Immune Response in Chickens to Infectious Bronchitis Virus, Strain 33 II. Response to Virus Propagated in Chicken Embryo Kidney Cells

Abstract

Adaptation and propagation of 4 levels of chicken-embryo-passaged strain 33 of avian infectious bronchitis virus (IBV-33) in chicken embryo kidney (CEK) cells did not alter the infectivity of the virus for chicken embryos. One aerosol exposure with CEKpropagated IBV-33 was sufficient to prevent reinfection of trachea, lung, and kidney tissue by a second aerosol exposure 4 weeks later. All birds developed significant plaque-reduction neutralizing-index titers of 1.5 or greater prior to challenge. No respiratory signs were observed following challenge by contact exposure with infected birds. Virus content of tissues of immunized birds was either negative or of lower concentrations than in the controls. Intracellular IBV antigens were detected by immunofluorescence in trachea and lung-tissue smears which possessed virus titers of 1009 plaque-forming units per ml or greater. No correlation existed between intracellular IBV antigens and virus titers from tissues of challenge-exposed birds.