hGas6 enhances binding and transduction of lentiviral vectors at low concentrations. (A) HMVEC were incubated with hProtein S, hGas6, or hGas6(γ-) at various concentrations (shown by ng/ml and M), followed by transduction with the 2.2 1L1L pseudotype (100 ng p24/ml). (B) 1×105 HMVEC were incubated with 100 ng/ml of hGas6 or hGas6(γ-) in PBS (+), or hGas6 in PBS (EGTA), then incubated with the 2.2 1L1L pseudotype labeled by EGFP (250 µl, 100 ng p24/ml). (C) HMVEC were incubated with PBS (+) or PBS (+) containing hGas6 (100 ng/ml), followed by transduction with various pseudotypes. vEnv(−) was also used for transduction. N.D.: Not Detected. (D) HMVEC were incubated with PBS (+) or hGas6 (100ng/ml) in PBS (+), followed by transduction with the 2.2 pseudotype with or without conjugation with αHLA Ab (2 µg/ml). (See also Figure S2)