From Infection to Death: An Overview of the Pathogenesis of Visceral Leishmaniasis

Comprehensive insights into leishmaniasis: From etiopathogenesis to a novel therapeutic approach

Leishmaniasis is a vector-borne disease caused by protozoan parasites of the genus Leishmania and is transmitted through the bites of infected sandflies. The disease is characterized by a variety of clinical manifestations, from small skin blemishes to large deformable ulcers, classified as cutaneous leishmaniasis (CL), mucocutaneous leishmaniasis (MCL) and disseminated cutaneous leishmaniasis (DCL), as well as severe systemic infections (Kala-Azar or visceral leishmaniasis [VL]), affecting the spleen and liver, along with atypical forms such as lupoid leishmaniasis. As one of the world's most neglected tropical diseases, leishmaniasis threatens more than 1 billion people globally, with 12 million currently affected and <1.3 million new cases reported annually. This review provides comprehensive insights into the etiopathogenesis of leishmaniasis and explores the complex life cycle of parasites and their interactions with host immune responses. A systematic literature search was conducted across databases such as PubMed, Google Scholar, and Scopus via keywords such as "Leishmaniasis," "etiopathogenesis," "cutaneous leishmaniasis," "visceral leishmaniasis," and "Novel therapeutic approaches." Relevant studies published after 2015 were critically analyzed to present the current understanding of the disease mechanisms involved. It also highlights the current treatment landscape, emphasizing the emergence of drug resistance and the need for novel therapeutic approaches. Recent advancements in drug delivery systems, such as nanoparticle formulations, have shown promise for enhancing treatment efficacy and reducing toxicity. Additionally, integrated control measures, such as vector management and public education, are crucial for mitigating disease spread. This overview underscores the urgent need for continued research and innovation to combat this neglected tropical disease effectively.

Diagnostic performance of a novel point-of-care test for the diagnosis of visceral leishmaniasis in Sudan: A Comparative Accuracy Study

METHODS

This study enrolled 107 VL suspects who attended a health centre in Gedaref between October 2022 and June 2023. Diagnostic accuracy was assessed by comparing the performance of the new index test (INgezimLeishma-CROM) with the comparator test (IT-LEISH) and parasitological examination as reference standard.

RESULTS

Of 107 VL suspects screened by parasitological examination, 77 VL patients were smear positive and 30 were smear negative. Independent serological testing of these patients using INgezim Leishma-CROM showed a sensitivity of 98.7% [95% CI 92.23-99.97] and specificity of 92.5% [95% CI 75.71-99.09]. For IT-LEISH, both sensitivity [95% CI 84.39-97.20] and specificity [95% CI 75.71-99.09] were 92.5%. INgezim Leishma-CROM demonstrated increased diagnostic accuracy (97.2%) compared to IT-LEISH RDT (92.5%). Both RDTs gave positive results in 2 cases from the smear negative group that were previously treated for VL. All other non-VL cases (malaria, typhoid, brucellosis) were negative in both RDTs, showing 100% specificity, while VL patients co-infected with malaria were positive in both tests. Within the smear-negative group, 3 VL symptomatic cases that had been previously treated but still show clinical signs were all positive with INgezim Leishma-CROM but only 2 cases were positive with IT-LEISH.

Synthesis and in vitro antitrypanosomatid activity of novel 5-nitroindole-rhodanine conjugates

AIM

Trypanosomatid diseases, leishmaniasis and trypanosomiasis are vector-borne parasitic diseases that can cause death and catastrophic economic losses for millions of people. The growing resistance of trypanosomatid parasites to current treatments highlights the urgent need for new therapeutic agents. This study explored 5-nitroindole-rhodanine conjugates to identify promising new compounds with the potential for future development as antitrypanosomatid treatments.

MATERIALS AND METHODS

The conjugates were synthesized in a multi-step process and evaluated in vitro for antileishmanial activity against Leishmania (L.) donovani and L. major strains. Cytotoxicity was assessed on Vero and THP-1 cells. Due to the taxonomic relation to Trypanosoma spp. the compounds were also screened for in vitro activity against species that cause zoonotic trypanosomiasis.

RESULTS AND CONCLUSION

Several hits were found with leishmanicidal activity against both L. donovani and L. major strains. Of these, 3d was identified as a potential early lead that exhibited nanomolar cidal activity against L. major, and greater selectivity than the reference drug amphotericin B. However, the compounds did not have similar activity levels against Trypanosoma spp. Hence, these compounds should be further investigated for their mechanism of action and in vivo antileishmanial activity to determine their potential as a leishmaniasis treatment.

TGF-beta plays dual roles in immunity and pathogenesis in leishmaniasis

Transforming growth factor-beta (TGF-β), displaying a dual role in immunosuppression and pathogenesis, has emerged as a key regulator of anti-leishmanial immune responses. In Leishmania infections, TGF-β drives immune deviation by enhancing regulatory T-cell (T-reg) differentiation and inhibiting macrophage activation, suppressing critical antiparasitic responses. This cytokine simultaneously promotes fibroblast proliferation, extracellular matrix production, and fibrosis in infected tissues, which aids in wound healing but impedes immune cell infiltration, particularly in visceral leishmaniasis, where splenic disorganization and compromised immune access are notable. In conjunction with IL-6, TGF-β modulates pathogenic Th17 responses which intensify inflammatory damage and disrupt tissue architecture. While TGF-β's immunosuppressive actions enable parasite persistence, its role in maintaining tissue integrity introduces therapeutic potential. Targeted modulation of TGF-β signaling, through selective inhibitors of TGF-β receptors or signaling intermediates, has the potential to enhance parasite clearance while minimizing immunopathology. Experimental studies suggest that phase-specific intervention strategies may allow for controlled immunostimulation or fibrosis reduction, enhancing host resistance without incurring inflammatory injury. This review discusses the intricate role of TGF-β in orchestrating immune deviation, fibrosis, and pathogenesis in leishmaniasis, proposing novel therapeutic avenues for selective modulation of TGF-β pathways to restore host immunity.

Impact of Marasmic Malnutrition on Visceral Leishmaniasis: Progression and Treatment Efficacy in a Murine Model

BACKGROUND/OBJECTIVES

Malnutrition and visceral leishmaniasis are major public health problems that are responsible for millions of deaths across many countries. Leishmaniasis development and progression are associated with the host immune status. In this context, malnutrition can directly affect the course of leishmaniasis, impairing several components of the immune system. Moreover, malnutrition directly interferes with the tropism of Leishmania in organs, affecting host susceptibility. Therefore, this work aimed to evaluate the influence of nutritional status on the establishment, progression, and treatment of Leishmania infantum infection in malnourished and refed mice.

METHODS

BALB/c mice were fed either a control or restricted diet, infected with L. infantum promastigotes, and treated with meglumine antimoniate, the standard drug for treating visceral leishmaniasis. The effects of infection were evaluated through limiting dilution analysis (LDA).

RESULTS

Compared with control mice, malnourished and refed mice presented a lower parasitic load in the spleen, which correlated with spleen atrophy, and the refeeding process partially reversed but did not fully rescue the infection status. Both groups presented a high parasitic load in the liver. Marasmic malnutrition appeared to impair the efficacy of leishmaniasis treatment; however, the refed groups exhibited a robust decrease in the parasite load, which was comparable to that in the control group subjected to treatment.

CONCLUSIONS

Our data suggested that marasmic malnutrition affects the establishment and progression of Leishmania infection, in addition to reducing the efficacy of standard treatment. Furthermore, the refeeding intervention used did not fully reverse the observed effects. These findings highlight the potential importance of nutritional interventions in the clinical management of visceral leishmaniasis in malnourished populations.

Evaluation of SB-83, a 2-amino-thiophene derivative, against Leishmania species that cause visceral leishmaniasis

Visceral leishmaniasis is a systemic disease that affects various internal organs and represents the most severe and fatal form of leishmaniasis. Conventional treatment presents significant challenges, such as prolonged management in hospital settings, high toxicity, and an increasing growing number of cases of resistance. In previous studies, our research group demonstrated the effective and selective activity of the 2-amino-thiophene derivative SB-83 in preclinical models of cutaneous leishmaniasis. Given the urgent need for new therapeutic alternatives for visceral leishmaniasis, and considering our previous promising results for SB-83, this study investigated the antileishmanial activity of the compound on the etiological agents of visceral leishmaniasis. SB-83 demonstrated efficacy in inhibiting the growth of promastigote forms of Leishmania (Leishmania) infantum (IC50 = 7.46 µM) and Leishmania (Leishmania) donovani (IC50 = 9.84 µM). In the cytotoxicity evaluation, in RAW 264.7 macrophages, the compound revealed a CC50 = 52.27 µM, being more toxic to the parasite, and respective selectivity indices (SI) of 7 and 5.31 against the previously mentioned species. Atomic force microscopy analysis showed that the compound causes alterations in surface roughness, formation of englobulations, and accumulation of lipids, all of which are indicative of cell death by apoptosis. This was confirmed by flow cytometry, which showed an increase in the number of cells labeled with Annexin V-FITC+/IP-, indicating apoptosis. SB-83 showed even greater efficacy against intramacrophagic amastigote forms (EC50 = 2.91 µM), which was associated with structural changes, such as increased lysosomal volume, and cellular mechanisms, including elevated levels of cytokines TNF-α and IL-12, reactive oxygen and nitrogen species, and reduced levels of cytokines IL-10 and IL-6, as well as decreased arginase activity. The results allow us to conclude that the 2-amino-thiophene derivative SB-83 is a promising compound for development of new treatments against visceral leishmaniasis.

First documented case of visceral leishmaniasis with rare colonic involvement in an immunocompetent adult in Slovakia

BACKGROUND

This article presents the first documented case of visceral leishmaniasis in an adult patient in Slovakia, with an unusual involvement of the colon. Leishmaniasis is a tropical parasitic infection transmitted by sandflies, predominantly occurring in developing countries.

CASE PRESENTATION

The patient was a 57-year-old woman without comorbidities or immunocompromising conditions. The clinical presentation included non-specific symptoms such as prolonged fever, marked weakness, hepatosplenomegaly, and generalized lymphadenopathy. The diagnosis was established based on histopathological examination and bone marrow PCR, which confirmed the presence of Leishmania infantum amastigotes. After initiating treatment with amphotericin B, the patient's condition improved, but a relapse occurred shortly thereafter, presenting with colonic involvement-an extremely rare occurrence in immunocompetent patients. The diagnosis of relapse was confirmed by repeated histopathological examination and molecular analysis. Treatment was re-initiated with an extended regimen of amphotericin B and additional supportive therapy.

CONCLUSION

This case highlights the importance of early diagnosis and targeted treatment of visceral leishmaniasis, even in non-endemic areas of the world. It emphasizes the need to consider this diagnosis in the differential diagnosis of patients with unexplained febrile conditions and hepatosplenomegaly, as the clinical presentation can often mimic various other infectious diseases or hematological malignancies, significantly complicating the diagnostic process.

Molecular characterization of Leishmania infection in canine

Background

Canine leishmaniasis is an infectious protozoan disease transmitted by sand fly bites. The parasite infects the macrophages of vertebrates during the amastigote stage.

Aim

This study aimed to detect the causative species for infections between dogs with Leishmania in Iraq and to determine the relationship between isolates that infect Iraqi animals and other animals worldwide.

Methods

Fifty dogs of various breeds, ranging from 1 month to 7 years old of both sexes. Then, blood samples were collected from the cephalic vein into an EDTA tube; DNA was extracted using a commercial kit. Afterward, conventional PCR was performed using universal primers to detect 18S in Leishmania.

Results

Most dog infections were caused by Leishmania infantum. The age of the infected dogs ranged from a few months to 7 years. Our results indicate that most infections with Leishmiania spp. occurred between older males and younger females. Most dogs were asymptomatic, and a small percentage exhibited clinical signs, such as skin lesions, rough coats, hair loss, and onychogryphosis. To confirm the results and gain insight into the origin of the positive L. infantum isolates, 10 samples were sequenced. Interestingly, L. infantum isolates were typical of those recorded in Brazil, France, and the USA, except for one isolate, which was slightly different from the detected isolates. Therefore, our results showed that most infections were between older males rather than younger females, and the DNA sequencing results indicated that only 1 isolate out of 10 had a different demographic origin.

Conclusion

Dogs in this study were infected mainly with L. infantum without any clinical signs; most isolates resemble those recorded in Brazil, France, and the USA.

Visceral leishmaniasis related secondary haemophagocytic syndrome: A case report

Visceral leishmaniasis (VL) is a parasitic disease that can trigger haemophagocytic syndrome (HPS), making its prompt diagnosis crucial. The application of metagenome next-generation sequencing (mNGS) provides a rapid diagnostic approach, particularly for patients with negative bone marrow aspiration results. We present here, a case of a male patient in his early 50s who presented with fever and abdominal pain. Routine examinations failed to identify its specific cause. However, diagnosis through mNGS helped prevent a potentially fatal outcome.

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.

Insecticide-impregnated dog collars for the control of visceral leishmaniasis: evaluation of the susceptibility of field Lutzomyia longipalpis populations to deltamethrin

BACKGROUND

Visceral leishmaniasis (VL) is a zoonotic disease caused by Leishmania infantum and transmitted by the sand fly Lutzomyia longipalpis. Dogs are the major domestic reservoir of L. infantum. To prevent the spread of the disease, dog collars impregnated with 4% deltamethrin have been effectively used in VL endemic areas. However, this approach may contribute to the emergence of insecticide resistance in sand flies. Therefore, it is important to characterize the susceptibility of different populations of Lu. longipalpis to deltamethrin in areas where insecticide-impregnated dog collars are used.

METHODS

Six field sand fly populations from Brazil were exposed to deltamethrin in CDC bottle bioassays at the diagnostic doses (DD) of 21.9 μg/bottle and 30 μg/bottle. For the dose-response (DR) experiments, doses of 1, 3, 5, 7, 9 and 11 μg/bottle of deltamethrin were used to impregnate bottles; control group bottles were impregnated with acetone only. Each bottle contained an average of 20 sand flies, both male and female, and they were exposed to either deltamethrin or acetone for 60 min.

RESULTS

Based on the DD of 21.9 μg/bottle, three populations were susceptible to deltamethrin. In contrast, two populations collected from the states of Ceará and Minas Gerais exhibited mortality rates of 94.9% and 95.7%, indicating possible resistance, and one population from the state of Ceará showed resistance, with a mortality rate of 87.1%. At the DD of 30 μg/bottle, two populations from the states of Ceará and Piauí showed possible resistance, while the other four populations were susceptible. The resistance ratio (RR50) ranged from 2.27 to 0.54, and RR95 ranged from 4.18 to 0.33, indicating a low resistance intensity.

CONCLUSIONS

This study established a DD for Lu. longipalpis using the CDC bottle bioassay. We found that Lu. longipalpis populations in three Brazilian states where insecticide-impregnated dog collars were used for VL control were susceptible to deltamethrin. However, one population in Ceará State was classified as resistant to deltamethrin. These results contribute to the current knowledge on sand fly resistance and surveillance, and highlight the need for a better understanding of the resistance mechanisms of Lu. longipalpis in areas where insecticide-impregnated dog collars have been widely used.

Possibility of re-purposing antifungal drugs posaconazole & isavuconazole against promastigote form of Leishmania major

Background & objectives The emergence of drug resistance in leishmaniasis has remained a concern. Even new drugs have been found to be less effective within a few years of their use. Coupled with their related side effects and cost-effectiveness, this has prompted the search for alternative therapeutic options. In this study, the Computer Aided Drug Design (CADD) approach was used to repurpose already existing drugs against Leishmania major. The enzyme lanosterol 14-alpha demethylase (CYP51), in L. major, was chosen as the drug target since it is a key enzyme involved in synthesizing ergosterol, a crucial component of the cell membrane. Methods A library of 1615 FDA-approved drugs was virtually screened and docked with modeled CYP51 at its predicted binding site. The drugs with high scores and high affinity were subjected to Molecular Dynamics (MD) simulations for 100 ns. Finally, the compounds were tested in vitro using an MTT [3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide] assay against the promastigotes of L. major. Results Computational screening of FDA-approved drugs identified posaconazole and isavuconazole as promising candidates, as both drugs target the CYP51 enzyme in fungi. Molecular dynamics (MD) simulations demonstrated that both drugs form stable complexes with the target enzyme. In vitro studies of posaconazole and isavuconazole against promastigotes of L. major demonstrated significant efficacy, with IC50 values of 2.062±0.89 µg/ml and 1.202±0.47 µg/ml, respectively. Interpretation & conclusions The study showed that the existing FDA-approved drugs posaconazole and isavuconazole can successfully be repurposed for treating L. major by targeting the CYP51 enzyme, demonstrating significant efficacy against promastigotes.

Hematological picture of pediatric Sudanese patients with visceral leishmaniasis and prediction of leishmania donovani parasite load

BACKGROUND

Visceral leishmaniasis (VL) is a systemic protozoan infection caused by Leishmania donovani (L. donovani) and transmitted by sand flies, causing macrophage invasion in the liver, spleen, and bone marrow. Diagnosis of VL is currently based on clinical signs, symptoms, and specific in-vitro markers and bone marrow investigations. However, VL's specific hematological and bone marrow manifestation in Sudanese pediatric patients is not well studied.

AIM

To examine the blood and bone marrow characteristics in pediatric patients from Sudan who have VL.

METHODS

This is a retrospective hospital-based study with a sample of 107 consecutive Sudanese pediatric patients. The data focused on hematological and bone marrow results. We included only the completed records of the pediatric patients with VL in the Tropical Disease Teaching Hospital in Khartoum, Sudan from the period of 2016 to 2020.

RESULTS

The majority of pediatric patients included in this study are below 5-years-old (n = 59, 55.2%). Moreover, anemia, thrombocytopenia, and leukopenia were among the prevalent characteristics in the population under study. To further analyze the data, we developed a machine learning model using boosted forest algorithms to predict L. donovani parasites load, with a mean accuracy of 0.88 for the training dataset and an accuracy of 0.46, 0.50, and 0.74 for mild, moderate, and severe L. donovani parasite load in the validation dataset.

CONCLUSION

This study shows that the most common bone marrow change among Sudanese VL children was increased chronic inflammatory cells (n = 88, 82.2%) with present macrophage hemophagocytes (n = 103, 96.3%). While anemia and thrombocytopenia were the most common hematological changes. These results will hopefully lead to an early diagnosis and hence better management for Sudanese pediatric patients with suspected VL.

Integrated subtractive genomics and structure-based approach to unravel the therapeutic drug target of Leishmania species

Leishmaniasis is a complex vector-borne disease caused by intracellular protozoan parasites of the Leishmania genus. It presents a significant public health challenge in tropical and subtropical regions globally. As resistance to treatment increases, managing and controlling Leishmaniasis becomes more challenging, necessitating innovative approaches. To address this challenge, our study utilized subtractive genomics and structure-based approaches to identify common drug targets and combat antimicrobial resistance (AMR) across five Leishmania species strains. The subtractive genomics approach unraveled Glutamate Dehydrogenase (GDH) as a promising drug target for treating Leishmania infections. The investigation considered established methodologies observed in analogous studies, orthologous group, and druggability tests. Multiple sequence alignment revealed conserved sequences in GDH, while phylogenetic tree analysis provided insights into the evolutionary origin and close relationships of GDH across Leishmania species. Conserved sequences in GDH along with its function in pathogenicity provided insights into the close relationships of GDH across Leishmania species. Using a structure-based approach, our study showed the molecular interactions between GDH and three ligands-Bithionol, GW5074, and Hexachlorophene-through molecular docking and 100 ns molecular dynamics (MD) simulations. GW5074 exhibited a significant affinity for GDH, as indicated by stable RMSD values, a more compact conformation, and a higher number of hydrogen bonds than Bithionol. MMPBSA analysis confirmed the superior binding energy of the GW5074-GDH complex, emphasizing its potential as a potent ligand for drug development. This comprehensive analysis identified GW5074 as a promising candidate for inhibiting GDH activities in Leishmania species, contributing to the development of effective therapeutics against Leishmania infections.

Parasites of the liver: A global problem?

Parasitic liver diseases can be caused by trematodes, cestodes, nematodes, and protozoa. This pathology is significant because millions of people in different parts of the world have liver parasites, which can manifest themselves in the development of inflammation, liver cysts, cholecystitis, cholelithiasis, pancreatitis and liver cirrhosis that are often threatening their lives. The International Agency for Research on Cancer considers three species of trematodes, Schistosoma haematobium, Opisthorchis viverrini and Clonorchis sinensis, to be carcinogens. Complex modern examination methods, in some cases including extensive screening of large populations, are required for diagnosing liver parasites. Treatment of parasitic liver diseases is differentiated and can involve a combination of surgical and therapeutic measures. There is no doubt that the clinical and epidemiological scale allows one to regard parasitic liver diseases as a global healthcare problem.

A breath of fresh air: impact of insect-borne protozoan parasites on the respiratory system

The protozoan parasites Plasmodium, Leishmania, and Trypanosoma are transmitted by hematophagous insects and cause severe diseases in humans. These infections pose a global threat, particularly in low-resource settings, and are increasingly extending beyond the current endemic regions. Tropism of parasites is crucial for their development, and recent studies have revealed colonization of noncanonical tissues, aiding their survival and immune evasion. Despite receiving limited attention, cumulative evidence discloses the respiratory system as a significant interface for host-pathogen interactions, influencing the course of (co)infection and disease onset. Due to its pathophysiological and clinical implications, we emphasize that further research is needed to better understand the involvement of the respiratory system and its potential to improve prevention, diagnosis, treatment, and interruption of the chain of transmission.

Prevalence of hepatitis B and C virus infections among visceral leishmaniasis patients: a systematic review and meta-analysis

Background

Visceral leishmaniasis (VL) patients are at high risk of acquiring hepatitis B virus (HBV) and hepatitis C virus (HCV) infections during multiple injections and the anti-leishmanial treatment possesses a potential hepatotoxic effect. This systematic review and meta-analysis determined the pooled prevalence of HBV and HCV infections in VL patients.

Methods

This study was registered in the International Prospective Register of Systematic Reviews (PROSPERO), with the assigned number CRD42024516889, and conducted as per the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A literature search was performed using PubMed, Medline, EMBASE, Google Scholar, Web of Science, and Science Direct databases. Data were extracted using Microsoft Excel and analyzed using STATA version 11.0 software. A random-effects model was used to estimate the pooled effect size of outcome variables across studies with a 95% confidence interval and was displayed in a forest plot. The I 2 statistic was used to check for heterogeneity. The presence of publication bias was determined using a funnel plot and Egger's test with a p value <0.05 evidence of statistically significant bias.

Results

Among 216 retrieved records, seven studies were eligible for systematic review and meta-analysis. A total of 937 VL patients were examined, revealing that 105 and 93 were infected with HBV and HCV, respectively. The pooled prevalence of HBV was 16.15% (95% CI: -4.10 to 36.39), with a significant heterogeneity (I 2 = 91.4%, p < 0.001). The combined prevalence of HCV was 13.74% (95% CI: 1.32-26.16, I 2 = 71.6%, p = 0.003). The funnel plot (symmetry), and Egger's test in both HBV (p value = 0.650) and HCV (p value = 0.841) revealed no publication bias. In subgroup analysis, high HBV and HCV prevalence was detected in Sudan; 20.64% (95% CI: -13.60 to 54.88) and India; 18.26% (95% CI: -0.40 to 36.92%), respectively.

Conclusion

This study revealed a high prevalence of both HBV and HCV infections in VL patients. In subgroup analysis, the prevalence of HBV and HCV was high in Sudan and India, respectively. Therefore, screening of VL patients for HBV and HCV, vaccination of VL patients in endemic regions, and collaboration between kala-azar and hepatitis elimination programs are required.

Systematic review registration

https://www.crd.york.ac.uk/prospero/export_details_pdf.php#page=1.00&gsr=0, identifier: CRD42024516889.

Cytokine profiles, blood parasite load and clinical features of visceral leishmaniasis in West Pokot County, Kenya

Visceral leishmaniasis (VL) is a severe infectious disease caused by protozoan parasites of the Leishmania donovani complex. Blood cytokine concentrations in VL patients can inform us about underlying immunopathogenesis and may serve as a biomarker for treatment effectiveness. However, cytokine levels have not yet been studied in VL patients from Kenya, where case load is high. This study measured the serum cytokine profile, blood parasite load and clinical and haematological features of VL patients from West Pokot County, Kenya, over the course of treatment with sodium stibogluconate and paromomycin (SSG-PM). VL patients recruited at the hospital presented with splenomegaly and weight loss, and frequently had pancytopenia and anaemia. Median Leishmania parasite load in blood, determined with real-time polymerase chain reaction, was 2.6 × 104 parasite equivalents mL−1. Compared to endemic healthy controls, serum interferon gamma (IFN-γ), interleukin 5 (IL-5), IL-6, IL-10, IL-12p70, IL-17A and IL-27 were significantly elevated in untreated VL patients. Severe VL was associated with higher IL-10 and lower IFN-γ levels. After 17 daily injections with SSG-PM, disease symptoms disappeared, leukocyte and thrombocyte counts significantly increased, and blood parasite load decreased to undetectable levels in all VL patients. There was a significant decrease in IL-10 and IL-6, whereas IL-17A levels increased; the remaining cytokines showed no significant concentration change during treatment. In conclusion, the results suggest that SSG-PM treatment of VL patients from West Pokot was effective. Moreover, both inflammatory and regulatory immune responses appeared to decrease during treatment, although the increase in IL-17A could reflect a partial continuation of immune activation.

An integrated analysis of the structural changes and gene expression of spleen in human visceral leishmaniasis with and without HIV coinfection

The spleen plays a pivotal role in the pathogenesis of visceral leishmaniasis. In severe forms of the disease, the spleen undergoes changes that can compromise its function in surveilling blood-circulating pathogens. In this study, we present an integrated analysis of the structural and gene expression alterations in the spleens of three patients with relapsing visceral leishmaniasis, two of whom were coinfected with HIV. Our findings reveal that the IL6 signaling pathway plays a significant role in the disorganization of the white pulp, while BCL10 and ICOSLG are associated with spleen organization. Patients coinfected with HIV and visceral leishmaniasis exhibited lower splenic CD4+ cell density and reduced expression of genes such as IL15. These effects may contribute to a compromised immune response against L. infantum in coinfected individuals, further impacting the structural organization of the spleen.

Targeting Trypanothione Metabolism in Trypanosomatids

Infectious diseases caused by trypanosomatids, including African trypanosomiasis (sleeping sickness), Chagas disease, and different forms of leishmaniasis, are Neglected Tropical Diseases affecting millions of people worldwide, mainly in vulnerable territories of tropical and subtropical areas. In general, current treatments against these diseases are old-fashioned, showing adverse effects and loss of efficacy due to misuse or overuse, thus leading to the emergence of resistance. For these reasons, searching for new antitrypanosomatid drugs has become an urgent necessity, and different metabolic pathways have been studied as potential drug targets against these parasites. Considering that trypanosomatids possess a unique redox pathway based on the trypanothione molecule absent in the mammalian host, the key enzymes involved in trypanothione metabolism, trypanothione reductase and trypanothione synthetase, have been studied in detail as druggable targets. In this review, we summarize some of the recent findings on the molecules inhibiting these two essential enzymes for Trypanosoma and Leishmania viability.

Identification of Leishmania donovani PEX5-PTS1 Interaction Inhibitors through Fluorescence Polarization-Based High-Throughput Screening

Leishmaniasis, an infectious disease caused by pathogenic Leishmania parasites, affects millions of people in developing countries, and its re-emergence in developed countries, particularly in Europe, poses a growing public health concern. The limitations of current treatments and the absence of effective vaccines necessitate the development of novel therapeutics. In this study, we focused on identifying small molecule inhibitors which prevents the interaction between peroxin 5 (PEX5) and peroxisomal targeting signal 1 (PTS1), pivotal for kinetoplastid parasite survival. The Leishmania donovani PEX5, containing a C-terminal tetratricopeptide repeat (TPR) domain, was expressed and purified, followed by the quantification of kinetic parameters of PEX5-PTS1 interactions. A fluorescence polarization-based high-throughput screening assay was developed and small molecules inhibiting the LdPEX5-PTS1 interaction were discovered through the screening of a library of 51,406 compounds. Based on the confirmatory assay, nine compounds showed half maximal inhibitory concentration (IC50) values ranging from 3.89 to 24.50 µM. In silico docking using a homology model of LdPEX5 elucidated that the molecular interactions between LdPEX5 and the inhibitors share amino acids critical for PTS1 binding. Notably, compound P20 showed potent activity against the growth of L. donovani promastigotes, L. major promastigotes, and Trypanosoma brucei blood stream form, with IC50 values of 12.16, 19.21, and 3.06 μM, respectively. The findings underscore the potential of targeting LdPEX5-PTS1 interactions with small molecule inhibitors as a promising strategy for the discovery of new anti-parasitic compounds.

The spleen is the graveyard of CD4+ cells in patients with immunological failure of visceral leishmaniasis and AIDS

BACKGROUND

Visceral leishmaniasis (VL), or kala-azar, is a common comorbidity in patients with AIDS in endemic areas. Many patients continue to experiences relapses of VL despite virological control, but with immunological failure. These patients remain chronically symptomatic with hypersplenism, for example with anemia, leukopenia, and thrombocytopenia, and are at risk of severe co-infection due to low CD4+ count. Therefore, in this study, splenectomized patients with VL and HIV infection were investigated to understand why the CD4+ count fails to recover in these patients, evaluating the importance of spleen mass for hypersplenism and immunological failure.

METHODS

From a retrospective open cohort of 13 patients who had previously undergone splenectomy as salvage therapy for relapsing VL, 11 patients with HIV infection were investigated. This study compared the patients' complete blood cell count (CBC) and CD4+ and CD8+ cell counts before and after splenectomy with respect to spleen weight.

RESULTS

CBC was substantially improved after splenectomy, indicating hypersplenism. However, to the best of our knowledge, this is the first study to show that spleen mass is strongly and negatively correlated with CD4+ cell count (ρ = -0.71, P = 0.015).

CONCLUSIONS

This finding was unexpected, as the spleen is the most extensive lymphoid tissue and T-lymphocyte source. After reviewing the literature and reasoning, we hypothesized that the immunological failure was secondary to CD4+ loss initially by apoptosis in the spleen induced by productive HIV infection and, subsequently, by pyroptosis sustained by parasitic infection in spleen macrophages.