Abstract
Of the eighteen hemagglutinin (HA) subtypes (H1–H18) that have been identified in bats and aquatic birds, many HA subtypes have been structurally characterized. However, several subtypes (H8, H11 and H12) still require characterization. To better understand all of these HA subtypes at the molecular level, HA structures from an A(H4N6) (A/swine/Missouri/A01727926/2015), an A(H8N4) (A/turkey/Ontario/6118/1968), an A(H11N9) (A/duck/Memphis/546/1974), an A(H14N5) A/mallard/Gurjev/263/1982, and an A(H15N9) (A/wedge-tailed shearwater/Western Australia/2576/1979 were determined by X-ray crystallography at 2.2Å, 2.3Å, 2.8Å, 3.0Å and 2.5Å resolution, respectively. The interactions between these viruses and host receptors were studied utilizing glycan-binding analyses with their recombinant HA. The data show that all avian HAs retain their strict binding preference to avian receptors, whereas swine H4 has a weak human receptor binding. The molecular characterization and structural analyses of the HA from these zoonotic influenza viruses not only provide a deeper appreciation and understanding of the structure of all HA subtypes, but also re-iterate why continuous global surveillance is needed.
Highlights
Influenza is an acute respiratory illness, caused by influenza A, B, C and D viruses (Hause et al, 2014; Palese and Shaw, 2007)
While H3, H4 and H6 avian influenza virus (AIV) subtypes are common, H8–H12, H14 and H15 are rarely detected in wild aquatic birds, while H13 and H16 viruses have been isolated mainly from gulls (Wille et al, 2011)
We focus on molecular characterization of HAs from an A(H8N4) (A/turkey/Ontario/6118/1968), an A(H11N9) (A/duck/Memphis/546/1974), an A(H14N5) A/mallard/Gurjev/263/1982, an A(H15N9) (A/wedge-tailed shearwater/Western Australia/2576/1979, and an A(H4N6) A/swine/Missouri/A01727926/2015) (Table 1)
Summary
Influenza is an acute respiratory illness, caused by influenza A, B, C and D viruses (Hause et al, 2014; Palese and Shaw, 2007). While all of these viruses contain segmented, linear, negative-sense, single-stranded RNA genomes (Fields et al, 2007), they differ in the number of RNA segments, with eight for influenza A and B and seven for influenza C and D. While H3, H4 and H6 avian influenza virus (AIV) subtypes are common, H8–H12, H14 and H15 are rarely detected in wild aquatic birds, while H13 and H16 viruses have been isolated mainly from gulls (Wille et al, 2011)
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