Fig. 1. Impact of mutation at published mAb escape sites on haemagglutination inhibition titres performed with polyclonal chicken antisera.

Change in log₂ HI titre associated with stated amino-acid replacements, based on eight individual anti-UDL1/08 antisera with a minimum of five technical repeats, are indicated by cell colouring according to the colour legend with non-significant differences shown in grey and untested substitutions in white. Published mAb escape mutations are shown to the left of centre, whereas alternative substitutions are shown to the right. Mutations that introduce absent or almost absent amino-acid states ( < 1% of sequenced natural isolates) are labelled in smaller, italicised, grey font. * addition of potential glycosylation site. ^† would not rescue. ^‡ Q146H rescued with additional substitution T186K