An indirect enzyme–linked immunosorbent assay (ELISA) was developed for screening of antibody to avian infectious bronchitis virus (IBV). Antigen was prepared from whole-purified IBV Massachusetts serotype (BR 801 strain). Optimum dilution with minimum background for antigen concentration, rabbit anti-chicken conjugate and sera in developed ELISA was determined 0.1μg/ml, 1:3000 and 1:100, respe...