Polysaccharide BAP1 of Bifidobacterium adolescentis CCDM 368 attenuates ovalbumin-induced allergy through inhibition of Th2 immunity in mice

Allergies have become a growing problem and the number of cases is increasing yearly. Administration of postbiotics, well-defined bacterial molecules, is gaining attention as a novel and promising strategy to ameliorate the allergic burden. The BAP1 polysaccharide (PS) of Bifidobacterium adolescentis CCDM 368, was previously characterized by us regarding its structure and in vitro immunomodulatory properties. Here, to decipher the effect of BAP1 on immune system development, it was intranasally (i.n.) administered to germ-free mice. We observed increased IgA in bronchoalveolar lavage (BAL) fluid, decreased CCL2 production, and higher Rorc gene expression in the lung. The intranasal administration of BAP1 reduced lung inflammation and decreased eosinophils numbers in BAL in the ovalbumin-induced allergy mouse model. Moreover, BAP1 decreased OVA-specific IgE levels in sera and Th2-related cytokines in OVA-stimulated splenocytes and lung cells. Finally, increased Rorc and inhibited Il10 gene expression were observed in lung tissue indicating their possible role in BAP1 function. Our findings support and expand on our previous in vitro and ex vivo studies by demonstrating that BAP1, with a unique chemical structure, induces a specific immunomodulatory effect in the host and could be potentially used for alleviating allergic diseases.