[Manifestations of influenza-virus variability during its cultivation in the system of passively immunized chick embryos].

A method of immunological actions on the influenza virus in the system of chick embryos passively immunized with isologous sera was elaborated. With the aid of the suggested method it was possible to induce in strains (with different hemagglutinin type and different degree of attenuation) the transformation of signs characterizing the virus variability in the epidemic process. Variants of the vaccine strains of the influenza virus with increased immunogenic activity and signs of antigenic "outrunning" were obtained. Experimental vaccines from these variants were nonreactogenic for humans and caused a more frequent seroconversion than the initial strain. The diagnostic agents from the variants revealed antibodies in human sera and gamma-globulin, similarly to the "new" viruses isolated from man. The theoretical significance and the aspects of practical utilization of the data obtained are discussed.