Detection of dengue virus antigens in cultured cells by using protein A-gold-silver staining (pAgs) method.

A protein A-gold-silver (pAgs) staining was developed to detect dengue virus antigens in cultured cells. The method can be carried out in either newly-subcultured or monolayered cells. Dengue virus-inoculated C6/36 clone of Aedes albopictus cells and human endothelial cells appeared brown-yellowish color on the peripheral membrane of the infected cells. In many cases, the infected C6/36 cells appeared darker than that of the infected endothelial cells. The positive results from the inoculated C6/36 cells usually appeared as early as 2 days post-inoculation for types 1, 2, and 4 of dengue viruses and 3 days for the dengue 3 virus. The same batch of specimens detected by direct immunofluorescence antibody test (DFA) showed positive 4 days post-inoculation for the types 2, 3, and 4 of dengue viruses and 6 days for the dengue 1 virus. The result also showed that all pAgs-positive specimens were also DFA-positive, but not vice versa. It suggested that pAgs is not only sensitive but also specific for dengue virus detection from inoculated cultured cells.