Characterization of purified HIV-1 particles. HIV-1 virions were purified from cell culture supernatants (see Materials and Methods for details). (A), Western Blot and silver stain analysis of the indicated virion preparations for major viral particle constituents. (B) Single round of replication analysis on TZM cells with the particle preparations analyzed in A. The assay was performed analogous to that described in Fig. 1A. (C) Relative amounts of total cell culture supernatant p24 recovered after the optiprep procedure. Depicted are average p24 amounts recovered in the virion preparation procedure relative to the total input from four independent purifications with the indicated standard error of the mean.