Full text loading...
Chapter 36 : Respiratory Syncytial Virus, Human Metapneumovirus, and Parainfluenza Viruses
Ebook: Choose a downloadable PDF or ePub file. Chapter is a downloadable PDF file. File must be downloaded within 48 hours of purchase
Respiratory syncytial virus (RSV), human metapneumovirus (hMPV) and the parainfluenza viruses (PIVs) are the most important causes of lower respiratory tract illnesses in infants and children. RSV comprises of two heterotypic strains of viruses that are antigenically distinct, classified as subgroups A and B. The major difference between these subgroups is the antigenic properties of the G surface glycoprotein protein. Immune responses to the two PIV surface glycoproteins, hemagglutininneuraminidase (HN) and fusion (F), also appear to correlate with protection against infection. Importantly, respiratory diseases remain the most significant cause of mortality in young children worldwide, with an estimated 3 million to 4 million children under 5 years of age dying annually. RSV, PIV, and hMPV are the most important causes of lower respiratory tract disease in children. All these viruses spread primarily from cell to cell in the upper respiratory tract and at times progress to the lower respiratory tract. The inoculum size is an important variable for achieving RSV and PIV infections in adults and possibly infants and children. In lung transplant recipients infected with hMPV, both acute and organizing lung injury occur, with diffuse alveolar damage and cytoplasmic inclusion bodies. The majority of children infected with hMPV can be managed at home with supportive care. For infants and children who require hospitalization, therapy is supportive, including supplementary oxygen and intravenous hydration.
Schematic presentation of the structure of viruses of the family Paramyxoviridae, including PIVs and RSV. L, large protein of the polymerase complex; NP or N, nucleoprotein; P, phosphoprotein. HN is an attachment protein for PIV, and G protein is an attachment protein for RSV.
Schematic presentation of the genomes of PIV type 3 and RSV. Abbreviations: NP, nucleoprotein; P+C, small proteins of the polymerase complex; M, matrix; F, fusion; HN, hemagglutinin-neuraminidase; L, large protein of the polymerase complex; NS, nonstructural proteins; N, nucleoprotein; P, phosphoprotein; SH, strongly hydrophobic protein; G, attachment protein; M2, small envelope protein. (Data from references 41a and 42 .)
Schematic presentation of the replication strategy of viruses of the family Paramyxoviridae. (–), negative sense; (+), positive sense. (Data from reference 150 .)
Characteristic histopathological changes of the airways of an infant with bronchiolitis due to RSV infection. Note the peribronchial mononuclear cell inflammation, relatively normal alveoli, and focal ulceration on top with regenerative epithelial changes. Hematoxylin and eosin stain; magnification, ×45.
Histopathological features of resolving RSV bronchiolitis in an infant. Note the plug of mucus and cellular debris in a terminal respiratory bronchus. Hematoxylin and eosin stain; magnification, ×144.
Histopathology in an infant with congenital immunodeficiency and RSV pneumonia. Note the plugging of a terminal bronchus by cellular debris and parenchymal infiltration with necrosis. Hematoxylin and eosin stain; magnification, ×72.
Chest radiograph of an infant with bronchiolitis due to RSV. Peribronchial thickening with hyperaeration and flattened diaphragms bilaterally are evident. (Reprinted from reference 139 with permission of Elsevier.)
Posterior-anterior (A) and lateral (B) chest radiographs of an infant with bronchiolitis and pneumonia due to RSV. Bilateral perihilar and peribronchial infiltrations and partial or segmental atelectasis of the right middle and right upper lobes are evident. (Reprinted from reference 139 with permission of Elsevier.)
Chest radiograph of a child with croup due to PIV type 1. Peribronchial thickening, scattered infiltrates, and marked narrowing of the superior portion of the trachea (arrow) are evident.
Chest radiograph of an infant with pneumonia due to PIV type 3. Right upper lobe atelectasis and multilobar infiltrates are evident.
Chest radiographs of a 6-month-old infant with bronchiolitis due to hMPV. Peribronchial thickening and hyperinflation are evident.
Cytopathic effect of RSV in cell culture on a continuous human epithelial cell line (HEp-2 cells) after 1 week of incubation. Large syncytial cells are evident, with ballooning and coalescence of RSV-infected cells.
(Left) Cytopathic effect of hMPV in cell culture on a continuous monkey kidney epithelial cell line (LLC-MK2 cells) after 14 days of incubation. (Right) Rounding up and detachment of cells are evident, with developing syncytia.