Host versus flu: antibodies win a round?

Abstract

Structural and functional analyses of three neutralizing antibodies against influenza virus H2 HA may explain why this HA subtype has disappeared from circulation in the human population and point to a potential new avenue for antiflu therapeutics.

Figure 1

Immune responses induced by influenza A virus. (a) Timeline of influenza A HA subtypes in human circulation since 1918. (b) Primary antibody response against H1- or H3-subtype viruses is primarily targeted to the hypervariable regions in the globular head (residues marked in blue), with very little targeted to the receptor-binding site (residues in red). This antibody repertoire has minimal activity during subsequent infection with a virus in which the hypervariable regions have drifted (from blue to green). In contrast, a greater share of the antibody response to H2-subtype viruses appears to be targeted toward the receptor-binding site, thus a greater degree of cross-reactivity is seen with drifted viruses.