Figure 4: Fitness tradeoffs model for the evolution of IFN suppression.

(a) Conceptual scheme of the model. Host cells are pictured in brown, and the IFN-suppressing and non-suppressing variants in red and blue, respectively. Released viral progeny is represented with dots inside triangles. During early steps of the infection, the virus spreads rapidly in the absence of IFN, and a fast-growing variant has a relative fitness of 1 + α_F. During late infection, viral spread is partially inhibited by IFN-mediated antiviral responses, and hence IFN suppressors have a relative fitness of 1 + α_S. In cells co-infected with fast growers and suppressors, relative fitness differences are offset because viral products are provided in trans. (b) Numerical solution of the model for three different MOIs and a range of α_F and α_F beneficial selection coefficients. Alternated first and second cycles were simulated until a stable equilibrium was reached or one of the two variants became fixed. Colors indicate the final population frequency of the suppressor variant. Q_S < 0.0001 (purple) indicates loss of the IFN suppressing virus, and Q_S = 1 (red) indicates fixation.