Fig. 5.

Genetic characteristics of phenotypically confirmed X4 sequences and structural modeling for coreceptor binding. (A) V3 amino acid alignment of SGA-derived sequences from the phenotype-confirmed primary viral isolates. Sequences shown in red and blue are phenotypically confirmed X4 and R5 sequences, respectively. Key V3 positions associated with the X4-using phenotype are shaded in light blue. (B) Structural modeling for V3 positions 7, 8, and 25 in binding of coreceptors CCR5 and CXCR4 using the V3-docking model.