Respiratory syncytial virus (RSV) is the leading cause of respira-tory tract infection in infants and young children.
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 is similar to that of measles virus.
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.
The virus is highly labile; it is easily inactivated by dryness at room temperature and by acid. It is preserved by lyophilization.
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.