FIG 2 .

In vitro opsonophagocytic killing (OPK), bactericidal activity, and Shiga toxin neutralizing activity of the antibodies induced by PNAG-based conjugate vaccines. (A and B) Opsonophagocytic killing (with HL-60 cells) of the STEC strains indicated on the x axis by antibody in sera raised to 9GlcNH₂-TT (A) or 9GlcNH₂-Stx1b (B). (C and D) Bactericidal killing (without HL-60 cells) of the STEC strains indicated on the x axis by antibody in sera raised to 9GlcNH₂-TT (C) or 9GlcNH₂-Stx1b (D). There was no killing in the absence of complement in any assay (small bar to the left of each 1:10 serum dilution bar). Bars represent means of three replicate samples within an assay. (E and F) Normal rabbit serum (NRS), antibody to the 9GlcNH₂-Stx1b conjugate vaccine, MAb to Stx1, or polyclonal antibody to Stx2 was diluted as indicated on the x axis and mixed with an amount of either Stx1 or Stx2 predetermined to give ~50% killing (dashed lines) of the Vero cells in 96-well culture plates. The control for Stx1 neutralization was a MAb initially used at 200 ng/ml. The bars represent the calculated mean cell viabilities from six duplicate wells, and the graphs depict a typical experiment representative of 3 repeat assays.