Antigenic drift of H1N1 influenza a virus in pigs with and without passive immunity

Andres Diaz, Matthew Allerson, Marie Culhane, Srinand Sreevatsan, Montserrat Torremorell

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


Background: The genetic and antigenic characteristics of influenza A viruses (IAV) within and between species change over time due to antigenic shift and drift. Although pigs are known to play a key role in the epidemiology of IAV between species, little is known about the molecular evolution of IAV hemagglutinin (HA) in pigs. Objectives: The aim of this study was to evaluate the HA drift of an H1N1 IAV after infecting weaned pigs with or without maternally derived passive immunity. Methods: Three- to four-week-old piglets born either to vaccinated or unvaccinated sows were contact-infected upon exposure with an IAV-infected pig. Nasal swabs were collected daily from each pig and tested for IAV by RRT-PCR. Full-length HA sequences were obtained directly from positive nasal swabs and compared between groups. Results: Synonymous and non-synonymous mutations were detected in pigs with and without passive immunity. Most of the non-synonymous mutations occurred within the HA1 region of the HA. Changes within HA1 region were only identified in antigenic site B in pigs without passive immunity and in antigenic sites A, B, and D in pigs with passive immunity. However, there was no association between the immune status of the pig and the amino acid substitutions observed. Conclusions: Overall, we demonstrated that amino acid substitutions within antigenic sites can happen in weaned pigs with or without passive immunity shortly after infection.

Original languageEnglish (US)
Pages (from-to)52-60
Number of pages9
JournalInfluenza and other Respiratory Viruses
Issue numberSUPPL.4
StatePublished - Dec 2013


  • Antigenic drift
  • Passive immunity
  • Swine influenza


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