The V protein of canine distemper virus is required for virus replication in human epithelial cells.

Canine distemper virus (CDV) becomes able to use human receptors through a single amino acid substitution in the H protein. In addition, CDV strains possessing an intact C protein replicate well in human epithelial H358 cells. The present study showed that CDV strain 007Lm, which was isolated from lymph node tissue of a dog with distemper, failed to replicate in H358 cells, although it possessed an intact C protein. Sequence analyses suggested that a cysteine-to-tyrosine substitution at position 267 of the V protein caused this growth defect. Analyses using H358 cells constitutively expressing the CDV V protein showed that the V protein with a cysteine, but not that with a tyrosine, at this position effectively blocked the interferon-stimulated signal transduction pathway, and supported virus replication of 007Lm in H358 cells. Thus, the V protein as well as the C protein appears to be functional and essential for CDV replication in human epithelial cells.