[Protein adsorption at the tips from synthetic polymers as the cause of incorrect titer analysis of interferons in antiviral bioassays]. / Proteinadsorption an Tips aus synthetischen Polymeren als Ursache für fehlerhafte Titerbestimmungen von Interferonen im antiviralen Bioassay.

The determination of the biological activity of interferons are carried out on the basis of the inhibition of the cytopathic effect of vesicular stomatitis virus on MDBK cells. Using microtiter-plates and tips made of synthetic polymers incorrect data may be observed due to the adsorption of the protein interferon to the tips and, thus, carryover of activity. The following recommendations may help to avoid this kind of mistakes: 1. Generally changing of the tips, at least for the highest concentrations. 2. Reduction of high initial activities by an appropriate pre-dilution. 3. Addition of the detergent Triton X 100 in concentrations between 50 to 100 mg/l to the dilution media for interferon.

[Sensitivity of different cell lines to interferons: the relative antiviral activity as a function of the interferon subtype]. / Interferonsensitivität verschiedener Zellkulturen: Untersuchungen zur Abhängigkeit der relativen antiviralen Aktivität vom Interferon-Subtyp.

The phenomenon that rHuIFN-alpha1(D) displays an apparently higher antiviral activity when assayed on bovine cells as compared to human cell lines was applied to the elucidation of the nature of recombinant HuIFN prepared in our institute. These investigations were carried out by using a microtitre test, which defines biological activity as the IFN concentration leading to 50% inhibition of the cytopathic effect of vesicular stomatitis virus (VSV). In addition, the ability of IFN to diminish the reproduction of infectious viruses was monitored. The two methods yielded similar results. With bovine cells, antiviral activities of the same order of magnitude were observed, regardless of the interferon types applied, i.e. rHuIFN-alpha 1, rHuIFN-alpha 2 and human leukocyte interferon. On human fibroblasts, however, rHuIFN-alpha 1 had an apparently 45 to 165 times lower activity than the other two interferons. On human WISH cells, the differences in apparent activity between the respective IFNs were even greater, with factors of up to 212 fold being observed. Still more distinctive were the effects on murine L 929 cells where an antiviral effect could be confirmed only for rHuIFN-alpha 1 whereas the other two interferons proved completely inactive.