Susceptibility of P^k-liposome–fused Jurkat T cells to X4 HIV-1 infection. Jurkat T cells lacking P^k were incubated with P^k- or P-liposomes and cultured for 18 hours, where PBS or PL-liposome controls were used. Tricolor FACS analysis was performed and scatter plots of Jurkat labeled with anti–CD4 PerCP Cy5.5, anti-CXCR4-PE, and anti–P^k GAM-FITC (or GAM-APC) were analyzed, where background was compensated to isotype controls. (A) Histogram representing percentage of cell populations expressing P^k. (B) Scatter plots representing cell populations expressing P^k and CXCR4, and gated on CD4-positive populations. (Left) PBS-treated Jurkat. (Center) PL-liposome–fused Jurkat. (Right) P^k-liposome–fused Jurkat. (C) Scatter plots representing percentage of cell populations expressing CD4 and CXCR4. (Left) PBS-treated Jurkat. (Center) PL-liposome–fused Jurkat. (Right) P^k-liposome–fused Jurkat. (D) Surface expression levels of CD4, CXCR4, and P^k are represented as MFI. (E) TLC of total GSLs extracted from control and liposome fused Jurkat cells. Lane 1: GSL standards. Lane 2: P^k-expressing B-cell line control (Daudi). Lane 3: PBS-treated Jurkat control. Lane 4: PL-liposome control. Lane 5: P^k-liposome–fused Jurkat. (F) Infection with HIV-1_IIIB (MOI, 0.3) and p24^gag monitored at day 3 after infection (n = 3 or 4 infection data points). Percentage difference in infection was calculated based on PBS control infection levels, and data were pooled from 3 independent experiments to show significance between PL-liposome controls and P^k-liposomes (*P < .05, **P < .002). PBS indicates PBS control; PL or PL-Lp, phospholipid liposome control; P^k or P^k-Lp, P^k liposomes; P, P-liposomes.