CHARACTERISTICS OF ANTIGENIC AND BIOLOGICAL PROPERTIES OF INFLUENZA-A VIRUSES ISOLATED DURING DIFFERENT EPIDEMICS OF SAME CYCLE

  • 1 January 1975
    • journal article
    • research article
    • Vol. B126  (4) , 461-470
Abstract
The antigenic character of the hemagglutinin and neuraminidase from Myxovirus influenzae strains isolated in the USSR during the 1968, 1970, 1971-1972 and 1972-1973 epidemics was studied. The hemagglutinins were at first relatively homogenous and constant, but subsequently newer isolates became less reactive against a specific serum prepared with A/HongKong/68. This drift up to 1972-1973 did not go beyond the limits of the H3 subtype. There were some differences in biological properties between earlier and later hemagglutinins, especially with respect to their sensitivity to .gamma.-inhibitor in animal sera, and to their pattern of thermoinactivation at 56.degree. C. Antigenic drift was similar in the case of neuraminidase and more pronounced than with hemagglutinin; the 1972-1973 isolates lost virtually all cross reactivity against the 1957-1969 strains. Three neuraminidase variants were distinguished: N2-1 from H2 sub-type isolates since 1957, N2-2 from 1964-1971 isolates and N2-3 from strains from 1972 on. Certain virus strains such as England/42/72 and some Leningrad/72, had neuraminidases intermediate between N2-2 and N2-3. The in vitro thermostability of these neuraminidases varied among the strains. The explosive nature of the 1972-1973 epidemic was linked to the changes in the virus neuraminidase, which were more pronounced than the changes in the hemagglutinin.