Seasonal influenza vaccines
Hopefully, all students enrolled in BIO230 have gotten their annual seasonal flu vaccine. As of January 15th, influenza incidence was reported as “widespread” in 17 states, including Pennsylvania by the Centers for Disease Control in Atlanta, and we have several more weeks of flu season to go before numbers of cases begin to significantly decline. As you likely know, influenza vaccines are typically only good for each year’s influenza outbreak, which is why a new vaccine is necessary each year. The reason that influenza vaccines are only effective against a single season’s outbreak is because the strain of virus is somewhat different from year to year, due to the inherent variability of the virus. Since vaccines are only effective against that year’s strain of virus, and because of the fact that varieties of influenza virus can infect and propagate in a wide variety of mammals and birds, it is unlikely that influenza will ever be a disease that can be eradicated, in the manner that smallpox has been. Which brings me to a fascinating science article that I found via the American Society of Microbiology news website. Researchers at Emory University and the University of Chicago examined the response of patients who had been infected with the H1N1 strain of flu during the 2009 flu season. Nine patients who were sick with this strain of flu were studied for their ability to make immune molecules called antibodies, which are the proteins that help to protect us from infectious diseases via a number of mechanisms. Antibodies are powerful mediators of immunity, but they are also incredibly specific: an antibody which is effective against one influenza virus will not recognize other varieties of influenza virus. This is why we must get a new influenza vaccine each year, as the antibodies we make when we get a flu shot will not be effective against next year’s flu.
This is where the story gets interesting. When the researchers examined the antibodies made by these patients against the H1N1 variety of influenza virus, they found several of the antibody types recognized other varieties of influenza virus in a process called “cross-reactivity.” Through very sensitive techniques, the researchers eliminated the possibility that the patients had been infected with one of these other flu types, and that the antibodies being made were in fact due to infection with H1N1. To verify the usefulness of these H1N1 antibodies, researchers put the antibodies into mice, which were then infected with influenza. Mice receiving the antibodies were protected from the effects of the virus.
What is the next step? This isn’t necessarily a novel finding; antibodies which cross-react with different influenza strains have been described before, but not to the same sort of detail as this study does. The studies will likely continue to be confirmed, and the protective nature of the immune response studies in mice and other animal models of influenza infection. At that point, the parts of the virus that induce the production of the protective antibodies seen in this study can be incorporated into the seasonal flu vaccine. This in turn can hopefully lead to the development of a flu vaccine that lasts more than one year, and offers more effective way of protecting the population from this deadly disease.