Lactobacillus paracasei feeding improves immune control of influenza infection in mice. Lactobacillus paracasei feeding improves immune control of influenza infection in mice

Respiratory tract infections such as flu are still causing severe morbidity and mortality and are among the leading causes of death in children and adults worldwide. Commensal microbiota is critical in orchestrating tissue homeostasis and immunity in the intestine. Whereas probiotics represent an interesting source of immune modulators, several clinical studies addressed potential beneficial effect of probiotics against respiratory infections. Here, we have investigated the mechanisms of protection conferred by L. paracasei CNCM I-1518 strain in a mouse model of influenza infection. Notably, local myeloid cells accumulation is generated in the lungs after seven days feeding with L. paracasei and prior the viral infection. L. paracasei-fed mice showed impaired susceptibility of the influenza infection associated with less accumulation of inflammatory cells in the lungs, faster viral clearance and general health improvement. Interestingly, Allobaculum was significantly increased in L. paracasei-fed mice 7 days after influenza infection, even if gut microbiota composition was not overall altered. L. paracasei-purified peptidoglycans were partially recapitulating protective phenotype observed with the entire bacteria. Our results show that oral consumption of L. paracasei CNCM I-1518 modulates lung immunity associated with an improved control of influenza infection. Collectively, our results suggest a beneficial role for certain lactobacilli to alleviate the burden of respiratory tract infections.