PLoS Neglected Tropical Diseases

Journal: PLoS Neglected Tropical Diseases

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PLOS

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1935-2727
1935-2735

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Publications 1 - 10 of 16

Performance evaluation of the diaxxoPCR system for rapid and user-friendly stool-based diagnosis of trichuriasis, ascariasis and strongyloidiasis in Mozambique
Messa, Augusto; Bengtson, Michel; Fleitas, Pedro; et al. (2025)
PLoS Neglected Tropical Diseases
Background: Nucleic acid amplification tests have shown promising results for the diagnosis of soil-transmitted helminths (STH). The implementation of real-time PCR (qPCR) in low-resource settings is, however, still hampered by multiple logistical challenges. In this study, we assessed the diagnostic performance of a cartridge-based real-time PCR system (diaxxoPCR) for the detection of DNA of Trichuris trichiura, Ascaris lumbricoides, and Strongyloides stercoralis in clinical samples, using qPCR as the reference test. Methodology: Initially, a technical validation of the diaxxoPCR system in a singleplex pod (cartridge) design was performed using 37 predefined DNA samples (Study A), followed by a diagnostic comparison between the diaxxoPCR system (singleplex) and qPCR on DNA samples extracted from 325 stools collected in a clinical trial in a rural area of Mozambique (Study B). Finally, one negative and one positive DNA sample were used to demonstrate the technical performance of a multiplex pod design as a potential use-case for the diaxxoPCR system (Study C). Principal Findings: Study A demonstrated that the diaxxoPCR system performed reliably for each of the three STH targets, with minimal intra- and inter-assay variation and sufficient output reproducibility. Study B, performed in Mozambique, showed a positive qPCR result in 57.5% (187), 15.4% (50), and 0.3% (1) of the 325 DNA trial samples for T. trichiura, A. lumbricoides, and S. stercoralis, respectively. The diaxxoPCR system demonstrated sensitivities and specificities above 97% and 94% for each target, resulting in nearly perfect to perfect qualitative agreements with the reference test. Quantitatively, significant and positive associations were seen between the Ct-values (qPCR) and Cq-values (diaxxoPCR). In Study C, the diaxxoPCR system correctly detected all 3 targets in the multiplex pod design. Conclusion: With refinements regarding faecal DNA extraction procedures, the diaxxoPCR system has potential to provide accurate and easy-to-use real-time molecular diagnostics of STH in low resource laboratories.
Serodiagnosis of Echinococcus spp. Infection: Explorative Selection of Diagnostic Antigens by Peptide Microarray
List, Claudia; Qi, Weihong; Maag, Eva; et al. (2010)
PLoS Neglected Tropical Diseases
Background Production of native antigens for serodiagnosis of helminthic infections is laborious and hampered by batch-to-batch variation. For serodiagnosis of echinococcosis, especially cystic disease, most screening tests rely on crude or purified Echinococcus granulosus hydatid cyst fluid. To resolve limitations associated with native antigens in serological tests, the use of standardized and highly pure antigens produced by chemical synthesis offers considerable advantages, provided appropriate diagnostic sensitivity and specificity is achieved. Methodology/Principal Findings Making use of the growing collection of genomic and proteomic data, we applied a set of bioinformatic selection criteria to a collection of protein sequences including conceptually translated nucleotide sequence data of two related tapeworms, Echinococcus multilocularis and Echinococcus granulosus. Our approach targeted alpha-helical coiled-coils and intrinsically unstructured regions of parasite proteins potentially exposed to the host immune system. From 6 proteins of E. multilocularis and 5 proteins of E. granulosus, 45 peptides between 24 and 30 amino acids in length were designed. These peptides were chemically synthesized, spotted on microarrays and screened for reactivity with sera from infected humans. Peptides reacting above the cut-off were validated in enzyme-linked immunosorbent assays (ELISA). Peptides identified failed to differentiate between E. multilocularis and E. granulosus infection. The peptide performing best reached 57% sensitivity and 94% specificity. This candidate derived from Echinococcus multilocularis antigen B8/1 and showed strong reactivity to sera from patients infected either with E. multilocularis or E. granulosus. Conclusions/Significance This study provides proof of principle for the discovery of diagnostically relevant peptides by bioinformatic selection complemented with screening on a high-throughput microarray platform. Our data showed that a single peptide cannot provide sufficient diagnostic sensitivity whereas pooling several peptide antigens improved sensitivity; thus combinations of several peptides may lead the way to new diagnostic tests that replace, or at least complement conventional immunodiagnosis of echinococcosis. Our strategy could prove useful for diagnostic developments in other pathogens.
Interactions and Potential Implications of Plasmodium falciparum-Hookworm Coinfection in Different Age Groups in South-Central Cote d'Ivoire
Righetti, Aurélie A.; Glinz, Dominik; Adiossan, Lukas G.; et al. (2012)
PLoS Neglected Tropical Diseases
Background: Given the widespread distribution of Plasmodium and helminth infections, and similarities of ecological requirements for disease transmission, coinfection is a common phenomenon in sub-Saharan Africa and elsewhere in the tropics. Interactions of Plasmodium falciparum and soil-transmitted helminths, including immunological responses and clinical outcomes of the host, need further scientific inquiry. Understanding the complex interactions between these parasitic infections is of public health relevance considering that control measures targeting malaria and helminthiases are going to scale. Methodology: A cross-sectional survey was carried out in April 2010 in infants, young school-aged children, and young non-pregnant women in south-central Côte d’Ivoire. Stool, urine, and blood samples were collected and subjected to standardized, quality-controlled methods. Soil-transmitted helminth infections were identified and quantified in stool.Finger-prick blood samples were used to determine Plasmodium spp. infection, parasitemia, and hemoglobin concentrations. Iron, vitamin A, riboflavin, and inflammation status were measured in venous blood samples. Principal Findings: Multivariate regression analysis revealed specific association between infection and demographic,socioeconomic, host inflammatory and nutritional factors. Non-pregnant women infected with P. falciparum had significantly lower odds of hookworm infection, whilst a significant positive association was found between both parasitic infections in 6- to 8-year-old children. Coinfected children had lower odds of anemia and iron deficiency than their counterparts infected with P. falciparum alone. Conclusions/Significance:Our findings suggest that interaction between P. falciparum and light-intensity hookworm infections vary with age and, in school-aged children, may benefit the host through preventing iron deficiency anemia. This observation warrants additional investigation to elucidate the mechanisms and consequences of coinfections, as this information could have important implications when implementing integrated control measures against malaria and helminthiases.
Structure-Activity Relationship Studies on the Macrolide Exotoxin Mycolactone of Mycobacterium ulcerans
Scherr, Nicole; Gersbach, Philipp; Dangy, Jean-Pierre; et al. (2013)
PLoS Neglected Tropical Diseases
Background Mycolactones are a family of polyketide-derived macrolide exotoxins produced by Mycobacterium ulcerans, the causative agent of the chronic necrotizing skin disease Buruli ulcer. The toxin is synthesized by polyketide synthases encoded by the virulence plasmid pMUM. The apoptotic, necrotic and immunosuppressive properties of mycolactones play a central role in the pathogenesis of M. ulcerans. Methodology/Principal Findings We have synthesized and tested a series of mycolactone derivatives to conduct structure-activity relationship studies. Flow cytometry, fluorescence microscopy and Alamar Blue-based metabolic assays were used to assess activities of mycolactones on the murine L929 fibroblast cell line. Modifications of the C-linked upper side chain (comprising C12–C20) caused less pronounced changes in cytotoxicity than modifications in the lower C5-O-linked polyunsaturated acyl side chain. A derivative with a truncated lower side chain was unique in having strong inhibitory effects on fibroblast metabolism and cell proliferation at non-cytotoxic concentrations. We also tested whether mycolactones have antimicrobial activity and found no activity against representatives of Gram-positive (Streptococcus pneumoniae) or Gram-negative bacteria (Neisseria meningitis and Escherichia coli), the fungus Saccharomyces cerevisae or the amoeba Dictyostelium discoideum. Conclusion Highly defined synthetic compounds allowed to unambiguously compare biological activities of mycolactones expressed by different M. ulcerans lineages and may help identifying target structures and triggering pathways.
Investigation of pyrimidine nucleoside analogues as chemical probes to assess compound effects on the proliferation of Trypanosoma cruzi intracellular parasites
Sykes, Melissa L.; Hilko, David H.; Kung, Livia I.; et al. (2020)
PLoS Neglected Tropical Diseases
Trypanosoma cruzi parasites utilise de novo pyrimidine biosynthesis to produce DNA and survive within mammalian host cells. This pathway can be hijacked to assess the replication of intracellular parasites with the exogenous addition of a DNA specific probe. To identify suitable probe compounds for this application, a collection of pyrimidine nucleoside analogues was assessed for incorporation into T. cruzi intracellular amastigote DNA using image-based technology and script-based analysis. Associated mammalian cell toxicity of these compounds was also determined against both the parasite host cells (3T3 cells) and HEK293 cells. Incorporation of 5-ethynyl-2′-deoxyuridine (EdU) into parasite DNA was the most effective of the probes tested, with minimal growth inhibition observed following either two or four hours EdU exposure. EdU was subsequently utilised as a DNA probe, followed by visualisation with click chemistry to a fluorescent azide, to assess the impact of drugs and compounds with previously demonstrated activity against T. cruzi parasites, on parasite replication. The inhibitory profiles of these molecules highlight the benefit of this approach for identifying surviving parasites post-treatment in vitro and classifying compounds as either fast or slow-acting. F-ara-EdU resulted in <50% activity observed against T. cruzi amastigotes following 48 hours incubation, at 73 μM. Collectively, this supports the further development of pyrimidine nucleosides as chemical probes to investigate replication of the parasite T. cruzi.
DNA plasmid coding for Phlebotomus sergenti salivary protein PsSP9, a member of the SP15 family of proteins, protects against Leishmania tropica
Gholami, Elham; Oliveira, Fabiano; Taheri, Tahereh; et al. (2019)
PLoS Neglected Tropical Diseases
Single nucleotide polymorphism typing of Mycobacterium ulcerans reveals focal transmission of buruli ulcer in a highly endemic region of Ghana
Röltgen, Katharina; Qi, Weihong; Ruf, Marie-Thérèse; et al. (2010)
PLoS Neglected Tropical Diseases
Buruli ulcer (BU) is an emerging necrotizing disease of the skin and subcutaneous tissue caused by Mycobacterium ulcerans. While proximity to stagnant or slow flowing water bodies is a risk factor for acquiring BU, the epidemiology and mode of M. ulcerans transmission is poorly understood. Here we have used high-throughput DNA sequencing and comparisons of the genomes of seven M. ulcerans isolates that appeared monomorphic by existing typing methods. We identified a limited number of single nucleotide polymorphisms (SNPs) and developed a real-time PCR SNP typing method based on these differences. We then investigated clinical isolates of M. ulcerans on which we had detailed information concerning patient location and time of diagnosis. Within the Densu river basin of Ghana we observed dominance of one clonal complex and local clustering of some of the variants belonging to this complex. These results reveal focal transmission and demonstrate, that micro-epidemiological analyses by SNP typing has great potential to help us understand how M. ulcerans is transmitted.
Sensitivity and Specificity of a Urine Circulating Anodic Antigen Test for the Diagnosis of Schistosoma haematobium in Low Endemic Settings
Knopp, Stefanie; Corstjens, Paul L.A.M.; Koukounari, Artemis; et al. (2015)
PLoS Neglected Tropical Diseases
Background Elimination of schistosomiasis as a public health problem and interruption of transmission in selected areas are key goals of the World Health Organization for 2025. Conventional parasitological methods are insensitive for the detection of light-intensity infections. Techniques with high sensitivity and specificity are required for an accurate diagnosis in low-transmission settings and verification of elimination. We determined the accuracy of a urine-based up-converting phosphor-lateral flow circulating anodic antigen (UCP-LF CAA) assay for Schistosoma haematobium diagnosis in low-prevalence settings in Zanzibar, Tanzania. Methodology A total of 1,740 urine samples were collected in 2013 from children on Pemba Island, from schools where the S. haematobium prevalence was <2%, 2–5%, and 5–10%, based on a single urine filtration. On the day of collection, all samples were tested for microhematuria with reagent strips and for the presence of S. haematobium eggs with microscopy. Eight months later, 1.5 ml of urine from each of 1,200 samples stored at -20°C were analyzed by UCP-LF CAA assay, while urine filtration slides were subjected to quality control (QCUF). In the absence of a true ‘gold’ standard, the diagnostic performance was calculated using latent class analyses (LCA). Principal Findings The ‘empirical’ S. haematobium prevalence revealed by UCP-LF CAA, QCUF, and reagent strips was 14%, 5%, and 4%, respectively. LCA revealed a sensitivity of the UCP-LF CAA, QCUF, and reagent strips of 97% (95% confidence interval (CI): 91–100%), 86% (95% CI: 72–99%), and 67% (95% CI: 52–81%), respectively. Test specificities were consistently above 90%. Conclusions/Significance The UCP-LF CAA assay shows high sensitivity for the diagnosis of S. haematobium in low-endemicity settings. Empirically, it detects a considerably higher number of infections than microscopy. Hence, the UCP-LF CAA employed in combination with QCUF, is a promising tool for monitoring and surveillance of urogenital schistosomiasis in low-transmission settings targeted for elimination.
Crystal Structures of T. b. rhodesiense Adenosine Kinase Complexed with Inhibitor and Activator: Implications for Catalysis and Hyperactivation
Kuettel, Sabine; Greenwald, Jason; Kostrewa, Dirk; et al. (2011)
PLoS Neglected Tropical Diseases
Background The essential purine salvage pathway of Trypanosoma brucei bears interesting catalytic enzymes for chemotherapeutic intervention of Human African Trypanosomiasis. Unlike mammalian cells, trypanosomes lack de novo purine synthesis and completely rely on salvage from their hosts. One of the key enzymes is adenosine kinase which catalyzes the phosphorylation of ingested adenosine to form adenosine monophosphate (AMP) utilizing adenosine triphosphate (ATP) as the preferred phosphoryl donor. Methods and Findings Here, we present the first structures of Trypanosoma brucei rhodesiense adenosine kinase (TbrAK): the structure of TbrAK in complex with the bisubstrate inhibitor P1,P5-di(adenosine-5′)-pentaphosphate (AP5A) at 1.55 Å, and TbrAK complexed with the recently discovered activator 4-[5-(4-phenoxyphenyl)-2H-pyrazol-3-yl]morpholine (compound 1) at 2.8 Å resolution. Conclusions The structural details and their comparison give new insights into substrate and activator binding to TbrAK at the molecular level. Further structure-activity relationship analyses of a series of derivatives of compound 1 support the observed binding mode of the activator and provide a possible mechanism of action with respect to their activating effect towards TbrAK.
Markov Model Predicts Changes in STH Prevalence during Control Activities Even with a Reduced Amount of Baseline Information
Montresor, Antonio; Deol, Arminder; Porta, Natacha à; et al. (2016)
PLoS Neglected Tropical Diseases
Background Estimating the reduction in levels of infection during implementation of soil-transmitted helminth (STH) control programmes is important to measure their performance and to plan interventions. Markov modelling techniques have been used with some success to predict changes in STH prevalence following treatment in Viet Nam. The model is stationary and to date, the prediction has been obtained by calculating the transition probabilities between the different classes of intensity following the first year of drug distribution and assuming that these remain constant in subsequent years. However, to run this model longitudinal parasitological data (including intensity of infection) are required for two consecutive years from at least 200 individuals. Since this amount of data is not often available from STH control programmes, the possible application of the model in control programme is limited. The present study aimed to address this issue by adapting the existing Markov model to allow its application when a more limited amount of data is available and to test the predictive capacities of these simplified models. Method We analysed data from field studies conducted with different combination of three parameters: (i) the frequency of drug administration; (ii) the drug distributed; and (iii) the target treatment population (entire population or school-aged children only). This analysis allowed us to define 10 sets of standard transition probabilities to be used to predict prevalence changes when only baseline data are available (simplified model 1). We also formulated three equations (one for each STH parasite) to calculate the predicted prevalence of the different classes of intensity from the total prevalence. These equations allowed us to design a simplified model (SM2) to obtain predictions when the classes of intensity at baseline were not known. To evaluate the performance of the simplified models, we collected data from the scientific literature on changes in STH prevalence during the implementation of 26 control programmes in 16 countries. Using the baseline data observed, we applied the simplified models and predicted the onward prevalence of STH infection at each time-point for which programme data were available. We then compared the output from the model with the observed data from the programme. Results The comparison between the model-predicted prevalence and the observed values demonstrated a good accuracy of the predictions. In 77% of cases the original model predicted a prevalence within five absolute percentage points from the observed figure, for the simplified model one in 69% of cases and for the simplified model two in 60% of cases. We consider that the STH Markov model described here could be an important tool for programme managers to monitor the progress of their control programmes and to select the appropriate intervention. We also developed, and made freely available online, a software tool to enable the use of the STH Markov model by personnel with limited knowledge of mathematical models.

Publications 1 - 10 of 16

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