FIG. 1.

Strategy to construct chimeric envelope gp120 regions. The organization of gp120 with hypervariable domains V1, V2, V3, V4, and V5 (white boxes) and conserved regions (black boxes) is shown with the restriction endonuclease sites used for construction of chimeric envelopes. Abbreviations: K, KpnI; B, BstAPI; S, StuI; Bu, Bsu36I; M, MfeI; P*, PstI site introduced by mutagenesis without changing the amino acid sequence. Bars below the gp120 diagram indicate the actual regions evaluated in the chimeric constructs: V1 includes C1; V3 includes C2 and part of C3; V4 includes part of C3 and C4; V5 includes part of C4.