Immune protection efficacy of FAdV-4 surface proteins fiber-1, fiber-2, hexon and penton base

The spread of hydropericardium syndrome has recently become serious in China since 2015. There is, therefore, an urgent need for new, safe and effective vaccines that prevent the disease. Here, the immune protection induced by Escherichia coli-expressed capsid proteins of fowl adenovirus serotype 4, including fiber-1, fiber-2, penton base and hexon (loop-1 region) were compared in chickens at different inoculation amounts. According to challenge mortalities and tissue gross/micro lesion results, fiber-2 induced the best protection, followed by fiber-1 and hexon. Fiber-1 and fiber-2 provided complete protection against 105.5 TCID50 viral load challenge with 100 or 50 μg doses per chicken, respectively. Penton could induce effective protection only at the high dosage of 200 μg per chicken. The immunoprotective characteristics of these FAdV-4 capsid proteins may prove useful for developing subunit vaccines to control hydropericardium syndrome.