Maternal antibody to infectious bronchitis virus: its role in protection against infection and development of active immunity to vaccine

Chicks hatched with high levels of maternal antibody had excellent protection (>95%) against infectious bronchitis virus (IBV) challenge at 1 day of age, but not at 7 days (<30%). This protection significantly (P<0.05) correlated with levels of local respiratory antibody and not with serum antibody. A high percentage of both maternal antibody-positive (Mab+) and maternal antibody-negative (Mab−) chicks failed to produce IBV antibody when vaccinated at 1 day of age by the intraocular route. In addition, Mab+ chickens had a weaker virus-neutralizing antibody response to a second IBV vaccination compared to Mab− birds (P<0.05). Mab+ chicks experienced a more rapid decline (P<0.01) in maternal antibody after 1-day-of-age vaccination compared to their unvaccinated counterparts. A monoclonal antibody-based blocking ELISA that measured antibody levels specific to S1 glycoprotein of IBV correlated well with virus-neutralizing antibody titers.