Modulation of Cytokines and Extracellular Matrix Proteins Expression by Leishmania amazonensis in Susceptible and Resistant Mice

Unraveling molecular mechanistic disparities in pathogenic visceral Leishmania resistance between reptiles and mammals through comparative transcriptomic analyses

Leishmaniasis is one of the most important neglected tropical parasitic diseases, manifesting various clinical forms depending on the parasite species and the genetic background of the host. In order to elucidate the underlying mechanisms of reptilian defense against pathogenic Leishmania species and to delineate the global gene expression profile alterations during host-pathogen interaction, we established experimental animal and cell models using both heterothermic lizards (Phrynocephalus przewalskii) and homothermic mammals (BALB/c mice) infected with pathogenic Leishmania infantum (high virulence HCZ strain) and Leishmania donovani (low virulence 801 strain). Overall, the lizards didn't show any obvious clinical symptoms or immune responses in vivo. Using RNA-seq methodology, differentially expressed genes identified in the HCZ and 801-comparison groups of P. przewalskii were primarily associated with arginine biosynthesis, the MAPK signaling pathway and the PI3K-Akt signaling pathway. In contrast, higher parasite loads, exacerbated hepatic inflammatory lesions and enhanced immune responses were observed in BALB/c mice, with DEGs predominantly associated with immunological diseases, innate and adaptive immune responses. By integrating transcriptional data from reptile and mammalian hosts, we elucidated the pivotal role of amino acid metabolism and lipid metabolism in parasite control. In contrast to findings from animal experiments, Leishmania parasites effectively infected peritoneal macrophages of lizards in vitro, demonstrating a high infection rate. Furthermore, we used RT-qPCR to detect changes in cytokine expression in macrophages and found that Th1-type cytokines were significantly upregulated in lizards, facilitating the clearance of the HCZ strain 24 hours post-infection. Conversely, cytokine expression was generally suppressed in BALB/c mice, allowing immune evasion by the parasites.

Case Notification of Cutaneous Leishmaniasis at Different Elevations in the North-Central Ethiopia from 2018 To 2022

Background

We aimed to analyze a four-year trend of Cutaneous leishmaniasis (CL) to determine risk levels and hotspots in North-central Ethiopia.

Methods

This retrospective study was conducted at Boru Meda Hospital (BMH) from March to April 2023, focusing on CL patients treated at the leishmaniasis treatment center (LTC). Data collected included age, gender, CL type, and other clinical factors. Each patient's origin was traced and geographically mapped by elevation to assess CL risk levels.

Results

There were a total of 573 CL patients reported from 46 districts, with a higher number of male patients (n=356) compared to female patients (n=217) (P <0.001). The median age of the patients was 21 years [15-30], with the highest number of CL cases observed among individuals aged 16 to 30 years. The majority of cases (69%) presented with localized CL (LCL). About 39% of patients had a previous treatment history for CL. A significant clustering of CL cases was observed at elevation of 2301-3300 meters above sea level (χ2:17.5; P <0.001), with the highest incidence (case notification) of 14.2/100,000 population.

Conclusion

Foci of CL, were burdened at higher elevations and no clinical variation were observed between elevation differences. The majority of cases were concentrated in an area covering approximately 21.4% of the total land mass. CL continues to be a significant issue in North-central Ethiopia and has the potential to spread to new areas.

Diagnosis of Cutaneous Leishmaniasis Using FTIR Spectroscopy and Machine Learning: An Animal Model Study

Cutaneous leishmaniasis (CL) is a polymorphic and spectral skin disease caused by Leishmania spp. protozoan parasites. CL is difficult to diagnose because conventional methods are time-consuming, expensive, and low-sensitive. Fourier transform infrared spectroscopy (FTIR) with machine learning (ML) algorithms has been explored as an alternative to achieve fast and accurate results for many disease diagnoses. Besides the high accuracy demonstrated in numerous studies, the spectral variations between infected and noninfected groups are too subtle to be noticed. Since variability in sample set characteristics (such as sex, age, and diet) often leads to significant data variance and limits the comprehensive understanding of spectral characteristics and immune responses, we investigate a novel methodology for diagnosing CL in an animal model study. Blood serum, skin lesions, and draining popliteal lymph node samples were collected from Leishmania (Leishmania) amazonensis-infected BALB/C mice under experimental conditions. The FTIR method and ML algorithms accurately differentiated between infected (CL group) and noninfected (control group) samples. The best overall accuracy (∼72%) was obtained in an external validation test using principal component analysis and support vector machine algorithms in the 1800-700 cm-1 range for blood serum samples. The accuracy achieved in analyzing skin lesions and popliteal lymph node samples was satisfactory; however, notable disparities emerged in the validation tests compared to results obtained from blood samples. This discrepancy is likely attributed to the elevated sample variability resulting from molecular compositional differences. According to the findings, the successful functioning of prediction models is mainly related to data analysis rather than the differences in the molecular composition of the samples.

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.

CXCR5 and TIM-3 expressions define distinct exhausted T cell subsets in experimental cutaneous infection with Leishmania mexicana

T-cell exhaustion is a key stage in chronic infections since it limits immunopathology, but also hinders the elimination of pathogens. Exhausted T (Tex) cells encompass dynamic subsets, including progenitor cells that sustain long-term immunity through their memory/stem like properties, and terminally-differentiated cells, resembling the so-called Tex cells. The presence of Tex cells in chronic leishmaniasis has been reported in humans and murine models, yet their heterogeneity remains unexplored. Using flow cytometry, we identified Tex cells subtypes based on PD-1, CXCR5 and TIM-3 expressions in draining lymph nodes (dLNs) and lesion sites of C57BL/6 mice infected with L. mexicana at 30-, 60- and 90-days post-infection. We showed that infected mice developed a chronic infection characterized by non-healing lesions with a high parasite load and impaired Th1/Th2 cytokine production. Throughout the infection, PD-1+ cells were observed in dLNs, in addition to an enhanced expression of PD-1 in both CD4+ and CD8+ T lymphocytes. We demonstrated that CD4+ and CD8+ T cells were subdivided into PD-1+CXCR5+TIM-3- (CXCR5+), PD-1+CXCR5+TIM-3+ (CXCR5+TIM-3+), and PD-1+CXCR5-TIM-3+ (TIM-3+) subsets. CXCR5+ Tex cells were detected in dLNs during the whole course of the infection, whereas TIM-3+ cells were predominantly localized in the infection sites at day 90. CXCR5+TIM-3+ cells only increased at 30 and 60 days of infection in dLNs, whereas no increase was observed in the lesions. Phenotypic analysis revealed that CXCR5+ cells expressed significantly higher levels of CCR7 and lower levels of CX3CR1, PD-1, TIM-3, and CD39 compared to the TIM-3+ subset. CXCR5+TIM-3+ cells expressed the highest levels of all exhaustion-associated markers and of CX3CR1. In agreement with a less exhausted phenotype, the frequency of proliferating Ki-67 and IFN-γ expressing cells was significantly higher in the CXCR5+ subset within both CD4+ and CD8+ T cells compared to their respective TIM-3+ subsets, whereas CD8+CXCR5+TIM-3+ and CD8+TIM-3+ subsets showed an enhanced frequency of degranulating CD107a+ cells. In summary, we identified a novel, less-differentiated CXCR5+ Tex subset in experimental cutaneous leishmaniasis caused by L. mexicana. Targeting these cells through immune checkpoint inhibitors such as anti-PD-1 or anti PD-L1 might improve the current treatment for patients with the chronic forms of leishmaniasis.

Macrophages in immunoregulation and therapeutics

Macrophages exist in various tissues, several body cavities, and around mucosal surfaces and are a vital part of the innate immune system for host defense against many pathogens and cancers. Macrophages possess binary M1/M2 macrophage polarization settings, which perform a central role in an array of immune tasks via intrinsic signal cascades and, therefore, must be precisely regulated. Many crucial questions about macrophage signaling and immune modulation are yet to be uncovered. In addition, the clinical importance of tumor-associated macrophages is becoming more widely recognized as significant progress has been made in understanding their biology. Moreover, they are an integral part of the tumor microenvironment, playing a part in the regulation of a wide variety of processes including angiogenesis, extracellular matrix transformation, cancer cell proliferation, metastasis, immunosuppression, and resistance to chemotherapeutic and checkpoint blockade immunotherapies. Herein, we discuss immune regulation in macrophage polarization and signaling, mechanical stresses and modulation, metabolic signaling pathways, mitochondrial and transcriptional, and epigenetic regulation. Furthermore, we have broadly extended the understanding of macrophages in extracellular traps and the essential roles of autophagy and aging in regulating macrophage functions. Moreover, we discussed recent advances in macrophages-mediated immune regulation of autoimmune diseases and tumorigenesis. Lastly, we discussed targeted macrophage therapy to portray prospective targets for therapeutic strategies in health and diseases.

A New Strategy for Mapping Epitopes of LACK and PEPCK Proteins of Leishmania amazonensis Specific for Major Histocompatibility Complex Class I

Leishmaniasis represents a complex of diseases with a broad clinical spectrum and epidemiological diversity, considered a major public health problem. Although there is treatment, there are still no vaccines for cutaneous leishmaniasis. Because Leishmania spp. is an intracellular protozoan with several escape mechanisms, a vaccine must provoke cellular and humoral immune responses. Previously, we identified the Leishmania homolog of receptors for activated C kinase (LACK) and phosphoenolpyruvate carboxykinase (PEPCK) proteins as strong immunogens and candidates for the development of a vaccine strategy. The present work focuses on the in silico prediction and characterization of antigenic epitopes that might interact with mice or human major histocompatibility complex class I. After immunogenicity prediction on the Immune Epitope Database (IEDB) and the Database of MHC Ligands and Peptide Motifs (SYFPEITHI), 26 peptides were selected for interaction assays with infected mouse lymphocytes by flow cytometry and ELISpot. This strategy identified nine antigenic peptides (pL1-H2, pPL3-H2, pL10-HLA, pP13-H2, pP14-H2, pP15-H2, pP16-H2, pP17-H2, pP18-H2, pP26-HLA), which are strong candidates for developing a peptide vaccine against leishmaniasis.

Sex-Biased Control of Inflammation and Metabolism by a Mitochondrial Nod-Like Receptor

Mitochondria regulate steroid hormone synthesis, and in turn sex hormones regulate mitochondrial function for maintaining cellular homeostasis and controlling inflammation. This crosstalk can explain sex differences observed in several pathologies such as in metabolic or inflammatory disorders. Nod-like receptor X1 (NLRX1) is a mitochondria-associated innate receptor that could modulate metabolic functions and attenuates inflammatory responses. Here, we showed that in an infectious model with the human protozoan parasite, Leishmania guyanensis, NLRX1 attenuated inflammation in females but not in male mice. Analysis of infected female and male bone marrow derived macrophages showed both sex- and genotype-specific differences in both inflammatory and metabolic profiles with increased type I interferon production, mitochondrial respiration, and glycolytic rate in Nlrx1-deficient female BMDMs in comparison to wild-type cells, while no differences were observed between males. Transcriptomics of female and male BMDMs revealed an altered steroid hormone signaling in Nlrx1-deficient cells, and a “masculinization” of Nlrx1-deficient female BMDMs. Thus, our findings suggest that NLRX1 prevents uncontrolled inflammation and metabolism in females and therefore may contribute to the sex differences observed in infectious and inflammatory diseases.

Nitric Oxide Induction in Peritoneal Macrophages by a 1,2,3-Triazole Derivative Improves Its Efficacy upon Leishmania amazonensis In Vitro Infection

1,2,3-Triazole is one of the most flexible chemical scaffolds broadly used in various fields. Here, we report the antileishmanial activity of 1,2,3-triazole derivatives, the ultrastructural alterations induced by their treatment, and the nitric oxide (NO) modulation effect on their efficacy against Leishmania amazonensis in vitro infection. After the screening of eleven compounds, compound 4 exhibited better results against L. amazonensis promastigotes (IC₅₀ = 15.52 ± 3.782 μM) and intracellular amastigotes (IC₅₀ = 4.10 ± 1.136 μM), 50% cytotoxicity concentration at 84.01 ± 3.064 μM against BALB/c peritoneal macrophages, and 20.49-fold selectivity for the parasite over the cells. Compound 4 induced ultrastructural mitochondrial alterations and lipid inclusions in L. amazonensis promastigotes, upregulated tumor necrosis factor α, interleukin (IL)-1β, IL-6, IL-12, and IL-10 messenger RNA expressions, and enhanced the NO production, verified by nitrite (p = 0.0095) and inducible nitric oxide synthase expression (p = 0.0049) quantification, which played an important role in its activity against intramacrophagic L. amazonensis. In silico prediction in association with antileishmanial activity results showed compound 4 as a hit compound with promising potential for further studies of new leishmaniasis treatment options.

Phenotypical and genotypical differences among Leishmania (Leishmania) amazonensis isolates that caused different clinical frames in humans and dogs: A systematic review

Leishmania (Leishmania) amazonensis is an important etiological agent of American cutaneous leishmaniasis (ACL) in Brazil. The species causes a large spectrum of clinical manifestations in humans and dogs, ranging from cutaneous, cutaneous diffuse, mucocutaneous, and visceral involvement, however, the factors that drive the development of different disease forms by the same species are not yet fully known. In the present work, it was systematically reviewed the studies addressing phenotypic and genotypic characteristics of Leishmania (L.) amazonensis isolates causing cutaneous and visceral clinical frames in humans and dogs, comparing the results observed. For this, four research databases were searched for the following keywords: (Leishmania amazonensis AND visceral leishmaniasis) AND (tropism OR virulence OR visceralization OR adaptations OR mutation OR clinical presentation OR resistance OR survival OR wide spectrum). The results revealed that the complexity disease seems to involve the combination of genetic factors of the parasite (as modifications in molecules related to the virulence and metabolism) and also of the host's immune background and status. Nonetheless, the exact mechanism that leads to different clinical manifestations between strains of the same species is still uncertain and future studies must be developed to better elucidate this phenomenon.

Amentoflavone as an Ally in the Treatment of Cutaneous Leishmaniasis: Analysis of Its Antioxidant/Prooxidant Mechanisms

Treatment of leishmaniasis is a challenging subject. Although available, chemotherapy is limited, presenting toxicity and adverse effects. New drugs with antileishmanial activity are being investigated, such as antiparasitic compounds derived from plants. In this work, we investigated the antileishmanial activity of the biflavonoid amentoflavone on the protozoan Leishmania amazonensis. Although the antileishmanial activity of amentoflavone has already been reported in vitro, the mechanisms involved in the parasite death, as well as its action in vivo, remain unknown. Amentoflavone demonstrated activity on intracellular amastigotes in macrophages obtained from BALB/c mice (IC₅₀ 2.3 ± 0.93 μM). No cytotoxicity was observed and the selectivity index was estimated as greater than 10. Using BALB/c mice infected with L. amazonensis we verified the effect of an intralesional treatment with amentoflavone (0.05 mg/kg/dose, in a total of 5 doses every 4 days). Parasite quantification demonstrated that amentoflavone reduced the parasite load in treated footpads (46.3% reduction by limiting dilution assay and 56.5% reduction by Real Time Polymerase Chain Reaction). Amentoflavone decreased the nitric oxide production in peritoneal macrophages obtained from treated animals. The treatment also increased the expression of ferritin and decreased iNOS expression at the site of infection. Furthemore, it increased the production of ROS in peritoneal macrophages infected in vitro. The increase of ROS in vitro, associated with the reduction of NO and iNOS expression in vivo, points to the antioxidant/prooxidant potential of amentoflavone, which may play an important role in the balance between inflammatory and anti-inflammatory patterns at the infection site. Taken together these results suggest that amentoflavone has the potential to be used in the treatment of cutaneous leishmaniasis, working as an ally in the control and development of the lesion.