IgM responses in chicken serum to live and inactivated infectious bronchitis virus vaccines

Intramuscular (i.m.) administration of infectious bronchitis virus (IBV) oil-emulsion vaccine (OEV) to IBV-primed or unprimed chickens resulted in the production of zero or minimal concentrations of IBV-specific IgM in the serum, as measured by enzyme-linked immunosorbent assay of gel chromatography fractions. Live-attenuated infectious bronchitis (IB) vaccine given i.m. or by eyedrop stimulated the production of IBV-specific IgM in similar amounts following inoculation by both routes. These levels were comparable to those found in earlier studies following intranasal inoculation with a virulent strain of IBV and confirm that the detection of IBV-specific IgM is a valuable aid to the diagnosis of recent infection. As expected, administration of live-attenuated IB vaccines i.m. or by eyedrop protected the respiratory tract against challenge with virulent virus 24 days later; however, OEV given i.m. did not.