In that outbreak, 46 monkeys died from severe pneumonia during a quarantine period. A CDV strain (CYN07-dV) was isolated in Vero cells expressing dog signaling lymphocyte activation molecule (SLAM). Phylogenic analysis showed that CYN07-dV was closely related to the recent CDV outbreaks in China, suggesting continuing chains of CDV infection in monkeys. In vitro, CYN07-dV uses macaca SLAM and macaca nectin4 as receptors as efficiently as dog SLAM and dog nectin4, respectively. CYN07-dV showed high virulence in experimentally infected cynomolgus monkeys and excreted progeny viruses in oral fluid and feces. These data revealed that some of the CDV strains, like CYN07-dV, have the potential to cause acute systemic infection in monkeys.

Canine distemper virus (CDV) uses signaling lymphocyte activation molecule (SLAM), expressed on immune cells, as a receptor. However, epithelial and neural cells are also affected by CDVin vivo. Wild-type CDV strains showed efficient replication with syncytia in Vero cells expressing dog nectin4, and the infection was blocked by an anti-nectin4 antibody. In dogs with distemper, CDV antigen was preferentially detected in nectin4-positive neurons and epithelial cells, suggesting that nectin4 is an epithelial cell receptor for CDV and also involved in its neurovirulence.

Sendai virus (SeV) encodes two accessory proteins, V and C, in the alternative reading frames in the P gene that are accessed transcriptionally (V) or translationally (C). The C protein is expressed as a nested set of four C-coterminal proteins, C, C, Y1, and Y2, that use different initiation codons. Using HeLa cell lines constitutively expressing the various C proteins, we previously found that the smallest (the 175-residue Y2) of the four C proteins was fully capable of counteracting the antiviral action of interferons (IFNs) and inhibiting viral RNA synthesis and that the C-terminal half of 106 residues was sufficient for both of these inhibitory functions Sendai virus (SeV) is an enveloped virus with a linear, nonsegmented, negative-sense RNA genome of 15,384 nucleotides and belongs to the genus Respirovirus of the subfamily Paramyxovirinae. SeV contains six genes in the order 3Ј-(leader)-N-P-M-F-HN-L-(trailer)-5Ј on the genome. The monocistronic mRNAs are transcribed by the viral RNA polymerase composed of L and P proteins (16). However, the P gene is exceptional in that it gives rise to multiple protein species by a process known as RNA editing and by the use of an overlapping open reading frame (ORF). The P protein is translated from the unedited mRNA, which is the exact copy of the P gene, while the V protein is translated from the edited mRNA, in which one nontemplated G residue is cotranscriptionally inserted to the editing position. The P and V proteins, therefore, have a common N terminus but have different C termini because the reading frame for V changes by ϩ1 relative to the P frame (for a review, see references 33 and 38). The V protein is encoded by almost all viruses that are members of the subfamily Paramyxovirinae. The unique C-terminal region of V contains seven cysteine residues highly conserved among paramyxoviruses, forms zinc finger-like motifs, and, indeed, binds Zn 2ϩ (7,20,35,44,51). The C protein is translated from the Ϫ1 reading frame relative to the frame common to P and V. The SeV P and V proteins are initiated at the AUG codon at position 104, whereas the SeV C reading frame produces a nested set of CЈ, C, Y1, and Y2 proteins initiating, respectively, at a non-AUG (ACG) codon at position 81 and at AUG codons at positions 114, 183, and 201 (4, 15, 45). The CЈ, C, Y1, and Y2 proteins are terminated at the same position 726 and are collectively called C proteins. Among them, the C protein is the major species expressed in infected cells, at a molar ratio severalfold higher than that of the other three proteins (32). The C proteins are expressed by the viruses belonging to three genera, Respirovirus, Morbillivirus, and Henipahvirus, and by Tupaia paramyxovirus-like viruses, but they are not expressed by the viruses belonging to two genera, Rubulavirus and Avulavirus of Paramyxovirinae (reviewed in reference 37). The amino acid sequence of the C proteins is well conserved within each genus

Our laboratory data strongly suggest a relationship between FHI and rubella virus.

Recent outbreaks in monkeys have proven that canine distemper virus (CDV) causes diseases in a wide range of mammals. CDV uses SLAM and nectin4 as receptors to replicate in susceptible animals. Here, we show that human nectin4, but not human SLAM, is fully functional as a CDV receptor. The CDV Ac96I strain hardly replicated in nectin4-expressing human epithelial NCI-H358 cells, but readily adapted to grow in them. Unsurprisingly, no amino acid change in the H protein was required for the adaptation. The original Ac96I strain possessed a truncated C protein, and a subpopulation possessing the intact C protein was selected after growth in NCI-H358 cells. Other CDV strains possessing the intact C protein showed significantly higher growth abilities in NCI-H358 cells than the Ac96I strain with the truncated C protein. These findings suggest that the C protein is functional in human epithelial cells and critical for CDV replication in them.