FIGURE 3.

Anti-CptA ELISA values correlate with toxin-neutralizing activity. Recombinant purified CptA24-1349 was pretreated with PBS alone (positive hemolysis control) or a vaginal swab sample and then added to washed RBCs. After 2 h at 37°C, released hemoglobin was measured by OD at 450 nm. The negative control (no CptA24-1349) value was subtracted from all test values, and the percentage of hemolysis relative to the positive control was calculated by setting untreated CptA24-1349 as 100%. All hemolysis assays were performed in duplicate, and averages of the two values are shown. Scatterplots showing percentage hemolysis (x-axis) relative to isotype-specific anti-CptA ELISA data (y-axis). Distinct markers were used for group 1 (preterm birth [PTB], low S. vaginalis), group 2 (PTB, high S. vaginalis), group 3 (term birth [TB], low S. vaginalis), and group 4 (TB, high S. vaginalis).