Complementation and epistasis in viral coinfection dynamics

Coinfection in RNA virus populations results in two important phenomena, complementation and recombination. Of the two, complementation has a strong effect on selection against deleterious mutations, as has been confirmed in earlier studies. As complementation delays the purging of less-fit mutations, coinfection may be detrimental to the evolution of a virus population. Here we employ both deterministic modeling and stochastic simulation to explore the mechanisms underlying the interactions between complementation and other evolutionary factors, namely, mutation, selection, and epistasis. We find that strong complementation reduces slightly the overall fitness of a virus population but substantially enhances its diversity and robustness, especially when interacting with selection and epistasis.