A SINDBIS VIRUS MESSENGER-RNA POLYNUCLEOTIDE VECTOR ACHIEVES PROLONGED AND HIGH-LEVEL HETEROLOGOUS GENE-EXPRESSION IN-VIVO

The direct intramuscular delivery of-naked plasmid DNA has been demons trated to allow expression of encoded heterologous genes in the target myocytes. The method has been employed to elicit immunization based u pon delivery of antigen encoding plasmid DNA. For application in the c ontext of achieving anti-tumor immunization against antigenic transfor ming oncoproteins, delivery of plasmid DNAs encoding these molecules w ould create significant potential safety hazards. As an alternative to DNA polynucleotide vectors, we explored the utility of mRNA vehicles for inducing foreign gene expression in muscle cells in vivo. Syntheti c reporter-gene encoding mRNA transcripts were derived for this analys is. The sindbis virus vector was also used to derive luciferase mRNA t ranscripts which possessed self-replication capacity. In these studies , it could be shown that the replicative vector was capable of directi ng significantly elevated levels of reporter gene expression in myocyt es compared to a non-replicative mRNA species. In addition, the replic ative species was capable of achieving significantly prolonged levels of in vivo gene expression compared to non-replicative mRNA. Both of t hese characteristics will make replicative mRNA vectors of utility for polynucleotide-based immunization protocols.