Effects of a combination of Mass and Dutch variant as an inactivated vaccine against variant 2 avian infectious bronchitis virus challenge.

The present study aimed to evaluate the effects of inactivated vaccines combining Mass and Dutch variants as vaccine boosters after H120 priming on inhibiting variant 2 viral load in the kidneys (as the target organ) and reducing fecal shedding. Ciliostasis score and antibody response were investigated as well. A total of 150 specific-pathogen-free (SPF) chicken were divided into six groups. All groups were vaccinated with a single dose of attenuated H120 vaccine except for two (no vaccine groups). Then, three groups received booster vaccines with inactivated polyvalent vaccines. At the 42 day of age, all groups were challenged with variant 2 viruses except for one (no vaccine group). Next, antibody response and infectious bronchitis virus viral load in kidneys and fecal shedding were evaluated by the enzyme-linked immunosorbent assay and quantitative real-time polymerase chain reaction. Then the ciliostasis score was investigated. In general, a vaccination program including a mass serotype attenuated vaccine (H120) as priming and polyvalent vaccines can significantly protect chickens against variant 2 infection through reducing viral load in kidneys and fecal shedding. Furthermore, the vaccination program can decrease ciliostasis in the epithelial ciliary tissue.