Paramyxoviridae

Baltimore Classification

Higher order taxa

Virus; ssRNA negative-strand viruses; Mononegavirales; Paramyxoviridae

Genera

Paramyxovirnae (subfamily)
- Avulavirus
- Henipavirus
- Morbillivirus
- Respirovirus
- Rubulavirus
Pneumovirinae (subfamily)
- Pneumovirus
- Metapneumovirus

Description and Significance

Genome Structure

The paramyxovirus is non-segmented and contains a molecule of linear, negative-sense, single-stranded RNA. Occasionally, virions may also contain a positive-sense, single-stranded copy of the genome. The complete genome is 15200-15900 nucleotides long. The 5'-terminus of the negative-sense strand does not have a covalently attached terminal protein, nor does it have a cap. (source: ICTVdB)

Virion Structure of a Paramyxovirus

Paramyxovirus virions consist of an envelope, a nucleocapsid, and a matrix protein. Virions are large and have a complex construction. They are spherical to pleiomorphic, and can range from 150-200nm in diameter and 1000-10000nm long. The envelope has spike-like projections spaced widely apart and evenly covering the surface. The surface projections are embedded in a lipid bilayer. The nucleocapsid is 600-800nm(-1000nm, depending on the genus), 13-18nm in diameter, and has helical symmetry. (source: ICTVdB)

Reproduction Cycle of a Paramyxovirus in a Host Cell

Paramyxovirus replication is very similar to that of other viruses in this group. The overall strategy of paramyxoviruses is very similar to that of influenza, though unlike influenza, all action in the replication of paramyxoviruses occurs in the cytoplasm.

The virions attach to the surface of a host cell, and the envelope fuses to the plasma membrane. The nucleocapsid is released into the cell. The negative-sense RNA is transcribed into individual messenger RNAs and a positive-sense RNA template, which is used to create negative-sense RNA. Assembly occurs, and new viruses bud from the cell membrane (which is how they become enveloped).

Paramyxoviruses have the ability to cause cell-to-cell fusion, creating large multinucleated cells called syncytia.

(sources: Microbiology @ Leicester, Murray)