BL23 modulates the innate immune response in -stimulated bovine mammary epithelial cells.

Probiotics have been adopted to treat and prevent various diseases in humans and animals. They were notably shown to be a promising alternative to prevent mastitis in dairy cattle. This inflammation of the mammary gland is generally of infectious origin and generates extensive economic losses worldwide. In a previous study, we found that BL23 was able to inhibit the internalisation of , one of the major pathogens involved in mastitis, into bovine mammary epithelial cells (bMEC). In this study, we further explored the capacity of this strain to modulate the innate immune response of bovine mammary epithelial cells during infection. BL23 was able to decrease the expression of several pro-inflammatory cytokines, including interleukins 6, 8, 1α and 1β and tumour necrosis factor alpha, in -stimulated bMEC, 8 h post-infection. On the other hand, did not impair the induction of defensins, such as lingual antimicrobial peptide and defensin β1 in the presence of , and even slightly increased the induction of tracheal antimicrobial peptide during infection. Finally, this strain did not alter the expression of the pattern recognition receptor nucleotide-binding oligomerisation domain proteins (NOD2). This study demonstrates that BL23 displayed anti-inflammatory properties on -stimulated bMEC. These results open the way to further characterisation of the BL23 probiotic potential in a bovine mammary gland context and to a better understanding of how all these beneficial properties combine to combat mastitis pathogens.