Cryptosporidium parvumInfection Rapidly Induces a Protective Innate Immune Response Involving Type I Interferon

Abstract

Type II interferon (IFN), IFN-γ, is important in innate immunity to the intestinal protozoan parasite Cryptosporidium species, which infects epithelial cells (enterocytes). This investigation is, to our knowledge, the first to characterize the role of type I IFN in innate immunity to this parasite. Pretreatment of human or murine enterocyte cell lines with IFN-α/β inhibited parasite development, and we identified that a key mechanism of cytokine action was to prevent parasite invasion of enterocytes. IFN-α/β was rapidly expressed by infected murine enterocytes and also by bone marrow-derived dendritic cells that were exposed to live parasites. Treatment of neonatal severe combined immunodeficiency mice with anti-IFN-α/β neutralizing antibodies before infection increased oocyst reproduction, as measured at the peak of infection, and parasite numbers in gut epithelium were also increased 2 days after infection. The latter observation correlated with strong intestinal expression of both IFN-α and IFN-β messenger RNA within 24 h after infection. Treatment with anti-IFN-α/β, however, did not reduce early expression of IFN-γ. These findings identify a novel early innate host response against Cryptosporidium parvum involving IFN-α/β