Figure 3.

Unrooted neighbor-joining tree showing the phylogenetic relationships between 26 FMDV serotype A, O, C, and Asia 1 strains. In total, 21 strains were assayed for VHH binding by DAS-ELISA, whereas five additional vaccine strains (gray dots) were added to guarantee the tree covers the most important lineages of vaccine strains according to the reports of OIE and FAO [32,33]. VP1 nucleotide sequences were used to generate the tree, with database accession numbers indicated after strain names. The evolutionary distances were computed using the Kimura-2 parameter model, and 500 replicates for bootstrap in MEGA-X. Colors indicate the lineage of the serotype A strain (green), topotype (blue), and serotype (purple).