Replication kinetics of parental MHV-GFP and recombinant MHV-GFP Clone 1 and Clone 2. L929 cells were infected at an MOI of 0.1. Cell culture supernatants were harvested at indicated time points post-infection and titrated by plaque assay. Data are representative of three independent experiments with two replicates per virus in each experiment. Error bars show standard deviation (SD) from the mean. pfu/ml, plaque forming units per millilitre. 