Systemic and local antibody responses to infectious bronchitis virus in chickens inoculated with infectious bursal disease virus and control chickens.

Serum and local (respiratory) antibody responses to infectious bronchitis virus (IBV) were studied in 5-wk-old white leghorn-type control chickens and chickens inoculated with infectious bursal disease virus (IBDV) at 1 day of age. Of the chickens inoculated with IBV alone, 93% had detectable levels of IBV antibodies in the sera and 87% had detectable antibodies in the respiratory lavage fluids. Compared to this group, only 73% and 65% of IBDV-IBV inoculated chickens had serum and respiratory antibodies, respectively. In chickens inoculated with IBV alone, the IBV antibodies were evenly associated with immunoglobulin classes IgM, IgG, and IgA, whereas the IBDV-IBV inoculated chickens mainly produced IgM-associated antibodies with low to negligible levels of IgA- and IgG-associated antibodies. These results suggest that the lack of adequate IgA- and IgG-associated antibody production in IBDV-infected chickens may account for their increased susceptibility to IBV infection.