Respiratory syncytial virus infection reversed anti-asthma effect of neonatal Bacillus Calmette-Guerin vaccination in BALB/c mice.

Bacillus Calmette-Guerin (BCG) vaccination can protect animals from asthma, but the effect of BCG on childhood asthma prevention is controversial in humans. To verify the hypothesis that the BCG anti-asthma effect in childhood might be reversed by a respiratory virus infection, newborn BALB/c mice were divided into five groups. Control and ovalbumin (OVA) groups were mock vaccinated and mock infected. The BCG/OVA group was BCG vaccinated and mock infected. The respiratory syncytial virus (RSV)/OVA group was mock vaccinated and RSV infected. The BCG/RSV/OVA group was BCG vaccinated and RSV infected. Except for the control group, all groups underwent OVA sensitization and challenge. Airway hyperresponsiveness (AHR) was measured after challenge and cells in bronchoalveolar lavage fluid (BALF) were counted. Cytokines in BALF and serum OVA-specific IgE were detected by ELISA and inflammatory characteristics of lung sections were scored. Mice with neonatal BCG vaccination (BCG/OVA group) were significantly protected from BALF eosinophilia, AHR to methacholine, peribronchiolitis, alveolitis, and peribronchial eosinophilia in comparison with the OVA, RSV/OVA, and BCG/RSV/OVA groups. AHR in the OVA group was greater than in the BCG/OVA group but lower than in the RSV/OVA and BCG/RSV/OVA groups. No significant differences in BALF eosinophilia, AHR, and lung inflammation were found between the RSV/OVA and BCG/RSV/OVA groups. The impact of BCG vaccination on anti-asthma in mice was not dependent on interferon-gamma, IL-4, and IL-10 levels. The results suggested that RSV infection can reverse the anti-asthma effect of neonatal BCG vaccination in BALB/c mice.