MEMBRANE-ANCHORED INCORPORATION OF A FOREIGN PROTEIN IN RECOMBINANT INFLUENZA VIRIONS

The RNA polymerase I system for in vivo synthesis of recombinant influ enza vRNA molecules was used for the expression of a chimeric protein, consisting of the 341-amino-acid ectodomain of the glycoprotein E2 of classical swine fever virus and the 37-amino-acid C-terminal membrane anchor of the influenza virus hemagglutinin (HA). During infection wi th an influenza A helper virus the amplified pseudo-viral RNA was pack aged into progeny virions together with influenza vRNA segments. The f oreign fusion protein E2-HA was shown to be physically incorporated in to the viral envelope. Incorporation of a third major glycoprotein int o the envelope did not affect biological functions of HA and neuramini dase that are required for the generation of infectious virus particle s. Based on mutational analyses of the cytoplasmic tail of E2-HA fusio n proteins three modes of interaction during virus budding have been o bserved: nonspecific low-level incorporation (truncated tails), specif ic full-level incorporation (wild-type amino acid sequence or minor va riations of it), and exclusion from incorporation (elongated tails). ( C) 1998 Academic Press.