Influenza vaccines typically coax the immune system to generate antibodies that recognize the head of hemagglutinin (HA), a protein that extends outward from the surface of the flu virus. The head is the most accessible regions of HA, making it a good target for the immune system; unfortunately, it is also one of the most variable. From year to year, the head of HA often mutates, necessitating new vaccines.
A team led by scientists at Weill Cornell Medicine, Scripps Research and the University of Chicago has identified an important site of vulnerability on influenza viruses—a site that future influenza vaccines and antibody therapies should be able to target to prevent or treat infections by a broad set of influenza strains. The scientists found that a small subset of antibodies elicited by experimental and existing influenza vaccines target a site at the base, or anchor, of the influenza virus HA protein—an “epitope” whose significance was not recognized in prior influenza antibody studies. Experiments in cell cultures and in mice suggested that antibodies against this “anchor epitope” can neutralize a broad set of influenza strains, including strains with pandemic potential.
“It’s always very exciting to discover a new site of vulnerability on a virus because it paves the way for rational vaccine design,” says co-senior author Andrew Ward, PhD, professor of Integrative Structural and Computational Biology at Scripps Research. “It also demonstrates that despite all the years and effort of influenza vaccine research there are still new things to discover.” The study was published in the journal Nature; Broadly neutralizing antibodies target a hemagglutinin anchor epitope.