A: increasing concentrations of purified rIsdA were exposed to BSA (closed symbols) or human fibrinogen (open symbols) -coated wells and detected using the p-nitrophenyl phosphate system from Sigma. B: Serum titre ELISA using rIsdA (open symbols) and BSA (closed symbols) -coated wells exposed to two-fold serial dilutions of rabbit pre-immune serum (diamond symbols), rIsdA post-immune serum (square symbols), and an IgG purified fraction of post-immune serum (triangle symbols). All assays were performed in triplicate and values represent the mean absorbance at 405 nm (A405) with the standard error (error bars are shown in black on all graphs, but are difficult to see in some cases on account of the errors being small). Image C shows specific rIsdA detection by western immunoblotting using rIsdA post-immune serum and the purified IgG fraction (IgG) compared to the rabbit pre-immune serum (Pre). M represents the SDS PAGE (low range) molecular weight marker from BioRad.
