TABLE 2.

Infection of HT1080 cells with HIV- and MLV-based GPR particles^a

Infection procedure	Titer (CFU/ml)
	HIV-GPR (LGFPRNL)	MLV-GPR (LZRNL)
GPR-VSV complex onto HT1080 cells	1.2 × 105	6.9 × 105
	1.4 × 105	4.0 × 105
GPR particles onto VSV-G-treated HT1080 cells	7.8 × 104	3.8 × 105
	9.0 × 104	9.8 × 104
GPR particles onto untreated cells followed by VSV-G addition	1.1 × 105	4.0 × 105
	8.2 × 104	2.4 × 105

^aAll infections were carried out in duplicate in the presence of Polybrene (8 μg/ml), using identical amounts of GPR particle preparations. Complexes of GPR particles with VSV-G and treatment of cells with VSV-G were performed as described in the text.