Analysis of Antigenic Drift in the Haemagglutinin Molecule of Influenza B Virus with Monoclonal Antibodies

Abstract

Antigenic drift in the hemagglutinin (HA) molecule of influenza B viruses was studied with monoclonal antibodies. Antigenic drift occurred in each of the 12 different epitopes studied and there was evidence that at least 2 antigenically distinguishable influenza B virus strains can co-circulate during an epidemic. The frequency of antigenic variation in the HA of influenza B viruses was frequently < 1 in 108 and was .apprx. 1000-fold below that found in influenza A strains. Hemagglutination inhibition (HI) tests on antigenic variants selected with 12 different monoclonal antibodies suggested that the antigenic determinants could be subdivided into 3 partially overlapping groups. Many of the antigenic variants selected with monoclonal antibodies were distinguishable from the parental virus with post-infection ferret sera, suggesting that the majority of the variants that do occur could have epidemiological potential.