Establishment of neonatal <i>S</i>. <i>pneumoniae</i> infection model and schematic of study protocol.

<p>Neonatal BALB/c mice were divided into the following groups: infected non-allergic (Neo), infected allergic (Neo/OVA), uninfected allergic (OVA), and uninfected non-allergic (control). Mice were infected intranasally with <i>S</i>. <i>pneumoniae</i> or phosphate-buffered saline (PBS) on day 0 (1 week-old). The <i>S</i>. <i>pneumoniae</i> clearance time (A) and the body weight (B) were monitored. Mice were sensitized by an i.p. injection of ovalbumin (OVA) or PBS on days 21 and 28, and challenged with aerosolized OVA or PBS to induce allergic airways disease (AAD) on days 35–42. Key features of AAD were characterized within 24 h after the final challenge (on day 43) (C).