Schwarz, Heike; Harlin, Olof; Ohnemus, Annette; Kaspers, Bernd; Staeheli, Peter
Synthesis of IFN-β by Virus-Infected Chicken Embryo Cells Demonstrated with Specific Antisera and a New Bioassay.
In: Journal of Interferon & Cytokine Research, Vol. 24, No. 3: pp. 179-184
Transcripts of interferon-α(IFN-α) and IFN-β genes are present in virus-infected chicken cells, but because
of a lack of appropriate assays and reagents, it was unclear if biologically active IFN-β is secreted. We have
established a nonviral bioassay for the sensitive detection of chicken IFN (ChIFN). This assay is based on a
quail cell line that carries a luciferase gene that is controlled by the IFN-responsive chicken Mx promoter.
Luciferase activity was strongly stimulated when the indicator cells were incubated with ChIFN-α, ChIFN-β,
or ChIFN-γ but not with chicken interleukin-1β (ChIL-1β). Unlike the classic antiviral assay that preferentially
detects ChIFN-α, the Mx-luciferase assay detected ChIFN-α and ChIFN-β with similar sensitivity.
With the help of this novel assay and with rabbit antisera specific for either IFN-α or IFN-β, we analyzed
the composition of IFN in supernatants of virus-infected chicken embryo cells. Virtually all IFN produced in
response to Newcastle disease virus (NDV) was IFN-α. However, IFN produced in response to influenza A or
vaccinia virus (VV) was a mixture of usually more than 80% IFN-α and up to 20% IFN-β. Thus, IFN-α and
IFN-β both contribute to the cytokine activity in supernatants of virus-infected chicken cells. Furthermore,
the infecting virus appears to determine the IFN subtype composition.