Recombinant chicken interferon-gamma-mediated inhibition of Eimeria tenella development in vitro and reduction of oocyst production and body weight loss following Eimeria acervulina challenge infection

Recombinant chicken interferon-gamma (chIFN-gamma) was produced in CHO-K1 or Spodoptera frugiperda (SF9) insect cells by transfect ion with a pcDNA vector or recombinant baculovirus (SF9-interferon-gamma [IFN-gamma]) carrying the chIFN-gamma gene. A rabbit antibody against a synthetic peptide corresponding to an immunogenic portion of chIFN-gamma recognized a 22-23-kDa band in SF3-IFN-gamma cell extracts by western blot analysis. Biological activity of recombinant chIFN-gamma was shown by its inhibition of vesicular stomatitis virus-induced cytotoxicity of chicken embryonic fibroblast cells in vitro. To investigate the role of chIFN-gamma during Eimeria infection, CHCC-OU2 chicken cells either pretreated with chIFN-gamma or stably transfected with the chIFN-gamma gene were infected with Eimeria tenella sporozoites. IFN-gamma demonstrated significant reductions in intracellular sporozoite development without affecting sporozoite invasion of host cells. Furthermore, chickens treated with recombinant chIFN-gamma showed decreased oocyst production and significant improvement in body weight gain following Eimeria acervulina challenge infection. These results provide the first direct evidence that chIFN-gamma exerts an inhibitory effect against Eimeria and provides a rational basis for use of this cytokine as a vaccine adjuvant against coccidiosis.