A sindbis virus variant with a cell-determined latent period

A rapidly growing variant of Sindbis virus was isolated by repeated selection for virions released from cells at 5.5 hr postinfection. The variant, SB-RL, was cloned from the eleventh 5.5-hr passage. SB-RL was characterized by a significant reduction in latent period and an increased rate of penetration. These characteristics were expressed only in the baby hamster kidney cell line used for the original selection. In other cell lines, the latent period and rate of penetration were identical to wild-type Sindbis. SB-RL also produced higher virus titers and exhibited an increased rate of RNA synthesis. However, the expression of these characteristics was independent of cell type. SB-RL could be distinguished from the parental Sindbis strain on the basis of neutralization of infectivity, suggesting an alteration in the E2 glycoprotein of SB-RL.