[Comparative study of the RNA-polymerase activity of non-pathogenic and pathogenic influenza viruses A and B]

Activity of RNA polymerase was studied in original non-pathogenic for mice viruses of influenza A and B (A/seal/Massachusetts 1/80, A/USSR 05/81, A/Philippines 2/82 and B/Singapore 227/79) and of their pathogenic derivatives. All the non-pathogenic viruses studied exhibited the low rate of transcriptase activity. Pathogenic derivatives of these strains exhibited higher activity of RNA polymerase, which was 1.5-3-fold higher as compared with the original strain. During passage of influenza viruses A and B in mice organism selection of the population appears to occur, which had the highest transcriptase activity.