Figure 3. Secondary challenge experiments using the basic and extended models.

Re-exposure was modeled by an instantaneous inflow of EBs at each of the above-described times using a multiple of the initial infectious dose, 10×E(0) for both the basic model (A), and the extended model (B). In both panels, second infection is decreased in severity because of some residual population of T cells (A) or both T cells and antibody (B). The magnitude and time evolution of the system of equations in both (A) and (B) have been rescaled (i.e., are presented non-dimensionally) so to allow for a visual comparison. Because of structural differences, the reference categories used for scaling were different between basic and extended models. Black arrow indicates time point of secondary exposure and CD4+ T cells and antibody are plotted on the right axis.