Evaluation of envelope domain III-based single chimeric tetravalent antigen and monovalent antigen mixtures for the detection of anti-dengue antibodies in human sera

<p>Abstract</p> <p>Background</p> <p>Flavivirus cross-reactive antibodies in human sera interfere with the definitive identification of dengue virus (DENV) infections especially in areas with multiple co-circulating flaviviruses. Use of DENV envelope domain-III (EDIII) can partially resolve the problem. This study has examined the effect of (i) incorporating the EDIIIs of four DENV serotypes into a single chimeric antigen, and (ii) immobilizing the antigen through specific interaction on the sensitivity and specificity of anti-DENV antibody detection.</p> <p>Methods</p> <p>A sera panel (n = 164) was assembled and characterized using commercial kits for infection by DENV and a host of other pathogens. Anti-DENV antibodies of both IgM and IgG classes in this panel were detected in indirect ELISAs using a mixture of monovalent EDIIIs, a chimeric EDIII-based tetravalent antigen, EDIII-T, and a biotinylated version of the latter as coating antigens. The sensitivity and specificity of these assays were compared to those obtained using the PanBio Dengue IgG/IgM ELISAs.</p> <p>Results</p> <p>The performance of dengue IgG and IgM indirect ELISAs, using either a physical mixture of four EDIIIs or the single chimeric EDIII-T antigen, were comparable. Coating of a biotinylated version of the tetravalent antigen on streptavidin plates enhanced sensitivity without compromising specificity.</p> <p>Conclusions</p> <p>The incorporation of the EDIIIs of the four DENV serotypes into a single chimeric antigen did not adversely affect assay outcome in indirect ELISAs. Oriented, rather than random, immobilization of the tetravalent antigen enhanced sensitivity of detection of anti-DENV antibodies with retention of 100% specificity.</p

Estimating the fusible content of individual coal grains and its application in coke making

Quantification of the amount of inertinite that is fusible during coke making has long been a goal for many researchers and coke makers alike. This study has used matched halves of coal and coke to first determine the fusibility cut-off, and has then used CSIRO's CGA optical imaging system to obtain quantitative compositional information on individual coal particles at the size they are used for coke making. The reflectance cut-off between fusible and infusible inertinite was determined by cutting coal lumps in half and coking one half. Comparison of matched structures in images of the coal and coke lumps allowed the fusible/infusible reflectance cut-off for inertinite to be determined for each of the coals. This study found that rather than there being a single reflectance cut off point between fusible and infusible inertinite for each coal there is a consistent difference (range) between the end of the vitrinite reflectance distribution and the fusible/infusible inertinite reflectance boundary for each individual particle within a coal. This reflectance range was then used to estimate the amount of fusible and infusible inertinite in individual particles of coal which had been crushed for use as coke oven feed for six Australian coking coals (consisting of matched pairs of coals of similar ranks from different Australian coal measures). Also determined was size detail for the individual inertinite structures within each particle and the amount of infusible inertinite structures greater than 1.5 mm in length. The CGA results obtained suggest that two of the coals (from the Rangal Coal Measures) contained a greater proportion of large infusible inerts than did the coals of comparable rank from other Australian measures. If this is proven, the information may assist coal producers to develop specific milling strategies for these coals

Predatory efficacy of five locally available copepods on Aedes larvae under laboratory settings: An approach towards bio-control of dengue in Sri Lanka.

Many countries are in search of more effective and sustainable methods for controlling dengue vectors, due to undeniable inefficiencies in chemical and mechanical vector control methods. Bio-control of vectors by copepods is an ideal method of using interactions in the natural ecosystem for vector management, with minimum consequences on the environment. Current study determined the predatory efficacy of five locally abundant copepod species on, Aedes larvae under laboratory conditions. Copepods were collected from the pre-identified locations within the districts of Gampaha and Kandy, and identified morphologically. Individual species of copepods were maintained as separate colonies with Paramecium culture and wheat grain as supplementary food. Five adult copepods of each species was introduced into separate containers with 200 larvae (1st instar) of Aedes aegypti. Number of larvae survived in containers were enumerated at 3 hour intervals within a duration of 24 hours. Each experiment was repeated five times. The same procedure was followed for Ae. albopictus. Significance in the variations among predation rates was evaluated with General Linear Modelling (GLM) followed by Tukey's pair-wise comparison in SPSS (version 23). Significant variations in predation rates of studied copepod species were reported (p<0.05), whereby M. leuckarti indicated the highest followed by M. scrassus, while C. languides indicated the lowest predatory efficacy. The effect of different Aedes larval species on the predation rates of copepods remained significant (p<0.05), even though the effect on predatory efficiency was not significant. Based on the findings, both M. leuckarti and M. scrassus, with the highest predatory efficiencies, could be recommended as potential candidates for biological controlling of Aedes vectors in Sri Lanka

Spatial and seasonal analysis of human leptospirosis in the District of Gampaha, Sri Lanka

Leptospirosis is a zoonostic infectious disease, caused by a pathogenic species of the Genus Leptospira. In recent years, a markedly increased number of leptospirosis cases have been reported in the District of Gampaha, in the Western Province of Sri Lanka. Typically, the risk of the disease in the district is seasonal with a small spike occurs in March to May and a large spike occurs during October to December. Objectives of this study were to analyze spatial and seasonal patterns of human leptospirosis and to predict the leptospirosis epidemic trend in the District of Gampaha, Sri Lanka. All Divisional Secretariats (DS) of the district of Gampaha were selected for the study. Epidemiological data were obtained from the Regional Epidemiological Unit, Gampaha. The leptospirosis cases were georeferenced according to DS in where these cases were reported. The cumulative incidence and the fatality were calculated for each DS. Of the georeferenced data, highest mean (±S.E.) of number of leptospirosis cases (72.60 ±15.54) were observed from DS of Mirigama. The highest mean cumulative incidence (4.97±1.10) and case fatality rate (3.88±2.42) were observed from DS of Divulapitiya and Katana respectively. According to past 10 years data on leptospirosis, highest mean numbers of leptospirosis cases were reported in March (51.00±12.99) and November (56.80±8.27). A predictive model for clinically confirmed human leptospirosis was designed for the district by using TSA package of the statistical software R. This study provides an evidence base for reducing disease burden by improving the understanding of the dynamic patterns of the disease in the District of Gampaha, Sri Lanka.</p

Potential of Extra Income Generation for the Rural Sector by Medicinal Plant Cultivation

Sri Lanka is very rich in plant diversity ensuring the supply for resources for local folk remedies and ayurvedic treatments. Among those plants, some bear volatile oils in the leaves with the ability to repel mosquitoes. However, most such plants were underexploited and underutilised. Hence, this study aimed to compile information on plant species which are commonly found in homegardens in Kurunegala district of Sri Lanka and to find strategies to help rural economic development. For this purpose, indigenous knowledge was gathered through interviewing 50 traditional ayurvedic practitioners and 30 subject experts. This survey revealed the availability of 127 volatile oil-bearing plant species with mosquito repellent properties. Those plants were cross-referenced with the IUCN conservation status to eliminate the ones in the high risk categories. Finally, 29 plant species(Ocimum tenuiflorum Sub-type Rama, O. gratissimum, Hyptis suaveolens, Atalantia ceylanica, Citrus aurantifolia, Cinnamomum verum, Cymbopogon citratus, O. tenuiflorum Sub-type Krishna, Plectranthus barbatus, P. zatarhendi, Acronychia pedunculata, Ageratum conyzoides, Acorus calamus, Citrus madurensis, Eryngium foetidum, Citrus sinensis, Citrus reticulata, Aegle marmelos, Anisomeles indica, Vitex negundo, Tithonia diversifolia, Croton laccifer L., Toddalia asiatica, Piper betle, Clausena indica, Ruta chalepensis, Limonia acidissima, Michelia champaca and Evolvulus alsinoides) were identified out of 123, by following a weighted ranking system based on the priority given by both ayurvedic practitioners and subject experts. Identification of the availability and willingness to supply of those top ranked plant species was tested via a structured questionnaire survey conducted for 80 participants in four villages (Hulugalla, Randenigama, Porawewa and Papolegama) in two agro-ecological regions (IL1 and IL3) of Kurunegala district. Selected 20 households from each village had the land extent equal or greater than 1 acre (0.4 ha). According to the results, Citrus aurantifolia, Citrus sinensis, Citrus reticulata, Aegle marmelos and Ocimum tenuiflorum Sub-type Rama were the top 5 ranked plant species that were commonly available. Further, this study demonstrated that on an average a family could earn between Rs. 500.00 and Rs. 3,000.00 by selling 1 kg of air-dried leaves. Thus, encouragement of medicinal plant cultivation in rural areas will help to generate financial returns and to conserve these plants in the wild.Keywords: Mosquito repellence, Volatile oils, Medicinal plants, Rural economy, Indigenous knowledg

A simplified non radioactive DNA probe technique for the field detection of sibling species A of the Anopheles culicifacies (Diptera: Culicidae) complex

Three cloned highly repetitive DNA sequences Rp36, Rp217 and Rp234 isolated from An.culicifacies Giles, sensu lato were developed as non radioactive DNA probes by using a biotinylatedlabeling and colorimetric detection system. These non radioactive DNA probes distinguish siblingspecies A from species B and C of the An. culicifacies complex in a dot blot hybridization assayusing single mosquito DNA extracts diluted 50 fold. The biotinylated Rp217 probe was furtherassayed in a more simple procedure which involves the hybridization of blots prepared fromsquashed mosquito heads. This technique avoids the separate extraction of mosquito DNA andfacilitates a number of samples to be processed rapidly while also allowing several field analyses tobe carried out on one mosquito specimen.Key words : Anopheles culicifacies, non radioactive DNA probe

A simplified non radioactive DNA probe technique for the field detection of sibling species A of the Anopheles culicifacies (Diptera: Culicidae) complex

Three cloned highly repetitive DNA sequences Rp36, Rp217 and Rp234 isolated from An.culicifacies Giles, sensu lato were developed as non radioactive DNA probes by using a biotinylatedlabeling and colorimetric detection system. These non radioactive DNA probes distinguish siblingspecies A from species B and C of the An. culicifacies complex in a dot blot hybridization assayusing single mosquito DNA extracts diluted 50 fold. The biotinylated Rp217 probe was furtherassayed in a more simple procedure which involves the hybridization of blots prepared fromsquashed mosquito heads. This technique avoids the separate extraction of mosquito DNA andfacilitates a number of samples to be processed rapidly while also allowing several field analyses tobe carried out on one mosquito specimen.Key words : Anopheles culicifacies, non radioactive DNA probe