ICTV Virus Taxonomy Profile: Paramyxoviridae

1Virions are enveloped, pleomorphic, but probably mostly spherical (Table 1, Fig. 1), with a ribonucleoprotein (RNP) core containing the RNA genome protected by a helical nucleocapsid protein (N), the polymerase-associated protein (P) and the large protein (L, including RNA-directed RNA polymerase, capping and cap methylation activities). The envelope contains two glycoproteins with receptor attachment [receptor-binding protein (RBP), designated variably as haemagglutinin–neuraminidase protein (HN), haemagglutinin (H) or glycoprotein (G)] and fusion (F) functions.

2Virus genomes range from 14 296–20 148 nt, but all have a canonical gene arrangement of: 3′-N-P/V/C-M-F-RBP-L-5′ (Fig. 2). In some members this is interspersed with additional transcription units (ATUs).

3Transcription of the negative-sense genome occurs in the cytoplasm and starts with the binding of the P/L protein complex to the transcription promoter at the 3′-end of the RNA, and transcription of 6–8 mRNAs that are capped and poly-adenylated. N-co-terminal V and P proteins encoded by alternative reading frames in the second transcribed gene are accessed by co-transcriptional insertion of non-templated G residues. The C protein is encoded in an overlapping reading frame in the V/P mRNA of most paramyxoviruses, with the exception of members of the subfamilies Avulavirinae, Rubulavirinae, Metaparamyxovirinae and the genus Ferlavirus. During replication, the negative-sense ribonucleoprotein (RNP) template is copied into a full-length encapsidated positive-sense RNA. Negative-sense RNPs are transported to the cellular surface, where budding occurs through interaction of the matrix (or membrane, M) protein with the RNP and the cytoplasmic tails of the two glycoproteins: the fusion protein (F) and the attachment protein (RBP).

4Subfamilies are defined by phylogenetic analysis of the L protein, and are consistent with previous classifications based on host range, biological or biochemical criteria.

5Members of the genera Orthoavulavirus, Metaavulavirus and Paraavulavirus infect birds. Their RBP has haemagglutinin and neuraminidase activity. Their genomes lack ATUs.

6Many members of the genera Orthoarubulavirus and Pararubulavirus derive from bats. Important human viruses are mumps virus and the respiratory viruses human parainfluenzavirus 2 and 4. The RBP of orthorubulaviruses has both haemagglutinin and neuraminidase activity. Pararubulavirus RBPs probably lack neuraminidase activity and may use a receptor other than sialic acid. Mumps virus and parainfluenza virus 5 have an ATU encoding an SH protein between the F and RBP genes.

7Members of the genera Respirovirus, Aquaparamyxovirus, Henipavirus, Narmovirus, Morbillivirus and Salemvirus lack ATUs. Members of the genus Ferlavirus have an additional ATU (U) between the N and P genes encoding a protein with unknown function. Members of Jeilongvirus have one or two ATUs (encoding SH and/or tM proteins) between the F and RBP genes. Members of the genera Respirovirus, Aquaparamyxovirus, Ferlavirus and possibly Jeilongvirus have a RBP that possesses haemagglutinin and neuraminidase activities. Members of the genera Henipavirus and Morbillivirus (and probably Narmovirus and Salemvirus) have protein receptors.

8The species Synodus synodonvirus has been established based on two sequences found in a triplecross lizardfish. The RBP of Wēnlǐng triplecross lizardfish paramyxovirus probably interacts with a protein receptor.

9Current ICTV Report on the family Paramyxoviridae: ictv.global/report/paramxyoviridae.