SIMULTANEOUS DETECTION OF AMPLICON AND HSV-1 HELPER ENCODED PROTEINS REVEALS THAT NEURONS AND ASTROCYTOMA-CELLS DO EXPRESS AMPLICON-BORNE TRANSGENES IN THE ABSENCE OF SYNTHESIS OF VIRUS IMMEDIATE-EARLY PROTEINS

HSV-1 amplicon vectors were used to express either a cytoplasmic (beta -galactosidase) or a membrane targeted protein (TIMP-Thy1) in primary neuronal cultures, and a human astrocytoma cell line. Whereas some cel ls became infected by vector particles alone others were simultaneousl y infected by both vector and helper particles. Our results show that IEHCMV and HSV-1 IE3 promoters are able to direct transgene expression in these cells in the absence of synthesis of helper virus transactin g proteins, and stress the need of monitoring expression from both par tners of an amplicon population, in order to differentiate transgene e xpression in cells singly infected with amplicon particles, from those infected by both amplicon and helper particles.