Summary
Pathogens such as influenza and trypanosomes alter surface antigens to evade immunity.
In depth
Antigenic drift: gradual point mutations in influenza HA and NA, requiring annual vaccine updates. Antigenic shift: reassortment of gene segments creates new subtypes causing pandemics. Trypanosomes switch VSG coats from a repertoire of thousands.
Variation allows reinfection. Vaccines may need updating (flu) or target conserved regions (universal flu vaccine research). Pathogens switch surface proteins stochastically.
Key idea: evolution under immune pressure drives antigenic change.
Pathogens vary antigens to escape immunity: trypanosomes switch among about 1000 VSG genes, Plasmodium changes PfEMP1 on infected red cells, Neisseria gonorrhoeae alters pili, and HIV mutates quickly. In influenza, drift occurs within a subtype, and shift produced pandemic strains such as H2N2 (1957) and H1N1 (2009). Sixteen HA and nine NA subtypes exist in birds.
Streptococcus pneumoniae has over 90 capsule serotypes, and vaccines cover the most common ones, with replacement by non-vaccine types a concern. Universal influenza vaccines aim at conserved parts of the virus, such as the HA stalk. Predicting next season's strains is done by WHO surveillance.
Frequently asked questions
What is Antigenic Variation?
Pathogens such as influenza and trypanosomes alter surface antigens to evade immunity.
Which area of biology covers Antigenic Variation, and how advanced is it?
Antigenic Variation is one of the 52 topics in Immunology & Disease. It is rated Advanced, so it suits learners who want specialist depth. Related topics in this area include Vaccines, mRNA Vaccines, Virus Evolution.
Why does Antigenic Variation matter?
Variation explains reinfections and challenges vaccine development.
Can you give an example of Antigenic Variation?
HIV mutates rapidly in each patient.
What should I learn before Antigenic Variation?
Work through the Beginner topics in Immunology & Disease first, such as Immune System, Viruses, Innate Immunity, then return to Antigenic Variation. Advanced topics assume the Intermediate vocabulary.
What topics are related to Antigenic Variation?
The closest topics to Antigenic Variation are Vaccines, mRNA Vaccines, Virus Evolution, Zoonotic Spillover. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Antigenic Variation?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Antigenic Variation. To practise the whole of Immunology & Disease, use the Immunology & Disease quiz.
How is Antigenic Variation different from Vaccines?
Antigenic Variation: Pathogens such as influenza and trypanosomes alter surface antigens to evade immunity. Vaccines: Preparations that train the immune system to recognise a pathogen without causing the disease. Read both side by side and note what each one explains.
How should I study Antigenic Variation step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Vaccines and explain the difference aloud. Finally, take the Immunology & Disease quiz and come back to this page for any question you miss.