Antibody Responses Elicited by Vaccination with Recombinant LaSota Virus Expressing IBV Spike in Chickens with Maternal Antibodies.

Vaccination with a recombinant Newcastle disease virus (NDV) LaSota (LS) strain expressing Arkansas (Ark) -type infectious bronchitis virus (IBV) spike ectodomain (Se) protein and granulocyte-macrophage colony-stimulating factor (GMCSF) (rLS/ArkSe.GMCSF, where rLS stands for recombinant LS) was evaluated in chickens of commercial origin with NDV and IBV maternally derived antibodies (MDAs). Chickens were vaccinated ocularly with rLS/ArkSe.GMCSF at either 2, 8, 15, or 30 days of age (DOA). Control chickens were vaccinated with the rLS virus (not expressing IBV SE or GMCSF) on the same days. Specific-pathogen-free (SPF) chickens also were vaccinated with either virus at 2 days old. The results showed detection of NDV RNA in lacrimal fluids of vaccinated chickens, indicating successful replication of the recombinant virus at periocular mucosal sites. IBV IgA in lacrimal fluids and serum IBV antibodies were determined by ELISA using recombinant IBV Ark S1-protein-coated plates. Vaccination at 2 DOA with rLS/ArkSe.GMCSF in chickens with MDAs elicited an IBV IgA response in lacrimal fluids. Chickens with MDAs vaccinated with rLS/ArkSe.GMCSF at 8 days old showed IgA levels in lacrimal fluids not differing significantly from levels achieved upon vaccination at 2 DOA. Vaccination at 30 days old did not result in increased IBV IgA levels in tear fluids of birds with MDAs compared to unvaccinated birds with MDAs. Vaccination with rLS/ArkSe.GMCSF of chickens with MDAs resulted in limited IBV and NDV serum antibody responses. We conclude that vaccination with rLS/ArkSe.GMCSF induces IBV IgA at periocular mucosae but limited serum antibody responses in chickens with NDV MDAs.