Maternal Antibody Transfer of a Fiber-Based Subunit Vaccine Confers Complete Protection Against Fowl Adenovirus Serotype 11 in Neonatal Chickens

Abstract

Simple Summary Highly virulent fowl adenovirus serotype 11 (FAdV-11) causes inclusion body hepatitis (IBH) and mass death in newly hatched broilers, generating severe economic losses for poultry farms worldwide. Young chicks under 7 days old are extremely susceptible to this virus, yet their immature immune systems cannot gain effective protection via routine active vaccination. In this work, we designed a truncated soluble trimeric Fiber antigen and verified its natural protein structure. Vaccinating breeder hens with this subunit vaccine induced high levels of protective antibodies that pass to offspring through egg yolk. After lethal virus exposure, all 1-day-old chicks carrying maternal antibodies survived with no disease signs, liver lesions or detectable virus in organs, while all unprotected control chicks died within five days. This breeder vaccination strategy delivers full passive protection to neonatal chicks under laboratory conditions, offering a promising candidate solution for FAdV-11 control in commercial poultry production pending further validation under commercial field conditions.