Immune response and in vivo distribution of the virus in chickens inoculated with the cell-associated vaccine of attenuated infectious laryngotracheitis (ILT) virus.

Chickens inoculated with the cell-associated (CA) vaccine acquired higher protective immunity to ILT. In chickens vaccinated with CA or cell-free (CF) vaccine, respectively, virus-neutralizing and IgG- and IgM-ELISA antibodies were detected in the serum, but no antibody was detected in the tracheal washes of the vaccinated chickens. More apparent antibody response was seen in chickens vaccinated with the CA vaccine than with the CF vaccine. The antibody titers did not correlate closely with the protection against challenge with ILT virus. After subcutaneous injection of either CA or CF vaccine, ILT virus was isolated from the liver, spleen, thymus, lungs and other organs of the chickens from 1 to 6 days after injection, and there was no correlation of the isolation rate for the CA-vaccinated and the CF-vaccinated chickens.