Figure 2.

Disease progression in patients with different average avidities of their HIV-specific T cell repertoire. Parameters values: σ=2 cells mm⁻³ d⁻¹, δ_T=0.05 d⁻¹, σ_H=10⁻⁵ cells mm⁻³ d⁻¹, α=0.4 d⁻¹, β=0.04 cells⁻¹ mm³ d⁻¹, ϵ=0.1 cells⁻¹ mm³ d⁻¹, δ_H=0.01 d⁻¹, δ_I=0.2 d⁻¹, γ=1 cell mm⁻³, k=0.3 cells⁻¹ mm³ d⁻¹; the probability of escape mutations arising per day in a given epitope is p_ESC=infected cells/35. Values for the parameters and variables are based on a ‘total body model’, and rescaled to a volume of 1 mm³. q_i is dimensionless; γ/q_i represents the number of cells mm⁻³ required for half-maximal proliferation. p.i, post infection. Colour coding: target cells, black; infected cells, red; total helper cells, light green; number of clones responding, purple; average avidity immune response, orange; avidity of the best clone, blue. AIDS corresponds to the state without immune response, with high-viral load (more than 8 cells mm⁻³) and low target cell numbers. (a) Low repertoire avidity, q_avg=0.5. Fast progressor: AIDS occurs after about 3.5 years. (b) Medium repertoire avidity, q_avg=1.0. Intermediate progressor: onset of AIDS at about 12 years. (c) High-repertoire avidity, q_avg=1.5. Slow progressor: AIDS after more than 17 years. (d) Primary infection phase (first 250 days) of the individual shown in figure 2b.