FIG. 2.

Growth curves of reverted viruses in CEMx174 cells. The second set of compensatory mutations, located in the DIS, i.e., A423G, and the NC region, i.e., E18Q and Q31K, were introduced, either alone (A) or combined (B), into the SD2 construct. The resultant constructs were transfected into COS-7 cells. Equivalent amounts of virus thereby recovered were used to infect C8166 cells based on levels of p27 antigen (10 ng/10⁶ cells). Viral replication was monitored by reverse transcriptase (RT) assay of culture fluids. Mock infection denotes exposure of cells to heat-inactivated wild-type (WT) virus as a negative control.