FIG. 5.

Estimation of anti-Vi IgG μg/ml. (A) A human immunoglobulin isotyping kit (catalog no. 48-302; Millipore, Billerica, MA) was performed according to manufacturer's instructions except that the anti-human IgG-rPE detection reagent utilized in the Vi bead assay was used as the detection reagent. (B) MFI values for the anti-Vi IgG standard curves that were within range of the total IgG standard curve were used to estimate the median IgG concentration of the Vi-specific IgG in the standard. This was used to plot anti-Vi IgG EU/ml versus anti-Vi IgG ng/ml to estimate protective levels of anti-Vi IgG (i.e., 1 μg/ml).