Ambient ammonia does not appear to inhibit the immune response to infectious bronchitis virus vaccination and protection from homologous challenge in broiler chickens

This study examined the effect of NH3 on the immune response to infectious bronchitis virus (IBV) vaccination and protection against homologous serotype challenge in commercial broiler chickens. One-day-old chicks were administered IBV vaccine and exposed to 30-60 ppm of NH3. At 28 DOA, birds were challenged oculonasally with a pathogenic homologous IBV, and protection was measured by viral detection, clinical signs, ciliostasis, and presence of airsacculitis. IBV-specific serum IgG and lacrimal fluid IgA titers, as well as Harderian gland (HG) immune cell phenotypes, were evaluated. Ammonia exposure was associated with an increased incidence of airsacculitis among non-vaccinated, challenged birds. Vaccinated, NH3-exposed birds were completely protected from IBV challenge. Ammonia had subtle effects on cilia morphology and function but did not affect vaccine or challenge virus replication and clearance, clinical signs, ciliostasis, tracheal histopathology scores, or immune responses. In the HG of vaccinated birds, the percent of leukocytes, MHC I+/MHC IIhi expression, IgM+ expression, and CD8+ expression was increased, while mucosal IgA and serum IgG titers were nominal. Non-vaccinated, IBV-challenged birds exhibited an increased percent of leukocytes, MHC I+/MHC IIhi expression, and IgM+ expression in the HG at 5 dpc, followed by increased mucosal IgA and serum IgG titers and CD8+ expression at 10-14 dpc. In contrast, vaccinated, IBV-challenged birds had a minimal increase...
Source: Veterinary Immunology and Immunopathology - Category: Veterinary Research Source Type: research