Biology subjects

Premawansa, G.

Publications and source records attributed to Premawansa, G..

7 recordsLinked to original sources

bioRxiv2025

In vitro effects of selected angiogenesis-promoting drugs on human Ea.hy926 endothelial cells treated with critical-stage dengue hemorrhagic fever serum

Endothelial dysfunction is the major pathophysiological effect in severe dengue infection. The effects of three angiogenesis-promoting drugs, Simvastatin, Phenytoin, and Ascorbic acid on endothelial dysfunction was assessed using the simulation model using Ea.hy.926 cells treating with severe dengue hemorrhagic fever serum. Sera of patients with dengue fever (DF, n=5), dengue hemorrhagic fever (DHF, n=5), and healthy controls (HC, n=5) were treated on Ea.hy926 endothelial cells and distances were measured after 3-hour incubation. DHF-treated cells showed a significant increase in average cell-cell distances compared to HC and DF, simulating endothelial destabilization caused during DHF condition (p<0.05). Significant reductions in cell-cell distances were observed in the cells treated with 0.01 {micro}M and 1 {micro}M Simvastatin along with DHF serum, compared to the cells treated only with DHF serum (p<0.05). Among these two conditions tested, 0.01 {micro}M Simvastatin showed a significant reduction in the cell-cell distances (p<0.05) and a significant increase in cell sizes (p<0.05) in the presence of DHF serum. Ascorbic acid (40 {micro}M, 80 {micro}M) showed no significant effect towards the endothelial monolayer destabilization in the presence of DHF serum. Both concentrations of phenytoin (10 {micro}M, 30 {micro}M) showed a significant increase in the average cell-cell distances compared to cells treated with DHF (p<0.05). This preliminary study suggests that low-dose Simvastatin promotes endothelial membrane formation in the presence of DHF serum and the reduction in cell-to-cell distances may not due to cell proliferation but could mainly be due to the increase in the average cell size, a known effect of Simvastatin.

immunology↗

bioRxiv2024

First report of pathogenic Leptospira in Sri Lankan bats: A potential reservoir risk

BackgroundLeptospirosis is a bacterial infection caused by spirochetes of the genus Leptospira. It affects both humans and animals, posing a significant public health threat worldwide. In Sri Lanka, leptospirosis causes annual outbreaks, particularly during the monsoon seasons. The disease is often difficult to diagnose and can have a high mortality rate. Bats are potential reservoirs for Leptospira in other countries. This study investigated the presence and diversity of Leptospira in bats inhabiting the Wavulgalge, a natural cave in Sri Lanka. Methodology/Principal FindingsUsing PCR and Sanger sequencing techniques, Leptospira borgpetersenii and Leptospira kirschneri were identified in Miniopterus fuliginosus and Rousettus leschenaultii bats. Out of 148 bat urine samples, 16 tested positive via RT-qPCR, with M. fuliginosus samples harboring L. borgpetersenii and one R. leschenaultii sample harboring L. kirschneri revealed by Sanger sequencing method. Conclusions/SignificanceThese findings enhance the understanding of the zoonotic role of Sri Lankan bats in Leptospira transmission. Author SummaryLeptospirosis is a bacterial disease that affects both humans and animals, particularly in tropical regions. It spreads through contact with water or soil contaminated by the urine of infected animals. In Sri Lanka, leptospirosis poses a significant public health challenge, with frequent outbreaks during the rainy season. However, while much research has focused on domestic animals as potential carriers, the role of bats in the transmission of this disease has not been fully explored. In this study, we investigated whether bats in Sri Lanka can act as carriers of Leptospira bacteria, which could contribute to the spread of leptospirosis to humans. We focused on a population of bats from the Wavulgalge cave and tested them for the presence of Leptospira using molecular methods. Our results provide the first evidence that Leptospira is present in Sri Lankan bats, highlighting their potential role as a reservoir for the bacteria. These findings are important because they suggest that bats, like rodents and livestock, could contribute to the spread of leptospirosis in Sri Lanka. Understanding which animals carry the bacteria helps inform public health strategies, allowing for more targeted surveillance and control measures. By including bats in these efforts, we can better prevent future outbreaks of leptospirosis and protect at-risk communities. This study also contributes to the broader understanding of how wildlife can influence human health, especially in tropical environments where human-animal interactions are common. Our work emphasizes the need for a One Health approach, which considers the connections between human, animal, and environmental health, to tackle neglected diseases like leptospirosis.

microbiology↗

bioRxiv2024

First Report of Nipah virus shed in urine by fruit bats (Pteropus medius), Sri Lanka

Nipah virus is an emerging pathogen with high public health relevance, causing outbreaks in South- and Southeast Asia with high case fatality rates. The natural reservoir host are fruit bats (Pteropus spp). In this study, we confirmed the presence of Nipah virus for the first time in Sri Lanka and are proving the genetic relatedness to Nipah virus strains from southern India, causing outbreaks in 2007, 2018, 2019 and 2023. It is noteworthy that the shedding of the Nipah Virus may have a temporal variation that correlates with the breeding season of Pteropus medius. Furthermore, preventive measures and possible mechanisms influencing viral shedding are discussed.

microbiology↗

bioRxiv2022

One Health Approach for the sampling of different bat species living in a sympatric colony

Bats are important contributors to the global ecosystems; at the same time, they are known to be a natural reservoir host for a number of human pathogenic viruses. These and many other unique features make them an interdisciplinary research object in the context of One Health, comprising zoology, ecology, virology, microbiology, molecular biology, immunology and public health issues. Performing field studies for bat research often aims to cover several of these topics and requires the combination of specific expertise in different fields. We carried out three individual field studies in Wavul Galge cave (Koslanda, Sri Lanka), where several bat species roost sympatrically. The main goals were to study the bat colony for ecological aspects and to sample bats for virological and molecular biological analyses. In the course of the field studies, we optimized the sampling procedure regarding safety aspects, a preferably low impact on the captured bats and an improved output of high-quality samples for further analysis. Different sampling methods and procedures were compared in order to establish a suitable strategy for frequent sampling and monitoring of these bats. In the present case study, we report on this process of optimizing our field work and provide suggestions for bat sampling methods that cause comparably less stress for the captured animals. We also report on constraints and obstacles encountered during the practical implementation and possible measures to overcome these. With these practical experiences, we hope to give support to other interdisciplinary research teams preparing for bat field work. Furthermore, we emphasize the need for the respectful treatment of the animals and minimized disturbance of their natural habitat when carrying out sustainable bat research.

zoology↗

bioRxiv2022

Comparative virome analysis of individual shedding routes of Miniopterus fuliginosus bats inhabiting the Wavul Galge Cave, Sri Lanka

Bats are described as the natural reservoir host for a wide range of viruses. Although an increasing number of bat-associated, potentially human pathogenic viruses were discovered in the past, the full picture of the bat viromes is not explored yet. In this study, the virome composition from Miniopterus fuliginosus bats inhabiting the Wavul Galge cave, Sri Lanka, was analyzed. To assess different possible shedding routes, oral swabs, feces and urine were collected and analyzed individually by using metagenomic NGS. The data obtained was further evaluated by using phylogenetic reconstructions. Two different alphacoronavirus strains were detected in feces and urine samples. Furthermore, a paramyxovirus was detected in urine samples. Sequences related to Picornaviridae, Iflaviridae, unclassified Riboviria and Astroviridae were identified in feces samples, and further sequences related to Astroviridae in urine samples. No further viruses were detected in oral swab samples. The comparative virome analysis in this study revealed a diversity in the virome composition between the collected sample types which also represent different potential shedding routes for the detected viruses. At the same time, several viruses were detected for the first time in bats in Sri Lanka. The detection of two different coronaviruses in the samples indicates the potential general persistence of this virus species in M. fuliginosus bats. Based on phylogenetics, the identified viruses are closer related to bat-associated viruses with comparably low human pathogenic potential. In further studies, the seasonal variation of the virome will be analyzed to identify possible shedding patterns for particular viruses.

molecular biology↗

bioRxiv2021

Molecular identification of bats from Wavulgalge cave, Wellawaya, Sri Lanka

This is the first report on the molecular identification and phylogeny of Rousettus leschenaultii, Rhinolophus rouxii, Hipposideros speoris, Hipposideros lankadiva, Miniopterus fuliginosus bat species in Sri Lanka, inferred from mitochondrially encoded cytochrome b gene sequences. Wellawaya Wavulgalge cave in Sri Lanka is one of the largest sympatric colonies found on the island, occupied by five species of bats. Recent research has indicated that bats show enormous cryptic genetic diversity. Moreover, even in the same species, acoustic properties of echolocation calls and morphological features such as fur colour could vary in different populations. Therefore, we have used molecular techniques for the accurate identification of five bat species recorded in one of the largest cave populations in Sri Lanka. Bats were caught using a hand net and saliva samples were collected non-invasively from each bat using a sterile oral swab. Nucleic acids were extracted from oral swab samples and mitochondrial DNA was amplified using primers targeting the mitochondrially encoded cytochrome b gene. This study identified the bat species recorded in the Wellawaya cave as Rousettus leschenaultii, Rhinolophus rouxii, Hipposideros speoris, Hipposideros lankadiva and Miniopterus fuliginosus. Our findings will contribute to future conservation and systematic studies of bats in Sri Lanka. This study will also provide the basis for a genetic database of Sri Lankan bats.

zoology↗

bioRxiv2018

No cell is an island: circulating T cell:monocyte complexes are markers of immune perturbations

Our results highlight for the first time that a significant proportion of cell doublets in flow cytometry, previously believed to be the result of technical artefacts and thus ignored in data acquisition and analysis, are the result of true biological interaction between immune cells. In particular, we show that cell:cell doublets pairing a T cell and a monocyte can be directly isolated from human blood, and high resolution microscopy shows polarized distribution of LFA1/ICAM1 in many doublets, suggesting in vivo formation. Intriguingly, T cell:monocyte complex frequency and phenotype fluctuate with the onset of immune perturbations such as infection or immunization, reflecting expected polarization of immune responses. Overall these data suggest that cell doublets reflecting T cell-monocyte in vivo immune interactions can be detected in human blood and that the common approach in flow cytometry to avoid studying cell:cell complexes should be revisited.

immunology↗