<p>Low doses of the relatively neutralization resistant SHIV <sub>SF162P3</sub> isolate were incubated at 37<sup>0</sup>C for four hours with concentrations of the human monoclonal antibody IgG1 b12. The mixture was then added to GHOST cells and allowed to absorb for 24 hours. The cells were washed and cultured for a further 24 hours (4/24/2 assays). Four duplicate cultures were used for each point within a replicate. Data are fitted to a second-order (quadratic) equation. Dotted lines are extrapolations to the horizontal axis calculated from the quadratic plots. Axes are truncated and some symbols are excluded to improve clarity, especially around the origin. <b>A</b>. SHIV<sub>SF162P3</sub> exposed to GHOST cells from passage 7 (1 replicate) and 9 (2 replicates). Gray: control cultures where virus were incubated without monoclonal antibody: y = -0.00285 x<sup>2</sup> + 1.310 x -6.009; green: Virus pre-incubated with 0.625 µg/ml IgG1 b12: y = -0.00284 x<sup>2</sup> + 0.939 x -0.517. <b>B</b>. Gray same as for A. blue: Virus pre-incubated with 0.25 µg/ml IgG1 b12: y = -0.000606 x<sup>2</sup> + 0.870 x + 3.152. <b>C</b>. SHIV<sub>SF162P3</sub> exposed to GHOST cells from passages 15, 17 and 21. Gray: control cultures where virus were incubated without monoclonal antibody: y = 0.00182 x<sup>2</sup> + 0.665 x + 11.01; green: Virus pre-incubated with 0.625 µg/ml IgG1 b12: y = + 0.00135 x<sup>2</sup> + 0.487 x + 8.334. <b>D</b>. Gray same as for C. blue: where cultures are exposed to virus pre-incubated with 0.25 µg/ml IgG1 b12: y = 0.00140x<sup>2</sup> + 0.616x + 5.768. Interval between points where control and 0.25 µg/ml IgG1 b12 plots cut x-axis: 7.81 infectious virus.</p
