Proteinases as virulence factors in Leishmania spp. infection in mammals

Targeting cysteine protease B to discover antileishmanial drugs: Directions and advances

Leishmaniasis is a severe disease and results in high mortality rates. Despite this, there are few drugs to treat and with various limitations such as toxicity and resistance, which justifies the search for new drugs. Thus, cysteine protease B (CPB) is a promising target against leishmania due to its immunomodulatory function related to the parasite's virulence and its interaction with the host. Thus, this perspective showed the potential of CPB in drug design and the main insights that can be used in subsequent drug design works. In fact, the aziridine analogs are the most explored against CPB due to the promising results and provide several insights into drug design. Also, it is noteworthy that one of the biggest challenges is target selectivity. Knowledge about substrate binding and other factors, such as the reversibility of inhibitors, is also needed. In addition, exploring target selectivity patterns is critical to developing CP inhibitors for clinical use to combat this threatening agent.

A Virtual Screening Approach to Evaluate the Multitarget Potential of a Chalcone Library with Binding Properties to Oligopeptidase B and Cysteine Proteinase B from Leishmania (Viannia) braziliensis

Leishmaniasis remains a significant public health problem in Brazil, particularly due to Leishmania (Viannia) braziliensis, which is associated with severe dermatological syndromes. The current treatments are limited by toxicity and uncertain efficacy, highlighting the need for new compounds with pharmacological potential. This study investigates chalcones as multitarget binding agents for oligopeptidase B (OPB) and cysteine proteinase B (CPB), which are critical pathogenic determinants of L. (V.) braziliensis. The methodology involved replacing methoxy groups with aryl motifs at various positions within the chalcone structures and introducing specific functional groups at the C-4 position. This was followed by a virtual screening approach using molecular docking to assess interactions with the target proteinases. Several chalcones from the virtual library (n = 178) exhibited high binding affinities for OPB and CPB, outperforming control ligands. A total of 30 chalcones with multitarget potential were identified, with fluorinated compounds C-191 and C-135 emerging as promising inhibitors, distinguished by the best energy rankings for both enzymes. ADMET analyses confirmed the viability of these chalcones as drug candidates, with most adhering to Lipinski's rules. These data suggest that chalcones may provide new multitarget treatment options for leishmaniasis.

A short ncRNA modulates gene expression and affects stress response and parasite differentiation in Leishmania braziliensis

The protozoan parasite Leishmania spp. is a causative agent of leishmaniasis, a disease that affects millions of people in more than 80 countries worldwide. Apart from its medical relevance, this organism has a genetic organization that is unique among eukaryotes. Studies of the mechanisms regulating gene expression in Leishmania led us to investigate noncoding RNAs (ncRNAs) as regulatory elements. We previously identified differentially expressed (DE) ncRNAs in Leishmania braziliensis with potential roles in the parasite biology and development. Herein, we present a functional analysis of one such DE ncRNA, the 147-nucleotide-long transcript ncRNA97, which is preferentially expressed in amastigotes, the replicative form within mammalian phagocytes. By RT-qPCR the ncRNA97 was detected in greater quantities in the nucleus under physiological conditions and in the cytoplasm under nutritional stress. Interestingly, the transcript is protected at the 5' end but is not processed by the canonical trypanosomatid trans-splicing mechanism, according to the RNA circularization assay. ncRNA97 knockout (KO) and addback (AB) transfectants were generated and subjected to phenotypic analysis, which revealed that the lack of ncRNA97 impairs the starvation response and differentiation to the infective form. Comparative transcriptomics of ncRNA97KO and parental cells revealed that transcripts encoding amastigote-specific proteins were affected. This pioneering work demonstrates that ncRNAs contribute to the developmental regulatory mechanisms of Leishmania.

Advances in Cysteine Protease B Inhibitors for Leishmaniasis Treatment

The expression and release of cysteine proteases by Leishmania spp. and their virulence factors significantly influence the modulation of host immune responses and metabolism, rendering cysteine proteases intriguing targets for drug development. This review article explores the substantial role of cysteine protease B (CPB) in medicinal chemistry from 2001 to 2024, particularly concerning combatting Leishmania parasites. We delve into contemporary advancements and potential prospects associated with targeting cysteine proteases for therapeutic interventions against leishmaniasis, emphasizing drug discovery in this context. Computational analysis using the pkCSM tool assessed the physicochemical properties of compounds, providing valuable insights into their molecular characteristics and drug-like potential, enriching our understanding of the pharmacological profiles, and aiding rational inhibitor design. Our investigation highlights that while nonpeptidic compounds constitute the majority (69.2%, 36 compounds) of the dataset, peptidomimetic- based derivatives (30.8%, 16 compounds) also hold promise in medicinal chemistry. Evaluating the most promising compounds based on dissociation constant (Ki) and half maximal inhibitory concentration (IC50) values revealed notable potency, with 41.7% and 80.0% of nonpeptidic compounds exhibiting values < 1 μM, respectively. On the other hand, all peptidic compounds evaluated for Ki (43.8%) and IC50 (31.3%) obtained values < 1 μM, respectively. Further analysis identified specific compounds within both categories (nonpeptidic: 1, 2, and 4; peptidic: 48-52) as particularly promising, warranting deeper investigation into their structure-activity relationships. These findings underscore the diverse landscape of inhibitors in medicinal chemistry and highlight the potential of both nonpeptidic and peptide-based compounds as valuable assets in therapeutic development against leishmaniasis.

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.

Anti-Leishmania major Properties of Nuphar lutea (Yellow Water Lily) Leaf Extracts and Purified 6,6' Dihydroxythiobinupharidine (DTBN)

Cutaneous leishmaniasis (CL) is a zoonotic disease, manifested as chronic ulcers, potentially leaving unattractive scars. There is no preventive vaccination or optimal medication against leishmaniasis. Chemotherapy generally depends upon a small group of compounds, each with its own efficacy, toxicity, and rate of drug resistance. To date, no standardized, simple, safe, and highly effective regimen for treating CL exists. Therefore, there is an urgent need to develop new optimal medication for this disease. Sesquiterpen thio-alkaloids constitute a group of plant secondary metabolites that bear great potential for medicinal uses. The nupharidines found in Nuphar lutea belong to this group of compounds. We have previously published that Nuphar lutea semi-purified extract containing major components of nupharidines has strong anti-leishmanial activity in vitro. Here, we present in vivo data on the therapeutic benefit of the extract against Leishmania major (L. major) in infected mice. We also expanded these observations by establishing the therapeutic effect of the extract-purified nupharidine 6,6'-dihydroxythiobinupharidine (DTBN) in vitro against promastigotes and intracellular amastigotes as well as in vivo in L. major-infected mice. The results suggest that this novel anti-parasitic small molecule has the potential to be further developed against Leishmania.

Recognition of Immunoreactive Proteins in Leishmania infantum Amastigote-Like and Promastigote Using Sera of Visceral Leishmaniasis Patients: a Preliminary Study

PURPOSE

Visceral leishmaniasis (VL) is a systemic and parasitic disease that is usually fatal if left untreated. VL is endemic in different parts of Iran and is caused mainly by Leishmania infantum. This study aimed to recognition immunoreactive proteins in amastigote-like and promastigote stages of L. infantum (Iranian strain) by antibodies present in the sera of VL patients.

METHODS

Total protein extract from amastigote-like and promastigote cells was separated by two-dimensional electrophoresis (2DE). To detect the immunoreactive proteins, 2DE immunoblotting method was performed using different pools of VL patients' sera.

RESULTS

Approximately 390 and 430 protein spots could be separated in 2DE profiles of L. infantum amastigote-like and promastigote stages, respectively. In immunoblotting method, approximately 295 and 135 immunoreactive proteins of amastigotes-like reacted with high antibody titer serum pool and low antibody titer serum pool, respectively. Approximately 120 and 85 immunoreactive proteins of promastigote extract were recognized using the high antibody titer sera pool and low antibody titer sera, respectively.

CONCLUSION

The present study has recognized a number of antigenic diversity proteins based on the molecular weight and pH in amastigote-like and promastigote stages of L. infantum. These results provide us a new concept for further analysis development in the field of diagnosis biomarkers and vaccine targets.

The effects of Leishmania RNA virus 2 (LRV2) on the virulence factors of L. major and pro-inflammatory biomarkers: an in vitro study on human monocyte cell line (THP-1)

BACKGROUND

Cutaneous Leishmaniasis (CL) is a parasitic disease with diverse outcomes. Clinical diversity is influenced by various factors such as Leishmania species and host genetic background. The role of Leishmania RNA virus (LRV), as an endosymbiont, is suggested to not only affect the pathogenesis of Leishmania, but also impact host immune responses. This study aimed to investigate the influence of LRV2 on the expression of a number of virulence factors (VFs) of Leishmania and pro-inflammatory biomarkers.

MATERIALS AND METHODS

Sample were obtained from CL patients from Golestan province. Leishmania species were identified by PCR (LIN 4, 17), and the presence of LRV2 was checked using the semi-nested PCR (RdRp gene). Human monocyte cell line (THP-1) was treated with three isolates of L. major with LRV2 and one isolate of L. major without LRV2. The treatments with four isolates were administered for the time points: zero, 12, 24, 36, and 48 h after co-infection. The expression levels of Leishmania VFs genes including GP63, HSP83, and MPI, as well as pro-inflammatory biomarkers genes including NLRP3, IL18, and IL1β, were measured using quantitative real-time PCR.

RESULTS

The expression of GP63, HSP83, and MPI revealed up-regulation in LRV2 + isolates compared to LRV2- isolates. The expression of the pro-inflammatory biomarkers including NLRP3, IL1β, and IL18 genes in LRV2- were higher than LRV2 + isolates.

CONCLUSION

This finding suggests that LRV2 + may have a probable effect on the Leishmania VFs and pro-inflammatory biomarkers in the human macrophage model.

Investigation of the Potential Targets behind the Promising and Highly Selective Antileishmanial Action of Synthetic Flavonoid Derivatives

Leishmaniases are among the neglected tropical diseases that still cause devastating health, social, and economic consequences to more than 350 million people worldwide. Despite efforts to combat these vector-borne diseases, their incidence does not decrease. Meanwhile, current antileishmanial drugs are old and highly toxic, and safer presentations are unaffordable to the most severely affected human populations. In a previous study by our research group, we synthesized 17 flavonoid derivatives that demonstrated impressive inhibition capacity against rCPB2.8, rCPB3, and rH84Y. These cysteine proteases are highly expressed in the amastigote stage, the target form of the parasite. However, although these compounds have been already described in the literature, until now, the amastigote effect of any of these molecules has not been proven. In this work, we aimed to deeply analyze the antileishmanial action of this set of synthetic flavonoid derivatives by correlating their ability to inhibit cysteine proteases with the action against the parasite. Among all the synthesized flavonoid derivatives, 11 of them showed high activity against amastigotes of Leishmania amazonensis, also providing safety to mammalian host cells. Furthermore, the high production of nitric oxide by infected cells treated with the most active cysteine protease B (CPB) inhibitors confirms a potential immunomodulatory response of macrophages. Besides, considering flavonoids as multitarget drugs, we also investigated other potential antileishmanial mechanisms. The most active compounds were selected to investigate another potential biological pathway behind their antileishmanial action using flow cytometry analysis. The results confirmed an oxidative stress after 48 h of treatment. These data represent an important step toward the validation of CPB as an antileishmanial target, as well as aiding in new drug discovery studies based on this protease.

Gelatin Zymography of Major Proteases in Exosomes of Leishmania major Promastigotes

Background

Enzymatic digestion of extra cellular matrix proteins by proteinases of Leishmania promastigotes is a complex process. Hence, studies on functional proteomics of these enzymes can help select these enzymes as possible vaccine candidates or selecting candidates for chemotherapy and immunotherapy. Several proteolytic enzymes are involved in virulence of Leishmania spp. These enzymes are mostly serine, cysteine and metalloproteases. We aimed to detect proteases in Leishmania promastigote exosomes.

Methods

Serine, cysteine and metalloproteases were investigated in exosomes and lysate of L. major promastigote using gelatin zymography. The study was carried out in the Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran, in 2021.

Results

Zymography findings of metalloproteinases showed transparent bands, including a 63-kDa glycoprotein (GP63). This glycoprotein is a major surface metalloproteinase. In addition, transparent bands belonged to serin proteases and cathepsin were demonstrated in gels associated to Leishmania promastigote lysate and exosomes.

Conclusion

Several metalloproteases, serin proteases and cathepsins were shown in promastigote lysate and exosomes of L. major, which could purified and used as fractions for immunodiagnostic.

Detection and activity of MMP-2 and MMP-9 in Leishmania amazonensis and Leishmania braziliensis promastigotes

Metalloproteinases (MMPs) are remarkable zinc-dependent endopeptidases, critical for degrading components of the extracellular matrix, thus actively influencing cell migration. Their impact on intracellular parasites, such as the enigmatic protozoan Leishmania, elicits intriguing queries. This study explores into the untapped territory of MMP-2 and MMP-9 within Leishmania spp. promastigotes. Notably, we successfully detected and quantified these MMPs, while also evaluating their activity in two distinct Leishmania species-L. amazonensis (La) and L. braziliensis (Lb)-at various growth stages and isolated from distinct clinical tegumentar disease forms. The results unveiled the presence of MMP-2 and MMP-9 in both species, albeit with distinct localization patterns. Specifically, MMP-9 exhibited significantly higher gelatinolytic activity in La when compared to Lb. Moreover, our data cleverly illustrated the presence and release of MMP-2 and MMP-9 by La and Lb promastigotes, exposing their ability to invade and migrate within a collagen matrix. This pioneering study establishes a compelling correlation between MMP-2 and MMP-9 and their potential role in the dynamics of La and Lb infection. Suggesting their potential as prognostic markers for severe leishmaniasis and promising target molecules for therapeutic interventions, this research opens new avenues for combatting this debilitating parasitic disease.

Leishmania species: A narrative review on surface proteins with structural aspects involved in host-pathogen interaction

In tropical and subtropical regions of the world, leishmaniasis is endemic and causes a range of clinical symptoms in people, from severe tegumentary forms (such as cutaneous, mucocutaneous, and diffuse leishmaniasis) to lethal visceral forms. The protozoan parasite of the genus Leishmania causes leishmaniasis, which is still a significant public health issue, according to the World Health Organization 2022. The public's worry about the neglected tropical disease is growing as new foci of the illness arise, which are exacerbated by alterations in behavior, changes in the environment, and an enlarged range of sand fly vectors. Leishmania research has advanced significantly during the past three decades in a few different avenues. Despite several studies on Leishmania, many issues, such as illness control, parasite resistance, parasite clearance, etc., remain unresolved. The key virulence variables that play a role in the pathogenicity-host-pathogen relationship of the parasite are comprehensively discussed in this paper. The important Leishmania virulence factors, such as Kinetoplastid Membrane Protein-11 (KMP-11), Leishmanolysin (GP63), Proteophosphoglycan (PPG), Lipophosphoglycan (LPG), Glycosylinositol Phospholipids (GIPL), and others, have an impact on the pathophysiology of the disease and enable the parasite to spread the infection. Leishmania infection may arise from virulence factors; they are treatable with medications or vaccinations more promptly and might greatly shorten the duration of treatment. Additionally, our research sought to present a modeled structure of a few putative virulence factors that might aid in the development of new chemotherapeutic approaches for the treatment of leishmaniasis. The predicted virulence protein's structure is utilized to design novel drugs, therapeutic targets, and immunizations for considerable advantage from a higher understanding of the host immune response.

Degron Pathways and Leishmaniasis: Debating Potential Roles of Leishmania spp. Proteases Activity on Guiding Hosts Immune Response and Their Relevance to the Development of Vaccines

Degrons are short peptide sequences that signalize target sites for protein degradation by proteases. Herein, we bring forth the discussion on degrons present in proteins related to the immune system of Mus musculus that are potential targets for cysteine and serine proteases of Leishmania spp. and their possible roles on host immune regulation by parasites. The Merops database was used to identify protease substrates and proteases sequence motifs, while MAST/MEME Suite was applied to find degron motifs in murine cytokines (IFN-y, IL-4, IL-5, IL-13, IL-17) and transcription factors (NF-kappaB, STAT-1, AP-1, CREB, and BACH2). STRING tool was used to construct an interaction network for the immune factors and SWISS-MODEL server to generate three-dimensional models of proteins. In silico assays confirm the occurrence of degrons in the selected immune response factors. Further analyses were conducted only in those with resolved three-dimensional structures. The predicted interaction network of degron-containing M. musculus proteins shows the possibility that the specific activity of parasite proteases could interfere with the trend of Th1/Th2 immune responses. Data suggest that degrons may play a role in the immune responses in leishmaniases as targets for parasite proteases activity, directing the degradation of specific immune-related factors.

Effect of Leishmania RNA virus 2 on virulence factors and cytokines gene expression in a human macrophage infected with Leishmania major: A preliminary study

Cutaneous leishmaniasis (CL) is one of the most important infectious parasitic diseases in the world caused by the Leishmania parasite. In recent decades, the presence of a virus from the Totiviridae family has been proven in some Leishmania species. Although the existence of LRV2 in the Old world Leishmania species has been confirmed, almost no studies have been done to determine the potential impact of LRV2 on the immunopathogenicity of the Leishmania parasite. In this preliminary study, we measured the expression of target genes, including Glycoprotein 63 (gp63), Heat Shock Protein 70 (hsp70), Cysteine Protease b (cpb), Interleukin 1 beta (IL-1β), IL8 and IL-12 in LRV2 positive Leishmania major strain (LRV2⁺L. major) and LRV2 negative L. major strain (LRV2^-L. major). We exposed THP-1, a human leukemia monocytic cell line, to promastigotes of both strains. After the initial infection, RNA was extracted at different time points, and the relative gene expression was determined using a real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Findings showed that the presence of LRV2 in L. major was able to increase the expression of gp63, hsp70, and cpb genes; also, we observed lower levels of expression in cytokine genes of IL-1β, IL-8, IL-12 in the presence of LRV2⁺, which are critical factors in the host's immune response against leishmaniasis. These changes could suggest that the presence of LRV2 in L. major parasite may change the outcome of the disease and increase the probability of Leishmania survival; nevertheless, further studies are needed to confirm our results.

Comparative Degradome Analysis of the Bovine Piroplasmid Pathogens Babesia bovis and Theileria annulata

Babesia bovis and Theileria annulata are tick-borne hemoprotozoans that impact bovine health and are responsible for considerable fatalities in tropical and subtropical regions around the world. Both pathogens infect the same vertebrate host, are closely related, and contain similar-sized genomes; however, they differ in invertebrate host specificity, absence vs. presence of a schizont stage, erythrocyte invasion mechanism, and transovarial vs. transstadial transmission. Phylogenetic analysis and bidirectional best hit (BBH) identified a similar number of aspartic, metallo, and threonine proteinases and nonproteinase homologs. In contrast, a considerably increased number of S54 serine rhomboid proteinases and S9 nonproteinase homologs were identified in B. bovis, whereas C1A cysteine proteinases and A1 aspartic nonproteinase homologs were found to be expanded in T. annulata. Furthermore, a single proteinase of families S8 (subtilisin-like protein) and C12 (ubiquitin carboxyl-terminal hydrolase), as well as four nonproteinase homologs, one with dual domains M23-M23 and three with S9-S9, were exclusively present in B. bovis. Finally, a pronounced difference in species-specific ancillary domains was observed between both species. We hypothesize that the observed degradome differences represent functional correlates of the dissimilar life history features of B. bovis and T. annulata. The presented improved classification of piroplasmid proteinases will facilitate an informed choice for future in-depth functional studies.

Unraveling the role of natural killer cells in leishmaniasis

NK cells are known as frontline responders that are efficient in combating several maladies as well as leishmaniasis caused by Leishmania spp. As such they are being investigated to be used for adoptive transfer therapy and vaccine. In spite of the lack of antigen-specific receptors at their surface, NK cells can selectively recognize pathogens, accomplished by the activation of the receptors on the NK cell surface and also as the result of their effector functions. Activation of NK cells can occur through interaction between TLR-2 expressed on NK cells and. LPG of Leishmania parasites. In addition, NK cell activation can occur by cytokines (e.g., IFN-γ and IL-12) that also lead to producing cytokines and chemokines and lysis of target cells. This review summarizes several evidences that support NK cells activation for controlling leishmaniasis and the potentially lucrative roles of NK cells during leishmaniasis. Furthermore, we discuss strategies of Leishmania parasites in inhibiting NK cell functions. Leishmania LPG can utilizes TLR2 to evade host-immune responses. Also, Leishmania GP63 can directly binds to NK cells and modulates NK cell phenotype. Finally, this review analyzes the potentialities to harness NK cells effectiveness in therapy regimens and vaccinations.

Characterization of Leishmania (L.) amazonensis oligopeptidase B and its role in macrophage infection

Leishmania spp. are parasitic protozoa that cause leishmaniasis, a disease endemic in 98 countries. Leishmania promastigotes are transmitted by the vector and differentiate into amastigotes within phagocytic cells of the vertebrate host. To survive in multiple and hostile environments, the parasite has several virulence factors. Oligopeptidase B (OPB) is a serine peptidase present in prokaryotes, some eukaryotes and some higher plants. It has been considered a virulence factor in trypanosomatids, but only a few studies, performed with Old World species, analysed its role in Leishmania virulence or infectivity.L. (L.) amazonensis is an important agent of cutaneous leishmaniasis in Brazil. The L. (L.) amazonensis OPB encoding gene has been sequenced and analysed in silico but has never been expressed. In this work, we produced recombinant L. (L.) amazonensis OPB and showed that its pH preferences, Km and inhibition patterns are similar to those reported for L. (L.) major and L. (L.) donovani OPBs. Since Leishmania is known to secrete OPB, we performed in vitro infection assays using the recombinant enzyme. Our results showed that active OPB increased in vitro infection by L. (L.) amazonensis when present before and throughout infection. Our findings suggest that OPB is relevant to L. (L.) amazonensis infection, and that potential drugs acting through OPB will probably be effective for Old and New World Leishmania species. OPB inhibitors may eventually be explored for leishmaniasis chemotherapy.

Making the Most of Its Short Reads: A Bioinformatics Workflow for Analysing the Short-Read-Only Data of Leishmania orientalis (Formerly Named Leishmania siamensis) Isolate PCM2 in Thailand

Simple Summary

Leishmaniasis is a parasitic disease caused by flagellated protozoa of the genus Leishmania. Multiple genome sequencing platforms have been employed to complete Leishmania genomes at the expense of high cost. This study proposes an integrative bioinformatic workflow for assembling only the short-read data of Leishmania orientalis isolate PCM2 from Thailand and produce an acceptable-quality genome for further genomic analysis. This workflow gives extensive information required for identifying strain-specific markers and virulence-associated genes useful for drug and vaccine development before a more exhaustive and expensive investigation.

Abstract

Background: Leishmania orientalis (formerly named Leishmania siamensis) has been neglected for years in Thailand. The genomic study of L. orientalis has gained much attention recently after the release of the first high-quality reference genome of the isolate LSCM4. The integrative approach of multiple sequencing platforms for whole-genome sequencing has proven effective at the expense of considerably expensive costs. This study presents a preliminary bioinformatic workflow including the use of multi-step de novo assembly coupled with the reference-based assembly method to produce high-quality genomic drafts from the short-read Illumina sequence data of L. orientalis isolate PCM2. Results: The integrating multi-step de novo assembly by MEGAHIT and SPAdes with the reference-based method using the L. enriettii genome and salvaging the unmapped reads resulted in the 30.27 Mb genomic draft of L. orientalis isolate PCM2 with 3367 contigs and 8887 predicted genes. The results from the integrated approach showed the best integrity, coverage, and contig alignment when compared to the genome of L. orientalis isolate LSCM4 collected from the northern province of Thailand. Similar patterns of gene ratios and frequency were observed from the GO biological process annotation. Fifty GO terms were assigned to the assembled genomes, and 23 of these (accounting for 61.6% of the annotated genes) showed higher gene counts and ratios when results from our workflow were compared to those of the LSCM4 isolate. Conclusions: These results indicated that our proposed bioinformatic workflow produced an acceptable-quality genome of L. orientalis strain PCM2 for functional genomic analysis, maximising the usage of the short-read data. This workflow would give extensive information required for identifying strain-specific markers and virulence-associated genes useful for drug and vaccine development before a more exhaustive and expensive investigation.

First report of Leishmania RNA virus 1 in Leishmania (Viannia) braziliensis clinical isolates from Rio de Janeiro State - Brazil

BACKGROUND

Leishmania parasites carry a double-stranded RNA virus (Leishmania RNA virus - LRV) that has been divided in LRV1 and LRV2.

OBJECTIVES

Leishmania (Viannia) braziliensis clinical isolates were assessed in order to determine LRV presence.

METHODS

Two-round polymerase chain reaction (PCR and nested PCR) was performed to detect LRV1 or LRV2 in L. (V.) braziliensis clinical isolates (n = 12).

FINDINGS

LRV1 was detected in three clinical isolates which was phylogenetically related to other sequences reported from other American tegumentary leishmaniasis (ATL) endemic areas of Brazil. Patients infected with L. (V.) braziliensis LRV-negative showed only cutaneous lesions while LRV-positive reported different manifestations.

MAIN CONCLUSION

Data presented here show for the first time that LRV1 is circulating in L. (V.) braziliensis clinical isolates from Rio de Janeiro State in Brazil.

Virulence factors of Leishmania parasite: Their paramount importance in unraveling novel vaccine candidates and therapeutic targets

Leishmaniasis is a neglected tropical disease and remains a global concern for healthcare. It is caused by an opportunistic protozoan parasite belonging to the genus Leishmania and affects millions worldwide. This disease is mainly prevalent in tropical and subtropical regions and is associated with a high risk of public morbidity and mortality if left untreated. Transmission of this deadly disease is aggravated by the bite of female sand-fly vectors (Phlebotomus and Lutzomyia). With time, significant advancement in leishmaniasis-related research has been carried out to cope with the disease burden. Still, the Leishmania parasite has also co-evolved with its host and adapted successfully within the host's lethal milieu/environment. Thus, understanding and knowledge of various leishmanial virulence factors responsible for the parasitic infection are essential for exploring drug targets and vaccine candidates. The present review elucidates the importance of virulence factors in pathogenesis and summarizes the major leishmanial virulence molecules contributing to the parasitic infection during host-pathogen interaction. Furthermore, we have also elaborated on the potential contribution of leishmanial virulence proteins in developing vaccine candidates and exploring novel therapeutics against this parasitic disease. We aim to represent a clearer picture of parasite pathogenesis within the human host that can further aid in unraveling new strategies to fight against the deadly infection of leishmaniasis.

Discovery of Leishmania Druggable Serine Proteases by Activity-Based Protein Profiling

Leishmaniasis are a group of diseases caused by parasitic protozoa of the genus Leishmania. Current treatments are limited by difficult administration, high cost, poor efficacy, toxicity, and growing resistance. New agents, with new mechanisms of action, are urgently needed to treat the disease. Although extensively studied in other organisms, serine proteases (SPs) have not been widely explored as antileishmanial drug targets. Herein, we report for the first time an activity-based protein profiling (ABPP) strategy to investigate new therapeutic targets within the SPs of the Leishmania parasites. Active-site directed fluorophosphonate probes (rhodamine and biotin-conjugated) were used for the detection and identification of active Leishmania serine hydrolases (SHs). Significant differences were observed in the SHs expression levels throughout the Leishmania life cycle and between different Leishmania species. Using iTRAQ-labelling-based quantitative proteomic mass spectrometry, we identified two targetable SPs in Leishmania mexicana: carboxypeptidase LmxM.18.0450 and prolyl oligopeptidase LmxM.36.6750. Druggability was ascertained by selective inhibition using the commercial serine protease inhibitors chymostatin, lactacystin and ZPP, which represent templates for future anti-leishmanial drug discovery programs. Collectively, the use of ABPP method complements existing genetic methods for target identification and validation in Leishmania.

Elevated baseline expression of seven virulence factor RNA transcripts in visceralizing species of Leishmania: a preliminary quantitative PCR study

Introduction:

Leishmaniasis is a neglected tropical disease that manifests as three major disease phenotypes: cutaneous, mucocutaneous, and visceral. In this preliminary study, we quantified virulence factor (VF) RNA transcript expression in Leishmania species, stratified by geographic origin and propensity for specific disease phenotypes.

Methods:

Cultured promastigotes of 19 Leishmania clinical and ATCC isolates were extracted for total cellular RNA, cDNA was reverse transcribed, and qPCR assays were performed to quantify VF RNA transcript expression for hsp23, hsp70, hsp83, hsp100, mpi, cpb, and gp63.

Results:

Comparison of visceralizing species (Leishmania donovani, Leishmania chagasi, and Leishmania infantum) versus non-visceralizing species [Leishmania (Viannia) spp., Leishmania tropica, Leishmania major, Leishmania mexicana, and Leishmania amazonensis] revealed a significantly greater pooled transcript expression for visceralizing species (p = 0.0032). Similarly, Old World species demonstrated significantly higher VF RNA transcript expression than New World species (p = 0.0015). On a per-gene basis, species with a propensity to visceralize ubiquitously expressed higher levels of gp63 (p = 0.005), cpb (p = 0.0032), mpi (p = 0.0032), hsp23 (p = 0.0039), hsp70 (p = 0.0032), hsp83 (p = 0.0032), and hsp100 (p = 0.0032).

Conclusion:

Here, we provide quantitative, preliminary evidence of elevated VF RNA transcript expression driven largely by the visceralizing causative species of Leishmania. This work highlights the extensive heterogeneity in pathogenicity mechanisms between Leishmania species, which may partly underpin the fatal progression of visceral leishmaniasis.

Genome Assembly and Genome Annotation of Leishmania martiniquensis Isolated from a Leishmaniasis Patient in Thailand

Leishmaniasis is a parasitic disease caused by Leishmania spp. with worldwide distribution. Autochthonous leishmaniasis has been reported to result from the infection by Leishmania martiniquensis in Thailand. This species was isolated in culture and subjected to high-throughput whole-genome sequencing. A total of 30.8 Mb in 36 chromosomes of the whole genome was assembled, annotated, and characterized. The L. martiniquensis under study was shown to segregate into the same clade and thus closely related to the previously identified L. martiniquensis (LU_Lmar_1.0), as determined by phylogenetic analysis of their genomic sequences along with those of representative kinetoplastid species. The total number of open reading frames genomewide predicts 8,209 protein-coding genes, of which 359 are putative virulence factors, including two previously known, e.g., cysteine proteinase C and superoxide dismutase B1. The results obtained from this study will be useful for further annotation and comparison with other Leishmania martiniquensis in the future.

Mutation Characteristics and Phylogenetic Analysis of Five Leishmania Clinical Isolates

Simple Summary

Leishmaniasis, a neglected tropical disease, is caused by infection with the Leishmania species, threatening millions of people in approximately 100 endemic countries. The emergence of antimony-resistant Leishmania strains have brought difficulties to the treatment and elimination of leishmaniasis. This study performed genome-wide resequencing and phylogenetic analysis of five isolates from the Leishmania donovani complex, focusing on finding mutations related to antimony resistance and virulence of the newly isolated Leishmania strain L_HCZ in 2016. By combining whole-genome sequencing and whole-genome phylogenetic analysis, Leishmania isolates L_801, L_9044 and L_Liu were identified as Leishmania donovani, and L_HCZ as Leishmania infantum. By discovering genome-wide single-nucleotide polymorphisms and structural variations, we identified mutations of drug resistance-related genes in the antimony-resistant Leishmania isolate L_HCZ. The new Leishmania isolate L_HCZ has strong virulence and strong drug resistance, which should be taken seriously by the relevant health departments and scientific researchers.

Abstract

Leishmaniasis is a neglected tropical disease threatening millions of people worldwide. The emergence of antimony-resistant Leishmania strains have brought difficulties to the treatment and elimination of leishmaniasis. This study performed genome sequencing, phylogenetic analysis and mutation analysis of five Leishmania clinical isolates, especially the Leishmania strain L_HCZ isolated in 2016, which shows strong virulence and antimony resistance. By phylogenetic analysis, four isolates (L_DD8, L_801, L_Liu and L_9044) were identified as Leishmania donovani, the isolate L_HCZ was identified as Leishmania infantum and the isolate L_DD8 as a standard strain of L.donovani. Genome-wide mutation analysis was applied to identify mutations related to the drug resistance and virulence of the newly isolated L_HCZ. Compared with the other four Leishmania isolates, L_HCZ had the most mutations in genes associated with antimony resistance, including the ABC transporter, ascorbate-dependent peroxidase, gamma–glutamylcysteine synthetase, glucose-6-phosphate 1-dehydrogenase, ATP-binding cassette protein subfamily A and multi-drug resistance protein-like genes. Among the genes associated with virulence, L_HCZ had the most mutations in cysteine peptidase A, cysteine peptidase B, cysteine peptidase C, heat-shock protein 70, gp63, acid phosphatase, kinesin k39, kinesin, phosphoglycan beta 1, amastin-like surface protein and amastin-like proteins. The mutations in L_HCZ might possibly contribute to its antimony resistance and strong virulence in clinical patients. Whole-genome resequencing has exhibited broad application prospects and may be put into clinical use in the future for parasite identifying and epidemiological investigations.

Potential molecular targets of Leishmania pathways in developing novel antileishmanials

The illness known as leishmaniasis has not become a household name like malaria, although it stands as the second-largest parasitic disease, surpassed only by malaria. As no licensed vaccine is available, treatment for leishmaniasis mostly relies on chemotherapy. Inefficiency and drug resistance are the major impediments in current therapeutics. In this scenario, identification of novel molecular drug candidates is indispensable to develop robust antileishmanials. The exploration of structure-based drugs to target enzymes/molecules of Leishmania which differ structurally/functionally from their equivalents in mammalian hosts not only helps in developing a new class of antileishmanials, but also paves the way to understand Leishmania biology. This review provides a comprehensive overview on possible drug candidates relating to various Leishmania molecular pathways.

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

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

Leishmania tarentolae novel responses to Bi3+-doped strontium aluminum oxyfluorides

Novel therapeutics for the treatment of leishmaniasis are of interest as the disease not only is becoming more prevalent, but drug resistance is increasing in certain regions of the world. Reported here is the use of Bi3+-doped strontium aluminum oxyfluoride phosphors and protease inhibitors to test in vitro inhibitory activity against cultured promastigote Leishmania tarentolae and effects on L. tarentolae secreted acid phosphatase (SAP) activity. Cell viability did not significantly decrease in the presence of 50 μM anti-perovskite compounds, implying limited cytotoxicity. Yet SAP activity did increase in the cell free preparations with time in the presence of strontium compounds. Of interest was the observation that cell free SAP activity did not increase in the presence of protease inhibitors with or without added strontium compounds. Since secreted proteases may play a role in the maturation of Leishmania SAP and thus be involved with parasite-host infection establishment, this is in further need of evaluation. Nitric oxide production on day 4 post-addition of the strontium compounds was evaluated and showed an approximately 50% decrease in NO production in the presence of two test compounds relative to DMSO control cells. This is the first report of anti-perovskite compound inhibition of NO production by Leishmania.

Inhibition of bacterial and human zinc-metalloproteases by bisphosphonate- and catechol-containing compounds

Compounds containg catechol or bisphosphonate were tested as inhibitors of the zinc metalloproteases, thermolysin (TLN), pseudolysin (PLN) and aureolysin (ALN) which are bacterial virulence factors, and the human matrix metalloproteases MMP-9 and -14. Inhibition of virulence is a putative strategy in the development of antibacterial drugs, but the inhibitors should not interfere with human enzymes. Docking indicated that the inhibitors bound MMP-9 and MMP-14 with the phenyl, biphenyl, chlorophenyl, nitrophenyl or methoxyphenyl ringsystem in the S₁'-subpocket, while these ringsystems entered the S₂'- or S₁ -subpockets or a region involving amino acids in the S₁'- and S₂'-subpockets of the bacterial enzymes. An arginine conserved among the bacterial enzymes seemed to hinder entrance deeply into the S₁'-subpocket. Only the bisphosphonate containing compound RC2 bound stronger to PLN and TLN than to MMP-9 and MMP-14. Docking indicated that the reason was that the conserved arginine (R203 in TLN and R198 in PLN) interacts with phosphate groups of RC2.

Cysteine proteases: Battling pathogenic parasitic protozoans with omnipresent enzymes

Millions of people worldwide lie at the risk of parasitic protozoic infections that kill over a million people each year. The rising inefficacy of conventional therapeutics to combat these diseases, mainly due to the development of drug resistance to a handful of available licensed options contributes substantially to the rising burden of these ailments. Cysteine proteases are omnipresent enzymes that are critically implicated in the pathogenesis of protozoic infections. Despite their significance and druggability, cysteine proteases as therapeutic targets have not yet been translated into the clinic. The review presents the significance of cysteine proteases of members of the genera Plasmodium, Entamoeba, and Leishmania, known to cause Malaria, Amoebiasis, and Leishmaniasis, respectively, the protozoic diseases with the highest morbidity and mortality. Further, projecting them as targets for molecular tools like the CRISPR-Cas technology for favorable manipulation, exploration of obscure genomes, and achieving a better insight into protozoic functioning. Overcoming the hurdles that prevent us from gaining a better insight into the functioning of these enzymes in protozoic systems is a necessity. Managing the burden of parasitic protozoic infections pivotally depends upon the betterment of molecular tools and therapeutic concepts that will pave the path to an array of diagnostic and therapeutic applications.

Novel coumarin-isatin hybrids as potent antileishmanial agents: Synthesis, in silico and in vitro evaluations

Leishmaniasis being one of the six major tropical diseases that affects nearly 0.7-1.3 million people annually, has so far limited and high toxic therapeutic options. Herein, we report the synthesis, in silico, and in vitro evaluations of novel coumarin-incorporated isatin hydrazones (Spf-1 - Spf-10) as highly potent and safe antileishmanial agents. Molecular docking was initially carried out to decipher the binding confirmation of lead molecules towards the active cavity of the target protein (Leishmanolysin gp63) of Leishmania tropica. Among all the docked compounds, only Spf-6, Spf-8, and Spf-10 showed high binding affinities due to a pattern of strong conventional hydrogen bonds and hydrophobic π-interactions. The molecular dynamics simulations showed the stable pattern of such bonding and structure-based confirmation with a time scale of 50 ns towards the top compound (Spf-10) and protein. These analyses affirmed the high stability of the system. Three out of ten compounds evaluated for their antileishmanial activity against Leishmania tropica promastigotes and amastigotes were found to be active at micromolar concentrations (IC₅₀ range 0.1-4.13 μmol/L), and most importantly, they were also found to be highly biocompatible when screened for their toxicity in human erythrocytes.

Insights into Leishmania Molecules and Their Potential Contribution to the Virulence of the Parasite

Neglected parasitic diseases affect millions of people worldwide, resulting in high morbidity and mortality. Among other parasitic diseases, leishmaniasis remains an important public health problem caused by the protozoa of the genus Leishmania, transmitted by the bite of the female sand fly. The disease has also been linked to tropical and subtropical regions, in addition to being an endemic disease in many areas around the world, including the Mediterranean basin and South America. Although recent years have witnessed marked advances in Leishmania-related research in various directions, many issues have yet to be elucidated. The intention of the present review is to give an overview of the major virulence factors contributing to the pathogenicity of the parasite. We aimed to provide a concise picture of the factors influencing the reaction of the parasite in its host that might help to develop novel chemotherapeutic and vaccine strategies.

Evaluation of Cysteine Protease C of Leishmania donovani in Comparison with Glycoprotein 63 and Elongation Factor 1α for Diagnosis of Human Visceral Leishmaniasis and for Posttreatment Follow-Up Response

Visceral leishmaniasis (VL) is a threat in many developing countries. Much effort has been put to eliminating this disease, for which serodiagnosis remains the mainstay for VL control programs. New and improved antigens as diagnostic candidates are required, though, as the available antigens fail to demonstrate equal optimum performance in all areas of endemicity. Moreover, these diagnoses are dependent on invasive serum sampling. In the current study, we cloned and expressed Leishmania donovani cysteine protease C (CPC) and evaluated its diagnostic and test-of-cure possibilities by detecting the antibody levels in human serum and urine through ELISA and immunoblot assays. Two immunodominant antigens, recombinant glycoprotein 63 (GP63) and elongation factor 1α (EF1α), identified earlier by our group, were also assessed by employing human serum and urine samples. Of these three antigens in ELISAs, CPC demonstrated the highest sensitivities of 98.15% and 96% positive testing in serum and urine of VL patients, respectively. Moreover, CPC yielded 100% specificity with serum and urine of nonendemic healthy controls compared to GP63 and EF1α. Urine samples were found to be more specific than serum for distinguishing endemic healthy controls and other diseases by means of all three antigens. In all cases, CPC gave the most promising results. Unlike serum, urine tests demonstrated a significant decrease in antibody levels for CPC, GP63, and EF1α after 6 months of treatment. The diagnostic and test-of-cure performances of CPC in the immunoblot assay were found to be better than those of GP63 and EF1α. In conclusion, CPC, followed by GP63 and EF1α, may be utilized as candidates for diagnosis of VL and to assess treatment response.

Detection of Metalloproteases and Cysteine Proteases RNA Transcripts of Leishmania (Leishmania) infantum in Ear Edge Skin of Naturally Infected Dogs

Leishmania spp. proteases have been proposed as virulence factors contributing to adaptive success these parasites to the mammalian hosts. Since these enzymes are poorly studied in naturally infected dogs, this work aims to show the differences in metalloprotease and cysteine proteases gene expression in ear edge skin of dogs naturally infected by Leishmania (Leishmania) infantum. A cohort of dogs (n = 20) naturally infected by L. (L.) infantum was clinically classified as asymptomatic, oligosymptomatic, and polysymptomatic and the parasite load range estimated. The analysis of proteases expression by RT-PCR in the ear edge skin was also assessed, suggesting more transcripts of proteases in cDNA samples from polysymptomatic dogs than oligosymptomatic and asymptomatic ones. Metalloprotease RT-PCR assays yielded products (202 bp) in all assessed cDNA dog samples. In contrast, cysteine proteases transcripts (227 bp) had shown to be better detected in cDNA samples of polysymptomatic dogs, compared with cDNA samples from asymptomatic and oligosymptomatic dogs. Predictive in silico assays suggested that secondary structures of metalloproteasee mRNAs can be more stable than cysteine proteases at the skin temperature of dogs. Evidence is presented that during natural infection of dogs by L. (L.) infantum, this parasite produces transcripts of metalloprotease and cysteine protease RNA in the skin from asymptomatic, oligosymptomatic, and polysymptomatic dogs.

Reactivity of sera from dogs living in a leishmaniasis-endemic area to the COOH-terminal region of cysteine proteinase B

Cysteine proteinases are well-known virulence factors of Leishmania spp. with demonstrated actions in both experimental mouse infection and human infection. However, studies on these enzymes in canine leishmaniasis are scarce. Here, we show, for the first time, the reactivity of sera from dogs living in an endemic area to a recombinant protein from the COOH-terminal region of cysteine B protease. In this work, enzyme-linked immunosorbent assays were performed using a 14kDa rcyspep protein obtained through a pET28-a expression system in Escherichia coli. First, 96-well plates were coated with rcyspep (500ng/well) and incubated with sera from dogs (1:100). Subsequently, IgG antibody detection was performed using rabbit anti-dog IgG antibodies conjugated with peroxidase. Sera from dogs (n=114), including suspect (n=30) and positive (n=50) dogs from a leishmaniasis-endemic area and dogs from a nonendemic area, (n=34), negative for leishmaniasis, were assessed. The results showed that sera from the suspect (42%) and positive (68%) groups responded differently to the antigen titers tested above the cut-off (Optical Density=0.166). This finding suggests that the immune response detected against cyspep may be related to clinical disorders present in these animals. Collectively, the data gathered here suggest that cyspep can sensitize the immune systems of dogs from a leishmaniasis-endemic area to elicit a humoral response, an immunological parameter indicating the contribution of this protein in host-parasite interaction.

A Review of Quercus infectoria (Olivier) Galls as a Resource for Anti-parasitic Agents: In Vitro and In Vivo Studies

Parasitic diseases represent one of the causes for significant global economic, environmental and public health impacts. The efficacy of currently available anti-parasitic drugs has been threatened by the emergence of single drug- or multidrug-resistant parasite populations, vector threats and high cost of drug development. Therefore, the discovery of more potent anti-parasitic drugs coming from medicinal plants such as Quercus infectoria is seen as a major approach to tackle the problem. A systematic review was conducted to assess the efficacy of Q. infectoria in treating parasitic diseases both in vitro and in vivo due to the lack of such reviews on the anti-parasitic activities of this plant. This review consisted of intensive searches from three databases including PubMed, Science Direct and Scopus. Articles were selected throughout the years, limited to English language and fully documented. A total of 454 potential articles were identified, but only four articles were accepted to be evaluated based on inclusion and exclusion criteria. Although there were insufficient pieces of evidence to account for the efficacy of Q. infectoria against the parasites, this plant appears to have anti-leishmanial, anti-blastocystis and anti-amoebic activities. More studies in vitro and in vivo are warranted to further validate the anti-parasitic efficacy of Q. infectoria.

Protective or Detrimental? Understanding the Role of Host Immunity in Leishmaniasis

The intracellular protozoan parasites of the genus Leishmania are the causative agents of leishmaniasis, a vector-borne disease of major public health concern, estimated to affect 12 million people worldwide. The clinical manifestations of leishmaniasis are highly variable and can range from self-healing localized cutaneous lesions to life-threatening disseminated visceral disease. Once introduced into the skin by infected sandflies, Leishmania parasites interact with a variety of immune cells, such as neutrophils, monocytes, dendritic cells (DCs), and macrophages. The resolution of infection requires a finely tuned interplay between innate and adaptive immune cells, culminating with the activation of microbicidal functions and parasite clearance within host cells. However, several factors derived from the host, insect vector, and Leishmania spp., including the presence of a double-stranded RNA virus (LRV), can modulate the host immunity and influence the disease outcome. In this review, we discuss the immune mechanisms underlying the main forms of leishmaniasis, some of the factors involved with the establishment of infection and disease severity, and potential approaches for vaccine and drug development focused on host immunity.

Exploring Leishmania infantum cathepsin as a new molecular marker for phylogenetic relationships and visceral leishmaniasis diagnosis

Background

Leishmania infantum, the etiological agent of visceral leishmaniasis, is a neglected zoonosis that requires validation and standardization of satisfactory diagnostic methodologies. Thus, the aim of the present study was to evaluate the effectiveness of cathepsin L-like protease as a target for making molecular diagnoses and as a phylogenetic marker enabling to understand the intraspecies variations and evolutionary history of L. infantum in Brazil.

Methods

We used 44 isolates of L. infantum. The cathepsin L-like gene fragments were amplified, sequenced, manually aligned and analyzed using inference methods. The sequences generated were used to search and design oligonucleotide primers to be used in reactions specific to the target parasite.

Results

The cathepsin L-like gene did not show any intraspecies variability among the isolates analyzed. The pair of primers proposed amplified the target deoxyribonucleic acid (DNA) of L. infantum isolates and were effective for DNA amplification at concentrations of as low as 10^− 11 ng/μl. The proposed marker did not present cross-reactions with other hemoparasites. When used for making the diagnosis in a panel of clinical samples from dogs, a positivity rate of 49.03% (102/208) was obtained, versus 14.42% (30/208) for a ribosomal internal transcribed spacer (ITS) marker. In samples from sandflies, the rate was 6.25% and from humans, 14.28%.

Conclusions

The results described in this work allow us to infer that CatLeish-PCR is a sensitive and specific marker for use in diagnostic trials of L. infantum and in clinical and epidemiological surveys.

Quantitative secretome analysis unravels new secreted proteins in Amphotericin B resistant Leishmania donovani

Leishmaniasis is second most neglected disease after malaria and seems to be a worldwide concern because of increased drug resistance and non-availability of approved vaccine. The underlying molecular mechanism of drug resistance (Amp B) in Leishmania parasites still remains elusive. Herein, the present study investigated differentially expressed secreted proteins of Amphotericin B sensitive (S) and resistant (R) isolate of Leishmania donovani by using label free quantitative LC-MS/MS approach. A total of 406 differentially expressed secreted proteins were found between sensitive (S) and resistant (R) isolate. Among 406 proteins, 32 were significantly up regulated (>2.0 fold) while 22 were down regulated (<0.5 fold) in resistant isolate of L. donovani. Further, differentially expressed proteins were classified into 11 various biological processes. Interestingly, identified up regulated proteins in resistant parasites were dominated in carbohydrate metabolism, stress response, transporters and proteolysis. Western blot and enzymatic activity of identified proteins validate our proteomic findings. Finally, our study demonstrated some new secreted proteins associated with Amp B resistance which provides a basis for further investigations to understand the role of proteins in L. donovani. BIOLOGICAL SIGNIFICANCE: Although great advances have been achieved in the diagnosis and treatment of leishmaniasis, still drug resistance is major hurdle in control of disease. Present study will enhance the deeper understanding of altered metabolic pathways involved in Amp B resistance mechanism and provide possible new proteins which can be potential candidate either for exploring as new drug target or vaccine. Protein-protein interactions highlighted the up-regulated metabolic pathways in resistant parasites which further unravel the adaptive mechanism of parasites.

Virulence factor RNA transcript expression in the Leishmania Viannia subgenus: influence of species, isolate source, and Leishmania RNA virus-1

BACKGROUND

Leishmania RNA virus-1 (LRV1) is a double-stranded RNA virus identified in 20-25% of Viannia-species endemic to Latin America, and is believed to accelerate cutaneous to mucosal leishmaniasis over time. Our objective was to quantify known virulence factor (VF) RNA transcript expression according to LRV1 status, causative species, and isolate source.

METHODS

Eight cultured isolates of Leishmania were used, four of which were LRV1-positive (Leishmania Viannia braziliensis [n = 1], L. (V.) guyanensis [n = 1], L. (V.) panamensis [n = 2]), and four were LRV1-negative (L. (V.) panamensis [n = 3], L. (V.) braziliensis [n = 1]). Promastigotes were inoculated into macrophage cultures, and harvested at 24 and 48 h. RNA transcript expression of hsp23, hsp70, hsp90, hsp100, mpi, cpb, and gp63 were quantified by qPCR.

RESULTS

RNA transcript expression of hsp100 (p = 0.012), cpb (p = 0.016), and mpi (p = 0.022) showed significant increases from baseline pure culture expression to 24- and 48-h post-macrophage infection, whereas hsp70 (p = 0.004) was significantly decreased. A trend toward increased transcript expression of hsp100 at baseline in isolates of L. (V.) panamensis was noted. Pooled VF RNA transcript expression by L. (V.) panamensis isolates was lower than that of L. (V.) braziliensis and L. (V.) guyananesis at 24 h (p = 0.03). VF RNA transcript expression did not differ by LRV1 status, or source of cultured isolate at baseline, 24, or 48 h; however, a trend toward increased VF RNA transcript expression of 2.71- and 1.93-fold change of mpi (p = 0.11) and hsp90 (p = 0.11), respectively, in LRV1 negative isolates was noted. Similarly, a trend toward lower levels of overall VF RNA transcript expression in clinical isolates (1.15-fold change) compared to ATCC® strains at 24 h was noted (p = 0.07).

CONCLUSIONS

Our findings suggest that known VF RNA transcript expression may be affected by the process of macrophage infection. We were unable to demonstrate definitively that LRV-1 presence affected VF RNA transcript expression in the species and isolates studied. L. (V.) guyanensis and L. (V.) braziliensis demonstrated higher pooled VF RNA transcript expression than L. (V.) panamensis; however, further analyses of protein expression to corroborate this finding are warranted.

Dipeptidyl nitrile derivatives have cytostatic effects against Leishmania spp. promastigotes

Cysteine proteases are involved in critical cell processes to the protozoa from Leishmania genus, and their inhibition is a therapeutic alternative to treat the disease. In this work, derivatives of dipeptidyl nitriles acting as reversible covalent inhibitors of cysteine proteases were studied as cytostatic agents. The proteolytic activity inside the living and lysed parasite cells was quantified using a selective substrate for cysteine proteases (Z-FR-MCA) from Leishmania amazonensis and L. infantum. The overall proteolytic activity of intact cells and even cell extracts was only marginally affected at high concentrations, with the observation of cytostatic activity and cell cycle arrest of promastigotes. However, the cytotoxic effects were only observed for infected J774 macrophages, which impaired further analysis of the amastigote infection. Therefore, the proteolytic inhibition in intact L. amazonensis and L. infantum promastigotes had no relationship to the cytostatic activity, which emphasizes that these dipeptidyl nitriles act through another mechanism of action.

Insights into the tracking of the cysteine proteinase B COOH-terminal polypeptide of Leishmania (Leishmania) amazonensis by surface plasmon resonance

Leishmania (Leishmania) amazonensis has adaptive mechanisms to the host environment that are guided by its proteinases, including cysteine proteinase B (CPB), and primarily its COOH-terminal region (Cyspep). This work aimed to track the fate of Cyspep by surface plasmon resonance (SPR) of promastigotes and amastigotes to gain a greater understanding of the adaptation of this parasite in both hosts. This strategy consisted of antibody immobilization on a COOH1 surface, followed by interaction with parasite proteins and epoxysuccinyl-L-leucylamido(4-guanidino)butane (E-64). Pro-CPB and Cyspep were detected using specific polyclonal antibodies against a recombinant Cyspep in both parasite forms. The parasitic supernatants from amastigotes and promastigotes exhibited higher anti-Cyspep recognition compared with that in the subcellular fractions. As the supernatant of the promastigote cultures exhibited resonance unit values indicative of an effective with to E-64, this result was assumed to be Pro-CPB detection. Finally, after using three sequential SPR assay steps, we propose that amastigotes and promastigotes release Cyspep into the extracellular environment, but only promastigotes release this polypeptide as Pro-CPB.

Serine Proteinases in Leishmania (Viannia) braziliensis Promastigotes Have Distinct Subcellular Distributions and Expression

Serine proteinases in Leishmania (Viannia) braziliensis promastigotes were assessed in this work. This study included the investigation of the enzymatic activity of subcellular fractions obtained from benzamidine affinity chromatography, reverse transcription polymerase chain reactions, and in silico assays of subcellular localization of subtilisin. Promastigote serine proteinases showed gelatinolytic activity with molecular masses of 43 kDa to 170 kDa in the cytosolic fraction and 67 kDa to 170 kDa in the membranous fraction. Serine proteinase activities were detected using N-benzyloxycarbonyl-l-phenylalanyl-l-arginine 7-amino-4-methylcoumarin (Z-FR-AMC) and N-succinyl-l-alanine-l-phenylalanine-l-lysine 7-amino-4-methylcoumarin (Suc-AFK-AMC) as substrates in the cytosolic fraction (Z-FR-AMC = 392 ± 30 µmol.min⁻¹ mg of protein⁻¹ and Suc-AFK-AMC = 252 ± 20 µmol.min⁻¹ mg of protein⁻¹) and in the membranous fraction (Z-FR-AMC = 53 ± 5 µmol.min⁻¹ mg of protein⁻¹ and Suc-AFK-AMC = 63.6 ± 6.5 µmol.min⁻¹ mg of protein⁻¹). Enzyme specificity was shown by inhibition with aprotinin (19% to 80% inhibition) and phenylmethanesulfonyl fluoride (3% to 69%), depending on the subcellular fraction and substrate. The expression of subtilisin (LbrM.13.0860 and LbrM.28.2570) and tryparedoxin peroxidase (LbrM.15.1080) genes was observed by the detection of RNA transcripts 200 bp, 162 bp, and 166 bp long, respectively. Subsequent in silico assays showed LbrM.13.0860 can be located in the cytosol and LbrM.28.2570 in the membrane of the parasite. Data obtained here show the subcellular distribution and expression of serine proteinases, including the subtilisin-like serine proteinases in L. (V.) braziliensis promastigotes.

Comparative transcriptomics in Leishmania braziliensis: disclosing differential gene expression of coding and putative noncoding RNAs across developmental stages

Leishmaniasis is a worldwide public health problem caused by protozoan parasites of the genus Leishmania. Leishmania braziliensis is the most important species responsible for tegumentary leishmaniases in Brazil. An understanding of the molecular mechanisms underlying the success of this parasite is urgently needed. An in-depth study on the modulation of gene expression across the life cycle stages of L. braziliensis covering coding and noncoding RNAs (ncRNAs) was missing and is presented herein. Analyses of differentially expressed (DE) genes revealed that most prominent differences were observed between the transcriptomes of insect and mammalian proliferative forms (6,576 genes). Gene ontology (GO) analysis indicated stage-specific enriched biological processes. A computational pipeline and 5 ncRNA predictors allowed the identification of 11,372 putative ncRNAs. Most of the DE ncRNAs were found between the transcriptomes of insect and mammalian proliferative stages (38%). Of the DE ncRNAs, 295 were DE in all three stages and displayed a wide range of lengths, chromosomal distributions and locations; many of them had a distinct expression profile compared to that of their protein-coding neighbors. Thirty-five putative ncRNAs were submitted to northern blotting analysis, and one or more hybridization-positive signals were observed in 22 of these ncRNAs. This work presents an overview of the L. braziliensis transcriptome and its adjustments throughout development. In addition to determining the general features of the transcriptome at each life stage and the profile of protein-coding transcripts, we identified and characterized a variety of noncoding transcripts. The novel putative ncRNAs uncovered in L. braziliensis might be regulatory elements to be further investigated.

In silico characterization of multiple genes encoding the GP63 virulence protein from Leishmania braziliensis: identification of sources of variation and putative roles in immune evasion

Background

The leishmaniasis are parasitic diseases caused by protozoans of the genus Leishmania, highly divergent eukaryotes, characterized by unique biological features. To survive in both the mammalian hosts and insect vectors, these pathogens make use of a number of mechanisms, many of which are associated with parasite specific proteases. The metalloprotease GP63, the major Leishmania surface antigen, has been found to have multiple functions required for the parasite’s survival. GP63 is encoded by multiple genes and their copy numbers vary considerably between different species and are increased in those from the subgenus Viannia, including L. braziliensis.

Results

By comparing multiple sequences from Leishmania and related organisms this study sought to characterize paralogs in silico, evaluating their differences and similarities and the implications for the GP63 function. The Leishmania GP63 genes are encoded on chromosomes 10, 28 and 31, with the genes from the latter two chromosomes more related to genes found in insect or plant parasites. Those from chromosome 10 have experienced independent expansions in numbers in Leishmania, especially in L. braziliensis. These could be clustered in three groups associated with different mRNA 3′ untranslated regions as well as distinct C-terminal ends for the encoded proteins, with presumably distinct expression patterns and subcellular localizations. Sequence variations between the chromosome 10 genes were linked to intragenic recombination events, mapped to the external surface of the proteins and predicted to be immunogenic, implying a role against the host immune response.

Conclusions

Our results suggest a greater role for the sequence variation found among the chromosome 10 GP63 genes, possibly related to the pathogenesis of L. braziliensis and closely related species within the mammalian host. They also indicate different functions associated to genes mapped to different chromosomes. For the chromosome 10 genes, variable subcellular localizations were found to be most likely associated with multiple functions and target substrates for this versatile protease.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5465-z) contains supplementary material, which is available to authorized users.

The selectivity of galardin and an azasugar-based hydroxamate compound for human matrix metalloproteases and bacterial metalloproteases

Inhibitors targeting bacterial enzymes should not interfere with enzymes of the host, and knowledge about structural determinants for selectivity is important for designing inhibitors with a therapeutic potential. We have determined the binding strengths of two hydroxamate compounds, galardin and compound 1b for the bacterial zinc metalloproteases, thermolysin, pseudolysin and auerolysin, known to be bacterial virulence factors, and the two human zinc metalloproteases MMP-9 and MMP-14. The active sites of the bacterial and human enzymes have huge similarities. In addition, we also studied the enzyme-inhibitor interactions by molecular modelling. The obtained Ki values of galardin for MMP-9 and MMP-14 and compound 1b for MMP-9 are approximately ten times lower than previously reported. Compound 1b binds stronger than galardin to both MMP-9 and MMP-14, and docking studies indicated that the diphenyl ether moiety of compound 1b obtains more favourable interactions within the S´1-subpocket than the 4-methylpentanoyl moiety of galardin. Both compounds bind stronger to MMP-9 than to MMP-14, which appears to be due to a larger S´1-subpocket in the former enzyme. Galardin, but not 1b, inhibits the bacterial enzymes, but the galardin Ki values were much larger than for the MMPs. The docking indicates that the S´1-subpockets of the bacterial proteases are too small to accommodate the diphenyl ether moiety of 1b, while the 4-methylpentanoyl moiety of galardin enters the pocket. The present study indicates that the size and shape of the ligand structural moiety entering the S´1-subpocket is an important determinant for selectivity between the studied MMPs and bacterial MPs.