Transduction efficiency was estimated 4 days after transduction at indicated MOIs. (a) GFP expression was observed under light microscopy (top) or fluorescence microscopy (bottom). (A) MOI of 5 (×100). (B) MOI of 20 (×100). DCs saw an increase in expression of GFP that peaked when . (b) The efficiency of infection was determined by assaying GFP expression by flow cytometry (green line) and comparing with uninfected control cells (grey peak).