Antigen distortion allows influenza virus to escape neutralization

The structure of the hemagglutinin (HA) of a mutant influenza virus that escapes neutralization by a monoclonal antibody shows that the mutation causes changes in HA structure which avoid an energetically less favorable conformation. However, the structure of the mutant HA·Fab complex indicates that the antibody binds selectively to mutant HA in a wild type-like distorted conformation. The association of an antibody with a less favored HA conformation represents an alternative to previously described mechanisms of escape from neutralization by antibodies.