Assembly of Vaccinia virus: role of the intermediate compartment between the endoplasmic reticulum and the Golgi stacks

The structure and assembly of vaccinia virus was characterized. The study protocol involved phospholipid analysis of the two distinct infectious forms, the intracellular naked virus (INV) and the extracellular enveloped virus, as well as immunoelectron microscopy using antibodies against different subcellular compartments. The results showed that the vaccinia virus becomes enwrapped by a membrane cisterna from the intermediate compartment between the endoplasmic reticulum and the Golgi apparatus, thus acquiring a double membrane in one step. This disproves the notion of de novo biogenesis of lipid envelpes by INVs.