Phenotypic Changes in the Flavivirus Kunjin after a Single Cycle of Growth in an Aedes albopictus Cell Line

Summary The properties of Kunjin virus produced during acute infections of Aedes albopictus (Aal) mosquito cells were compared with those of the virus progeny from the C6/36 clone of mosquito cells and from Vero cells. Titres of 108 p.f.u./ml or greater were obtained from all cells, but significant haemagglutinin activity was associated only with progeny from Vero and C6/36 cells. Kunjin virus from Aal cells adsorbed to goose erythrocytes and blocked haemagglutination by virus from Vero or C6/36 cells. High titres of virus from Aal cells were obtained only when the cells were grown in the presence of 10% or higher concentrations of foetal calf serum, and large losses were encountered when this virus was concentrated by pelleting or by precipitation with polyethylene glycol, and during rate-zonal sedimentation through sucrose gradients. Because of these losses, and because of poor incorporation of [35S]methionine in Aal cells, only analytical amounts of labelled structural proteins were recovered. Electropherograms showed that the presumptive envelope protein E of Kunjin virus from Aal cells migrated more rapidly than E of virions grown in C6/36 and Vero cells, and that the core (C) and membrane-like (M) proteins were not detectably labelled. All the observed changes in phenotype were reversed during one cycle of growth in Vero cells.