Replication of reverse-engineered and knockout (KO) viruses in RL-5 T lymphocytes. (A) Growth curves of Ur, SLS, Lu, and Ur with M005L/R knocked out or replaced with M005L/R from Ur, SLS, or Lu at an MOI of 0.05. (B) Single-step growth curves of Ur with M005L/R knocked out or replaced with M005L/R from Ur, SLS, or Lu at an MOI of 5 in RL-5 cells. (C) Growth curves of SWH 8/2/93 with M156R knocked out or replaced with M156R from SWH 8/2/93 or WS6/1071 at an MOI of 0.05. Each growth analysis was performed in triplicate, and the geometric means for each time point are shown.