Mannan Oligosaccharide Protects against the Aflatoxin-B1-Promoted Influenza Replication and Tissue Damages in a Toll-Like-Receptor-4-Dependent Manner.

Our previous study reported that aflatoxin B1 (AFB1) promoted influenza replication. Mannan oligosaccharide (MOS), derived from the cell walls of yeast, is a potent immunomodulator. Here, we investigated the role of MOS in AFB1-promoted influenza replication and further explored the underlying mechanisms. In vitro and in vivo, the exposure to AFB1 alone resulted in significantly decreased weight gain and increased viral replication as well as lung and spleen damages. Increased influenza replication coupled with increases in toll-like receptor 4 (TLR4), phosphorylated nuclear factor κB, and tumor necrosis factor α (TNF-α) levels. However, MOS given in conjunction with exposure to AFB1 significantly reversed these above changes. A further study indicated that MOS activity was abolished by TLR4 knockout or TLR4 overexpression. Surprisingly, TNF-α played no role in the MOS-mediated protective effects. Collectively, our data suggest that MOS alleviates the AFB1-promoted influenza replication, inflammation, and tissue damages in a TLR4-dependent manner.