Multiscale modeling of influenza A virus replication in cell cultures predicts infection dynamics for highly different infection conditions

Influenza A viruses (IAV) are commonly used to infect animal cell cultures for research purposes and vaccine production. Their replication is influenced strongly by the multiplicity of infection (MOI), which ranges over several orders of magnitude depending on the respective application. So far, mathematical models of IAV replication have paid little attention to the impact of the MOI on infection dynamics and virus yields. To address this issue, we extended an existing model of IAV replication in adherent MDCK cells with kinetics that explicitly consider the time point of cell infection. This modification does not only enable the fitting of high MOI measurements, but also the successful prediction of viral release dynamics of low MOI experiments using the same set of parameters. Furthermore, this model allows the investigation of defective interfering particle (DIP) propagation in different MOI regimes. The key difference between high and low MOI conditions is the percentage of infectious virions among the total virus particle release. Simulation studies show that DIP interference at a high MOI is determined exclusively by the DIP content of the seed virus while, in low MOI conditions, it is predominantly controlled by the de novo generation of DIPs. Overall, the extended model provides an ideal framework for the prediction and optimization of cell culture-derived IAV manufacturing and the production of DIPs for therapeutic use.Author summary: Influenza is a contagious respiratory disease that severely affects several million people each year. Vaccination can provide protection against the infection, but vaccine composition has to be adjusted regularly to remain effective against this fast evolving pathogen. While influenza vaccines are mostly produced in embryonated chicken eggs, cell culture-based vaccine production is developing as an alternative providing controlled process conditions in closed systems, better scalability, and a short response time in case of pandemic outbreaks. Here, we employ a computational model to describe underlying mechanisms during the IAV infection in adherent MDCK cells. Special attention was paid on the influence of the MOI on virus spread in cell populations. Although dynamics between infections with high and low amounts of infecting virions differ significantly, our model closely captures both scenarios. Furthermore, our results provide insights into IAV-induced apoptosis and the switch from transcription to replication in intracellular IAV replication. Additionally, model simulations indicate how virus particle release is regulated, and what impact defective interfering particles have on virus replication in different infection conditions. Taken together, we developed a computational model that enables detailed analyses of IAV replication dynamics in animal cell culture.