The generation and propagation of defective-interfering particles of semliki forest virus in different cell types

Abstract

We have examined the generation and propagation of Semliki Forest virus (SFV) defective-interfering (DI) particles produced during high multiplicity serial passaging in six clonally purified cell lines and in primary chicken embryo fibroblasts. In all but one cell type (one of two lines of HeLa cells examined) DI particles were generated after 11 or fewer passages. In the nonproducer HeLa line, DI particles, although not generated, could readily be propagated. From an analysis of the intracellular RNA species specified by DI particles in the course of serial passaging we show that, with one exception, all cell types capable of generating SFV DI particles ultimately generate a single type of DI particle whose genetic material is about one-sixth the size of the genome of standard virus. We also show that in this generation process DI particles containing between one-half and one-fifth of the standard virus genome are produced and that the passage longevity of these intermediate particles differs markedly from cell type to cell type. Finally by comparing the oligonucleotide fingerprints of the DI RNAs with that of standard virus RNA, we define the deletion events which occur in each cell type during DI particle generation.