Figure 1.

Interaction between host immunity, gut microbiota and viral pathogens in gut mucosa. Abbreviations: intraepithelial lymphocytes (IELs), innate lymphoid cells (ILCs), short-chain fatty acids (SCFAs). The gastrointestinal epithelium is composed of a single-cell layer that separates the intestinal lumen from the underlying lamina propria. Host immune cells including dendritic cells, γδ T cells, αβ T cells, ILCs, macrophages and B cells survey the IELs are interspersed throughout the epithelium and are positioned both within and directly below the epithelium. The mucus layer, containing mucins, provides a physical barrier between pathogens and host epithelia. Gut microbiota can influence mucin production with potential antiviral properties. Gut microbes including lactic acid bacteria can regulate tight junctions and thus maintain normal mucosal permeability and produce antimicrobial compounds (bacteriocins) that can inhibit viral attachment. Lastly, gut microbiota can modulate immune cell functions through the production of SCFAs in the small intestine and stimulate γδ T cell and ILC functions.