[Interfering and interferonogenic activity of attenuated and original para-influenza viral strains]. / Interferiruiushchaia i interferonogennaia aktivnost' attenuirovannykh i iskhodnykh shtammov virusov paragrippa.

A higher interfering activity of attenuated (vaccine) strains of parainfluenza virus types 1, 2 and 3 which had undergone a long-term adaptation to cell cultures as compared to the original viruses was established. The interferon-inducing activity of vaccine parainfluenza virus types 2 and 3 was also higher than that of the original viruses. The high interfering and interferon-inducing activity of attenuated parainfluenza virus strains of type 2 and 3 correlated with reduced virulence of these variants for man. These tests may be used for the assessment of virulence of parainfluenza virus strains type 2 and 3 in the laboratory.