Recombinant proteins produced by vaccinia virus vectors can be incorporated within the virion (IMV form) into different compartments

Vaccinia virus (VV) is one of the largest and most complex of animal viruse s, with a virion that contains about 100 different polypeptides. Assembly o f the viral proteins occurs in discrete cytoplasmic sites leading to format ion of two infectious forms, an abundant (>90%) intracellular mature virus (IMV) with an envelope, and a minor extracellular enveloped virus (EEV) wit h an extra membrane acquired from the trans-Golgi network. It has been show n that while EEV contains in the outer membrane cellular proteins probably acquired during virus release from cells, however, IMV exclude host protein s during assembly. Since VV recombinants (VVr) expressing genes of interest are candidates as potential vaccines against: pathogens and cancer, it bec omes important to know if VVr can acquire foreign proteins during morphogen esis. In this investigation we show that purified virions (IMVs) from VVr c an incorporate foreign proteins into different sites in the virus particle. By sequential fractionation of virion compartments with detergents, we fou nd foreign proteins in the lipid envelope (cytokine IL-12 and CS antigen of Plasmodium yoelii), as part of a protein matrix-like membrane (HIV-1 gp41 of env), or more closely associated with me core containing the DNA complex es (HIV-1 gp160; a multiepitopic protein with the V3 loop of HIV-I Env from different isolates, and P-galactosidase). Similar findings were observed w ith purified virions derived from the WR strain as well as from the highly attenuated modified vaccinia virus Ankara (MVA) strain. These observations should be taken into consideration when VVr are used in clinical trials or in other vaccination approaches.