Figure 2.

Preexposure of P4-R5 MAGI cells to select polyanionic compounds results in enhancement of R5 HIV-1 infection. P4-R5 MAGI cells were incubated for 1 h with (A) IC₅₀ or (B) IC₉₀ (the concentrations at which 50% or 90% virus inhibition is achieved, respectively) dextran sulfate (DS), cellulose sulfate (CS), or λ-carrageenan (LC). Following exposure, cells were washed thoroughly and either challenged immediately with HIV-1 strain BaL for 1 h or supplemented with new medium for up to 6 h before infection with HIV-1 BaL (as described in Materials and Methods). Infectivity remaining is expressed relative to mock-treated, HIV-1-infected cells. To assess possible changes in cell viability associated with compound washout, P4-R5 MAGI cells were incubated for 1 h with (C) IC₅₀ and (D) IC₉₀ concentrations of DS, CS, or LC. The IC₅₀ and IC₉₀ for BaL inhibition were used because these concentrations were, with one exception, higher than the IIIB IC₅₀ and IC₉₀ (Table 1). Cells were subsequently assessed for viability as described in Materials and Methods. Viability is expressed relative to mock-treated cells. Data for this experiment are shown as mean values and calculated standard deviations from two independent assays in which each concentration was examined in triplicate. Error bars represent standard deviations. **p ≤ 0.01, *** p ≤ 0.001.