Replicon-based vectors of positive strand RNA viruses

Vectors based on self-replicating RNAs (replicons) of positive strand RNA viruses are becoming powerful tools for gene expression in mammalian cells and for the development of novel antiviral and anticancer vaccines. A relatively small genome size and simple procedure allow rapid generation of recombinants. Cytoplasmic RNA amplification eliminates nuclear involvement and leads to extremely high levels of gene expression, and continuous synthesis of double stranded RNA results in induction of enhanced immune responses, making these vectors unique among other gene expression systems. Both cytopathic replicon vectors allowing short-term transient expression, and non-cytopathic replicon vectors allowing long-term stable expression, are now available with the choice of vector depending on particular applications.