exerted different antiviral effects on respiratory syncytial virus infection in mice.

Respiratory syncytial virus (RSV) infection is a constant threat to the health of young children, and this is mainly attributed to the lack of effective prevention strategies. This study aimed to determine whether () , a potential probiotic, could protect against respiratory viral infection in a mouse model. Naive 3-4-week-old BALB/c mice were orally administered with three strains (2.5 × 10 CFU/mouse) 7 days before RSV infection (10 TCID/mouse). Results showed that all three strains inhibited RSV replication and reduced the proportions of inflammatory cells, including granulocytes and monocytes in the blood. The M104R01L3 treatment maintained stable weight in mice and increased interferon (IFN)-β and tumor necrosis factor (TNF)-α levels. The DCC1HL5 treatment increased interleukin (IL)-1β and IL-10 levels. Moreover, the M104R01L3 and DCC1HL5 strains increased the proportions of , , and which contributed to the advantageous modulation of the gut microbiota. Besides, affected the gut levels of short-chain fatty acids (SCFAs) that are important for the antiviral response. 1,025 increased acetate, propionate, and butyrate levels, whereas M104R01L3 increased the level of acetate in the gut. M104R01L3 may protect against viral infection by upregulating the IFN-β levels in the lungs and its antiviral effect may be related to the increase of acetate levels in the gut. In conclusion, the three strains exerted antiviral effects against RSV infection by differentially regulating immune responses and intestinal micro-ecological balance. This study can provide a reference for studying the mechanisms underlying the antiviral effects of .