Reactive oxygen species and nitric oxide in cutaneous leishmaniasis

PLGA nanoparticle-delivered Leishmania antigen and TLR agonists as a therapeutic vaccine against cutaneous leishmaniasis in BALB/c mice

Leishmaniasis, caused by Leishmania (L.) species, remains a neglected infection. Therapeutic vaccination presents a promising strategy for its treatment. In this study, we aimed to develop a therapeutic vaccine candidate using Leishmaniaantigens (SLA) and Toll-like receptor (TLR) 7/8 agonist (R848) encapsulated into the poly (lactic-co-glycolic acid) (PLGA) nanoparticles (NPs). Moreover, TLR1/2 agonist (Pam3CSK4) was loaded onto the NPs. The therapeutic effects of these NPs were evaluated in L. major-infected BALB/c mice. Footpad swelling, parasite load, cellular and humoral immune responses, and nitric oxide (NO) production were analyzed. The results demonstrated that the PLGA NPs (SLA-R848-Pam3CSK4) therapeutic vaccine effectively stimulated Th1 cell responses, induced humoral responses, promoted NO production, and restricted parasite burden and lesion size.Our findings suggest that vaccination with SLA combined with TLR1/2 and TLR7/8 agonists in PLGA NPs as a therapeutic vaccine confers strong protection againstL. majorinfection. These results represent a novel particulate therapeutic vaccine against Old World cutaneous leishmaniasis.

Unveiling of the antileishmanial activities of Linalool loaded zinc oxide nanocomposite through its potent antioxidant and immunomodulatory effects

This study aimed to produce linalool loaded zinc oxide nanocomposite (LZNPs) and assess its in vitro and in vivo antileishmanial effects against Leishmania major. LZNPs was produced through the synthesis of an ethanolic solution containing polyvinyl alcohol. The average size of LZNPs was determined to be 105 nm. The findings indicated that LZNPs displayed significant (p < 0.01) antileishmanial effects on promastigotes and amastigotes. Following exposure of promastigotes to LZNPs, there was a notable rise in the percentage of early and late apoptotic cells from 9.0 to 57.2 %. The gene expression levels of iNOS, IFN-γ, and TNF-α in macrophages were upregulated in a dose-dependent approach following exposure to LZNPs. LZNPs alone and in conjunction with glucantime (Glu) resulted in a reduction in the diameter and parasite load of CL lesions in infected mice. Treatment of the CL-infected mice with LZNPs at 25 and 50 mg/kg mainly in combination with Glu-reduced the tissue level of malondialdehyde (MDA), increased both gene and protein expression of the antioxidant enzymes as well as raised the expression level of IFN-γ and IL-12 cytokines, whereas caused a significant reduction in the expression level of IL-4. The present study shows that LZNPs has potent antileishmanial effects and controls CL in a mice model through its antioxidant and immunomodulatory properties. Further investigation, especially in clinical trials, could explore the potential use of this nanocomposite in managing and treating CL.

Global Remodeling of Host Proteome in Response to Leishmania Infection

The protozoan parasite Leishmania possesses an intrinsic ability to modulate a multitude of pathways in the host, toward aiding its own proliferation. In response, the host reprograms its cellular, immunological, and metabolic machinery to evade the parasite's lethal impact. Besides inducing various antioxidant signaling pathways to counter the elevated stress response proteins like heme oxygenase-1 (HO-1), Leishmania also attempts to delay host cell apoptosis by promoting anti-apoptotic proteins like Bcl-2. The downstream modulation of apoptotic proteins is regulated by effector pathways, including the PI3K/Akt survival pathway, the mitogen-activated protein kinases (MAPKs) signaling pathway, and STAT phosphorylation. In addition, Leishmania assists in its infection in a time-dependent manner by modulating the level of various proteins of autophagic machinery. Immune effector cells, such as mast cells and neutrophils, entrap and kill the pathogen by secreting various granular proteins. In contrast, the host macrophages exert their leishmanicidal effect by secreting various cytokines, such as IL-2, IL-12, etc. An interplay of various signaling pathways occurs in an organized network that is highly specific to both pathogen and host species. This Review analyzes the modulation of expression of proteins, including the cytokines, providing a realistic approach toward understanding the pathophysiology of disease and predicting some prominent markers for disease intervention and vaccine support strategies.

Evaluation of IL-8, nitric oxide and macrophage inhibitory factor as clinical circulatory markers in patients with cutaneous leishmaniasis, before and during sodium stibogluconate treatment

The clinical spectrum of cutaneous leishmaniasis (CL), an intracellular parasitic pathogen, ranges from a single sore healing to chronic crusty lesions with a manifestation of treatment resistance. The complicated interaction between Leishmania bodies and the early immune response, including innate and adaptive mechanisms, determines the evolution of nodules. This study examined the levels of the chemoattractant interleukin 8 (IL-8), pro-inflammatory nitric oxide (NO), and immunoregulatory macrophage inhibitory factor (MIF) in the serum of subjects recently diagnosed with cutaneous leishmaniasis, in parallel with patients being monitored during consecutive sodium stibogluconate (Pentostam) treatment. A total of 161 serum samples of newly diagnosed individuals and patients undergoing pentostam injections were collected form an endemic area of Diyala, east central of Iraq. Sandwich ELISA was used to measure the level of IL-8, NO and MIF in the studied groups. Results of circulatory markers levels showed a considerable difference in all groups, with IL-8 being exceptionally higher in the first two groups of pretreated and dose-1 (191.5, 273.64) pg/ml respectively, while NO was found to be lower than in control subjects, particularly in the pretreated group (12.08 µmol/L) and MIF level was significantly higher in the pretreated group, which was (7.18 pg/ml). These findings can provide insights for distinction of disease phase and monitoring treatment efficacy along consecutive dosages, particularly in populations where CL is endemic.

Photodynamic therapy mediated by a red LED and methylene blue inactivates resistant Leishmania amazonensis

Cutaneous leishmaniasis is a neglected parasitic disease that leads to destructive lesions. The emergence of drug resistance has been a global concern over the past years. Photodynamic therapy (PDT) mediated by a red LED and methylene blue (MB) involves the overproduction of oxidative stress, which oxidizes several cellular biomolecules and prevents the selection of resistant strains. Herein, we investigated the potential of PDT mediated by MB against wild-type and miltefosine-resistant strains of Leishmania amazonensis. As a result, both strains were susceptible to PDT, thus encouraging us to seek the best conditions to overcome the drug resistance problem in cutaneous leishmaniasis.

Leishmaniasis: Recent epidemiological studies in the Middle East

Leishmaniasis, one of the most neglected tropical diseases (NTDs), is the third most important vector-borne disease worldwide. This disease has a global impact and severity of the infection and is greatest in the Middle East. The agent of infection is a protozoan parasite of the genus, Leishmania, and is generally transmitted by blood-sucking female sandflies. In humans, there are three clinical forms of infection: (1) cutaneous (CL), (2) mucocutaneous (ML), and (3) visceral leishmaniasis (VL). This review aims to discuss the current epidemiological status of leishmaniasis in Saudi Arabia, Iraq, Syria, and Yemen with a consideration of treatment options. The elevated risk of leishmaniasis is influenced by the transmission of the disease across endemic countries into neighboring non-infected regions.

Autophagy induced macrophages by α-alumina(α-AL2O3) conjugated cysteine peptidase, enhances the cytotoxic activity of CD8+ T lymphocytes against Leishmania major

Introduction

Induction of a protective immune response against Leishmania major requires the activation of both TH1 and CD8+ T lymphocytes. Because L. major is an intra-phagosomal parasite, its antigens do not have access to MHC-I. The present study aimed to evaluate the effect of cysteine peptidase A (CPA)/cysteine peptidase B (CPB) conjugated to α-AL2O3 on autophagy induction in L. major infected macrophages and subsequent activation of cytotoxic CD8+ T lymphocytes.

Methods

Recombinant CPA and CPB of L. major were produced in expression vectors and purified. Aldehyde functionalized α-AL2O3 were conjugated to hydrazine-modified CPA/CPB by a chemical bond was confirmed by Fourier-transform infrared spectroscopy (FTIR). The High efficient internalization of α-AL2O3 conjugated CPA/CPB to macrophages was confirmed using a fluorescence microscope and flowcytometry. Induction of the acidic autophagosome and LC3 conversion in macrophages was determined by acridine orange (AO) staining and western blot. Autophagy-activated macrophages were used for CD8+ T cell priming. Cytotoxic activity of the primed CD8+ T cell against L. major infected macrophages was measured using apoptosis assay.

Results

α-AL2O3 conjugated CPA/CPB enhances macrophages antigen uptake and increases acidic vacuole formation and LC-3I to LC-3II conversion. Co-culture of autophagy-activated macrophages with CD8+ T cells augmented CD8+ T cells priming and proliferation more than in other study groups. These primed CD8+ T cells induce significant apoptotic death of L. major infected macrophages compared with non-primed CD8+ T cells.

Conclusion

α-AL2O3 nanoparticles enhance the cross-presentation of L. major antigens to CD8+ T cells by inducing autophagy. This finding supports the positive role of autophagy and encourages the use of α-AL2O3 in vaccine design.

Anti-leishmaniasis Effect of Staphylococcus Aureus Protein A on the Size of the Lesion and Parasitic Load

Background

Many studies in the past have evaluated the role of immune system boosters in the treatment of leishmania major infection. Protein A (PA) is one of the structural components in peptidoglycan cell wall of gram-negative bacteria such as staphylococcus aurous which functions as a stimulator in the cellular immune system. The present study aims to evaluate the anti-inflammatory effect of PA on the recovery of leishmania major infection.

Materials and Methods

This study was conducted on 24 female Balb/c-infected mice. The experimental group received PA at a dose of 60 mg/kg for four weeks. There was no intervention for the negative control group; the third group received the solvent of PA and sterile H2O; and the positive control group received Amphotericin B at a dose of 1 mg/kg body weight. At the end of the treatment period, a real-time polymerase chain reaction (PCR) assay was performed to determine parasitic burden, and the size of the lesions was measured by caliper with an accuracy of 0.01 mm.

Results

Results showed that PA did slightly decrease the wound spread and growth but not to an extent that can be considered statistically significant. Also, differences in cycle threshold (Ct) values between the treated group and the untreated group was not impressive.

Conclusions

Although findings showed that PA isn't such a good candidate for leishmania treatment, it may still be suitable for therapies that use multiple drugs in combination to speed up the healing of leishmaniosis, an issue that merits evaluation in future studies.

Exploring the antileishmanial activity of N1,N2-disubstituted-benzoylguanidines: synthesis and molecular modeling studies

In this report, we describe the synthesis and evaluation of nine N¹,N²-disubstituted-benzoylguanidines against promastigotes and amastigotes forms of Leishmania amazonensis. The derivatives 2g and 2i showed low IC₅₀ values against promastigote form (90.8 ± 0.05 µM and 68.4 ± 0.03 µM, respectively), low cytotoxicity profile (CC₅₀ 396 ± 0.02 µM and 857.9 ± 0.06 µM) for peritoneal macrophages cells and SI of 5.5 and 12.5, respectively. Investigations about the mechanism of action of 2g and 2i showed that both compounds cause mitochondrial depolarization, increase in ROS levels, and generation of autophagic vacuoles on free promastigotes forms. These compounds were also capable of reducing the number of infected macrophages with amastigotes forms (59.5% ± 0.08% and 98.1% ± 0.46%) and the number of amastigotes/macrophages (79.80% ± 0.05% and 96.0% ± 0.16%), through increasing induction of microbicide molecule NO. Additionally, ADMET-Tox in silico predictions showed drug-like features and free of toxicological risks. The molecular docking studies with arginase and gp63 showed that relevant intermolecular interactions could explain the experimental results. Therefore, these results reinforce that benzoylguanidines could be a starting scaffold for the search for new antileishmanial drugs.Communicated by Ramaswamy H. Sarma.

Ageing impairs protective immunity and promotes susceptibility to murine visceral leishmaniasis

It is well accepted that the impact of diseases is generally more detrimental in elderly individuals than in younger ones. Changes in the immune system due to ageing can directly affect the ability to respond effectively to infections and may contribute to the higher morbidities and mortalities in the elderly population. Leishmaniasis is a complex of clinically unique diseases caused by obligate intracellular protozoa belonging to genus Leishmania, wherein visceral leishmaniasis (VL) is the most severe form and is fatal if left untreated. In this study, aged mice (72 weeks old) presented increased susceptibility to L. infantum infection compared to younger mice (4–6-week-old), with notable parasitism in both the spleen and liver, as well as exhibiting hepatosplenomegaly. A pronounced inflammatory profile was observed in the aged-infected mice, with excessive production of TNF-α and nitrite, along with diminished IFN-γ production and reduced proliferative capacity of T cells (assessed by expression of the Ki67 marker). Additionally, both CD4+ and CD8+ T cells from the aged-infected mice presented increased expression of the inhibitory receptors PD-1 and KLRG1 that strongly correlated with the parasitism found in the liver and spleen of this group. Overall, the data reported in this study suggests for the first time that ageing may negatively impact the VL outcome and provides a perspective for new therapeutic strategies involving manipulation of immunosenescence features against Leishmania infection.

Immune Responses in Leishmaniases: An Overview

Leishmaniasis is a parasitic, widespread, and neglected disease that affects more than 90 countries in the world. More than 20 Leishmania species cause different forms of leishmaniasis that range in severity from cutaneous lesions to systemic infection. The diversity of leishmaniasis forms is due to the species of parasite, vector, environmental and social factors, genetic background, nutritional status, as well as immunocompetence of the host. Here, we discuss the role of the immune system, its molecules, and responses in the establishment, development, and outcome of Leishmaniasis, focusing on innate immune cells and Leishmania major interactions.

The Ecto-5 ′ nucleotidase/CD73 Mediates Leishmania amazonensis Survival in Macrophages

Endogenous nucleotides produced by various group of cells under inflammatory conditions act as potential danger signals in vivo. Extracellularly released nucleotides such as ATP are rapidly hydrolyzed to adenosine by the coordinated ectonucleotidase activities of CD39 and CD73. Leishmania is an obligate intracellular parasite of macrophages and capable of modulating host immune response in order to survive and multiply within host cells. In this study, the activity of CD73 induced by Leishmania amazonensis in infected macrophages has been investigated and correlated with parasite survival and infection in vitro. For this, the expression of CD39 and CD73, by flow cytometry, in murine peritoneal macrophages infected with metacyclic promastigotes of L. amazonensis has been analyzed. Our results showed that L. amazonensis-infected macrophages, unlike LPS-treated macrophages, increased CD73 expression. It was also noted that when CD73 enzymatic activity was blocked by α, β-methyleneadenosine 5′-diphosphate sodium salt (APCP), macrophage parasitism was significantly decreased. Interestingly, these effects were not associated with the production of TNF-α, IL-10, or nitric oxide (NO). Together, these data demonstrate that L. amazonensis induces a regulatory phenotype in macrophages, which by activating the CD39/CD73 pathway allows parasite survival through the action of immunomodulatory adenosine receptors.

N-Acetylglucosamine Sensing and Metabolic Engineering for Attenuating Human and Plant Pathogens

During evolution, both human and plant pathogens have evolved to utilize a diverse range of carbon sources. N-acetylglucosamine (GlcNAc), an amino sugar, is one of the major carbon sources utilized by several human and phytopathogens. GlcNAc regulates the expression of many virulence genes of pathogens. In fact, GlcNAc catabolism is also involved in the regulation of virulence and pathogenesis of various human pathogens, including Candida albicans, Vibrio cholerae, Leishmania donovani, Mycobacterium, and phytopathogens such as Magnaporthe oryzae. Moreover, GlcNAc is also a well-known structural component of many bacterial and fungal pathogen cell walls, suggesting its possible role in cell signaling. Over the last few decades, many studies have been performed to study GlcNAc sensing, signaling, and metabolism to better understand the GlcNAc roles in pathogenesis in order to identify new drug targets. In this review, we provide recent insights into GlcNAc-mediated cell signaling and pathogenesis. Further, we describe how the GlcNAc metabolic pathway can be targeted to reduce the pathogens’ virulence in order to control the disease prevalence and crop productivity.

Botryosphaeran, [(1 → 3)(1 → 6)-β-D-glucan], induces apoptosis-like death in promastigotes of Leishmania amazonensis, and exerts a leishmanicidal effect on infected macrophages by activating NF-kB and producing pro-inflammatory molecules

Leishmaniasis is an infectious-parasitic disease caused by the protozoan Leishmania spp. The available treatments are based upon expensive drugs bearing adverse side-effects. The search for new therapeutic alternatives that present a more effective action without causing adverse effects to the patient is therefore important. The objective of this study was to evaluate the in vitro effect of botryosphaeran, a (1 → 3)(1 → 6)-β-D-glucan, on the promastigote and intracellular amastigote forms of Leishmania amazonensis. The direct activity of botryosphaeran on promastigote forms was evaluated in vitro and inhibited proliferation, the IC50 7 μg/mL in 48 h was calculated. After 48 h treatment, botryosphaeran induced nitric oxide production (NO), caused mitochondrial membrane hyperpolarization, increased reactive oxygen species (ROS), and accumulation of lipid vesicles in promastigotes, resulting in apoptosis, necrosis and autophagy, and was accompanied by morphological and ultrastructural changes. The range of concentrations used did not alter the viability of peritoneal macrophages from BALB/c mice and erythrocytes of sheep. Botryosphaeran was able to reduce the number of infected macrophages and the number of amastigotes per macrophage at 12.5 μg/mL (50.75% ± 6.48), 25 μg/mL (55.66% ± 3.93) and 50 μg/mL (72.9% ± 6.98), and IC50 9.3 μg/mL (±0.66) for intracellular amastigotes forms. The leishmanicidal effect was due to activation of NF-κB and promoted an increase in pro-inflammatory cytokines (TNF-α and IL-6), iNOS and microbial-derived ROS and NO, in addition to decreasing the levels of SOD. Based upon the data obtained, we infer that botryosphaeran exerted an active leishmanicidal and immunomodulatory effect, acting on promastigotes through autophagic, apoptotic and necrosis processes, and in the intracellular amastigote form, through the action of ROS and NO.

Therapeutic Delivery of Nitric Oxide Utilizing Saccharide-Based Materials

As a gasotransmitter, nitric oxide (NO) regulates physiological pathways and demonstrates therapeutic effects such as vascular relaxation, anti-inflammation, antiplatelet, antithrombosis, antibacterial, and antiviral properties. However, gaseous NO has high reactivity and a short half-life, so NO delivery and storage are critical questions to be solved. One way is to develop stable NO donors and the other way is to enhance the delivery and storage of NO donors from biomaterials. Most of the researchers studying NO delivery and applications are using synthetic polymeric materials, and they have demonstrated significant therapeutic effects of these NO-releasing polymeric materials on cardiovascular diseases, respiratory disease, bacterial infections, etc. However, some researchers are exploring saccharide-based materials to fulfill the same tasks as their synthetic counterparts while avoiding the concerns of biocompatibility, biodegradability, and sustainability. Saccharide-based materials are abundant in nature and are biocompatible and biodegradable, with wide applications in bioengineering, drug delivery, and therapeutic disease treatments. Saccharide-based materials have been implemented with various NO donors (like S-nitrosothiols and N-diazeniumdiolates) via both chemical and physical methods to deliver NO. These NO-releasing saccharide-based materials have exhibited controlled and sustained NO release and demonstrated biomedical applications in various diseases (respiratory, Crohn's, cardiovascular, etc.), skin or wound applications, antimicrobial treatment, bone regeneration, anticoagulation, as well as agricultural and food packaging. This review aims to highlight the studies in methods and progress in developing saccharide-based NO-releasing materials and investigating their potential applications in biomedical, bioengineering, and disease treatment.

Delineating infection strategies of Leishmania donovani secretory proteins in Human through host-pathogen protein Interactome prediction

Interactions of Leishmania donovani secretory virulence factors with the host proteins and their interplay during the infection process in humans is poorly studied in Visceral Leishmaniasis. Lack of a holistic study of pathway level de-regulations caused due to these virulence factors leads to a poor understanding of the parasite strategies to subvert the host immune responses, secure its survival inside the host and further the spread of infection to the visceral organs. In this study, we propose a computational workflow to predict host-pathogen protein interactome of L.donovani secretory virulence factors with human proteins combining sequence-based Interolog mapping and structure-based Domain Interaction mapping techniques. We further employ graph theoretical approaches and shortest path methods to analyze the interactome. Our study deciphers the infection paths involving some unique and understudied disease-associated signaling pathways influencing the cellular phenotypic responses in the host. Our statistical analysis based in silico knockout study unveils for the first time UBC, 1433Z and HS90A mediator proteins as potential immunomodulatory candidates through which the virulence factors employ the infection paths. These identified pathways and novel mediator proteins can be effectively used as possible targets to control and modulate the infection process further aiding in the treatment of Visceral Leishmaniasis.

The Paradox of a Phagosomal Lifestyle: How Innate Host Cell-Leishmania amazonensis Interactions Lead to a Progressive Chronic Disease

Intracellular phagosomal pathogens represent a formidable challenge for innate immune cells, as, paradoxically, these phagocytic cells can act as both host cells that support pathogen replication and, when properly activated, are the critical cells that mediate pathogen elimination. Infection by parasites of the Leishmania genus provides an excellent model organism to investigate this complex host-pathogen interaction. In this review we focus on the dynamics of Leishmania amazonensis infection and the host innate immune response, including the impact of the adaptive immune response on phagocytic host cell recruitment and activation. L. amazonensis infection represents an important public health problem in South America where, distinct from other Leishmania parasites, it has been associated with all three clinical forms of leishmaniasis in humans: cutaneous, muco-cutaneous and visceral. Experimental observations demonstrate that most experimental mouse strains are susceptible to L. amazonensis infection, including the C57BL/6 mouse, which is resistant to other species such as Leishmania major, Leishmania braziliensis and Leishmania infantum. In general, the CD4⁺ T helper (Th)1/Th2 paradigm does not sufficiently explain the progressive chronic disease established by L. amazonensis, as strong cell-mediated Th1 immunity, or a lack of Th2 immunity, does not provide protection as would be predicted. Recent findings in which the balance between Th1/Th2 immunity was found to influence permissive host cell availability via recruitment of inflammatory monocytes has also added to the complexity of the Th1/Th2 paradigm. In this review we discuss the roles played by innate cells starting from parasite recognition through to priming of the adaptive immune response. We highlight the relative importance of neutrophils, monocytes, dendritic cells and resident macrophages for the establishment and progressive nature of disease following L. amazonensis infection.

Curzerene antileishmania activity: Effects on Leishmania amazonensis and possible action mechanisms

Leishmaniasis is a set of infectious diseases with high rates of morbidity and mortality, it affects millions of people around the world. Treatment, mainly with pentavalent antimonials, presents significant toxicity and many cases of resistance. In previous works we have demonstrated the effective and selective antileishmanial activity of Eugenia uniflora L. essential oil, being constituted (47.3%) by the sesquiterpene curzerene. Considering the high rate of parasite inhibition demonstrated for E. uniflora essential oil, and the significant presence of curzerene in the oil, this study aimed to evaluate its antileishmania activity and possible mechanisms of action. Curzerene was effective in inhibiting the growth of promastigotes (IC₅₀ 3.09 ± 0.14 µM) and axenic amastigotes (EC₅₀ 2.56 ± 0.12 µM), with low cytotoxicity to RAW 264.7 macrophages (CC₅₀ 83.87 ± 4.63 µM). It was observed that curzerene has direct effects on the parasite, inducing cell death by apoptosis with secondary necrotic effects (producing pores in the plasma membrane). Curzerene proved to be even more effective against intra-macrophage amastigote forms, with an EC₅₀ of 0.46 ± 0.02 µM. The selectivity index demonstrated by curzerene on these parasite forms was 182.32, being respectively 44.15 and 8.47 times more selective than meglumine antimoniate and amphotericin B. The antiamastigote activity of curzerene was associated with immunomodulatory activity, as it increased TNF-α, IL-12, and NO levels, and lysosomal activity, and decreased IL-10 and IL-6 cytokine levels detected in macrophages infected and treated. In conclusion, our results demonstrate that curzerene is an effective and selective antileishmanial agent, a candidate for in vivo investigation in models of antileishmanial activity.

Protective CD4+ Th1 cell-mediated immunity is reliant upon execution of effector function prior to the establishment of the pathogen niche

Intracellular infection with the parasite Leishmania major features a state of concomitant immunity in which CD4+ T helper 1 (Th1) cell-mediated immunity against reinfection coincides with a chronic but sub-clinical primary infection. In this setting, the rapidity of the Th1 response at a secondary site of challenge in the skin represents the best correlate of parasite elimination and has been associated with a reversal in Leishmania-mediated modulation of monocytic host cells. Remarkably, the degree to which Th1 cells are absolutely reliant upon the time at which they interact with infected monocytes to mediate their protective effect has not been defined. In the present work, we report that CXCR3-dependent recruitment of Ly6C+ Th1 effector (Th1EFF) cells is indispensable for concomitant immunity and acute (<4 days post-infection) Th1EFF cell-phagocyte interactions are critical to prevent the establishment of a permissive pathogen niche, as evidenced by altered recruitment, gene expression and functional capacity of innate and adaptive immune cells at the site of secondary challenge. Surprisingly, provision of Th1EFF cells after establishment of the pathogen niche, even when Th1 cells were provided in large quantities, abrogated protection, Th1EFF cell accumulation and IFN-γ production, and iNOS production by inflammatory monocytes. These findings indicate that protective Th1 immunity is critically dependent on activation of permissive phagocytic host cells by preactivated Th1EFF cells at the time of infection.

Green Synthesis and Characterization of Carboxymethyl Cellulose Fabricated Silver-Based Nanocomposite for Various Therapeutic Applications

Purpose

The current study proposed the simple, eco-friendly and cost-effective synthesis of carboxymethyl cellulose (CMC) structured silver-based nanocomposite (CMC-AgNPs) using Syzygium aromaticum buds extract.

Methods

The CMC-AgNPs were characterized by ultraviolet (UV) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transmission infra-red (FTIR), energy-dispersive X-ray (EDX), and dynamic light scattering (DLS) techniques. The synthesized nanocomposites were evaluated for their bactericidal kinetics, in-vivo anti-inflammatory, anti-leishmaniasis, antioxidant and cytotoxic activities using different in-vitro and in-vivo models.

Results

The spherical shape nanocomposite of CMC-AgNPs was synthesized with the mean size range of 20–30 nm, and the average pore diameter is 18.2 nm while the mean zeta potential of −31.6 ± 3.64 mV. The highly significant (P < 0.005) antibacterial activity was found against six bacterial strains with the ZIs of 24.6 to 27.9 mm. More drop counts were observed in Gram-negative strains after 10 min exposure with CMC-AgNPs. Significant damage in bacterial cell membrane was also observed in atomic force microscopy (AFM) after treated with CMC-AgNPs. Nanocomposite showed highly significant anti-inflammatory activity in cotton pellet induced granuloma model (Phase I) in rats with the mean inhibitions of 43.13% and 48.68% at the doses of 0.025 and 0.05 mg/kg, respectively, when compared to control. Reduction in rat paw edema (Phase II) was also highly significant (0.025 mg/kg; 42.39%; 0.05 mg/kg, 47.82%). At dose of 0.05 mg/kg, CMC-AgNPs caused highly significant decrease in leukocyte counts (922 ± 83), levels of CRP (8.4 ± 0.73 mg/mL), IL-1 (177.4 ± 21.3 pg/mL), IL-2 (83.7 ± 11.5 pg/mL), IL-6 (83.7 ± 11.5 pg/mL) and TNF-α (18.3 ± 5.3 pg/mL) as compared to control group. CMC-AgNPs produced highly effective anti-leishmaniasis activity with the viable Leishmania major counts decreased up to 36.7% within 24 h, and the IC₅₀ was found to be 28.41 μg/mL. The potent DPPH radical scavenging potential was also observed for CMC-AgNPs with the IC₅₀ value of 112 μg/mL. Furthermore, the cytotoxicity was assessed using HeLa cell lines with the LC₅₀ of 108.2 μg/mL.

Conclusion

The current findings demonstrate positive attributes of CMC fabricated AgNPs as a promising antibacterial, anti-inflammatory, anti-leishmaniasis, and antioxidant agent with low cytotoxic potential.

Toll-like receptor-7/8 agonist kill Leishmania amazonensis by acting as pro-oxidant and pro-inflammatory agent

OBJECTIVES

Evaluation of the anti-Leishmanial activity of imidazoquinoline-based TLR7/8 agonists.

METHODS

TLR7/8-active imidazoquinolines (2 and 3) were synthesized and assessed for activity against Leishmania amazonensis-intracellular amastigotes using mouse peritoneal macrophages. The production of reactive oxygen species (ROS), nitric oxide (NO) and cytokines was determined in infected and non-infected macrophages.

KEY FINDINGS

The imidazoquinolines, 2 and 3, were primarily agonists of TLR7 with compound 3 also showing modest TLR8 activity. Docking studies showed them to occupy the same binding pocket on TLR7 and 8 as the known agonists, imiquimod and resiquimod. Compounds 2 and 3 inhibited the growth of L. amazonensis-intracellular amastigotes with the most potent compound (3, IC50 = 5.93 µM) having an IC50 value close to miltefosine (IC50 = 4.05 µM), a known anti-Leishmanial drug. Compound 3 induced macrophages to produce ROS, NO and inflammatory cytokines that likely explain the anti-Leishmanial effects.

CONCLUSIONS

This study shows that activating TLR7 using compounds 2 or 3 induces anti-Leishmanial activity associated with induction of free radicals and inflammatory cytokines able to kill the parasites. While 2 and 3 had a very narrow cytotoxicity window for macrophages, this identifies the possibility to further develop this chemical scaffold to less cytotoxic TLR7/8 agonist for potential use as anti-Leishmanial drug.

Larval excretion/secretion of dipters of Lucilia cuprina species induces death in promastigote and amastigote forms of Leishmania amazonensis

Leishmaniasis is a neglected tropical disease that affects millions of people around the world. Larval excretion/secretion (ES) of the larvae of flies of the Calliphoridae family has microbicidal activity against Gram-positive and Gram-negative bacteria, in addition to some species of Leishmania. Our study aimed at assessing the in vitro efficacy of Lucilia cuprina larval ES against the promastigote and amastigote forms of Leishmania amazonensis, elucidating possible microbicidal mechanisms and routes of death involved. Larval ES was able to inhibit the viability of L. amazonensis at all concentrations, induce morphological and ultrastructural changes in the parasite, retraction of the cell body, roughness of the cytoplasmic membrane, leakage of intracellular content, ROS production increase, induction of membrane depolarization, and mitochondrial swelling, the formation of cytoplasmic lipid droplets and phosphatidylserine exposure, thus indicating the possibility of apoptosis-like death. To verify the efficacy of larval ES on amastigote forms, we performed a phagocytic assay, measurement of total ROS, and NO. Treatment using larval ES reduced the percentage of infection and the number of amastigotes per macrophage of lineage J774A.1 at all concentrations, increasing the production of ROS and TNF-α, thus indicating possible pro-inflammatory immunomodulation and oxidative damage. Therefore, treatment using larval ES is effective at inducing the death of promastigotes and amastigotes of L. amazonensis even at low concentrations.

AgNP-PVP-meglumine antimoniate nanocomposite reduces Leishmania amazonensis infection in macrophages

BACKGROUND

Leishmaniasis is an infectious disease caused by parasites of the genus Leishmania and presents different clinical manifestations. The adverse effects, immunosuppression and resistant strains associated with this disease necessitate the development of new drugs. Nanoparticles have shown potential as alternative antileishmanial drugs. We showed in a previous study the biosynthesis, characterization and ideal concentration of a nanocomposite that promoted leishmanicidal activity. In the present study, we conducted a specific analysis to show the mechanism of action of AgNP-PVP-MA (silver nanoparticle-polyvinylpyrrolidone-[meglumine antimoniate (Glucantime®)]) nanocomposite during Leishmania amazonensis infection in vitro.

RESULTS

Through ultrastructural analysis, we observed significant alterations, such as the presence of small vesicles in the flagellar pocket and in the extracellular membrane, myelin-like structure formation in the Golgi complex and mitochondria, flagellum and plasma membrane rupture, and electrodense material deposition at the edges of the parasite nucleus in both evolutive forms. Furthermore, the Leishmania parasite infection index in macrophages decreased significantly after treatment, and nitric oxide and reactive oxygen species production levels were determined. Additionally, inflammatory, and pro-inflammatory cytokine and chemokine production levels were evaluated. The IL-4, TNF-α and MIP-1α levels increased significantly, while the IL-17 A level decreased significantly after treatment.

CONCLUSIONS

Thus, we demonstrate in this study that the AgNP-PVP-MA nanocomposite has leishmanial potential, and the mechanism of action was demonstrated for the first time, showing that this bioproduct seems to be a potential alternative treatment for leishmaniasis.

Differential inflammatory responses associated with Leishmania major and L tropica in culture

BACKGROUND

Anthroponotic cutaneous leishmaniasis (ACL) due to Leishmania tropica and zoonotic CL (ZCL) due to L major have different clinical and epidemiological features.

OBJECTIVES

To determine whether pro-inflammatory cytokines are involved in diverse pathogenicity of Leishmania species causing CL.

PATIENTS/METHODS

The capacity of L major/L tropica to modulate expression of IL-1β, IL-8 (CXCL8), IFN-γ, TNF-α and MCP-1 (CCL2) in peripheral blood mononuclear cells (PBMCs) and monocyte-derived macrophages (MDMs) was evaluated by real-time RT-PCR technique.

RESULTS

PBMCs from both ZCL and ACL cases expressed significantly higher IFN-γ (P < .001) and TNF-α (P < .05) compared with healthy controls (HC). PBMCs from ACL patients expressed significantly higher IL-1β and IL-8 compared with ZCL patients and HC when stimulated with live L major or L tropica promastigotes (P < .001). After 4 and 10 hours, L major-infected MDMs expressed significantly higher IFN-γ (P < .05), and after 10 hours, L tropica-infected MDMs expressed significantly higher IL-1β, IFN-γ and IL-8 compared with noninfected cells (P < .05).

CONCLUSIONS

This study shows differential parasite-mediated stimulations of the inflammatory response with L major vs L tropica ex vivo. Pro-inflammatory cytokines particularly IL-8 (CXCL8) and IL-1β might contribute in diverse clinical features of CL such as longer duration of lesion persistence in ACL patients.

The Modulation of NADPH Oxidase Activity in Human Neutrophils by Moroccan Strains of Leishmania major and Leishmania tropica Is Not Associated with p47phox Phosphorylation

Polymorphonuclear neutrophils (PMNs) are the first phagocyte recruited and infected by Leishmania. They synthetize superoxide anions (O2-) under the control of the NADPH oxidase complex. In Morocco, Leishmania major and L. tropica are the main species responsible for cutaneous leishmaniasis (CL). The impact of these parasites on human PMN functions is still unclear. We evaluated the in vitro capacity of primary Moroccan strains of L. major and L. tropica to modulate PMN O2- production and p47phox phosphorylation status of the NADPH oxidase complex. PMNs were isolated from healthy blood donors, and their infection rate was measured by microscopy. O2- production was measured by superoxide dismutase-inhibitable reduction of cytochrome C. P47phox phosphorylation was analyzed by Western blot using specific antibodies against Ser328 and Ser345 sites. Whereas we did not observe any difference in PMN infectivity rate, our results indicated that only L. tropica promastigotes inhibited both fMLF- and PMA-mediated O2- production independently of p47phox phosphorylation. Leishmania soluble antigens (SLAs) from both species significantly inhibited O2- induced by fMLF or PMA. However, they only decreased PMA-induced p47phox phosphorylation. L. major and L. tropica modulated differently O2- production by human PMNs independently of p47phox phosphorylation. The inhibition of ROS production by L. tropica could be a mechanism of its survival within PMNs that might explain the reported chronic pathogenicity of L. tropica CL.

Nitric-oxide releasing chitosan nanoparticles towards effective treatment of cutaneous leishmaniasis

Cutaneous leishmaniasis (CL) is a major public health problem caused by Leishmania parasites that produce destructive and disfiguring skin conditions. There is an urgent need for alternative topical therapies due to the limitations of current systemic treatments. Recently, we have synthesized nitric oxide-releasing chitosan nanoparticles (NONPs) and shown their potential in vitro against Leishmania amazonensis. Herein we evaluated the application of NONPs for the treatment of CL on infected BALB/c mice. Mice were treated with topical administration of increasing concentrations of NONPs and disease progression was investigated regarding parasite load, lesion thickness, and pain score. As a result, we observed a dose-dependent NONPs effect. Parasite burden and lesion thickness were substantially lower on animals receiving NONPs at a 2 mM concentration compared to untreated control. Moreover, the clinical presentation of the lesions did not show any visible signs of ulcer, suggesting clinical healing in these animals. This successful outcome was sustained for at least 21 days after therapy even in one single dose. Thus, we demonstrate that NONPs are suitable for topical administration, and represent an attractive approach to treat CL.

Three decades of clinical trials on immunotherapy for human leishmaniases: a systematic review and meta-analysis

Aim: Current treatments for leishmaniases are not satisfactory, thus alternatives are needed. We searched for clinical trials with immunotherapeutic approaches for patients with leishmaniasis. Materials & methods: Out of 205 articles, 24 clinical trials were selected, and eight submitted to meta-analysis. Results: A reduction in healing time was observed in patients with tegumentary leishmaniasis treated with pentavalent antimony plus granulocyte-macrophage colony-stimulating factor, and therapeutic vaccines. Overall meta-analysis indicated that immunotherapy associated with the standard chemotherapy generated a significantly reduced risk of treatment failure than the pentavalent antimony alone (p = 0.03). Conclusion: Our review confirmed the efficacy of immunotherapies for the treatment of cutaneous and visceral leishmaniasis and highlighted the importance of clinical trials using immunotherapies for leishmaniases.

Therapeutic Potential of Green Synthesized Copper Nanoparticles Alone or Combined with Meglumine Antimoniate (Glucantime®) in Cutaneous Leishmaniasis

Background: In recent years, the focus on nanotechnological methods in medicine, especially in the treatment of microbial infections, has increased rapidly. Aim: The present study aims to evaluate in vitro and in vivo antileishmanial effects of copper nanoparticles (CuNPs) green synthesized by Capparis spinosa fruit extract alone and combined with meglumine antimoniate (MA). Methods: CuNPs were green synthesized by C. spinosa methanolic extract. The in vitro antileishmanial activity of CuNPs (10–200 µg/mL) or MA alone (10–200 µg/mL), and various concentrations of MA (10–200 μg/mL) along with 20 μg/mL of CuNPs, was assessed against the Leishmania major (MRHO/IR/75/ER) amastigote forms and, then tested on cutaneous leishmaniasis induced in male BALB/c mice by L. major. Moreover, infectivity rate, nitric oxide (NO) production, and cytotoxic effects of CuNPs on J774-A1 cells were evaluated. Results: Scanning electron microscopy showed that the particle size of CuNPs was 17 to 41 nm. The results demonstrated that CuNPs, especially combined with MA, significantly (p < 0.001) inhibited the growth rate of L. major amastigotes and triggered the production of NO (p < 0.05) in a dose-dependent manner. CuNPs also had no significant cytotoxicity in J774 cells. The mean number of parasites was significantly (p < 0.05) reduced in the infected mice treated with CuNPs, especially combined with MA in a dose-dependent response. The mean diameter of the lesions decreased by 43 and 58 mm after the treatment with concentrations of 100 and 200 mg/mL of CuNPs, respectively. Conclusion: The findings of the present study demonstrated the high potency and synergistic effect of CuNPs alone and combined with MA in inhibiting the growth of amastigote forms of L. major, as well as recovery and improving cutaneous leishmaniasis (CL) induced by L. major in BALB/c mice. Additionally, supplementary studies, especially in clinical settings, are required.

Eugenia piauhiensis Vellaff. essential oil and γ-elemene its major constituent exhibit antileishmanial activity, promoting cell membrane damage and in vitro immunomodulation

Leishmaniasis is considered as one of the most Neglected Tropical Diseases (NTDs) in the world, caused by protozoan parasites of the genus Leishmania. Treatment of leishmaniasis by chemotherapy remains a challenge because of limited efficacy, toxic side effects, and drug resistance. The search for new therapeutic agents from natural sources has been a constant for the treatment of diseases such as leishmaniasis. The objective of this study was to evaluate the biological activity of Eugenia piauhiensis Vellaff. essential oil (EpEO) and its major constituent γ-elemene on promastigote and amastigote forms of Leishmania (Leishmania) amazonensis, its cytotoxicity, and possible mechanisms of action. EpEO was more active (IC₅₀ 6.43 ± 0.18 μg/mL) against promastigotes than γ-elemene [9.82 ± 0.15 μg/mL (48.05 ± 0.73 μM)] and the reference drug miltefosine [IC₅₀ 17.25 ± 0.26 μg/mL (42.32 ± 0.64 μM)]. EpEO and γ-elemene exhibited low cytotoxicity against J774.A1 macrophages, with CC₅₀ 225.8 ± 3.57 μg/mL and 213.21 ± 3.3 μg/mL (1043 ± 16.15 μM), respectively. Additionally, EpEO and γ-elemene present direct activity against the parasite, decreasing plasma membrane integrity. EpEO and γ-elemene also proved to be even more active against intracellular amastigotes of the parasite [IC₅₀ 4.59 ± 0.07 μg/mL and 8.06 ± 0.12 μg/mL (39.44 ± 0.59 μM)], respectively), presenting indirect effects through macrophage activity modulation. Anti-amastigote activity was associated with increased TNF-α, IL-12, NO, and ROS levels. In conclusion, our results suggest EpEO and γ-elemene as promising candidates for new drug development against leishmaniasis.

Development of new combination anti-leishmanial complexes: Triphenyl Sb(V) mono-hydroxy mono-quinolinolates

In seeking to develop single entity combination anti-Leishmanial complexes six heteropletic organometallic Sb(V) hydroxido quinolinolate complexes of general formula [SbPh₃(C₉H₄NORR')(OH)] have been synthesised and characterised, derived from a series of halide substituted quinolinols (8-hydroxyquinolines). Single crystal X-ray diffraction on all the complexes show a common distorted six-coordinate octahedral environment at the Sb(V) centre, with the aryl groups and nitrogen atom of quinolinolate ligand bonding in the equatorial planes, with the two oxygen atoms (hydroxyl and quinolinolate) occupying the axial plane in an almost linear configuration. Each complex was tested for their anti-promastigote activity and mammalian cytotoxicity and a selectivity indices established. The complexes displayed excellent anti-promastigote activity (IC₅₀: 2.03-3.39 μM) and varied mammalian cytotoxicity (IC₅₀: 12.7-46.9 μM), leading to a selectivity index range of 4.52-16.7. All complexes displayed excellent anti-amastigote activity with a percentage infection range of 2.25%-9.00%. All complexes performed substantially better than the parent quinolinols and comparable carboxylate complexes [SbPh₃(O₂CRR')₂] indicating the synergistic role of the Sb(V) and quinolinol moieties in increasing parasite mortality. Two of the complexes [SbPh₃(C₉H₄NOBr₂)(OH)] 4, [SbPh₃(C₉H₄NOI₂)(OH)] 5, provide an ideal combination of high selective and good activity towards the leishmanial amastigotes and offer the potential as good lead compounds.

Leishmanial aspartyl-tRNA synthetase: Biochemical, biophysical and structural insights

Aminoacyl tRNA synthetases (aaRSs) are integral components of protein biosynthesis along with several non-canonical cellular processes. Inhibition studies of aaRSs presented these enzymes as promising drug targets in many pathogens, however aspartyl tRNA synthetase has not been studied in trypanosomatids despite its essentiality. Hence, full-length ORF of Leishmania donovani aspartyl tRNA synthetase (LdaspRS) was cloned and purified to homogeneity followed by molecular mass determination. The aminoacylation assay established that the purified protein performs its function optimally at physiological pH and temperature. The kinetic parameters of LdaspRS revealed the affinity of l-aspartate towards the enzyme to be very much lower than the cofactor. Our study also highlights the moonlighting function of LdaspRS to stimulate the pro-inflammatory cytokines and nitric oxide generation by host macrophage. Furthermore, CD and intrinsic tryptophan fluorescence measurements showed the changes in structural conformation at varying pH, denaturants and ligands. The modelled LdaspRS structure presented all the specific characteristics of class II aaRSs, while in silico study suggested binding of pyrimidine-derived inhibitors in its cofactor binding site with high affinity followed by validation using MD simulation. Altogether, this study could provide a platform for exploring LdaspRS to develop potential therapeutics against leishmaniasis.

Regulation of macrophage subsets and cytokine production in leishmaniasis

Macrophages are host cells for parasites of the genus Leishmania where they multiply inside parasitophorous vacuoles. Paradoxically, macrophages are also the cells responsible for killing or controlling parasite growth, if appropriately activated. In this review, we will cover the patterns of macrophage activation and the mechanisms used by the parasite to circumvent being killed. We will highlight the impacts of the vector bite on macrophage activation. Finally, we will discuss the ontogeny of macrophages that are infected by Leishmania spp.

In Vitro Modulator Effect of Total Extract from the Endophytic Paenibacillus polymyxa RNC-D in Leishmania (Leishmania) amazonensis and Macrophages

Leishmaniases are diseases with high epidemiological relevance and wide geographical distribution. In Brazil, Leishmania (Leishmania) amazonensis is related to the tegumentary form of leishmaniasis. The treatment for those diseases is problematic as the available drugs promote adverse effects in patients. Therefore, it is important to find new therapeutic targets. In this regard, one alternative is the study of biomolecules produced by endophytic microorganisms. In this study, the total extract produced by the endophytic Paenibacillus polymyxa RNC-D was used to evaluate the leishmanicidal, nitric oxide, and cytokines production using RAW 264.7 macrophages. The results showed that, in the leishmanicidal assay with L. amazonensis, EC50 values at the periods of 24 and 48 hours were 0.624 mg/mL and 0.547 mg/mL, respectively. Furthermore, the cells treated with the extract presented approximately 25% of infected cells with an average of 3 amastigotes/cell in the periods of 24 and 48 hours. Regarding the production of cytokines in RAW 264.7 macrophages infected/treated with the extract, a significant increase in TNF-α was observed at the periods of 24 and 48 hours in the treated cells. The concentrations of IFN-γ and IL-12 showed significant increase in 48 hours. A significant decrease in IL-4 was observed in all cells treated with the extract in 24 hours. It was observed in the treated cells that the NO production by RAW 264.7 macrophages increased between 48 and 72 hours. The endophytic Paenibacillus polymyxa RNC-D extract modulates the mediators of inflammation produced by RAW 264.7 macrophages promoting L. amazonensis death. The immunomodulatory effects might be a promising target to develop new immunotherapeutic and antileishmanial drugs.

Intralesional Injection of Mouse Mesenchymal Stem Cells Reduces IL-10 Production and Parasite Burden in L. major Infected BALB/c Mice

Objective

Leishmaniasis is of public health problems, especially in endemic areas. The activation of macrophages, as the main host of leishmania and promotion of the TH1 immune responses, are the main goal of im-munotherapy methods. Recently, the immunomodulatory role of mesenchymal stem cells (MSCs) in infectious disease has been considered. Different in vitro studies demonstrated the immunostimulatory effect of MSCs on macrophages in response to L.major. In this study, the effect of MSCs on cutaneous leishmaniasis in BALB/c mice was assessed.

Materials and Methods

To do this experimental research, BALB/c mice infected with L. major that was followed by multiple subcutaneous injections of MSCs at infection site at different intervals. Footpad thickness, spleen parasite burden, lymph node, and spleen cytokine production were measured to determine the efficacy of cell therapy.

Results

Significant (P<0.05) reduction in footpad thickness and delayed wound formation was observed in MSCs treated group. The spleen of the MSCs-treated group indicated a two-fold reduction in parasite burden compared with non-treated infected mice. In addition, nitric oxide (NO), interleukin-10 (IL-10), and tumor necrosis factor-alpha (TNF-α) production of lymph node isolated cells and splenocytes changed to the benefit of macrophage activation in response to L. major in MSCs treated group. A two-fold increase in interferon-gamma (IFN-γ) production in the lymph node was determined in the MSCs-treated group.

Conclusion

Although MSCs therapy could not clear the parasite, the results confirm the ability of MSCs to enhance immune responses against leishmania by induction of inflammatory responses and slowing down the spread of parasites. However, further studies needed to improve the efficacy of this method and provide a therapeutic protocol.

Reconciling protective and pathogenic roles of the NLRP3 inflammasome in leishmaniasis

Leishmaniasis is a global health problem that affects more than 2 billion people worldwide. Recent advances in research have demonstrated critical roles for cytoplasmic sensors and inflammasomes during Leishmania spp. infection and pathogenesis. Specifically, several studies have focused on the role of nod-like receptor family, pyrin domain-containing protein 3 (NLRP3) inflammasome and inflammasome-associated cytokines IL-1β and IL-18 in leishmaniasis. Despite these studies, our understanding of the priming and activation events that lead to NLRP3 inflammasome activation during Leishmania spp. infection is limited. Furthermore, whether NLRP3 plays a protective or pathogenic role during Leishmania spp. infection is far from resolved, with some studies showing a protective role and others showing a pathogenic role. In this review, we performed a critical review of the literature to provide a current update on priming and activating signals required for NLRP3 inflammasome activation during Leishmania spp. infection. Finally, we provide a thorough review of the literature to reconcile differences in the observed protective vs pathogenic roles of the NLRP3 inflammasome during Leishmania spp. infection.

DH82 Canine and RAW264.7 Murine Macrophage Cell Lines Display Distinct Activation Profiles Upon Interaction With Leishmania infantum and Leishmania amazonensis

Leishmaniasis is an anthropozoonotic disease, and dogs are considered the main urban reservoir of the parasite. Macrophages, the target cells of Leishmania sp., play an important role during infection. Although dogs have a major importance in the epidemiology of the disease, the majority of the current knowledge about Leishmania–macrophage interaction comes from murine experimental models. To assess whether the canine macrophage strain DH82 is an accurate model for the study of Leishmania interaction, we compared its infection by two species of Leishmania (Leishmania infantum and L. amazonensis) with the murine macrophage cell line (RAW264.7). Our results demonstrated that L. amazonensis survival was around 40% at 24 h of infection inside both macrophage cell lines; however, a reduction of 4.3 times in L. amazonensis infection at 48 h post-infection in RAW 264.7 macrophages was observed. The survival index of L. infantum in DH82 canine macrophages was around 3 times higher than that in RAW264.7 murine cells at 24 and 48 h post-infection; however, at 48 h a reduction in both macrophages was observed. Surprisingly at 24 h post-infection, NO and ROS production by DH82 canine cells stimulated with LPS or menadione or during Leishmania infection was minor compared to murine RAW264.7. However, basal arginase activity was higher in DH82 cells when compared to murine RAW264.7 cells. Analysis of the cytokines showed that these macrophages present a different response profile. L. infantum induced IL-12, and L. amazonensis induced IL-10 in both cell lines. However, L. infantum and L. amazonensis also induced TGF-β in RAW 264.7. CD86 and MHC expression showed that L. amazonensis modulated them in both cell lines. Conversely, the parasite load profile did not show significant difference between both macrophage cell lines after 48 h of infection, which suggests that other mechanisms of Leishmania control could be involved in DH82 cells.

Antioxidant defense in the eyes of immunocompetent and immunosuppressed mice infected with Acanthamoeba spp

Background

Acanthamoeba spp. are ubiquitous pathogens which cause granulomatous amoebic encephalitis and disseminated infection. Moreover, Acanthamoeba spp. infection of the cornea leads to Acanthamoeba keratitis. Our previous study showed that the infection of an eyeball may also take place via the migration of trophozoites through the optic nerve from the brain to the eyes. The aim of the study was to analyze the activity of enzymatic antioxidants and the concentration of non-enzymatic antioxidant in the eyes of immunocompetent and immunocompromised mice with disseminated acanthamoebiasis.

Results

In the immunocompetent mice infected with Acanthamoeba spp. we noted a significant decrease in catalase activity at 8 and 16 days post-infection (dpi). Glutathione reductase activity was significantly lower at 16 dpi compared to the control group and glutathione concentration was statistically higher at 24 dpi than in the control group. In the immunosuppressed mice, a statistically significant increase in glutathione concentration in the eye samples was found at 16 dpi compared to those not infected with Acanthamoeba spp. In the immunosuppressed mice infected with Acanthamoeba spp., glutathione peroxidase activity was statistically lower at 8 dpi, and glutathione concentration was statistically significantly higher at 16 dpi compared to the control group.

Conclusions

The inflammatory response in the eyes of hosts with experimental acanthamoebiasis led to changes in the activity of enzymatic antioxidants and the content of non-enzymatic antioxidant. Therefore, the dysregulation of antioxidants may play a role in the pathomechanism of Acanthamoeba eye infection.

Antileishmanial activity of Urtica dioica extract against zoonotic cutaneous leishmaniasis

BACKGROUND

Neglected parasitic diseases (NTDs) like cutaneous leishmaniasis (CL) have caused high mortality and morbidity rate in developing countries. This disease is considered as one of the six major tropical diseases, and has a great importance in HIV infected individuals as an opportunistic infection in those areas that both infections are endemic. This study evaluated the therapeutic effects of the Urtica dioica L (U. dioica) aqueous extract as an anti-leishmanial herbal drug in-vitro and in-vivo, and in addition to that, evaluated two vital immune system cytokines including gamma interferon (IFN-γ) and interleukin-4 (IL-4) plus nitric oxide (NO) and arginase activity against Leishmania major (L. major) infected mice.

METHODOLOGY/PRINCIPAL FINDINGS

In-vitro anti-leishmanial activity of U. dioica aqueous extract was determined using MTT method and also Parasite Rescue Transformation Assay. Also, the footpad lesion size and parasite load in BALB/c mice infected with L. major were quantified for in-vivo assessment. Furthermore, for evaluating the immune responses, the levels of IFN-γ, IL-4, NO and arginase were measured in the BALB/c mice. These results indicated that U. dioica extract significantly reduced the L. major promastigotes viability. According to the in-vitro cytotoxicity assay of the extract on Leishmania parasites (CC50) and infected macrophages (EC50), the extract had no toxicity to the macrophages, however it efficiently killed the L. major amastigotes. In addition, the lesion size, parasite load, IL-4, and ARG were decreased in the treated infected mice, however IFN-γ and NO were significantly increased.

CONCLUSIONS/SIGNIFICANCE

This study established satisfactory results in Leishmania parasite clearing both in-vivo and in-vitro. Therefore, U. dioica extract can be considered as an effective and harmless herbal compound for killing the parasite without toxicity to the host macrophages. Furthermore, it also can treat the CL by switching the mouse immune response towards a cell-mediated response (Th1); hence, it may be identified as a perfect therapeutic herbal drug for CL treatment.

Leishmania amazonensis resistance in murine macrophages: Analysis of possible mechanisms

Leishmaniasis encompass a group of infectious parasitic diseases occurring in 97 endemic countries where over one billion people live in areas at risk of infection. It is in the World Health Organization list of neglected diseases and it is considered a serious public health problem, with more than 20,000 deaths a year and high morbidity. Infection by protozoa from the genus Leishmania can cause several forms of the disease, which may vary from a self-healing ulcer to fatal visceral infection. Leishmania species, as well as host immune response and genetics can modulate the course of the disease. Leishmania sp are obligatory intracellular parasites that have macrophages as their main host cell. Depending on the activation phenotype, these cells may have distinct roles in disease development, acting in parasite control or proliferation. Therefore, the purpose of this work was to analyze Leishmania amazonensis infection in primary macrophage cells obtained from mice with two distinct genetic backgrounds, ie. different susceptibility to the infection; evaluating the cause for that difference. After infection, peritoneal macrophages from the resistant C3H/He strain presented lower parasite load when compared to susceptible BALB/c macrophages. The same was also true when cells received a Th2 stimulus after infection, but the difference was abrogated under Th1 stimulus. Nitric oxide production and arginase activity was different between the strains under Th1 or Th2 stimulus, respectively, but iNOS inhibition was unable to suppress C3H/He resistance. Hydrogen peroxide production was also higher in C3H/He than BALB/c under Th1 stimulus, but it could not account for differences in susceptibility. These results led us to conclude that, although they have an important role in parasite control, neither NO nor H2O2 production can explain C3H/He resistance to infection. Other studies are needed to uncover different mechanisms of resistance/susceptibility to L. amazonensis.

Quantification of Nitric Oxide and Reactive Oxygen Species in Leishmania-infected J774A.1 Macrophages as a Response to the in vitro treatment with a Natural Product Compound

Leishmaniasis is a parasitic disease caused by the obligatory intracellular protozoa Leishmania spp. Current therapeutic options are limited and thus, drug discovery against leishmaniasis is very important. Nevertheless, there is a great difficulty to develop therapeutic strategies against the disease because the parasite deploys various mechanisms to evade the immune system and multiply inside the host. Among the main factors of the immunity that are recruited to confront the Leishmania infection are the macrophages (MΦs) that produce effector molecules such as Nitric Oxide (NO) and Reactive Oxygen Species (ROS). Therefore, efficient drug agents should combine the antileishmanial effect of these gaseous transmitters along with the enhancement of the host's adaptive immunity. In the quest of therapeutic alternatives, natural products have been extensively studied and are considered as candidate antileishmanial agents since they exhibit specific properties in modulating the host's immune response towards an effective anti-leishmanial cell-mediated immunity capable to eliminate parasitic dissemination. In the current protocol, Leishmania-infected MΦs (J774A.1 cell line) that have been treated with various increasing concentrations of a natural compound, are tested for the production of the aforementioned molecules. In order to detect NO production, we employ the Griess colorimetric nitrite assay and quantification relies on the construction of an accurate standard curve using appropriate standards of known concentration. ROS detection and quantification is achieved by flow cytometry and relies on the use of carboxy-H₂DCFDA, an indicator that converts to a fluorescent form when interacts with ROS molecules.

Lupeol induces immunity and protective efficacy in a murine model against visceral leishmaniasis

The available chemotherapeutics for the cure of visceral leishmaniasis (VL) are linked with many detrimental effects. Moreover, VL is associated with the suppression of protective Th1 immune response of the host and induction of disease exaggerating Th2 immune response. Therefore, there is an urgent requirement of therapeutics which can augment the immune status of the host to cure this disease. In the current investigation, the antileishmanial potential of lupeol was monitored in vitro and in vivo in inbred BALB/c mice against Leishmania donovani. Lupeol showed potent antipromastigote activity via arresting parasites at sub G0/G1 phase in vitro. Lupeol significantly decreased the splenic parasite burden by inducing strong delayed-type hypersensitivity responses in contrary to untreated infected animals. The therapeutic efficacy of lupeol was observed to be similar to the reference drug, AmB. Treatment of infected animals with lupeol depicted enhanced levels of T cells and Th1 cytokines in contrast to only infected controls. Further lupeol treatment upregulated the levels of nuclear factor κ B and nitric oxide synthase genes and elevated the production of reactive oxygen species and nitric oxide. Unlike AmB, lupeol-treated infected animals did not show any toxicity. These findings are promising and indicate that lupeol can serve as a prototype drug for the cure of VL.

Caffeic acid has antipromastigote activity by apoptosis-like process; and anti-amastigote by TNF-α/ROS/NO production and decreased of iron availability

BACKGROUND

Leishmaniasis is a disease caused by protozoan parasites of the Leishmania genus whose current treatment has high cost, highly toxic, and difficult administration, which makes it very important to find alternative natural compounds of high efficiency and low cost.

PURPOSE

This study assessed the in vitro effect of caffeic acid (CA) on promastigotes and L. amazonensis-infected macrophages.

METHODS

Evaluation of the in vitro leishmanicidal activity of CA against promastigotes and L. amazonensis infected peritoneal macrophages, as well its microbicide mechanisms.

RESULTS

CA 12.5-100 µg/ml were able to inhibit promastigotes proliferation at all tested periods. The IC₅₀, 12.5 µg/ml, also altered promastigote cell morphology and cell volume accompanied by loss of mitochondrial integrity, increase in reactive oxygen species (ROS) production, phosphatidylserine exposure, and loss of plasma membrane integrity - characterizing the apoptosis-like process. Moreover, CA reduced the percentage of infected macrophages and the number of amastigotes per macrophages increasing TNF-α, ROS, NO and reducing IL-10 levels as well as iron availability.

CONCLUSION

CA showed in vitro antipromastigote and antiamostigote by increasing oxidant and inflammatory response important to eliminate the parasite.

In vitro and in vivo leishmanicidal activity of a ruthenium nitrosyl complex against Leishmania (Viannia) braziliensis

Leishmaniasis is a parasitic disease caused by protozoa of the genus Leishmania. There are many complications presented by the current treatment, as high toxicity, high cost and parasite resistance, making the development of new therapeutic agents indispensable. The present study aims to evaluate the leishmanicidal potential of ruthenium nitrosyl complex cis-[Ru(bpy)₂(SO₃)(NO)](PF₆) against Leishmania (Viannia) braziliensis. The effect of this metal complex on parasite-host interaction was evaluated by in vitro efficacy test in dermal fibrobast cells in the presence of different concentrations (1, 10, 50 and 100 μM) and by in vivo efficacy tests performed in the presence of two different concentrations of complex (100 μg/kg/day or 300 μg/kg/day) evaluating its effect on the size of the lesion and the number of parasites present in the draining lymph nodes in hamsters. Even at the lowest concentration of 1 μM of ruthenium complex, it was observed a significant decrease of the infected cells, after 24 h exposure in vitro, with total reduction at 50 μM of the ruthenium complex. In the in vivo cutaneous infection model, administration of daily doses of 300 μg/kg/day of complex reduced significantly lesion size by 51% (p < 0.05), with a 99.9% elimination of the parasites found in the lymph nodes (p < 0.001). The results suggest a promising leishmanicidal effect by that ruthenium nitrosyl complex against L. (V.) braziliensis.

Relationship between antioxidant defense in Acanthamoeba spp. infected lungs and host immunological status

The role of oxidative stress in the pathogenicity of acanthamoebiasis is an important aspect of the intricate and complex host-parasite relationship. The aim of this experimental study was to determine oxidative stress through the assessment of lipid peroxidation product (LPO) levels and antioxidant defense mechanism in Acanthamoeba spp. lung infections in immunocompetent and immunosuppressed hosts. In Acanthamoeba spp. infected immunocompetent mice we noted a significant increase in lung lipid peroxidation products (LPO) at 8 days and 16 days post infection (dpi). There was a significant upregulation in lung LPO in immunocompetent and immunosuppressed mice infected by Acanthamoeba spp. at 16 dpi. The superoxide dismutase activity decreased significantly in lungs in immunosuppressed mice at 8 dpi. The catalase activity was significantly upregulated in lungs in immunocompetent vs. immunosuppressed group and in immunocompetent vs. control mice at 16 dpi. The glutathione reductase activity was significantly lower in immunosuppressed group vs. immunosuppressed control at 24 dpi. We found significant glutathione peroxidase downregulation in immunocompetent and immunosuppressed groups vs. controls at 8 dpi, and in immunosuppressed vs. immunosuppressed control at 16 dpi. The consequence of the inflammatory response in immunocompetent and immunosuppressed hosts in the course of experimental Acanthamoeba spp. infection was the reduction of the antioxidant capacity of the lungs resulting from changes in the activity of antioxidant enzymes. Therefore, the imbalance between oxidant and antioxidant processes may play a major role in pathology associated with Acanthamoeba pneumonia.

In vitro activity of Morinda citrifolia Linn. fruit juice against the axenic amastigote form of Leishmania amazonensis and its hydrogen peroxide induction capacity in BALB/c peritoneal macrophages

OBJECTIVE

The current treatment of leishmaniasis induces strong side effects and increasing numbers of cases of resistance to reference drugs have been reported. The discovery of the therapeutic properties of active substances in plant extracts represents an interesting field of research into a more efficient treatment against leishmaniasis. Morinda citrifolia, commonly known as noni, has demonstrated promising results as antileishmanial and immunomodulator. Thus, the aim of this work was to evaluate activity against axenic amastigote and hydrogen peroxide induction capacity by M. citrifolia fruit juice.

RESULTS

Phytochemical screening identified anthraquinones, flavonoids, alkaloids, terpenoids, steroids, saponins, coumarins, phenolic compounds, tannins, anthocyanidins and chalcones. Noni juice exhibited dose-dependent activity and an IC₅₀ of 240.1 µg/mL for axenic amastigotes. An absence of endotoxins was observed at the concentrations analyzed, while no cytotoxic effects were identified. Noni juice induced hydrogen peroxide production in BALB/c peritoneal macrophages but not in macrophages infected with Leishmania amazonensis. M. citrifolia fruit juice exhibited antileishmanial activity against L. amazonensis axenic amastigotes and activated macrophages by hydrogen peroxide induction, asserting its potential for further research into new forms of leishmaniasis treatment.