An Inactivated Novel Trivalent Vaccine Provides Complete Protection against FAdV-4 Causing Hepatitis-Hydropericardium Syndrome and FAdV-8b/-11 Causing Inclusion Body Hepatitis

Outbreaks of hepatitis-hydropericardium syndrome (HHS) caused by fowl adenovirus serotype 4 (FAdV-4) and inclusion body hepatitis (IBH) related to FAdV-8b and FAdV-11 have been increased in chickens in China since 2015. Clinical concurrent infections of FAdV-4, FAdV-8b, and FAdV-11 are quite common, yet there are no commercially available trivalent vaccines against infection by these three serotypes. In our previous study, a bivalent vaccine based on a recombinant FAdV-4, of which fiber-1 was replaced with the fiber of FAdV-8b, has been developed. In this study, a novel recombinant rFAdV-4-fiber/8b + 11 was constructed by inserting FAdV-11 fiber gene into the 1966-bp deletion region of rFAdV-4-fiber/8b genome. The in vitro replication ability of the rFAdV-4-fiber/8b + 11 was similar to the parental FAdV-4. One dose immunization with the inactivated rFAdV-4-fiber/8b + 11 vaccine generated robust immune responses against FAdV-4, FAdV-8b, and FAdV-11, and provided efficient clinical protection against FAdV-4, FAdV-8b, and FAdV-11 challenge. This study provides a novel strategy for developing potential trivalent vaccines for the prevention and control of HHS and IBH.