Comparative study of some characteristics of influenza virus A/PR8/34 (H1N1) cultivated on chorioallantoic membrane fragments in the presence of ceruloplasmin or of parainfluenza type I (Sendai) virus

Multiplication of influenza virus A/PR8/34 (H1N1) in the presence of either ceruloplasmin or parainfluenza type I (Sendai) virus results in the appearance of progens different from the parental virus as regards some of their biological properties. The role of viral envelope changes in acquiring new characteristics is discussed.