This family consists of several Borna disease virus P40 proteins. Borna disease (BD) is a persistent viral infection of the central nervous system caused by the single-negative-strand, nonsegmented RNA Borna disease virus (BDV). P40 is known to be a nucleoprotein [1].

1: Borna disease virus nucleoprotein (p40) is a major target for CD8(+)-T-cell-mediated immune response. Planz O, Stitz L; J Virol 1999;73:1715-1718. PMID:9882386