Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 12, 2000
Publication Date: N/A
Interpretive Summary: Cell-mediated immunity (CMI) plays an important role in host resistance to diseases. Recent studies show that CMI is mediated by soluble factors called cytokines which are secreted by lymphocytes and macrophages. In chickens, progress in understanding cell-mediated immunity is hampered by inability to assay cellular response of chickens. In this study, ARS scientists developed the first in vitro assay to assess a cytokine called interferon-gamma (IFN-gamma) which is produced by activated T cells. This assay uses specific mouse monoclonal antibodies (mabs) which detect chicken IFN-gamma and can be used to measure IFN-gamma production in serum and in other body fluids in chickens. Since IFN-gamma plays an important role in CMI, the ability to measure this cytokine in various biological samples will enhance scientists' ability to assess chicken cellular responses to vaccines and infectious agents. This will enable the poultry industry to use more effective vaccines.
Twelve mabs against native or recombinant chicken IFN-g were produced and characterized by virus neutralization, ELISA, and Western blot assays. No data were obtained to suggest that the form of the immunogen (native vs. recombinant) influenced the antigenic specificity of the mabs produced. While only 2 antibodies inhibited the in vitro virus neutralizing activity of IFN-g, other evidence indicated that the specificity of these mabs was indeed directed against IFN-g. By Western blot analysis all antibodies identified a 17-kDa IFN-g polypeptide. Using a direct binding ELISA incorporating these mabs, a high correlation with IFN-g detected by in vitro virus neutralization was observed. The IFN-g ELISA was also capable of measuring cytokine levels in the sera of chickens orally infected with Eimeria maxima. At 8 and 10 days post-primary infection, significantly higher (p < 0.001) levels of serum IFN-g were detected in E. maxima infected chickens compared to uninfected controls. These results indicate that a mab-based direct binding ELISA is suitable to measure chicken IFN-g in a variety of formats.