Reassortment

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Process of reassortment using the example of influenza viruses.

In virology, reassortment or reassortment is understood as the mixing or redistribution of genetic information between two similar viruses . Mostly it is a matter of variants or subtypes of a virus species or closely related species within a virus genus. A reassortment is only possible under natural conditions if:

  1. the two virus types multiply in the same infected cell and
  2. their genome consists of several segments.

The first condition can only be fulfilled if both viruses can also infect the same host , since only then can their genomes be located in one cell. Viruses that are not tied to a single host, i.e. have a low host specificity or are often able to adapt to a new host through variants, reassort more frequently because they have more hosts and thus more viruses available for reassortment.

The second condition is only met in some virus families that are characterized by a segmented genome.

Result of a reassortment

Influenza virus A reassortment since 1918

The result of a reassortment is the sudden appearance of a genetically very different variant that contains segments from both virus genomes mixed up. If the reassortment has mixed up the segments for the surface proteins or (in the case of non-enveloped viruses) the capsid proteins of a virus, this also results in a sudden change in the epitopes on the virus surface. As a result of reassortment calls this phenomenon is antigenic shift ( English antigenic shift ).

Reassortments are rather rare in natural biotopes because of the necessary simultaneous infection of a host with two viruses . In most cases, the result of a reassortment is viruses that are unable to replicate, or only to a limited extent, or that produce progeny viruses that no longer recognize the target cell with their new surface proteins and can therefore no longer infect them. The probability of reassortment increases significantly when one or two populations (e.g. humans and pigs or chickens) with different virus variants in large numbers and densities have the possibility of mutual infection.

In the event of a reassortment, major changes in the sequence of the viral genetic information and thus also of the viral proteins encoded from it suddenly take place. As a result, these new variants of the viral proteins are not so well recognized by memory cells of the immune system, and an immune evasion occurs which can undermine herd immunity and thus enable a new epidemic.

Reassortment can be prevented in the laboratory by swapping the packaging signals of at least two segments.

Vertebral virus reassortment

Reassortment in viruses that can infect vertebrates (vertebrates) is only available in the case of RNA viruses, namely in the following families:

Reassortment in non-vertebral viruses

In addition to the virus families mentioned above, there are other families or genera with a segmented genome, which only infect bacteria, plants, fungi or insects (instead of vertebrates, or vertebrates ). A reassortment has also been described for these. These are:

literature

  • David M. Knipe, Peter M. Howley, et al . (Ed.): Fields' Virology. 4th edition. Philadelphia 2001, ISBN 0-7817-1832-5 .
  • JR Gentsch, AR Laird, B. Bielfelt, DD Griffin et al .: Serotype diversity and reassortment between human and animal rotavirus strains: implications for rotavirus vaccine programs. In: The Journal of Infectious Diseases . 192 Suppl 1, September 1, 2005, pp. S146 – S159 (Review)
  • RN Charrel, JJ Lemasson, M. Garbutt, R. Khelifa et al .: New insights into the evolutionary relationships between arenaviruses provided by comparative analysis of small and large segment sequences. In: Virology. 317 (2), December 20, 2003, pp. 191-196.
  • T. Yanase, T. Kato, M. Yamakawa, K. Takayoshi et al .: Genetic characterization of Batai virus indicates a genomic reassortment between orthobunyaviruses in nature. In: Archives of Virology. 151 (11), November 2006, pp. 2253-2260.
  • MI Nelson, L. Simonsen, C. Viboud, MA Miller et al .: Stochastic Processes Are Key Determinants of Short-Term Evolution in Influenza A Virus. In: PLoS Pathog . 2 (12), December 1, 2006, p. E125. PMID 17140286
  • B. Schweiger, L. Bruns, K. Meixenberger: Reassortment between human A (H3N2) viruses is an important evolutionary mechanism. In: Vaccine. 24 (44-46), Nov. 10, 2006, pp. 6683-6690.

See also

Web links

Individual evidence

  1. ^ Q. Gao, P. Palese: Rewiring the RNAs of influenza virus to prevent reassortment. In: Proceedings of the National Academy of Sciences . Volume 106, Number 37, September 2009, pp. 15891-15896, doi: 10.1073 / pnas.0908897106 . PMID 19805230 , PMC 2747214 (free full text).
  2. ↑ SIB: Hordeivirus , on: ViralZone