PLoS Neglected Tropical Diseases最新文献

Background: Sphingosine-1-phosphate (S1P) is a bioactive lipid mediator regulating apoptosis, proliferation, and immune responses. While S1Ps presence in Leishmania donovani phagolysosomes has been reported, the role of sphingosine kinases, especially SphK1, in parasite survival and host immune modulation remains underexplored. This study investigates the molecular and functional role of L. donovani SphK1 (LdSphK1) and evaluates the antileishmanial potential of PF-543, a specific SphK1 inhibitor.

Methods: LdSphK1 and human SphK1 (rhSphK1) were cloned, expressed in E. coli, purified, and analyzed by SDS-PAGE. Enzymatic activity and inhibition by PF-543 were assessed using NBD-S1P-based fluorometric assays. Protein-ligand interactions were analyzed using Microscale Thermophoresis (MST) and validated in silico docking studies, which identified key species-specific differences in the inhibitor's active site. Leishmania promastigotes overexpressing LdSphK1 were studied via confocal microscopy, and their viability and infectivity were assessed in vitro. THP-1 macrophages infected with L. donovani were treated with PF-543 alone or with Amphotericin B and analyzed by MTT assay, RT-PCR, Giemsa staining, ELISA and immunoblotting. In vivo efficacy was tested in L. donovani-infected Swiss mice.

Results: rLdSphK1 (~102 kDa) and rhSphK1 (~50 kDa) were enzymatically active and significantly inhibited by PF-543. MST demonstrated specific, measurable binding of PF-543 to both orthologues (KD ~ 29μM under identical experimental conditions). In L. donovani SphK1 overexpressor (LdSphKa) promastigotes, PF-543 inhibited SphK1 activity and reduced parasite infectivity, more than in wildtype L. donovani promastigotes. Notably, PF-543 treatment reduced parasite infectivity in vitro, lowered amastigote load by ~40%, and promoted a pro-inflammatory cytokine shift (↑IL-12, ↑ TNF-α, ↓ IL-10). Inhibition of ceramide synthesis and S1P supplementation revealed that S1P rescues ceramide-induced parasite death, implicating SphK1 in parasite survival. PF-543 and Amphotericin B demonstrated synergistic anti-parasitic effects both in vitro and in vivo, with >90% reduction in parasite burden in mice.

Conclusion: PF-543 exerts moderate direct inhibition of parasite SphK1 while prominently modulating host SphK1-dependent immune and apoptotic pathways, collectively restricting Leishmania survival. Rather than functioning as a parasite-selective inhibitor, PF-543 acts as a dual host-parasite modulator. These findings provide proof-of-concept evidence that simultaneous targeting of sphingolipid signalling in both host and parasite can enhance anti-leishmanial efficacy and support further exploration of SphK-based combination therapeutic strategies.

In the austral summer of 2021-2022, Australia experienced an unprecedented Japanese encephalitis virus (JEV) outbreak, with detections over 3000 km south of previous occurrences. Given the limited knowledge of JEV transmission ecology in Australia, we developed geospatial models of transmission risk to support the public health response. We created time-varying habitat suitability models for suspected mosquito vectors and ardeid hosts using month-scaled occurrence and covariate data from 2000-2023. Ardeid host presence-absence data were obtained from eBird and BirdLife Australia, with habitat suitability estimated using gradient-boosted regression tree models. A national dataset of Culex occurrences was compiled from mosquito surveillance records, literature, and biodiversity databases. Penalised logistic regression was used to model mosquito vector habitat suitability. Vector and host habitat predictions for the outbreak peak in February 2022 were rescaled using JEV infection locations in the public domain to create a combined habitat suitability surface. Our models aligned with detected JEV infections at the continental scale, highlighting transmission suitability across tropical northern Australia and major inland drainage basins in the East. Unlike existing models, we predicted lower suitability along the eastern seaboard, suggesting a delimiting effect of the Great Dividing Range. Our approach provides the most comprehensive and temporally dynamic models for JEV hosts and vectors in Australia, with a significantly larger vector dataset than previous studies. The novel method of rescaling host and vector outputs into a combined surface offers new insights into JEV transmission risk. Favourable conditions were repeated in 2023 with few detected infections, emphasising that JEV ecology in Australia remains poorly understood. This study's results can support improvements in arbovirus surveillance systems, promoting earlier detection of circulating viruses. Increased focus on vector ecology and distributions is crucial for better understanding JEV transmission in Australia.

Noma is a rapidly progressive orofacial gangrene that predominantly affects children living in extreme poverty. Despite its documentation since antiquity and its designation as a World Health Organisation Neglected Tropical Disease in 2023, the microbiological cause of noma remains poorly understood, with no specific organisms confidently identified as definitive aetiological agents. Here, we present the first deep shotgun metagenomic profiling of oral saliva microbiomes from 19 Nigerian children with acute noma. Our analyses of this preliminary study reveal marked microbial dysbiosis in noma microbiomes, with machine learning and multivariate statistical analyses indicating significant enrichment of Treponema, Porphyromonas, and Bacteroides, alongside depletion of Streptococcus and Rothia, as key microbial signatures of noma disease. From the dataset we recovered 40 high-quality Treponema metagenome assembled genomes (MAGs) spanning 19 species, 14 of which were novel. Notably, a novel species designated Treponema sp. A was detected in 15 of the 19 noma participants and was entirely absent from an internationally representative set of healthy saliva metagenomes. Re-analysis of previously published 16S rRNA datasets from children with noma in Niger also revealed Treponema sp. A to be highly prevalent in noma cases but extremely rare in controls. While these findings highlight Treponema, particularly Treponema sp. A, as an organism of interest and a potential contributor to noma pathogenesis, further comprehensive studies will be required to confirm this association and to clarify whether it reflects a causal role and/or is a genuine marker of noma dysbiosis. Additionally, analysis of antimicrobial resistance determinants detected in noma metagenomes revealed concerning levels of resistance to antibiotics commonly used in noma treatment, particularly β-lactams and metronidazole, especially among Prevotella spp. These findings provide the first high-resolution microbial framework for noma and offer a foundation for future research into its pathogenesis and the development of novel diagnostics, therapeutics, and preventive strategies in endemic settings.

Background: Human brucellosis is a neglected zoonosis that can cause anemia, miscarriage and pre-term birth, yet its burden during pregnancy in Uganda is unknown. This study determined the seroprevalence and associated risk factors for brucellosis among pregnant women at a Tertiary Hospital in Uganda.

Methodology: This cross-sectional study was conducted in the antenatal clinic of Kampala International University Teaching Hospital, western Uganda (September-December 2024). Consecutive participants provided sociodemographic and livestock-exposure data and 5 mL of venous blood was drawn. Sera were screened with the Rose Bengal Plate Test; all reactive samples and 10% of non-reactive samples were confirmed with an indirect IgG/IgM ELISA. Multivariable logistic regression identified factors independently associated with seropositivity with significance set at P < 0.05.

Results: Of 207 enrolled women (median gestation = 24 weeks), 29 were ELISA-confirmed seropositive, giving a prevalence of 14.0% (95% CI 9.2-18.8). Independent risk factors were lack of formal education (adjusted odds ratio [aOR] 4.05, 95% CI 1.02-16.01), consumption of fresh milk or under-cooked meat (aOR 5.70, 95% CI 1.94-16.76), frequent contact with animal manure (aOR 3.29, 95% CI 1.29-8.47) and rearing livestock at home (aOR 3.75, 95% CI 1.36-10.32).

Conclusions: One in seven pregnant women in this mixed livestock-human ecosystem showed evidence of brucellosis, far above the WHO elimination threshold. Integrating RBPT-based screening into routine antenatal care, promoting milk pasteurization and safe meat preparation, improving manure handling and strengthening herd vaccination through One-Health collaboration could reduce maternal infection and adverse pregnancy outcomes in similar smallholder settings.

Background: Arboviruses represent a diverse group of pathogens transmitted by arthropod vectors. Within Haiti, arboviruses responsible for previous outbreaks include dengue virus, Zika virus, and chikungunya virus. Recent security concerns within Haiti have interrupted broader surveillance efforts, creating challenges for public health agencies tasked with monitoring for vector-borne diseases. In this study, we aimed to better understand circulating arboviruses within Haiti using nucleic acids stored in discarded malaria rapid diagnostic tests (RDTs).

Methodology/principal findings: RDTs were collected between 2021-2023 from febrile patients presenting to health care centers throughout the Sud and Ouest Departments of Haiti. Test strips were removed from the RDT cassettes, and total nucleic acid was extracted. Samples were initially tested for sample integrity using a human RNase P real-time PCR assay, followed by a flavivirus spp. real-time PCR assay. A total of 52 RDTs tested positive by the flavivirus spp. assay, and an additional 21 were indeterminant. Testing all flavivirus spp. positive and indeterminant samples with a DENV quadraplex assay resulted in 68 samples testing positive for DENV-3. All samples testing positive for DENV-3 were collected in 2023. NGS sequencing and subsequent phylogenetic analysis demonstrated high sequence similarity to sequences published from the Caribbean region between 2022-2023. A subset of the flavivirus negative RDTs were tested using alphavirus spp. (n = 517) and Oropouche virus (n = 293) real-time RT-PCR assays. No samples tested positive using either the alphavirus spp. (0/517) or Oropouche virus (0/293) assays.

Conclusions/significance: These results demonstrate the context-specific utility of discarded malaria RDTs for remote arbovirus surveillance among febrile patients, with potential for viral characterization. The exclusive finding of DENV-3 within these samples is concordant with the DENV-3 outbreak that was observed throughout the Americas in 2023. As political insecurity continues within Haiti, malarial RDTs represent an important tool for high level surveillance of novel public health threats.

Background: HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a spastic spinal cord-related paralysis that is caused by a human T-lymphotropic virus type 1 infection. Common symptoms of HAM/TSP include gait disorder, bladder disturbance, constipation, and sensory symptoms. Because no curative treatment exists, individuals with HAM/TSP have to self-manage their chronic condition. Although patients with HAM/TSP have unique self-management strategies owing to their complex backgrounds, limited information is available on how they self-manage their chronic conditions. This study aimed to explore the self-management strategies of patients with HAM/TSP in Japan.

Methods: Using semi-structured interviews and an open-ended questionnaire, data were collected from seven participants with HAM/TSP. Interviews were transcribed verbatim. Data analysis was conducted using a qualitative content analysis method to identify categories that describe the self-management strategies of people with HAM/TSP.

Findings: Six core categories of self-management strategies of people with HAM/TSP were identified: "Attempting to maintain body functions", "Acquiring new ways to complement body functions", "Engaging to maintain an independent daily life", "Ensuring a specialized treatment environment for HAM/TSP", "Taking control of HAM/TSP", and "Moving forward as people with HAM/TSP.".

Conclusions: The self-management strategies of people with HAM/TSP are affected by three characteristics of HAM/TSP: the lack of an established curative treatment, the low social awareness of the disease, and its infectious nature. This study highlights the need for personalized educational strategies and accessible support for the development of self-management skills.

Paracoccidioidomycosis (PCM) is a systemic fungal infection endemic to Latin America, especially Brazil, where it is considered a neglected occupational disease. Caused by Paracoccidioides spp., PCM presents a wide spectrum of clinical manifestations, ranging from localized to severe disseminated forms. This heterogeneity suggests that host-related factors, including genetic background, may influence disease development. Genetic susceptibility to infectious diseases is key to understanding differences in immune responses. In PCM, variants in immune-related genes such as cytokines and pattern recognition receptors may modulate susceptibility and disease progression. This study aimed to review the literature on the association between single nucleotide variants (SNVs) PCM susceptibility, severity, and clinical outcomes. A systematic review followed PRISMA guidelines, searching databases like MEDLINE (PubMed), Cochrane Library, LILACS, SciELO, Web of Science, and Google Scholar. Keywords related to "Paracoccidioidomycosis" and "SNVs" were used. The review included studies on SNVs and PCM susceptibility. The quality of the evidence was assessed with the Cochrane and Joanna Briggs Institute risk of bias tool. We also performed a meta-analysis of studies utilizing identical SNVs. This study is registered on PROSPERO, number CRD42025646417. Two SNVs, Interleukin 10 (IL10) and Vitamin D Receptor (VDR) showed a significant association in individual analyses, but none demonstrated a significant association in the meta-analysis. The main limitations discussed in the studies were insufficient sample size, population heterogeneity, and the composition of control groups. Although some SNVs, particularly in IL10 and VDR, showed significant associations with PCM susceptibility in individual studies, the evidence remains limited. The meta-analyses included only two studies per SNV, resulting in low statistical power and exploratory pooled estimates, largely reflecting small sample sizes, lack of replication, and methodological heterogeneity across studies.

Background: Paracoccidioidomycosis (PCM) is a neglected systemic mycosis endemic to Latin America, where diagnosis is often delayed due to limited access to rapid, simple confirmatory testing tools in resource-limited settings. This gap creates a critical need for accessible detection methods of its causative agent, Paracoccidioides spp., that can be deployed in frontline healthcare facilities.

Methodology/principal findings: We developed a frugal Recombinase Polymerase Amplification (RPA) assay targeting a conserved region of the internal transcribed spacer (ITS) locus for genus-level detection of Paracoccidioides spp. Primer specificity was evaluated in silico and experimentally against phylogenetically related fungi and clinically relevant pathogens, with no cross-reactivity observed. The assay robustly amplified across multiple Paracoccidioides lineages, and all products were validated by Sanger sequencing. The analytical limit of detection (LoD) was 1 pg of genomic DNA per 8 µL reaction, demonstrated by UV-based SYBR Green I visualization, agarose gel electrophoresis, and Qubit fluorometric assessment. Key optimizations included reaction miniaturization from 50 µL to 8 µL and a simple freeze-boil lysis compatible with crude fungal biomass extracts, avoiding the need for commercial extraction kits, lengthy protocols and expensive equipment.

Conclusions/significance: This RPA assay offers a rapid, affordable, and operationally simple molecular tool specifically designed for the detection of Paracoccidioides DNA. Its ability to work with crude lysates and miniaturized reaction volumes supports its implementation in resource-limited endemic areas. Although clinical validation remains necessary, this assay constitutes a practical foundation for expanding molecular diagnostic capacity for PCM in underserved regions. This work demonstrates how frugal methodological strategies can support equitable access to molecular detection tools.

Background: Soil-transmitted helminthiasis (STH) and intestinal schistosomiasis are widespread and prevalent in tropical regions due to poor sanitation and limited healthcare access. Despite control efforts, localized epidemiological data remain essential for effective intervention. This study aimed to assess the prevalence of STH and associated factors among schoolchildren in Hawella Tulla sub-city, Hawassa City, Sidama National Regional State, Ethiopia.

Method: A school-based cross-sectional study involving 394 primary schoolchildren was conducted from June to December 2023. Data were collected using an interviewer-administered questionnaire. Infection with the parasite was diagnosed by Kato-Katz microscopy. Bivariate and multivariable logistic regression were used to identify factors associated with the STH infections.

Results: The combined prevalence of soil-transmitted helminths (STHs) and intestinal schistosomiasis was 42.6% (168/394; 95% CI: 37.8-47.6). STHs constituted the predominant infection, detected in 41.1% of children (162/394; 95% CI: 36.3-46.0), while intestinal schistosomiasis was found in 3.3% (13/394; 95% CI: 1.9-5.4). The most prevalent parasite was Ascaris lumbricoides (29.2%), followed by Trichuris trichiura (17.8%) and hookworms (5.1%). Schoolchildren who reported consuming unwashed fruits or vegetables (AOR: 2.89; 95% CI: 1.73-4.85), swimming or bathing in streams or lakes (AOR: 2.23; 95% CI: 1.31-3.79), and not receiving deworming treatment (AOR: 2.12; 95% CI: 1.26-3.56) were significantly more likely to be infected with soil-transmitted helminths (STHs).

Conclusion: Overall, soil-transmitted helminthiasis (STHs) and Schistosoma mansoni remain significant public health concerns in the study area, affecting more than one-third of schoolchildren. Infections were strongly associated with poor hygiene practices, inadequate deworming coverage, and exposure to contaminated water sources. This highlights the need for improved hygiene, health education, and deworming programs.

Background: Neglected tropical and vector-borne diseases, including dengue, chikungunya, lymphatic filariasis, and kala-azar, pose substantial public health burdens in India. Despite WHO recommendations for enhanced disease surveillance and targeted communication strategies, little is known about public perceptions and discussions of these diseases across digital platforms. Understanding these perceptions can guide evidence-based policy making and public health messaging.

Methods: We conducted an in silico analysis of publicly accessible social and news media data related to dengue, chikungunya, filariasis, and kala-azar in India from January 2019 to December 2023. YouTube comments and Google News headlines were systematically retrieved, pre-processed, and analysed through sentiment analysis (VADER lexicon) and Latent Dirichlet Allocation (LDA) topic modelling. Facebook and Twitter data were not included due to Application programming interface (API) restrictions and their current subscription-based models, limiting free access even for research purposes. We visualized disease-specific digital attention in comparison to epidemiological burden and created chord, Sankey, and network diagrams to elucidate thematic and sentiment-based interactions.

Results: Across keyword-matched items (n = 330), dengue accounted for 173 (~52%) and also had the highest mean annual reported burden (163,679 cases/year; 2019-2023). Lymphatic filariasis showed disproportionately high attention (106 items/mentions vs 3,060 reported cases/year), while kala-azar had minimal visibility (5 items; none on YouTube). Sentiment was overall neutral-to-positive, with Google News more neutral and YouTube more positive. Topics emphasized outbreak alerts, public-health campaigns, and prevention/treatment, with recurring vaccine/innovation themes.

Conclusions: Our study presents a novel approach combining digital surveillance, sentiment analysis, and topic modelling to provide insights into public perceptions of NTDs in India. The observed mismatch between epidemiological burden and online attention underscores the need for strategic public health messaging, aligning with WHO recommendations for community engagement and tailored disease-awareness campaigns. This research provides a valuable tool for policymakers to enhance the effectiveness of communication strategies and improve targeted intervention planning for neglected tropical diseases in India.