Seasonal flu vaccines mainly target an influenza surface protein called hemagglutinin (HA). But new research from National Institute of Health (NIH) studies suggest that it might be better to target a surface protein called neuraminidase (NA) for broader protection.
Researchers analyzed blood samples from people vaccinated against influenza and people who were diagnosed with the 2009 H1N1 virus or H3N2 viruses. The analyses indicated that influenza vaccines rarely induce NA-reactive antibodies, whereas natural influenza infection induces these types of antibodies at least as often as it induces HA-reactive antibodies, the researchers say.
Additional laboratory experiments showed the NA-reactive antibodies induced during natural flu infection were “broadly reactive,” meaning they could potentially protect against diverse strains. To test that theory, the researchers isolated NA-reactive monoclonal antibodies from the patients with H3N2 and H1N1, then administered 13 N2-reactive antibodies to mice and infected the mice with a different H3N2 virus strain. Eleven of the N2-reactive antibodies partially or fully protected the mice. In a similar test of N1-reactive antibodies versus H1N1 virus and H5N1-like virus, 4 of 8 antibodies completely protected against both strains.