TABLE 1.

Formation of G418-resistant colonies after infection with hybrid viruses in comparison with rAAV^a

MOI (genomes per cell)	% Formation of G418-resistant colonies after 4 weeks of selection (SEM)
	rAAV1	ΔAd.AAV1	Ad.AAV1	Ad.AAV1-Δ2ITRs
101	<0.001	<0.001	<0.001	<0.001
102	0.01	0.01	0.06	<0.001
103	2.7 (1.6)	1.3 (1)	5.4 (3.0)	<0.001
104	90.8 (7.0)	48.0 (8.9)	12.9 (7.2)	<0.001
105	N/A	93.1 (5.4)	3.8 (2.1)	<0.001
106	N/A	100	<0.001	<0.001
107	N/A	100	<0.001	<0.001

^aConfluent SKHEP-1 cells (12-well plates) were infected with different MOIs of rAAV1 (stock, 10¹⁰ genomes per ml), ΔAd.AAV1 (stock, 5 × 10¹² genomes per ml), Ad.AAV1 (stock, 10¹³ genomes per ml), and Ad.AAV1Δ1ITR (stock, 9 × 10¹² genomes per ml) in a volume of 100 μl. Twenty four hours after infection, cells were washed, trypsinized, and plated at different dilutions. G418 was added 24 h after plating, and selection was performed for 4 weeks. G418-resistant colonies contained, on average, >5 × 10⁴ cells (at least 16 cell divisions). A significant number of small colonies visible at 2 weeks postinfection did not survive continued selection, probably due to episomal vector expression. Cells infected with first-generation Ads with MOIs greater than 10⁴ developed cytopathic effects during the first week of selection. The rAAV titer was not high enough to perform infection studies with MOIs greater than 10⁴. The colony formation is expressed as percentage of the number of colonies after selection to the number of cells initially seeded for selection. Results are based upon three independent experiments. N/A, nonapplicable.