Duration of pH 2.5 exposure differentially affects ELISA signals in sera from unvaccinated nonTg mice compared to vaccinated nonTg mice. Sera were collected from unvaccinated mice (3A) and mice vaccinated with human Aβ1–42 peptide (3B), diluted 1:400. Aliquots were incubated with dissociation buffer at pH 7 (open bar, 120 min) or pH 2.5 (solid bars) for 5, 20, 30, 90 and 120 minutes. The ELISA assays were completed as described in methods and the optical density at 450 nm used to estimate the amount of antibody binding to the ELISA plate. Results are presented as mean ± SEM. * P < 0.05; ** P < 0.001 compared to pH 7.0.