Inhibition of cell-cell spread assayed by quantitative real-time PCR. HIV-1 (NL4.3) infected Jurkat cells were either left untreated (control) or incubated with 10 or 100 μg/ml of the indicated antibodies for 1 h at 37°C prior to mixing with uninfected Jurkat 1G5 target T cells. DNA was extracted at 0, 3, 6 and 12 h and quantitative real-time PCR was performed to measure the appearance HIV-1 pol DNA resulting from de novo reverse transcription in newly-infected target cells. Data were normalised to the albumin housekeeping gene and expressed as the fold increase in HIV-1 DNA copy number over time relative to the baseline value at t = 0 h. Value of greater than 1 indicates an increase in HIV-1 DNA. Data are the mean with SD from a representative of 2 independent experiments. Statistical analysis was performed using by Anova with Tukey's post-test to compare each antibody to the control (untreated) at corresponding time points (t = 3 h, t = 6 h and t = 12 h). Values for J3, b12 VRC01, and HJ16 were significantly different from untreated controls at 6 h and 12 h at both antibody concentrations (p < 0.001). 4E10 was significantly different from untreated controls at 6 h and 12 h only when used at 100 μg/ml (p < 0.001).