FIG 9.

Single substitutions in the HIV-1 envelope can substantially alter susceptibility to the late IFN-γ-induced block in MT4 cells. (A) MT4 cells with and without pretreatment with 1,000 U/ml of IFN-γ were infected at an MOI of ∼0.001 with HIV-1 (NHG). The percentage of GFP-positive cells over time is shown (determined using flow cytometry). HIV-1 propagated in the presence of IFN-γ was used to inoculate fresh MT4 cells (at the times indicated with arrows) with or without IFN-γ pretreatment. (B and C) Sanger sequencing chromatograms from PCR-amplified proviral DNA from the parental clone or the P5 swarm from vif or env are shown (single nucleotide polymorphisms are highlighted with arrows). (D) Replication of the T192M mutant and the parental clone was measured as described in panel A. (E) An amino acid alignment of the V2 region of gp120 of the four most IFN-γ-sensitive and -resistant strains from the experiment shown in Fig. 5, along with two pathogenic SHIVs (SF162P3 and KU-1) and the corresponding HIV-1 envelope sequence (SF162 and HXB2, respectively). T192 (NHG) is indicated with an arrow and colored shading.