Table 3.

Experimentally verified molecular markers/motifs in the polymerase basic protein 2 (PB2; segment 1) gene of avian influenza virus associated with polymerase activity, virulence, and transmissibility

Mutation/motif	Phenotype	Subtypes tested	References
D9Na	Increased virulence in mice	H5N1	[115, 116]
V25A	Increased virulence in mice	H5N1 backbone with H1N1 NS	[267]
I63T	Decreased pathogenicity in mice	H5N1	[72]
E158G	Increased polymerase activity in mammalian cell line, increased virulence in mice	H5N2	[268]
		H5N9	[268]
E158K	Increased polymerase activity and replication in mammalian cell line, increase virulence in mice	H4N6	[269]
E192K	Increased polymerase activity in mammalian and avian cell line, increased virulence in mice	H5N1	[117]
A199S	Increased virulence in mice	H5N1	[116]
D253N	Increased polymerase activity in mammalian cell line	H9N2	[270]
D256G	Increased polymerase activity in mammalian cell line	H5N1 backbone with pH1N1 PB2	[271]
T271A	Increase polymerase activity in avian and mammalian cell line	H3N2 (avian)	[272]
		H5N1	[273]
		H7N9	[274]
I292V	Increased polymerase activity in mammalian cell line, increased virulence in mice	H9N2	[275]
	Increased polymerase activity in mammalian cell line	H10N8	[276]
E358V	Decreased virulence in mice	H7N3	[277]
K389R	Increased polymerase activity and replication in mammalian cell line	H7N9	[278]
L339T	Decreased polymerase activity and decreased virulence in mice	H5N1	[279]
K482R	Increased polymerase activity in mammalian cell line	H7N9	[280, 281]
K526R	Increased polymerase activity in mammalian cell line	H5N1	[282]
		H7N9	[282]
M535L	Increased polymerase activity in mammalian cell line	H7N9	[25]
A588V	Increased polymerase activity and replication in mammalian and avian cell lines, increased virulence in mice	H7N9	[276]
		H9N2	[276]
		H10N8	[276]
Q591K	Increased polymerase activity in mammalian and avian cell line, increased replication in mammalian cell line, increased virulence in mice	H5N1	[117, 283]
	Increased polymerase activity in mammalian and avian cell lines	H7N9	[25, 274]
	Increased polymerase activity and replication in mammalian cell line, increased virulence in mice	H9N2	[284]
V598T/I	Increased polymerase activity and replication in mammalian cells, increased virulence in mice	H7N9	[278]
E627K	Increased polymerase activity and replication in mammalian cell line, increase virulence in mice	H4N6	[269]
	Enhanced polymerase activity, increased virulence in mice, contributes to airborne pathogenicity of IAVs in ferrets and contact transmission in guinea pigs. Decreases polymerase activity and replication in avian cell lines. Decreases virulence in chickens.	H5N1	[15, 100, 101, 106–108, 116, 257, 271, 285–289]
	Increased polymerase activity in mammalian cell line, increased virulence in mice	H6N1	[103]
	Increased polymerase activity in mammalian cell lines, increase virulence in mice	H7N7	[102, 104]
	Increased polymerase activity and replication in mammalian cell lines, increased virulence in mice	H7N9	[102, 105]
	Increased polymerase activity in mammalian cell line, increased virulence in mice	H9N2	[102, 290]
E627V	Increased polymerase activity and replication in mammalian cell lines, increased virulence in mice	H5N1	[117]
K627E	Increased virulence in chickens	H5N1	[291]
D701N	Increased viral replication in mammalian cells and virulence in mice	H1N2	[220]
	Increased polymerase activity, enhanced replication efficiency, increased virulence and contact transmission in guinea pigs, increased virulence in mice	H5N1	[96, 117, 206, 292, 293]
	Increased polymerase activity in mammalian cell line	H7N9	[25, 274]
	Increased polymerase activity in mammalian cell line	H9N2	[102]
D701V	Increased polymerase activity and replication in mammalian cell lines, increased virulence in mice	H5N1	[117]
S714R	Increased polymerase activity and replication in mammalian cell line	H7N7	[94, 102, 124]
	Increased polymerase activity in mammalian cell line	H9N2	[102]
S715N	Decreased virulence in mice	H5N1	[294]
M28I, A274T, K526R, I553V, L607V	Decreased polymerase activity in mammalian cell line	H5N1	[295]
L89V, G309D	Increased polymerase activity in mammalian cell line and increased virulence in mice	H5N1	[296]
L89V, G309D, T339K, R477G, I495V, K627E, A676T	Increased polymerase activity in mammalian cell line and increased virulence in mice	H5N1	[296]
M147L, E627K	Increased polymerase activity in mammalian cell line and virulence in mice	H9N2	[297]
I147T, K339T, A588T	Increased polymerase activity in mammalian cell line and virulence in mice	H5N1	[298]
K526R, E627K	Increased polymerase activity and viral replication in mammalian cell lines, increased virulence in mice	H5N1	[282]
		H7N9	[282]
E627K, D701N	Increased polymerase activity in mammalian cell line	H7N9	[299]
E627K, S714R	Increased polymerase activity in mammalian cell lines	H7N7	[102]
		H7N9	[102]
		H9N2	[102]
E627K, D701N, S714R	Increased polymerase activity in mammalian cells, increased virulence in mice	H9N2	[102]
D701N, S714R	Increased polymerase activity in mammalian cell line, increased virulence in mice	H5N1	[300]
	Increased polymerase activity in mammalian cell lines	H7N7	[102]
	Increased polymerase activity in mammalian cell lines	H7N9	[102]
	Increased polymerase activity in mammalian cell lines	H9N2	[102]
E627K (with HA: H110Y, T160A, Q226L, G228S; PB1: H99Y)	Enable airborne transmissibility between ferrets and contact transmission between guinea pigs	H5N1	[15, 58]

Single mutations are presented first followed by motifs involving multiple mutations. Individual markers and motifs are listed in numerical order for ease of identifying mutation of interest

^aMutations/motifs are numbered according to alignments with A/Goose/Guangdong/1/1996 (H5N1)