FIG. 7.
sCD4 preferentially inhibits infection by X4-tropic HIV-1. X4- and R5-tropic viral isolates (A) and V3 loop mutants (B) were produced in 293T cells. Virions were treated with the indicated concentrations of sCD4 and assayed for infection on P4/CCR5+ reporter cells as described in Materials and Methods. Values are expressed as a percentage of the infectivity of the corresponding untreated virus. Shown is a representative of up to three experiments. Filled symbols, X4-tropic HIV-1; open symbols, R5-tropic HIV-1.