Post-mitotic, differentiated myotubes efficiently produce retroviral vector from hybrid adeno-retrovirus templates

We have examined the ability of proliferating myoblasts and post-mitotic, differentiated myotubes to produce retroviral vector using hybrid adeno-retroviral vectors as templates. We show that production of retroviral vector from myoblasts peaks 48 h after adenoviral infection at 4.8 x 10(4) cfu/ml and is scarcely detectable by 96 h. Both fully and partially differentiated myotubes were able to generate a sustained increase in the levels of retroviral vector compared with myoblasts peaking 48 h at 1.4 x 10(5) cfu/ml and 1.8 x 10(5) cfu/ml, respectively. Addition of the cell cycle inhibitor aphidicolin (5 microg/ml) had no effect on the production of retroviral vector from fully differentiated myotubes, but resulted in an 80% increase in vector production from partially differentiated myotubes. Thus indicating that retroviral vector production is more efficient in post-mitotic myotubes and is independent of muscle cell cycle progression.