Transfection of HEK293 cells by (a) MLV-A and Chi/M-VLP (pH 3 and pH 4, 5 μg/109 M-VLPs) and (b) MLV-A and Lip587/M-VLP, Lip505/M-VLP and Lip550/M-VLP (10 μg/109 M-VLPs) in the presence of drug inhibitors. Luciferase activity in treated cells was normalized to expression in untreated cells. Cellular uptake of (c) Chi/M-VLP (pH 3 and pH 4, 5 μg/109 M-VLPs) and (d) Lip587/M-VLPDiD, Lip505/M-VLPDiD and Lip550/M-VLPDiD (10 μg/109 M-VLPs) in the presence of drug inhibitors normalized to corresponding values in untreated cells. Error bars represent SD, n=3 (# - p < 0.05, ## - p < 0.02, ### - p <0.002 and * - p <0.0001).