Publications by authors named "Y I Nilmini Silva Gunawardene"

19 Publications

Voltage-Gated Sodium Channel () Mutation-Based Pyrethroid Resistance in Populations of Three Endemic Dengue Risk Areas of Sri Lanka.

Biomed Res Int 2021 22;2021:8874092. Epub 2021 May 22.

Molecular Medicine Unit, Faculty of Medicine, University of Kelaniya, Sri Lanka.

Background: Pyrethroid insecticides are widely used in many countries for chemical-based control of . Regardless of their efficacy, the constant use of insecticides has induced insecticide resistance mechanisms, such as knockdown resistance () in mosquitoes. Sri Lankan Vector Controlling Entities (VCE) have been using a variety of pyrethroid insecticides as the primary approach for dengue control. However, development of any resistance among the mosquitoes has been limitedly studied in the country. Therefore, the current study was conducted to evaluate the prevalence of F1534C, V1016G, and S989P mutations among mosquito populations in three dengue endemic high-risk regions of Sri Lanka. . Immature (both pupae and larvae) stages of mosquitoes were collected from Colombo, Gampaha, and Kandy districts of Sri Lanka from February 2018 to December 2019. Polymerase Chain Reaction- (PCR-) based assay for molecular genotyping of mutations was performed to identify the prevalence of mutations in collected populations, separately. The frequencies of the resistant and susceptible kdr alleles were determined by using the Hardy-Weinberg equilibrium.

Results: The populations from Colombo, Gampaha, and Kandy districts showed 46%, 42%, and 22% of F1534C mutation allele frequencies, along with 15%, 12%, and 6% of V1016G mutation allele frequencies, respectively. The mutation allele frequencies of S989 in Colombo, Gampaha, and Kandy districts were 9.5%, 8.5%, and 4.5%, respectively. The wild-type (PP) genotype remained predominant within all the three districts, whereas the homogenous (QQ) mutation genotype occurred only in minority. The abundance of Q allele frequency in mosquitoes was relatively higher for all the three mutations in Colombo.

Conclusions: The findings clearly indicate that long-term insecticide applications and multiple use of pyrethroids have led to the acquisition of mutations, leading to the development of insecticide resistance among local populations, especially in the Colombo and Gampaha districts. Therefore, evaluation of the prevalence levels of these mutations highlights the necessity for shifting towards novel vector control strategies.
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http://dx.doi.org/10.1155/2021/8874092DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8166465PMC
May 2021

Assessment of Developmental and Reproductive Fitness of Dengue-Resistant Transgenic and Improvement of Fitness Using Antibiotics.

Biomed Res Int 2021 2;2021:6649038. Epub 2021 Mar 2.

Department of Chemistry, Faculty of Science, University of Colombo, Colombo, Sri Lanka.

Background: Genetic modification offers opportunities to introduce artificially created molecular defence mechanisms to vector mosquitoes to counter diseases causing pathogens such as the dengue virus, malaria parasite, and Zika virus. RNA interference is such a molecular defence mechanism that could be used for this purpose to block the transmission of pathogens among human and animal populations. In our previous study, we engineered a dengue-resistant transgenic using RNAi to turn off the expression of dengue virus serotype genomes to reduce virus transmission, requiring assessment of the fitness of this mosquito with respect to its wild counterpart in the laboratory and semifield conditions.

Method: Developmental and reproductive fitness parameters of TM and WM have assessed under the Arthropod Containment Level 2 conditions, and the antibiotic treatment assays were conducted using co-trimoxazole, amoxicillin, and doxycycline to assess the developmental and reproductive fitness parameters.

Results: A significant reduction of developmental and reproductive fitness parameters was observed in transgenic mosquito compared to wild mosquitoes. However, it was seen in laboratory-scale studies that the fitness of this mosquito has improved significantly in the presence of antibiotics such as co-trimoxazole, amoxicillin, and doxycycline in their feed.

Conclusion: Our data indicate that the transgenic mosquito produced had a reduction of the fitness parameters and it may lead to a subsequent reduction of transgenic vector density over the generations in field applications. However, antibiotics of co-trimoxazole, amoxicillin, and doxycycline have shown the improvement of fitness parameters indicating the usefulness in field release of transgenic mosquitoes.
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http://dx.doi.org/10.1155/2021/6649038DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7946483PMC
May 2021

RNAi-mediated silencing of ARV1 in Setaria digitata impairs in-vitro microfilariae release, embryogenesis and adult parasite viability.

Vet Parasitol 2020 Aug 31;284:109189. Epub 2020 Jul 31.

Department of Chemistry, Faculty of Science, University of Colombo, PO 1490, Kumaratunga Munidasa Mawatha, Colombo, 00300, Sri Lanka. Electronic address:

Setaria digitata is a nematode that resides in the peritoneal cavity of ruminants causing cerebrospinal nematodiasis disease affecting livestock and inflicting significant economic forfeitures in Asia. Further, this nematode can infect humans, causing abscesses, allergic reactions, enlarged lymph nodes, eye lesions and inflammation of the lungs. The 'ARE2 required for viability1' (ARV1) encodes for putative lipid transporter localized in the endoplasmic reticulum (ER) and Golgi complex membrane in humans and yeast. In the present study, the functional role of S. digitata ARV1 (SD-ARV1) was investigated using RNA interference (RNAi) reverse genetic tool. The targeted silencing SD-ARV1 transcripts by siRNA mediated RNAi resulted in a dramatic reduction of SD-ARV1 gene and protein expressions in S. digitata, which in turn modulated the parasitic motility, its production of eggs and microfilaria viability. Further, the same silencing caused severe phenotypic deformities such as distortion of eggs and embryonic development arrest in the intrauterine stages of adult female S. digitata. These results suggest that SD-ARV1 plays a pivotal role in worm embryogenesis, adult parasite motility and microfilariae viability. Finally, the ubiquitous presence of ARV1 in human filarial nematodes, its crucial functional roles in nematode biology and its remarkable diversity in primary protein structure compared to homologues in their hosts warrants further investigations to ascertain its candidacy in anthelmintic drug development.
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http://dx.doi.org/10.1016/j.vetpar.2020.109189DOI Listing
August 2020

Use of Novaluron-Based Autocidal Gravid Ovitraps to Control Dengue Vector Mosquitoes in the District of Gampaha, Sri Lanka.

Biomed Res Int 2020 29;2020:9567019. Epub 2020 Feb 29.

Molecular Medicine Unit, Faculty of Medicine, University of Kelaniya, Ragama, Sri Lanka.

Dengue is the most important mosquito-borne viral infection in Sri Lanka causing an enormous social and economic burden in the country. In the absence of therapeutic drugs and the developed vaccines are under investigation, vector control is the best strategy to reduce the disease transmission. Therefore, the development of novel tools to control dengue vector mosquitoes has become the need of the hour. Novaluron is a recently developed Insect Growth Regulator (IGR) which inhibits chitin synthesis in immature stages of insects. The aim of the study was to identify the efficacy of a simple and cost-effective Autocidal Gravid Ovitrap (AGO) developed using Novaluron to control dengue outbreaks in the District of Gampaha, Sri Lanka. Laboratory and semifield experiments were performed to identify the activity range, optimum field dosage, and residual effects of Novaluron following the World Health Organization guidelines, and field experiments were performed in the Ragama Medical Officer of Health (MOH) area. Two study areas 800 m apart were selected and assigned as treated and control areas randomly. In each study area, 30 households were selected randomly. Each household was given two ovitraps, one placed indoors and the other placed outdoors. Mortality and survival counts were recorded separately for one-year time period and data were analyzed using a two-way repeated measures analysis of variance model. During the laboratory experiments, the adult emerging inhibition was 100% in all tested concentrations. The optimum field dosage was 2 ppm and the residual effect was 28 days. In the field experiments, significantly higher mortality counts were recorded in treated areas both indoor- and outdoor-placed AGOs. Two-factor repeated measures ANOVA followed by Tukey's test confirmed that the mean mortality count is high for the developed AGOs both indoor and outdoor settings. The developed AGO can be deployed to control both indoor and outdoor dengue vector mosquito populations, and in dengue-risk areas, the ovitrap will be supportive to local health authorities to enhance the efficiency of future vector control programs.
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http://dx.doi.org/10.1155/2020/9567019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7071800PMC
December 2020

Could quantitative real-time polymerase chain reaction assay serve as an alternative test method to evaluate human epidermal growth factor receptor 2 status of gastric carcinoma in the South Asian setting?

Indian J Gastroenterol 2019 08 10;38(4):317-324. Epub 2019 Aug 10.

Department of Chemistry, Faculty of Science, University of Colombo, Colombo, Sri Lanka.

Background: Human epidermal growth factor receptor 2 (HER2) protein overexpression and/or HER2 gene amplification are/is linked to a dismal outcome of gastric carcinoma (GCa). Immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) are key methods to identify patients for HER2 targeted therapy. Drawbacks of both the methods warrant novel tests. Hence, we evaluated the value of quantitative real-time polymerase chain reaction (qPCR) as an alternative test method, relative to IHC to detect HER2 status of GCa and to find relationship between these  results with demographic/clinicopathological data.

Method: Twenty GCa patients with known IHC HER2 scores were evaluated. qPCR was performed for the HER2 gene and amyloid precursor protein (reference gene) in formalin-fixed paraffin-embedded GCa tissue. Cycle threshold values (Ct) were analyzed using the Pfaffl method to detect HER2 gene amplification.

Results: HER2 positivity rates by IHC and qPCR were 20% and 35%, respectively. The sensitivity and specificity of qPCR were 67% and 76%, respectively, relative to IHC. qPCR results were reproducible. The diagnostic consistency between IHC and qPCR (κ = 0.146) was slightly agreeable (0.01 < k < 0.20), with a 65% concordance. Based on McNemar's test, there was no significant difference between the results of the two tests. IHC HER2 protein expression had relationship with the tumor (TNM) stage and Lauren histological type (p < 0.05). Positive HER2 gene expression by qPCR showed relationship with depth of invasion, lymph node involvement, and degree of differentiation (p < 0.05).

Conclusion: Cost-effective qPCR could serve as an alternative test method for detection of HER2 status of GCa. Both HER2 overexpression by IHC and gene amplification by qPCR are associated with adverse clinicopathological features.
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http://dx.doi.org/10.1007/s12664-019-00955-6DOI Listing
August 2019
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