HIGH-EFFICIENCY INCORPORATION OF FUNCTIONAL INFLUENZA-VIRUS GLYCOPROTEINS INTO RECOMBINANT VESICULAR STOMATITIS VIRUSES

We derived recombinant vesicular stomatitis virus (VSV) expressing eit her influenza virus hemagglutinin (HA) or neuraminidase (NA) glycoprot eins from extra genes inserted in the viral genome, The HA protein was expressed from a site downstream of the VSV glycoprotein (G) gene, wh ile NA protein was expressed from a site upstream of the VSV G gene, T he HA protein was expressed at lower levels than the VSV G protein, wh ile the NA protein was expressed at higher levels, as expected from th e gradient of VSV transcription that follows the gene order, The HA an d NA proteins were transported to the cell surface and were functional as demonstrated by hemadsorption, hemolysis, and NA assays. Biochemic al analysis showed that both HA and NA proteins were incorporated into VSV particles at high levels, although there was a preference for inc orporation of the VSV G protein over either of the influenza virus pro teins, Immunoelectron microscopy of the recombinants showed that the p articles derived from the recombinants were mosaics carrying both the VSV G protein and the influenza virus membrane glycoproteins. These re sults extend earlier studies showing incorporation of the cellular gly coprotein CD4 and two other viral glycoproteins into VSV particles, Ou r results indicate that there is significant space in the VSV membrane that can accommodate foreign membrane proteins and that the foreign p rotein can represent as much as 35% of the total protein in the viral envelope, Incorporation of foreign proteins into VSV virions can, in m any cases, occur passively in the absence of specific incorporation si gnals.