ViPS-specific IgM and IgG Measurement

ViPS-specific IgM and IgG were measured by coating 96-well microtiter plates (Nunc MaxiSorp™; Invitrogen, Carlsbad, CA) with 2 µg/ml of ViPS purified from S. Typhi clinical isolate C6524^{64 (link)} in DPBS overnight at room temperature. All plates were washed and blocked with 2% Bovine serum albumin (BSA) in PBS pH 7.2 (blocking buffer) for 2 h at room temperature. Blood from immunized mice was diluted to 1:25 for IgG detection and 1:50 for IgM detection in blocking buffer; ViPS-specific mouse IgM and IgG levels were interpreted as ng/μl “equivalents” using normal mouse serum standards (Bethyl Laboratories, Montgomery, TX), as described previously^{35 (link)}.