Late protein which is a part of a large complex required for early virion morphogenesis. This complex participates in the formation of virosomes and the incorporation of virosomal contents into nascent immature virions. A15 is required for the stability and kinase activity of F10 (By similarity). Part of a complex composed of A30, G7, F10 kinase, A15, D2, D3, and J1. Localizes in cytoplasmic virus factories and present in the virion core. Belongs to the chordopoxvirinae A15 family.