Variables and parameters of our model.

aQ0 and S0 are chosen to maintain a stable density of CD4+ T cells (N0 = 725 cell/μl) in the absence of an infection; b Production from sources including thymus; c Beyond this threshold CD4+ T cell proliferation stops; d The average number of effective contacts between two CD4+ T cells. Cells contact each other frequently, but only a proportion (20–25%) of these random contacts are sufficiently stable and “effective” for a synapse to be formed at rate θ; e The average probability to form a virological synapse when two cells have an effective contact; f The average probability that a susceptible cell is infected when it forms a synapse with an infected cell; g Between the initial infection and the onset of cellular immune response, including the period before symptoms begin; hκ = 0 when t < D. Variables and parameters of our model.