Interferon production by Theileria annulata ‐transformed cell lines is restricted to the beta family

Theileria are tick‐transmitted protozoans causing often fatal diseases in ruminants . Theileria sporozoites immortalize and transform host cells of haematopoietic origin. Transformation is associated with profound functional alterations. For example, bovine cells infected by Theileria annulata or T. parva . constitutively produce interferon (IFN). In this study, the type and family of IFN produced by a panel of T. annulata ‐transformed cell lines and a T. parva ‐transformed cell line was investigated, using molecular probes specific for the members of the IFN‐α, IFN‐β, IFN‐γ and IFN‐ω family . T. parva ‐transformed cells produced IFN‐γ exclusively, whereas T. annulata ‐infected cells expressed type I IFN only. Analysis of mRNA expression showed that this type I IFN was confined to IFN‐β, regardless of the cellular origin of the transformed cells. When cells were exposed to double‐stranded RNA (poly (I:C)) which induces IFN production in other systems, a 10–5,000fold increase in IFN activity was noted. The amounts of IFN‐β mRNA were inceased, but mRNA coding for IFN‐α, IFN‐ω or IFN‐γ was not detected. In contrast, primary macrophages, from which many of the tested lines were derived, expressed IFN‐α, IFN‐β and IFN‐ω mRNA to similar degrees when stimulated by LPS or poly (I:C). Thus, T. annulata appears to constitutively turn on IFN‐β gene transcription while silencing the genes coding for IFN‐α and IFN‐ω .