NOVEL INFECTIOUS PARTICLES GENERATED BY EXPRESSION OF THE VESICULAR STOMATITIS-VIRUS GLYCOPROTEIN FROM A SELF-REPLICATING RNA

Self-propagating infectious particles were produced in animal cells tr ansfected with an RNA replicon encoding a single viral structural prot ein, the vesicular stomatitis virus glycoprotein (VSV-G). The replicon is derived from an alphavirus, Semliki Forest virus (SFV), and encode s the SFV RNA replicase, but none of the SFV structural proteins. Afte r transfection of the replicon into tissue culture cells, expression o f G protein spread from small foci throughout the culture. Supernatant s from the cells contained infectious, virus-like particles that could be passaged and were neutralized by anti-VSV serum. The majority of t he infectious particles were smaller and less dense than either VSV or SFV. Characterization by electron microscopy showed membrane-envelope d vesicles that contained the VSV-G protein. Infectious particles were apparently generated by budding of vesicles containing VSV-G protein and the RNA replicon. These experiments reveal that an enveloped infec tious agent can be much simpler than previously thought.