FIG. 5.

Env trans-complementation assay of mutant Env proteins. Env pseudotypes produced from 293T cells cotransfected with pHXB2ΔBglCAT and each of the ΔKS (control), WT, or mutant Env plasmids were normalized for RT activity before being used to challenge CEM-SS cells. CAT activity was measured 3 days after virus infection. A representative result is shown in panel A. The background CAT level detected in the defective virus produced from ΔKS pSVE7puro cotransfection was subtracted from the CAT activity of the WT or mutant pseudotypes. The relative viral entry ability mediated by mutant proteins is expressed as a percentage of that mediated by the WT Env. The results from three independent experiments are shown as the mean ± standard deviation in panel B.