Recombinant Interferon-γ Inhibits Cell Invasion byEimeria tenella

Abstract

Treatment of primary chicken kidney (CK) cultures with supernatants from concanavalin A-treated Eimeria tenella-immune avian splenic T cells significantly inhibited the invasion of the cells by sporozoites of E. tenella. Biochemical evaluation of this T-cell factor is consistent with the idea that this anti-Eimeria activity in the avian lymphokines is due to interferon-γ (IFN-γ). We then studied the effect of recombinant bovine and human IFN-γ on the invasion of sporozoites of E. tenella in cultures of bovine and human cell lines, respectively. The initial infection of either the Madin–Darby bovine kidney cell line (MDBK) or the human larynx epidermoid carcinoma cell line (HEp-2) by the obligate intracellular protozoan parasite E. tenella was inhibited following a 24-h pretreatment with recombinant bovine or human IFN-γ, respectively. The IFN-γ-mediated inhibition was dose-dependent for both cell lines. Incubation of sporozoites of E. tenella with IFN-γ alone before infection had no detectable inhibitory effect on cell invasion of either cell line by the parasite. In addition, the establishment of the antiinfective cellular state by IFN-γ required at least a 16- to 24-h preincubation for significant inhibitory effects. These results are suggestive of a direct effect of the IFN-γ on the host cells and not on the parasite themselves. Taken together these studies provide evidence for a role for IFN-γ as a nonspecific mediator of host protection against coccidiosis.