FIG. 1.
Dose-dependent binding of CARex-Fc-Ad2 clusters to THP-1 cells. (A) [35S]methionine-labeled Ad2 (2.5 × 109 particles, 81,000 cpm) was incubated with different amounts of CARex-Fc in 20 μl of ice-cold phosphate-buffered saline for 45 min, added to 5 × 105 THP-1 cells in 0.5 ml of cold RPMI containing 0.2% BSA, and incubated in the cold on a rocking platform for 60 min. The cells were washed twice in cold RPMI-BSA and resuspended in 0.2% SDS, and the amount of cell-associated Ad2 was determined by scintillation counting. Results are expressed as percentages of bound Ad2. (B) Ad2 (1.68 μg) was incubated with (a) or without (b) CARex-Fc (0.43 μg) in 13 μl of PBS on ice for 45 min, spotted on an EM grid, negatively stained with uranyl acetate, and observed by TEM (×12,000). CARex-Fc alone (0.43 μg in 13 μl) is shown in panel c. Bar = 1 μm.