FIG 2.

LVS-V induce robust antibody responses where IgM is essentially all anti-LPS antibody and IgG is predominantly directed against non-LPS epitopes. (A) Schematic of immunization and bleeding schedule. The mice were immunized and challenged as described in Fig. 1. The mice were challenged again 22 days following the primary challenge to determine the effect on antibody responses. (B) ELISA data measuring F. tularensis-specific IgM. (C) ELISA data measuring F. tularensis-specific IgG (all subclasses). Microwell plates were coated with purified F. tularensis LVS LPS (top panels) or whole F. tularensis LVS bacteria (bottom panels) to distinguish between LPS-specific and overall anti-F. tularensis antibody levels. The titers are shown on a log scale. Each symbol represents one mouse. ND, none detected. (D) The geometric means of the ELISA titers detected in B and C were replotted for easier visual comparison between the antibody levels directed against whole F. tularensis LVS (filled symbols, solid lines) and those against purified F. tularensis LVS LPS (open symbols, dashed lines) in both IgG (■, black) and IgM (▲, gray) assays. **, P < 0.01; ***, P < 0.001.