Table 1.
Comparison between avian- and human-like amino acids in the PB2, PA and NP proteins of influenza A viruses
We analysed protein sequences in the ISD and identified 75 host-specific amino acids conserved in human and avian influenza viruses. For this study, we selected 12 amino acids, as described in the text.
| Protein | Amino acid | Isolates* | ||
|---|---|---|---|---|
| Position | Avian-like | Human-like | ||
| PB2 | 9 | D | N | A/Hong Kong/482/97 (H5N1), A/Hong Kong/483/97 (H5N1) |
| 199 | A | S | A/Brevig Misson/1/18 (H1N1), several Hong Kong isolates in 1997 (H5N1) | |
| 368 | R | K | A/Hong Kong/1774/99 (H3N2) | |
| 627 | E | K | Many H5N1 isolates (i.e. A/Hong Kong/483/97, A/Hong Kong/213/03, A/Vietnam/1203/04) | |
| PA | 142 | K | N, E† | A/Hong Kong/156/97 (H5N1)‡, A/Vietnam/1203/04 (H5N1) |
| 421 | S | I | A/Vietnam/1203/04 (H5N1), A/Vietnam/1204/04 (H5N1) | |
| NP | 33 | V | I | A/Brevig Misson/1/18 (H1N1), A/Hong Kong/1774/99 (H3N2), A/Wisconsin/10/98 (H1N1), many 2006 Eurasian isolates (H5N1) |
| 100 | R | V | A/Wisconsin/10/98 (H1N1) | |
| I§ | A/Brevig Misson/1/18 (H1N1) | |||
| 283 | L | P | A/Brevig Misson/1/18 (H1N1), A/Hong Kong/156/97 (H5N1)‡ | |
| 357 | Q | K | A/Brevig Misson/1/18 (H1N1), A/Wisconsin/10/98 (H1N1), A/Thailand/5(KK494)/04 (H5N1) | |
*Human isolates originated from avian viruses possessing a human-like amino acid or those possessing the corresponding gene segment from an avian virus.
†Two H5N1 human isolates (A/Hong Kong/156/97 and A/Vietnam/1203/2004) encode Glu at position 142 of PA, whereas most human influenza viruses possess Asn at this position.
‡A mixed population of avian- and human-like amino acids was observed at positions 142 of PA and 283 of NP for A/HK/156/97 virus in the ISD.
§A/Brevig Misson/1/18 (1918 pandemic) virus encodes Ile at position 100 of NP, whereas most human isolates possess Val at this position.