Figure 2. MoMLV infection of inGluc-MLV-DERSE cells produces Gluc activity in the culture supernatant.

(a) inGluc-MLV-DERSE cells can detect RCR produced by a chronically infected cell-line. inGluc-MLV-DERSE cells were co-cultured with NIH-3T3 cells that were chronically infected with MoMLV. Three days after the co-culture was initiated, 10µL of culture supernatant was assayed for Gluc activity. Cultures and co-cultures were conducted in triplicate. Columns represent the mean of 3 cultures (standard error of mean error bars are present, but not visible at this scale). (b) Gluc activity in the cell culture supernatant accumulates over time and its level is directly related to the amount of virus used for infection. 96-well plates containing 1.25 × 10³ inGluc-MLV-DERSE cells per well were infected with 0.03 ml of serial dilutions of MoMLV; Gluc activity in the supernatant was measured at 4 (circles), 5 (squares) and 6 (triangles) days post infection. The dashed line represents the average counts per second in supernatant from the mock-infected cultures. Points represent the mean of 3 infections (standard error of mean error bars are present, but not visible at this scale). The 10⁻¹ dilution of the inoculum contained 1.5 × 10³ focus-inducing units per 0.03 ml.¹⁰ (c) Gluc activity assay can be conducted directly in the cell-culture plate. inGluc-MLV-DERSE cells were infected with MoMLV and 3 days after infection Gluc substrate was added directly to the culture wells and Gluc activity measured. Columns represent the mean of 3 infections, error bars represent the standard error of mean.