TABLE 1.

Luciferase activity in Schneider 2 cells infected by retroviral vector LNhsp70lucL pseudotyped by gyp-ENV or VSV-G envelope

Envelope expression	Light units/μg of proteina
	No centrifugation		Centrifugation,b no heat shock
	No heat shock	Heat shock
Transient
No envelope	0.7d	NDc	0.7d
gyp-ENV	1.4 ± 0.4	ND	19.7 ± 12.3
VSV-G	998.0 ± 223.0	ND	2352.0 ± 148.5
Established
No envelope	6.7d	3.5d	3.8d
gyp-ENVe	20.8 ± 10.9,  21.0 ± 12.3	40.3 ± 14.7,  31.6 ± 4.4	243.7 ± 111.6,  255.3 ± 67.5

^aThe data are means of three assays ± standard deviations except as indicated. 

^bCells in a tissue culture well plus virus were centrifuged at 1,000 × g for 1 h. 

^cND, not determined. 

^dSingle assay. 

^eResults obtained with two different supernatants in two separate experiments.