FIGURE 2.

A positive correlation between NTHi P5 expression and C4BP binding is observed for clinical isolates. Box plots showing binding of Alexa Flour 647–labeled C4BP (20 µg/ml) to different NTHI isolates (A) and P5 surface expression assessed using an anti-P5 mAb and an FITC-conjugated secondary Ab (B) as measured by flow cytometry. NTHi strains were isolated from the LRT of COPD patients (LRT, n = 16), invasive isolates from blood or cerebrospinal fluid (Blood/cerebrospinal fluid, n = 16), tonsil specimens from patients undergoing tonsillectomy (Tonsil, n = 15) or the URT (n = 16). Vertical dashed line indicates cutoff for P5 expression. Statistical significance was calculated using Kruskal–Wallis nonparametric ANOVA. The lower, mid, and upper hinges mark the first quartile, the median, and the third quartile, respectively. Whiskers extend from the hinges to the lowest and highest value within 1.5 times the interquartile range. Outliers are plotted as dots. H(3) = 21.862, p < 0.001 and H(3) = 40.147, p < 0.001 with multiple pairwise comparisons according to Dunn. (C) Spearman correlation analysis of Alexa Flour 647–labeled C4BP binding versus P5 expression in NTHi clinical isolates. Data represent two separate measurements of technical duplicates. r = 0.48, p < 0.001, n = 63.