[Significance of the heterogeneity of an influenza virus population in the cytopathology of influenzal infection].

Separation of the allantoic cultures of influenza A/Hong Kong/68 and A/England/72 viruses on DEAE-Sephadex-A-50 with 1/15 M phosphate buffer solution containing 0.1, 0.5, and 1.0 M NaCl (I, II, and III stages of elution, respectively) produced structurally (in size) and functionally (immunologic properties and invectivity for chick embryos) different subpopulations of influenza virus. When white mice were infected with the virus of the Ist and IInd stages of elution, marked proliferation and desquamation of alveolar cells, their hypertrophy and atypism were observed at 10-30 days, with moderately normal blood supply to the lung tissue. In the lungs of mice infected with virions of the IIIrd elution fraction there was no interstitial reaction and marked hemorrhagic component was observed. Virus persistence up to 6 months in the lungs was observed in mice infected with virus from the Ist and IIIrd elution fractions. The observed differences in the quality of influenza virus populations must be taken into account in evaluations of strain evolution at the expense of certain subpopulations and their implications in manifestations of infection and long-term persistence of virus.