Limit of detection <i>in vitro</i>.

<p>(<b>A</b>) Images of two 96-well microtitre plates containing dilutions of <i>T.b. brucei</i> GVR35 clone VSL2 and a non-transformed control (WT). Each plate was imaged using an IVIS Lumina (Perkin Elmer) with 1 minute exposure and medium binning. Both cell lines were serially diluted from 1×10⁶ to 1×10³ (upper plate) and from 1×10³ to 1×10² parasites ml⁻¹ (cell numbers shown above each plate). 100 VSL2 parasites could be clearly visualised. Note that the imaging software automatically adjusts the heat-map scale to account for the intensity of the well containing the highest number of parasites. (<b>B</b>) <i>In vitro</i> linear regression plots generated from both plates. Each point corresponds to bioluminescence represented by the total flux recorded from a single well. In both cases, linear regression analysis shows a very strong positive correlation between bioluminescence and parasite number (R²>0.99). The graphs show readings from duplicate wells. In the upper graph, duplicate values were extremely close and are not individually distinguishable. In the lower graph, duplicates are shown as red squares and blue triangles, and the dotted line indicates the background in blank wells (green triangles), plus two standard deviations.