THURSDAY, Nov. 26 (HealthDay News) -- Swine flu has many immunological similarities to seasonal flu, and the general population has some pre-existing immunity to swine flu, suggesting that swine flu infection may not be as severe as feared, according to a study published online Nov. 16 in the Proceedings of the National Academy of Sciences.

Jason A. Greenbaum, Ph.D., from the La Jolla Institute for Allergy and Immunology in California, and colleagues analyzed the similarity of seasonal and swine influenza immunological epitopes using data from the Immune Epitope Database.

The researchers found that, while only 31 percent of B-cell epitopes were conserved in swine flu, 41 percent of CD4+ T cell epitopes and 69 percent of CD8+ T cell epitopes were conserved. Peripheral blood mononuclear cells from normal adults collected before the current swine flu pandemic responded to CD4+ and CD8+ T cell swine flu epitopes. Further investigation showed that the responding cells were memory T cells, and that the magnitude of the response was similar to memory against seasonal flu.

"Therefore, the conservation of a large fraction of T-cell epitopes suggests that the severity of a swine-origin H1N1 influenza virus infection, as far as it is determined by susceptibility of the virus to immune attack, would not differ much from that of seasonal flu," Greenbaum and colleagues conclude.

Abstract
Full Text