Figure 2. Resistance of the IM2 cell line maps to the MLV core.

(A) CHO-K1and IM2 cells were challenged with serial dilutions of the VSV-G pseudotyped MLV vector (MMP-nls-lacZ[VSV-G]), encoding β-galactosidase. The cells were then stained 48 hpi with X-gal, the number of blue cells were counted, and the data reported as the percentage of LacZ transducing units (LTU) obtained from WT CHO-K1 infections (5×10⁵ LTU). The data shown are the average of three experiments each performed with triplicate samples. Error bars indicate the standard deviation of the data. (B) CHO-K1 cells and IM2 cells, engineered to express TVA800, or wild-type CHO-K1 cells, were challenged with either pMMp-nls-LacZ[envA], an EnvA pseudotyped MLV vector encoding β-galactosidase, or with RCASBP(A)-AP, an ALSV-A vector encoding heat stable alkaline phosphatase. Infection was monitored using chemiluminescent assays to detect reporter enzyme activities along with a chemiluminescent assay to measure relative viable cell numbers. The ratios of [enzyme activities∶relative viable cell number] were calculated for each sample and compared with values from CHO-K1 TVA 800 cells (defined as 100% infection). The data shown are the average mean values obtained in an experiment performed with quadruplicate samples and are representative of three independent experiments. Error bars indicate the standard deviation of the data.