FIGURE 5.

HIV-1_NL4-3 Env-mediated cell fusion and entry. A, HIV-1_NL4-3 Env-mediated cell-cell fusion activity. B, infectivity of HIV-1_NL4-3 pseudoviruses on TZM-b1 cells. C, the effect of substitutions of M-T hook residues on HIV-1_NL4-3 Env-mediated cell fusion and infection. Both cell fusion and single-cycle infection assays were performed at least three times and the data are presented as mean ± S.D. The control is cell-derived background in the absence of HIV-1 Env (fusion) or pseudoviruses (entry).