greater impact on the formation of NETs compared to NL and NS groups.

Role of Macrophage PIST Protein in Regulating Leishmania major Infection.

PDZ protein interacting specifically with Tc10 or PIST is a mammalian trans-Golgi resident protein that regulates subcellular sorting of plasma membrane receptors. PIST has recently emerged as a key player in regulating viral pathogenesis. Nevertheless, the involvement of PIST in parasitic infections remains unexplored. Leishmania parasites infiltrate their host macrophage cells through phagocytosis, where they subsequently multiply within the parasitophorous vacuole (PV). Host cell autophagy has been found to be important in regulating this parasite infection. Since PIST plays a pivotal role in triggering autophagy through the Beclin 1-PI3KC3 pathway, it becomes interesting to identify the status of PIST during Leishmania infection. We found that while macrophage cells are infected with Leishmania major (L. major), the expression of PIST protein remains unaltered; however, it traffics from the Golgi compartment to PV. Further, we identified that in L. major-infected macrophage cells, PIST associates with the autophagy regulatory protein Beclin 1 within the PVs; however, PIST does not interact with LC3. Reduction in PIST protein through siRNA silencing significantly increased parasite burden, whereas overexpression of PIST in macrophages restricted L. major infectivity. Together, our study reports that the macrophage PIST protein is essential in regulating L. major infectivity.

The apo-acyl coenzyme A binding protein of Leishmania major forms a unique 'AXXA' motif mediated dimer.

Acyl-Coenzyme A binding domain containing proteins (ACBDs) are ubiquitous in nearly all eukaryotes. They can exist as a free protein, or a domain of a large, multidomain, multifunctional protein. Besides modularity, ACBDs also display multiplicity. The same organism may have multiple ACBDs, differing in sequence and organization. By virtue of this diversity, ACBDs perform functions ranging from transport, synthesis, trafficking, signal transduction, transcription, and gene regulation. In plants and some microorganisms, these ACBDs are designated ACBPs (acyl-CoA binding proteins). The simplest ACBD/ACBP is a small, ∼10 kDa, soluble protein, comprising the acyl-CoA binding (ACB) domain. Most of these small ACBDs exist as monomers, while a few show a tendency to oligomerize. In sync with those studies, we report the crystal structure of two ACBDs from Leishmania major, named ACBP103, and ACBP96 based on the number of residues present. Interestingly, ACBP103 crystallized as a monomer and a dimer under different crystallization conditions. Careful examination of the dimer disclosed an exposed 'AXXA' motif in the helix I of the two ACBP103 monomers, aligned in a head-to-tail arrangement in the dimer. Glutaraldehyde cross-linking studies confirm that apo-ACBP103 can self-associate in solution. Isothermal titration calorimetry studies further show that ACBP103 can bind ligands ranging from C8 - to C20-CoA, and the data could be best fit to a 'two sets of sites'/sequential binding site model. Taken together, our studies show that Leishmania major ACBP103 can self-associate in the apo-form through a unique dimerization motif, an interaction that may play an important role in its function.

Comparison of Intralesional Sodium Stibogluconate versus Intralesional Meglumine Antimoniate for the Treatment of Leishmania major Cutaneous Leishmaniasis.

Israel is endemic for Old-World cutaneous leishmaniasis. The most common species is Leishmania major. However, the available treatment options are limited. This study's objective was to compare the authors' experience with different antimony intralesional treatments of Leishmania major cutaneous leishmaniasis. A retrospective evaluation was undertaken for cases of Leishmania major cutaneous leishmaniasis treated by pentavalent antimony in a university-affiliated medical centre in Israel. The previous treatment of intralesional sodium stibogluconate (Pentostam®) was compared with the current treatment of meglumine antimoniate (Glucantime®). One hundred cases of cutaneous leishmaniasis were treated during the study period, of whom 33 were treated with intralesional sodium stibogluconate and 67 were treated with intralesional meglumine antimoniate. The patients were 78 males and 22 females, mean age 24 (range 10-67) and there was a total of 354 skin lesions. Within 3 months from treatment, 91% (30/33) of the intralesional sodium stibogluconate group and 88% (59/67) of the intralesional meglumine antimoniate group had complete healing of the cutaneous lesions after an average of 3 treatment cycles (non-statistically significant). In conclusion, the 2 different medications have the same efficacy and safety for treating cutaneous leishmaniasis. Pentavalent antimoniate intralesional infiltration treatment is safe, effective, and well tolerated with minimal side effects for Old-World cutaneous leishmaniasis.

In silico prediction of CD8+ and CD4+ T cell epitopes in Leishmania major proteome: Using immunoinformatics.

The leishmaniases are NDTs (neglected tropical diseases) that affect people all over the world. They are brought on by protozoans from the genus Leishmania and disseminated by phlebotomine flies that are afflicted with the disease. The best option to manage and lower the incidence of these diseases has been thought by the creation of a safe and effective vaccination. This research used an in silico based mining approach to look for high potential epitopes that might bind to MHC Class I and MHC Class II molecules (mainly; HLA-A*02:01 & HLA-DRB1*03:01) from human population in order to promote vaccine development. Based on the presence of signal peptides, GPI anchors, antigenicity predictions, and a subtractive proteomic technique, we have screened 17 putative antigenic proteins from the 8083 total proteins of L. major. After that thorough immunogenic epitope prediction were done using IEDB-AR tools. We isolated five immunogenic epitopes (three 9-mer & two 15-mer) from five antigenic proteins through docking and MD simulation analysis. Finally, these five anticipated epitopes, viz., TLPEIPVNV, ELMAPVFGL, TLAAAVALL, NSINIRLDGVTSAGF and NVPLVVDASSLFRVA have considerably stronger binding potential with their respective alleles and may trigger immunological responses. The goal of this work was to identify MHC restricted epitopes for CD8+ and CD4+ T cells activation using immunoinformatics in order to identify potential vaccine candidates against L. major parasites.

Genetic Diversity of Leishmania major Isolated from Different Dermal Lesions Using ITS2 Region.

BACKGROUND AND OBJECTIVE: Cutaneous leishmaniasis (CL) is still considered to be an uncontrolled endemic disease that spreads in many countries. The current study aimed to determine intra-species relationships of L. major using ITS2 sequencing. METHODS: The study was conducted from the beginning of March to the end of November 2022. All medical information regarding CL was collected from patients of Thi-Qar province who attended the Dermatology Department of Al-Hussein Teaching Hospital in Nasiriyah city. Seventy-three samples were selected for the molecular identification after confirming microscopy with Giemsa stain. In this study, the primers were designed using NCBI GenBank sequence database and Primer 3 plus primer design online software. RESULTS: The results recorded 21 (28.77%) positive samples of L. major using the internal transcribed spacer 2 region (ITS2) in ribosomal RNA gene. The local L. major IQN.1-IQN.10 were submitted to NCBI GenBank database with accession numbers OM069357.1-OM069366.1, respectively. The phylogenetic analysis revealed that local isolates of L. major showed a close relationship with NCBI-BLAST L. major Iran isolate (KU680848.1). CONCLUSION: ITS2-PCR is suitable for identifying Leishmania spp. and determining genetic diversity. A phylogenetic data analysis may provide an idea on the genetic homogeneity of local isolates and knowing the genetic origin of the dermal lesion. However, the local isolates showed genetic proximity to the KU680848.1 isolate. This signifies the possibility of infection prevalence from Iranian areas. In general, genetic variation of L. major isolates may give several clinical manifestations of the cutaneous lesion. Therefore, determination of the heterogeneity is important for detecting the infection origin, epidemiology, therapy, and control strategies.

Elucidating miR-146a-3p as a key player in autophagy and lipid metabolism in Leishmania major infection.

Autophagy is a key step involved in many unicellular eukaryotic diseases, including leishmaniasis, for cellular remodelling and differentiation during parasite's lifecycle. Lipids play a significant role in the infection process that begins with Leishmania major invading host cells. MicroRNAs (miRNAs), a family of small, 22-24 nucleotide noncoding regulatory RNAs, target mRNAs to modify gene expression and, subsequently, proteome output may have a regulatory role in altering the host cell processes. We observed miR-146a-3p expression increases in a time-dependent manner post Leishmania major infection. Transfecting miR-146a-3p mimic increases the expression of ATG7, an autophagy gene that encodes an E1-like enzyme in two ubiquitin-like conjugation systems required for autophagosome progression. HPGD (15-hydroxyprostaglandin dehydrogenase) operates as an enzyme, converting prostaglandin to its non-active form. Microarray data and western studies reveal that miR-146a-3p targets and inhibits HPGD, thereby increasing prostaglandin activity in lipid droplets. Herein, our research focuses on miR-146a-3p, which boosts ATG7 expression while reducing HPGD post Leishmania major infections helping us comprehend the intricate network of microRNA, autophagy, and lipid metabolism in leishmaniasis.

Phylogenetic analysis and antimony resistance of Leishmania major isolated from humans and rodents.

Cutaneous Leishmaniasis (CL) is one of the world's neglected diseases which is caused by Leishmania spp. The aim of this study was to assess molecular profile and antimony resistance of Leishmania isolated from human and rodent hosts. Samples were collected from suspected CL patients referred to health centres and wild rodent's traps in Gonbad-e-Qabus region, north-eastern Iran. Smears were subjected to PCR-RFLP to identify Leishmania species. In addition, ITS1-PCR products were sequenced for phylogenetic analysis. Clinical isolates and rodent samples were subjected to MTT assay to determine IC50 values and in vitro susceptibilities. Expression levels of antimony resistance-related genes were determined in CL isolates. Out of 1,949 suspected patients with CL and 148 rodents, 1,704 (87.4%) and 6 (4.05%) were positive with direct smear, respectively. Digestion patterns of BusRI (HaeIII) endonuclease enzyme were similar to what expected for Leishmania major. Phylogenetic analysis revealed that the highest interspecies similarity was found between current L. major sequences with L. major obtained from Russia and Uzbekistan. Out of 20 L. major samples tested, 13 (65%) were resistant to meglumine antimoniate (MA) treatment, with an activity index (AI) exceeding 4. The remaining 7 samples (35%) responded to MA treatment and were classified as sensitive isolates, with a confirmed sensitive phenotype based on their AI values. The comparison expression analysis of three major antimony resistance-associated genes in unresponsive clinical isolates demonstrated significant fold changes for TDR1 (4.78-fold), AQP1 (1.3-fold), and γ-GCS (1.17-fold) genes (P < 0.05). Herein, we demonstrate genetic diversity and antimony resistance of L. major isolated from human and reservoir hosts in north-eastern Iran, which could be the basis for planning future control strategies.

A Geomedical Survey: Is There an Association Between Climatic Conditions and Leishmania Species Distribution in Iran During the Years 1999-2021?

PURPOSE: Iran is among the high-risk leishmaniasis regions in the world. WHO recommends the use of GIS as an ideal tool for healthcare authorities to predict the evolution of a disease, delimit the risk of outbreaks and identify critical areas. The aim of this research is to find the association between the main species of Leishmania (L. major, L. tropica, L. infantum) dispersion and climatic variables in Iran. METHODS: All molecular-based reports of leishmaniasis from Iran between 1999 and 2021 were gathered from reliable medical sources. Meteorological data (air and soil temperatures, annual rainfall and humidity) of the country along the study period were obtained from the Iranian Climatological Research Centre. The data concerning species distribution and climatic conditions during this period were moved to a base-map through raster layers using ArcGIS 10.4.1 software. The relationship between parasitological and climatic models was examined using ANOVA. RESULTS: High risk area maps, based on the cut-off thresholds, were generated for Leishmania major, L. tropica and L. infantum. According to the molecular-based reports, the L. major distribution was significantly related to all climatic variables, while L. tropica was merely related to rainfall and humidity, and the L. infantum distribution was significantly associated with rainfall, soil and air temperatures. CONCLUSION: The association between climatic conditions and Leishmania species distribution in Iran has been confirmed. Consequently, both, the relationship between climatic conditions and the geographical distribution of Leishmania species, and the use of GIS to better understand the spatial epidemiology of leishmaniasis, have been reaffirmed.

Leishmania profilin interacts with actin through an unusual structural mechanism to control cytoskeletal dynamics in parasites.

Diseases caused by Leishmania and Trypanosoma parasites are a major health problem in tropical countries. Because of their complex life cycle involving both vertebrate and insect hosts, and >1 billion years of evolutionarily distance, the cell biology of trypanosomatid parasites exhibits pronounced differences to animal cells. For example, the actin cytoskeleton of trypanosomatids is divergent when compared with other eukaryotes. To understand how actin dynamics are regulated in trypanosomatid parasites, we focused on a central actin-binding protein profilin. Co-crystal structure of Leishmania major actin in complex with L. major profilin revealed that, although the overall folds of actin and profilin are conserved in eukaryotes, Leishmania profilin contains a unique α-helical insertion, which interacts with the target binding cleft of actin monomer. This insertion is conserved across the Trypanosomatidae family and is similar to the structure of WASP homology-2 (WH2) domain, a small actin-binding motif found in many other cytoskeletal regulators. The WH2-like motif contributes to actin monomer binding and enhances the actin nucleotide exchange activity of Leishmania profilin. Moreover, Leishmania profilin inhibited formin-catalyzed actin filament assembly in a mechanism that is dependent on the presence of the WH2-like motif. By generating profilin knockout and knockin Leishmania mexicana strains, we show that profilin is important for efficient endocytic sorting in parasites, and that the ability to bind actin monomers and proline-rich proteins, and the presence of a functional WH2-like motif, are important for the in vivo function of Leishmania profilin. Collectively, this study uncovers molecular principles by which profilin regulates actin dynamics in trypanosomatids.

Adipose-Derived Stem Cells' Secretome Attenuates Lesion Size and Parasite Loading in Leishmaniasis Caused by Leishmania Major in Mice.

Background: Stem cell-derived secretome (SE) released into the extracellular space contributes to tissue repair. The present study aimed to investigate the impact of isolated secretome (SE) from adipose-derived mesenchymal stem cells (ASCs) on Leishmania major (L. major) lesions in BALB/c mice. Methods: This experimental study was conducted at Ahvaz University of Medical Sciences (Ahvaz, Iran) in 2021. Forty female BALB/c mice were infected with stationary phase promastigotes through intradermal injection in the bottom of their tail and randomly divided into four groups (n=10 per group). The mice were given SE (20 mg/mL), either alone or in combination with Glucantime (GC, 20 mg/mL/Kg), meglumine antimoniate (20 mg/mL/Kg) for the GC group, and phosphate-buffered saline (PBS) for the control group. After eight weeks, the lesion size, histopathology, the levels of Interleukin 10 (IL-10), and Interleukin 12 (IL-12) were assessed. For the comparison of values between groups, the parametric one-way ANOVA was used to assess statistical significance. Results: At the end of the experiment, the mice that received SE had smaller lesions (4.56±0.83 mm versus 3.62±0.59 mm, P=0.092), lower levels of IL-10 (66.5±9.7 pg/mL versus 285.4±25.2 pg/mL, P<0.001), and higher levels of IL-12 (152.2±14.2 pg/mL versus 24.2±4.4 pg/mL, P<0.001) than the control. Histopathology findings revealed that mice treated with SE had a lower parasite burden in lesions and spleen than the control group. Conclusion: The current study demonstrated that ADSC-derived SE could protect mice infected with L. major against leishmaniasis.

Photodynamic therapy of cationic and anionic BSA-curcumin nanoparticles on amastigotes of Leishmania braziliensis and Leishmania major and Leishmania amazonensis.

Cutaneous leishmaniasis is a neglected disease prevalent in tropical countries, and conventional treatment can cause several serious side effects. Photodynamic therapy (PDT) can be considered a promising treatment alternative, as it is non-invasive therapy that has no side effects and uses accessible and low-cost substances, such as curcumin. This study evaluated the PDT response with cationic and anionic BSA nanoparticles encapsulated with curcumin in macrophages infected with L. braziliensis, L. major, and L. amazonensis. The nanoparticle system was characterized using a steady-state technique, scanning electron microscopy (SEM) study, and its biological activity was evaluated using macrophage cell lines infected with different Leishmania species. All spectroscopy measurements demonstrated that BSA curcumin (BSACur) has good photophysical properties, and confocal microscopy shows that macrophages and protozoa internalized the nanoparticles. The viability test demonstrated that at low concentrations, such as 0.1, 0.7, and 1.0 µmol. L-1, there was a decrease in cell viability after PDT application. Furthermore, a decrease in the number of parasites recovered was observed in the PDT groups. The results allowed us to conclude that curcumin loaded into BSA nanoparticles may have potential application in drug delivery systems for PDT protocols, demonstrating reduced cell viability at lower concentrations than free curcumin.