Respiratory Syncytial: Properties of the Virus

Respiratory Syncytial

Respiratory syncytial virus (RSV) is the leading cause of respira-tory tract infection in infants and young children.

Properties of the Virus

◗ Morphology

Respiratory syncitial virus shows following features:Virus

·           It is pleomorphic and measures from 150 to 300 nm in size.

·           It has a small nucleocapsid, measuring 13 nm in diameter, unlike large nucleocapsid (18 nm) of other paramyxoviruses.

·           The viral envelope contains a surface glycoprotein G, by which it is attached to the cell surface of the host cells. It contains F protein but lacks both H and N proteins.

·           The F protein induces the fusion of the infected cells with adjoining cells, resulting in the formation of large multinu-cleated syncytia, from which the virus derives its name.

Differences between morphology of RSV and other paramyxo-viruses are summarized in Table 61-1.

◗ Viral replication

Viral replication is similar to that of measles virus.

◗ Antigenic and genomic properties

The virus is antigenically stable. It has only one antigenic sero-type with the subtypes A and B. Subtype A appears to be more virulent than the subtype B.

◗ Other properties

The virus is highly labile; it is easily inactivated by dryness at room temperature and by acid. It is preserved by lyophilization.

Virus Isolation

◗ Cell culture

Respiratory syncytial virus is difficult to grow in cell culture in PMK or in human cell (HeLa cells, Hep-2) lines. Formation of large multinucleated syncytia is the characteristic CPE produced by the virus, but slowly in 2–10 days.