Our results show that the DV1 RSPs produced by HeLa-prME cell line mimic maturation and secretion of DV1, thus providing a useful tool to study the interaction between DV and host cells during viral egress. To identify host factors that could either enhance or reduce production of DV RSPs, we first developed a quantitative assay to relatively quantify levels of secreted particles in supernatant of HeLa-prME cells. The chemiluminescence dotblot (CLDB) assay is based on the concentration of RSPs from cell supernatant on PVDF membranes, followed by detection of E with a specific horseradish peroxidase (HRP)-conjugated antibody and quantification of substrate-induced luminescence using a luminometer. Our data using purified E protein of known concentrations showed that, when ranging between 400 pg to 40 ng, E protein on PVDF membrane displayed a very good linear correlation with the luminescence density in CLDB assay ( Figure 7A ). The CLDB was first used to estimate the RSPs yield from HeLa-prME cell line, and we found that the concentration of E protein in supernatant of HeLa-prME cell line was around 500-1000 ng/ml under the culture condition used for siRNA transfection (data not shown). We then screened a siRNA library that consisted of 122 genes which target cellular membrane trafficking using the HeLa-prME cell line. Non-targeting siRNA (NT) and siRNA targeting DV1 prME were added as controls. Library and control siRNAs were transfected in triplicates on 96-well plates. Levels of RSPs secreted by siRNA transfected HeLa-prME were measured by CLDB assay from 40 microliters of supernatant from each well. Levels of E protein in cell supernatant were expressed in relative luminescence units and ratios to that of NT controls were shown in Figure 7B . T test was used to assess the statistical significance of differences between each sample and NT. Differences were considered statistically significant when P,0.05. We observed that targeting of 23 genes resulted in significant reduction of DV1 RSPs amounts in supernatants whereas targeting of 22 other genes induced a significant increase. For instance, our results showed that downregulation of ADP-ribosylation factor 1 (ARF1), which regulates secretory membrane transport [30] , resulted in 3 fold decrease of DV1 RSPs in cell supernatant, suggesting its involvement in the secretion of DV. Some genes whose down-regulation enhanced levels of DV RSPs in the supernatant are involved in endocytosis, such as the three dynamins which show a 2 to 4 fold increase in dengue RSPs secretion. These proteins are involved in the budding process or in the transport of vesicles [31] . Such an enhancement might have been due, at least in part, to a blockade in the re-internalization of secreted RSPs by HeLa-prME cells.