Morphology

• Single-stranded negative-sense unsegmented RNA virus
• Reassortment and antigenic shift cannot occur
• Spike proteins include
  • HN (Haemagglutinin and Neuraminidase)
  • F (Fusion glycoprotein), which allows the virus to fuse directly to the plasma membrane and release its RNA
    • F also causes syncitium to form, which aids diagnosis
    • Host antibody response to the F protein is the basis for vaccination

Virulence

• Paramyxoviruses replicate in the epithelium of the upper respiratory tract as well as occasionally in the gut
  • Sites of spike protein cleavage
• Virulence varies by virus, see below

Types and Subtypes

Paramoyxoviridae was reclassified in 2000 to include 2 subfamilies and 5 genera, of interest including:

• Subfamily: Paramyxovirinae:

• Subfamily: Pneumovirinae

Antigenic Variation

• Antigenic conservation allows some cross protection by vaccination:
  • Conservation of major virus-specific F/HN antigens means vaccines protect against all isolates of the same virus
  • Minor morbillivirus-specific epitopes on F allows some cross protection between canine distemper, measles, and rinderpest
• Antigenic "fingerprinting" is possible for some viruses based on minor variable epitopes of HN, F and NP on specific isolates as detected by monoclonal antibodies
  • These are detected by immunostaining infected cells

Other resources

• On line Paramyxoviridae lecture by P. Russell