CHARACTERIZATION OF HUMAN FOAMY VIRUS PROTEINS EXPRESSED BY RECOMBINANT VACCINIA VIRUSES

We report the generation of recombinant vaccinia viruses (VVs) express ing the gag, pol, bel-1, and bet open reading frames of human foamy vi rus (HFV), and the establishment of a transient, VV-T7 RNA polymerase- directed expression system for the HFV env gene, The correct expressio n of the HFV proteins was demonstrated by radioimmunoprecipitation usi ng monospecific rabbit antisera, by analysis of the subcellular distri bution (for VVgag, VVpol, VVbel-1, and VVbet), and by the ability to i nduce syncytium formation (for the env expression system), The HFV pol gene was successfully expressed using its own ATG start codon, Foamy viruses are regarded as retroviruses with intracytoplasmatic capsid as sembly, However, when VVgag and VVpol were used to study the HFV Gag-P ol protein interaction and particle formation, no HFV capsid structure s were observed in singly or doubly infected cells, In addition, no cl eavage of the pr74(gag) precursor molecule by the pol-encoded protease was detected in doubly infected cells, Our results indicate that foam y virus particle assembly is fundamentally different from that of othe r retroviruses.