FIG. 1.

(A) Constructs of NL4-3 chimeric envelope expression vectors. As a WT envelope expression vector, we used pME-NF-NL4-3env with a FLAG tag at the 5′ terminal end of the NL4-3 envelope gene. The V3 region of the NL4-3 envelope was replaced with a fragment of SDF-1 by using PvuII and NheI restriction sites. (B) Amino acid sequences of the V3 region of the NL4-3 envelope (NL4-3/V3) and human SDF-1. Homology between NL4-3/V3 and SDF-1 is indicated as follows: identical, asterisks; related, dots. Two different overlapping portions of SDF-1 used for chimeric envelope expression vectors are shown with three separate lines.