FIG. 6.

Relationship between CD4 independence and neutralization sensitivity. Fusion assays with the indicated Env proteins were performed in the presence of a 1:100 dilution of either normal human serum or HIV-positive human serum. The efficiency with which each Env mediated CD4-independent membrane fusion (derived from Fig. 2 to 4) is shown for convenience. Chimeras containing the indicated 8x domains and the V3 region point mutations described in Fig. 3 are shown in panel A, while the V4 point mutations described in Fig. 4 are shown in panel B.