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.