Identification of Low- and High-Impact Hemagglutinin Amino Acid Substitutions That Drive Antigenic Drift of Influenza A(H1N1) Viruses
Fig 3
Observed and predicted antigenic impact of amino acid substitutions.
The mean antigenic impact of each substitution predicted from modeling (Table 1) plotted against the mean observed impact averaged across antisera in the panel (S3 Table). 95% confidence intervals are shown for both. Each point shows the observed mean antigenic impact (ΔHA, change in HI titer for a recombinant virus relative to its parent virus) of a particular amino acid substitution (labeled at top) with each antiserum in the panel. Red points indicate that the reference virus lacked the amino acid substitution, so the predicted impact of mutation is a reduction in titer; blue points indicate that the reference virus shared the substitution, so the predicted impact of mutation is an increase in titer. The number of points for each substitution is dependent on whether it was inserted into one or both (Neth93 and Neth93 Δ130) parental viruses and on the number of antisera used. A negative observed antigenic impact indicates a change in HI titer in the opposite direction to that predicted. Mean titers used to calculate antigenic and non-antigenic effects of substitutions are shown in S4 Table and as a heat-map in S2 Fig.