FIG 4.
Effects of LP-52-selected mutations on the functionality of SIV Env. (A) Infectivity of the wild-type (WT) and mutant SIVmac239 pseudoviruses in TZM-bl cells. The viral particles were normalized to a fixed amount by p24 antigen and their relative infectivity was determined by a single-cycle infection assay. The luciferase activity of WT SIVmac239 was treated as 100%, and the relative activities of other mutant viruses were calculated accordingly. (B) Relative cell-cell fusion activity of WT and mutant SIVmac239 Envs determined by a dual split-protein (DSP) assay. HEK293T cells expressing viral Env and DSP1-7 were used as effector cells and 293FT cells expressing CXCR4/CCR5 and DSP8-11 were used as target cells. Similarly, the luciferase activity of WT Env was treated as 100%, and the relative fusion activities of other mutant Envs were calculated accordingly. The data were derived from the results of three independent experiments and are expressed as means and standard deviations (SD). Statistical comparisons were conducted by ANOVA (**, P < 0.01; ***, P < 0.001). (C) The expression and processing of SIVmac239 Envs determined by Western blotting. The viral glycoproteins in the lysates of transfected cells were detected with a monkey anti-SIV serum. The bands corresponding to gp160, gp120, and gp41 are respectively marked. The experiments were repeated two times, and representative data are shown.