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

Theileria are tick-transmitted protozoans causing often fatal diseases in r uminants. Theileria sporozoites immortalize and transform host cells of hae matopoietic origin. Transformation is associated with profound functional a lterations. 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 an d a T. parva-transfomed cell line was investigated, using molecular probes specific for the members of the IFN-alpha, IFN-beta, IFN-gamma and IFN-omeg a family. T. parva-transformed cells produced IFN-gamma exclusively, wherea s T. annulata-infected cells expressed type I IFN only. Analysis of mRNA ex pression showed that this type I IFN was confined to IFN-beta, regardless o f the cellular origin of the transformed cells. When cells were exposed to double-stranded RNA (poly (I:C)) which induces IFN production in other syst ems, a 10-5,000 fold increase in IFN activity was noted. The amounts of IFN -beta mRNA were inceased, but mRNA coding for IFN-alpha, IFN-omega or IFN-g amma was not detected. In contrast, primary macrophages, from which many of the tested lines were derived, expressed IFN-alpha, IFN-beta and IFN-omega mRNA to similar degrees when stimulated by LPS or poly (I:C). Thus, T. ann ulata appears to constitutively tur on IFN-beta gene transcription while si lencing the genes coding for IFN-alpha and IFN-omega.