GaLV Env levels and titers of pseudotyped vectors. A. Western blot of a representative experiment showing levels of GaLV TM, HIV-1 p24, MLV p30 and actin in cell lysates and pelleted supernatants from 293T cells co-transfected with plasmids expressing GaLV Env, together with pCgp, R8.2, R8.91 or a control (Ctrl.) plasmid, as indicated. Also shown is a quantitative analysis of the steady-state levels of GaLV TM in cell lysates, made relative to the levels in the presence of control plasmid. Results are mean of three independent experiments. B. Titers of GaLV Env and VSV G pseudotyped retroviral (pCgp) and lentiviral (R8.2 and R8.91) vectors, as indicated, expressed as transducing units per ml (TU/ml). * indicates no detectable titer.