Table 4.

Amino acids at positions 155, 159, 190, and 225 of the HA of H1 viruses from birds, swine, and humansa

Virus type (no. of sequences analyzed)Amino acid residue at position:
 Avian (13)T* T* E* G*
 Classical swine (22)V* N[19], D[2], S[1]D[21], E[1]G[20], D[1], N[1]
 Avian-like swine (8)V[6], I[2]N* D[7], E[1]G[6], E[2]
 Human (42)T* G* D[33], E[5], N[4]D[22], G[19], N[1]
 Human, 1918 (3)b T* S* D* D[2], G[1]
H2-H15 avian (14)c Variable: T, V, I, LVariable: G, A, S, T, N, Q, DE* G[13], N[1]
  • a The analysis was performed with sequences obtained from the GenBank and from the literature (29,41). An asterisk next to an amino acid indicates that it was conserved in all sequences. Otherwise, the number of sequences for a particular amino acid is given in brackets.

  • b Reid et al. (30).

  • c The analysis was performed with a previously described set of avian virus HA sequences representing each of the 15 HA subtypes (23).