Interfering activity of epidemic, attenuated and recombinant strains of influenza A virus.

Interfering activity (IA) of the epidemic and attenuated influenza virus strains of different ts-phenotype was studied. IA was assessed by inhibition of vaccinia virus cytopathic effect in chick embryo chorioallantoic membrane (CAM) cells. Direct relationship was established between the temperature sensitivity (ts) index and IA of these viruses. The relationship between IA and multiplicity of infection was strain-specific.