[The antigenic characteristics of the influenza virus subpopulations isolated from a single patient]

Examinations by HI and EIA of influenza A (H3N2) virus isolates of 1985-1990 showed the strains derived from nasopharyngeal washings from patients to present very frequently as phenotypic mixtures of stable virus variants. Immunological analysis with monospecific antibody to hemagglutinin antigenic sites revealed a wide spectrum of antigenic activity based on the degree of relationship with viruses of previous years. By means of the immune pressing with antibody of different specificity the isolated strains could be divided into 2 subpopulations each characterized by the presence of only three antigenic sites. The subpopulations homogeneous by the antigenic composition of hemagglutinin represented the strains with antigenic markers of hemagglutinins of previous variants with drift variants of epidemic nature.