FIG. 3.

Macrophage-tropic envelopes require less CD4 for infection. HeLa cell clones expressing different CD4 and CCR5 levels (29) were infected with Env⁺ pseudoviruses as described in Materials and Methods. After 72 h, cells were fixed and immunostained for p24 antigen, and foci of infection were counted. Infectivities for Env⁺ pseudotypes prepared with envelopes amplified from adult blood and semen (A) and pediatric plasma (B) are shown. Envelopes that conferred infection of macrophages (SQ43 380.1, C98-15, C98-18, J92-14, and S94-CSF-11) also conferred infection of HeLa cells expressing low levels of CD4. (C) Infectivities of an extended panel of brain and lymph node envelopes that were previously reported (27) are shown for comparison. Envelopes from pediatric patients P-1206, P-1114, and P-1031 are designated by the letters S, C, and J, respectively.