The Role of Nitric Oxide and Reactive Oxygen Species in the Killing of Leishmania braziliensis by Monocytes from Patients with Cutaneous Leishmaniasis

Lupeol stimulates iNOS, TNF-α, and IL-10 expression in the U937 cell line infected with old-world Leishmania donovani

OBJECTIVE

Visceral leishmaniasis is a neglected tropical disease that can be lethal if not treated. The available medicines have severe side effects, such as toxicity and drug resistance. Various investigations are looking into new anti-leishmanial compounds from natural products that have little impact on host cells. Lupeol, a triterpenoid present in the flora of many edible plants, has been shown to have antimicrobial properties. The present study investigated the immunomodulatory effects of lupeol on U937 macrophages infected with Leishmania donovani, focusing on the expression of key cytokines and enzymes involved in the immune response.

METHODS

U937 macrophages were infected with Leishmania donovani amastigotes and treated with varying concentrations of lupeol throughout three days. The expression levels of inducible nitric oxide synthase (iNOS), tumor necrosis factor-alpha (TNF-α), and interleukin-10 (IL-10) were measured using real-time polymerase chain reaction (RT-PCR). A positive simulation of gene expression was estimated using ΔΔCT to assess relative expression.

RESULTS

The results demonstrated that lupeol significantly upregulated iNOS and TNF-α expression, especially at higher concentrations, indicating enhanced pro-inflammatory and anti-leishmanial activity. Interestingly, IL-10 expression also increased, suggesting a complex immunomodulatory role of lupeol that involves both pro-inflammatory and anti-inflammatory pathways. Pearson correlation analysis revealed a strong association between iNOS and TNF-α (0.97692), as well as a moderate correlation between iNOS and IL-10 (0.51603).

CONCLUSION

These findings suggest that lupeol may promote a balanced immune response, enhancing the body's ability to combat L. donovani while potentially mitigating excessive inflammation. Lupeol can potentially serve as a novel therapeutic agent against visceral leishmaniasis.

Effect of a thiohydantoin salt derived from l-Arginine on Leishmania amazonensis and infected cells: Insights from biological effects to molecular docking interactions

Leishmaniasis is a neglected tropical disease caused by parasites of the genus Leishmania and is responsible for more than 1 million new cases and 70,000 deaths annually worldwide. Treatment has high costs, toxicity, complex and long administration time, several adverse effects, and drug-resistant strains, therefore new therapies are urgently needed. Synthetic compounds have been highlighted in the medicinal chemistry field as a strong option for drug development against different diseases. Organic salts (OS) have multiple biological activities, including activity against protozoa such as Leishmania spp. This study aimed to investigate the in vitro leishmanicidal activity and death mechanisms of a thiohydantoin salt derived from l-arginine (ThS) against Leishmania amazonensis. We observed that ThS treatment inhibited promastigote proliferation, increased ROS production, phosphatidylserine exposure and plasma membrane permeabilization, loss of mitochondrial membrane potential, lipid body accumulation, autophagic vacuole formation, cell cycle alteration, and morphological and ultrastructural changes, showing parasites death. Additionally, ThS presents low cytotoxicity in murine macrophages (J774A.1), human monocytes (THP-1), and sheep erythrocytes. ThS in vitro cell treatment reduced the percentage of infected macrophages and the number of amastigotes per macrophage by increasing ROS production and reducing TNF-α levels. These results highlight the potential of ThS among thiohydantoins, mainly related to the arginine portion, as a leishmanicidal drug for future drug strategies for leishmaniasis treatment. Notably, in silico investigation of key targets from L. amazonensis, revealed that a ThS compound from the l-arginine amino acid strongly interacts with arginase (ARG) and TNF-α converting enzyme (TACE), suggesting its potential as a Leishmania inhibitor.

A squalene oil emulsified MPL-A and anti-CD200/CD300a antibodies adjuvanted whole-killed Leishmania vaccine provides durable immunity against L. donovani parasites

Antigenic inefficacy to induce robust immune responses and durable memory are major causes of constantly failing prophylactic approaches in leishmaniasis. Here, we determine the potential of a standardized whole-killed Leishmania vaccine (Leishvacc) adjuvanted with anti-CD200 and anti-CD300a antibodies, either alone or with monophosphoryl lipid A (MPL-SE) emulsified in squalene oil, in restoring the compromised antigen presenting abilities of dendritic cells (DCs), effector properties of CD4+T cells and providing protection against Leishmania donovani parasites. In animals vaccinated with antibodies adjuvanted vaccines, either alone or with MPL-SE, the antigen presenting abilities of CD11c+ DCs against Leishmania antigens, measured in terms of CD80, CD86, MHC-I, and MHC-II surface receptors and intracellular IL-12 were found enhanced than non-adjuvanted vaccine. We observed more proliferative and pro-inflammatory cytokines i.e. IL-2, IFN-γ, IL-23, and IL-12 producing CD4+T cells in antibodies/MPL-SE adjuvanted vaccinated animals further suggesting that this approach helps antigen activated CD4+T cells to acquire pro-inflammatory cytokines producing abilities. In antibodies, either alone or with MPL-SE, vaccinated animals, the number of CD4+ central memory T cells and their longevity were found significantly enhanced that further evidenced the impact of this vaccination approach in inducing long term protective immunity. The animals, receiving antibodies adjuvanted vaccines, either alone or with MPL-SE, exhibited excellent protection against virulent parasites by restricting their growth, which correlated with the significantly reduced parasitemia, splenomegaly, and hepatomegaly, along with fewer numbers of liver granulomas. Our findings provide an insight to a new immunoprophylactic approach against visceral leishmaniasis, which not only satisfies the safety criteria, but also provides a robust immunogenic response with remarkable potential for parasites control. However, further in-depth investigations are needed to ascertain its ability in inducing long-lasting immunity.

Targeting and activation of macrophages in leishmaniasis. A focus on iron oxide nanoparticles

Macrophages play a pivotal role as host cells for Leishmania parasites, displaying a notable functional adaptability ranging from the proinflammatory, leishmanicidal M1 phenotype to the anti-inflammatory, parasite-permissive M2 phenotype. While macrophages can potentially eradicate amastigotes through appropriate activation, Leishmania employs diverse strategies to thwart this activation and redirect macrophages toward an M2 phenotype, facilitating its survival and replication. Additionally, a competition for iron between the two entities exits, as iron is vital for both and is also implicated in macrophage defensive oxidative mechanisms and modulation of their phenotype. This review explores the intricate interplay between macrophages, Leishmania, and iron. We focus the attention on the potential of iron oxide nanoparticles (IONPs) as a sort of immunotherapy to treat some leishmaniasis forms by reprogramming Leishmania-permissive M2 macrophages into antimicrobial M1 macrophages. Through the specific targeting of iron in macrophages, the use of IONPs emerges as a promising strategy to finely tune the parasite-host interaction, endowing macrophages with an augmented antimicrobial arsenal capable of efficiently eliminating these intrusive microbes.

Assessing proteases and enzymes of the trypanothione system in subpopulations of Leishmania (Viannia) braziliensis Thor strain during macrophage infection

BACKGROUND

Leishmania (Viannia) braziliensis Thor strain exhibits a heterogeneous composition comprised of subpopulations with varying levels of infectivity. Clonal subpopulations were previously obtained from the strain Thor by sorting single-parasites and proceeding cultivation. The subpopulations used in this study are named Thor03, Thor 10 and Thor22.

OBJECTIVES

Phenotypic characteristics of the parasite, specially focusing on virulence factors and resistance to the antimicrobial mechanisms of macrophages, were investigate in these subpopulations.

METHODS

Cellular and molecular biology, as well as biochemistry approaches were applied to obtain the data analysed in this study.

FINDINGS

Relative quantification of gene expression was measured for calpain, cysteine protease B (CPB), and subtilisin proteases but no significant differences in these genes' expression among subpopulations was observed. However, subtilisin and CPB proteins were assessed as more abundant in Thor03 by fluorescence-labelled flow cytometry technique. Western Blotting assays, as semi-quantitative analysis in gel, showed higher concentrations of subtilisin (110 to 50 kDa) and CPB (40 to 18 kDa) in extract of intracellular amastigotes from subpopulations Thor03 and Thor10 and calpain (60 to 25 kDa) showed no significant differences among subpopulations. Complementary, higher trypanothione reductase activity was observed in Thor10 intracellular amastigotes and assays of susceptibility to hydrogen peroxide-inducing agents and nitric oxide donors conducted with promastigotes revealed greater resistance to in vitro oxidative stress induction for Thor10, followed by Thor03.

MAIN CONCLUSIONS

The data obtained for the virulence factors explored here suggest how multiple coexisting phenotypic-distinct subpopulations may contribute in adaptability of a single L. (V.) braziliensis strain during infection in the host cells.

Unmasking the Mechanism behind Miltefosine: Revealing the Disruption of Intracellular Ca2+ Homeostasis as a Rational Therapeutic Target in Leishmaniasis and Chagas Disease

Originally developed as a chemotherapeutic agent, miltefosine (hexadecylphosphocholine) is an inhibitor of phosphatidylcholine synthesis with proven antiparasitic effects. It is the only oral drug approved for the treatment of Leishmaniasis and American Trypanosomiasis (Chagas disease). Although its precise mechanisms are not yet fully understood, miltefosine exhibits broad-spectrum anti-parasitic effects primarily by disrupting the intracellular Ca2+ homeostasis of the parasites while sparing the human hosts. In addition to its inhibitory effects on phosphatidylcholine synthesis and cytochrome c oxidase, miltefosine has been found to affect the unique giant mitochondria and the acidocalcisomes of parasites. Both of these crucial organelles are involved in Ca2+ regulation. Furthermore, miltefosine has the ability to activate a specific parasite Ca2+ channel that responds to sphingosine, which is different to its L-type VGCC human ortholog. Here, we aimed to provide an overview of recent advancements of the anti-parasitic mechanisms of miltefosine. We also explored its multiple molecular targets and investigated how its pleiotropic effects translate into a rational therapeutic approach for patients afflicted by Leishmaniasis and American Trypanosomiasis. Notably, miltefosine's therapeutic effect extends beyond its impact on the parasite to also positively affect the host's immune system. These findings enhance our understanding on its multi-targeted mechanism of action. Overall, this review sheds light on the intricate molecular actions of miltefosine, highlighting its potential as a promising therapeutic option against these debilitating parasitic diseases.

Genetic variation of FcγRIIa induces higher uptake of Leishmania infantum and modulates cytokine production by adherent mononuclear cells in vitro

Introduction

Single nucleotide variations (SNVs) are specific genetic variations that commonly occur in a population and often do not manifest phenotypically. However, depending on their location and the type of nucleotide exchanged, an SNV can alter or inhibit the function of the gene in which it occurs. Immunoglobulin G (IgG) receptor genes have exhibited several polymorphisms, including rs1801274, which is found in the FcgRIIa gene. The replacement of A with T results in a Histidine (H) to Arginine (R) substitution, altering the affinity of the IgG receptor for IgG subtypes and C-reactive protein (CRP). In this study, we analyzed rs1801274 and its functional implications concerning L. Infantum uptake and cytokine production.

Methods

We genotyped 201 individuals from an endemic area for visceral leishmaniasis to assess the presence of rs1801274 using Taqman probes for a candidate gene study. Additionally, we included seventy individuals from a non-endemic area for a functional study. Subsequently, we isolated and cultivated one-week adherent mononuclear cells (AMCs) derived from the peripheral blood of participants residing in the non-endemic region in the presence of L. infantum promastigotes, with and without antigen-specific IgG and/or CRP. We analyzed the rate of phagocytosis and the production of nitric oxide (NO), tumor necrosis factor (TNF)-a, interleukin (IL)-10, IL-12 p70, IL-1b, IL- 6, and IL-8 in the culture supernatants.

Results and discussion

In participants from the endemic region, the A/G (H/R isoform) heterozygous genotype was significantly associated with susceptibility to the disease. Furthermore, SNVs induced a change in the phagocytosis rate in an opsonin-dependent manner. Opsonization with IgG increased the production of IL-10, TNF-a, and IL-6 in AMCs with the H/R isoform, followed by a decrease in NO production. The results presented here suggest that the rs1801274 polymorphism is linked to a higher susceptibility to visceral leishmaniasis.

Short communication: The miR-155a-5p is correlated with increased ROS and impaired apoptosis in macrophages infected by Leishmania braziliensis

Cutaneous leishmaniasis (CL) caused by Leishmania braziliensis, is a disease characterized by well-limited ulcerated lesions with raised borders in exposed parts of the body. miRNAs are recognized for their role in the complex and plastic interaction between host and pathogens, either as part of the host's strategy to neutralize infection or as a molecular mechanism employed by the pathogen to modulate host inflammatory pathways to remain undetected. The mir155 targets a broad range of inflammatory mediators, following toll-like receptors (TLRs) signaling. In this work, we evaluated the effects of the expression of miR155a-5p in human macrophages infected with L. braziliensis. Our results show that miR155a-5p is inversely correlated with early apoptosis and conversely, seems to influence an increment in the oxidative burst in these cells. Altogether, we spotted a functional role of the miR155a-5p in CL pathogenesis, raising the hypothesis that an increased miR-155 expression by TLR ligands influences cellular mechanisms settled to promote both killing and control of parasite density after infection.

Isoenzyme characterization of Leishmania infantum toward checking the antioxidant activity of superoxide dismutase and glutathione peroxidase

BACKGROUND

Leishmania infantum is the major causative agent of visceral leishmaniasis in Mediterranean regions. Isoenzyme electrophoresis (IE), as a biochemical technique, is applied in the characterization of Leishmania species. The current study attempted to investigate the isoenzyme patterns of logarithmic and stationary promastigotes and axenic amastigotes (amastigote-like) of L. infantum using IE. The antioxidant activity of superoxide dismutase (SOD) and glutathione peroxidase (GPX) was also checked in the aforementioned forms.

METHOD

After L. infantum cultivation and obtaining logarithmic and stationary promastigotes, axenic amastigotes were achieved by incubation of stationary promastigotes at 37 °C for 48 h. The lysate samples were prepared and examined for six enzymatic systems including glucose-6-phosphate dehydrogenase (G6PD), nucleoside hydrolase 1 (NH1), malate dehydrogenase (MDH), glucose-phosphate isomerase (GPI), malic enzyme (ME), and phosphoglucomutase (PGM). Additionally, the antioxidant activity of SOD and GPX was measured.

RESULTS

GPI, MDH, NH1, and G6PD enzymatic systems represented different patterns in logarithmic and stationary promastigotes and axenic amastigotes of L. infantum. PGM and ME showed similar patterns in the aforementioned forms of parasite. The highest level of SOD activity was determined in the axenic amastigote form and GPX activity was not detected in different forms of L. infantum.

CONCLUSION

The characterization of leishmanial-isoenzyme patterns and the measurement of antioxidant activity of crucial antioxidant enzymes, including SOD and GPX, might reveal more information in the biology, pathogenicity, and metabolic pathways of Leishmania parasites and consequently drive to designing novel therapeutic strategies in leishmaniasis treatment.

Part I: Epidemiology, pathophysiology, and clinical considerations of primary and secondary Raynaud's phenomenon

Raynaud's phenomenon (RP) is a relatively common disease with both primary and secondary forms. It is well understood as a vasospastic condition affecting the acral and digital arteries, resulting in characteristic, well-demarcated color changes typically in the hands and feet in response to cold or stress. Secondary RP (SRP) has been described in association with a variety of rheumatologic and nonrheumatologic diseases, environmental exposures, and/or medications. While both primary RP and SRP may impact the quality of life, SRP may lead to permanent and potentially devastating tissue destruction when undiagnosed and untreated. It is therefore crucial for dermatologists to distinguish between primary and secondary disease forms early in clinical evaluation, investigate potential underlying causes, and risk stratify SRP patients for the development of associated autoimmune connective tissue disease. The epidemiology, pathogenesis, and clinical presentation and diagnosis of both forms of RP are described in detail in this review article.

Leishmanicidal and immunomodulatory activity of Terminalia catappa in Leishmania amazonensisin vitro infection

Leishmaniases are infectious-parasitic diseases that impact public health around the world. Antileishmanial drugs presented toxicity and increase in parasitic resistance. Studies with natural products show an alternative to this effect, and several metabolites have demonstrated potential in the treatment of various diseases. Terminalia catappa is a plant species with promising pharmaceutical properties. The objective of this work was to evaluate the therapeutic potential of extracts and fractions of T. catappa on Leishmania amazonensis and investigate the immunomodulatory mechanisms associated with its action. In anti-Leishmania assays, the ethyl acetate fraction exhibited activity against promastigotes (IC50 86.07 ± 1.09 μg/mL) and low cytotoxicity (CC50 517.70 ± 1.68 μg/mL). The ethyl acetate fraction also inhibited the intracellular parasite (IC50 25.74 ± 1.08 μg/mL) with a selectivity index of 20.11. Treatment with T. catappa ethyl acetate fraction did not alter nitrite production by peritoneal macrophages stimulated with L. amazonensis, although there was a decrease in unstimulated macrophages treated at 50 μg/mL (p = 0.0048). The T. catappa ethyl acetate fraction at 100 μg/mL increased TNF-α levels (p = 0.0238) and downregulated HO-1 (p = 0.0030) and ferritin (p = 0.0002) gene expression in L. amazonensis-stimulated macrophages. Additionally, the total flavonoid and ellagic acid content for ethyl acetate fraction was 13.41 ± 1.86 mg QE/g and 79.25 mg/g, respectively. In conclusion, the T. catappa ethyl acetate fraction showed leishmanicidal activity against different forms of L. amazonensis and displayed immunomodulatory mechanisms, including TNF-α production and expression of pro and antioxidant genes.

Immunogenicity and protective efficacy of tuzin protein as a vaccine candidate in Leishmania donovani-infected BALB/c mice

Visceral leishmaniasis (VL) is referred to as the most severe and fatal type of leishmaniasis basically caused by Leishmania donovani and L. infantum. The most effective method for preventing the spread of the disease is vaccination. Till today, there is no promising licensed vaccination for human VL. Hence, investigation for vaccines is necessary to enrich the therapeutic repertoire against leishmaniasis. Tuzin is a rare trans-membrane protein that has been reported in Trypanosoma cruzi with unknown function. However, tuzin is not characterized in Leishmania parasites. In this study, we for the first time demonstrated that tuzin protein was expressed in both stages (promastigote and amastigote) of L. donovani parasites. In-silico studies revealed that tuzin has potent antigenic properties. Therefore, we analyzed the immunogenicity of tuzin protein and immune response in BALB/c mice challenged with the L. donovani parasite. We observed that tuzin-vaccinated mice have significantly reduced parasite burden in the spleen and liver compared with the control. The number of granulomas in the liver was also significantly decreased compared with the control groups. We further measured the IgG2a antibody level, a marker of Th1 immune response in VL, which was significantly higher in the serum of immunized mice when compared with the control. Splenocytes stimulated with soluble Leishmania antigen (SLA) displayed a significant increase in NO and ROS levels compared with the control groups. Tuzin-immunized and parasite-challenged mice exhibit a notable rise in the IFN-γ/IL-10 ratio by significantly suppressing IL-10 expression level, an immunosuppressive cytokine that inhibits leishmanicidal immune function and encourages disease progression. In conclusion, tuzin immunizations substantially increase the protective immune response in L. donovani-challenged mice groups compared with control.

Inhibition and structural insights of leishmanial glutamyl-tRNA synthetase for designing potent therapeutics

Aminoacyl-tRNA synthetases (aaRSs), essential components of the protein synthesizing machinery, have been often chosen for devising therapeutics against parasitic diseases. Due to their relevance in drug development, the current study was designed to explore functional and structural aspects of Leishmania donovani glutamyl-tRNA synthetase (LdGluRS). Hence, LdGluRS was cloned into an expression vector and purified to homogeneity using chromatographic techniques. Purified protein showed maximum enzymatic activity at physiological pH, with more binding capacity towards its cofactor (Adenosine triphosphate, 0.06 ± 0.01 mM) than the cognate substrate (L-glutamate, 9.5 ± 0.5 mM). Remarkably, salicylate inhibited LdGluRS competitively with respect to L-glutamate and exhibited druglikeness with negligible effect on human macrophages. The protein possessed more α-helices (43 %) than β-sheets (12 %), whereas reductions in thermal stability and cofactor-binding affinity, along with variation in mode of inhibition after mutation signified the role of histidine (H60) as a catalytic residue. LdGluRS could also generate a pro-inflammatory milieu in human macrophages by upregulating cytokines. The docking study demonstrated the placement of salicylate into LdGluRS substrate-binding site, and the complex was found to be stable during molecular dynamics (MD) simulation. Altogether, our study highlights the understanding of molecular inhibition and structural features of glutamyl-tRNA synthetase from kinetoplastid parasites.

Antileishmanial Activity, Toxicity and Mechanism of Action of Complexes of Sodium Usnate with Lanthanide Ions: Eu(III), Sm(III), Gd(III), Nd(III), La(III) and Tb(III)

Leishmaniases are neglected diseases with limited therapeutic options. Diffuse cutaneous leishmaniasis can occur in Brazil due to Leishmania amazonensis. This study details the antileishmanial activity and cytotoxicity of complexes of sodium usnate (SAU) with lanthanide ions ([LnL3 (H2O)x] (Ln = La(III), Nd(III), Gd(III), Tb(III), Eu(III) and Sm(III); L = SAU). All lanthanide complexes were highly active and more potent than SAU against L. amazonensis promastigotes and intracellular amastigotes (Pro: IC50 < 1.50 μM; Ama: IC50 < 7.52 μM). EuL3·3H2O and NdL3·3H2O were the most selective and effective on intracellular amastigotes, with a selectivity index of approximately 7.0. In silico predictions showed no evidence of mutagenicity, tumorigenicity or irritation for all complexes. Treatment with EuL3·3H2O triggered NO release even at the lowest concentration, indicating NO production as a mechanism of action against the parasite. Incubating promastigotes with the lanthanide complexes, particularly with SmL3·4H2O and GdL3·3H2O, led to a change in the mitochondrial membrane potential, indicating the ability of these complexes to target this essential organelle. The same complexes caused cell death through cell membrane disruption, but their relationship with early or late apoptotic processes remains unclear. Thus, the inclusion of lanthanide ions in SAU improves selectivity with a promising mechanism of action targeting the mitochondria.

Oxidative Stress in Parasitic Diseases-Reactive Oxygen Species as Mediators of Interactions between the Host and the Parasites

Oxidative stress plays a significant role in the development and course of parasitic infections, both in the attacked host organism and the parasite organism struggling to survive. The host uses large amounts of reactive oxygen species (ROS), mainly superoxide anion (O2•-) and hydrogen peroxide (H2O2), to fight the developing parasitic disease. On the other hand, the parasite develops the most effective defense mechanisms and resistance to the effects of ROS and strives to survive in the host organism it has colonized, using the resources and living environment available for its development and causing the host's weakening. The paper reviews the literature on the role of oxidative stress in parasitic diseases, which are the most critical epidemiological problem worldwide. The most common parasitosis in the world is malaria, with 300-500 million new cases and about 1 million deaths reported annually. In Europe and Poland, the essential problem is intestinal parasites. Due to a parasitic infection, the concentration of antioxidants in the host decreases, and the concentration of products of cellular components oxidation increases. In response to the increased number of reactive oxygen species attacking it, the parasites have developed effective defense mechanisms, including primarily the action of antioxidant enzymes, especially superoxide dismutase and nicotinamide adenine dinucleotide phosphate hydrogen (NADPH)-dependent complexes glutathione and thioredoxin.

The immune response in canine and human leishmaniasis and how this influences the diagnosis- a review and assessment of recent research

Leishmaniasis is a widespread but still underdiagnosed parasitic disease that affects both humans and animals. There are at least 20 pathogenic species of Leishmania, most of them being zoonotic. The diagnosis of leishmaniasis remains a major challenge, with an important role being played by the species of parasites involved, the genetic background, the immunocompetence of the host. This paper brings to the fore the sensitivity of the balance in canine and human leishmaniasis and addresses the importance of the host's immune response in establishing a correct diagnosis, especially in certain cases of asymptomatic leishmaniasis, or in the situation the host is immunosuppressed or acquired leishmaniasis through vertical transmission. The methods considered as a reference in the diagnosis of leishmaniasis no longer present certainty, the diagnosis being influenced mostly by the immune response of the host, which differs according to the presence of other associated diseases or even according to the breed in dogs. Consequently, the diagnosis and surveillance of leishmaniasis cases remains an open topic, requiring new diagnostic methods adapted to the immunological state of the host.

Cellular mediators in human leishmaniasis: Critical determinants in parasite killing or disease progression

Data on cellular immunity mediators in the early phase of human leishmaniasis are still limited and controversial. In order to mimic the changes of humoral mediators during the early phase of human natural infection, some Th1, Th2, Treg, and Breg cytokines, MCP-1, and the nitric oxide (NO) from human PBMC, stimulated by Leishmania infantum, Leishmania major, Leishmania donovani and Leishmania tropica infective metacyclic promastigotes, were determined. After 4 h of L. major, L. donovani, and L. tropica challenge, TNFα, IL-1β, IL-6 levels were significantly higher than negative control cultures with saline (SF) instead of Leishmania promastigotes, unlike L. infantum-stimulated TNFα and L. major-stimulated IL-1β. We obtained higher levels of IL-4 and IL-10 cytokines after stimulation of human PBMCs by L. infantum and L. donovani, compared to those observed after the challenge of PBMCs by L. major and L. tropica. Regarding IL-35, such cytokine levels were significantly increased following infection with L. infantum and L. donovani, in contrast to L. major and L. tropica. Up to our knowledge, we are the first to study the effect of four different species of Leishmania on IL-35 levels in human cells. Our study highlights how several Leishmania species can up-regulate different groups of cytokines (Th1, Th2, Treg and Breg) and modulate NO release in a different way. This original aspect can be explained by different Leishmania cell products, such as LPG, obtained from different strains/species of live parasites. Our findings would contribute to the development of new therapeutics or vaccination strategies.

Prostaglandin E2 contributes to L. braziliensis survival and therapeutic failure in cutaneous leishmaniasis

Patients with cutaneous leishmaniasis (CL) present an exacerbated inflammatory response associated with tissue damage and ulcer development. In recent years, higher rates of failure to pentavalent antimoniate therapy have been observed, yet the underlying reason remains poorly understood. We hypothesize that the eicosanoid PGE2 favours the establishment of infection by L. braziliensis, which contributes to therapeutic failure. The aim of the present study was to investigate the influence of PGE2 on the survival of L. braziliensis in macrophages and rates of therapeutic failure in CL patients. PGE2, an eicosanoid derived from the metabolism of arachidonic acid by the COX-2 enzyme, plays several roles in immune response. We found that increased PGE2 decreases the microbicidal function of macrophages and is associated with disease severity and therapeutic failure. Additionally, the neutralization of COX-2 by NS398, a selective NSAID, increases the ability of macrophages to kill L. braziliensis and protects against the pathological inflammatory response. Our data suggest that NS398 may serve as an adjunct treatment for CL patients.

Curcumin as a Stabilizer of Macrophage Polarization during Plasmodium Infection

Malaria is a parasitic infection responsible for high morbidity and mortality rates worldwide. During the disease, phagocytosis of infected red blood cells by the macrophages induces the production of reactive oxygen (ROS) and nitrogen species (RNS), culminating in parasite death. Curcumin (CUR) is a bioactive compound that has been demonstrated to reduce the production of pro-inflammatory cytokines and chemokines produced by macrophages but to reduce parasitemia in infected mice. Hence, the main purpose of this study is to investigate whether curcumin may interfere with macrophage function and polarization after Plasmodium berghei infection in vitro. In our findings, non-polarized macrophage (M0), classically activated (M1), and alternatively activated (M2) phenotypes showed significantly increased phagocytosis of infected red blood cells (iRBCs) when compared to phagocytosis of uninfected red blood cells (RBCs) 3 h after infection. After 24 h, M1 macrophages exposed to RBCs + CUR showed greater elimination capacity when compared to macrophages exposed to iRBCs + CUR, suggesting the interference of curcumin with the microbicidal activity. Additionally, curcumin increased the phagocytic activity of macrophages when used in non-inflammatory conditions (M0) and reduced the inducible nitric oxide synthase (iNOS) and arginase activities in all macrophage phenotypes infected (M0, M1, and M2), suggesting interference in arginine availability by curcumin and balance promotion in macrophage polarization in neutral phenotype (M0). These results support the view of curcumin treatment in malaria as an adjuvant, promoting a balance between pro- and anti-inflammatory responses for a better clinical outcome.

Optimization of the 2-arylquinazoline-4(3H)one scaffold for a selective and potent antitrypanosomal agent: modulation of the mechanism of action through chemical functionalization

We sought to identify a potent and selective antitrypanosomal agent through modulation of the mechanism of action of a 2-arylquinazoline scaffold as an antitrypanosomal agent via chemical functionalization at the 4-position. We wished to use the: (i) susceptibility of trypanosomatids towards nitric oxide (NO) and reactive oxygen species (ROS); (ii) capacity of the 4-substituted quinazoline system to act as an antifolate agent. Three quinazolin-based moieties that differed from each other by having at the 4-position key pharmacophores targeting the induction of NO and ROS production were evaluated in vitro against Leishmania infantum and Trypanosoma cruzi parasites and their modes of action were explored. Replacement of an oxygen moiety at the 4-position of the antifolate 2-arylquinazolin-4(3H)one by hydrazinyl and 5-nitrofuryl-hydrazinyl pharmacophores enhanced antitrypanosomatid activity significantly due to promotion of an additional mechanism beyond the antifolate response such as NO or ROS production, respectively. Among the three types of chemical functionalization, the 5-nitrofuryl-hydrazinyl moiety generated the most potent compounds. Compound 3b was a potential candidate thanks to its sub-micromolar response against the promastigotes/amastigotes of L. infantum and epimastigote of T. cruzi, moderate toxicity on macrophages (J774.1), good selectivity index (∼15.1-17.6) and, importantly, non-mutagenic effects. 2-Arylquinazoline could be an attractive platform to design new anti-trypanosomatid agents with the use of key pharmacophores.

Leishmania braziliensis exosomes activate human macrophages to produce proinflammatory mediators

Exosomes, organelles measuring 30-200nm, are secreted by various cell types. Leishmania exosomes consist of many proteins, including heat shock proteins, annexins, Glycoprotein 63, proteins exerting signaling activity and those containing mRNA and miRNA. Studies have demonstrated that Leishmania donovani exosomes downregulate IFN-γ and inhibit the expression of microbicidal molecules, such as TNF and nitric oxide, thus creating a microenvironment favoring parasite proliferation. Despite lacking immunological memory, data in the literature suggest that, following initial stimulation, mononuclear phagocytes may become "trained" to respond more effectively to subsequent stimuli. Here we characterized the effects of macrophage sensitization using L. braziliensis exosomes prior to infection by the same pathogen. Human macrophages were stimulated with L. braziliensis exosomes and then infected with L. braziliensis. Higher levels of IL-1β and IL-6 were detected in cultures sensitized prior to infection compared to unstimulated infected cells. Moreover, stimulation with L. braziliensis exosomes induced macrophage production of IL-1β, IL-6, IL-10 and TNF. Inhibition of exosome secretion by L. braziliensis prior to macrophage infection reduced cytokine production and produced lower infection rates than untreated infected cells. Exosome stimulation also induced the consumption/regulation of NLRP3 inflammasome components in macrophages, while the blockade of NLRP3 resulted in lower levels of IL-6 and IL-1β. Our results suggest that L. braziliensis exosomes stimulate macrophages, leading to an exacerbated inflammatory state that may be NLRP3-dependent.

Next generation of selenocyanate and diselenides with upgraded leishmanicidal activity

Nowadays, leishmaniasis is still treated with outdated drugs that present several obstacles related to their high toxicity, long duration, parenteral administration, high costs and drug resistance. Therefore, there is an urgent demand for safer and more effective novel drugs. Previous studies indicated that selenium compounds are promising derivatives for innovative therapy in leishmaniasis treatment. With this background, a new library of 20 selenocyanate and diselenide derivatives were designed based on structural features present in the leishmanicidal drug miltefosine. Compounds were initially screened against promastigotes of L. major and L. infantum and their cytotoxicity was evaluated in THP-1 cells. Compounds B8 and B9 were the most potent and less cytotoxic and were further screened for the intracellular back transformation assay. The results obtained revealed that B8 and B9 showed EC50 values of 7.7 µM and 5.7 µM, respectively, in L. major amastigotes, while they presented values of 6.0 µM and 7.4 µM, respectively, against L. infantum amastigotes. Furthermore, they exerted high selectivity (60 < SI > 70) towards bone marrow-derived macrophages. Finally, these compounds exhibited higher TryR inhibitory activity than mepacrine (IC50 7.6 and 9.2 µM, respectively), and induced nitric oxide (NO) and reactive oxygen species (ROS) production in macrophages. These results suggest that the compounds B8 and B9 could not only exert a direct leishmanicidal activity against the parasite but also present an indirect action by activating the microbicidal arsenal of the macrophage. Overall, these new generation of diselenides could constitute promising leishmanicidal drug candidates for further studies.

A comprehensive review of natural products with anti-hypoxic activity

Natural products exhibit substantial impacts in the field of anti-hypoxic traetment. Hypoxia can cause altitude sickness and other negative effect on the body. Headache, coma, exhaustion, vomiting and, in severe cases, death are some of the clinical signs. Currently, hypoxia is no longer just a concern in plateau regions; it is also one of the issues that can not be ignored by urban residents. This review covered polysaccharides, alkaloids, saponins, flavonoids, peptides and traditional Chinese compound prescriptions as natural products to protect against hypoxia. The active ingredients, effectiveness and mechanisms were discussed. The related anti-hypoxic mechanisms involve increasing the hemoglobin (HB) content, glycogen content and adenosine triphosphate (ATP) content, removing excessive reactive oxygen species (ROS), reducing lipid peroxidation, regulating the levels of related enzymes in cells, protecting the structural and functional integrity of the mitochondria and regulating the expression of apoptosis-related genes. These comprehensive summaries are beneficial to anti-hypoxic research and provide useful information for the development of anti-hypoxic products.

Co-expression analysis of lncRNA and mRNA suggests a role for ncRNA-mediated regulation of host-parasite interactions in primary skin lesions of patients with American tegumentary leishmaniasis

Leishmaniasis, caused by different Leishmania species, manifests as cutaneous or visceral forms. In the American continent, the cutaneous form is called American tegumentary leishmaniasis (ATL) and is primarily caused by Leishmania (Viannia) braziliensis. Mucosal leishmaniasis (ML), the most severe form of ATL, arises in approximately 20% of patients from a primary cutaneous lesion. Evidence indicates changes in overall expression patterns of mRNAs and lncRNAs of the host in response to Leishmania infection, with the parasite capable of modulating host immune response, which may contribute to disease progression. We evaluated whether the co-expression of lncRNAs and their putative target mRNAs in primary cutaneous lesions of patients with ATL could be associated with the development of ML. Previously available public RNA-Seq data from primary skin lesions of patients infected with L. braziliensis was employed. We identified 579 mRNAs and 46 lncRNAs differentially expressed in the primary lesion that subsequently progressed to mucosal disease. Co-expression analysis revealed 1,324 significantly correlated lncRNA-mRNA pairs. Among these, we highlight the positive correlation and trans-action between lncRNA SNHG29 and mRNA S100A8, both upregulated in the ML group. S100A8 and its heterodimeric partner S100A9 form a pro-inflammatory complex expressed by immune cells and seems to participate in host innate immune response processes of infection. These findings expand the knowledge of the Leishmania-host interaction and indicate that the expression of lncRNAs in the primary cutaneous lesion could regulate mRNAs and play roles in disease progression.

Enriched PUFA environment of Leishmania infantum promastigotes promotes the accumulation of lipid mediators and favors parasite infectivity towards J774 murine macrophages

Leishmania parasites are the causative agents of visceral or cutaneous leishmaniasis in humans and of canine leishmaniosis. The macrophage is the predilected host cell of Leishmania in which the promastigote stage is transformed into amastigote. We previously showed changes in the fatty acid composition (FA) of lipids in two strains of Leishmania donovani upon differentiation of promastigote to amastigote, including increased proportions of arachidonic acid (AA) and to a less extent of docosahexaenoic acid (DHA). Here, we carried out supplementation with AA or DHA on two Leishmania infantum strains, a visceral (MON-1) and a cutaneous (MON-24), to evaluate the role of these FA in parasite/macrophage interactions. The proportions of AA or DHA in total lipids were significantly increased in promastigotes cultured in AA- or DHA-supplemented media compared to controls. The content of FA-derived oxygenated metabolites was enhanced in supplemented strains, generating especially epoxyeicosatrienoic acids (11,12- and 14,15-EET) and hydroxyeicosatetraenoic acids (5- and 8- HETE) from AA, and hydroxydocosahexaenoic acids (14- and 17-HDoHE) from DHA. For both MON-1 and MON-24, AA-supplemented promastigotes showed higher infectivity towards J774 macrophages as evidenced by higher intracellular amastigote numbers. Higher infectivity was observed after DHA supplementation for MON-24 but not MON-1 strain. ROS production by macrophages increased upon parasite infection, but only minor change was observed between control and supplemented parasites. We propose that under high AA or DHA environment that is associated with AA or DHA enrichment of promastigote lipids, FA derivatives can accumulate in the parasite, thereby modulating parasite infectivity towards host macrophages.

Fatty Acid Composition and Metabolism in Leishmania Parasite Species: Potential Biomarkers or Drug Targets for Leishmaniasis?

Fatty acids have received growing interest in Leishmania biology with the characterization of the enzymes allowing the complete fatty acid synthesis of this trypanosomatid parasite. This review presents a comparative analysis of the fatty acid profiles of the major classes of lipids and phospholipids in different species of Leishmania with cutaneous or visceral tropism. Specificities relating to the parasite forms, resistance to antileishmanial drugs, and host/parasite interactions are described as well as comparisons with other trypanosomatids. Emphasis is placed on polyunsaturated fatty acids and their metabolic and functional specificities, in particular, their conversion into oxygenated metabolites that are inflammatory mediators able to modulate metacyclogenesis and parasite infectivity. The impact of lipid status on the development of leishmaniasis and the potential of fatty acids as therapeutic targets or candidates for nutritional interventions are discussed.

Recent Advances in the Development of Adenovirus-Vectored Vaccines for Parasitic Infections

Vaccines against parasites have lagged centuries behind those against viral and bacterial infections, despite the devastating morbidity and widespread effects of parasitic diseases across the globe. One of the greatest hurdles to parasite vaccine development has been the lack of vaccine strategies able to elicit the complex and multifaceted immune responses needed to abrogate parasitic persistence. Viral vectors, especially adenovirus (AdV) vectors, have emerged as a potential solution for complex disease targets, including HIV, tuberculosis, and parasitic diseases, to name a few. AdVs are highly immunogenic and are uniquely able to drive CD8+ T cell responses, which are known to be correlates of immunity in infections with most protozoan and some helminthic parasites. This review presents recent developments in AdV-vectored vaccines targeting five major human parasitic diseases: malaria, Chagas disease, schistosomiasis, leishmaniasis, and toxoplasmosis. Many AdV-vectored vaccines have been developed for these diseases, utilizing a wide variety of vectors, antigens, and modes of delivery. AdV-vectored vaccines are a promising approach for the historically challenging target of human parasitic diseases.

Cytokine and phenotypic cell profiles in human cutaneous leishmaniasis caused by Leishmania donovani

BACKGROUND

The innate immune mediators are likely to influence the clinical phenotype of leishmaniasis by primary responses which limit or facilitate the spread of the parasite, as well as by modulating adaptive immunity. This study investigated the response of key innate immune cells in a focus which regularly reports localised cutaneous leishmaniasis (LCL) caused by Leishmania donovani, a species which typically causes visceral disease.

METHODS

Peripheral blood mononuclear cell (PBMC) derived macrophages and dendritic cells from patients with LCL and healthy controls from endemic and non-endemic areas, were stimulated with soluble Leishmania antigen (SLA). Inflammatory mediators produced by macrophages (TNF-α/TGF-β/IL-10, ELISA; NO, Griess method) and dendritic cells (IL-12p70, IL-10, flowcytometry) and macrophage expression of surface markers of polarization, activation and maturation (flowcytometry) were determined at 24h, 48h and 72h and compared. Study was conducted prospectively from 2015-2019.

RESULTS

Patient derived macrophages and dendritic cells produced higher levels of both pro and anti-inflammatory mediators compared to controls (p<0.05) with the best discrimination for active disease observed at 72h. Data demonstrated an early activation of macrophages and a subsequent pro-inflammatory bias, as indicated by temporal profiles of TNF-α/TGF-β and TNF-α/IL-10 ratios and higher proportions of classical (M1) macrophages. Higher TGF-β levels were observed in cells from patients with ulcerated or persistent lesions. Immune responses by cells derived from controls in endemic and non-endemic regions did not differ significantly from each other.

CONCLUSIONS

The overall immunophenotypic profile suggests that LCL observed in the country is the result of a balancing immune response between pro-inflammatory and regulatory mediators. The mediators which showed distinct profiles in patients warrant further investigation as potential candidates for immunotherapeutic approaches. A comparison with visceral leishmaniasis caused by the same species, would provide further evidence on the differential role of these mediators in the resulting clinical phenotype.

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.

Synthesis and Antitrypanosomal and Mechanistic Studies of a Series of 2-Arylquinazolin-4-hydrazines: A Hydrazine Moiety as a Selective, Safe, and Specific Pharmacophore to Design Antitrypanosomal Agents Targeting NO Release

Nitric oxide (NO) represents a valuable target to design antitrypanosomal agents by its high toxicity against trypanosomatids and minimal side effects on host macrophages. The progress of NO-donors as antitrypanosomal has been restricted by the high toxicity of their agents, which usually is based on NO-heterocycles and metallic NO-complexes. Herein, we carried out the design of a new class of NO-donors based on the susceptibility of the hydrazine moiety connected to an electron-deficient ring to be reduced to the amine moiety with release of NO. Then, a series of novel 2-arylquinazolin-4-hydrazine, with the potential ability to disrupt the parasite folate metabolism, were synthesized. Their in vitro evaluation against Leishmania and Trypanosoma cruzi parasites and mechanistic aspects were investigated. The compounds displayed significant leishmanicidal activity, identifying three potential candidates, that is, 3b, 3c, and 3f, for further assays by their good antiamastigote activities against Leishmania braziliensis, low toxicity, non-mutagenicity, and good ADME profile. Against T. cruzi parasites, derivatives 3b, 3c, and 3e displayed interesting levels of activities and selectivities. Mechanistic studies revealed that the 2-arylquinazolin-4-hydrazines act as either antifolate or NO-donor agents. NMR, fluorescence, and theoretical studies supported the fact that the quinazolin-hydrazine decomposed easily in an oxidative environment via cleavage of the N-N bond to release the corresponding heterocyclic-amine and NO. Generation of NO from axenic parasites was confirmed by the Griess test. All the evidence showed the potential of hydrazine connected to the electron-deficient ring to design effective and safe NO-donors against trypanosomatids.

Nitric oxide in parasitic infections: a friend or foe?

The complex interaction between the host and the parasite remains a puzzling question. Control of parasitic infections requires an efficient immune response that must be balanced against destructive pathological consequences. Nitric oxide is a nitrogenous free radical which has many molecular targets and serves diverse functions. Apart from being a signaling messenger, nitric oxide is critical for controlling numerous infections. There is still controversy surrounding the exact role of nitric oxide in the immune response against different parasitic species. It proved protective against intracellular protozoa, as well as extracellular helminths. At the same time, it plays a pivotal role in stimulating detrimental pathological changes in the infected hosts. Several reports have discussed the anti-parasitic and immunoregulatory functions of nitric oxide, which could directly influence the control of the infection. Nevertheless, there is scarce literature addressing the harmful cytotoxic impacts of this mediator. Thus, this review provides insights into the most updated concepts and controversies regarding the dual nature and opposing sides of nitric oxide during the course of different parasitic infections.

Host P2X7R-p38MAPK axis mediated intra-macrophage leishmanicidal activity of Spergulin-A

Current drugs are inefficient for the treatment of visceral leishmaniasis an immunosuppressive ailment caused by Leishmania donovani. Regrettably, there is no plant-origin antileishmanial drug present. P2X₇R is constitutively present on macrophage surfaces and can be a putative therapeutic target in intra-macrophage pathogens with function attributes towards inflammation, host cell apoptosis, altered redox, and phagolysosomal maturation by activating p₃₈MAPK. Here we demonstrated that the initial interaction of Spergulin-A (Sp A), a triterpenoid saponin with RAW 264.7 macrophages was mediated through P2X₇R involving the signaling cascade intermediates Ca⁺⁺, p₃₈MAPK, and NF-κβ. Phospho (P)-p38MAPK involvement is shown to have specific and firm importance in leishmanial killing with increased NF-κβp65. Phago-lysosomal maturation by Sp A also campaigns for another contribution of P2X₇R. In vivo evaluation of the anti-leishmanial activity of Sp A was monitored through expression analyses of P2X₇R, P-p38MAPK, and NF-κβp65 in murine spleen and bone-marrow macrophages and supported Sp A being a natural compound of leishmanicidal functions which acted through the P2X₇R-p38MAPK axis.

Following successful anti-leishmanial treatment, neutrophil counts, CD10 expression and phagocytic capacity remain reduced in visceral leishmaniasis patients co-infected with HIV

Visceral leishmaniasis (VL) patients co-infected with HIV (VL/HIV patients) experience frequent treatment failures, VL relapses, opportunistic infections, and higher mortality. Their immune system remains profoundly suppressed after clinical cure and they maintain higher parasite load. This is in contrast with patients with VL alone (VL patients). Since neutrophils play a critical role in the control of Leishmania replication and the regulation of immune responses, we tested the hypothesis that neutrophil activation status and effector functions are fully restored in VL, but not in VL/HIV patients. Our results show the neutrophil counts and all activation markers and effector functions tested in our study were reduced at the time of diagnosis in VL and VL/HIV patients as compared to controls. CD62L, CD63, arginase 1 expression levels and reactive oxygen species production were restored at the end of treatment in both groups. However, neutrophil counts, CD10 expression and phagocytosis remained significantly lower throughout follow-up in VL/HIV patients; suggesting that dysregulated neutrophils contribute to the impaired host defence against pathogens in VL/HIV patients.

Pioglitazone, a Peroxisome Proliferator-Activated Receptor-γ Agonist, Downregulates the Inflammatory Response in Cutaneous Leishmaniasis Patients Without Interfering in Leishmania braziliensis Killing by Monocytes

Patients with cutaneous leishmaniasis (CL) due to Leishmania braziliensis infection have an exacerbated inflammatory response associated with tissue damage and ulcer development. An increase in the rate of patients who fail therapy with pentavalent antimony has been documented. An adjuvant therapy with an anti-inflammatory drug with the potential of Leishmania killing would benefit CL patients. The aim of the present study was to investigate the contribution of peroxisome proliferator-activated receptor-γ (PPAR-γ) activation by pioglitazone in the regulation of the inflammatory response and L. braziliensis killing by monocytes. Pioglitazone is an oral drug used in the treatment of diabetes, and its main mechanism of action is through the activation of PPAR-γ, which is expressed in many cell types of the immune response. We found that activation of PPAR-γ by pioglitazone decreases the inflammatory response in CL patients without affecting L. braziliensis killing by monocytes. Our data suggest that pioglitazone may serve as an adjunctive treatment for CL caused by L. braziliensis.

Antiproliferative properties of Turmerone on Leishmania major: Modes of action confirmed by antioxidative and immunomodulatory roles

Treatment of leishmaniasis by conventional synthetic compounds has faced a serious challenge worldwide. This study was performed to evaluate the effect and modes of action of aromatic Turmerone on the Leishmania major intra-macrophage amastigotes, the causative agent of zoonotic cutaneous leishmaniasis in the Old World. In the findings, the mean numbers of L. major amastigotes in macrophages were significantly decreased in exposure to Turmerone plus meglumine antimoniate (Glucantime®; MA) than MA alone, especially at 50 µg/mL. In addition, Turmerone demonstrated no cytotoxicity as the selectivity index (SI) was 21.1; while it induced significant apoptosis in a dose-dependent manner on L. major promastigotes. In silico molecular docking analyses indicated an affinity of Turmerone to IL-12, with the MolDock score of - 96.8 kcal/mol; which may explain the increased levels of Th1 cytokines and decreased level of IL-10. The main mechanism of action is more likely associated with stimulating a powerful antioxidant and promoting the immunomodulatory roles in the killing of the target organism.

Protection and Pathology in Leishmania braziliensis Infection

Leishmania killing is mediated by IFN-γ-activated macrophages, but IFN-γ production and macrophage activation are insufficient to control L. braziliensis infection. In American tegumentary leishmaniasis (ATL), pathology results from an exaggerated inflammatory response. This report presents an overview of our contributions regarding ATL pathogenesis, highlighting future directions to improve the management of L. braziliensis infection. Monocytes and lymphocytes from individuals exposed to L. braziliensis but who do not develop CL, i.e., subclinical infection (SC), exhibit lower respiratory burst and IFN-γ production, yet more efficiently kill L. braziliensis. As vaccines aimed at inducing IL-12 and IFN-γ do not sufficiently prevent CL, the elucidation of how subjects with SC infection kill Leishmania may lead to new approaches to controlling ATL. While inflammation arising from the recruitment of inflammatory cells via chemokines induced by IFN-γ and TNF or IL-17 is observed and contributes to pathology, cytotoxic CD8⁺ T cells and NK cells play a key role in the pathogenesis of L. braziliensis infection. The increased transcription of genes related to inflammation and cytotoxicity, e.g., granzyme A, granzyme B, NLRP3 and IL-1β, has been documented in CL tissue samples. The release of products by killed cells leads to NLRP3 inflammasome activation, IL-1β production and additional damage to skin and mucosal tissues. The use of drugs that downmodulate the inflammatory response in combination with chemotherapy improves the ATL cure rate and decreases healing time.

Immune response to LinB13, a Lutzomyia intermedia salivary protein correlates with disease severity in tegumentary leishmaniasis

BACKGROUND

We have previously shown that seropositivity to rLinB-13, a salivary protein from Lutzomyia intermedia, predicted sand fly exposure and was associated with increased risk of developing cutaneous leishmaniasis (CL).

METHODS

Herein, we investigated the cellular immune response to saliva from Lu. intermedia, using rLinB-13 as a surrogate antigen in naturally exposed individuals presenting positive serology to LinB-13. We also investigated the response to rLinB-13 in leishmaniasis patients, displaying active ulcers and positive PCR for L. braziliensis.

RESULTS

Peripheral blood mononuclear cells (PBMCs) stimulated in vitro with rLinB-13 secreted elevated levels of IL-10, IL-4, IL-1β, IL-1α, IL-6 and chemokines (CCL3, CCL4, CCL5 and CXCL5). CL, and disseminated leishmaniasis (DL) patients displayed a significantly higher IgG response to rLinB-13, compared to healthy subjects and anti-rLinB-13 IgG was positively correlated with the number of lesions in DL patients. Positive serology to rLinB-13 was also associated with chemotherapy failure. PBMCs from DL patients stimulated with rLINB-13 secreted significantly higher levels IL-10 and IL-1β compared to CL individuals.

CONCLUSIONS

In this study, we observed an association between humoral and cellular immune response to the sand fly salivary protein rLinB-13 and disease severity in tegumentary leishmaniasis. This study brings evidence that immunity to rLinB-13 influences disease outcome in L. braziliensis infection and results indicate that positive serology to rLinB-13 IgG can be employed as marker of DL, an emerging and severe form of disease caused by L. braziliensis.

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.

In vitro antileishmanial activity of sustainable anacardic acid and cardol based silver nanoparticles on L. braziliensis

The search for effective and less toxic drugs for the treatment of Cutaneous Leishmaniasis (CL) is desirable due to the emergence of resistant parasites. The present study shows the preparation, characterization and in vitro antileishmanial activity of green-based silver nanoparticles (AgNPs) with Cashew Nutshell Liquid (CNSL, main constituents: anacardic acid (AA) and cardol (CD). The synthesis of silver nanoparticles was achieved by reduction with sodium borohydride in the presence of anacardic acid or cardol under microwave irradiation (400 W, 60 °C, 5 min) resulting in AgAA and AgCD. In vitro assay showed opposite effects for AgAA and AgCD. While AgAA is highly toxic to macrophages (CC₅₀ = 6.910 µg mL^-1) and almost non-toxic for L.braziliensis (IC₅₀ = 86.61 µg mL^-1), AgCD results very selective toward killing the parasite (CC₅₀ = 195.0 µg mL^-1, IC₅₀ = 11.54 µg mL^-1). AA's higher polarity and conical shape easily promote cell lysis by increasing cell permeability, while CD has a protective effect: for that reason, AA and AgAA were not further used for tests. CD (EC₅₀ = 2.906 µg mL^-1) had higher ability to kill intracellular amastigotes than AgCD (EC₅₀ = 16.00 µg mL^-1), however, less intact cells were seen on isolated CD tests. In addition, considering that NO is one of the critical molecular species for the intracellular control of Leishmania, we used Griess colorimetric test to analyze the effect of treatment with AgCD and CD. Overall, the in vitro antileishmanial tests indicate that AgCD should be further explored as a promising non-toxic treatment for CL.

Current and future strategies against cutaneous parasites

Cutaneous parasites are identified by their specific cutaneous symptoms which are elicited based on the parasite's interactions with the host. Standard anti-parasitic treatments primarily focus on the use of specific drugs to disrupt the regular function of the target parasite. In cases where secondary infections are induced by the parasite itself, antibiotics may also be used in tandem with the primary treatment to deal with the infection. Whilst drug-based treatments are highly effective, the development of resistance by bacteria and parasites, is increasingly prevalent in the modern day, thus requiring the development of non-drug based anti-parasitic strategies. Cutaneous parasites vary significantly in terms of the non-systemic methods that are required to deal with them. The main factors that need to be considered are the specifically elicited cutaneous symptoms and the relative cutaneous depth in which the parasites typically reside in. Due to the various differences in their migratory nature, certain cutaneous strategies are only viable for specific parasites, which then leads to the idea of developing an all-encompassing anti-parasitic strategy that works specifically against cutaneous parasites. The main benefit of this would be the overall time saved in regards to the period that is needed for accurate diagnosis of parasite, coupled with the prescription and application of the appropriate treatment based on the diagnosis. This review will assess the currently identified cutaneous parasites, detailing their life cycles which will allow for the identification of certain areas that could be exploited for the facilitation of cutaneous anti-parasitic treatment.

A Critical Overview of Interleukin 32 in Leishmaniases

Interleukin-32 (IL-32) has several immune regulatory properties, which have driven its investigation in the context of various diseases. IL-32 expression is reported to be induced in the lesions of patients with American tegumentary leishmaniasis (ATL) by the New World Leishmania spp. that are responsible for causing ATL and visceral leishmaniasis (VL). IL-32 expression may elevate the inflammatory process through the induction of pro-inflammatory cytokines and also via mechanisms directed to kill the parasites. The genetic variants of IL-32 might be associated with the resistance or susceptibility to ATL, while different isoforms of IL-32 could be associated with distinct T helper lymphocyte profiles. IL-32 also determines the transcriptional profile in the bone marrow progenitor cells to mediate the trained immunity induced by β-glucan and BCG, thereby contributing to the resistance against Leishmania. IL-32γ is essential for the vitamin D-dependent microbicidal pathway for parasite control. In this context, the present review report briefly discusses the data retrieved from the studies conducted on IL-32 in leishmaniasis in humans and mice to highlight the current challenges to understanding the role of IL-32 in leishmaniasis.

Identification and Characterization of the miRNAs and Cytokines in Response to Leishmania infantum Infection with Different Response to Treatment

PURPOSE

Due to the complexity of cytokine and microRNA function in progression and/or suppression of an infection, in this study, we examined miR-3473f, miR-2128, miR-6994-5p, miR-7093-3p, miR-5128, miR-574-5p, miR-7235, IL-2, IL-4, IL-5, IL-10 and IL-13 in patients with VL caused by Leishmania infantum in an in vivo study.

METHODS

Sampling was carried out from patient with leishmaniasis and with different responses to treatment during March 2016-January 2020. DNA was extracted and purified using QIAamp Kit. The L. infantum were cultured in DMEM medium and protein content was determined by the Micro BCA Protein Assay Kit. Cytokines were evaluated using a MILLIPLEX MAP Mouse Cytokine/Chemokine Panel I kit. The relative expression of miRNAs was measured in duplicate using automatic thermocycler ABI Prism 7500 sequence detection system (Applied Bio-systems) using the TaqMan MicroRNA Assay kit.

RESULTS

The real-time PCR assay revealed that miR-2128, miR-6994-5p, miR-7093-3p, miR-5128, miR-574-5p and miR-7235 were down-regulated and miR-3473 were up-regulated in patients with semi-resistance and resistance parasite strain (P < 0.05). In the current work, cytokine patterns in patients who were slow-to-clear or unable-to-clear L. infantum infection during drug treatment were seen to have decreased protective Th1 cytokines (IL-2, IL-12, TNF-α, and IFN-ɤ, P < 0.001) and increased Th2 cytokines (IL-5, IL-10, and IL-13, P < 0.001). No association was seen with IL-4 in patients with different treatment outcomes.

CONCLUSION

Overall, the results of a recent study have shown that cytokines and microRNAs can play a key role in response to treatment, and more comprehensive studies are needed to support this hypothesis.

Long-Term In Vitro Passaging Had a Negligible Effect on Extracellular Vesicles Released by Leishmania amazonensis and Induced Protective Immune Response in BALB/c Mice

Depending on Leishmania species and the presence/absence of virulence factors, Leishmania extracellular vesicles (EVs) can differently stimulate host immune cells. This work is aimed at characterizing and evaluating the protective role of EVs released by Leishmania amazonensis promastigotes under different maintenance conditions. Initially, using a control strain, we standardized 26°C as the best release temperature to obtain EVs with a potential protective role in the experimental leishmaniasis model. Then, long-term (LT-P) promastigotes of L. amazonensis were obtained after long-term in vitro culture (100 in vitro passages). In vivo-derived (IVD-P) promastigotes of L. amazonensis were selected after 3 consecutive experimental infections in BALB/c mice. Those strains developed similar lesion sizes except for IVD-P at 8 weeks post infection. No differences in EV production were detected in both strains. However, the presence of LPG between LT-P and IVD-P EVs was different. Groups of mice immunized with EVs emulsified in the adjuvant and challenged with IVD-P parasites showed decreased lesion size and parasitic load compared with the nonimmunized groups. The immunization regimen with two doses showed high IFN-γ and IgG2a titers in challenged mice with either IVD-P or LT-P EVs. IL-4 and IL-10 were detected in immunized mice, suggesting a mixed Th1/Th2 profile. EVs released by either IVD-P or LT-P induced a partial protective effect in an immunization model. Thus, our results uncover a potential protective role of EVs from L. amazonensis for cutaneous leishmaniasis. Moreover, long-term maintenance under in vitro conditions did not seem to affect EV release and their immunization properties in mice.

DC-SIGN Mediates the Interaction Between Neutrophils and Leishmania amazonensis-Infected Dendritic Cells to Promote DC Maturation and Parasite Elimination

Background

Leishmaniasis is a neglected arthropod-borne disease that affects millions of people worldwide. Successful Leishmania infections require the mitigation of immune cell functions leading to parasite survival and proliferation. A large body of evidence highlights the involvement of neutrophils (PMNs) and dendritic cells (DCs) in the establishment of immunological responses against these parasites. However, few studies, contemplate to what extent these cells interact synergistically to constrain Leishmania infection.

Objective

We sought to investigate how PMNs and infected DCs interact in an in vitro model of Leishmania amazonensis infection.

Material and Methods

Briefly, human PMNs and DCs were purified from the peripheral blood of healthy donors. Next, PMNs were activated with fibronectin and subsequently co-cultured with L. amazonensis-infected DCs.

Results

We observed that L. amazonensis-infected DC exhibited lower rates of infection when co-cultivated with either resting or activated PMNs. Surprisingly, we found that the release of neutrophil enzymes was not involved in Leishmania killing. Next, we showed that the interaction between PMNs and infected-DCs was intermediated by DC-SIGN, further suggesting that parasite elimination occurs in a contact-dependent manner. Furthermore, we also observed that TNFα and ROS production was dependent on DC-SIGN-mediated contact, as well as parasite elimination is dependent on TNFα production in the co-culture. Finally, we observed that direct contact between PMNs and DCs are required to restore the expression of DC maturation molecules during L. amazonensis infection.

Conclusion

Our findings suggest that the engagement of direct contact between PMNs and L. amazonensis-infected DC via DC-SIGN is required for the production of inflammatory mediators with subsequent parasite elimination and DC maturation.

Chalcone-rich extracts from Lonchocarpus cultratus roots present in vitro leishmanicidal and immunomodulatory activity

OBJECTIVES

This study aimed to evaluate the in vitro anti-Leishmania activity of chalcone-rich three extracts (LDR, LHR and LMR) from Lonchocarpus cultratus (Vell.) A.M.G. Azevedo & H.C. Lima against L. amazonensis. Also, the immunomodulatory and antioxidant capacity was assessed.

METHODS

Successive extraction with hexane, dichloromethane and methanol were performed to obtain LHR, LDR and LMR extracts from L. cultratus roots, which were characterized by 1H NMR. Promastigotes, amastigotes and peritoneal macrophages were exposed to crescent concentrations of the three extracts, and after incubation, the inhibition rates were determined to both types of cells, and morphological analyses were performed on the parasite. The immunomodulatory activity was determined against stimulated macrophages.

KEY FINDINGS

LDR, LHR and LMR inhibited promastigote cell growth (IC50 0.62 ± 0.3, 0.94 ± 0.5 and 1.28 ± 0.73 µg/ml, respectively) and reduced the number of amastigotes inside macrophages (IC50 1.36 ± 0.14, 1.54 ± 0.26 and 4.09 ± 0.88 µg/ml, respectively). The cytotoxicity against murine macrophages resulted in a CC50 of 13.12 ± 1.92, 92.93 ± 9.1 and >300 µg/ml, resulting in high selectivity index to promastigotes and amastigotes. The extracts also inhibited the nitric oxide secretion in RAW 264.7 macrophages. The antioxidant capacity resulted in a higher scavenger LMR ability.

CONCLUSIONS

These results suggest that L. cultratus extracts have anti-Leishmania potential, are non-toxic, and immunosuppress macrophages in vitro.

Determinants of Innate Immunity in Visceral Leishmaniasis and Their Implication in Vaccine Development

Leishmaniasis is endemic to the tropical and subtropical regions of the world and is transmitted by the bite of an infected sand fly. The multifaceted interactions between Leishmania, the host innate immune cells, and the adaptive immunity determine the severity of pathogenesis and disease development. Leishmania parasites establish a chronic infection by subversion and attenuation of the microbicidal functions of phagocytic innate immune cells such as neutrophils, macrophages and dendritic cells (DCs). Other innate cells such as inflammatory monocytes, mast cells and NK cells, also contribute to resistance and/or susceptibility to Leishmania infection. In addition to the cytokine/chemokine signals from the innate immune cells, recent studies identified the subtle shifts in the metabolic pathways of the innate cells that activate distinct immune signal cascades. The nexus between metabolic pathways, epigenetic reprogramming and the immune signaling cascades that drive the divergent innate immune responses, remains to be fully understood in Leishmania pathogenesis. Further, development of safe and efficacious vaccines against Leishmaniasis requires a broader understanding of the early interactions between the parasites and innate immune cells. In this review we focus on the current understanding of the specific role of innate immune cells, the metabolomic and epigenetic reprogramming and immune regulation that occurs during visceral leishmaniasis, and the strategies used by the parasite to evade and modulate host immunity. We highlight how such pathways could be exploited in the development of safe and efficacious Leishmania vaccines.

Blockade of TLR2 and TLR4 Attenuates Inflammatory Response and Parasite Load in Cutaneous Leishmaniasis

Human cutaneous leishmaniasis (CL) caused by Leishmania braziliensis is characterized by a pronounced inflammatory response associated with ulcer development. Monocytes/macrophages, the main cells harboring parasites, are largely responsible for parasite control. Toll-like receptor (TLR) signaling leads to the transcription of inflammatory mediators, such as IL-1β and TNF during innate immune response. TLR antagonists have been used in the treatment of inflammatory disease. The neutralization of these receptors may attenuate an exacerbated inflammatory response. We evaluated the ability of TLR2 and TLR4 antagonists to modulate host immune response in L. braziliensis-infected monocytes and cells from CL patient skin lesions. Following TLR2 and TLR4 neutralization, decreased numbers of infected cells and internalized parasites were detected in CL patient monocytes. In addition, reductions in oxidative burst, IL-1β, TNF and CXCL9 production were observed. TNF production by cells from CL lesions also decreased after TLR2 and TLR4 neutralization. The attenuation of host inflammatory response after neutralizing these receptors suggests the potential of TLR antagonists as immunomodulators in association with antimonial therapy in human cutaneous leishmaniasis.

Resistance Against Leishmania major Infection Depends on Microbiota-Guided Macrophage Activation

Innate immune cells present a dual role during leishmaniasis: they constitute the first line of host defense but are also the main host cells for the parasite. Response against the infection that results in the control of parasite growth and lesion healing depends on activation of macrophages into a classical activated phenotype. We report an essential role for the microbiota in driving macrophage and monocyte-derived macrophage activation towards a resistance phenotype against Leishmania major infection in mice. Both germ-free and dysbiotic mice showed a higher number of myeloid innate cells in lesions and increased number of infected cells, mainly dermal resident and inflammatory macrophages. Despite developing a Th1 immune response characterized by the same levels of IFN-γ production as the conventional mice, germ-free mice presented reduced numbers of iNOS+ macrophages at the peak of infection. Absence or disturbance of host microbiota impaired the capacity of bone marrow-derived macrophage to be activated for Leishmania killing in vitro, even when stimulated by Th1 cytokines. These cells presented reduced expression of inos mRNA, and diminished production of microbicidal molecules, such as ROS, while presenting a permissive activation status, characterized by increased expression of arginase I and il-10 mRNA and higher arginase activity. Colonization of germ-free mice with complete microbiota from conventional mice rescued their ability to control the infection. This study demonstrates the essential role of host microbiota on innate immune response against L. major infection, driving host macrophages to a resistance phenotype.