3.3. Protection of chickens against IBV challenge
Following challenge with LX4, 15/16, 12/16, and 13/16 chickens in the rFPV-IBVS1, rFPV-IBVS1-ChIFNγ and H120, respectively, were protected from clinical signs of IB (Table 1). All vaccinated chickens of the above three groups survived, except one chicken that died in FPV-IBVS1 group on day 3 post-challenge. In contrast, 14/16 chickens of the S-FPV-017 group and 16/16 chickens of the control (non-vaccinated) group developed clinical signs after challenge (Table 1). All deaths occurred between days 3 and 5 post-challenge. Necropsies revealed typical pathology of acute IB, which was restricted to the upper respiratory tract and kidneys, such as suffusion of mucus in the upper respiratory tract, swelling of the throat, bleeding in the trachea and swollen kidney in mud-like gray with piebalds.