ELISA as an alternative tool for epidemiological surveillance for dengue in mosquitoes: a report from Thailand

Background & objectives: Dengue fever (DF), dengue hemorrhagic fever (DHF) and dengue shocksyndrome (DSS) are the re-emerging infectious diseases caused by the four serotypes of dengue(DEN) virus, type 1 to 4, belonging to the family Flaviviridae and genus Flavivirus. In the absenceof a safe and effective mass immunisation, the prevention and control of dengue outbreaks dependupon the surveillance of cases and mosquito vector. The aim of this work is to test enzyme-linkedimmunosorbent assay (ELISA) tool for the virological surveillance of dengue.Methods: Virus-infected Aedes mosquitoes were collected from the field in order to serve as anearly warning monitoring tool for dengue outbreaks. In a prospective field study conducted fromApril to September 2000, female adult Aedes mosquitoes were caught from selected dengue-sensitivearea in Chombung district, Ratchaburi province and assayed by ELISA.Result: Approximately 18.3% were found positive for dengue virus.Conclusion: This can imply that ELISA can be an alternative tool for epidemiological surveillancefor dengue in mosquitoes

Host cell killing by the West Nile Virus NS2B–NS3 proteolytic complex: NS3 alone is sufficient to recruit caspase-8-based apoptotic pathway

AbstractThe West Nile Virus (WNV) non-structural proteins 2B and 3 (NS2B–NS3) constitute the proteolytic complex that mediates the cleavage and processing of the viral polyprotein. NS3 recruits NS2B and NS5 proteins to direct protease and replication activities. In an effort to investigate the biology of the viral protease, we cloned cDNA encoding the NS2B–NS3 proteolytic complex from brain tissue of a WNV-infected dead crow, collected from the Lower Merion area (Merion strain). Expression of the NS2B–NS3 gene cassette induced apoptosis within 48 h of transfection. Electron microscopic analysis of NS2B–NS3-transfected cells revealed ultra-structural changes that are typical of apoptotic cells including membrane blebbing, nuclear disintegration and cytoplasmic vacuolations. The role of NS3 or NS2B in contributing to host cell apoptosis was examined. NS3 alone triggers the apoptotic pathways involving caspases-8 and -3. Experimental results from the use of caspase-specific inhibitors and caspase-8 siRNA demonstrated that the activation of caspase-8 was essential to initiate apoptotic signaling in NS3-expressing cells. Downstream of caspase-3 activation, we observed nuclear membrane ruptures and cleavage of the DNA-repair enzyme, PARP in NS3-expressing cells. Nuclear herniations due to NS3 expression were absent in the cells treated with a caspase-3 inhibitor. Expression of protease and helicase domains themselves was sufficient to trigger apoptosis generating insight into the apoptotic pathways triggered by NS3 from WNV