FIG 2.

Cross-reactivity of peptides with heterologous sera. (A) The probability of reactivity of a peptide with heterologous sera raised against the other chlamydial species/strains is shown in dependence on the percent sequence identity of the peptide to the respective heterologous chlamydial peptide. Peptides that produced with the heterologous sera >5% of the signal of homologous sera were designated as cross-reactive. The probability of cross-reactivity analyzed by logistic regression (n = 700, P < 10⁻⁶) is shown on the left ordinate; the number of peptides analyzed for each 10% bracket, visualized by bars, is shown on the right ordinate. Cross-reactive peptides are found exclusively at a 50% or higher sequence identity. (B) Signal strength of cross-reactive peptides relative to the signal of the homologous peptides in dependence of sequence identity. In linear regression analysis, the signal strength is independent of the degree of sequence identity (n = 49, r² = 0.01, P = 0.5).