Avian metapneumovirus M2:2 protein inhibits replication in Vero cells: Modification facilitates live vaccine development

► Vero cells allow optimal AMPV replication for vaccine development. ► AMPV field strain #8544 is the progenitor of most subtype A live vaccines. ► #8544 grows in Vero cells only after M2:2 protein ablation. ► M2:2 ablation facilitates future subtype A vaccine development.