What makes pandemic H1N1 tick

Washington, November 17 (ANI): Scientist have come one step closer to understanding why the pandemic H1N1 virus, commonly known as "swine flu," is lower than expected in older adults as it continues to evolve.

Researchers at UT Southwestern Medical Center in California sought to understand why children and young adults were more susceptible to the rising H1N1 strain.

Co-author of the paper, Dr. Richard Scheuermann, a professor of pathology and clinical sciences at UT Southwestern and his collaborators, found that the molecular makeup of the present H1N1 flu strain was markedly different from previous H1N1 strains as well as the normal seasonal flu.

He said: "We hypothesize that older people are somewhat protected because the epitopes present in flu strains before 1957 may be similar to those found in the current H1N1 strain, or at least similar enough that the immune system of the previously infected person recognizes the pathogen and knows to attack.

"Those born more recently have virtually no pre-existing immunity to this pandemic H1N1 strain because they have never been exposed to anything like it."

Dr. Scheuermann and experts from the La Jolla Institute for Allergy and Immunology in La Jolla, Calif., and the University of California San Diego also discovered major genetic differences between the pandemic H1N1 strain and seasonal strains.

Dr. Scheuermann, who is also a member of the Cancer Immunobiology Center at UT Southwestern said: "Normally, older adults are generally more susceptible to pathogens like influenza, however, for the pandemic H1N1 strain this does not seem to be the case.

"The antibody epitopes, which provide protection against disease, for the pandemic H1N1 strain are virtually all different from those present in recent seasonal strains, so young people have no built-in protective mechanisms. We speculate that older adults may have been exposed to viruses in their youth in which the epitopes are more similar."

The study, funded by the National Institutes of Health, appeared in a future issue of Proceedings of the National Academy of Sciences. (ANI)