Each year, researchers select three influenza strains to include in the seasonal flu vaccine. Because there are so many different strains of the influenza virus, and because it mutates so rapidly, this selection is always a guess—a highly educated one based on global surveillance data, but still a guess.
In some years, the selections turn out to be remarkably accurate. During the 2010-2011 flu season, for example, the three strains selected for the seasonal flu vaccine were a very good match to strains circulating in the wild. In other years, however, researchers haven’t been so lucky. And since immunity to one strain of the flu doesn’t necessarily provide protection against other strains, a poor match between the vaccine strains and the circulating ones may mean an ineffective flu vaccine.
Researchers have long hoped to develop a so-called “universal” flu vaccine: one that could provide protection against all, or at least most, of the many strains of influenza capable of making people sick. If such a vaccine could be developed, the need for a new seasonal shot every year could be a thing of the past.
Unfortunately, past research has lacked good targets for such a vaccine. There are few parts of the virus that are “conserved” among strains – that is, the same or similar among different strains, and likely to remain that way even if the virus mutates. Without such a target being present in each strain for a vaccine to “aim” at, it’s difficult to provide protection against the different strains.
Recently, researchers from The Scripps Research Institute and pharmaceutical firm Crucell discovered an antibody (called CR8020) that “recognizes” a unique conserved piece of the influenza virus. In tests, the antibody provided broad protection against multiple influenza A strains in mice. Previously, in February 2009, the same group had reported on a group of antibodies that provided protection against a different group of influenza A viruses.
The researchers now suggest that the previously discovered and newly documented antibodies, used in combination, could provide broad protection against nearly all disease-causing influenza A subtypes. (Influenza A viruses, named based on two viral proteins, hemagglutinin and neuraminidase, are those of the type “HxNy.” For example, the H1N1 “swine flu” is an influenza A virus.)
While it’s still too early to tell whether this approach will be effective in humans, the researchers note that a successful antibody-based treatment based on this research would provide particular benefits for those at high risk from influenza, including people with immune system deficiencies. In the meantime, studying the targets of the antibodies—the parts of the virus that are conserved across strains—may provide another avenue of research toward a universal influenza vaccine.
Ekiert D, Friesen R, Bhabba G et al. A Highly Conserved Neutralizing Epitope on Group 2 Influenza A Viruses. Science. 7 July 2011: 1204839Published online 7 July 2011. Available at: http://www.sciencemag.org/content/early/2011/07/06/science.1204839
Ekiert D, Bhabba G, Elsliger M et al. Antibody Recognition of a Highly Conserved Influenza Virus Epitope. Science. 10 April 2009: 324 (5924), 246-251. Published online 26 February 2009. Available at: http://www.sciencemag.org/content/324/5924/246.abstract