Replicative intermediate of an arbovirus.

One hour after infection of chick fibroblasts with Semliki Forest virus (SFV), a viral ribonucleic acid (RNA) structure is present which has many of the properties described for the replicative intermediate of several RNA bacteriophages. These properties include a polydisperse nature on sucrose density gradient analysis, ribonuclease resistance, a variation in sedimentation pattern associated with changes in salt concentration, and recovery of infectious viral RNA upon denaturation. Most of the replicative intermediate present in SFV infection appears to be membrane-associated.