Optimisation of coating concentration and serum dilution in an MBP-IA-2 fusion protein ELISA. A. Incubation of ELISA plates with between 0.06 and 16 μg/mL with MPB-IA-2 fusion protein resulted in saturation at 6 μg/mL as determined using an anti-MBP monoclonal antibody. B. Subsequently, fusion protein coated ELISA plates were incubated with serum from 2 healthy individuals diluted at 1:10 (solid line - circle), 1:20 (dashed line - square), 1:50 (dotted line - triangle) and 1:100 (dotted/dashed line - inverted triangle). Background binding was highest at a coating concentration of 6 μg/mL, followed by 4 μg/mL. At most coating concentrations, serum dilutions of 1:10 produced the highest background and 1:100 the lowest. To achieve maximum assay sensitivity and acceptable background serum binding, a coating concentration of 4 μg/mL with serum dilution of 1:20 was selected for all subsequent fusion proten ELISAs. Data points represent the mean of individual experimental conditions. All experimental conditions were performed in triplicate.