Figure 3
Increased binding activity of FeLV-945 SU is observed over a 100-fold range of SU concentration. A. - E. FeLV-945 SU or FeLV-A/61E SU proteins in equivalent mass amounts over a 100-fold range (0.1X - 10X) were incubated with feline 3201 cells and processed for flow cytometric binding assays as described in Figure 2. Representative histograms are shown, demonstrating the binding activity of FeLV-A/61E SU (gray shaded) or FeLV-945 SU (black shaded). Negative controls (open histograms) included supernatants from mock-transfected cells (solid line), FeLV-A/61E SU with isotype control antibody (dotted line), and FeLV-945 SU with isotype control antibody (dashed line). Indicated at each SU concentration is the result of statistical analysis of replicate binding assays using four independently generated and infrared-quantified batches of SU proteins. A statistically significant increase in geometric mean fluorescence for FeLV-945 SU binding was considered p < 0.05. F. Relative dissociation constants (Kd) were determined from the data shown in A - E by nonlinear regression analysis using saturation binding equations with an assumption of one site-specific binding (GraphPad Prism5.0).