Table 2.

Amino Acid Substitutions Introduced Into the Recombinant Neuraminidase (NA) Proteins of Influenza A/Shanghai/2/2013(H7N9) Virus

NA Residuea			Amino Acidb	Amino Acid Change	Functionc	RI/HRIe Reported in	Nucleotide Change in A/Shanghai/2/2013 NA
N2	Avian N9	N9 (H7N9)
119	120	115	E	A	FW	N1, N2, B	GAA → GCA
…	…	…	…	D	…	N1, N2, N7, B	GAA → GAU
…	…	…	…	G	…	N1, N2, N3, N7, N9, B	GAA → GGA
…	…	…	…	V	…	N1, N2, N7, N9, N9 (2013), B	GAA → GUA
136	137	132	Q	K	-	N1f, N2, N9	CAA → AAA
152	153	148	R	K	Cat	B, N9	AGG → AAG
222	224	219	I	K	FW	N1, N9 (2013)	AUA → AAA
…	…	…	…	R	…	N1, N9 (2013)	AUA → AGA
247	249	244	S(T)g	P	-	N2v	ACU → CCU
274	276	271	H	Y	FW	N1, N3, N9, B	CAU → UAU
276	278	273	E	D	Cat	N2, N7	GAA → GAC
292	294	289	R	K	Cat	N2, N3, N6, N7, N9, N9 (2013)	AGG → AAG
294	296	291	N	S	-	N1, N2, B	AAU → AGU
371	372	367	R	K	Cat	N2, B	AGG → AAG

Abbreviations: Cat, catalytic residue; FW, framework residue; −, nonactive site/unspecified.

^aAmino acid position in the NA that is known or suspected to adversely affect susceptibility to NA inhibitor(s). N2, avian N9, and 2013 N9-specific numbering schemes were used.

^bAmino acid at the indicated residue of the NA gene of A/Victoria/361/2001(H3N2), A/Shanghai/2/2013(H7N9), and A/tern/Australia/G70C/1975(H11N9).

^cThe function of the NA residue is based on findings by Colman et al [16].

^dCompared with the NA sequence of A/Shanghai/2/2013(H7N9) virus. The difference is shown in bold.

^eReduced (RI) or highly reduced inhibition (HRI) were determined using the NA inhibition assay. See also Table 4.

^fWas shown to be host-cell selected.

^gSerine is a highly conserved amino acid residue in A(H3N2) viruses, whereas tyrosine is predominant in avian N9 viruses.