Effect of infectious bursal disease virus on the immunological responsiveness of the chicken

The immunological response of chickens infected at 28 days of age with infectious bursal disease virus (IBDV) was examined. Cellular immunity was studied by the graft-versus-host reaction and delayed type hypersensitivity skin reactions to tuberculin. Antibody responses to sheep red blood cells (S-RBC's) were tested by a direct hemagglutination test. Circulating levels of immunoglobulins (Ig's) IgM, IgG and IgA were monitored by the radial immunodiffusion test. The results of the graft-versus-host reaction and delayed type hypersensitivity reactions were similar for both the infected and control chicks. IBDV significantly reduced the primary antibody response to S-RBC's, but had no marked effect on the secondary antibody response. Chicks infected with IBDV had normal levels of serum IgM and IgG, but significantly lower levels of IgA when compared to uninfected control birds.