TABLE 1.

Properties of mutant GALV SU proteins

SU protein	Processinga	Incorporationb	Bindingc	Titer (106 BFU/ml)d
GALV R213-260	+	+	ND	0.0002 ± 0.4
GALV I264	+	+	0.03	1.3 ± 0.3
GALV I219	+	+	0.95	0.43 ± 0.6
GALV I10	+	+	0.81	0.000001
FeLV-B	+	+	1.00	NDe
GALV	ND	ND	ND	3.8 ± 0.4

^aSU protein was detected (+) or not (−) in lysates from transiently transfected 293T cells, as described in Materials and Methods.

^bSU protein was present (+) or absent (−) in retroviral vector particles produced in 293T cells at 35°C.

^cAverage shift in fluorescence intensity observed with vector particles bound to MDTF-Pit1 cells, detected by antibody C11D8 in a FACS-based binding assay, normalized to the average mean fluorescence observed with FeLV-B bound to MDTF-Pit1 cells (1.0). The average values for negative-control MDTF cells with GALV I₁₀, GALV I₂₁₉, and FeLV-B were 0.018, 0.019, and 0.016, respectively; these values were subtracted from those obtained on MDTF-Pit1 cells. Values are derived from from three independent experiments.

^dTiters are expressed as the average numbers of blue foci (BFU) ± standard errors of the means on MDTF-Pit1 target cells, from three experiments.

^eND, not done.