Antigenic variants of influenza viruses: Marked differences in the frequencies of variants selected with different monoclonal antibodies

Abstract

Monoclonal antibodies against the hemagglutinin of two influenza A viruses and one influenza B virus were used to analyze the frequencies of antigenic variant subpopulations in cloned virus seeds. Antigenic variants selected with monoclonal antibodies specific for different antigenic determinants were obtained over a wide range of frequencies. With one monoclonal antibody directed to the hemagglutinin of A/PR/8/34 virus antigenic variants were isolated at a frequency of 10- 4.4, whereas another monoclonal antibody, specific for the hemagglutinin of X-31 virus, completely neutralized all infectious virus in the X-31 virus seeds examined, indicating a frequency of antigenic variation, for one seed at least, of less than 10 −8.1.