Improved conditions for the production and detection of interferon from guinea pig embryo cells

Primary guinea pig embryo (GPE) fibroblasts were assessed as potential sources of guinea pig interferon (IFN). GPE cells proved to be excellent in vitro producers of guinea pig IFN, although the actual amounts produced were only detectable when sample irradiation under ultraviolet light (to inactivate inducing viruses) was substituted for overnight sample treatment at pH 2. Thus, the rapid spontaneous inactivation of large proportion of the antiviral activity after overnight exposure to 4 degrees C, regardless of pH, was avoided. IFN was induced using Newcastle disease virus (NDV), Sindbis virus, and a genetic variant of vesicular stomatitis virus, VSV T1026R1. Each virus exhibited different dose response kinetics, with VSV T1026R1 proving the most efficient inducer of the three. Optimal IFN production depended largely on virus multiplicity and cell age. All the antiviral activity produced by GPE fibroblasts had the classical properties of species specificity, susceptibility to trypsin, and a broad range of antiviral activity.