Entry of Influenza A Virus with a α2,6-Linked Sialic Acid Binding Preference Requires Host Fibronectin

Abstract

The receptor binding specificity of influenza A virus is one of the major determinants of viral tropism and host specificity. In general, avian viral hemagglutinin prefers to bind to α2,3-linked sialic acid, whereas the human viral hemagglutinin prefers to bind to α2,6-linked sialic acid. Here, we demonstrate that host fibronectin protein plays an important role in the life cycle of some influenza A viruses. Treating cells with anti-fibronectin antibodies or fibronectin-specific small interfering RNA can inhibit the virus replication of human H1N1 influenza A viruses. Strikingly, these inhibitory effects cannot be observed in cells infected with H5N1 viruses. By using reverse genetics techniques, we observed that the receptor binding specificity, but not the origin of the hemagglutinin subtype, is responsible for this differential inhibitory effect. Changing the binding preference of hemagglutinin from α2,6-linked sialic acid to α2,3-linked sialic acid can make the virus resistant to the anti-fibronectin antibody treatment and vice versa. Our further characterizations indicate that anti-fibronectin antibody acts on the early phase of viral replication cycle, but it has no effect on the initial binding of influenza A virus to cell surface. Our subsequent investigations further show that anti-fibronectin antibody can block the postattachment entry of influenza virus. Overall, these results indicate that the sialic acid binding preference of influenza viral hemagglutinin can modulate the preferences of viral entry pathways, suggesting that there are subtle differences between the virus entries of human and avian influenza viruses.

Glycosylation changes in the globular head of H3N2 influenza hemagglutinin modulate receptor binding without affecting virus virulence

“…While some studies have found a correlation between receptor binding and IAV virulence18212226, there is growing evidence that the HA binding to SA-containing receptors does not always correlate with infection in itself373839404142. Consistent with the latter and our previous observation that variations in SA binding by H3N2 IAVs isolated from 1968 to 2012 does not correlate with disease severity or spread13, modulation in receptor binding of rgHK68 viruses had no effect on such viral characteristics as elution from turkey RBC, growth in epithelial cell cultures, cytopathology, or virulence in mice.…”

“…Consistent with the latter and our previous observation that variations in SA binding by H3N2 IAVs isolated from 1968 to 2012 does not correlate with disease severity or spread13, modulation in receptor binding of rgHK68 viruses had no effect on such viral characteristics as elution from turkey RBC, growth in epithelial cell cultures, cytopathology, or virulence in mice. One possible explanation for this may be a role for post-attachment factors373839404142. Another possibility is that H3N2 binding and entry is mainly dependent on only a limited subset of sialylated glycans, and that binding to these biologically critical ligands has remained relatively constant over time.…”

Highly Pathogenic H5N1 and Novel H7N9 Influenza A Viruses Induce More Profound Proteomic Host Responses than Seasonal and Pandemic H1N1 Strains

“…The importance of fibronectin in influenza virus infection was demonstrated in a study by Leung et al 52 . It was identified as a key entry factor specifically required for viruses with a tropism for glycoproteins with α(2,6)-linked sialic acid (SA) moieties.…”

Sialic acid-dependent interactions between influenza viruses and Streptococcus suis affect the infection of porcine tracheal cells

“…4). The human influenza virus strain WSN, which recognizes a2,6-linked sialic acid (Leung et al, 2012), was also inhibited by Streptococcus suis wt. By contrast, the mouse-adapted H1N1 virus PR8, which recognizes a2,3-linked sialic acid (Koerner et al, 2012; Tate et al, 2011), was not inhibited in its HA activity by Streptococcus suis wt (Fig.…”