FIG. 3.

Comparison of the strict threshold assumption of the basic model to the soft threshold assumption. (A) The infectivity of a virion as a function of the number of functional trimers on its surface according to the strict threshold assumption. In this example, we assume that T = 8, i.e., that a virion with eight or more trimers is fully infectious, whereas a virion with fewer than eight trimers is not infectious. (B) The infectivity of a virion as a function of the number of functional trimers on its surface according to the soft threshold model. Two curves with differing Hill coefficients, h, are shown.