Table 1.

Frequency of potentially antigenic glycosylation sites in natural H9 isolates

Potential glycosylation site positiona	Mutant(s) in this studyb	Frequencyc
127–129	S127N, T127N	6.8%
131–133	K131N	0.1%
148–150	A150T, L150S	1.5%
188–190	T188N	2.6%
189–191	D189N	0.1%

^aPotential glycosylation sites defined as amino-acid motif N-X-S/T, where X is not P; ^bMutants described in Fig. 1, mutants made in this study shown in bold; ^cTotal frequency of potential glycosylation site at this position, based on full length H9 sequences in the NCBI database as of July 2017