Many of us anticipate, with some trepidation, the yearly ritual of getting a flu shot to protect against the newest influenza strains.
Sometimes, the stakes are pretty high. Last year, the H1N1 virus raised the specter of a virulent plague that might cause widespread death. Fortunately, that didn't materialize, but the many months required to make a vaccine to protect against a new virus strain could portend a future outbreak with a more frightening outcome.
These are the twin problems- new influenza viruses evolve at a high rate, and old vaccines frequently don't protect against the new flu strains. Sometimes scientists and physicians aren't able to accurately predict the strains of flu virus that will cause disease in a particular season and, consequently, even the current vaccine doesn't work very well. This was the case, for example, for the vaccine developed for the 2007-2008 flu season. It would be ideal if a vaccine could protect against a variety of influenza viruses, and new research provides some hope that such a vaccine might be in the offing. Researchers at the National Institutes of Health and the Centers for Disease Control and Prevention tested a new strategy for vaccination in mice, ferrets, and monkeys. They used a two-step process. The first step was injection of DNA containing a gene from the influenza virus. The second step was an additional vaccination, using a traditional flu vaccine.
To allow a comparison, mice were treated in one of five different ways. Some mice were unvaccinated, some were vaccinated with DNA only, some were vaccinated with the vaccine used in 2006-2007 only, some were vaccinated against a strain of flu virus that circulated in 1934, and some were vaccinated with both DNA and the 2006-2007 vaccine.
Following treatment, mice were infected with a normally lethal dose of the influenza virus from 1934. All the mice vaccinated against the 1934 virus survived; more than 80 percent of mice who received both the DNA and the 2006-2007 vaccine survived; all the other mice died. A similar test was done with ferrets, with the measure of vaccine effectiveness being weight loss. The ferrets vaccinated with the 1934 vaccine, and with the DNA and 2006-2007 vaccination had the least weight loss; the other ferrets suffered more dramatic weight loss, a sign of more serious disease.
In addition, the researchers took blood from the vaccinated mice, ferrets and monkeys. They found that animals vaccinated with both DNA and the 2006-2007 vaccine were immune to a wide range of viruses from 1934, 1986, 1995, 1999, 2006, and 2007. In contrast, animals vaccinated with just DNA, or just the 2006-2007 vaccine were immune to a smaller range of viruses.
This work is a starting point, and some additional modifications may further improve the efficacy of this vaccination strategy for influenza. If so, a few years from now a flu shot may needed only once a decade.
This article was based on a report in Science by Wei, Boyington, and others entitled "Induction of broadly neutralizing H1N1 influenza antibodies by vaccination." Vol. 329:1060-1064, August, 2010, and a review by Robert Dome "Prime, Boost, and Broaden" Science Vol. 329:102-103, August 2010.
Patrick Guilfoile has a Ph.D. in bacteriology and is currently an interim associate vice president at Bemidji State University.