TABLE 3 .
Amino acids at key codons in the IAV genome
Host | Virus, subtype, or location |
PB2a | PA-Xb | NAc | M2d |
---|---|---|---|---|---|
Canine | CIV-H1N1 | E627 | Truncated | H275 | N31 |
CIV-H3N2 | E627 | Truncated | H275 | S31 | |
CIV-H3N8 | E627 | Truncated | H275 | S31 | |
Equine | EIV H7N7 | E627 | Complete | H275 | S31 |
EIV H3N8 | E627 | Complete | H275 | S31 | |
Swine | CswH1 | K627 | Complete/Truncated | H275 | S31 |
EAswH1 | E627 | Complete | H275 | N31 | |
TRswH3 | E627 | Truncated | H275 | S31 | |
PDMswH1 | E627 | Truncated | H275 | N31 | |
Human | H1N1 (seasonal) | K627 | Complete | H275 (1918–2006) | S31 |
Y275 (2007–2009) | |||||
H1N1pdm | E627 | Truncated | H275/Y275 | N31 | |
H2N2 | K627 | Complete | H275 | S31 | |
H3N2 | K627 | Complete | H275 | S31 (1968–2002) | |
N31 (2003–2017) | |||||
Avian | Eurasian | E627 | Complete | H275 | S31/N31 |
North American | E627 | Complete | H275 | S31 |
The E627K substitution in the PB2 polymerase protein increases replication efficiency in mammals (35).
PA-X is a fusion protein that modulates host cellular immune responses (63). The protein is encoded by a +1 frameshift open reading frame (ORF), and a synonymous mutation in the PA gene produces a nonsense mutation at PA-X codon 42 (34).
The H274Y substitution (H275Y N1 numbering) in the NA protein is associated with reduced susceptibility to oseltamivir antivirals (64).
The S31N substitution in the M2 ion channel protein is associated with reduced susceptibility to adamantane antivirals (65).