Infectious bronchitis: effect of viral doses and routes on specific lacrimal and serum antibody responses in chickens.

An enzyme-linked immunosorbent assay was used to measure the effect of various infectious bronchitis virus (IBV) (strain H-120) vaccine doses and routes of immunization on specific lacrimal and serum antibody responses. The results of the first trial showed that the maximum dose, 10(6) median embryo infective doses (EID50s), delivered by the ocular route elicited both a systemic and a local antibody response in the vaccinated chickens. Lower doses of vaccinal virus, 10(4) (median dose) and 10(2) (minimum dose) EID50 delivered by the same route did not induce a detectable systemic antibody response. A significant increase of IBV-specific lacrimal IgA was elicited by both the maximum and the median vaccine doses. The low vaccine dose (10(2) EID50) did not induce a detectable increase of lacrimal IgA. In a second trial approximately the same vaccine dose was administered to different chicken groups by ocular instillation, drinking water, spray, and cloaca. The results showed that all routes of vaccination tested, including the cloacal route, resulted in an increase of specific serum antibodies. Higher IgG levels were detected throughout the experimental period after vaccination by the ocular route as compared with vaccination via the drinking water. All routes of vaccination tested resulted in an increase of specific IgA in lacrimal fluid. The vaccine application methods spray, ocular instillation, and drinking water induced similar lacrimal IgA responses.