Short chain fatty acids facilitate protective immunity by macrophages and T cells during acute fowl adenovirus-4 infection.

Short chain fatty acids (SCFAs) are major gut metabolites that are involved in the regulation of dysfunction in immune responses, such as autoimmunity and cytokine storm. Numerous studies have reported a protective action of SCFAs against infectious diseases. This study investigated whether SCFAs have protective effect for immunity during fowl adenovirus-4 (FAdV-4) infection. We examined whether SCFA mixture (acetate, propionate, and butyrate) administration could protect against intramuscular challenge of a virulent viral strain. SCFA treatment promoted MHCII-expressing monocytes, the active form of T cells, and effector molecules in both peripheral and lymphoid tissues. It also boosted the production of immune molecules involved in pathogen elimination by intraepithelial lymphocytes and changed the intestinal microbial composition. We suggest that gut metabolites influence the gut microbial environment, and these changes stimulate macrophages and T cells to fight against the intramuscular challenge of FAdV-4.