A novel recombinant chimeric Fiber-8a/8b-AD subunit vaccine provides complete protection against both FAdV-8a and FAdV-8b.

In recent years, outbreaks of fowl adenovirus (FAdV) in domestic chicken populations in China, particularly fowl adenovirus serotype 8 (FAdV-8), have attracted significant attention due to its role as a major causative agent of inclusion body hepatitis (IBH). Although FAdV-8 exhibits lower virulence compared to FAdV-4, its ability to co-infect with other pathogens presents new challenges for vaccine development. In this study, full-length and chimeric expression technologies were applied to develop four novel subunit vaccines using Fiber proteins from FAdV-8a and FAdV-8b strains: Fiber-8a-AB, Fiber-8b-CD, Fiber-8a/8b-AD, and Fiber-8b/8a-CB. Immunogenicity experiments indicated that the Fiber-8a/8b-AD subunit vaccine induced production of antibodies at 14 days of age earlier than the other three subunit vaccine. Moreover, the neutralizing antibody level of the Fiber-8a/8b-AD subunit vaccine group was higher than the three subunit vaccine groups. Immuno-challenge tests confirmed that this vaccine effectively protected chickens from weight loss, liver damage, and viral shedding post FAdV-8a and FAdV-8b infection. These findings valuable crucial insights for the development of new vaccines and suggest that the Fiber-8a/8b-AD subunit vaccine has the potential to serve as an effective alternative to inactivated whole-virus vaccines, with substantial commercial potential.