MUTANT OF SINDBIS VIRUS WHICH IS RELEASED EFFICIENTLY FROM CELLS MAINTAINED IN LOW IONIC-STRENGTH MEDIUM

Experiments many years ago showed that reducing the ionic strength of the medium in which Sindbis virus-infected chick embryo fibroblasts we re maintained prevented the release of progeny virus into the medium. It was proposed at that time that the susceptibility of virus release to inhibition by low ionic strength (LIS) medium might be determined b y the properties of the viral envelope proteins. We thought that if su ch were the case, it might be possible to obtain a viral mutant which is resistant to the inhibitory effect of LIS medium. We report here th at we were able to isolate such a mutant of Sindbis virus, and that we identified two amino acids (Glu(23) and Thr(76)) which, when present in the E2 protein, made possible the release of infectious progeny vir us from cells incubated in LIS medium. (C) 1995 Academic Press, Inc.