Aspects of a Methodological Approach to Determination of Interferon Alpha Specific Activity

Specific antiviral activity is one of the key indicators characterising pharmaceutical quality and pharmacological efficacy of interferon alpha products (IFN-α). Specific activity is determined using a bioassay measuring antiviral activity in cell culture. The aim of the study was to select the most appropriate conditions for in vitro determination of IFN-α product specific activity. Materials and methods: Vero, MDBK, Hep-2, and A-549 homologous and heterologous cell cultures, as well as vesicular stomatitis Indiana virus (VSV) and murine encephalomyocarditis (EMC) virus at a dose of 100 TCD50 /0.1 mL were used for determination of specific antiviral activity. The international reference standard of recombinant interferon alpha-2b activity (Interferon alpha 2b, human, rDNA, E. coli-derived, 2nd WHO International Standard, 1999, NIBSC Code No. 95/566) and human recombinant interferon alpha 2b in the form of solution (batch No. 040214, Pharmapark LLC, Russia) were used as IFN-α samples. Results: the analysis of the obtained data helped to determine: the combinations of cell lines and the indicator virus most sensitive to IFN-α; the optimal concentration of fetal serum in the medium, and the optimal time parameters; the preferred method of reporting test results. Conclusions: the following test conditions were found to be optimal: the MDBK/VSV and Hep-2/EMC combinations proved to be the most sensitive to IFN-α; the optimal period of interferon and cell culture incubation—24 hours; the optimal concentration of fetal bovine serum in the culture medium used for diluting interferon products—2–5%. The instrumental procedure is preferred for reporting the results of interferon antiviral activity determination, because it is up-to-date, reliable, accurate and time-efficient.