A virus that could not be identified as a previously known equine virus was
isolated from the mononuclear cells of a horse. Electron microscopy reveal
ed enveloped virions with nucleocapsid structures characteristic of viruses
in the Paramyxoviridae family. The virus failed to hemadsorb chicken or gu
inea pig red blood cells and lacked neuraminidase activity. Two viral genes
were isolated from a cDNA expression library. Multiple sequence alignments
of one gene indicated an average identity of 45% as compared to Morbillivi
rus N protein sequences. A weaker relationship was found with Tupaia paramy
xovirus (TPMV) and Hendra virus (HeV) N proteins. In the second gene, multi
ple open reading frames (ORFs) were identified, corresponding to the arrang
ement of the P,V, and C ORFs in the Morbillivirus and Respirovirus viruses.
Short stretches in the C-terminal regions of the P and C proteins showed l
imited homologies to viruses in the Morbillivirus genus but no obvious rela
tionship to viruses in other genera. The V ORF translation product containe
d a highly conserved, cysteine-rich domain that is common to most Viruses i
n the Paramyxovirinae subfamily. Sequencing of P gene cDNA clones confirmed
the use of a cotranscriptional editing mechanism for the regulation of P/V
expression. Based on the location of its origin it has been named Salem vi
rus (SalV). (C) 2000 Academic Press.