Infectivity of influenza viruses for an organ culture of human embryonic trachea and the change in this trait in recombination

The infecting and reproduction activity of epidemic and vaccine strains of influenza virus as well as their recombinants was studied in human embryo trachea culture. At a certain combination of genes the recombinants showed new qualities: increased tropism to cells of the human upper respiratory tract and intensified virus reproduction in these cells. Of special interest was a recombinant containing the inner proteins of A/Leningrad/9/46 (H0N1) virus and external proteins of A/Brazil/11/78 (H1N1) virus. A possible association of the genes of the internal proteins of influenza A/Leningrad/9/46 virus with the intensity of reproduction, and of the genes of surface glycoproteins with the species specificity of this recombinant is discussed.