FIG. 1.

CpG ODN enhance antipolysaccharide antibody responses after immunization with 19F-CRM₁₉₇ conjugate vaccine. Groups of six mice were immunized on days 0 and 14 with 19F-CRM₁₉₇ (approximately 5 μg of polysaccharide equivalent) with or without 100 μg of CpG ODN 1826 or 100 μg of non-CpG ODN 1982 in saline. Serial dilutions of mouse sera obtained on day 28 were assayed by ELISA for anti-19F antibodies, the OD values for the dilutions were used to construct a curve for each mouse, and the anti-19F antibody titer was calculated for each mouse at an OD of 0.5, using two-point curve fit analysis (see Materials and Methods). The geometric mean titer is shown for each group of six mice (error bars indicate SEM); ∗ indicates P < 0.05 compared to immunization with 19F-CRM₁₉₇ alone. (A) Total anti-19F; (B) anti-19F IgG1; (C) anti-19F IgG2a; (D) anti-19F IgG3; (E) anti-19F IgM. In sera from unimmunized mice, the titers of total anti-19F and all isotypes of anti-19F were <1 (maximum OD < 0.5). These data are representative of three independent experiments of similar design plus three modified related experiments, all of which showed enhancement of anti-19F antibodies by CpG ODN.