Three novel Anas platyrhynchos avian β-defensins, upregulated by duck hepatitis virus, with antibacterial and antiviral activities

► Three novel Anas platyrhynchos avian β-defensins (Apl_AvBDs) were identified successfully and characterized in tissues from Peking ducks. ► Both recombinant and synthetic forms of the three Apl_AvBDs showed antibacterial activity against most of the bacteria investigated. ► Significant antiviral activity of the three Apl_AvBDs was shown against duck hepatitis virus (DHV). However, none of the Apl_AvBDs showed significant hemolytic activity. ► Expression of the three Apl_AvBDs showed different levels in different tissues of ducklings at different time points after DHV infection. ► The present results demonstrate that Apl_AvBDs play vital roles in the immune response of ducks against bacterial and viral pathogens.