FIG 5.

Tetherin antagonism by Nef facilitates HIV-1 replication in cells expressing human tetherin. (A to E, G, and H) JTAg parental (A), JTAg L-tetherin (B), JTAg S-tetherin (C), and activated CD4⁺ T lymphocytes from two different donors (D, E, G, and H) were infected with HIV-1.Δvpu.IeG-Nef recombinants expressing the indicated Nef alleles, and virus replication was monitored by measuring the accumulation of p24 in cell culture supernatants by an antigen capture ELISA. For primary CD4⁺ T lymphocytes, the cultures were divided 48 h after infection and maintained in medium with (E and H) and without (D and G) 100 U/ml IFN-α. (F and I) Tetherin upregulation in response to IFN-α was verified by surface staining on day 3 postinfection. Histograms show the fluorescence intensity of staining with an antibody to tetherin (BST-2) compared to staining with an isotype control antibody (shaded). The data are representative of results from at least two independent experiments.