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Immune System of Healthy Adults May Be Better Prepared Than Expected to Fight 2009 H1N1 Flu Virus (2009)

A study team led by the La Jolla Institute for Allergy and Immunology, which included a researcher at the University of Texas Southwestern, looked at molecular similarities between the 2009 H1N1 influenza virus and other strains of seasonal H1N1 virus that have been circulating in the population since 1988. Their findings suggest that healthy people may have immune memory that recognizes the 2009 H1N1 strain and therefore can mount some measure of an immune attack.

The researchers studied epitopes—molecular structures known to be recognized by the immune system—on 2009 H1N1 influenza and seasonal H1N1 viruses. Analysis of scientific data input into the NIAID-supported Immune Epitope Database and Analysis Resource found that some viral epitopes are identical in both the 2009 and seasonal H1N1 viral strains.

Viral epitopes are recognized by immune cells called B and T cells: B cells make antibodies that can bind to viruses, blocking infection, and T cells help to eliminate virus-infected cells. This study showed that epitopes that could be recognized by two subsets of T cells, called CD4 and CD8 T cells, are 41 percent and 69 percent identical, respectively. Subsequent experiments using blood samples taken from healthy adults suggested that this level of T-cell epitope conservation may provide some protection and lessen flu severity in healthy adults infected with the 2009 H1N1 influenza virus.


J Greenbaum et al. Pre-existing immunity against swine-origin H1N1 influenza viruses in the general human population. Proc Natl Acad Sci. DOI: 10.1073/PNAS.0911580106 (2009).

Visit the Immune Epitope Database and Analysis Resource.

Last Updated March 06, 2013

Last Reviewed March 06, 2013