Targeting a foreign protein into virion particles by fusion with the Vpx protein of simian immunodeficiency virus

The Vpx and Vpr proteins of the primate immunodeficiency viruses are stoichiometrically incorporated into virion particles. The chloramphenicol acetyltransferase (CAT) enzyme, when fused to a sufficient portion of the simian immunodeficiency virus (SIVmac239) Vpx protein, was incorporated into virions and retained enzymatic activity. An analysis of the replication of this virus compared with the replication of revertants and control viruses encoding nonpackageable Vpx-CAT fusion proteins suggested that the observed delay in replication was due to cis-acting effects of the CAT gene insertion rather than to the presence of the Vpx-CAT fusion protein in the virions. These studies indicate that, in host cells where Vpx and Vpr function is not required for efficient SIVmac replication, functional enzymes can be incorporated into virions by fusion with the Vpx protein. This approach could be utilized for study of the function and localization of Vpx and/or Vpr proteins during virus replication and for attempts to disrupt virus replication by the incorporation of foreign proteins.