Figure 1.

Western blots of MLV pseudotypes. (A) MLV particles were produced by cotransfection of 293T cells with plasmids expressing MLV gag and either the indicated receptor constructs or an empty pCDNA3 vector (MLV–pCDNA3). Purified MLV–pCDNA3, MLV–CCR5, MLV–CXCR4, and MLV–CD4 particles were analyzed by Western blot using antibodies against the various receptors and the MLV gag protein as indicated. (B) Fractions from an equilibrium density gradient containing MLV–CCR5 were analyzed by SDS-PAGE and Western blot using antibodies to CCR5 (Upper) and MLV-gag (Lower). Densities of each fraction are indicated (in g/ml), and a CCR5 standard was run in the far right lane to control for expression.