Structural analysis of antigenic variation and adaptive evolution of the H5N1 neuraminidase gene
Fig 3
Phylogenetic reconstruction of nine influenza A neuraminidase subtypes.
This unrooted phylogenetic tree reconstructs the evolutionary relationships among 645 neuraminidase homologs, representing the nine major influenza A virus (IAV) NA subtypes (N1-N9). Inferred using PhyML + SMS version 3.0 based on the comprehensive structure-guided alignment (as detailed in Fig 1) with SH-like aLRT branch support, the tree distinctly groups the NA subtypes into their nine established clades. These clades further cluster into two broad phylogenetic groups: Group 1 (N1, N4, N5, N8) and Group 2 (N2, N3, N6, N7, N9). Notably, a distinct node representing Neuraminidase from Influenza B virus is positioned between these two major Influenza A groups, reflecting its evolutionary divergence. Each NA subtype is visually differentiated by uniquely colored eclipse-shaped nodes.