PRODUCTION OF VIRAL ANTIGENS IN CULTURE FLUID OF C6/36 MOSQUITO CELL LINE INFECTED WITH DENGUE TYPE 4 VIRUS STRAINS ISOLATED FROM PATIENTS WITH DIFFERENT CLINICAL SEVERITIES

Viral antigen production was examined in the culture fluid of Aedes albopictus clone C6/36 cell line incubated at 28°C and 37°C after infection with four strains of dengue type 4 (DEN-4) virus which were isolated from patients with different clinical severities. During the observation period from day 1 to day 18, the number of infected cells at each day for all four strains did not show any significant difference (P >0.05). Antigen production as determined by the hemagglutination (HA) test and sandwich enzyme linked immunosorbent assay (ELISA) was higher at 28°C than at 37°C for all four DEN-4 virus strains examined. The amount of viral antigen produced was highest for CT93-74 strain (dengue hemorrhagic fever syndrome (DHF) grade II) and was significantly different in comparison to other strains (P <0.001). This strain was followed by CT93-158 and CT93-129 strains (both of DHF grade I), and CT93-77 strain (dengue fever (DF)). The viral antigen production was apparently proportional to the clinical severity of the patient from whom the virus was isolated. These results show that CT9374 strain could be used to produce DEN-4 virus antigen of sufficiently high titer in the C6/36 cell culture instead of classical extraction of this antigen from suckling mouse brains.