RetroPack-A was generated by stably expressing retroviral structural genes Gag-pol and env under EF1 promoter in 293T cells. These cells showed extremely efficient virus producing capability and can consistently generate high titer virus (>1x107 IFU/ml) for at least 30-40 passages. Amphotropic virus can infect most of proliferating mammalian cells including human cells. These cells have been used for reprogramming human fibroblasts into induced pluripotent stem cells (iPSCs). They are your ideal choice for high efficient retrovirus production.
Figure 1 | Infection of Human Keratinocytes by Retrovirus (Oct4 expression)