Chicken viperin inhibits fowl adenovirus serotype 4 replication and affects related innate immune signaling pathways

Fowl adenovirus serotype 4 (FAdV-4) is the main pathogen causing hydropericardium‑hepatitis syndrome (HHS), which seriously endangers the poultry industry. Viperin, an interferon‑stimulated gene (ISG), possesses broad‑spectrum antiviral activity, but its role during FAdV‑4 infection remains unclear. In this study, the chicken viperin gene was cloned and expressed, and its sequence characteristics, protein structure and tissue distribution were systematically analyzed. By overexpressing or silencing viperin in chicken hepatocellular carcinoma (LMH) cells, the effect of viperin on FAdV‑4 replication was investigated; meanwhile, this study examined the expression levels of multiple factors associated with innate immune signaling pathways under different treatment conditions, to investigate the regulatory role of viperin in the innate immune response induced by FAdV‑4. The main results showed that chicken viperin is a ∼41 kDa protein predominantly composed of α‑helices and random coils, and is highly expressed in immune organs. Overexpression of viperin significantly reduced FAdV‑4 viral load and titer, whereas knockdown of viperin promoted viral replication. The expression levels of several innate immune factors, including LGP2, MDA5 and MAVS, varied under different conditions. This study preliminarily demonstrates that chicken viperin inhibits FAdV‑4 replication. By measuring the expression changes of multiple innate immune factors under different conditions, we analyzed and conjectured the innate immune regulatory mechanism of viperin against FAdV‑4. This research provides an important theoretical basis and potential molecular targets for the design of antiviral prevention and control strategies in poultry as well as for the development of next‑generation vaccine adjuvants. Moreover, it offers research directions and experimental ideas for further in‑depth dissection of the molecular mechanism by which viperin inhibits FAdV‑4.