<i>VSG</i> Switching Hierarchy in T. brucei

<p>The graph is adapted from [<a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0060185#pbio-0060185-b009" target="_blank">9</a>] and shows the numbers of T. brucei cells (parasitaemia) measured in a cow for up to 70 days post-infection (this measurement is depicted by inversely plotting the prepatent period, in days, that a 0.2-ml inoculum of cattle blood achieves a parasitaemia of 1 × 10^8.1 trypanosomes ml⁻¹ units in an immunosuppressed mouse). Below the graph is a depiction of <i>VSG</i> gene activation timing (see <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0060185#pbio-0060185-g002" target="_blank">Figure 2</a> for details of the switch mechanisms). During <i>VSG</i> switches driven by recombination, silent <i>VSG</i>s at a telomere are, in general, activated more frequently that subtelomeric array <i>VSG</i>s, which are activated more frequently than <i>VSG</i> pseudogenes (pseudo). It is unclear (indicated by a question mark) if transcriptional switches between <i>VSG</i> bloodstream expression sites (BES) occur predominantly at the start of an infection or continue throughout.