FIG. 2.

pH dependence of exposure of the MAb E1f epitope on virus particles or E1^* ectodomains. Purified radiolabeled ectodomains (hatched bars) or intact virions (black bars) were treated at the indicated pH for 5 min at 37°C and then adjusted to pH 8.0. The samples were immunoprecipitated for 1 h on ice with a polyclonal antibody against the SFV glycoproteins or with MAb E1f and analyzed by SDS-PAGE. The amounts of E1 and E1^* directly immunoprecipitated by MAb E1f were quantitated by phosphorimaging and graphed as a percentage of the total E1 or E1^* immunoprecipitated by the polyclonal antibody. The data shown are representative of three experiments.