Determination of the antigenic relationships within the Massachusetts (M41) type of infectious bronchitis virus using the hemagglutination-inhibition test.

The antigenic relationships, antigenic spectrum, and immunogenicity of seven IBV-Massachusetts-41 isolates were investigated using the hemagglutination-inhibition (HI) test. HI titers equal to 32 are considered suspicious, titers lower than 32 are considered negative, and titers higher than 32 are considered positive immune responses to infectious bronchitis virus (IBV). Some isolates of Massachusetts-41 ( M41 ) were capable of inducing large quantities of antibodies in chickens following inoculation and demonstrated a wider antigenic spectrum than others. Variations in antigenic spectrum observed within M41 isolates in this study are in agreement with previous reports. This variation is of importance in selecting a proper vaccine strain for a successful immunization program for IBV.