CONSTRUCTION AND CHARACTERIZATION OF ENCAPSIDATED POLIOVIRUS REPLICONS THAT EXPRESS BIOLOGICALLY-ACTIVE MURINE INTERLEUKIN-2

Poliovirus genomes have been constructed in which the capsid genes hav e been substituted with the murine gene encoding interleukin-2 (IL-2) (referred to as replicons). One replicon contained the gene for IL-2 i n place of the poliovirus capsid VP2 and VP3 genes, and a second repli con was constructed that contained the murine IL-2 substituted for the poliovirus VP3 and VPI genes, The IL-2 genes were cloned into the rep licon so as to maintain the translational reading frame with the remai ning poliovirus proteins. Transfection of either replicon into cells r esulted in the expression of replicon-encoded proteins and replication of replicon RNA. Using a procedure developed in this laboratory, we h ave encapsidated these replicons into authentic polio virions by passa ging the replicons in the presence of a recombinant vaccinia virus, VV P1, which expresses the capsid precursor, P1, protein. Using a quantit ative immunoassay, we determined that the majority of the IL-2 produce d remained intracellular, with approximately 1%-2% released from the i nfected cells, and that the IL-2 was biologically active. The results of these studies demonstrate the utility of poliovirus replicons for e xpression of small bioactive molecules and are discussed with respect to future applications as immune adjuvants as well as potential new tu mor therapies.