Antigenic drift

Source: Wikipedia, the free encyclopedia.
Not to be confused with Antigenic shift or Genetic drift.

Antigenic drift is a kind of genetic variation in viruses, arising from the accumulation of

influenza B
viruses.

(Confusion can arise with two very similar terms,

random mutational changes that do not interfere with the DNA's function and thus that are not seen by natural selection
.)

The

acquired immunity. However, viral genomes are constantly mutating
, producing new forms of these antigens. If one of these new forms of an antigen is sufficiently different from the old antigen, it will no longer bind to the antibodies or immune-cell receptors, allowing the mutant virus to infect people who were immune to the original strain of the virus because of prior infection or vaccination.

In 1940s,

selection pressure to continue over an extended period of time and stronger host immune responses increase selection pressure for development of novel antigens.[5]

In influenza viruses

In the

virions budding out of host cells.[7] Sites recognized on the hemagglutinin and neuraminidase proteins by host immune systems are under constant selective pressure. Antigenic drift allows for evasion of these host immune systems by small mutations in the hemagglutinin and neuraminidase genes that make the protein unrecognizable to pre-existing host immunity.[8] Antigenic drift is this continuous process of genetic and antigenic change among flu strains.[9]

In human populations, immune (vaccinated) individuals exert selective pressure for single point mutations in the hemagglutinin gene that increase receptor

single point mutations that decrease receptor binding avidity.[8] These dynamic selection pressures facilitate the observed rapid evolution in the hemagglutinin gene. Specifically, 18 specific codons in the HA1 domain of the hemagglutinin gene have been identified as undergoing positive selection to change their encoded amino acid.[10] To meet the challenge of antigenic drift, vaccines that confer broad protection against heterovariant strains are needed against seasonal, epidemic and pandemic influenza.[11]

As in all

immunity, and the numbers and locations of these mutations that confer the greatest amount of immune escape has been an important topic of study for over a decade.[12][13][14]

Antigenic drift has been responsible for heavier-than-normal flu seasons in the past, like the outbreak of influenza H3N2 variant A/Fujian/411/2002 in the 2003–2004 flu season. All influenza viruses experience some form of antigenic drift, but it is most pronounced in the influenza A virus.[citation needed]

Antigenic drift should not be confused with antigenic shift, which refers to reassortment of the virus' gene segments. As well, it is different from

random genetic drift, which is an important mechanism in population genetics.[citation needed
]

See also

Notes

  1. ^
    S2CID 46630955
    .
  2. ^
    PMID 15858560
    .
  3. doi:10.1016/S0169-5347(02)02502-8
    .
  4. ISBN 978-0-444-82461-5
    .
  5. PMID 16777717
    .
  6. PMID 19230160
    .
  7. S2CID 221107
    .
  8. ^
    PMID 19900932
    .
  9. ^
    PMID 20542248
    .
  10. S2CID 2836600
    .
  11. PMID 17719149
    .
  12. PMID 10555276
    .
  13. PMID 9223253
    .
  14. S2CID 1258353. Archived from the original
    (PDF) on 2019-03-07.

Further reading

External links
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