Parainfluenza Viruses


Parainfluenza viruses are enveloped viruses that contain nonsegmented negative‐strand genomic ribonucleic acid (RNA). Replication of these viruses begins with entry by attachment and fusion, followed by genomic transcription and replication. Next, the de novo synthesised viral components are trafficked to assembly sites at the plasma membrane where newly formed virions bud out from the cell. These viruses are respiratory pathogens which act as the causative agents for croup, bronchiolitis and pneumonia. As a group, the parainfluenza viruses are second only to human respiratory syncytial virus as the cause of acute paediatric respiratory tract disease and are responsible for hundreds of thousands of additional U.S. hospitalisations per year. Despite their clinical importance, licensed vaccines or antiviral compounds for prevention or treatment of parainfluenza viruses are not currently available, making understanding the pathogenesis of these viruses critical for antiviral drug and vaccine development.

Key Concepts:

  • Parainfluenza viruses are enveloped, nonsegmented negative‐strand RNA viruses, which cause respiratory infections.

  • The structure of the virion consists of glycoprotein spikes protruding from a lipid envelope under which lies the matrix protein surrounding the viral nucleocapsid, consisting of viral RNA encapsidated by nucleoprotein and associated with the polymerase complex.

  • Specific interactions between the two envelope glycoproteins HN and F are necessary for efficient virus infection.

  • Because the viral genome is negative‐stranded RNA, an intermediate step is required for production of progeny viral genomes.

  • Newly synthesised viral nucleocapsids are transported to the assembly site at the plasma membrane utilising the microtubule network.

  • Pathogenicity of parainfluenza viruses is highly dependent on the anti‐interferon activity of the viral accessory proteins.

  • Infectious virus can be created from a complementary deoxyribonucleic acid (cDNA) clone of the viral RNA genome, which is termed reverse genetics.

  • The development of vaccines against parainfluenza viruses currently include intranasally administered vaccines attenuated by cold‐passage, host range attenuation, chimeric vaccine constructs, or the introduction of attenuating mutations through the use of reverse genetics.

Keywords: paramyxovirus; parainfluenza virus; respiratory tract infections; viral proteins; viral vaccines

Figure 1.

Structure of parainfluenza virus. Diagram of parainfluenza virus (Sendai virus, top left) and its genomic RNA (bottom). Electron micrograph of Sendai virus (top middle) and its helical nucleocapsid (top right).

Figure 2.

Syncytium formation induced by haemagglutinin‐neuraminidase (HN) and fusion (F) proteins. Membrane fusion occurs when HN and F proteins of the homologous viruses (b) but not heterologous viruses (a) are expressed; this finding indicates that specific interaction between HN and F is required for membrane fusion (Bousse et al., ).

Figure 3.

Live cell tracking of viral nucleocapsid movement. Sendai virus nucleocapsid, which contains L protein tagged with eGFP can be visualised in live cells using fluorescence microscopy. These nucleocapsids move along microtubule structures in infected cells. Trafficking of nucleocapsid is shown in the time lapse series of images (b) taken from the boxed area of the infected cells shown in (a). Reproduced from Chambers and Takimoto .



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Further Reading

Chambers R and Takimoto T (2009) Antagonism of innate immunity by paramyxovirus accessory proteins. Viruses 1: 574–593.

Harrison MS, Sakaguchi T and Schmitt AP (2010) Paramyxovirus assembly and budding: building particles that transmit infections. International Journal of Biochemistry and Cell Biology 42: 1416–1429.

Karron RA and Collins PL (2007) Parainfluenza viruses. In: Fields BN, Knipe DM and Howley PM et al. (eds) Fields Virology, 5th ed, pp. 1497–1526. Philadelphia: Lippincott‐Raven.

Lamb RA and Parks GD (2007) Paramyxoviridae: the viruses and their replication. In: Fields BN, Knipe DM and Howley PM et al. (eds) Fields Virology, 5th ed, pp. 1449–1496. Philadelphia: Lippincott‐Raven.

Randall RE and Goodbourn S (2008) Interferons and viruses: an interplay between induction, signalling, antiviral responses and virus countermeasures. Journal of General Virology 89: 1–47.

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Chambers, Raychel, and Takimoto, Toru(Mar 2011) Parainfluenza Viruses. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0001078.pub3]