FOREIGN GLYCOPROTEINS EXPRESSED FROM RECOMBINANT VESICULAR STOMATITISVIRUSES ARE INCORPORATED EFFICIENTLY INTO VIRUS-PARTICLES

In a previous study we demonstrated that vesicular stomatitis virus (V SV) can be used as a vector to express a soluble protein in mammalian cells. Here we have generated VSV recombinants that express four diffe rent membrane proteins: the cellular CD4 protein, a CD4-G hybrid prote in containing the ectodomain of CD4 and the transmembrane and cytoplas mic tail of the VSV glycoprotein (G), the measles virus hemagglutinin, or the measles virus fusion protein. The proteins were expressed at l evels ranging from 23-62% that of VSV G protein and all were transport ed to the cell surface. In addition we found that all four proteins we re incorporated into the membrane envelope of VSV along with the VSV G protein. The levels of incorporation of these proteins varied from 6- 31% of that observed for VSV G. These results suggest that many differ ent membrane proteins may be co-incorporated quite efficiently with VS V G protein into budding VSV virus particles and that specific signals are not required for this co-incorporation process. In fact, the CD4- G protein was incorporated with the same efficiency as wild type CD4. Electron microscopy of virions containing CD4 revealed that the CD4 mo lecules were dispersed throughout the virion envelope among the trimer ic viral spike glycoproteins. The recombinant VSV-CD4 virus particles were about 18% longer than wild type virions, reflecting the additiona l length of the helical nucleocapsid containing the extra gene. Recomb inant VSVs carrying foreign antigens on the surface of the virus parti cle may be useful for viral targeting, membrane protein purification, and for generation of immune responses.