Comparison of two methods with potential application in the detection of viremia produced by clinical dengue virus isolates

Most clinical isolates do not form clear plaques on cell monolayers. Therefore, they can not be detected by plaque assay. Reliable alternative methods for the measurement of viremia are thus required for the validation of the protective efficacy of dengue vaccine candidates against circulating virus strains. In this work, two different cell culture formats (25 cm2 flasks and 24-well plates) were used to isolate dengue virus from 48 serum samples collected from monkeys. Only 8 dengue positive sera were detected after isolation in 24-well plates. In contrast, the 25 cm2-flask format allowed the detection of virus in 22 serum samples, suggesting that the Vero cell monolayer area influences virus isolation. We also compared the sensitivity of ELISA and flow cytometry for detecting dengue virus after isolation in Vero cell culture. Both techniques showed 100% specificity and similar sensitivity. In addition, there was a high agreement rate and correlation between the two techniques. Our findings suggest that ELISA and flow cytometry have similar capacity to detect and quantify dengue virus from monkey serum samples after virus isolation in cell culture.