INDUCTION OF PROTECTIVE IMMUNITY IN CHICKENS VACCINATED WITH INFECTIOUS-BRONCHITIS VIRUS S1 GLYCOPROTEIN EXPRESSED BY A RECOMBINANT BACULOVIRUS

A recombinant baculovirus containing the S1 glycoprotein gene of the v irulent nephropathogenic KM91 strain of infectious bronchitis virus (I BV) was constructed in order to investigate protective immunity in vac cinated chickens, Results from the protection test were evaluated by r e-isolation of virus from the kidneys and tracheas of vaccinated chick ens after challenge with strain KM91. After three immunizations, the r ecombinant S1 (rS1) glycoprotein induced 50% protection of the kidney, whilst inactivated KM91 induced 88% and 50% protection of the kidney and trachea, respectively, In chickens primed with the attenuated H120 vaccine strain, which is heterologous to KM91, the rS1 glycoprotein i nduced 83% protection of the kidney after two immunizations. Haemagglu tination-inhibition titres were also increased in chickens immunized w ith the rS1 glycoprotein after three immunizations, and significantly higher titres were detected after challenge, These data indicate that the expressed rS1 glycoprotein alone can induce a protective immune re sponse as well as an antibody response.