Mathematical model for change in diameter distribution of baculovirus-infected Sf-9 insect cells

Abstract

Sf-9 insect cells were examined for diameter before and after baculovirus infection. The diameter distribution of uninfected Sf-9 insect cells was described by the normal distribution function with a mean cell diameter and standard deviation of 18.5 ± 1.5 μm. After synchronous infection at a high MOI and high cell density, the infected cells grew in diameter almost linearly with time for about 48 h to have a steady mean diameter 1.45 times larger than that of uninfected cells, though still normally distributed. The distribution of the infected cells began to broaden at around 6 h-post-infection and eventually had standard deviation twice as large as that of uninfected cells. A mathematical model was developed to describe the change in the diameter distribution of virus-infected insect cells, integrating the distributions of infected cell subsets that were generated according to the Poisson distribution function between time t and t + d t and individually characterized with a post-infection time. The growth of uninfected cells and post-infection events such as progeny virus replication and secondary infection of uninfected remained cells were simulated according to a previous report. The model calculation predicts the change in diameter distribution of Sf-9 insect cells that were infected under various conditions, giving an indication to assess the degree of virus infection.