Universal flu care.

Designing the annual flu vaccine is not unlike playing the stock market. Each year the World Health Organization (WHO) creates a portfolio of three strains of flu, each representing a different influenza virus. This portfolio is the trivalent inactive vaccine, the official name for your annual flu shot. The strains that are selected are predicted to be the predominant source of flu infection in the upcoming season. Inactive forms of the viruses are combined into one shot, which gives your immune system a preview of what it can expect to fight in the upcoming months. Your body produces antibodies to those strains in advance so that it is ready to attack when flu season begins.

Year after year the scientists at WHO have much success in predicting the most harmful strains of flu; however, their selection process is by no means infallible. While the scientists have plenty of data to draw upon, the decision is, at best, an educated guess. There is no way to know for sure which strains present the greatest risk, and those strains that don’t make it into the vaccine can still infect you and make you sick. Moreover, foresight is greatly limited by the speed with which the viruses evolve. Flu viruses mutate so rapidly that vaccines lose their effectiveness every year. Even after your body builds a supply of antibodies to a particular flu strain, it will be unable to recognize the same strain the following year.

A virus is a very simple entity consisting of a piece of DNA contained within a protein case. Antibodies can only recognize one specific site on the protein case, which they attach to, signaling white blood cells to attack. Usually the antibodies that develop in response to the annual flu vaccine target a highly variable site on the head of the protein case, meaning that a different antibody is needed for each strain of the virus every year. During the 2009 H1N1 pandemic, however, vaccinated patients produced a different kind of antibody. These bound to a region of the protein that is conserved among all Influenza A subtypes, including seasonal flu, avian flu, and swine flu. Additionally, the high degree of conservation among flu viruses suggests that this site on the protein may not mutate from year to year.

Of course the antibody itself cannot be a vaccine, but it will inform the design of a future universal flu vaccine. Now knowing the best region to target, scientists will be able to develop a vaccine that triggers your immune system to produce the antibodies to latch onto the same, conserved site, regardless of the year or strain. Such a vaccine will eliminate the annual guesswork and protect against unexpected strains. You can learn more about this stunning development in immunology as it was published in Science as well as additional reports in Nature News.