Induction of Venezuelan equine encephalitis (Mucambo) virus by iododeoxyuridine in chronically infected 'cured' cultured mosquito cells.

Infection of cultured Aedes aegypti mosquito cells with Venezuelan equine encephalitis virus (Mucambo subtype) results in the establishment of a chronic non-cytopathic infection. Infected cells could be 'cured' when they were grown in the presence of immune serum for 3-4 passages. 'Cured' cells could then be subcultured repeatedly, in the absence of immune serum, without showing any indication of infectious virus production. When 'cured' cells were exposed to 50 microgram/ml of 5-iodo-2-deoxyuridine for 24 h, efficient induction of virus was observed. The enhancement of virus replication could not be related with increased susceptibility of the uninfected cell population. The phenotype (plaque size and virulence) of the induced virus resembles more closely that of the standard virus than the phenotype of the virus produced in chronically infected mosquito cells. These findings indicate that virus information can be maintained in chronically infected mosquito cells in a latent inducible form, and constitute indirect evidence suggesting the existence of a DNA provirus in this system.