Orthomyxoviridae

The family Orthomyxoviridae (Greek Myxa: mucus) comprises enveloped viruses with single-stranded RNA of negative polarity as genome. Your RNA genome is distributed over several segments, which is why they are opposed to the Paramyxoviridae not attributed to the order Mononegavirales.

The segmentation of their genome allows the Orthomyxoviridae a high genetic flexibility and adaptability to new host species due to the mixing of the different segments of different subtypes and mutants by the so-called reassortment.

Among the Orthomyxoviridae virus include species that infect mainly by droplet infection, the respiratory system of a host and multiply therein. This applies particularly to the genera of influenza viruses that can cause asymptomatic infections or serious diseases in mammals and birds. Some aquatic hosts of the genus Influenza virus A ( baleen whales ) and Isavirus ( salmon ) are transmitted by contaminated water, direct contact or (for the virus of infectious salmon anemia) due to sea lice. Only the species of the genus Thogotovirus not cause respiratory infections and transmitted by ticks to vertebrates.

Morphology

The virions of Orthomyxoviridae are spherical to irregular and 80-120 nm in size in diameter. Also threadlike ( filamentous ) forms with lengths up to a few microns can be observed. In the lipid-containing viral envelope glycoproteins 1-3 and 1-2 non-glycosylated proteins are embedded. These form 10-14 nm long and 4-6 nm in diameter large visible "spikes" on the surface. Anchored in the shell, however, showing with the major portion to the inside, are so-called matrix proteins that line the space between casing and capsids (matrix area). The virions can be found, depending on the segmentation of the genome of several helical capsids, at one end of each of a plurality of subunits of the viral polymerase proteins (PA, PB1 and PB2 ) are associated. These viral enzymes show different activities depending on the virus species, eg PB1 is the influenza virus endonuclease and additionally, these and belonging to the genus Thogotovirus an RNA polymerase ( transcriptase). The capsids are after release in the cytoplasm by specific nuclear transport ( "nuclear import" ) transported into the nucleus.

The (-) ssRNA genome is linear and segmented; the number of segments varies between genres. Thus, the species of the genera possess influenza virus A, influenza virus B and Isavirus each 8 segments, influenza virus C, and the species Dhori -Virus 7, the species Thogoto virus 6 segments. The size of the segments ranges 874-2396 nt, the total size of the genome from 10.0 to 14.6 kb. Through distribution and synthesis error during virus replication many virions possess shorter, defective RNA pieces or do not have a complete set of segments. This is observed especially in mutations of polymerase subunit PA, which obviously plays a crucial role for the proper packing, and distribution of genome segments.

System

  • Family Orthomyxoviridae
  • Genus Influenza virus A
  • Species Influenza A virus
  • Genus Influenza virus B
  • Species influenza B virus
  • Genus Influenza virus C
  • Species influenza C virus
  • Genus Thogotovirus
  • Species Dhori virus
  • Species Thogoto virus
  • Genus Isavirus
  • Species virus of infectious salmon anemia
624322
de