Intranasal probiotic Lactobacillus rhamnosus GG prevents respiratory exacerbation in a mouse model of birch pollen allergic asthma

Abstract

The increasing prevalence of allergic airway diseases in industrialized countries has been associated with high hygienic standards and reduced microbial exposure. Probiotic lactic acid bacteria, such as certain Lactobacillus strains, were shown to have potentially beneficial immunomodulatory properties. Therefore, we determined the effect of intranasal administration of L. rhamnosus GG (LGG) and GR-1 (LGR-1) in a mouse model of birch pollen-induced allergic asthma. The symptoms of allergic asthma were induced with 7 intranasal applications with 1- or 2-day interval with birch pollen extract. The asthma induction protocol was preceded by 8 intranasal administrations of LGG or LGR-1 at a concentration of 5 x 108 CFU/dose over the course of two weeks on four consecutive days each week. We assessed serum antibody levels, bronchoalveolar lavage (BAL) cell counts, lung histology, lung cytokine levels, airway hyperreactivity. LGG administration resulted in a significant decrease in allergic airway inflammation (BAL eosinophils, lung IL-13 and IL-5 levels) and a significantly reduced number of respiratory exacerbations. Contrary to LGG, no decisive results were obtained for LGR-1. Longitudinal in vivo lung micro-computed tomography (micro-CT) is currently ongoing to determine inflammatory exacerbation. Complementary to micro-CT, fluorescence imaging (FLI) of a fluorescent LGG strain will be performed to understand the probiotic-host interactions at the whole-body and whole-organ level. In conclusion, bacterial strain-specific beneficial effects of intranasally administered LGG were observed in a mouse model of birch pollen-induced allergic asthma.