FIG 4.

The conformational state induced by CD4Ms demonstrates isolate-specific stabilities. (A and B) Effects of sCD4 and JRC-II-191 on structure and function of Env. HOS cells expressing the indicated Envs were incubated for 1 h at 37°C with MAb 17b in the presence of JRC-II-191 or sCD4 (Bottom). Changes in 17b binding relative to samples not containing CD4Ms (Top). In addition, viruses containing these Envs were incubated with cells in the absence or presence of sCD4 or JRC-II-191 for 6 h. The cells were then washed and further incubated to measure the residual infectivity of CD4M-treated virus relative to untreated virus. (C) Relationship between binding of MAb 17b to Envs in the absence and presence of JRC-II-191. The lines are color coded according to the sensitivity of each Env to inactivation by JRC-II-191 (red, resistant; green, sensitive). (D) Reversibility of structural changes induced by CD4Ms. HOS cells expressing 89.6 Env were incubated with MAb 17b and JRC-II-191 or sCD4. Alternatively, some samples were first incubated with the CD4M, which was then removed and MAb 17b was added. The data represent changes in binding of MAb 17b relative to samples incubated without CD4Ms. (E) Effect of JRC-II-191 on infection of CD4⁻ CCR5⁺ cells. Viruses containing the indicated Envs were spinoculated onto cells at 10°C and then incubated for 2 h at 37°C in the absence or presence of JRC-II-191. The cells were then washed, and infectivity was measured 3 days later. The dashed lines represent infectivity measured in the same experiment by untreated virus bound to CD4⁺ CCR5⁺ cells. (F) Effect of JRC-II-191 on neutralization by PS and MAb 17b. Viruses containing the indicated Envs were added to cells in the presence of JRC-II-191 (4 μM), PS, or both for 6 h at 37°C. The cells were then washed and further incubated to measure residual infectivity. The blue triangles represent the calculated synergistic effects between JRC-II-191 and PS or MAb 17b. (G) Synergy between the effects of cold and JRC-II-191. Viruses were exposed to 0°C, JRC-II-191 (4 μM), or both for 2 h and then added to cells to measure residual infectivity. The values in the x axis represent the calculated products of the inhibitory effects of each treatment separately. The values in the y axis describe the measured effect on infectivity of virus exposed to both treatments simultaneously.