Re-Challenge with Ovalbumin Failed to Induce Bronchial Asthma in Mice with Eosinophilic Bronchitis

Objective To investigate whether eosinophilic bronchitiswithout airway hyperresponsiveness will develop bronchial asthma in allergic mice. Methods Mice were sensitized with OVA on days 0, 7, and 14, challenged on days 21 to 23 (1st OVA challenge), and re-challenged on days 46 to 48 (2nd OVA challenge), intranasally with 10 (the EB group) and 200 (the AS group) μg OVA. Lung resistance (RL) was assessed 24 h after each challenge and on day 45 followed by analysis of leukocyte distribution in the bronchoalveolar lavage (BAL) fluid and histological examination. Results Twenty-four hours after the 1st OVA challenge, aerosolized methacholinecaused a dose-dependent increase in RL in all groups. At doses ≥1.56 mg/mL, RL in the AS group was significantly higher than that of the NS-1 group (P 0.05). At doses ≥12.5 mg/mL, RL in the AS group was significantly higher than that of the control group and EB group (P<0.01 or 0.05). The percentage of eosinophils in the AS group was noticeably higher than that of the EB group(P<0.05). Furthermore, there was apparent infiltration by inflammatory cells, predominantly eosinophils, into the sub-epithelial region of the bronchusand the bronchiolesand around the vessels in the EB and AS group. Conclusion Re-challenge with low doses of ovalbumindid not increase airway reactivity and failed to induce bronchial asthma in mice with ovalbumin-induced EB.