Plasmid DNA-based alphavirus expression vectors for nucleic acid immunization.

: Alphavirus-derived vectors are being developed for vaccine, gene therapy and recombinant protein production applications, based in part on observations of transient, high level expression of heterologous genes in eukaryotic cells. Efficient means for launching the RNA alphavirus genome from RNA polymerase II expression cassettes have been developed, obviating the need for transcription in vitro of long cDNA templates. One system being developed from this technology is a layered plasmid DNA vector which, when inoculated directly into animal muscle, launches a self-amplifying alphavirus vector, resulting in subsequent induction of comparatively robust immune responses specific for the expressed antigen.