TABLE 1.

Enhanced packaging of an HSV amplicon vector

Vector	Cell linea	Vector titerb (104 BFU/ml of lysate)	Virus titerc
pHSVlac	293T	1.5	<10
pHSVlacOri	293T	2.7	<10
pHSVlac	BHK	2.4	<10
pHSVlacOri	BHK	1.8	<10

^aThe pBAC-V2 clone was used as the HSV-1 helper construct in all transfections. 

^bSerial 10-fold dilutions of the lysates were plated on a confluent lawn of Vero cells, and the cells were assayed for β-galactosidase activity after 2 days by using X-Gal histochemistry. 

^cSerial 10-fold dilutions of the lysates were plated on a confluent lawn of Vero cells, and plaques were counted after 3 days. A titer of <10 reflects the fact that no helper virus was detected in a 10⁻¹ dilution of the lysate, which was the lowest dilution tested in this experiment.