FIG. 2.

Competitive inhibition of salivary gp340-mediated streptococcal aggregation by antigen I/II peptides AR-A (A), AR-B (B), and AR-P (C). The AR-A and AR-B peptides were incubated at 37°C with S. gordonii M5 cells in the presence of 30 μg of gp340 per ml in a 1-ml volume. The AR-P peptide was similarly incubated with S. mutans KPSK2 (Fig. 2C). gp340-mediated bacterial aggregation was followed by monitoring the decrease in OD₆₇₅ as cell aggregates formed and settled. Incubations were carried out in the presence of 10 (♦), 25 (▴), 50 (▪), or 90 μg (▾) of each peptide per ml or in the presence of 30 μg of full-length SspB per ml (•). Positive control reactions (○) consisted of bacteria and gp340 in the absence of AR peptide. Nonspecific settling of cells was monitored in blank reactions containing only bacteria and was ≤0.05 OD₆₇₅ units for all reactions. All reactions were carried out in triplicate.