FIG. 1.

Analyses of phages selected with strain 89.6 Env pseudotyped virus particles preincubated with sCD4. (A) ELISAs showing the reactivity of selected phages (phages a to i) and the wild-type (WT) control phage with 89.6 Env-expressing Fly cells without sCD4 preincubation (black bars) and with sCD4 preincubation (gray bars), as well as with Fly control cells (white bars; no Env expression, sCD4 preincubation). OD, optical density. (B) Sequences of the peptide inserts of the selected phages. Phage a was selected 12 times, and phage e was selected twice. (C) Some peptide inserts (a, b, g, h) show sequence identity with amino acids of the N terminus and motifs in the extracellular domains of the CCR5 receptor marked with arrows. Motifs in boldface type have previously been identified to be implicated in gp120 binding and virus entry. The 3A9/5C7 mimotope corresponds to a composed epitope for 3A9 and 5C7 antibodies against CCR5 identified by us previously to be important for HIV-1 entry (21). The YD-rich motifs are also found at the N terminus of CXCR4.