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Since the 2009 pandemic H1N1 swine-origin influenza A virus (09 S-OIV) has reminded the world about the global threat of the ever changing influenza virus,many questions regarding the detailed re-assortment of influenza viruses yet remain unanswered.Influenza A virus is the causative agent of the pandemic flu and contains 2 major antigenic glycoproteins on its surface:(i) hemagglutinin (HA);and (ii) neuraminidase (NA).The structures of the 09 S-OIV HA and NA proteins (09H1 and 09N1) have recently been resolved in our laboratory and provide some clues as to why the 09 S-OIV re-assortment virus is highly infectious with severe consequences in humans.For example,the 09H1 is highly similar to the HA of the 1918 influenza A pandemic virus in overall structure and especially in regards to its 5 defined antibody binding epitopes.For 09N1,its most distinctive feature is the lack of a 150-loop active site cavity,which was previously predicted to be present in all N1 NAs,and we hypothesize that the 150-loop may play a important role in the substrate specificity (α2,3 or α2,6 linked sialic acid receptors) and enzymatic mechanism of influenza NA.Combination of the HA and NA with special characteristics for the 09 S-OIV might contribute to its high increased transmissibility in humans.
Since the 2009 pandemic H1N1 swine-origin influenza A virus (09 S-OIV) has reminded the world about the global threat of the ever changing influenza virus, many questions regarding the detailed re-assortment of influenza viruses yet remain unanswered. Influenza A virus is the causative agent of the pandemic flu and contains 2 major antigenic glycoproteins on its surface: (i) hemagglutinin (HA); and (ii) neuraminidase (NA). The structures of the 09 S-OIV HA and NA proteins 09N1) have recently been resolved in our laboratory and provide some clues as to why the 09 S-OIV re-assortment virus is highly infectious with severe consequences in humans. For example, the 09H1 is more similar to the HA of the 1918 influenza A pandemic virus in overall structure and especially in regards to its 5 defined antibody binding epitopes. For 09N1, its most distinctive feature is the lack of a 150-loop active site cavity, which was previously predicted to be present in all N1 NAs, and we hypothesize that the 150-loop may play a significant role in the substrate specificity (α2,3 or α2,6 linked sialic acid receptors) and enzymatic mechanism of influenza NA. Combining the HA and NA with special characteristics for the 09 S-OIV might contribute to its high increased transmissibility in humans.