Worldwide risk factors in leishmaniasis

Ecological study measuring the association between conflict, environmental factors, and annual global cutaneous and mucocutaneous leishmaniasis incidence (2005-2022)

BACKGROUND

Cutaneous and mucocutaneous leishmaniasis (CL/ML) cause significant morbidity globally and are vulnerable to changes from environmental events and conflict. In this ecological study, we aim to measure the associations between annual CL/ML cases, conflict intensity, and environmental factors between 2005 and 2022 globally.

METHODS

We pulled annual case data from the WHO for 52 nations that had conflict intensity scores (ranging from 1-10) from the Bertelsmann Transformation Index. Using Earth observation tools, we gathered temperature, precipitation, vegetation, and humidity data, in addition to data on annual estimates of population, internal displacement, and GDP. We fit a negative binomial generalized additive model with a random nation-level intercept.

RESULTS

Conflict was positively associated with increased CL/ML across the studied nations (IRR: 1.09, 95% CI: 1.01-1.16, p = 0.02). Given this, intense conflict (a score of ten) was associated with over double the risk of CL/ML compared to the lowest conflict levels (score of one). We also identified a curvilinear relationship between mean temperature and cases, as well as between vegetation level and cases. Each had small pockets of significant increased and decreased risk, respectively. Larger mean humidity ranges were negatively associated with cases. Importantly, the relationship between conflict intensity and cases was mediated by displacement.

DISCUSSION

Conflict is significantly associated with increased CL/ML cases. This is especially true at higher conflict levels, marking when conflict turns violent. The destruction of critical infrastructure (e.g., that related to healthcare, water, and sanitation) often seen during conflict could drive this association. Such environments can be hospitable to sandflies and can heighten individuals' vulnerability through increased malnutrition, poverty, and displacement. Understanding this relationship is crucial for public health preparedness and response, especially as conflicts become increasingly violent and protracted.

Evaluation of Chemokines MIG and IP-10 as Immunological Biomarkers of Human Visceral Leishmaniasis: A Systematic Review

Visceral leishmaniasis (VL) is a neglected tropical disease that is potentially fatal when untreated. Current diagnostic methods have limitations that contribute to ongoing transmission and poor prognosis. Thus, new tests are needed to provide quick, accurate diagnoses and evaluate clinical progression and treatment efficacy. The monokine induced by interferon-gamma (MIG) and interferon-gamma-inducible protein 10 (IP-10) has been associated with the host susceptibility to VL with potential diagnostic and prognostic purposes. We performed a systematic review using four search databases (Scopus, PubMed, Web of Science, and MEDLINE) to identify studies assessing MIG and IP-10 as potential biomarkers in patients with VL across various clinical conditions. A total of 13 studies were potentially eligible and included in this review. The articles, in general, reveal that the chemokines MIG and IP-10 are elevated in response to infection by Leishmania spp., acting on the host's resistance to the development of the disease. They are associated with asymptomatic conditions and after VL treatment, and this relationship can be observed in both immunocompetent and immunocompromised individuals. Consequently, these chemokines hold relevance in the diagnoses and appropriate management of individuals with VL.

Evaluation of the biodiversity and distribution of sand flies and tracking of Leishmania major in them in central Iran

Many areas of Iran are endemic regarding Cutaneous leishmaniasis (CL) as a parasitic disease transmitted by a female sand fly vector's bite. The present study investigated the distribution of sand flies in Harand and Egieh in Isfahan province, Central Iran. Overall, 408 out of 1260 collected sand flies were identified morphologically, among which 353 and 55 were isolated from Harand and Egieh, respectively. Also, 66.4% and 33.6% of the sand flies were female and male, respectively. The most prevalent sand fly species were Phlebotomus papatasi (52%), followed by Ph. caucasicus (40.4%), Sergentomyia sintoni (4.9%), and Ph. kazeruni (0.7%). Among 180 molecularly-analyzed sand flies, 14 (7.77%) were found infected with L. major, with 9 out of 103 (8.73%) Ph. papatasi and 5 out of 75 (6.66%) Ph. caucasicus.

Mortality due to visceral leishmaniasis in Brazil by municipalities, 2001-2018: a spatial-temporal analysis of estimates from the Global Burden of Disease study

OBJECTIVES

In the American regions, Brazil accounts for 97% of visceral leishmaniasis (VL) cases, with a case fatality rate of approximately 10%. This study aimed to investigate the VL mortality distribution in Brazil and identify high-priority and high-risk areas for intervention strategies.

STUDY DESIGN

This was an ecological study that analysed the spatial-temporal patterns of VL mortality in Brazilian municipalities.

METHODS

Age-standardised VL mortality rates from the Global Burden of Disease study from 2001 to 2018 were used. The distribution of mortality in the municipalities was assessed, and subsequently the Local Index of Spatial Autocorrelation (LISA) analysis was conducted to identify contiguous areas with high mortality rates. Scan analysis identified clusters of high spatial-temporal risks.

RESULTS

The highest mortality rates and clusters were in municipalities located in the Northeast region and in the states of Tocantins and Roraima (North region), Mato Grosso do Sul (Central-West region), and Minas Gerais (Southeast region). According to LISA, there was an increase in the number of municipalities classified as high priority from the first 3-year period (n = 434) to the last 3-year period (n = 644). The spatio-temporal analysis identified 21 high-risk clusters for VL mortality.

CONCLUSION

Areas with a high risk of VL mortality should prioritise preventing transmission, invest in early diagnosis and treatment, and promote the training of healthcare professionals.

Genetic diversity in Leishmania infantum and Leishmania tropica isolates from human and canine hosts in northern Morocco

This study investigated nine provinces in northern Morocco and collected 275 skin scraping, 22 bone marrow aspirates, and 89 fine needle aspirations from suspected cutaneous leishmaniasis (CL) and visceral leishmaniasis (VL) patients and potentially infected dogs. Molecular analysis using ITS1 RFLP PCR and RT-PCR revealed a higher prevalence of L. infantum (66.18 %; χ2 = 28.804; df = 1; P-value = 8.01e-08) than L. tropica in skin scraping, with L. infantum being the sole causative agent for both VL and canine leishmaniasis. L. infantum was predominantly found in most provinces, while L. tropica was relatively more dominant in Taza Province. Discriminant Analysis of Principal Components (DAPC) revealed distinct clustering between L. tropica and the other three species. However, no small subset of SNPs could clearly differentiate between Infantum_CL, Infantum_VL, and CanL, as they likely share a significant genetic background. The high rate of L. infantum could be attributed to the abundance of sand fly species transmitting VL. In Taza Province, Phlebotomus sergenti, responsible for anthroponotic CL, is the most abundant species. DNA sequencing demonstrated sequence heterogeneity in L. infantum (variants 1-9) and L. tropica (variants 1-7). Phylogenetic analysis showed a distinct separation between L. tropica and L. infantum strains, with an overlap among L. infantum strains isolated from cutaneous, visceral, and canine cases, and dogs serving as the central population for L. infantum.

Spiro-Acridine Compound as a Pteridine Reductase 1 Inhibitor: in silico Target Fishing and in vitro Studies

Among the many neglected tropical diseases, leishmaniasis ranks second in mortality rate and prevalence. In a previous study, acridine derivatives were synthesized and tested for their antileishmanial activity against L. chagasi. The most active compound identified in that study (1) showed a single digit IC50 value against the parasite (1.10 μg/mL), but its macromolecular target remained unknown. Aiming to overcome this limitation, this work exploited inverse virtual screening to identify compound 1's putative molecular mechanism of action. In vitro assays confirmed that compound 1 binds to Leishmania chagasi pteridine reductase 1 (LcPTR1), with moderate affinity (Kd=33,1 μM), according to differential scanning fluorimetry assay. Molecular dynamics simulations confirm the stability of LcPTR1-compound 1 complex, supporting a competitive mechanism of action. Therefore, the workflow presented in this work successfully identified PTR1 as a macromolecular target for compound 1, allowing the designing of novel potent antileishmanial compounds.

Spatio-Temporal distribution of a vector of cutaneous leishmaniasis: Pintomyia longiflocosa, in a population from the Colombian Andean Mountains

BACKGROUND

Leishmaniasis, a neglected disease and public health concern, is associated with various factors such as biological, social, economical conditions and climate, increasing the risk of human infection. Understanding the population dynamics of the vectors, like Pintomyia longiflocosa, and its relationship with ecological variables is crucial for developing effective strategies to control sand fly populations and combat cutaneous leishmaniasis in a tropical country like Colombia.

METHODOLOGY

Adult sand flies were collected in three different sample locations: outdoor, indoor, and peri-domestic areas in three houses located in the rural settlement of Campoalegre (Huila) between February 2020 and February 2021, using the CDC light traps. The sand fly density was quantified and associated with the sample locations and the sampling months using Analysis of Variance and Pearson correlations.

PRINCIPAL FINDINGS

In the period of the sample, 98.86% of sand fly collected was identified as Pi. longiflocosa. The density of this species was significantly different between males and females, the latter contributing more to density in all sample locations (P<0.0001). The outdoor was the sample location with the highest and most significative density in this study (70%, P = 0.04). The density of these sand flies is related to the seasonality of Campoalegre, revealing a density peak from February and June to October (P < 0.05). Finally, precipitation is the environmental variable prominently linked to the density pattern, showing a negative correlation with it. Months with the highest precipitations show the lowest values of Pi. longiflocosa abundance.

CONCLUSIONS/SIGNICANCE

Our investigation reveals a inverse correlation between precipitation levels and the abundance of Pi. longiflocosa in Campoalegre (Huila), particularly in outdoor areas. This suggests that vector control strategies to periods of reduced precipitation in outdoor settings could offer an effective approach to minimizing cases of cutaneous leishmaniasis in the region.

A panel of recombinant Leishmania donovani cell surface and secreted proteins identifies LdBPK_323600.1 as a serological marker of symptomatic infection

Visceral leishmaniasis is a deadly infectious disease and is one of the world's major neglected health problems. Because the symptoms of infection are similar to other endemic diseases, accurate diagnosis is crucial for appropriate treatment. Definitive diagnosis using splenic or bone marrow aspirates is highly invasive, and so, serological assays are preferred, including the direct agglutination test (DAT) or rK39 strip test. These tests, however, are either difficult to perform in the field (DAT) or lack specificity in some endemic regions (rK39), making the development of new tests a research priority. The availability of Leishmania spp. genomes presents an opportunity to identify new diagnostic targets. Here, we use genome data and a mammalian protein expression system to create a panel of 93 proteins consisting of the extracellular ectodomains of the Leishmania donovani cell surface and secreted proteins. We use these panel and sera from murine experimental infection models and natural human and canine infections to identify new candidates for serological diagnosis. We observed a concordance between the most immunoreactive antigens in different host species and transmission settings. The antigen encoded by the LdBPK_323600.1 gene can diagnose Leishmania infections with high sensitivity and specificity in patient cohorts from different endemic regions including Bangladesh and Ethiopia. In longitudinal sampling of treated patients, we observed reductions in immunoreactivity to LdBPK_323600.1 suggesting it could be used to diagnose treatment success. In summary, we have identified new antigens that could contribute to improved serological diagnostic tests to help control the impact of this deadly tropical infectious disease.

IMPORTANCE

Visceral leishmaniasis is fatal if left untreated with patients often displaying mild and non-specific symptoms during the early stages of infection making accurate diagnosis important. Current methods for diagnosis require highly trained medical staff to perform highly invasive biopsies of the liver or bone marrow which pose risks to the patient. Less invasive molecular tests are available but can suffer from regional variations in their ability to accurately diagnose an infection. To identify new diagnostic markers of visceral leishmaniasis, we produced and tested a panel of 93 proteins identified from the genome of the parasite responsible for this disease. We found that the pattern of host antibody reactivity to these proteins was broadly consistent across naturally acquired infections in both human patients and dogs, as well as experimental rodent infections. We identified a new protein called LdBPK_323600.1 that could accurately diagnose visceral leishmaniasis infections in humans.

Quinine and chloroquine: Potential preclinical candidates for the treatment of tegumentary Leishmaniasis

Leishmaniasis is an endemic disease in more than 90 countries, constituting a relevant public health problem. Limited treatment options, increase in resistance, and therapeutic failure are important aspects for the discovery of new treatment options. Drug repurposing may accelerate the discovery of antiLeishmanial drugs. Recent tests indicating the in vitro potential of antimalarials Leishmania resulted in the design of this study. This study aimed at evaluating the susceptibility of Leishmania (L.) amazonensis to chloroquine (CQ) and quinine (QN), alone or in combination with amphotericin B (AFT) and pentamidine (PTN). In the in vitro tests, first, we evaluated the growth inhibition of 50 % of promastigotes (IC50) and cytotoxicity for HepG2 and THP-1 cells (CC50). The IC50 values of AFT and PNT were below 1 µM, while the IC50 values of CQ and QN ranged between 4 and 13 µM. Concerning cytotoxicity, CC50 values ranged between 7 and 30 µM for AFT and PNT, and between 22 and 157 µM for the antimalarials. We also calculated the Selectivity Index (SI), where AFT and PTN obtained the highest values, while the antimalarias obtained values between 5 and 12. Both antimalarials were additive (ƩFIC 1.05-1.8) in combination with AFT and PTN. For anti-amastigote activity, the drugs obtained the following ICA50 values: AFT (0.26 µM), PNT (2.09 µM), CQ (3.77 µM) and QN (24.5 µM). In the in vivo tests, we observed that the effective dose for the death of 50 % of parasites (ED50) of AFT and CQ were 0.63 mg/kg and 27.29 mg/kg, respectively. When combining CQ with AFT, a decrease in parasitemia was observed, being statistically equal to the naive group. For cytokine quantification, it was observed that CQ, despite presenting anti-inflammatory activity was effective at increasing the production of IFN-γ. Overall, our data indicate that chloroquine will probably be a candidate for repurposing and use in drug combination therapy.

Gold(I) and Silver(I) Complexes Containing Hybrid Sulfonamide/Thiourea Ligands as Potential Leishmanicidal Agents

Leishmaniasis is a group of parasitic diseases with the potential to infect more than 1 billion people; however, its treatment is still old and inadequate. In order to contribute to changing this view, this work consisted of the development of complexes derived from MI metal ions with thioureas, aiming to obtain potential leishmanicidal agents. The thiourea ligands (HLR) were obtained by reactions of p-toluenesulfohydrazide with R-isothiocyanates and were used in complexation reactions with AgI and AuI, leading to the formation of complexes of composition [M(HLR)2]X (M = Ag or Au; X = NO3- or Cl-). All compounds were characterized by FTIR, 1H NMR, UV-vis, emission spectroscopy and elemental analysis. Some representatives were additionally studied by ESI-MS and single-crystal XRD. Their properties were further analyzed by DFT calculations. Their cytotoxicity on Vero cells and the extracellular leishmanicidal activity on Leishmania infantum and Leishmania braziliensis cells were evaluated. Additionally, the interaction of the complexes with the Old Yellow enzyme of the L. braziliensis (LbOYE) was examined. The biological tests showed that some compounds present remarkable leishmanicidal activity, even higher than that of the standard drug Glucantime, with different selectivity for the two species of Leishmania. Finally, the interaction studies with LbOYE revealed that this enzyme could be one of their biological targets.

Multi-epitope vaccine design against leishmaniasis using IFN-γ inducing epitopes from immunodominant gp46 and gp63 proteins

There is no currently approved human vaccine against leishmaniasis. Utilization of immunogenic antigens and their epitopes capable of enhancing immune responses against leishmaniasis is a crucial step for rational in silico vaccine design. The objective of this study was to generate and evaluate a potential vaccine candidate against leishmaniasis, designed by immunodominant proteins from gp46 and gp63 of Leishmania major, which can stimulate helper T-lymphocytes (HTL) and cytotoxic T-lymphocytes (CTL). For this aim, the IFN-γ-inducing MHC-I and MHC-II binders were predicted for each examined protein (gp46 and gp63) and connected with appropriate linkers, along with an adjuvant (Mycobacterium tuberculosis L7/L12) and a histidine tag. The vaccine's stability, antigenicity, structure, and interaction with the TLR-4 receptor were evaluated in silico. The resulting chimeric vaccine was composed of 344 amino acids and had a molecular weight of 35.64 kDa. Physico-chemical properties indicated that it was thermotolerant, soluble, highly antigenic, and non-allergenic. Predictions of the secondary and tertiary structures were made, and further analyses confirmed that the vaccine construct could interact with the human TLR-4 receptor. Virtual immune simulation demonstrated strong stimulation of T-cell responses, particularly by an increase in IFN-γ, following vaccination. In summary, the in silico data indicated that the vaccine candidate showed high antigenicity in humans. It was also found to trigger significant levels of clearance mechanisms and other components of the cellular immune profile. Nevertheless, further wet experiments are required to properly assess the efficacy of this multi-epitope vaccine candidate against leishmaniasis.

A novel outlook in the delivery of artemisinin: production and efficacy in experimental visceral leishmaniasis

The visceral form of leishmaniasis (VL), due to infection by Leishmania infantum, is a neglected tropical disease. The accessible therapeutic options are limited. Artemisinin is an efficient antileishmanial product with poor biological availability that requires high repetition of therapeutic doses in VL. Solid lipid nanoparticles (SLNs) provide targeted delivery, increase bioavailability and reduce toxicity of the traditional therapeutic strategy. The spherical shape artemisinin-loaded SLNs were prepared in a particle diameter of 222.0 ± 14.0 nm. The SLNs showed no particular toxic effect on the parasites, whereas the native artemisinin demonstrated a significant toxicity rate of 31% in viability of the promastigotes at the 250 µg/ml concentration. The therapeutic efficacy of the artemisinin-loaded SLNs was demonstrated in the experimental VL, using the L. infantum-infected BALB/c mice, in the present study. The 10 and 20 mg/kg doses of artemisinin-loaded SLNs showed higher level of antileishmanial efficacy compared with the free artemisinin. There was a significant diminishing of the parasite burden in liver (84.7 ± 4.9%) and spleen (85.0 ± 3.1%) and hepatosplenomegaly by the artemisinin-loaded SLNs treated at 20 mg/kg compared to the free artemisinin. Therefore, the present study supports the superior efficacy of artemisinin-loaded SLNs over the free artemisinin and could be considered as a new therapeutic strategy in the treatment of leishmaniasis.

Comparison of the Diagnostic Performances of Five Different Tests in Diagnosing Visceral Leishmaniasis in an Endemic Region of Ethiopia

The lack of accurate and feasible diagnostic tests poses a significant challenge to visceral leishmaniasis (VL) healthcare services in endemic areas. To date, various VL diagnostic tests have been or are being developed, and their diagnostic performances need to be assessed. In the present study, the diagnostic performances of rk39 RDT, the direct agglutination test (DAT), microscopy, loop-mediated isothermal amplification (LAMP), and miniature direct-on-blood polymerase chain reaction-nucleic acid lateral flow immunoassay (mini-dbPCR-NALFIA) were assessed using quantitative polymerase chain reaction (qPCR) as the reference test in an endemic region of Ethiopia. In this study, 235 suspected VL cases and 104 non-endemic healthy controls (NEHCs) were recruited. Among the suspected VL cases, 144 (61.28%) tested positive with qPCR. The sensitivities for rk39 RDT, DAT, microscopy, LAMP assay, and mini-dbPCR-NALFIA were 88.11%, 96.50%, 76.58%, 94.33%, and 95.80%, respectively. The specificities were 83.33%, 97.96%, 100%, 97.38%, and 98.92% for rk39 RDT, DAT, microscopy, LAMP assay, and mini-dbPCR-NALFIA, respectively. In conclusion, rk39 RDT and microscopy exhibited lower sensitivities, while DAT demonstrated excellent performance. LAMP and mini-dbPCR-NALFIA showed excellent performances with feasibility for implementation in remote endemic areas, although the latter requires further evaluation in such regions.

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

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

Molecular identification of Leishmania tropica in mammals occurring in human-inhabited areas of a cutaneous leishmaniasis endemic focus in North-West Pakistan

Cutaneous Leishmaniasis is endemic in the tribal district of Khyber near the Pak-Afghan border and is caused by Leishmania tropica. In Pakistan, cutaneous leishmaniasis caused by L. tropica is considered anthroponotic and is thought to be maintained by a human-sand fly-human transmission cycle. Along with humans, other mammals may also be acting as reservoir hosts of leishmaniasis in the study area. To investigate the role of non-human mammals in the transmission of leishmaniasis, blood samples were collected from 245 animals from the CL endemic district of Khyber, Pakistan. Leishmania parasite in these samples was detected by amplifying the species-specific sequences in minicircle kinetoplast DNA, using PCR. L. tropica DNA was detected in 18 (7.35%) samples, comprising 11 cows (Bos taurus), 6 goats (Capra hircus), and 1 dog (Canus lupus familiaris). Only a single cow and dog had a leishmaniasis-like lesion, and the remaining positive samples were asymptomatic. None of the tested sheep (Ovis aries) and rat (Rattus rattus, Rattus norvegicus) was positive. The present study reports the first instance of molecular detection of L. tropica in domestic animals. Our study indicates that along with humans' cows, goats and dogs may also be playing an important role in the transmission of anthroponotic cutaneous leishmaniasis in district Khyber in particular and Pakistan in general.

Drug Discovery Based on Oxygen and Nitrogen (Non-)Heterocyclic Compounds Developed @LAQV-REQUIMTE/Aveiro

Artur Silva's research group has a long history in the field of medicinal chemistry. The development of new synthetic methods for oxygen (mostly polyphenols, e.g., 2- and 3-styrylchromones, xanthones, flavones) and nitrogen (e.g., pyrazoles, triazoles, acridones, 4-quinolones) heterocyclic compounds in order to be assessed as antioxidant, anti-inflammatory, antidiabetic, and anticancer agents has been the main core work of our research interests. Additionally, the synthesis of steroid-type compounds as anti-Alzheimer drugs as well as of several chromophores as important dyes for cellular imaging broadened our research scope. In this review article, we intend to provide an enlightened appraisal of all the bioactive compounds and their biological properties that were synthesized and studied by our research group in the last two decades.

Antiparasitic effect of Farnesol against Leishmania major: A rationale from in vitro and in silico investigations

Leishmaniasis is a vector-borne parasitic infection caused by the infective bite of female Phlebotomine sandflies. Treatment of leishmaniasis by conventional synthetic compounds is met by challenges pertaining to adverse effects which call for the discovery of newer anti-leishmanial molecules. This study was performed to evaluate the effect and modes of action of a sesquiterpene alcoholic molecule Farnesol on Leishmania major, the causative agent of Zoonotic CL. The cytotoxic effect of Farnesol against L.major promastigotes, amastigotes and macrophages was assessed by MTT test and counting. The IC50 on promastigotes by Farnesol on L.major was also evaluated by flow cytometry. In the findings, promastigotes were reduced at 167μM. The mean numbers of L.major amastigotes in macrophages were significantly decreased on exposure to Farnesol at 172μM. In addition, Farnesol induced significant apoptosis dose-dependent on L.major promastigotes. In silico protein-ligand_binding analyses indicated the effect of Farnesol in perturbation of the ergosterol synthesis pathway of Leishmania with attributes suggesting inhibition of Lanosterol-α-demethylase, the terminal enzyme of ergosterol synthesis machinery. Findings from flow cytometry reveal the role of Farnesol in apoptosis-induced killing in promastigotes. Farnesol was effective at very lower concentrations when compared to Paromomycin. Further studies are crucial to evaluate the therapeutic potential of Farnesol alone or in combination with other conventional drugs in animal models.

Vaccine value profile for leishmaniasis

Leishmania infections are global, occurring in 98 countries and all World Health Organization (WHO) regions with 600 million to 1 billion people at risk of infection. Visceral leishmaniasis is associated with almost 20,000 reported deaths annually, with children under 5 years of age being at the greatest risk of mortality. Amongst WHO-recognised Neglected Tropical Diseases (NTDs), leishmaniasis is one of the most important in terms of mortality and morbidity. With an increasing global burden of disease and a growing threat from climate change, urbanisation and drug resistance, there remains an imperative to develop leishmaniasis vaccines. New tools to understand correlates of protection and to assess vaccine efficacy are being developed to ease the transition into larger scale efficacy trials or provide alternate routes to licensure. Early indications suggest a diverse portfolio of manufacturers exists in endemic countries with an appetite to develop leishmaniasis vaccines. This Vaccine Value Profile (VVP) provides a high-level, comprehensive assessment of the currently available data to inform the potential public health, economic, and societal value of leishmaniasis vaccines. The leishmaniasis VVP was developed by a working group of subject matter experts from academia, public health groups, policy organizations, and non-profit organizations. All contributors have extensive expertise on various elements of the leishmaniasis VVP and have collectively described the state of knowledge and identified the current gaps. The VVP was developed using only existing and publicly available information.

Functionally distinct regions of the locus Leishmania major response 15 control IgE or IFNγ level in addition to skin lesions

Leishmaniasis, a disease caused by parasites of Leishmania spp., endangers more than 1 billion people living in endemic countries and has three clinical forms: cutaneous, mucocutaneous, and visceral. Understanding of individual differences in susceptibility to infection and heterogeneity of its pathology is largely lacking. Different mouse strains show a broad and heterogeneous range of disease manifestations such as skin lesions, splenomegaly, hepatomegaly, and increased serum levels of immunoglobulin E and several cytokines. Genome-wide mapping of these strain differences detected more than 30 quantitative trait loci (QTLs) that control the response to Leishmania major. Some control different combinations of disease manifestations, but the nature of this heterogeneity is not yet clear. In this study, we analyzed the L. major response locus Lmr15 originally mapped in the strain CcS-9 which carries 12.5% of the genome of the resistant strain STS on the genetic background of the susceptible strain BALB/c. For this analysis, we used the advanced intercross line K3FV between the strains BALB/c and STS. We confirmed the previously detected loci Lmr15, Lmr18, Lmr24, and Lmr27 and performed genetic dissection of the effects of Lmr15 on chromosome 11. We prepared the interval-specific recombinant strains 6232HS1 and 6229FUD, carrying two STS-derived segments comprising the peak linkage of Lmr15 whose lengths were 6.32 and 17.4 Mbp, respectively, and analyzed their response to L. major infection. These experiments revealed at least two linked but functionally distinct chromosomal regions controlling IFNγ response and IgE response, respectively, in addition to the control of skin lesions. Bioinformatics and expression analysis identified the potential candidate gene Top3a. This finding further clarifies the genetic organization of factors relevant to understanding the differences in the individual risk of disease.

High seroprevalence of Leishmania infantum is linked to immune activation in people with HIV: a two-stage cross-sectional study in Bahia, Brazil

Visceral leishmaniasis is an opportunistic disease in HIV-1 infected individuals, unrecognized as a determining factor for AIDS diagnosis. The growing geographical overlap of HIV-1 and Leishmania infections is an emerging challenge worldwide, as co-infection increases morbidity and mortality for both infections. Here, we determined the prevalence of people living with HIV (PWH) with a previous or ongoing infection by Leishmania infantum and investigated the virological and immunological factors associated with co-infection. We adopted a two-stage cross-sectional cohort (CSC) design (CSC-I, n = 5,346 and CSC-II, n = 317) of treatment-naïve HIV-1-infected individuals in Bahia, Brazil. In CSC-I, samples collected between 1998 and 2013 were used for serological screening for leishmaniasis by an in-house Enzyme-Linked Immunosorbent Assay (ELISA) with SLA (Soluble Leishmania infantum Antigen), resulting in a prevalence of previous or ongoing infection of 16.27%. Next, 317 PWH were prospectively recruited from July 2014 to December 2015 with the collection of sociodemographic and clinical data. Serological validation by two different immunoassays confirmed a prevalence of 15.46 and 8.20% by anti-SLA, and anti-HSP70 serology, respectively, whereas 4.73% were double-positive (DP). Stratification of these 317 individuals in DP and double-negative (DN) revealed a significant reduction of CD4+ counts and CD4+/CD8+ ratios and a tendency of increased viral load in the DP group, as compared to DN. No statistical differences in HIV-1 subtype distribution were observed between the two groups. However, we found a significant increase of CXCL10 (p = 0.0076) and a tendency of increased CXCL9 (p = 0.061) in individuals with DP serology, demonstrating intensified immune activation in this group. These findings were corroborated at the transcriptome level in independent Leishmania- and HIV-1-infected cohorts (Swiss HIV Cohort and Piaui Northeast Brazil Cohort), indicating that CXCL10 transcripts are shared by the IFN-dominated immune activation gene signatures of both pathogens and positively correlated to viral load in untreated PWH. This study demonstrated a high prevalence of PWH with L. infantum seropositivity in Bahia, Brazil, linked to IFN-mediated immune activation and a significant decrease in CD4+ levels. Our results highlight the urgent need to increase awareness and define public health strategies for the management and prevention of HIV-1 and L. infantum co-infection.

Case Report: FDG-PET/CT findings in co-infection of visceral leishmaniasis and chronic hepatitis B

Visceral leishmaniasis is an opportunistic infection in immunocompromised patients. Herein, we report a case of an adult male patient with a persistent fever of unknown origin, along with chronic hepatitis B. The patient underwent bone marrow aspiration twice, which revealed hemophagocytosis. Abdomen enhanced CT revealed splenomegaly with a persistent strengthening of multiple nodules, and hemangiomas were diagnosed. A subsequent 18-fluoro-deoxyglucose (18F-FDG) PET/CT scan, which was implemented to search for the reason for the fever, showed diffuse splenic disease uptake, and splenic lymphoma was considered as the diagnosis. His clinical symptoms improved after receiving hemophagocytic lymphohistiocytosis (HLH) chemotherapy. However, the patient was readmitted for fever again only 2 months later. Splenectomy surgery is performed to confirm the diagnosis and classification of lymphoma. Visceral leishmaniasis was eventually diagnosed in a spleen specimen and the third bone marrow biopsy. He received treatment with lipid amphotericin B and remained recurrence-free for 1 year. In this paper, we aim to provide detailed information that will help further our understanding of the clinical symptoms and radiographic findings of visceral leishmaniasis.

Computer-aided drug design approaches applied to screen natural product's structural analogs targeting arginase in Leishmania spp

Introduction: Leishmaniasis is a disease with high mortality rates and approximately 1.5 million new cases each year. Despite the new approaches and advances to fight the disease, there are no effective therapies. Methods: Hence, this study aims to screen for natural products' structural analogs as new drug candidates against leishmaniasis. We applied Computer-aided drug design (CADD) approaches, such as virtual screening, molecular docking, molecular dynamics simulation, molecular mechanics-generalized Born surface area (MM-GBSA) binding free estimation, and free energy perturbation (FEP) aiming to select structural analogs from natural products that have shown anti-leishmanial and anti-arginase activities and that could bind selectively against the Leishmania arginase enzyme. Results: The compounds 2H-1-benzopyran, 3,4-dihydro-2-(2-methylphenyl)-(9CI), echioidinin, and malvidin showed good results against arginase targets from three parasite species and negative results for potential toxicities. The echioidinin and malvidin ligands generated interactions in the active center at pH 2.0 conditions by MM-GBSA and FEP methods. Conclusions: This work suggests the potential anti-leishmanial activity of the compounds and thus can be further in vitro and in vivo experimentally validated.

Natural products derived steroids as potential anti-leishmanial agents; disease prevalence, underlying mechanisms and future perspectives

Leishmaniasis is a vector-borne infection caused by protozoan parasites from the genus leishmania and is among the most neglected tropical diseases. It is highly prevalent disease, affecting about 350 million population worldwide. Only limited number of anti-leishmanial agents are approved for clinical use till now and they are associated with side effects and have limited efficacy. Subsequently, natural products based discovery of more safe and effective drugs against leishmania is under scientific consideration. Various studies reported the efficacy of natural products against intracellular and extracellular forms of leishmania species. This work is aimed to evaluate current literature focused on the anti-leihmanial efficacy of steroidal moieties from natural products and their mechanism of action. Compounds including steroidal saponins, steroidal alkaloids and phytosterols were found to exhibit considerable anti-leishmanial efficacy. For instance, steroidal saponin, (25R)-spirost-5-en-3b-ol,3-O-α-rhamnopyranosyl-(1 → 4)-α-rhamnopyranosyl-(1 → 4)-[a-rhamnopyranosyl-(1 → 2)]-glucopyranoside isolated from A. paradoxum has completely eradicated Leishmania major promastigotes at 50 µg mL-1 dose. Spirostanic saponins isolated from Solanum paniculatum L. were effective against Leishmania amazonensis promastigotes. Turgidosterones isolated from Panicum turgidum exhibited high leishmanicidal potentials against Leishmania donovani promastigotes with IC50 of 4.95-8.03 µg mL-1 and even better activity against amastigotes exhibiting an IC50 of 4.50-9.29 µg mL-1. Likewise, racemoside-A from Asparagus racemosus was found effective against an antimonial sensitive (AG83) and antimonial resistant (GE1F8R) strains of the L. donovani. Moreover, steroidal alkaloids including hookerianamide-1, hookerianamide-H, hookerianamide-J, hookerianamide-K, dehydrosarsalignone, vagenine-A, sarcovagine-C, holaphylline, saracodine, holamine, 15-α hydroxyholamine, holacurtin, N-desmethyl holacurtine and elasticine has exhibited time and dose-dependent efficacy against various strains of leishmania. β-sitosterol was found active against multiple strains of leishmania. These compounds mainly exhibit their therapeutic efficacy via liberation of ROS, mitochondrial depolarization, morphological and ultra-structural changes, accumulation of lipid droplets, depletion of non-protein thiols and triggering apoptotic pathways. In conclusion, leishmaniasis is a major health problem in many countries. Plants-derived steroids moieties have reveled efficacy against leishmaniasis and is a source of lead compounds. Further detailed molecular studies are warranted for the discovery of more effective and safe anti-leishmanial drugs.

Cloning, expression and in vitro validation of chimeric multi epitope vaccine candidate against visceral leishmaniasis infection

Visceral Leishmaniasis or Kala-Azar is one of the most severe and deadly neglected tropical disease caused by the Leishmania parasite. A few number of vaccines are going through different phases in clinical trial but failing of these vaccines in successive phase trial or less efficacy, urge to develop highly immunogenic and cost-effective treatment to get rid of deadly VL. This study focuses on the development of more potent vaccine candidate against VL. The recombinant vaccine candidate LeiSp was expressed in Pichia pastoris, followed by purification and characterization. The purified protein was also tested for any post-translation modification, which favors being a potent immunogenic candidate. Further, the expression modulation of different pro-inflammatory and anti-inflammatory cytokines was evaluated in THP1 cell lines. A significant upregulation in the expression of pro-inflammatory cytokines while no significant changes were observed in the expression of anti-inflammatory cytokines. The impact of recombinant vaccine protein candidates in infected conditions were determined. Here, upon treatment with chimeric vaccine protein candidate, we observed a considerable recovery in the expression level of pro-inflammatory cytokines, which were downregulated upon infection alone. In addition to this, we found a significant decrease in the expression of anti-inflammatory cytokines, which were upregulated during infection alone. We further validated our findings in infected hPBMCs and observed similar expression modulation of pro-inflammatory and anti-inflammatory cytokines with and without treatment. Thus, the present study indicates that the chimeric LeiSp protein which was designed using bioinformatics approaches shows a potential inductive efficacy for pro-inflammatory cytokines in Leishmania-infected cells.

In Vitro Evaluation of Aerosol Therapy with Pentamidine-Loaded Liposomes Coated with Chondroitin Sulfate or Heparin for the Treatment of Leishmaniasis

The second-line antileishmanial compound pentamidine is administered intramuscularly or, preferably, by intravenous infusion, with its use limited by severe adverse effects, including diabetes, severe hypoglycemia, myocarditis and renal toxicity. We sought to test the potential of phospholipid vesicles to improve the patient compliance and efficacy of this drug for the treatment of leishmaniasis by means of aerosol therapy. The targeting to macrophages of pentamidine-loaded liposomes coated with chondroitin sulfate or heparin increased about twofold (up to ca. 90%) relative to noncoated liposomes. The encapsulation of pentamidine in liposomes ameliorated its activity on the amastigote and promastigote forms of Leishmania infantum and Leishmania pifanoi, and it significantly reduced cytotoxicity on human umbilical endothelial cells, for which the concentration inhibiting 50% of cell viability was 144.2 ± 12.7 µM for pentamidine-containing heparin-coated liposomes vs. 59.3 ± 4.9 µM for free pentamidine. The deposition of liposome dispersions after nebulization was evaluated with the Next Generation Impactor, which mimics human airways. Approximately 53% of total initial pentamidine in solution reached the deeper stages of the impactor, with a median aerodynamic diameter of ~2.8 µm, supporting a partial deposition on the lung alveoli. Upon loading pentamidine in phospholipid vesicles, its deposition in the deeper stages significantly increased up to ~68%, and the median aerodynamic diameter decreased to a range between 1.4 and 1.8 µm, suggesting a better aptitude to reach the deeper lung airways in higher amounts. In all, nebulization of liposome-encapsulated pentamidine improved the bioavailability of this neglected drug by a patient-friendly delivery route amenable to self-administration, paving the way for the treatment of leishmaniasis and other infections where pentamidine is active.

Development of a microemulsion loaded with epoxy-α-lapachone against Leishmania (Leishmania) amazonensis murine infection

Epoxy-α-lapachone (ELAP), an oxirane-functionalized molecule synthesized from naturally occurring lapachol, has shown promising activity against murine infection with Leishmania (Leishmania) amazonensis. Herein, we report the successful development of oil-in-water-type (o/w) microemulsions (ME) loaded with ELAP (ELAP-ME) using Capmul MCM, Labrasol, and PEG 400. Stability studies revealed that ELAP-ME (100 µg/mL of ELAP), which was comprised of globule size smaller than 120.4 ± 7.7 nm, displayed a good stability profile over 73 days. ELAP-ME had an effect in BALB/c mice infected with L. (L.) amazonensis, causing reductions in paw lesions after two weeks of treatment (∼2-fold) when compared to untreated animals. Furthermore, there was also a reduction in the parasite load both in the footpad (60.3%) and in the lymph nodes (31.5%). Based on these findings, ELAP-ME emerges as a promising treatment for tegumentar leishmaniasis.

Structure-Activity Relationship Studies of 9-Alkylamino-1,2,3,4-tetrahydroacridines against Leishmania (Leishmania) infantum Promastigotes

Leishmaniasis is one of the most neglected diseases in modern times, mainly affecting people from developing countries of the tropics, subtropics and the Mediterranean basin, with approximately 350 million people considered at risk of developing this disease. The incidence of human leishmaniasis has increased over the past decades due to failing prevention and therapeutic measures-there are no vaccines and chemotherapy, which is problematic. Acridine derivatives constitute an interesting group of nitrogen-containing heterocyclic compounds associated with numerous bioactivities, with emphasis to their antileishmanial potential. The present work builds on computational studies focusing on a specific enzyme of the parasite, S-adenosylmethionine decarboxylase (AdoMet DC), with several 1,2,3,4-tetrahydro-acridines emerging as potential inhibitors, evidencing this scaffold as a promising building block for novel antileishmanial pharmaceuticals. Thus, several 1,2,3,4-tetrahydroacridine derivatives have been synthesized, their activity against Leishmania (Leishmania) infantum promastigotes evaluated and a structure-activity relationship (SAR) study was developed based on the results obtained. Even though the majority of the 1,2,3,4-tetrahydroacridines evaluated presented high levels of toxicity, the structural information gathered in this work allowed its application with another scaffold (quinoline), leading to the obtention of N¹,N¹²-bis(7-chloroquinolin-4-yl)dodecane-1,12-diamine (12) as a promising novel antileishmanial agent (IC₅₀ = 0.60 ± 0.11 μM, EC₅₀ = 11.69 ± 3.96 μM and TI = 19.48).

Ecology and natural infection of phlebotomine sand flies in different ecotopes and environments in the municipality of Pains, Minas Gerais, Brazil

Phlebotomines (Diptera: Psychodidae) are vectors of protozoa of the genus Leishmania and distributed throughout Brazil, formerly restricted to rural areas, have expanded including to periurban and urban regions, been recorded in different habitats. This study aimed to understand the dynamics of sand flies in different ecotopes in the municipality of Pains. Sand flies were captured during thirty samplings using HP light traps installed in seven different ecotopes for two consecutive nights, once a month, from August 2018 to July 2019. A total of 1,352 sand flies were captured, representing 24 species belong to ten genera. Evandromyia edwardsi was the most abundant species, followed by Evandromyia lenti and Micropygomyia quinquefer. Leishmania DNA was detected in seven female sand flies in four ecotopes, for an infection rate of 0.9%. Sand flies were collected in all seven ecotopes, although forest (23.04%), cave (20.88%) and pasture (17.75%) had higher abundance and richness. Similarity was found among ecotopes, indicating that they are all important for the maintenance of the sand fly community. Spatial analysis indicated high densities of sand flies in areas with natural characteristics. All ecotopes in the municipality were evidenced to have an adequate and harmonious epidemiological profile for the transmission and expansion of leishmaniasis throughout the territory. Because of the increasing environmental changes and deforestation in the municipality, the risk of generating ecological imbalance and increased cases of leishmaniasis is imminent, which highlights the importance of developing preventive and control strategies.

Anti-leishmanial therapy: Caught between drugs and immune targets

Leishmaniasis is an enigmatic disease that has very restricted options for chemotherapy and none for prophylaxis. As a result, deriving therapeutic principles for curing the disease has been a major objective in Leishmania research for a long time. Leishmania is a protozoan parasite that lives within macrophages by subverting or switching cell signaling to the pathways that ensure its intracellular survival. Therefore, three groups of molecules aimed at blocking or eliminating the parasite, at least, in principle, include blockers of macrophage receptor- Leishmania ligand interaction, macrophage-activating small molecules, peptides and cytokines, and signaling inhibitors or activators. Macrophages also act as an antigen-presenting cell, presenting antigen to the antigen-specific T cells to induce activation and differentiation of the effector T cell subsets that either execute or suppress anti-leishmanial functions. Three groups of therapeutic principles targeting this sphere of Leishmania-macrophage interaction include antibodies that block pro-leishmanial response of T cells, ligands that activate anti-leishmanial T cells and the antigens for therapeutic vaccines. Besides these, prophylactic vaccines have been in clinical trials but none has succeeded so far. Herein, we have attempted to encompass all these principles and compose a comprehensive review to analyze the feasibility and adoptability of different therapeutics for leishmaniasis.

Sterol profiling of Leishmania parasites using a new HPLC-tandem mass spectrometry-based method and antifungal azoles as chemical probes reveals a key intermediate sterol that supports a branched ergosterol biosynthetic pathway

Human leishmaniasis is an infectious disease caused by Leishmania protozoan parasites. Current chemotherapeutic options against the deadly disease have significant limitations. The ergosterol biosynthetic pathway has been identified as a drug target in Leishmania. However, remarkable differences in the efficacy of antifungal azoles that inhibit ergosterol biosynthesis have been reported for the treatment of leishmaniasis. To better understand the sterol biosynthetic pathway in Leishmania and elucidate the mechanism underlying the differential efficacy of antifungal azoles, we developed a new LC-MS/MS method to study sterol profiles in promastigotes of three Leishmania species, including two L. donovani, one L. major and one L. tarentolae strains. A combination of distinct precursor ion masses and LC retention times allowed for specific detection of sixteen intermediate sterols between lanosterol and ergosterol using the newly developed LC-MS/MS method. Although both posaconazole and fluconazole are known inhibitors of fungal lanosterol 14α-demethylase (CYP51), only posaconazole led to a substantial accumulation of lanosterol in azole-treated L. donovani promastigotes. Furthermore, a key intermediate sterol accumulated by 40- and 7-fold when these parasites were treated with posaconazole and fluconazole, respectively, which was determined as 4α,14α-dimethylzymosterol by high resolution mass spectrometry and NMR spectroscopy. The identification of 4α,14α-dimethylzymosterol supports a branched ergosterol biosynthetic pathway in Leishmania, where lanosterol C4- and C14-demethylation reactions occur in parallel rather than sequentially. Our results suggest that selective inhibition of leishmanial CYP51 is insufficient to effectively prevent parasite growth and dual inhibitors of both CYP51 and the unknown sterol C4-demethylase may be required for optimal antiparasitic effect.

Current Applications of Plant-Based Drug Delivery Nano Systems for Leishmaniasis Treatment

Leishmania is a trypanosomatid that causes leishmaniasis. It is transmitted to vertebrate hosts during the blood meal of phlebotomine sandflies. The clinical manifestations of the disease are associated with several factors, such as the Leishmania species, virulence and pathogenicity, the host-parasite relationship, and the host's immune system. Although its causative agents have been known and studied for decades, there have been few advances in the chemotherapy of leishmaniasis. The urgency of more selective and less toxic alternatives for the treatment of leishmaniasis leads to research focused on the study of new pharmaceuticals, improvement of existing drugs, and new routes of drug administration. Natural resources of plant origin are promising sources of bioactive substances, and the use of ethnopharmacology and folk medicine leads to interest in studying new medications from phytocomplexes. However, the intrinsic low water solubility of plant derivatives is an obstacle to developing a therapeutic product. Nanotechnology could help overcome these obstacles by improving the availability of common substances in water. To contribute to this scenario, this article provides a review of nanocarriers developed for delivering plant-extracted compounds to treat clinical forms of leishmaniasis and critically analyzing them and pointing out the future perspectives for their application.

Determinants of anthroponotic cutaneous leishmaniasis by case-control study in Morocco

Leishmaniasis is endemic in Morocco where both cutaneous and visceral forms coexist. To date, anthroponotic cutaneous leishmaniasis (ACL) determinants remain poorly investigated in Morocco. However, the disease risk factors identification is vital to determine the specific preventive process. In this aim, a case-control study was conducted in the main active ACL foci in central Morocco. Epidemiological data were extracted from bulletins, registers and annual reports of the regional direction of Health offices. The socioeconomic and environmental data were collected from epidemiological surveys, completed by a questionnaire intended for accessible positive population and control people selected from the cases' entourage. The study included 258 cases and 395 controls. Our results showed that many socioeconomic factors were associated with ACL in Morocco such as the rural habitation (OR = 4.163; 95% CI: 2.91-5.96), movement to endemic area (OR = 4.53; 95% CI: 3.03-6.77), provenance from leishmaniasis foci (in Essaouira focus OR = 5.34; 95% CI: 1.19-24.03) and poverty. In addition, environmental factors like proximity of vegetation (OR = 2.45; 95% CI: 1.14-5.25), poor domestic hygiene, particularly the absence of sewage system/waste management (OR = 1.63; 95% CI: 1.35-1.96), and presence of animals (OR = 2.67; 95% CI: 1.14-5.25) increase the risk of ACL in Morocco. Except for Matrimonial status (married people, OR = 4.11; 95% CI: 1.80-9.41), there is however no significant association of the disease with the other socio-demographic factors in the study area (p>0.05). These several risk factors must be taken in consideration to prevent this disease through multidisciplinary collaboration and community participation.

Epidemiological and clinical characteristics of cutaneous leishmaniasis among patients attending at Tefera Hailu Memorial Hospital, Sekota, Northeast Ethiopia: A five-year trend analysis (2016-2020)

Objective

This study was designed to determine the epidemiological and clinical characteristics of cutaneous leishmaniasis among patients attending at Tefera Hailu Memorial Hospital, Sekota, Northeast Ethiopia over the last 5 years.

Methods

A 5-year retrospective study was conducted at Tefera Hailu Memorial Hospital, Northeast Ethiopia. Data were summarized and analysed using Microsoft Excel and SPSS 26 version software, respectively. To present the data and evaluate the patterns in cutaneous leishmaniasis cases across the 5 years, months, and seasons, descriptive statistics were utilized. In multivariable logistic regression analysis of determinants in relation to cutaneous leishmaniasis positivity, p-value less than 0.05 was considered as statistically significant.

Result

The overall positivity rate of cutaneous leishmaniasis was 31.1% (452 out of 1455) over the last 5 years at Tefera Hailu Memorial Hospital. The result showed a fluctuating yet declining trend in cutaneous leishmaniasis infections. The highest number of cases was registered in 2016, while the lowest was in 2020. Males and the age group of 15-49 years, accounted 78.5% and 79.9% of the patients, respectively, were the hardest hit by cutaneous leishmaniasis in the area. Similarly, the highest number of cases was observed in Dehana district (268). From all registered confirmed cases, 54 (10.7%) were previously treated cases. Moreover, the majority of cases, 423 (93.6%) were localized cutaneous leishmaniasis and most of the lesions were on the face.

Conclusion

Although the results indicate a fluctuating yet declining trend, the positivity rate of confirmed cutaneous leishmaniasis cases in the area remains alarming and indicates a major public health burden. Therefore, efforts are required to reduce the disease burden through continuous monitoring and evaluation of control measures in the study area.

Environmental, Climatic, and Parasite Molecular Factors Impacting the Incidence of Cutaneous Leishmaniasis Due to Leishmania tropica in Three Moroccan Foci

Cutaneous leishmaniasis (CL) occurring due to Leishmania tropica is a public health problem in Morocco. The distribution and incidence of this form of leishmaniasis have increased in an unusual way in the last decade, and the control measures put in place are struggling to slow down the epidemic. This study was designed to assess the impact of climatic and environmental factors on CL in L. tropica foci. The data collected included CL incidence and climatic and environmental factors across three Moroccan foci (Foum Jemaa, Imintanout, and Ouazzane) from 2000 to 2019. Statistical analyses were performed using the linear regression model. An association was found between the occurrence of CL in Imintanout and temperature and humidity (r² = 0.6076, df = (1.18), p-value = 3.09 × 10⁻⁵; r² = 0.6306, df = (1.18), p-value = 1.77 × 10⁻⁵). As a second objective of our study, we investigated the population structure of L.tropica in these three foci, using the nuclear marker internal transcribed spacer 1 (ITS1). Our results showed a low-to-medium level of geographic differentiation among the L.tropica populations using pairwise differentiation. Molecular diversity indices showed a high genetic diversity in Foum Jemaa and Imintanout; indeed, 29 polymorphic sites were identified, leading to the definition of 13 haplotypes. Tajima’s D and Fu’s F test statistics in all populations were not statistically significant, and consistent with a population at drift–mutation equilibrium. Further analysis, including additional DNA markers and a larger sample size, could provide a more complete perspective of L. tropica’s population structure in these three regions. In addition, further research is needed to better understand the impact of climatic conditions on the transmission cycle of Leishmania, allowing both for the development of effective control measures, and for the development of a predictive model for this parasitosis.

Benzylamines as highly potent inhibitors of the sterol biosynthesis pathway in Leishmania amazonensis leading to oxidative stress and ultrastructural alterations

Leishmaniasis is a neglected disease caused by protozoan parasites of the Leishmania genus. Benzylamines are a class of compounds selectively designed to inhibit the squalene synthase (SQS) that catalyzes the first committed reaction on the sterol biosynthesis pathway. Herein, we studied seven new benzylamines (SBC 37–43) against Leishmania amazonensis. After the first screening of cell viability, two inhibitors (SBC 39 and SBC 40) were selected. Against intracellular amastigotes, SBC 39 and SBC 40 presented selectivity indexes of 117.7 and 180, respectively, indicating high selectivity. Analysis of the sterol composition revealed a depletion of endogenous 24-alkylated sterols such as episterol and 5-dehydroepisterol, with a concomitant accumulation of fecosterol, implying a disturbance in cellular lipid content. This result suggests a blockade of de novo sterol synthesis at the level of SQS and C-5 desaturase. Furthermore, physiological analysis and electron microscopy revealed three main alterations: (1) in the mitochondrion; (2) the presence of lipid bodies and autophagosomes; and (3) the appearance of projections in the plasma membrane. In conclusion, our results support the notion that benzylamines have a potent effect against Leishmania amazonensis and should be an exciting novel pharmaceutical lead for developing new chemotherapeutic alternatives to treat leishmaniasis.

Evaluation of the inhibitory potential of Valproic acid against histone deacetylase of Leishmania donovani and computational studies of Valproic acid derivatives

Valproic acid (VA) is a proven inhibitor of human histone deacetylases (HDACs). The homogenous HDAC has been associated with all major human parasitic pathogens and hence, it has been considered an attractive drug target for anti-leishmanial therapy. To assist in drug design endeavors for HDACs, an in-vitro study has been presented to investigate the VA inhibition on Leishmania donovani HDAC (LdHDAC). The regression analysis of VA by 24 hrs viability assay confirmed its activity against LdHDAC. Moreover, the toxicity of VA is also well documented. Thus, the in-silico experiments were also conducted to screen the non-toxic VA derivatives as anti-leishmanial drug candidates having potential as inhibitors of LdHDAC. For in-silico study, the 3D structure of target LdHDAC was developed by homology modeling. Based on their in-silico activity, we shortlisted 13 VA derivatives having maximum affinity for LdHDAC and identified four potential derivatives that can specifically bind to this protein. After that, these ligands were subjected to molecular dynamics simulation. These derivatives may be effective against L. donovani promastigotes since they followed Lipinski's RO5 and were non-toxic. Thus, screened derivatives can be considered as lead ligands for targeting LdHDAC and may be used as possible drug candidates to treat leishmaniasis and overcome the limitation of anti-leishmanial drugs. This is the first report of antileishmanial potential of VA and its derivatives targeting LdHDAC. Hence, the current investigation presents a search for novel target specific drugs to aid the anti-leishmanial drug development. Communicated by Ramaswamy H. Sarma.

Estimating the global demand curve for a leishmaniasis vaccine: A generalisable approach based on global burden of disease estimates

Background

A pressing need exists to develop vaccines for neglected diseases, including leishmaniasis. However, the development of new vaccines is dependent on their value to two key players–vaccine developers and manufacturers who need to have confidence in the global demand in order to commit to research and production; and governments (or other international funders) who need to signal demand based on the potential public health benefits of the vaccine in their local context, as well as its affordability. A detailed global epidemiological analysis is rarely available before a vaccine enters a market due to lack of resources as well as insufficient global data necessary for such an analysis. Our study seeks to bridge this information gap by providing a generalisable approach to estimating the commercial and public health value of a vaccine in development relying primarily on publicly available Global Burden of Disease (GBD) data. This simplified approach is easily replicable and can be used to guide discussions and investments into vaccines and other health technologies where evidence constraints exist. The approach is demonstrated through the estimation of the demand curve for a future leishmaniasis vaccine.

Methodology/Principal findings

We project the ability to pay over the period 2030–2040 for a vaccine preventing cutaneous and visceral leishmaniasis (CL / VL), using an illustrative set of countries which account for most of the global disease burden. First, based on previous work on vaccine demand projections in these countries and CL / VL GBD-reported incidence rates, we project the potential long-term impact of the vaccine on disability-adjusted life years (DALYs) averted as a result of reduced incidence. Then, we apply an economic framework to our estimates to determine vaccine affordability based on the abilities to pay of governments and global funders, leading to estimates of the demand and market size. Based on our estimates, the maximum ability-to-pay of a leishmaniasis vaccine (per course, including delivery costs), given the current estimates of incidence and population at risk, is higher than $5 for 25–30% of the countries considered, with the average value-based maximum price, weighted by quantity demanded, being $5.7–6 [$0.3 - $34.5], and total demand of over 560 million courses.

Conclusion/Significance

Our results demonstrate that both the quantity of vaccines estimated to be required by the countries considered as well as their ability-to-pay could make a vaccine for leishmaniasis commercially attractive to potential manufacturers. The methodology used can be equally applied to other technology developments targeting health in developing countries.

A Review on Climate, Air Pollution, and Health in North Africa

PURPOSE OF REVIEW

The aim of this review is to summarize and provide clear insights into studies that evaluate the interaction between air pollution, climate, and health in North Africa.

RECENT FINDINGS

Few studies have estimated the effects of climate and air pollution on health in North Africa. Most of the studies highlighted the evidence of the link between climate and air pollution as driving factors and increased mortality and morbidity as health outcomes. Each North African country prioritized research on a specific health factor. It was observed that the health outcome from each driving factor depends on the studied area and data availability. The latter is a major challenge in the region. As such, more studies should be led in the future to cover more areas in North Africa and when more data are available. Data availability will help to explore the applicability of different tools and techniques new to the region. This review explores studies related to climate and air pollution, and their possible impacts on health in North Africa. On one hand, air quality studies have focused mainly on particulate matter exceedance levels and their long-term exposure impacts, namely, morbidity and mortality. The observed differences between the various studies are mainly due to the used exposure-response function, the studied population, background emissions, and natural emission from the Sahara Desert that characterize the region. On the other hand, climate studies have focused primarily on the impact of heat waves, vector-borne disease, and mental disorders. More than half of these studies have been on leishmaniasis disease. The review revealed unbalanced and insufficient research on health impacts from air pollution episodes and climate extremes across the region.

Metalloprotease Gp63-Targeting Novel Glycoside Exhibits Potential Antileishmanial Activity

Visceral leishmaniasis (VL) and post kala-azar dermal leishmaniasis (PKDL) affect most of the poor populations worldwide. The current treatment modalities include liposomal formulation or deoxycholate salt of amphotericin B, which has been associated with various complications and severe side effects. Encouraged from the recent marked antimalarial effects from plant-derived glycosides, in this study, we have exploited a green chemistry-based approach to chemically synthesize a library of diverse glycoside derivatives (Gly1–12) and evaluated their inhibitory efficacy against the AG83 strain of Leishmania donovani. Among the synthesized glycosides, the in vitro inhibitory activity of Glycoside-2 (Gly2) (1.13 µM IC50 value) on L. donovani promastigote demonstrated maximum cytotoxicity with ~94% promastigote death as compared to amphotericin B that was taken as a positive control. The antiproliferative effect of Gly2 on promastigote encouraged us to analyze the structure–activity relationship of Gly2 with Gp63, a zinc metalloprotease that majorly localizes at the surface of the promastigote and has a role in its development and multiplication. The result demonstrated the exceptional binding affinity of Gly2 toward the catalytic domain of Gp63. These data were thereafter validated through cellular thermal shift assay in a physiologically relevant cellular environment. Mechanistically, reduced multiplication of promastigotes on treatment with Gly2 induces the destabilization of redox homeostasis in promastigotes by enhancing reactive oxygen species (ROS), coupled with depolarization of the mitochondrial membrane. Additionally, Gly2 displayed strong lethal effects on infectivity and multiplication of amastigote inside the macrophage in the amastigote–macrophage infection model in vitro as compared to amphotericin B treatment. Gp63 is also known to bestow protection against complement-mediated lysis of parasites. Interestingly, Gly2 treatment enhances the complement-mediated lysis of L. donovani promastigotes in serum physiological conditions. In addition, Gly2 was found to be equally effective against the clinical promastigote forms of PKDL strain (IC50 value of 1.97 µM); hence, it could target both VL and PKDL simultaneously. Taken together, this study reports the serendipitous discovery of Gly2 with potent antileishmanial activity and proves to be a novel chemotherapeutic prototype against VL and PKDL.

Influence of the presence of mannose-binding lectin polymorphisms on the occurrence of leishmaniasis: a systematic review and meta-analysis

BACKGROUND

Leishmaniasis is caused by an intracellular protozoan of the Leishmania genus. Mannose-binding lectin (MBL) is a serum complement protein and recognizes lipoprotein antigens in protozoa and the bacterial plasma membrane. Nucleotide variants in the promoter region and exon 1 of the MBL gene can influence its expression or change its molecular structure.

OBJECTIVE

To evaluate, through a systematic review, case-control studies of the genetic association of variants in the MBL2 gene and the risk of developing leishmaniasis.

METHODS

This review carried out a search in PubMed, Science Direct, Cochrane Library, Scopus and Lilacs databases for case-control publications with six polymorphisms in the mannose-binding Lectin gene. The following strategy was used: P = Patients at risk of leishmaniasis; I = Presence of polymorphisms; C = Absence of polymorphisms; O = Occurrence of leishmaniasis. Four case/control studies consisting of 791 patients with leishmaniasis and 967 healthy subjects (Control) are included in this meta-analysis. The association of variants in the mannose-binding Lectin gene and leishmaniasis under the allelic genetic model, -550 (Hvs. L), -221 (X vs. Y), +4 (Q vs. P), CD52 (A vs. D), CD54 (A vs. B), CD57 (A vs. C) and A/O genotype (A vs. O) was evaluated. International Prospective Register of Systematic Reviews (PROSPERO): CRD42020201755.

RESULTS

The meta-analysis results for any allelic genetic model showed no significant association for the variants within the promoter, the untranslated region, and exon 1, as well as for the wild-type A allele and mutant allele O with leishmaniasis.

STUDY LIMITATIONS

Caution should be exercised when interpreting these results, as they are based on a few studies, which show divergent results when analyzed separately.

CONCLUSIONS

This meta-analysis showed a non-significant association between the rs11003125, rs7096206, rs7095891, rs5030737, rs1800450, and rs1800451 polymorphisms of the Mannose-binding Lectin gene and leishmaniasis in any allelic and heterogeneous evaluation.

Sand flies: Basic information on the vectors of leishmaniasis and their interactions with Leishmania parasites

Blood-sucking arthropods transmit a variety of human pathogens acting as disseminators of the so-called vector-borne diseases. Leishmaniasis is a spectrum of diseases caused by different Leishmania species, transmitted quasi worldwide by sand flies. However, whereas many laboratories focus on the disease(s) and etiological agents, considerably less study the respective vectors. In fact, information on sand flies is neither abundant nor easy to find; aspects including basic biology, ecology, and sand-fly-Leishmania interactions are usually reported separately. Here, we compile elemental information on sand flies, in the context of leishmaniasis. We discuss the biology, distribution, and life cycle, the blood-feeding process, and the Leishmania-sand fly interactions that govern parasite transmission. Additionally, we highlight some outstanding questions that need to be answered for the complete understanding of parasite–vector–host interactions in leishmaniasis.

In this review, numerous aspects of sand flies as vectors of Leishmania parasites—from biology to the vector parasite interactions—are discussed.

Topical treatment of cutaneous leishmaniasis lesions using quercetin/ Artemisia-capped silver nanoparticles ointment: Modulation of inflammatory response

Leishmaniasis is a major health issue that affects people all over the world, producing considerable morbidity and mortality in Asia, Africa, and the Americas, and existing treatments have significant side effects. Nowadays, the development of nanoscale materials such as biogenic silver nanoparticles has attracted much medical attraction. In this study, AgNPs were synthesized from leaf extract of Artemisia aucheri. Biosynthesized AgNPs were analyzed by UV-visible spectroscopy, dynamic light scattering and zeta potential, fourier transform infrared spectroscopy and field emission scanning electron microscopy. Biosynthesized AgNPs were examined for anti-leishmanial and antibacterial activity. The in vivo study was conducted by treating the L. major infected BALB/c mice with quercetin/ artemisia-capped silver nanoparticles ointment topically for 21 consecutive days. The in vitro and in vivo results showed that the ointment containig quercetin/artemisia-capped silver nanoparticles have the potential to decrease inflammatory responses and enhance wound healing with granulation tissue formation compared to the untreated group. Therefore, biogenic nanoparticles are safe, eco-friendly, and easy to synthesize and could be considered as an alternative regimen for treatment of L. major.

Spatial modeling of zoonotic cutaneous leishmaniasis with regard to potential environmental factors using ANFIS and PCA-ANFIS methods

This study compares two adaptive neuro-fuzzy inference system (ANFIS) and principal component analysis (PCA)-ANFIS techniques for spatial modeling and forecasting of zoonotic cutaneous leishmaniasis (ZCL) cases in rural districts of Golestan province, Iran. We collected and prepared data on ZCL cases and climatic, topographic, vegetation, and human population factors. By applying the PCA algorithm, the parameters affecting the ZCL incidence were decomposed into principal components (PCs), and their dimensions were reduced. Then, PCs were used to train the ANFIS model. To evaluate the proposed approaches in model assessment phase, we used test data in 2016. In this phase, we showed that PCA-ANFIS model with values ​​of R² = 0.791, MAE = 0.681, RMSE = 0.904 compared to ANFIS model with values ​​of R² = 0.705, MAE = 0.827, RMSE = 1.073 has better performance in prediction of the ZCL cases. Actual and predicted maps of ZCL cases in 2016 by both models demonstrated that the high-risk regions of the disease are located in the northeastern, northern parts, and some central rural districts of Golestan province. Sensitivity analysis of the ANFIS model showed that population, vegetation, average wind speed, elevation, and average soil temperature, respectively, are the most significant factors in predicting the ZCL cases. The findings indicated the importance of machine learning (ML) techniques (ANFIS and PCA-ANFIS) in medical geography studies. By using these approaches, with less cost and shorter time, high-risk areas of diseases can be predicted, and the most effective factors on the spatial prediction of diseases can be identified. Public health policymakers can use these useful tools to control and prevent the disease and to allocate resources to disease-prone areas.

Host–Pathogen Interaction in Leishmaniasis: Immune Response and Vaccination Strategies

Leishmaniasis is a zoonotic and vector-borne infectious disease that is caused by the genus Leishmania belonging to the trypanosomatid family. The protozoan parasite has a digenetic life cycle involving a mammalian host and an insect vector. Leishmaniasisis is a worldwide public health problem falling under the neglected tropical disease category, with over 90 endemic countries, and approximately 1 million new cases and 20,000 deaths annually. Leishmania infection can progress toward the development of species–specific pathologic disorders, ranging in severity from self-healing cutaneous lesions to disseminating muco-cutaneous and fatal visceral manifestations. The severity and the outcome of leishmaniasis is determined by the parasite’s antigenic epitope characteristics, the vector physiology, and most importantly, the immune response and immune status of the host. This review examines the nature of host–pathogen interaction in leishmaniasis, innate and adaptive immune responses, and various strategies that have been employed for vaccine development.

Domestic mammals as reservoirs for Leishmania donovani on the Indian subcontinent: Possibility and consequences on elimination

Leishmania donovani is the causative agent of historically anthroponotic visceral leishmaniasis (VL) on the Indian subcontinent (ISC). L. donovani is transmitted by the sand fly species Phlebotomus argentipes. Our collaborative group and others have shown that sand flies trapped outside in endemic villages have fed on cattle and dogs in addition to people. Domestic animals are reservoirs for L. donovani complex spp., particularly L. infantum, in other endemic areas. Multiple studies using quantitative PCR or serological detection methods have demonstrated that goats, cattle, rats and dogs were diagnostically positive for L. donovani infection or exposure in eastern Africa, Bangladesh, Nepal and India. There is a limited understanding of the extent to which L. donovani infection of domestic animals drives transmission to other animals or humans on the ISC. Evidence from other vector-borne disease elimination strategies indicated that emerging infections in domestic species hindered eradication. The predominant lesson learned from these other situations is that non-human reservoirs must be identified, controlled and/or prevented. Massive efforts are underway for VL elimination on the Indian subcontinent. Despite these herculean efforts, residual VL incidence persists. The spectre of an animal reservoir complicating elimination efforts haunts the final push towards full VL control. Better understanding of L. donovani transmission on the Indian subcontinent and rigorous consideration of how non-human reservoirs alter VL ecology are critical to sustain elimination goals.

Could combination chemotherapy be more effective than monotherapy in the treatment of visceral leishmaniasis? A systematic review of preclinical evidence

From a systematic review framework, we assessed the preclinical evidence on the effectiveness of drug combinations for visceral leishmaniasis (VL) treatment. Research protocol was based on the PRISMA guideline. Research records were identified from Medline, Scopus and Web of Science. Animal models, infection and treatment protocols, parasitological and immunological outcomes were analysed. The SYRCLE's (SYstematic Review Center for Laboratory Animal Experimentation) toll was used to evaluate the risk of bias in all studies reviewed. Fourteen papers using mice, hamster and dogs were identified. Leishmania donovani was frequently used to induce VL, which was treated with 23 drugs in 40 different combinations. Most combinations allowed to reduce the effective dose, cost and time of treatment, in addition to improving the parasitological control of Leishmania spp. The benefits achieved from drug combinations were associated with an increased drug's half-life, direct parasitic toxicity and improved immune defences in infected hosts. Selection, performance and detection bias were the main limitations identified. Current evidence indicates that combination chemotherapy, especially those based on classical drugs (miltefosine, amphotericin B antimony-based compounds) and new drugs (CAL-101, PAM3Cys, tufisin and DB766), develops additive or synergistic interactions, which trigger trypanocidal and immunomodulatory effects associated with reduced parasite load, organ damage and better cure rates in VL.